MS1003SHMS1004SH Application Note Ver.2.2 The product and product specifications are subject to change without notice. SHINDENGEN ELECTRIC MFG. CO. , LTD 1/41 MS1003SHMS1004SH Application Note Ver.2.2 Precautions Thank you for purchasing this product. To ensure safety, keep the following warnings and cautions in mind at all times when using this IC. Warning ! Improper handling may result in death, serious injury, or significant property damage. Caution ! Improper handling may result in minor injuries or minor damage to property. ! ! While we strive to improve quality and reliability at all times, semiconductor products will malfunction at a certain rate. To prevent or limit the scope of injury, fire, or other societal damage that may result from product malfunctions, it is your responsibility to take steps to ensure that your designs incorporate suitable safety factors, including appropriate redundancy, fire prevention, and false operation prevention measures. The semiconductor product described in this document is not designed or manufactured for use in devices or systems in which malfunctions would threaten human life or result in injury. Nor is it designed or manufactured for use in other devices or systems requiring mission-critical quality and reliability. Please consult with us before using the product in any of the following special or specific applications: Warning Special applications Transport equipment (e.g., automobiles and ships), communications equipment for backbone networks, traffic signal equipment, disaster or crime prevention equipment, medical devices, various types of safety equipment Specific applications Nuclear power control systems, aircraft equipment, aerospace equipment, submarine repeaters, life-support medical equipment Please consult with us before using any IC products in equipment expected to run continuously for extended periods, even if the application in question has no special requirements. Caution ! Never repair or modify the product. Doing so may result in serious accidents. <<Electric shock, destruction, fire, or malfunction may result.>> ! In the event of problems, an excessive voltage may arise at the output terminal, or the voltage may drop. Try to anticipate malfunctions and load issues and confirm that the end equipment is adequately protected (e.g., by overvoltage or overcurrent protection). ! Check the polarity of the input and output terminals. Make sure they are correctly connected before turning on power. <<The protective element may blow, or smoke or fire may result.>> ! Use the specified input voltage. Provide a protective element in the input line. <<Smoke or fire may result in event of a problem.>> In the event of a malfunction or other anomaly, turn power off immediately and contact us. ! The contents of this document are subject to change without notice due to product improvements. You must provide written agreement concerning the specifications before starting to use the device. We have made every effort to confirm that all information provided in this document is correct and reliable. However, we take no responsibility for losses or damages incurred or infringements of patents or other rights resulting from use of the information. This document neither warrants nor authorizes the right to exercise intellectual property rights or any other rights belonging to Shindengen or third parties. No part of this document may be duplicated or reproduced in any form without prior consent from Shindengen. SHINDENGEN ELECTRIC MFG. CO. , LTD 2/41 MS1003SHMS1004SH Application Note Ver.2.2 Contents ... 4 4. Pin functions ... 17 1.1 Introduction ... 4 4.1 Z/C pin ... 17 1.2 Characteristics ... 4 4.2 F/B pin ... 17 1.3 Applications ... 4 4.3 GND pin ... 17 1.4 Appearance and dimensions ... 4 4.4 OCL pin ... 17 1.5 Basic circuit configuration ... 5 4.5 VG pin ... 17 ... 6 4.6 Vcc pin ... 17 2.1 Block diagram ... 6 4.7 Vin pin ... 17 2.2 Pin names ... 6 ... 18 3. Circuit operation ... 7 5.1 Design flow chart ... 18 ... 7 5.2 Example of main transformer design conditions ... 19 3.1.1 Startup circuit ... 7 5.3 Formulas for main transformer design ... 19 3.1.2 Soft start ... 8 5.4 Checking the operating points ... 21 3.1.3 Bias assist ... 8 5.4.1 Variables in formulas ... 22 ... 9 ... 9 5.4.2 Formulas for obtaining trough skip start power ... 3.2.1 On-trigger circuit 22 3.2.2 Quasi-resonance ... 9 ... 10 ... 3.2.3 Soft drive 5.4.3 Formulas for obtaining trough skip end power 22 3.2.4 Trough skip operation ... 10 ... 11 ... 3.2.5 Output voltage control 5.4.4 Formulas for obtaining auto burst start/end power 24 3.3 Burst mode oscillation ... 11 ... 11 ... 3.3.1 AutoStby function 5.4.5 Formulas for obtaining droop point power 24 3.3.2 Super standby mode ... 13 ... 27 3.4 Protection functions ... 14 5.5.1 Design procedure for the Z/C pin (Pin 1) ... 27 3.4.1 Vcc overvoltage protection latch ... 14 5.5.2 Design procedure for F/B pin ... 29 3.4.2 Overcurrent protection ... 14 5.5.3 Design of OCL pin ... 30 3.4.3 Overload protection (timer latch function) ... 15 5.5.4 Design of VG pin ... 31 3.4.4 VCC-GND short circuit protection ... 16 5.5.5 Design of Vcc pin ... 32 16 5.5.6 Setting resonating capacitor ... 34 ... 35 6.1 Circuit diagram ... 35 6.2 Calculations for example circuit design ... 35 1. Overview 2. Block diagram 3.1 Startup 3.2 Oscillation 3.4.5 Leading edge blank (LEB) 3.4.6 On-trigger malfunction prevention circuit ... 16 3.4.7 TSD ... 16 5. Design procedure 5.5 Pin design 6. Example circuit diagram SHINDENGEN ELECTRIC MFG. CO. , LTD 3/41 MS1003SHMS1004SH Application Note Ver.2.2 1. Overview 1.1 Introduction We have developed the MS1003SH and MS1004SH to meet the growing demand for power conservation. These ICs incorporate a super standby mode to optimize power efficiency under micro loads. The MS1003SH and MS1004SH consume less power in standby mode than conventional ICs. The ICs incorporate various functions to make it more user-friendly and to make it easier to design a power supply with fewer external components. 1.2 Characteristics 1) Quasi-resonant design for high efficiency and low noise 2) Four-step soft start function (40 ms/step) 3) Onboard startup circuit requires no startup resistor, dramatically reducing losses in the startup circuit. 4) The automatic trough skip function controls increases in oscillation frequency and improves efficiency under light loads. 5) Auto burst function improves efficiency under light loads with no additional components. 6) Super standby mode improves efficiency under micro loads. 7) Soft drive circuit reduces noise. 8) Thermal shutdown, overvoltage protection, and overload protection (timer latch) 9) Primary current limit circuit incorporates an input voltage dependence correction circuit to reduce the number of components required. 10) Bias assist function for startup circuit 11) Vcc-GND short circuit protection function 12) SOP-8 package employed for compact dimensions 1.3 Applications Televisions, video recorders, refrigerators, washing machines, air conditioners and other appliances in which reduced standby power consumption is a design goal. Unit: mm 6.0 3.9 0.3 1.4 Appearance and dimensions SHINDENGEN ELECTRIC MFG. CO. , LTD 4/41 MS1003SHMS1004SH Application Note Ver.2.2 1.5 Basic circuit configuration (1) Circuit without super standby function (2) Circuit with super standby function SHINDENGEN ELECTRIC MFG. CO. , LTD 5/41 MS1003SHMS1004SH Application Note Ver.2.2 2. Block diagram 2.1 Block diagram TIMER_ LATCH_ STBY_ CIR TSD Z/C 1 S R S S S R V F/B OVP COMP 5 VG 4 OCL 8 Vin 6 V 3 GND 2 IDP_Limit COMP S R IDP_burst COMP VUL COMP R Stup_UVLO COMP Vcc_UVLO COMP SPSTBY UVLO COMP 2.2 Pin names Pin number 1 2 3 4 5 6 7 8 Symbol Z/C F/B GND OCL VG Vcc NC Vin Pin name Zero current detection pin Feedback signal input pin Ground pin Overcurrent limit pin VG pin Vcc pin No connection Vin pin SHINDENGEN ELECTRIC MFG. CO. , LTD 6/41 MS1003SHMS1004SH Application Note Ver.2.2 3. Circuit operation 3.1 Startup The diagram below shows the startup sequence. Vin Nc coil backup Off On Off On Off Normal mode On Off Standby mode Standby On Normal mode Vcc(start)= Vcc(stup off)=12V Vcc(stop on normal)=9V Vcc(stop normal)=8V Vcc Vcc(stup on stby)=8V Vcc(stop stby)=12V VccUVLO Startup UVLO Startup sequence 3.1.1 Startup circuit The startup circuit does not require a startup resistor, making it possible to easily start the IC with a small number of components. A schematic diagram of the startup circuit is shown to the right. Vin pin Startup circuit Until the IC starts up, the startup circuit current Icc (stup) flows from the Vin pin to the Vcc pin to charge C, as shown in the diagram. Oscillation begins when the voltage at the Vcc pin reaches Vcc (start). The startup circuit opens, and the Vcc pin startup circuit current stops. The Vcc pin has hysteresis, which begins oscillating at Vcc (start) and stops oscillating at Vcc (stop stby) or Vcc (stop normal). A bias assist function is provided for the Vcc voltage to ensure safe startup. For more information on the bias assist function, see Section 3.1.3. SHINDENGEN ELECTRIC MFG. CO. , LTD 7/41 MS1003SHMS1004SH Application Note Ver.2.2 3.1.2 Soft start At startup, the OCL level changes in four stages. Current flowing to the main switch also increases in stages. The envelope curves of the current to the main switch are shaped in four steps to avoid abrupt switch startups. The soft start time depends on the Tss1 to Tss3 settings. The time settings are determined by the IC. Normal OCL level Steady-state operation 3.1.3 Bias assist Soon after oscillation begins during startup, the voltage drops, and the oscillation may halt. To prevent this and ensure proper startup, the bias assist function supplies energy to the Vcc pin. Shown below is a schematic diagram of Vcc startup incorporating the bias assist function. Assist function activates. If the voltage drops below the oscillation stop voltage, oscillation halts, and the startup circuit must restart. The voltage remains above the oscillation stop voltage to ensure that oscillation does not halt. SHINDENGEN ELECTRIC MFG. CO. , LTD 8/41 MS1003SHMS1004SH Application Note Ver.2.2 3.2 Oscillation Approx. 3.2.1 On-trigger circuit As shown to the right, when a negative edge of the Z/C pin voltage reaches VZ/C (0.25 V), the gate signal is output, and the main switching device is turned on. Current-critical operations are performed by detecting energy discharge timing with the control coil voltage before turning on the main switching device. To minimize noise, negative edge detection detects a trigger while the Z/C pin voltage falls from Hi to Low. The VZ/C voltage (0.25V) incorporates 50 mV hysteresis for improved noise resistance. 0.25V 0.25 V VZ/C ID Secondary rectification diode current 2 VDS Control coil voltage 3.2.2 Quasi-resonance In a circuit having resonating capacitor Cq between the drain and the source of the main switching device, as shown to the right, when the secondary diode current reaches 0 A, damping begins at the resonance frequency based on the primary inductance LP of the main transformer and the resonating capacitor. Adjusting the time constant of the CR connected to the Z/C pin as shown on the right allows the main switching device to be turned on at a trough of the damping voltage waveform, thereby reducing turn-on losses. LP 8 Cq Vin pin Vin 1 5 Z/C pin Z/C R 3 GND pin GND C The time constant determines on-timing. ON SHINDENGEN ELECTRIC MFG. CO. , LTD 9/41 MS1003SHMS1004SH Application Note Ver.2.2 3.2.3 Soft drive Gate voltage supply The soft drive circuit supplies a trigger voltage slightly greater than the gate threshold of the main switch as a gate drive voltage before constant voltage driving begins. This prevents the supply of greater gate voltage than necessary. matched to drain current VGS The soft drive reduces losses by the gate charge voltage and reduces noise by controlling the resonating capacitor discharge peak current. Reducing gate charge spikes IG Reducing reactive charge under light loads Damping of resonating capacitor discharge current ID 3.2.4 Trough skip operation The MS1003SH and MS1004SH monitor the switching cycle. If the switching cycle length becomes shorter than the trough skip start cycle T (bottom skip start) of 7.5 s (TYP), the IC enter the following modes: MS1003SH moves from the normal partial resonance mode to the 1 trough skip mode (switching on at the second trough). MS1004SH moves from the normal partial resonance mode to the 2 trough skip mode (switching on at the third trough). In trough skip mode, the MS1003SH extends the off-period by a cycle of resonance and the MS1004SH by two cycles of resonance. This controls an increase in the frequency. Once in trough skip mode, the cycle monitoring timer setting changes. When the time from switching on to the first voltage trough becomes longer than T (bottom skip stop) of 13 s (TYP), the IC returns to normal partial resonance mode. Using hysteresis in this manner prevents jitter and acoustic noise. VDS ID Operating mode Partial resonance Trough skip Partial resonance OFF range monitoring timer T(bottom skip start) T(bottom skip stop) T(bottom skip start) Sequence of MS1003SH SHINDENGEN ELECTRIC MFG. CO. , LTD 10/41 MS1003SHMS1004SH Application Note Ver.2.2 3.2.5 Output voltage control The MS1003SH and MS1004SH control the output voltage with the ON range proportional to the voltage at the F/B pin. The latch count start voltage (VF/B (latch count)) is set up for the F/B pin. When the voltage exceeds the set level, the timer begins counting. After maintaining this state for approximately 2 s (latch count), the IC is latched. ON rangetton [s] ons The output voltage is controlled linearly so that the ON range is at its minimum when the F/B pin voltage is 1.5 V and at its maximum when the voltage is 4.5 V. The IF/B current flows from the F/B pin. The impedance of the photocoupler transistor externally connected between the F/B pin and the GND pin is varied by a control signal from the secondary output detection circuit, thereby controlling the ON range of the main switching device to produce a constant voltage. Controlling output voltage with photocoupler F/B pin Output voltage error detection feedback signal ton (max) 0 1.5 4.5 VF/B(latch count) Feedback voltage VF/BV 3.3 Burst mode oscillation 3.3.1 AutoStby function The MS1003SH and MS1004SH switch between normal mode and burst mode automatically. This enables low standby power consumption with no other components required for standby mode. 1) Switching from normal mode to burst mode The IC switches from normal mode to burst mode when the load becomes lighter and the OCL pin detects a drain current at the VOCL (stby) = 45 mV (TYP) or less for longer than Tstby = 250 ms (TYP). VOCL (stby) = 45 mV or less Operating mode The IC enters standby mode when the drain current stays at the burst switching current or below for longer than Tstby = 250 ms. Normal Burst SHINDENGEN ELECTRIC MFG. CO. , LTD 11/41 MS1003SHMS1004SH Application Note Ver.2.2 2) Burst mode control In burst mode, the OCL pin detects the drain current, and every pulse is limited to VTH (stby) = 60 mV (TYP) to control oscillation. Output voltage is controlled linearly in normal mode. In burst mode, oscillation begins when the F/B pin voltage VF/B reaches the VF/B (stby start) = 1.8 V (TYP) and stops when the voltage falls to the VF/B (stby stop) = 0.8 V (TYP). This control causes voltage ripples and intermittent oscillation, reducing switching loss per unit time and thereby reducing standby power consumption. The following thresholds also change from normal mode: The thresholds for oscillation stop voltage and the startup circuit on voltage are reduced by 1 V from normal mode. VCC (stop normal) = 8 V (TYP) VCC (stop stby) = 7 V (TYP) VCC (startup on normal) = 9 V (TYP) VCC (startup on stby) = 8 V (TYP) These allow easy adjustment of the Vcc setting in standby mode and further reduce power consumption. 3) Switching from burst mode to normal mode The IC switches automatically to normal mode when the load becomes heavier and the VF/B voltage rises and exceeds VF/B (stby reset) = 3V (TYP). The thresholds changed at standby return to previous levels when the IC returns from burst mode to normal mode. At the same time, soft start activates for approximately 1/70 of the normal startup to prevent jitter and other problems during mode switching. Soft start for approx. 1/70 of normal startup Operating mode Burst Normal SHINDENGEN ELECTRIC MFG. CO. , LTD 12/41 MS1003SHMS1004SH Application Note Ver.2.2 3.3.2 Super standby mode Super standby mode is an intermittent oscillation mode that minimizes power losses under micro loads. The function helps reduce input power. 1) Switching from normal mode or auto burst mode to super standby mode The IC switches from normal mode or auto burst mode to super standby mode by stopping the external clamp of the Z/C pin voltage using a signal and by applying 3 V or more per cycle. In super standby mode, the IC promptly lowers the Vcc voltage to VCC (sp stby start) to shift seamlessly from direct control to indirect control. Standby signal ON (Photocoupler lights up): 6 VCC VCC pin Z/C pin 1 Z/C Z/C pin voltage clamp Normal mode or auto burst mode GND pin GND 3 Standby signal OFF (Photocoupler goes out): Z/C pin voltage clamp released Super standby mode Standby signal (external signal) 2) Super standby control In super standby mode, control shifts from direct control using the F/B pin to indirect control using the Vcc pin. Super standby oscillation start VCC voltage: VCC (sp stby start) = 8.7 V (TYP) Super standby oscillation stop VCC voltage: VCC (sp stby stop) = 9.3 V (TYP) Control is implemented with a lower voltage than VCC during normal operations. Output voltage is kept below regulation voltage, thereby bypassing activation of the feedback photocoupler and reducing power consumption. 3V Z/C Super standby start Super standby stop ID Super standby Normal Vcc(sp stby stop)=9.3V Vcc(sp stby start)=8.7V Super standby Normal Indirect control with Vcc Vcc VCC Vout SHINDENGEN ELECTRIC MFG. CO. , LTD 13/41 MS1003SHMS1004SH Application Note Ver.2.2 3) Switching from super standby mode to normal mode The IC exits super standby mode by clamping the Z/C pin voltage at 3 V or less using an external signal. 3.4 Protection functions 3.4.1 Vcc overvoltage protection latch The MS1003SH and MS1004SH incorporate an overvoltage protection circuit (OVP). The IC is latched when the control coil voltage exceeds the VOVP to provide indirect overvoltage protection for the secondary output. The IC is unlatched by momentarily dropping the VCC pin voltage to the VUL (unlatch voltage) or below. Vin Nc coil Nc backup OFF ON ON OFF Deliberately increasing Vcc voltage (e.g., output VCC detection open) VOVP=26V Vcc(start)=12V Vcc(stop on stby) or Vcc(stop on normal) VUL=3.2V Vcc VccUVLO Startup UVLO UVLO Latched Latch Unlatched Unlatched VULVUL signal 3.4.2 Overcurrent protection NP A current detection resistor is connected between the OCL pin and the GND pin to detect the source current of the main switching device. The main switching device current is limited by pulse-by-pulse operation using a threshold voltage that varies with ON range. 8 Vin pin Vin 5 Current detection resistor OCL pin OCL 4 3 GND pin GND SHINDENGEN ELECTRIC MFG. CO. , LTD 14/41 MS1003SHMS1004SH Application Note Ver.2.2 Output voltage VoVo This current limit protection function incorporates a function to correct dependence on input voltage. The function changes the OCL threshold on the IC from the VTH (OCL start) of approximately 0.35 V to the VTH (OCL) clamp of approximately 0.55 V linearly with time. Since the slope (di/dt) of the drain current of the main switching device is proportional to the input voltage, when the input voltage increases, the current reaches the OCL threshold with smaller IDP, and the droop is corrected. VGS VTH(OCL)clamp VTH(OCL start) VOCL level Vin Vin Large Output current Io Io TOCL Large Small Small 3.4.3 Overload protection (timer latch function) If the load exceeds the VTH (OCL) droop VTH(OCL) power limit, the output voltage falls; after Tlatch count = 2 s (TYP) has elapsed, the IC is latched. Tlatch count=2(TYP) The power limit for protection is activated if power exceeds the droop power set as the overcurrent limit VTH (OCL), and the output voltage begins to fall. The feedback voltage increases beyond the control limit, and the VF/B voltage increases to the VF/B (latch count) = 4.6 V or more. The timer detects this voltage and begins counting. When the increase in voltage is detected continuously for Tlatch count = 2 seconds, the IC is latched to prevent a persisting overload. The timer is set for 2 seconds to avoid false detection. Output voltage Vo (V) Vo(V) The overload timer latch function is a protection function that latches the IC when the F/B pin voltage stays at the VF/B (latch count) = 4.6 V or more for more than Tlatch count = 2 seconds. 0 Latched Output current Io (A) Io(A) The timer is reset if the F/B pin voltage drops below the VF/B (latch count) = 4.6 V or if the VCC voltage drops below the VUL as the timer counts. After the IC is latched, the bias assist function of the startup circuit turns off to reduce heat buildup in the IC. SHINDENGEN ELECTRIC MFG. CO. , LTD 15/41 MS1003SHMS1004SH Application Note Ver.2.2 Overload beyond the droop setting Output current Io Main SW device current ID The bias assist function turns off after the IC is latched. Control voltage Vcc Feedback voltage VF/B 3.4.4 VCC-GND short circuit protection If Vcc and GND short-circuit, current flows continuously to the startup circuit, and heat builds up in the IC. A function reduces Icc in the event of short circuits to prevent excessive heat buildup. 3.4.5 Leading edge blank (LEB) The MS1003SH and MS1004SH incorporate a leading edge blank function, which rejects trigger signals from the drain current detection circuit for a certain period of time after the main switching device is turned on to improve the noise margin. This function prevents false detection due to a gate drive current generated the moment the main switching device is turned on or to a current discharged from the resonating capacitor. The on-trigger is disabled during this period. 3.4.6 On-trigger malfunction prevention circuit At startup or in the event of a load short circuit, the output voltage drops to levels significantly below the set voltage. Since the control coil voltage is proportional to the output voltage, it drops significantly as well. In this case, a false on-trigger timing may be detected due to the ringing voltage while the device is off. The device may switch before the current critical point. To address this problem, the MS1003SH and MS1004SH incorporate a circuit for preventing on-trigger malfunctions at startup or in the event of short circuits. Approx. 0.25V Tondead tondead 0.25 V VZ/C ID Secondary rectification diode current 2 This function disables the on-trigger during the period Tondead after the main switching device in the IC is turned off. This prevents false detection due to the ringing voltage while the device is off. 3.4.7 TSD The MS1003SH and MS1004SH incorporate a thermal shutdown circuit. The IC is latched at 150C (TYP), and oscillation is stopped. The IC is unlatched by momentarily dropping the VCC pin voltage to the VUL (unlatch voltage) or below. SHINDENGEN ELECTRIC MFG. CO. , LTD 16/41 MS1003SHMS1004SH Application Note Ver.2.2 4. Pin functions 4.1 Z/C pin The Z/C pin detects the NC coil voltage and outputs a turn-on signal. The pin has the following functions: 1) Gate on-trigger 2) Prevention of false turn-on (Tondead) 3) Trough skip 4.2 F/B pin The F/B pin determines the ON range during constant voltage control. The pin has the following functions: 1) Determination of ON range for the F/B pin voltage (gate off-trigger) 2) Timer latch protection during no control or drooping 4.3 GND pin The GND pin is used as the ground reference of the IC. 4.4 OCL pin The OCL pin uses a detection resistor to limit the primary current. The pin has the following functions: 1) Determination of the maximum primary current peak (pulse-by-pulse) 2) Determination of the primary current peak during the four-step soft start 3) Determination of the primary current peak during the AutoStby 4) Leading edge blank function 4.5 VG pin The VG pin outputs a gate voltage and has the following functions: 1) Output of gate signal 2) Soft drive 4.6 Vcc pin The Vcc pin is the IC power terminal and has the following functions: 1) UVLO 2) OVP latch 3) Vcc assist 4) ON/OFF of the startup circuit 5) Unlatching 6) Vcc-GND short circuit protection 7) Indirect control in super standby mode 4.7 Vin pin The Vin pin is connected to the positive side of the input capacitor and is used to power on the IC. SHINDENGEN ELECTRIC MFG. CO. , LTD 17/41 MS1003SHMS1004SH Application Note Ver.2.2 5. Design procedure The design procedure presented in this section is intended to illustrate an example of electrical design procedure. Make sure insulation materials, insulation configuration, and structure meet the safety standards set forth by the relevant authorities. The following table shows the units for the parameters used in the formulas encountered in this section: List of units used in the formulas in this section Description Unit Description Unit s (second) Voltage V (volt) Time Current A (ampere) Length mm (millimeter) 2 Power W (watt) Area mm (square millimeter) Capacitance F (farad) Current density A/mm2 (ampere per square millimeter) Inductance H (henry) Magnetic flux density mT (millitesla) Resistance (ohm) Number of turns turn 5.1 Design flow chart Determine specifications. Design the main transformer. Review Check each operating point. Select the primary circuit components. [5.2 Example of main transformer design conditions] P. 19 [5.3 Formulas for main transformer design] P. 19 [5.4 Checking the operating points] P. 21 [5.5 Pin design] P. 27 Produce a prototype. Check function. Completion SHINDENGEN ELECTRIC MFG. CO. , LTD 18/41 MS1003SHMS1004SH Application Note Ver.2.2 5.2 Example of main transformer design conditions The values below are provided as guideline values only. Make the appropriate adjustments to suit specific load conditions. Description Symbol Unit Reference value VAC [V] 85-276 - 0.80-0.85 f(min) [kHz] 35-50 On duty ratio D - 0.4-0.6 Capacity of resonating capacitor Cq [pF] 100-3300 Control coil voltage VNC [V] 15-20 Magnetic flux density variation B [mT] Input voltage range Efficiency Minimum oscillation frequency Coil current density 250-300 2 [A/mm ] 4-6 * If the output capacity of the main switching device Coss is significant relative to the capacity setting of the resonating capacitor, Cq must be the capacity of the resonating capacitor plus Coss. 5.3 Formulas for main transformer design 1 Minimum DC input voltage VDC (min) 1.2 V AC (min) [V] 2 Maximum DC input voltage VDC (max) 2 VAC (max) [V] 3 Maximum oscillation cycle T(max) 4 Maximum ON period ton (max)1 5 Maximum OFF period t off (max) 6 Quasi-resonance period tq Lp Cq [s] 7 Maximum load power PO (max) Vo I O (max) [W] 8 Maximum output power (reference value) PL 1.2 PO (max) [W] 9 Main SW device peak current I DP 1 [s] f (min) D [s] f (min) N S1 VDC (min) t on (max)1 Np (VO1 VF 1 ) 2 PL VDC (min) D tq [s] [A] SHINDENGEN ELECTRIC MFG. CO. , LTD 19/41 MS1003SHMS1004SH Application Note Ver.2.2 VDC (min) t on (max)1 10 Primary coil inductance Lp 11 Number of turns in primary coil Np 12 Core gap lg [H] I DP VDC (min) t on (max)1 10 9 [Turn] B Ae 4 Ae Np 2 10 10 Lp * Ae: Sectional area of core [mm] * The gap Ig must be the center gap value. * If the Ig is 1 mm or greater, review the transformer core size and oscillation frequency and consider a redesign. Np (VO1 VF 1 ) ( Number of turns in control output coil N S1 14 Number of turns in non-control output coil N S 2 N S1 15 Number of turns in control coil Nc N S1 13 1 f (min) t on (max)1 tq ) [Turn] VDC (min) t on (max)1 VO 2 VF 2 VO1 VF 1 [Turn] VNC VFNC VO1 VF 1 [Turn] * Symbols used in formulas 13 to 15 Control output coil: Output voltage 1 VO1 Output of control output coil: Rectification diode forward voltage VF1 Non-control output Output voltage 2 VO 2 Output of non-control output coil: Rectification diode forward voltage VF 2 V NC Output of control coil: Rectification diode forward voltage VFNC coil: Control coil: Output voltage 1 * If the control coil voltage VNC is not well regulated, set a lower value. To make the most of the super standby function, set the voltage higher. 16 Primary coil sectional area 17 Secondary coil sectional area ANP 2 D Po 3 VDC (min) t on (max)1 f (min) ANS 2 Io 1 D (tq f (min) ) 3 (t off (max) tq ) f (min) [mm2] [mm2] * We recommend a wire diameter of 0.2 mm or greater for the Nc coil to simplify calculations. SHINDENGEN ELECTRIC MFG. CO. , LTD 20/41 MS1003SHMS1004SH Application Note Ver.2.2 5.4 Checking the operating points The MS1003SH and MS1004SH have points of change at which the oscillation frequency changes according to the functions of the control IC. Identifying each point helps predict the behavior of a prototype power supply. The following chart shows a model of operating frequency characteristics relative to output power. Knowing each operating point will provide approximate levels of the power, hysteresis width and droop point at these points of change. MS1003SH and MS1004SH operating frequency characteristic model Operating frequency [kHz] [kHz] Auto burst start point Auto burst end point Trough skip start point Auto burst hysteresis Trough skip end point Trough skip hysteresis Droop point Output power [W] The operating points to be calculated in this section are circled on the chart above. Trough skip start and end points Auto burst start and end points Droop point Obtain these points to check the following: Is the standby operation properly performed in standby mode? Is the trough skip hysteresis sufficient? Is the droop point sufficiently greater than the output? SHINDENGEN ELECTRIC MFG. CO. , LTD 21/41 MS1003SHMS1004SH Application Note Ver.2.2 5.4.1 Variables in formulas Description Symbol Unit DC input voltage setting VDC [V] ON range under each condition ton [s] OFF range under each condition toff [s] Main SW device peak current under each condition IDP [A] Output power under each condition Po [W] Primary current detection resistance R(ocl) [] OCL pin auto burst threshold voltage Vburst [V] OCL pin current detection threshold voltage Vth(ocl) [V] Operating cycle OFF range ON range Skipping 1 1 trough The diagram to the right shows switching waveform models, including numbers of troughs to skip and tq. For other symbols, see Section 5.3 and the specification. tq Skipping no trough 0 Skipping no trough 0 Skipping 1 1 trough Skipping 2 2 troughs Switching waveform model 5.4.2 Formulas for obtaining trough skip start power Np (T(bottom_sk ip_start) tq ) (VO1 V F 1 ) 18 ON range ton 19 OFF range toff T(bottom_sk ip_start) ton 20 Main SW device peak current I DP Trough skip start power V DC ton 2 Po 2 Lp T(bottom_skip_start) N S 1 V DC Np (VO1 V F 1 ) V DC ton Lp [s] [s] [A] 2 21 [W] If the trough skip start power obtained by the formulas above is greater than the trough skip end power obtained in Section 5.4.3, the hysteresis is insufficient; redesign the transformer. 5.4.3 Formulas for obtaining trough skip end power The trough skip function ends when either Condition 1 or Condition 2 is met. The trough skip end power will be the "trough skip end power 1 of the formula 25 of Condition 1" or the "trough skip end power 2 of the formula 30 or the trough skip end power 3 of the formula 34 of Condition 2," whichever is smaller. (Depending on the input voltage you want to calculate, compare either the trough skip end power 2 or 3 of Condition 2 to trough skip end power 1.) The chart below shows model curves of trough skip start and end power levels relative to input voltage. SHINDENGEN ELECTRIC MFG. CO. , LTD 22/41 Trough skip start/end power [W] MS1003SHMS1004SH Application Note Ver.2.2 Calculation line of trough skip end power condition 1 Calculation line of trough skip end power condition 2 Trough skip hysteresis with input voltage of VDC (clamp) or above Calculation line of trough skip start power Trough skip hysteresis with input voltage of VDC (clamp) or below Input voltage VDC [V] [Condition 1] The operating frequency fulfills T (bottom_skip_stop). * In place of coefficient A in the formulas, substitute 1 for the MS1003SH and 2 for the MS1004SH. Np (T(bottom_sk ip_stop) tq ) (VO1 V F 1 ) 22 ON range ton 23 OFF range toff T(bottom_sk ip_stop) 2 A tq ton 24 Main SW device peak current I DP Trough skip end power 1 V DC ton 2 Po 2 Lp (T(bottom_skip_stop) 2 A tq) N S 1 V DC Np (VO1 V F 1 ) V DC ton Lp [s] [s] [A] 2 25 [W] [Condition 2] The OCL pin voltage reaches the current detection threshold voltage in trough skip mode. Under this condition, Vth (ocl) varies with input voltage. First, calculate the input voltage V DC (clamp) at the point of change in Vth (ocl). If VDC does not exceed VDC (clamp), apply the formulas in 1). If VDC exceeds VDC (clamp), apply the formulas in 2). The input voltage at the point of change in Vth (ocl) is obtained with the following formula. 26 Input voltage at the point of change in Vth (ocl) V DC ( clamp ) Lp Vth(OCL ) clamp TOCL R(OCL ) [V] SHINDENGEN ELECTRIC MFG. CO. , LTD 23/41 MS1003SHMS1004SH Application Note Ver.2.2 1) VDC < VDC (clamp) * In place of the coefficient A in the formulas, substitute 1 for the MS1003SH and 2 for the MS1004SH. Lp Vth(OCL ) clamp 27 ON range ton 28 OFF range toff 29 Main SW device peak current I DP 30 Trough skip end power 2 Po [s] V DC R( OCL ) VDC N S1 ton (2 A 1) tq Np (VO1 VF 1 ) Vth(OCL ) clamp [s] [A] R(OCL ) V DC Vth( OCL ) clamp ton [W] 2 R( OCL ) (ton toff ) 2) VDC > VDC (clamp) * In place of the coefficient A in the formulas, substitute 1 for the MS1003SH and 2 for the MS1004SH. ton 31 ON range VDC R(OCL ) Lp Vth(OCLstart ) (Vth( OCL ) clamp Vth(OCLstart ) ) [s] T( ocl ) 32 OFF range toff VDC N S1 ton (2 A 1) tq Np (VO1 VF 1 ) 33 Main SW device peak current I DP V DC ton Lp Trough skip end power 3 V DC ton 2 Po 2 Lp (ton toff ) [s] [A] 2 34 [W] 5.4.4 Formulas for obtaining auto burst start/end power For Vburst in the formulas, substitute the VOCL (stby) or VTH (stby) indicated under "Automatic standby" of "Electric/thermal characteristics" in the specification. To obtain auto burst start power, substitute VOCL (stby) = 0.045 V in place of Vburst. To obtain the auto burst end power, substitute VTH (stby) = 0.060 V in place of Vburst. SHINDENGEN ELECTRIC MFG. CO. , LTD 24/41 MS1003SHMS1004SH Application Note Ver.2.2 * In place of the coefficient A in the formulas, substitute 1 for the MS1003SH and 2 for the MS1004SH. Lp Vburst VDC R(OCL ) 35 ON range ton 36 OFF range toff VDC N S1 ton (2 A 1) tq Np (VO1 VF 1 ) 37 Main SW device peak current I DP Vburst R(OCL ) [A] 38 Auto burst start/end power Po VDC Vburst ton 2 R(OCL ) (ton toff ) [W] [s] [s] 5.4.5 Formulas for obtaining droop point power Vth (ocl) varies with input voltage. First, calculate the input voltage VDC (clamp) at the point of change in Vth (ocl). If VDC does not exceed VDC (clamp), apply the formulas in 1). If VDC exceeds VDC (clamp), apply the formulas in 2). Just as in Section 5.4.3, use the following formula to obtain the input voltage at the point of change in Vth (ocl). 26 Input voltage at the point of change in Vth (ocl) V DC ( clamp ) Lp Vth(OCL ) clamp TOCL R(OCL ) [V] Droop point power PL [W] The chart below shows a model curve of the relationship between input voltage and droop point power. Calculated droop point power determined by OCL resistance Calculated droop point power corrected by the OCL correction function OCL correction starts at this point. Input voltage VDC [V] SHINDENGEN ELECTRIC MFG. CO. , LTD 25/41 MS1003SHMS1004SH Application Note Ver.2.2 1) VDC < VDC (clamp) Lp Vth(OCL ) clamp 39 ON range ton 40 OFF range toff 41 Main SW device peak current I DP Droop point power VDC ton 2 PL 2 Lp (ton toff ) [s] V DC R( OCL ) VDC N S 1 ton tq Np (VO1 VF 1 ) [s] Vth(OCL ) clamp [A] R(OCL ) 2 42 [W] 2) VDC > VDC (clamp) 43 ON range ton VDC R(OCL ) Lp Vth( OCLstart ) (Vth(OCL ) clamp Vth( OCLstart ) ) 44 OFF range toff VDC N S1 ton tq Np (VO1 VF 1 ) 45 Main SW device peak current I DP V DC ton Lp 46 Droop point power PL 47 Vth (ocl) at droop point Vth( ocl ) [s] TOCL [s] [A] VDC ton 2 2 Lp (ton toff ) 2 [W] (Vth( OCL ) clamp Vth( OCLstart ) ) TOCL ton Vth(OCLstart ) [V] The results of calculations for the operating points above are provided as guidelines. They may differ from actual power supply characteristics for various reasons, including power supply efficiency, filter circuit, and control IC signal delays. SHINDENGEN ELECTRIC MFG. CO. , LTD 26/41 MS1003SHMS1004SH Application Note Ver.2.2 5.5 Pin design 5.5.1 Design procedure for the Z/C pin (Pin 1) The operating mode switching circuit described in this section incorporates a photocoupler that receives signals from the secondary side. For the secondary circuit configuration, see 6. Example circuit diagram. (1) Basic circuit This is the simplest circuit configuration for designs requiring only normal mode. Since auto burst mode is available, it is the easiest design for a power supply featuring standby mode. (2) Circuit for using super standby mode The diagram to the right shows the basic circuit for using super standby mode. A photocoupler is added to switch the Z/C pin between high and low levels. If the photocoupler activates, the circuit operates in normal mode. If the photocoupler deactivates, the circuit operates in super standby mode. The photocoupler current must be carefully set so that the Z/C pin voltage falls sufficiently low. Protection for this circuit configuration Protect with a zener diode if the insulation appears likely to break down between the photocoupler PH102 and the primary or secondary side, as shown to the right. MS1003SH MS1004SH 3 1 R105 R106 Nc D102 DZ301 PH102 C108 (3) Circuit for operating the photocoupler at low current This circuit uses less power to operate the PH102 in auto burst mode, thereby slightly enhancing efficiency in auto burst mode compared to circuit (2). SHINDENGEN ELECTRIC MFG. CO. , LTD 27/41 MS1003SHMS1004SH Application Note Ver.2.2 (4) Setting components 1) R105 + R106 The absolute maximum rating of the Z/C pin is 5 mA. A zener diode is mounted for protection between the Z/C pin (Pin 1) and the GND pin (Pin 3). This diode determines the absolute maximum current rating. Set resistance so that the current does not exceed this level. The diagram to the right shows a model circuit, which is a basic circuit with an onboard protection element (zener diode) added. I(1) and I(2) represent currents flowing to this onboard protection element. The current I(1) flows when the Nc coil output is a positive voltage. I(2) flows when the Nc coil output is a negative voltage. Onboard protection element I(1) I(2) I(1) and I(2) must not exceed the absolute maximum rating. In ordinary designs, set resistance so that these currents do not exceed 80% of the absolute maximum rating ( 4 mA). The following table gives formulas for calculating the resistance R105 + R106: 48 Resistance assuming a positive voltage for Nc coil 49 Resistance assuming a negative voltage for Nc coil Nc (VO1 V F 1 ) VCL( H ) N S1 R105 R106 I Nc VDC (max) R105 R106 Np VCL( L) [] [] I VCL(H) and VCL(L) are the clamping voltages of the onboard protection element, a protective zener diode. The specification gives these values. If the basic circuit configuration shown in Section (1) is used, I(1) flows to the D102. In this case, formula 48 may be disregarded. 2) R106 and C108 These components set up the partial resonance period tq. Adjust to the partial resonance troughs while monitoring actual waveforms. Initial design value C108 100 pF R106 1 k or greater SHINDENGEN ELECTRIC MFG. CO. , LTD 28/41 MS1003SHMS1004SH Application Note Ver.2.2 3) D102 This diode sets the Z/C pin to low to activate normal mode. As described in Section 3.2.1, the on-trigger circuit detects the Z/C pin voltage when it reaches VZ/C (0.25 V). Thus, the diode should not reduce the voltage below VZ/C. Make sure the diode has adequate VF to secure VZ/C. 5.5.2 Design procedure for F/B pin (1) Basic circuit The diagram to the right shows the basic circuit. PH101 is a photocoupler for constant voltage control. R107 and C107 are noise reduction components. C107 has a capacitance between 470 pF and 2,200 pF. Set the initial design value to 1,000 pF. R107 is set between 39 k and 47 k. Normally, it should be set to 47 k. If the resistance falls below 39 k, the timer latch function may be disabled. (2) Protection PH101 may exhibit insulation breakdown during a short circuit test. If so, protect the circuit using a zener diode, as shown to the right. A zener diode for 10 V or greater should have negligible effect on IC functions for normal use. (3) Phase compensation of F/B pin C107 is used not just to reduce noise, but to adjust feedback response. However, in a large-capacity or multi-output power supply, phase compensation by the secondary control circuit may be inadequate. If so, add a circuit between the F/B pin and the GND pin, as shown to the right. Doing so can resolve various issues, including hunting. Refer to the following table to determine constants. Initial design value R303 4.7 k C301 0.1 F SHINDENGEN ELECTRIC MFG. CO. , LTD 29/41 MS1003SHMS1004SH Application Note Ver.2.2 (4) Additional circuit to F/B pin When adding a circuit to the power supply circuit due to load setting conditions or for other reasons, be careful to avoid disabling the timer latch function. Disabling the timer latch will affect power supply performance. 5.5.3 Design of OCL pin (1) Basic circuit The diagram to the right shows the basic circuit. The circuit consists of R104 for primary current detection and a filter circuit comprising R103 and C106. R104: Resistance required in Section 5.4 C106: Initial design value of 220 pF Design values from 220 pF to 3,300 pF R103: Initial design value of 100 Design values from 100 to 470 Increase the constants if switching noise is significant and may lead to malfunctions. (2) Protection for large output power If switching noise is significant--for instance, because output power is large--a high negative voltage may be applied to the OCL pin. Since the MS100xSH series are single power supply ICs, a negative voltage may damage the IC or cause malfunctions. The following diagram shows a circuit that incorporates a feature to protect the OCL pin against negative voltages. The added diode D301 should have small VF (a Schottky barrier diode is recommended) and should be connected as close as possible to the pin. SHINDENGEN ELECTRIC MFG. CO. , LTD 30/41 MS1003SHMS1004SH Application Note Ver.2.2 5.5.4 Design of VG pin (1) Basic circuit The VG pin outputs switching signals. It can be used when the main switching device is a voltage-driven element. The diagram to the right shows the basic circuit configuration. The initial design values should be 10 for the gate resistor R102 and 33 k for the resistor R101 between the gate and the source. (2) Circuit requiring a drive circuit The main switching device driving performance of the MS100x series is specified under "Soft drive" of "Electric/thermal characteristics" in the specification. A circuit for enhancing the driving performance is required between the VG pin and the main SW device as shown to the right if the main switching device cannot be driven directly by the VG pin in the basic circuit (1). 6 MS1003SH MS1004SH Q302 5 3 R102 100 Q303 Refer to the diagram to the right to determine constants. R304 100 Q101 R305 10 R306 10k R104 Use the gate total charge quantity Qg of the main switching device as a guide for determining whether a driving circuit is required. Qg of main SW device > 20 nC to 25 nC Driving circuit required QG of main SW device < 20 nC No driving circuit required (3) Handling high power Design the drive circuit as shown below if a power supply circuit requires more than one main switching device. The diagram illustrates an example of a circuit using two main SW devices. For configurations involving three main SW devices, connect the devices in parallel based on the example. Use the constants shown in the diagram as initial design values and evaluate to determine optimal constants. SHINDENGEN ELECTRIC MFG. CO. , LTD 31/41 MS1003SHMS1004SH Application Note Ver.2.2 5.5.5 Design of Vcc pin (1) Basic circuit The diagram to the right is the basic circuit. The circuit consists of D103 and C109 for rectifying the Nc coil output and C110 for noise reduction between Vcc and GND. For C110, use a capacitor with good frequency characteristics. Design around 0.22 F. (2) Measure against poorly regulated Vcc voltage If the Vcc voltage is not well regulated due to design conditions, such as the load specification, add R110 as shown below to the left. This is generally the most cost-effective way to improve regulation. The chart to the right shows model lines of Vcc voltage regulation relative to output power. The red line represents Vcc voltage regulation with the basic circuit (1). The measure adjusts behavior to the black line. Previous Vcc regulation Vcc voltage Vcc OVP voltage Improved Vcc regulation Output power (3) Measure against poorly regulated Vcc voltage The diagram below shows a circuit that improves regulation more effectively than measure (2). SHINDENGEN ELECTRIC MFG. CO. , LTD 32/41 MS1003SHMS1004SH Application Note Ver.2.2 Initial design value Recommended value R310 560 220 -1 k DZ303 18 V 16 V-22 V * Keep in mind potential losses associated with R310. OVP voltage Vcc voltage Vcc This measure will improve the regulation (represented by the red line) and move it to the black line on the chart to the right. The voltage setting of DZ303 is the operating point of DZ303, as shown to the right. Previous Vcc regulation Operating point of DZ303 This circuit incorporating this measure is the most effective circuit available when using super standby mode. No losses occur in super standby mode. Output power (4) Measure against poorly regulated Vcc voltage If the measures described in Section (2) and (3) above do not work, use a dropper circuit as shown below to stabilize Vcc. Use the constants given below as guidelines. When selecting DZ304, note the withstand voltage between Q306 and EB. If the withstand voltage between Q306 and EB is 5 V, select 22 V or greater. If the withstand voltage between Q306 and EB is 7 V, select 20 V or greater. The chart to the right shows a Vcc regulation model after implementing the measures above. Activating the dropper circuit stabilizes the voltage. When DZ305 activates, the voltage becomes the OVP voltage. Previous Vcc regulation OVP voltage Vcc voltage Vcc This measure stabilizes the Vcc pin voltage to the zener voltage of DZ304 plus VBE of Q306. Unless DZ305 is added as shown in the diagram above, OVP of the Vcc pin cannot be used. Set the zener voltage of DZ305 so that the OVP functions properly. Operating point of dropper circuit Operating point of DZ305 Output power SHINDENGEN ELECTRIC MFG. CO. , LTD 33/41 MS1003SHMS1004SH Application Note Ver.2.2 (5) Circuit protection The Vcc pin may break down during a short circuit test. If so, protect the circuit using a zener diode (DZ306), as shown to the right. A zener diode for 30 V or greater should have negligible effect on IC functions for normal use. 5.5.6 Setting resonating capacitor The capacitance set for the resonating capacitor should be between 100 pF and 3,300 pF for real-world applications. No other restrictions apply. (1) Conditions under which a relatively large capacitance is selected The partial resonance trough is close to 0 V because, for example, input voltage is low and switching loss is expected to be very small. The conducted emissions are high. The surge voltage is large relative to the withstand voltage of the main switching device, and there is no margin. (2) Conditions under which a relatively small capacitance is selected The main switching device generates significant heat. Standby power must be minimized. The following table lists the effects of changes in the capacitance of the resonating capacitor on power supply performance. Reduce capacitance. Item Increase capacitance. Rise Fall Droop point power Increase Decrease Heat buildup in the main SW Decrease Increase Main SW device current immediately after powering on Decrease Increase Main SW peak current under the same output power conditions Decrease Increase Regulation of output voltage Decline Improve Regulation of Vcc voltage Decline Improve Power supply efficiency Improve Decline Rising tendency Declining tendency Main SW device peak voltage Noise In efforts to optimize power supply performance, changes in the capacitance of the resonating capacitor often involve trade-offs. Carefully examine the advantages and disadvantages of the change when determining the constants. It may be possible to improve the trade-offs by redesigning the transformer. Consider redesigning the transformer to optimize power supply performance. SHINDENGEN ELECTRIC MFG. CO. , LTD 34/41 MS1003SHMS1004SH Application Note Ver.2.2 6. Example circuit diagram 6.1 Circuit diagram L101 HF2316-A103Y1R0 F101 10mH AC250V 1.6A 1A C102 AC250V 1000pF C101 AC250V 0.1F AC AC C103 AC250V 1000pF AC85132V D201 SG5S6M T101 ECO2219 D101 S1WB80 C105 1kV 470pF R104 0.39 2W C104 200V 100F L201 2.6A 4.7H Np GND C201 16V 1500F R102 10 0.5W R101 33k R201 3.3k 0.25W R202 2.2k PC101 PC123 R110 D103 1 0.5W M1FL20U IC111 MS1003SH 8 1 Vin 7 2 Z/C NC F/B 6 3 Vcc GND 4 R107 47k Nc R109 150k IC201 HA17431HLTP R207 10k 0.5% R208 6.8k 0.25W Super standby mode switching circuit R209 100k PC102 PC123 Q201 DTC114EUA High signal: NormalMode Mode HighNormal Low signal: SP Stby Stby Mode LowSP R106 12k PH102 PC123 PH101 PC123 R205 36k 0.5% R206 2.2k 0.5% C203 R203 50V 4.7k 0.047F C109 50V 100F OCL C107 50V 1000p Q102 2SC4081 C110 50V 0.1F VG C106 50V 220pF R105 10k D102 M1FL20U 5 +Vo 12V/2.1A Ns Q101 F5B52HP R103 100 0.25W C202 16V 470F C151 AC250V 2200pF C108 50V 100p R108 68k This circuit is based on the results of calculations described in Section 6.2 6.2 below. Actual values may differ from calculations due to differences in efficiency and in the response system, variance in IC thresholds, temperature IC drifts for each component, and various other factors. Use the results of calculations as guidelines. In the example circuit, the OCL resistance (R(OCL)) OCL(R (OCL) ) is changed from 0.37 to 0.39 due to discrepancies between the actual 0.370.39 device and calculations. The transformer inductance at AL-value = 140 has AL-value=140 been changed from 0.656 mH to 0.647 mH based on information from the 0.656mH0.647mH transformer manufacturer. 6.2 Calculations for example circuit design This section discusses the design procedure for the example circuit shown in Section 6.1. (1) I/O specification and transformer Control IC MS1003SH Input specification AC85-132V Output specification 12V/2.1A Transformer ECO2219 (made by TDK) (2) Initial design value list VDC(min) 102 [V] D 0.47 Cq 470 pF VDC(max) 187 [V] Po 25.2 [W] PL Po 1.2 [W] f(min) 50 [kHz] 0.85 Ae 46.4 [mm2] VO1 12 [V] VNC 15 [V] B 300 mT Vo1 rectification diode forward voltage: VF1 0.8 [V] VNC rectification diode forward voltage: VFNC 0.6 [V] SHINDENGEN ELECTRIC MFG. CO. , LTD 35/41 MS1003SHMS1004SH Application Note Ver.2.2 * Setting the on duty ratio (D) The on duty ratio D is determined primarily by the withstand voltage of the main switching device and the corresponding heat buildup. The following table lists changes in characteristics resulting from changes in D. Increase Fall Rise Main SW device peak current Increase Decrease Main SW device switching loss Increase Decrease Main SW device conduction loss Increase Decrease Operating frequency fluctuation range Decrease Increase Decrease On duty ratio (D) Voltage applied to the main SW device (3) Calculating the primary inductance and the main switch peak current Substitute 0.47 =9.4[s] and 50 10 3 2 25.2 1.2 Formula 9: I DP =1.484[A] into Formula 10. 0.85 102 0.47 102 9.4 10 6 Formula 10: Lp =0.646[mH] 1.484 Formula 4: t on (max)1 (4) Calculating the number of turns in the primary coil Substitute Formula 4: t on (max)1 Formula 11: Np D f (min) 0.47 =9.4[s] into Formula 11. 50 10 3 VDC (min) t on (max)1 10 7 B Ae 102 9.4 10 6 10 7 =68.88[Turn] 300 0.464 Round the result to the nearest integer, i.e., Np = 68 turns. (Round up the result when adjusting D upwards. In the example, the result is rounded down to adjust it downwards.) (5) Calculating the number of turns in the control output coil 470 10 12 =1.73[s] 1 (12 0.6) 68 ( 9.4 10 6 1.73 10 6 ) 3 50 10 =7.76[Turn] 102 9.6 10 6 Formula 6: tq 3.14 0.646 10 Formula 13: N S 1 3 Round the result to the nearest integer, i.e., NS1 = 8 turns. (Round down the result when adjusting D upwards. In the example, the result is rounded up to adjust it downwards.) SHINDENGEN ELECTRIC MFG. CO. , LTD 36/41 MS1003SHMS1004SH Application Note Ver.2.2 (6) Calculating the number of turns in the control coil Formula 15: Nc 8 15 0.8 =10.03[Turn] 12 0.6 Round the result to the nearest integer, i.e., Nc = 10 turns. (Round up the result when adjusting the voltage upwards. When adjusting it downwards, round it down.) (7) Recalculating the transformer design The actual design values of a transformer differ from initial design values because results are rounded to integers during the design process and because actual resistances and inductances differ from calculations. The differences are corrected and the OCL resistance R(OCL) and transformer core gap are determined as follows: 1) Correcting the main SW peak current and determining OCL resistance R(OCL) Calculate R(OCL) based on the relationship between the main SW peak current obtained in Section (3) and the VTH (OCL) clamp. R(OCL ) 0.54 =0.3638[] 1.484 To adjust resistance, change R(OCL) to 0.37 (e.g., 0.22 + 0.15 ). The main SW peak current changes to I DP 0.54 =1.46[A]. 0.37 2) Determining the core gap and correcting the inductance To specify the core gap when ordering a transformer, you can use the result of Formula 12 in Section 5.3. Note that using the inductance coefficient "AL-value" is more common. The AL-value is among the key parameters that determine transformer core performance, together with the NI-limit expressed in [ nH ] and magnetic saturation condition. N2 The inductance is corrected based on the assumption that the AL-value is 140. (Standard AL-values vary from manufacturer to manufacturer. Contact the transformer manufacturer to obtain more information.) Since the AL - value nH 2 , the result is 140 68 = 647360 nH. 2 N The inductance Lp is corrected to 0.647 mH. 3) Correcting initial design values From the IDP and Lp obtained in Sections 1) and 2), the initial design values are corrected as follows: Formula 10: t on (max)1 Lp I DP 0.647 10 3 1.46 =9.26 [s] V DC (min) 102 SHINDENGEN ELECTRIC MFG. CO. , LTD 37/41 MS1003SHMS1004SH Application Note Ver.2.2 Formula 6: Formula 5: tq 3.14 0.647 10 3 470 10 12 1.73[s] t off (max) On duty ratio: D 8 102 9.26 10 6 1.73 10 6 =10.55[s] 68 (12 0.6) t on (max)1 t on (max)1 t off (max) 9.26 =0.467 9.26 10.55 Minimum oscillation frequency: f (min) Formula 9: PL I DP VDC (min) D 2 1 1 =50.48[kHz] t on (max)1 t off (max) 9.26 10.55 1.46 0.85 102 0.467 =29.56[W] 2 The preceding calculation shows that the droop point power is 1.173 times the maximum power; i.e., PL 1.173 PO (max) . The following formula gives B: B V DC (min) t on (max)1 10 7 Np Ae 102 9.26 10 6 10 7 =299.35[mT] 68 0.464 The result indicates whether B presents any problems. Corrected parameters f(min) 50.48 [kHz] D 0.467 B 299.4mT Lp 0.647 [mH] tq 1.73 [s] PL Pox1.173[W] Np 68 [Turn] NS1 8 [Turn] Nc 10 [Turn] Check to determine whether these corrected values are adequate. In particular, make sure P L is not too large (the output current is not too large) or too small (there is sufficient margin relative to load) and that the resulting conditions do not lead to saturation of B. (8) Estimating the voltage applied to the main switching device After finalizing the transformer design, estimate the withstand voltage of the main switching device and check to determine whether the selected main switching device has sufficient withstand voltage. The diagram to the right shows a model waveform of the main switching device when the main switching device is off. The maximum voltage of the main switching device is estimated by calculating (1) to (4). (3) (2) (1) (4) SHINDENGEN ELECTRIC MFG. CO. , LTD 38/41 MS1003SHMS1004SH Application Note Ver.2.2 1) VDC voltage This is the same as the input capacitor voltage. Formula 2 gives the maximum value. In this example, the maximum value is 186.7 V. 2) Flyback voltage This is the transformer's flyback voltage: Np (VO1 VF 1 ) N S1 The following formula gives the voltage: 68 (12 0.6) =107.1[V] 8 3) Surge voltage This surge voltage attributable to leakage inductance varies from specification to specification and from transformer to transformer. In this example, it is estimated to be 150 V at maximum. This parameter must be confirmed using actual equipment. 4) Quasi-resonance trough voltage The higher this voltage, the greater the switching loss. This is obtained by subtracting (2) from (1) above. In this example, it is 186.7 V - 107.1 V = 79.6 V. The maximum voltage of the main switching device is 186.7 V + 107.1 V + 150 V = 443.8 V. For instance, a MOSFET capable of withstanding 500 V is suitable for use with a margin exceeding 10% (450 V). If the withstand voltage is too low, reduce on duty ratio D. Increase the on duty ratio D to make the most of quasi-resonance effects. SHINDENGEN ELECTRIC MFG. CO. , LTD 39/41 MS1003SHMS1004SH Application Note Ver.2.2 (8) Checking operating points When checking the operating points, use the design values corrected in Section 6.2 (7)-3). Work out the operating points of the example power supply in accordance with Section 5.4. The following table gives the results of calculations based on an input voltage of DC 120 V: (1) Trough skip start power 9.33[W] (2) Operating frequency at trough skip start (3) Trough skip end power Trough skip end power 1 from Formula 25 of [Condition 1] .................................................................................... 16.23[W] As DC 120 V = VDC < VDC (clamp) = 129.4 V; Trough skip end power 2 from Formula 30 of [Condition 2]-1) .................................................................................... 26.77[W] Trough skip end power 1 < Trough skip end power 2 Trough skip end power 1 is used. 16.23[W] (4) Operating frequency at trough skip end Calculated from Formulas 22 and 23 for trough skip end power 1. 60.74[kHz] (5) Auto burst start power (6) Operating frequency immediately before auto burst start (7) Auto burst end power (8) Operating frequency immediately after auto burst end (9) Droop point power Calculated from Formula 30 as DC 120 V = VDC < VDC (clamp) = 129.4 V. (10) Operating frequency at droop point 133.3[kHz] 0.62[W] 151.86[kHz] 1.03[W] 141.87[kHz] 31.8[W] 54.3[kHz] Operating frequency [kHz] The chart below shows a model of the operating frequency characteristics relative to output power indicating each operating point. Check the operating points (1) to (10). (6) (8) (2) (4) (10) (5)(7) (1) (3) Output power [W] (9) SHINDENGEN ELECTRIC MFG. CO. , LTD 40/41 MS1003SHMS1004SH Application Note Ver.2.2 MS1003SH/MS1004SH Application note Ver.2.2 Issued by: Devices development department 2, Electronic device division Issued: April 13, 2012 SHINDENGEN ELECTRIC MFG. CO., LTD SHINDENGEN ELECTRIC MFG. CO. , LTD 41/41 Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: Shindengen: MS1004SH-5072 MS1003SH-5072