For Non-Isolated Off-Line PWM Controllers with Integrated Power MOSFET STR5A450 Series Data Sheet Description Package The STR5A450 Series is power ICs for switching power supplies, incorporating a MOSFET and a current mode PWM controller IC for non-isolated Buck converter and Inverting converter topologies. The operation mode is automatically changed, in response to load, to the fixed switching frequency, to the switching frequency control, and to the burst oscillation mode. Thus the power efficiency is improved. The product achieves high cost-performance power supply systems with few external components. DIP8 S/OCP 1 8 D/ST FB 2 7 D/ST GND 3 6 D/ST VCC 4 5 D/ST Not to scale Features ● ● ● ● ● ● ● ● ● ● Buck converter Inverting converter Current mode type PWM control Automatically changed operation mode in response to load conditions Fixed switching frequency mode, 60 kHz (typ.) Green mode, 23 kHz (typ.) to 60 kHz (typ.) Burst oscillation mode Built-in Startup Function reducing power consumption, and shortening the startup time Built-in Error Amplifier Random Switching Function Leading Edge Blanking Function Soft Start Function Protections Overcurrent Protection (OCP): adjustabe by an external current detection resistor, including OCP input compensation function Overload Protection (OLP): Auto-restart Overvoltage Protection (OVP): Auto-restart Thermal Shutdown with hysteresis (TSD): Auto-restart Typical Application (Buck Convertor, DIP8) STR5A450D D/ST VCC D/ST GND D/ST FB D/ST S/OCP 5 3 6 7 8 D1 4 C4 R1 C2 C3 R2 D2 L1 ROCP VOUT (+) U1 VAC C1 D3 ● Electrical Characteristics fOSC(AVG) = 60 kHz (typ.) VD/ST = 650V (max.) Products RDS(ON) (max.) STR5A451D 4.0 Ω IOUT(MAX)* (Universal, open frame, VOUT = 24 V) 0.7 A STR5A453D 1.9 Ω 0.9 A * The output power is actual continues current that is measured at 50 °C ambient. The peak output current can be 120 to 140 % of the value stated here. Thermal design affects the output current. It may be less than the value stated here. Recommended Operating Condition Buck Inverting Converter Converter AC 85 V to AC 265 V Input Voltage D/ST Input ≥ 40 V Voltage Output Voltage > 11 V > – 27.5 V Range* < 27.5 V < – 11 V *Add a zener diode or a regulator to VCC pin when target output voltage is high. R3 2 1 STR5A450 Series C5 R4 (-) TC_STR5A450_1_R1 Applications ● White goods ● Auxiliary power supply (lighting equipment with microcomputer, etc.) ● Power supply for motor control (actuator, etc.) ● Telecommunication equipment (convertible from 48VDC to 15VDC) ● Other Switchung mode power supply, SMPS STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 1 STR5A450 Series CONTENTS Description ------------------------------------------------------------------------------------------------------ 1 1. Absolute Maximum Ratings ----------------------------------------------------------------------------- 3 2. Electrical Characteristics -------------------------------------------------------------------------------- 3 3. Performance Curves -------------------------------------------------------------------------------------- 5 3.1 Derating Curves ------------------------------------------------------------------------------------- 5 3.2 MOSFET Safe Operating Area Curves --------------------------------------------------------- 5 3.3 Ambient Temperature versus Power Dissipation Curves ----------------------------------- 6 3.4 Transient Thermal Resistance Curves ---------------------------------------------------------- 6 4. Block Diagram --------------------------------------------------------------------------------------------- 7 5. Pin Configuration Definitions --------------------------------------------------------------------------- 7 6. Typical Application --------------------------------------------------------------------------------------- 8 7. External Dimensions and Marking Diagram -------------------------------------------------------- 9 8. Operational Description ------------------------------------------------------------------------------- 10 8.1 Startup Operation of IC ------------------------------------------------------------------------- 10 8.2 Undervoltage Lockout (UVLO) ---------------------------------------------------------------- 10 8.3 Power Supply Startup and Soft Start Function --------------------------------------------- 10 8.4 Constant Voltage (CV) Control----------------------------------------------------------------- 11 8.4.1 Buck Converter Operation ---------------------------------------------------------------- 12 8.4.2 Inverting Converter Operation ----------------------------------------------------------- 12 8.5 Leading Edge Blanking Function -------------------------------------------------------------- 13 8.6 Random Switching Function -------------------------------------------------------------------- 13 8.7 Operation Mode ----------------------------------------------------------------------------------- 13 8.8 Overcurrent Protection (OCP) ----------------------------------------------------------------- 14 8.8.1 OCP Operation ------------------------------------------------------------------------------ 14 8.8.2 OCP Input Compensation Function ----------------------------------------------------- 14 8.9 Overload Protection (OLP) ---------------------------------------------------------------------- 14 8.10 Overvoltage Protection (OVP) ------------------------------------------------------------------ 15 8.11 Thermal Shutdown (TSD) ----------------------------------------------------------------------- 15 9. Design Notes ---------------------------------------------------------------------------------------------- 15 9.1 External Components ---------------------------------------------------------------------------- 15 9.1.1 Input and Output Electrolytic Capacitor ----------------------------------------------- 16 9.1.2 Inductor --------------------------------------------------------------------------------------- 16 9.1.3 VCC Pin Peripheral Circuit --------------------------------------------------------------- 16 9.1.4 FB Pin Peripheral Circuit ----------------------------------------------------------------- 16 9.1.5 Freewheeling diode -------------------------------------------------------------------------- 16 9.1.6 Bleeder resistance --------------------------------------------------------------------------- 16 9.2 D/ST Pin --------------------------------------------------------------------------------------------- 16 9.3 Inductance Calculation --------------------------------------------------------------------------- 17 9.3.1 Parameter Definition ----------------------------------------------------------------------- 17 9.3.2 Buck Convertor ------------------------------------------------------------------------------ 18 9.3.3 Inverting Convertor ------------------------------------------------------------------------ 23 9.4 PCB Trace Layout -------------------------------------------------------------------------------- 28 10. Reference Design of Power Supply ------------------------------------------------------------------ 30 10.1 Buck Converter ------------------------------------------------------------------------------------ 30 10.2 Inverting Converter ------------------------------------------------------------------------------- 31 IMPORTANT NOTES ------------------------------------------------------------------------------------- 32 STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 2 STR5A450 Series 1. Absolute Maximum Ratings ● The polarity value for current specifies a sink as "+," and a source as "−," referencing the IC. ● Unless otherwise specified, TA = 25 °C, all D/ST pins (5 pin to 8pin) are shorted. Parameter Symbol Drain Peak Current IDPEAK Avalanche Energy(1) EAS Test Conditions Pins Rating 3.6 8–1 Single pulse ILPEAK = 2.13 A 5A451D 5A453D 53 5A451D mJ 72 5A453D VS/OCP 1–3 − 2 to 5 A FB Pin Voltage VFB 2–3 − 0.3 to 7 V VCC Pin Voltage VCC 4–3 − 0.3 to 32 V D/ST Pin Voltage VD/ST 4–5 − 0.3 to VDSS V S/OCP Pin Voltage MOSFET Power Dissipation PD1 (2) 1.68 8–1 5A451D W 1.76 5A453D Control Part Power Dissipation PD2 4–3 1.3 W Operating Ambient Temperature TOP – − 40 to 125 °C Storage Temperature Tstg – − 40 to 125 °C Junction Temperature Tj – 150 °C (1) (2) 2. Notes A 5.2 8–1 ILPEAK = 2.46 A Units Single pulse, VDD = 99 V, L = 20 mH When embedding this hybrid IC onto the printed circuit board (cupper area in a 15mm×15mm) Electrical Characteristics ● The polarity value for current specifies a sink as "+," and a source as "−," referencing the IC. ● Unless otherwise specified, TA = 25 °C, all D/ST pins (5 pin to 8pin) are shorted. Parameter Symbol Test Conditions Pins Min. Typ. Max. Units Notes Power Supply Startup Operation Operation Start Voltage VCC(ON) 4–3 13.6 15.0 16.6 V Operation Stop Voltage VCC(OFF) 4–3 7.3 8.0 8.7 V Circuit Current in Operation Startup Circuit Operation Voltage Startup Current PWM Operation Average PWM Switching Frequency Switching Frequency Modulation Deviation Feedback Reference Voltage ICC(ON) VCC = 12 V 4–3 – – 3.0 mA VST(ON) VCC = 13.5 V 8–3 21 29 37 V ICC(ST) VCC = 13.5 V 4–3 – 3.0 − 1.7 – 0.9 mA VFB = VFB(REF)–20mV 8–3 53 60 67 kHz Δf 8–3 – 7.1 – kHz VFB(REF) 2–3 2.44 2.50 2.56 V fOSC(AVG) STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 3 STR5A450 Series Parameter Symbol Feedback Current(1) S/OCP Pin Standby Threshold voltage Maximum ON Duty Test Conditions Pins Min. Typ. Max. Units 2–3 − 2.4 − 0.8 − μA VOCP(STB) 1–3 – 0.11 – V DMAX 8–3 56 62 69 % IFB(OP) VFB = 2.3 V Notes Protection Leading Edge Blanking Time(1) tBW – – 280 – ns (1) DPC – – 15.8 – mV/µs (1) DDPC − − 36 − % VOCP(L) 1−3 0.640 0.735 0.830 V VOCP(H) 1−3 0.74 0.83 0.92 V VOCP(LEB) 1−3 − 1.61 − V VCC(OVP) 4–3 27.5 29.3 31.3 V ms OCP Compensation Coefficient OCP Compensation Limit Duty OCP Threshold Voltage at Zero ON-Duty OCP Threshold Voltage OCP Threshold Voltage During LEB (tBW) OVP Threshold Voltage OLP Delay Time at Startup Circuit Current in Overload Protection Delay Time of FB Pin Short Protection at Startup Standby Blanking Time at Startup Thermal Shutdown Operating Temperature(1) Thermal Shutdown Hysteresis(1) Power MOSFET Drain-to-Source Breakdown Voltage Drain Leakage Current On Resistance Switching Time Thermal Characteristics Thermal Resistance Junction to Case (2) (1) (2) tOLP VFB = 0.41 V 8–3 53 70 88 IOLP VCC = 9 V 4–3 – 300 – tFBSH VFB = 0.2 V 8–3 13.0 17.5 22.0 tSTB(INH) VFB = 2.6 V 8–3 2.0 3.0 4.0 ms Tj(TSD) – 135 – – °C Tj(TSDHYS) – – 80 – °C VDSS IDS = 50 µA 8–1 650 − − V IDSS VDS = VDSS 8–1 − − 50 μA RDS(ON) 8–1 − − 4.0 IDS = 0.4 A − − 1.9 – – 250 – – 18 tf 8–1 θj-C Ω 5A451D 5A453D ns 5A451D °C/W 5A453D Design assurance Case temperature (TC) measured at the center of the case top surface STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 4 STR5A450 Series 3. Performance Curves 3.1 Derating Curves 100 EAS Temperature Derating Coefficient (%) Safe Operating Area Temperature Derating Coefficient (%) 100 80 60 40 20 0 0 25 50 75 100 125 80 60 40 20 0 25 150 Ambient Temperature, TA (°C) 75 100 125 150 Junction Temperature, Tj (°C) Figure 3-1 SOA Temperature Derating Coefficient Curve 3.2 50 Figure 3-2 Avalanche Energy Derating Coefficient Curve MOSFET Safe Operating Area Curves When the IC is used, the safe operating area curve should be multiplied by the temperature derating coefficient derived from Figure 3-1. The broken line in the safe operating area curve is the drain current curve limited by on-resistance. Unless otherwise specified, TA = 25 °C, Single pulse. Drain Current, ID (A) 0.1ms 1 1ms 0.1 10 0.1ms Drain Current, ID (A) 10 1 S_STR5A453D_R1 ● STR5A453D S_STR5A451D_R1 ● STR5A451D 1ms 0.1 0.01 0.01 1 10 100 Drain-to-Source Voltage (V) 1000 1 10 100 1000 Drain-to-Source Voltage (V) STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 5 STR5A450 Series Ambient Temperature versus Power Dissipation Curves PD1 = 1.68 W 0 25 50 75 100 125 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 PD1 = 1.76 W 0 150 25 50 75 100 125 150 Ambient Temperature, TA (°C ) Ambient Temperature, TA (°C ) 3.4 PD1_STR5A453D_R1 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 ● STR5A453D PD1_STR5A45D_R1 Power Dissipation, PD1 (W) ● STR5A451D Power Dissipation, PD1 (W) 3.3 Transient Thermal Resistance Curves ● STR5A451D TR_STR5A451D_R1 Transient Thermal Resistance θch-c (°C/W) 10 1 0.1 0.01 1µ 10µ 100µ 1m 10m 100m 1m 10m 100m Time (s) ● STR5A453D TR_STR5A453D_R1 Transient Thermal Resistance θch-c (°C/W) 10 1 0.1 0.01 1µ 10µ 100µ Time (s) STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 6 STR5A450 Series 4. Block Diagram VCC 4 STARTUP D/ST 5, 6, 7, 8 UVLO OVP REG PROTECTION TSD DRV PWM OSC S Q R OCP Drain Peak Current Compensation 2 FB E/A Feedback Control VFB(REF) LEB S/OCP GND 1 3 BD_STR5A450_R1 5. Pin Configuration Definitions Pin Name S/OCP 1 8 D/ST 1 S/OCP FB 2 7 D/ST 2 FB 3 GND GND 3 6 D/ST 4 VCC VCC 4 5 D/ST Descriptions Power MOSFET source and Overcurrent Protection (OCP) signal input Constant voltage control signal input and overload protection signal input Ground Power supply voltage input for control part and Overvoltage Protection (OVP) signal input 5 6 7 D/ST MOSFET drain and startup current input 8 STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 7 STR5A450 Series 6. Typical Application Figure 6-1 and Figure 6-2 are the example circuits. To enhance the heat dissipation, the wide pattern layout of the D/ST pin (5 through 8 pin) is recommended. When the absolute value of the output voltage | VOUT | is 27.5 V or higher, add a zener diode DZ1 connected to D1 in serial as shown in Figure 6-3. Using the maximum on-duty of 50 % in the steady state operation, the condition of |VOUT| is shown below: | VOUT | : | VOUT | in response to the input voltage : STR5A450D D/ST VCC D/ST GND D/ST FB D/ST S/OCP 5 8 C4 3 6 7 D1 4 C3 R1 C2 R3 R2 2 D2 1 VOUT (+) L1 ROCP U1 VAC C1 D3 C5 R4 (-) TC_STR5A450_2_R1 Figure 6-1 Buck converter STR5A450D D/ST VCC D/ST GND D/ST FB D/ST S/OCP 5 3 6 7 8 D1 4 C4 C3 R1 C2 R2 1 VOUT (-) ROCP D3 U1 VAC R3 2 C1 L1 C5 D2 R4 (+) TC_STR5A450_3_R1 Figure 6-2 Inverting converter STR5A450D D1 DZ1 D2 (+) VCC 4 C4 C3 GND 3 U1 Figure 6-3 TC_STR5A450_4_R1 Increasing the absolute value of |VOUT| STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 8 STR5A450 Series 7. External Dimensions ● DIP8 NOTES: 1) Units: mm 2) Pb-free. Device composition compliant with the RoHS directive 8. Marking Diagram DIP8 8 5A45×D Part Number SKYMD 1 Lot Number Y = Last Digit of Year (0-9) M = Month (1-9,O,N or D) D = Period of days (1 to 3) 1 : 1st to 10th 2 : 11th to 20th 3 : 21st to 31st Sanken Control Number STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 9 STR5A450 Series 9. Operational Description All of the parameter values used in these descriptions are typical values, unless they are specified as minimum or maximum. With regard to current direction, "+" indicates sink current (toward the IC) and "–" indicates source current (from the IC). The common items of Buck converter and Inverting are desribed by using Buck conveter. The voltage between VCC pin and GND pin in the steady state operation is calculated as follows, where VFD1, VFD2 and VFD3 are the forward voltage of D1, D2 and D3 respectively: (2) 9.2 9.1 Startup Operation of IC Figure 9-1 shows the circuit around VCC pin. U1 ISTRTUP STARTUP Normal operation 4 VCC Contro1 Startup operation D2 D1 C4 GND C3 Undervoltage Lockout (UVLO) Figure 9-2 shows the relationship of VCC pin voltage and the circuit current, ICC. When VCC pin voltage increases to VCC(ON) = 15.0 V, the control circuit starts switching operation and the circuit current, ICC, increases. When VCC pin voltage decreases to VCC(OFF) = 8.0 V, the control circuit stops its operation by the Undervoltage Lockout (UVLO) circuit, and reverts to the state before startup. 3 C1 VOUT (＋) ROCP S/OCP D/ST L1 1 D3 R4 Stop C5 Circuit current, ICC Start 5~8 (－) Figure 9-1 VCC pin peripheral circuit in Buck converter The IC incorporates the startup circuit. The circuit is connected to D/ST pin. When D/ST pin voltage reaches the Startup Circuit Operation Voltage VST(ON) = 29 V, the startup circuit starts operation. During the startup process, the constant current, ICC(ST) = − 1.7 mA, charges C4 at VCC pin. When VCC pin voltage increases to VCC(ON) = 15.0 V, the control circuit starts switching operation. After switching operation begins, the startup circuit turns off automatically so that its current consumption becomes zero. The approximate startup time tSTART is calculated as follows: (1) where, tSTART is the startup time of IC (s), VCC(INT) is the initial voltage on VCC pin (V). When the internal power MOSFET turns off, the output voltage, VOUT, charges C4 through D1 and D2 (Refer to Figure 9-1). VCC（OFF） VCC pin VCC（ON） voltage Figure 9-2 Relationship between VCC pin voltage and ICC 9.3 Power Supply Startup and Soft Start Function The Soft Start Function reduces the voltage and the current stress of the internal power MOSFET and the freewheeling diode, D3. Figure 9-3 shows the startup waveforms. After the IC starts, during the Standby Blanking Time at Startup, tSTB(INH), the burst oscillation mode is disabled to operate the soft start. The IC activates the soft start circuitry during the startup period. The soft start time is fixed to about 10.2 ms. During the soft start period, the overcurrent threshold is increased step-wisely (7 steps). The IC operates switching operation by the frequency responding to FB pin voltage until the output reaches the setting voltage. Here, the tLIM is defined as the period until FB pin voltage reaches 1.6 V after the IC starts. When the tLIM reaches the OLP Delay Time at Startup, tOLP, of 70 ms STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 10 STR5A450 Series and more, the IC stops switching operation. Thus, it is necessary to adjust the value of output electrolytic capacitor, C5 so that the tLIM is less than tOLP. If VCC pin voltage reaches VCC(OFF) and a startup failure occurs as shown in Figure 9-4, increase C4 value or decrease C5 value. Since the larger capacitance causes the longer startup time of IC, it is necessary to check and adjust the startup process based on actual operation in the application. Since the Leading Edge Blanking Function (Refer to Section 9.5) is disabled during the soft start period, the on-time may be less than the Leading Edge Blanking Time (tBW = 280 ns). operation. The IC controls the peak value of the voltage of a current detection resistor (VROCP) to be close to target voltage (VSC), comparing VROCP with VSC by internal FB comparator. Feedback Control circuit receives the target voltage, VSC, reversed FB pin voltage by an error amplifier (Refer to Figure 9-5 and Figure 9-6). U1 Feedback Control FB comp + VSC E/A FB + - R2 R3 2 R1 GND 3 PWM Control VCC pin voltage Startup of IC C3 L1 5~8 D/ST Normal opertion Startup of SMPS VOUT (＋) ROCP S/OCP 1 VROCP tSTART ILON D3 C1 VCC(ON) R4 C5 (－) VCC(OFF) tSTB(INH) Time D/ST pin current, ID Time FB pin voltage VFB(REF) Figure 9-5 FB pin peripheral circuit in Buck converter Soft start period, fixed to approximately 10.2 ms tLIM < tOLP - VSC + VROCP FB comparator Voltage on both side of ROCP 1.6V Drain current, ION Time Figure 9-3 Startup waveforms Figure 9-6 Drain current ID and FB comparator in steady state operation VCC pin voltage Startup success IC starts operation Target operating voltage VCC(ON) Increase with rising of output voltage VCC(OFF) Startup failure Time Startup time of IC, tSTART Figure 9-4 VCC pin voltage during startup period 9.4 Constant Voltage (CV) Control ● Decreasing load When the output load decreases, the FB pin voltage increases in response to the increase of the output voltage. Since VSC which is the output voltage of internal error amplifier becomes low, the peak value of VROCP is controlled to become low, and the peak of the drain current decreases. This control prevents the output voltage from increasing. ● Increasing load When the output load increases, the control circuit operates the reverse of the former operations. Since VSC becomes high, the peak drain current increases. This control prevents the output voltage from decreasing. The constant voltage (CV) control for power supply output adopts the peak-current-mode control method which enhances the response speed and the stable STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 11 STR5A450 Series 9.4.1 Buck Converter Operation Figure 9-7 shows the output current path in the Buck converter. Figure 9-8 shows the operational waveforms. D1 VCC 4 Contro1 U1 D2 C4 FB 2 C3 GND 3 5~8 1 IL ROCP L1 2) PWM Off-Time Period When the internal power MOSFET turns off, the back electromotive force occurs in the inductor, L1, the freewheeling diode, D3, is forward biased and turns on. Thus, the ILOFF current flows as shown in Figure 9-7. As shown in Figure 9-8, after the average switching period, C AVG ), the power MOSFET turns on again, and the event moves to the previous 1). VOUT (＋) The output current is equal to the average inductor current of L1. R4 9.4.2 VL C1 VIN ILON (MOSFET ON) D3 ILOFF (MOSFET OFF) C5 (－) Inverting Converter Operation Figure 9-9 shows the output current path in the Inverting converter. Figure 9-10 shows the operational waveforms. Figure 9-7 Output current path in Buck converter VL MOSFET ON OFF ON D1 VCC 4 Contro1 U1 C4 FB 2 C3 GND 3 VIN-VRON-VOUT 5~8 0 1 D2 D3 ROCP VOUT (－) t -(VOUT+VFD3) C1 VIN IL ILON (MOSFET ON) VL C5 IL ILOFF (MOSFET OFF) R4 L1 t (＋) t Figure 9-9 Output current path in Inverting converter ILON ILOFF t VL 1/fOSC(AVG) Figure 9-8 Operational waveforms in Buck converter MOSFET ON OFF VIN-VRON t 0 -(VOUT+VFD3) In the Buck converter, the PWM control is described in the following. 1) PWM On-Time Period When the internal power MOSFET turns on, the ILON current flows as shown in Figure 9-7, and the inductor, L1, stores some energy. Since the ILON flows through the current detection resistor, ROCP, the voltage of ROCP is detected as the current detection voltage, VROCP. FB pin voltage is the voltage divided C3 voltage by voltage dividing resistors, and the target voltage, V SC, is given by FB pin voltage. When VROCP reaches VSC, the power MOSFET turns off. ON IL t ILON t ILOFF t 1/fOSC(AVG) Figure 9-10 Operational waveforms in Inverting converter STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 12 STR5A450 Series In the Inverting converter, the PWM control is described in the following. 1) PWM On-Time Period When the internal power MOSFET turns on, the ILON current flows as shown in Figure 9-9, and the inductor, L1, stores some energy. Since the ILON flows through the current detection resistor, ROCP, the voltage of ROCP is detected as the current detection voltage, VROCP. FB pin voltage is the voltage divided C3 voltage by voltage dividing resistors, and the target voltage, V SC, is given by FB pin voltage. When VROCP reaches VSC, the power MOSFET turns off. 2) PWM Off-Time Period When the internal power MOSFET turns off, the back electromotive force occurs in the inductor, L1, the freewheeling diode, D3, is forward biased and turns on. Thus, the ILOFF current flows as shown in Figure 9-9 As shown in Figure 9-10, after the average switching period, C AVG , the power MOSFET turns on again, and the event moves to the previous 1). The output current is equal to the average current of ILOFF of L1. 9.5 Leading Edge Blanking Function The constant voltage control for power supply output adopts the peak-current-mode control method. The peak drain current is detected by the current detection resistor, ROCP. Just in turning on the internal power MOSFET, the steep surge current would occur. If the Overcurrent Protection (OCP) responds to the voltage caused by that surge current, the power MOSFET may be turned off. To prevent that response, the OCP threshold voltage increases during Leading Edge Blanking (tBW = 280 ns) just after the power MOSFET turns on, and this prevents the OCP detection from responding to the surge voltage in turning-on (Refer to Section 9.8.1). 9.6 Random Switching Function The switching frequency is randomly modulated by superposing the modulating frequency on fOSC(AVG). This function reduces the conduction noise compared with other products without this function, and simplifies noise filtering of the input lines of power supply. 9.7 Operation Mode As shown in Figure 9-12, when the output power is decreasing, together with the decrease of the drain current ID of the internal power MOSFET, the operation mode is automatically changed to the fixed switching frequency mode (60 kHz), to the Green mode controlled the switching frequency (23 kHz to 60 kHz), and to the burst oscillation mode controlled by an internal oscillator. In the Green mode, the number of switching is reduced. In the burst oscillation mode, the switching operation is stopped during a constant period. Thus, the switching loss is reduced, and the power efficiency is improved (Refer to Figure 9-13). When the output load becomes lower, FB pin voltage increases and S/OCP pin voltage decreases. The S/OCP pin voltage reaches to the S/OCP pin standby threshold voltage, VOCP(STB) = 0.11 V, the burst oscillation mode is activated. As shown in Figure 9-13, the burst oscillation mode consists of the switching period and the non-switching period. The oscillation frequency during the switching period is the Minimum Frequency of about 23 kHz. Switching frequency fOSC 60 kHz Normal operation About 23 kHz Burst oscillation Green mode Output power, PO Figure 9-12 Switching frequency in response to PO tBW ROCP voltage Surge pulse voltage width at turning on Figure 9-11 Leading Edge Blanking ID Switching period Non-switching period Switching operation of about 23 kHz Time Figure 9-13 Switching waveform at burst oscillation mode STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 13 STR5A450 Series 9.8.1 Overcurrent Protection (OCP) 1.0 OCP Operation Overcurrent Protection (OCP) detects each drain peak current level of a power MOSFET on pulse-by-pulse basis, and limits the output power when the voltage on the current detection resistor, ROCP, reaches to OCP threshold voltage. During Leading Edge Blanking Time shown in Figure 9-11, the OCP threshold voltage becomes VOCP(LEB) = 1.61 V which is higher than the normal OCP threshold voltage. Changing to this threshold voltage prevents the OCP detection from responding to the surge voltage in turning-on the power MOSFET. This function operates as protection at the condition including output shorted. When the power MOSFET turns on, the surge voltage width of the S/OCP pin should be less than t BW. To prevent surge voltage, pay extra attention to ROCP trace layout (Refer to Section 10.4). 9.8.2 OCP threshold voltage after compensating, VOCP 9.8 OCP Input Compensation Function ICs with PWM control usually have some propagation delay time. The steeper the slope of the actual drain current at a high AC input voltage is, the larger the detection voltage of actual drain peak current is, compared to VOCP. Thus, the peak current has some variation depending on AC input voltage in OCP state. To reduce the variation of peak current in OCP state, the Input Compensation Function is built-in. This function compensates the OCP threshold voltage so that it depends on AC input voltage, as shown in Figure 9-14. When AC input voltage is low, the OCP threshold voltage is controlled to become high. Thus this control reduces the difference of peak drain current between at low AC input voltage and at high. When the on-time is 6 µs or more, the OCP threshold voltage is VOCP(H) of 0.83 V. When the on-time is less than 6 µs, that is VOCP shown in Equation (3). VOCP(H) VOCP(L) 0.5 0 6 ONTime (µs) Figure 9-14 Relationship between ONTime and OCP threshold voltage after compensating 9.9 Overload Protection (OLP) When the voltage on the current detection resistor, ROCP, reaches the OCP threshold voltage, the internal power MOSFET turns off. Figure 9-15 shows the characteristic of output voltage and current. The output voltage decreases in the overload state, and FB pin voltage also decreases. When the period keeping FB pin voltage less than 1.6 V continues for OLP Delay Time at Startup, tOLP = 70 ms, the Overload Protection (OLP) is activated, and the IC stops switching operation. Thus, VCC pin voltage decreases to VCC(OFF), and the control circuit stops operation. After that, the startup circuit is activated, VCC pin voltage increases to VCC(ON) by the startup current, and the control circuit operates again. Thus, the intermittent operation by UVLO is repeated in the OLP state (Refer to Figure 9-16). This intermittent operation reduces the stress of parts including the power MOSFET and the freewheeling diode. In addition, this operation reduces power consumption because the switching period in this intermittent operation is much shorter than the oscillation stop period. When the abnormal condition is removed, the IC returns to normal operation automatically. (3) Where, VOCP(L): OCP Threshold Voltage at Zero ON Duty (V) DPC: CP Compensation Coefficient mV/μs ONTime: On-time of power M FET μs Output voltage, VOUT CV mode Output current, IOUT Figure 9-15 Overload characteristics STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 14 STR5A450 Series startup current, and the control circuit operates again. The intermittent operation by TSD and UVLO is repeated in the TSD state. After the fault condition is removed, the IC returns to normal operation automatically. Non-switching interval VCC pin voltage VCC(ON) VCC(OFF) Junction temperature, Tj Drain current, ID tOLP TSD is active Return to normal operation Tj(TSD) tOLP Tj(TSD)−Tj(TSD)HYS ON Bias Assist Function Figure 9-16 OLP operational waveform OFF OFF VCC pin voltage VCC(ON) VCC(BIAS) VCC(OFF) 9.10 Overvoltage Protection (OVP) When the voltage between VCC pin and GND pin increases to VCC(OVP) = 29.3 V or more, the Overvoltage Protection (OVP) is activated and the IC stops switching operation. The intermittent operation by UVLO is repeated in the OVP state. Refer to Section 9.9 about the intermittent operation by UVLO. When the abnormal condition is removed, the IC returns to normal operation automatically. The approximate value of output voltage VOUT(OVP) in the OVP condition is calculated by using Equation (4). Drain current, ID Figure 9-17 TSD operational waveforms 10. Design Notes (4) where, VOUT(OVP) is voltage of between VOUT(+) and VOUT − , VFD1 is the forward voltage of D1 in Figure 9-1, VFD2 is the forward voltage of D2, and VFD3 is the forward voltage of D3. 10.1 External Components Take care to use properly rated, including derating as necessary, and proper type of components. Figure 10-1 shows the peripheral circuit of IC in Buck converter. 9.11 Thermal Shutdown (TSD) Figure 9-17 shows the Thermal Shutdown (TSD) operational waveforms. When the junction temperature of the IC control circuit increases to Tj(TSD) = 135 °C (min.) or more, the TSD is activated, and the IC stops switching operation. The TSD has a temperature hysteresis. While the junction temperature of the control circuit is more than Tj(TSD)−Tj(TSD)HYS, the Bias Assist Function is enabled when VCC pin voltage decreases to about 9.4 V. While this function is activated, the startup current is supplied to VCC pin in order to keep VCC(OFF) or more, and the IC holds stopping. While the junction temperature is Tj(TSD)−Tj(TSD)HYS or less, the Bias Assist Function is disabled, and VCC pin voltage decreases to VCC(OFF) or less. Thus, the control circuit stops operation. After that, the startup circuit is activated, VCC pin voltage increases to VCC(ON) by the D1 D/ST VCC D/ST GND D/ST FB D/ST S/OCP 5 3 6 7 8 4 C4 R1 C2 C3 R2 R3 2 1 D2 L1 ROCP VOUT (+) U1 VAC C1 D3 C5 R4 (-) Figure 10-1 Peripheral circuit of IC in Buck converter STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 15 STR5A450 Series 10.1.1 Input and Output Electrolytic Capacitor Apply proper derating to ripple current, voltage, and temperature rise. The value of output electrolytic capacitor, C5, should be fulfilled the following conditions: - The specification of output ripple - Enough shorter output voltage rising time in startup than the OLP Delay Time at Startup, tOLP = 70 ms. - Low impedance types, designed for switch mode power supplies, is recommended. depends on the value of output electrical capacitor, C5. Usually the value of C3 is 0.022 μF to 0.22 μF. When C3 value is set larger, the line regulation becomes better, however, the dynamic response of the output voltage becomes worse. Be careful of that value. The voltage dividing resistor of R1, R2 and R3 is determined by the reference voltage, VFB(REF) = 2.50 V, the output voltage, VOUT, and so on. The following Equation (6) shows the relationship of them. The target value of R1 is about 10 kΩ to 22 kΩ. R2 and R3 should be adjusted in actual operation condition. The VF of D2 and D3 affects the output voltage. Thus, the diodes of low VF should be selected. The ESR of C5 should be set in the range of Equation (5). (5) where, ZCO is the ESR of electrolytic capacitor at the operation frequency (Since the ESR in general catalogs is mostly measured at 100 kHz, check the frequency characteristic.), ΔVOR is the output ripple voltage specification, and ILRP is the ripple current of inductor (Refer to Section 10.3). 10.1.2 Inductor Apply proper design margin to core temperature rise by core loss and copper loss. The inductor should be designed so that the inductor current does not saturate. Refer to Section 10.3 about the inductance. The value should be the minimum considered a negative tolerance of inductance and a decline of DC superposition characteristics. The on-time must be longer than the Leading Edge Blanking Time to control the output voltage constantly. In the universal input voltage design, the on-time is easy to become short in the condition of maximum AC input voltage and light load. Be careful not to choose too small value for the inductance (The recommended value is 100 μH or more). (6) where, VFD2 is the forward voltage of D2, and VFD3 is the forward voltage of D3. 10.1.5 Freewheeling diode D3 in Figure 10-1 is the freewheeling diode. When the internal power MOSFET turns on, the recovery current flows through D3. The current affects power loss and noise much. The VF affects the output voltage. Thus, the diode of fast recovery and low VF should be selected. 10.1.6 Bleeder resistance For light load application, the bleeder resistor, R4, in Figure 10-1 should be connected to both ends of output capacitor, C5, to prevent the increase of output voltage. The value of R4 should be satisfied with Equation (7), and should be adjusted in actual operation condition. (7) 10.1.3 VCC Pin Peripheral Circuit The reference value of C4 in Figure 10-1 is generally 10 to 47 μF. Refer to Section 9.1 about the startup time. 10.2 D/ST Pin 10.1.4 FB Pin Peripheral Circuit As shown in Figure 10-1, FB pin is input the voltage divided the voltage between VOUT(+) and GND pin by resistors. C3 is the smoothing capacitor. The value of C3 When the voltage or the current of the D/ST pins shown in Figure 10-1 exceeds the Absolute Maximum Ratings, the internal power MOSFET connected to the D/ST pin would be permanently damaged. STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 16 STR5A450 Series 10.3 Inductance Calculation 10.3.1 Parameter Definition Since this calculation is just on paper, it is necessary to take account of margins and to check operations on actual operation in the application. The following parameters refer to the circuit of Figure 6-1 and Figure 6-2. VDCIN_MIN : Min. DC input voltage at C1 VDCIN_MAX : Max. DC input voltage at C1 VOUT : Output voltage IOUT : Output current VRON : On voltage of internal power MOSFET Drain current × RDS(ON) VFD1 : D1 forward voltage VFD2 : D2 forward voltage VFD3 : D3 forward voltage VDZ1 : DZ1 zener voltage When | VOUT | is 27.5 V or more, add a zener diode or a regulator. Take care of that power loss. ROCP : Current detection resistor between S/OCP pin and GND pin The PWM control has the three operation modes shown below. Since each operation mode has that characteristic, it is necessary to take account of choosing the operation mode. The table on the right shows the comparison of three operation modes in the same input and output condition. Table 10-1 Operation mode comparison POW L ILR PRD(ON) PSW CCM Large Large Small Small Large CRM Middle Middle Middle Middle Small When the following have no values, refer to the values of Section 2. Electrical Characteristics. DON_MAX : Max. on-duty in steady operation, 0.5 KRP_MIN : 0.4 VST_MAX : Max. value of VST(ON) VDC(MAX) : Minimum DC input voltage, recommended 400 V VCC_MIN : Min. value of VCC Voltage, 10 V VCC(OVP)_MIN : Min. value of VCC(OVP) IDLIM : less than the value of IDPEAK × the derating supposed as 90 % fTYP : Typ. value of fOSC(AVG) fMIN : Minimum switching frequency, 23 kHz VOCP(L)_MIN ：Min. value of VOCP(L) VOCP(L)_TYP ：Typ. value of VOCP(L) VOCP(H)_MIN ：Min. value of VOCP(H) VOCP(H)_TYP ：Typ. value of VOCP(H) VOCP(H)_MAX ：Max. value of VOCP(H) VOCP(STB)：Typ. value of VOCP(STB) DPC：Typ. value of DPC DCM Small Small Large Large Small where, CCM : Continuous current mode, CRM : Critical current mode, DCM : Discontinuous current mode POW : Capable output power, L : Inductance value of L1, ILR : Ripple inductor current, PRDS(ON) : Conduction loss on the power MOSFET, PSW : Switching loss CCM CRM DCM ILU ILU ILU ILR ILR ILR ILL 0A tON tOFF 1/fSW I KRP = LR ILU tON tOFF 1/fSW tON tOFF tD 1/fSW Figure 10-2 Operation mode of PWM control where, fSW : Switching frequency, tON: On-time, tOFF: Off-time, tD: Discontinuous current time, ILU : Upper inductor current, ILL: Lower inductor current, ILR: Ripple inductor current, KRP : Ripple inductor current ratio, STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 17 STR5A450 Series 10.3.2 Buck Convertor (B-1) Input and Output Condition The definition refers to Section 10.3.1. Lower value is a higher value or more of either VST_MAX or VDCIN_MIN Upper value is VDC(MAX) or less. VDCIN_MAX . VOUT IOUT . In addition,IOUT also depends on the OCP setting. VDZ1 Lower value is a higher value or more of either 0 or Upper value is ROCP Lower value is ROCP(L) = . , or more. (B-2) Calculation ● Choosing DCM The on-duty for DCM, DCCM1, is set in the range of There are two calculation ways: LCALC Calculation, and Parameter Calculation assigned LUSER. (B-2-1) LCALC Calculation The inductance, LCALC, is given by choosing the operation mode at VDCIN_MIN. The parameters of both VDCIN_MIN and VDCIN_MAX are given by LCALC. The condition of IOUT : (B-2-1-1-3) Inductor current (B-2-1-1) Parameters for VDCIN_MIN DON1 is denoted the on-duty. LLH1, ILL1, and ILR1 are the upper inductor current, the lower inductor current, and the ripple inductor current, respectively. (B-2-1-1-1) On-duty in continuous operation, DCCM1 ● Choosing CCM The condition of DCCM1 : < 0.5 (B-2-1-1-2) Choosing the operation mode, and KRP1 or DDCM1 ● Choosing CCM KRP1 is set in the following range. ● Choosing CRM The condition of IOUT : ● Choosing CRM The condition of IOUT : STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 18 STR5A450 Series ● Choosing DCM (B-2-1-1-6) On-time, tON1 By DON1 and fSW1 of the choosing operation mode, If tON1 is less than 500 ns, try the procedure 1 in Section (B-2-1-1-4) to increase it. (B-2-1-1-4) Upper ROCP(H)_TMP1 temporary value of ROCP, (B-2-1-1-7) OCP threshold voltage, VOCP1 VOCP1 is given below by tON1. ● For , VOCP1 = VOCP(H)_MIN ● For , The temporary range of the current detection resistor, ROCP, is given below. where, DPC (mV/µs)、tON1 (µs) If ROCP setting has no range, try the following procedure 1. ● Procedure 1 : For CCM, reduce KRP1 or IOUT. For CRM, change to CCM. For DCM, increase DDCM1, or change to CRM or CCM. After these changes, try to calculate again from Section (B-1) Input and Output Condition. ROCP setting is set in the previous range. The switching frequency, fSW1, and the peak inductor current at OCP depend on ROCP. When ROCP is set low, fSW1 becomes low, and the peak current becomes large. (B-2-1-1-5) Switching frequency, fSW1 The fSW1 is given by the following with the ILH1 of the choosing operation mode and ROCP. The following K is a coefficient. (B-2-1-1-8) Current detection resistor, ROCP Upper value at VDCIN_MIN of the ROCP range is given below. The range of ROCP is given below. If ROCP setting has no range, try the procedure 1 in Section (B-2-1-1-4). If ROCP setting is out of the previous range, try to set it again, and then try to calculate again from Section (B-2-1-1-5). (B-2-1-1-9) Inductance, LCALC By ILH1, ILL1, and fSW1 of the choosing operation mode, fSW1 is given below by using K. where, For For , set to fMIN. , set to fTYP. The value should be the minimum considered a negative tolerance of inductance and a decline of DC superposition characteristics. If LCACL is less than 100 µH, try the procedure 1 of Section (B-2-1-1-4) to increase it. STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 19 STR5A450 Series (B-2-1-1-10) Drain RMS current and Inductor RMS current : IDRMS1, ILRMS1 The conduction loss of RDS(ON) of power MOSFET is estimated to be . 3) Calculate Switching frequency, fSW2 where, For fSW2 < fMIN, set to fMIN. For fTYP < fSW2, set to fTYP. When fSW2 is fMIN or fTYP, calculate ILH2 again by the following. This value is equivalent to the rating for inductor. (B-2-1-2) Parameters for VDCIN_MAX (B-2-1-2-1) On-duty in continuous operation, DCCM2 For fMIN ≤ fSW2 ≤ fTYP, ILH2 is the value of the previous 2). If ILH2 is IDLIM or more, try the procedure 1 in Section (B-2-1-1-4) to decrease it. 4) Calculate Lower inductor current, ILL2 The condition of DCCM2 : < 0.5 (B-2-1-2-2) Operation mode check 1) At first, calculate the following coefficients ROCP setting in Section (B-2-1-1-8) and LCALC calculated in Section (B-2-1-1-9) are used. 5) The operation mode is given by the following. ● For ILL2 > 0, CCM ● For ILL2 = 0, CRM ● For ILL2 < 0, DCM (B-2-1-2-3) DON2, fSW2, ILH2, ILL2 of the operation mode result These parameters are different in the operation mode results of Section (B-2-1-2-2)-5). ● Resulting in CCM fSW2 is the value of Section (B-2-1-2-2) - 3). ILH2 is the value of Section (B-2-1-2-2) - 3). ILL2 is the value of Section (B-2-1-2-2) - 4). 2) Calculate Upper inductor current, ILH2 ● Resulting in CRM fSW2 is the value of Section (B-2-1-2-2) - 3). STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 20 STR5A450 Series ● Resulting in DCM 1) Draw the graph of the following equations. By using this, find the values of fSW2 and ILH2 of DCM. 2) Set Switching frequency, fSW2 When fSW at the intersection of ILH2_f and ILH2_DCM is in the range of fMIN to fTYP as shown in Figure 10-3, fSW2 is set to that value. When fSW is out of the range as shown in Figure 10-4, fSW2 is set to the limited value which is fMIN or fTYP of the over range side. 3) Calculate On-duty, DON2 The condition of DDCM2 : < DCCM2 I LH (A) 5 I LH2_f ILH_f 4 I LH2_DCM ILH_dcm 3 4) Calculate ILH2, ILL2, and ILR2 ILH2 is the value at the intersection of fSW2 which is given in the previous 2) and ILH2_DCM. Otherwise, ILH2 is given below. I LH2_CRM ILH_crm 2 f MIN fmin 1 f TYP fmax 0 20 25 30 35 40 45 50 55 60 65 70 f SW (kHz) Figure 10-3 ILH2 and fSW2 of DCM Graph in which the intersection of ILH_f and ILH_DCM is in the range of fMIN to fTYP. (B-2-1-2-4) ILH2 If ILH2 is IDLIM or more, try the procedure 1 in Section (B-2-1-1-4) to decrease it. (B-2-1-2-5) On-time, tON2 I LH (A) 5 4 3 2 1 I LH2_f ILH_f I LH2_DCM ILH_dcm I LH2_CRM ILH_crm f MIN fmin f TYP fmax 0 20 25 30 35 40 45 50 55 60 65 70 f SW (kHz) Figure 10-4 ILH2 and fSW2 of DCM Graph in which the intersection of ILH_f and ILH_DCM is out of the range of fMIN to fTYP. If tON2 is less than 500 ns, try the procedure 1 in Section (B-2-1-1-4) to increase it. (B-2-1-2-6) OCP threshold voltage, VOCP2 VOCP2 is given below by tON2. ● For , VOCP2 = VOCP(H)_MIN ● For , where, DPC (mV/µs)、tON1 (µs) In DCM, ILH value at the intersection of ILH2_f and ILH2_DCM is bigger than that of ILH2_CRM. STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 21 STR5A450 Series (B-2-1-2-7) Current detection resistor, ROCP (B-2-1-2-9) Inductor current spec. Upper value at VDCIN_MAX of the ROCP range is given below. The peak current in OCP operation, IOCP, is given below. Denoting ROCP(H) as a smaller value of either ROCP(H)2 for VDCIN_MAX or ROCP(H)1 for VDCIN_MIN in Section (B-2-1-1-8), the range of ROCP is given below. The saturation current of the inductor should be enough larger than IOCP. The rating current refers to the equation of RMS in Section (B-2-1-1-10). If ROCP setting has no range, try the procedure 1 in Section (B-2-1-1-4). If ROCP setting is out of the previous range, try to set it again, and then try to calculate again from Section (B-2-1-1-5). (B-2-1-2-8) IDRMS2, ILRMS2 These are given by substituting ILH2, ILL2, DON2, and DCCM2 for ILH1, ILL1, DON1, and DCCM1 in the equation of Section (B-2-1-1-10), respectively. (B-2-2) Parameter Calculation assigned LUSER Parameter calculation assigned LUSER at VDCIN_MIN and VDCIN_MAX is similar to the way of Section (B-2-1-2) Parameters for VDCIN_MAX. Parameters assigned LUSER are given by substituting the input voltage and LUSER for VDCIN_MAX and LCALC. If the conditions of calculation aren’t satisfied, increase LUSER setting, or decrease IOUT setting, and then try to calculate again. STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 22 STR5A450 Series 10.3.3 Inverting Convertor (I-1) Input and Output Condition The definition refers to Section 10.3.1. |VOUT| is the absolute value of VOUT. VDCIN_MIN Lower value is a higher value or more of either VST_MAX or Upper value is VDC(MAX) or less. . VDCIN_MAX |VOUT| . In addition,IOUT also depends on the OCP setting. IOUT where, VDZ1 Lower value is a higher value or more of either 0 or Upper value is ROCP Lower value is ROCP(L) = . . , or more. (I-2) Calculation There are two calculation ways: LCALC Calculation, and Parameter Calculation assigned LUSER. (I-2-1-1-2) Choosing the operation mode, and KRP1 or DDCM1 ● Choosing CCM KRP1 is set in the following range. (I-2-1) LCALC Calculation The inductance, LCALC, is given by choosing the operation mode at VDCIN_MIN. The parameters of both VDCIN_MIN and VDCIN_MAX are given by LCALC. The condition of IOUT : (I-2-1-1) Parameters for VDCIN_MIN (I-2-1-1-1) On-duty in continuous operation, DCCM1, and Average inductor current, ILAVG1 The condition of DCCM1 : < 0.5 ● Choosing CRM The condition of IOUT : ● Choosing DCM On-duty, DDCM1, is set in the following range. The condition of IOUT : STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 23 STR5A450 Series (I-2-1-1-3) Inductor current DON1 is denoted the on-duty. LLH1, ILL1, and ILR1 are the upper inductor current, the lower inductor current, and the ripple inductor current, respectively. ROCP setting is set in the previous range. The switching frequency, fSW1, and the peak inductor current at OCP depend on ROCP. When ROCP is set low, fSW1 becomes low, and the peak current becomes large. ● Choosing CCM (I-2-1-1-5) Switching frequency, fSW1 The fSW1 is given by the following with the ILH1 of the choosing operation mode and ROCP. The following K is a coefficient. fSW1 is given below by using K. ● Choosing CRM where, For For , set to fMIN. , set to fTYP. (I-2-1-1-6) On-time, tON1 ● Choosing DCM By DON1 and fSW1 of the choosing operation mode, If tON1 is less than 500 ns, try the procedure 1 in Section (I-2-1-1-4) to increase it. (I-2-1-1-7) OCP threshold voltage, VOCP1 (I-2-1-1-4) Upper ROCP(H)_TMP1 temporary value of ROCP, VOCP1 is given below by tON1. ● For , VOCP1 = VOCP(H)_MIN ● For , The temporary range of the current detection resistor, ROCP, is given below. where, DPC (mV/µs)、tON1 (µs) (I-2-1-1-8) Current detection resistor, ROCP If ROCP setting has no range, try the following procedure 1. Upper value at VDCIN_MIN of the ROCP range is given below. ● Procedure 1 : For CCM, reduce KRP1 or IOUT. For CRM, change to CCM. For DCM, increase DDCM1, or change to CRM or CCM. After these changes, try to calculate again from Section (I-1) Input and Output Condition. STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 24 STR5A450 Series The range of ROCP is given below. (I-2-1-2-2) Operation mode check 1) At first, calculate the following coefficients ROCP setting in Section (I-2-1-1-8) and LCALC calculated in Section (I-2-1-1-9) are used. If ROCP setting has no range, try the procedure 1 in Section (I-2-1-1-4). If ROCP setting is out of the previous range, try to set it again, and then try to calculate again from Section (I-2-1-1-5). (I-2-1-1-9) Inductance, LCALC By ILH1, ILL1, and fSW1 of the choosing operation mode, The value should be the minimum considered a negative tolerance of inductance and a decline of DC superposition characteristics. If LCACL is less than 100 µH, try the procedure 1 of Section (I-2-1-1-4) to increase it. (I-2-1-1-10) Drain RMS current and Inductor RMS current : IDRMS1, ILRMS1 The conduction loss of RDS(ON) of power MOSFET is estimated to be . 2) Calculate Upper inductor current, ILH2 3) Calculate Switching frequency, fSW2 where, For fSW2 < fMIN, set to fMIN. For fTYP < fSW2, set to fTYP. When fSW2 is fMIN or fTYP, calculate ILH2 again by the following. This value is equivalent to the rating for inductor. (I-2-1-2) Parameters for VDCIN_MAX (I-2-1-2-1) On-duty in continuous operation, DCCM2, and Average inductor current, ILAVG2 For fMIN ≤ fSW2 ≤ fTYP, ILH2 is the value of the previous 2). If ILH2 is IDLIM or more, try the procedure 1 in Section (I-2-1-1-4) to decrease it. 4) Calculate Lower inductor current, ILL2 The condition of DCCM2 : < 0.5 STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 25 STR5A450 Series 5) The operation mode is given by the following. ● For ILL2 > 0, CCM ● For ILL2 = 0, CRM ● For ILL2 < 0, DCM (I-2-1-2-3) DON2, fSW2, ILH2, ILL2 of the operation mode result I LH (A) 5 I LH2_DCM ILH_dcm 3 I LH2_CRM ILH_crm 2 These parameters are different in the operation mode results of Section (I-2-1-2-2)-5). 1 ● Resulting in CCM 0 fSW2 is the value of Section (I-2-1-2-2)-3). I LH2_f ILH_f 4 f MIN fmin f TYP fmax 20 25 30 35 40 45 50 55 60 65 70 f SW (kHz) Figure 10-5 ILH2 and fSW2 of DCM Graph in which the intersection of ILH_f and ILH_DCM is in the range of fMIN to fTYP. ILH2 is the value of Section (I-2-1-2-2)-3) ILL2 is the value of Section (I-2-1-2-2)-4) I LH (A) 5 I LH2_f ILH_f 4 I LH2_DCM ILH_dcm 3 I LH2_CRM ILH_crm 2 ● Resulting in CRM f MIN fmin 1 f TYP fmax 0 20 25 30 35 40 45 50 55 60 65 70 f SW (kHz) fSW2 is the value of Section (I-2-1-2-2)-3). ● Resulting in DCM 1) Draw the graph of the following equations. By using this, find the values of fSW2 and ILH2 of DCM. Figure 10-6 ILH2 and fSW2 of DCM Graph in which the intersection of ILH_f and ILH_DCM is out of the range of fMIN to fTYP. In DCM, ILH value at the intersection of ILH2_f and ILH2_DCM is bigger than that of ILH2_CRM. 2) Set Switching frequency, fSW2 When fSW at the intersection of ILH2_f and ILH2_DCM is in the range of fMIN to fTYP as shown in Figure 10-5, fSW2 is set to that value. When fSW is out of the range as shown in Figure 10-6, fSW2 is set to the limited value which is fMIN or fTYP of the over range side. 3) Calculate On-duty, DON2 The condition of DDCM2 : < DCCM2 STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 26 STR5A450 Series 4) Calculate ILH2, ILL2, and ILR2 ILH2 is the value at the intersection of fSW2 which is given in the previous 2) and ILH2_DCM. Otherwise, ILH2 is given below. (I-2-1-2-8) IDRMS2、ILRMS2 These are given by substituting ILH2, ILL2, DON2, and DCCM2 for ILH1, ILL1, DON1, and DCCM1 in the equation of Section (I-2-1-1-10), respectively. (I-2-1-2-9) Inductor current spec. The peak current in OCP operation, IOCP, is given below. (I-2-1-2-4) ILH2 If ILH2 is IDLIM or more, try the procedure 1 in Section (I-2-1-1-4) to decrease it. (I-2-1-2-5) On-time, tON2 The saturation current of the inductor should be enough larger than IOCP. The rating current refers to the equation of RMS in Section (I-2-1-1-10). (I-2-2) Parameter Calculation assigned LUSER If tON2 is less than 500 ns, try the procedure 1 in Section (I-2-1-1-4) to increase it. (I-2-1-2-6) OCP threshold voltage, VOCP2 VOCP2 is given below by tON2. ● For , VOCP2 = VOCP(H)_MIN ● For , Parameter calculation assigned LUSER at VDCIN_MIN and VDCIN_MAX is similar to the way of Section (I-2-1-2) Parameters for VDCIN_MAX. Parameters assigned LUSER are given by substituting the input voltage and LUSER for VDCIN_MAX and LCALC. If the conditions of calculation aren’t satisfied, increase LUSER setting, or decrease IOUT setting, and then try to calculate again. where, DPC (mV/µs)、tON1 (µs) (I-2-1-2-7) Current detection resistor, ROCP Upper value at VDCIN_MAX of the ROCP range is given below. Denoting ROCP(H) as a smaller value of either ROCP(H)2 for VDCIN_MAX or ROCP(H)1 for VDCIN_MIN in Section (I-2-1-1-8), the range of ROCP is given below. If ROCP setting has no range, try the procedure 1 in Section (I-2-1-1-4). If ROCP setting is out of the previous range, try to set it again, and then try to calculate again from Section (I-2-1-1-5). STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 27 STR5A450 Series 4) VCC Trace Layout This is the trace for supplying power to the IC, and thus it should be as small loop as possible. If C4 and the IC are distant from each other, placing a capacitor such as film capacitor Cf about 0.1 μF to 1.0 μF close to the VCC pin and the GND pin is recommended. 10.4 PCB Trace Layout Since the PCB circuit trace design and the component layout significantly affects operation, EMI noise, and power dissipation, the high frequency PCB trace should be low impedance with small loop and wide trace. In addition, the ground traces affect radiated EMI noise, and wide, short traces should be taken into account. Figure 10-7 and Figure 10-8 show the circuit design example. 5) FB Trace Layout The divided voltage by R2+R3 and R1 of output voltage is input to the FB pin. To increase the detection accuracy, R3 and R1 should be connected to the bottom of C3 and the GND pin, respectively. The trace between R1, R2 and the FB pin should be as short as possible. 1) Main Circuit Trace Layout This is the main trace containing switching currents, and thus it should be as wide trace and small loop as possible. 2) Freewheeling Loop Layout This is the trace for the current of freewheeling diode, D3, and thus it should be as wide trace and small loop as possible. 6) Thermal Considerations Since the internal power MOSFET has a positive thermal coefficient of RDS(ON), consider it in thermal design. Since the copper area under the IC and the GND pin trace act as a heatsink, its traces should be as wide as possible. 3) Control Ground Trace Layout Since the operation of IC may be affected from the large current of the main trace that flows in control ground trace, the control ground trace should be separated from main trace and connected at single point grounding. (4) Loop of the power supply should be small (7) Trace of D/ST pin should be wide for heat release D1 D/ST VCC D/ST GND D/ST FB 5 3 8 C1 C2 R1 2 D2 R2 ROCP S/OCP D/ST R3 VOUT (＋) 1 U1 (6) Components connected to FB pin should be connected as close to FB pin as possible. C3 C4 6 7 4 L1 D3 C5 R4 (－) (1) Main trace should be wide trace and small loop (5)ROCP should be connected as close to S/OCP pin as possible. (3)Control GND trace should be connected at a single point as close to ROCP as possible. (2) Freewheeling Loop trace should be wide trace and small loop Figure 10-7 Peripheral circuit example around the IC for Buck converter STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 28 STR5A450 Series (4) Loop of the power supply should be small (7) Trace of D/ST pin should be wide for heat release D1 D/ST VCC D/ST GND D/ST FB 5 8 C3 C4 3 6 7 4 C2 R1 2 D2 R2 ROCP S/OCP D/ST (6) Components connected to FB pin should be connected as close to FB pin as possible. R3 VOUT D3 (－) 1 U1 C5 C1 R4 L1 (＋) (1) Main trace should be wide trace and small loop (5)ROCP should be connected as close to S/OCP pin as possible. (3)Control GND trace should be connected at a single point as close to ROCP as possible. (2) Freewheeling Loop trace should be wide trace and small loop Figure 10-8 Peripheral circuit example around the IC for Inverting converter STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 29 STR5A450 Series 11. Reference Design of Power Supply 11.1 Buck Converter As an example, the following show the power supply specification, the circuit schematic, the bill of materials, and the transformer specification. ● Power supply specification IC Input voltage Maximum output power Output voltage Output current STR5A453D AC 85 V to AC 265 V 15 W (max.) 15 V 1A ● Circuit schematic U1 D6 D/ST VCC D/ST GND D/ST FB D/ST S/OCP 5 1 7 F1 C4 D1 D2 D4 D3 C6 R2 R3 R4 2 L1 8 C5 3 6 CN1 4 1 CN2 D7 (+) L2 R1 C1 C2 C11 D5 C8 ZD1 R5 3 (-) TC_STR5A450_5_R2 ● Bill of materials Ratings(1) Recommended Sanken Parts F1 Fuse 250 V, 2 A C1 Film capacitor 275 V, 0.1 μF C2 Electrolytic capacitor 400 V, 56 μF (2) C4 Ceramic capacitor 50 V, 470 pF C5 Electrolytic capacitor 50 V, 10 μF, 2012 C6 Ceramic capacitor 50 V, 2.2 μF, 2012 C8 Electrolytic capacitor 50 V, 330 μF C11 Ceramic capacitor 2 kV, 22 pF D1, D2, D3, D4 Diode 600 V, 1 A D5 Fast recovery diode 600 V, 3 A RL4A D6 Fast recovery diode 90 V, 1 A SJPB-D9 D7 Fast recovery diode 600 V, 0.5 A AG01A ZD1 Zener diode Vz = 22 V, SOD-323 (2) L1 CM inductor 8.2 mH L2 Inductor 180 μH R1 Resistor 0.33 Ω, 1 W (2) R2 Resistor 10 kΩ, 1/8 W, 1608 (2) R3 Resistor 47 kΩ, 1/8 W, 1608 (2) R4 Resistor 4.7 kΩ, 1/8 W, 1608 (2) R5 Resistor 6.8 kΩ, 1/4 W, 2012 U1 AC/DC convertor IC 650 V/1.9 Ω STR5A453D (1) Unless otherwise specified, the voltage rating of capacitor is 50 V or less and the power rating of resistor is 1/8 W or less. (2) It is necessary to be adjusted based on actual operation in the application. Symbol Part type STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 30 STR5A450 Series 11.2 Inverting Converter As an example, the following show the power supply specification, the circuit schematic, the bill of materials, and the transformer specification. ● Power supply specification IC Input voltage Maximum output power Output voltage Output current STR5A453D AC 85 V to AC 265 V 15 W (max.) – 15 V 1A ● Circuit schematic U1 D6 D/ST VCC D/ST GND D/ST FB D/ST S/OCP 5 1 7 F1 D2 D4 D3 8 C6 C4 R2 R3 R4 2 L1 D1 C5 3 6 CN1 4 1 CN2 D7 (-) R1 D5 C1 C2 C11 L2 C8 ZD1 R5 3 (+) TC_STR5A450_6_R2 ● Bill of materials Ratings(1) Recommended Sanken Parts F1 Fuse 250 V, 2 A C1 Film capacitor 275 V, 0.1 μF C2 Electrolytic capacitor 400 V, 56 μF (2) C4 Ceramic capacitor 50 V, 470 pF C5 Electrolytic capacitor 50 V, 10 μF, 2012 C6 Ceramic capacitor 50 V, 2.2 μF, 2012 C8 Electrolytic capacitor 50 V, 330 μF C11 Ceramic capacitor 2 kV, 22 pF D1, D2, D3, D4 Diode 600 V, 1 A D5 Fast recovery diode 600 V, 3 A RL4A D6 Fast recovery diode 90 V, 1 A SJPB-D9 D7 Fast recovery diode 600 V, 0.5 A AG01A ZD1 Zener diode Vz = 22 V, SOD-323 (2) L1 CM inductor 8.2 mH L2 Inductor 180 μH R1 Resistor 0.33 Ω, 1 W (2) R2 Resistor 10 kΩ, 1/8 W, 1608 (2) R3 Resistor 47 kΩ, 1/8 W, 1608 (2) R4 Resistor 4.7 kΩ, 1/8 W, 1608 (2) R5 Resistor 6.8 kΩ, 1/4 W, 2012 U1 AC/DC convertor IC 650 V/1.9 Ω STR5A453D (1) Unless otherwise specified, the voltage rating of capacitor is 50 V or less and the power rating of resistor is 1/8 W or less. (2) It is necessary to be adjusted based on actual operation in the application. Symbol Part type STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 31 STR5A450 Series IMPORTANT NOTES ● All data, illustrations, graphs, tables and any other information included in this document as to anken’s products listed herein (the “Sanken Products” are current as of the date this document is issued. All contents in this document are subject to any change without notice due to improvement, etc. Please make sure that the contents set forth in this document reflect the latest revisions before use. ● The Sanken Products are intended for use as components of general purpose electronic equipment or apparatus (such as home appliances, office equipment, telecommunication equipment, measuring equipment, etc.). Prior to use of the Sanken Products, please put your signature, or affix your name and seal, on the specification documents of the Sanken Products and return them to Sanken. If considering use of the Sanken Products for any applications that require higher reliability (transportation equipment and its control systems, traffic signal control systems or equipment, disaster/crime alarm systems, various safety devices, etc.), you must contact a Sanken sales representative to discuss the suitability of such use and put your signature, or affix your name and seal, on the specification documents of the Sanken Products and return them to Sanken, prior to the use of the Sanken Products. Any use of the Sanken Products without the prior written consent of Sanken in any applications where extremely high reliability is required (aerospace equipment, nuclear power control systems, life support systems, etc.) is strictly prohibited. ● In the event of using the Sanken Products by either (i) combining other products or materials therewith or (ii) physically, chemically or otherwise processing or treating the same, you must duly consider all possible risks that may result from all such uses in advance and proceed therewith at your own responsibility. ● Although Sanken is making efforts to enhance the quality and reliability of its products, it is impossible to completely avoid the occurrence of any failure or defect in semiconductor products at a certain rate. You must take, at your own responsibility, preventative measures including using a sufficient safety design and confirming safety of any equipment or systems in/for which the Sanken Products are used, upon due consideration of a failure occurrence rate or derating, etc., in order not to cause any human injury or death, fire accident or social harm which may result from any failure or malfunction of the Sanken Products. Please refer to the relevant specification documents and Sanken’s official website in relation to derating. ● No anti-radioactive ray design has been adopted for the Sanken Products. ● No contents in this document can be transcribed or copied without anken’s prior written consent. ● The circuit constant, operation examples, circuit examples, pattern layout examples, design examples, recommended examples and evaluation results based thereon, etc., described in this document are presented for the sole purpose of reference of use of the Sanken Products and Sanken assumes no responsibility whatsoever for any and all damages and losses that may be suffered by you, users or any third party, or any possible infringement of any and all property rights including intellectual property rights and any other rights of you, users or any third party, resulting from the foregoing. ● All technical information described in this document the “Technical Information” is presented for the sole purpose of reference of use of the Sanken Products and no license, express, implied or otherwise, is granted hereby under any intellectual property rights or any other rights of Sanken. ● Unless otherwise agreed in writing between Sanken and you, Sanken makes no warranty of any kind, whether express or implied, as to the quality of the Sanken Products (including the merchantability, or fitness for a particular purpose or a special environment thereof), and any information contained in this document (including its accuracy, usefulness, or reliability). ● In the event of using the Sanken Products, you must use the same after carefully examining all applicable environmental laws and regulations that regulate the inclusion or use of any particular controlled substances, including, but not limited to, the EU RoHS Directive, so as to be in strict compliance with such applicable laws and regulations. ● You must not use the Sanken Products or the Technical Information for the purpose of any military applications or use, including but not limited to the development of weapons of mass destruction. In the event of exporting the Sanken Products or the Technical Information, or providing them for non-residents, you must comply with all applicable export control laws and regulations in each country including the U.S. Export Administration Regulations (EAR) and the Foreign Exchange and Foreign Trade Act of Japan, and follow the procedures required by such applicable laws and regulations. ● Sanken assumes no responsibility for any troubles, which may occur during the transportation of the Sanken Products including the falling thereof, out of anken’s distribution network. ● Although Sanken has prepared this document with its due care to pursue the accuracy thereof, Sanken does not warrant that it is error free and Sanken assumes no liability whatsoever for any and all damages and losses which may be suffered by you resulting from any possible errors or omissions in connection with the contents included herein. ● Please refer to the relevant specification documents in relation to particular precautions when using the Sanken Products, and refer to our official website in relation to general instructions and directions for using the Sanken Products. STR5A450-DSE Rev.1.0s SANKEN ELECTRIC CO.,LTD. Jan. 29, 2016 http://www.sanken-ele.co.jp/en © SANKEN ELECTRIC CO.,LTD. 2015 32