Application Information STR-A6000 Series PWM Off-Line Switching Regulator ICs General Description The STR-A6000 series are power ICs for switching power supplies, incorporating a power MOSFET and a current mode PWM controller IC in one package. To achieve low power consumption, the product includes a startup circuit and a standby function in the controller. Not to scale The switching modes are automatically changed according to load conditions so that the PWM mode is in normal operation and the burst mode is in light load condition. The rich set of protection features helps to realize low component counts, and high performance-to-cost power supply. Features and Benefits ▪ Current mode PWM control ▪ Brown-In and Brown-Out function: auto-restart, prevents excess input current and heat rise at low input voltage ▪ Auto Standby function: improves efficiency by burst mode operation in light load ▫ Normal load operation: PWM mode ▫ Light load operation: Burst mode ▪ No load power consumption < 25 mW ▪ Random Switching function: reduces EMI noise, and simplifies EMI filters ▪ Slope Compensation function: avoids subharmonic oscillation ▪ Leading Edge Blanking function ▪ Audible Noise Suppression function during Standby mode DIP8 package ▪ Protection features ▫ Overcurrent Protection function (OCP): pulse-by-pulse, with input compensation function ▫ Overvoltage Protection function (OVP): latched shutdown ▫ Overload Protection function (OLP): auto-restart, with timer ▫ Thermal shutdown protection (TSD): latched shutdown Applications Switching power supplies for electronic devices such as: • Battery charger for mobile phone, digital camera, camcorder, electric shaver, emergency/guide light, and so forth • Standby power supply for LCD/PDP television, desktop PC, multi-function printer, audio equipment, and so forth • Small switch-mode power supply (SMPS) for printer, BD/DVD player, CD player, set-top-box, and so forth • Auxiliary power supply for air conditioner, refrigerator, washer, dishwasher, and so forth The product lineup for the STR-A6000 series provides the following options Power MOSFET Output Power1, POUT (W) Open Frame Adaptor Part Number Features VDSS(min) RDS(ON)(max) 85 to 85 to (V) (Ω) 230 VAC 230 VAC 265 VAC 265 VAC STR-A6051M STR-A6052M STR-A6053M STR-A6079M STR-A6059H STR-A6061H STR-A6062H STR-A6069H STR-A6061HD STR-A6062HD STR-A6063HD STR-A6069HD fOSC = 67 kHz 650 800 650 fOSC = 100 kHz fOSC = 100 kHz, two types of OCP2 700 700 3.95 2.8 1.9 19.2 6 3.95 2.8 6 3.95 2.8 2.3 6 30 35 41 13 30 35 38 30 35 38 40 30 1The 21 25 29 9 19 24 26 19 24 26 27 19 20 23 26 8 17 21 23 17 21 23 25 17 16 19 22 6 11 15 18 11 15 18 20 11 listed output power is based on the thermal ratings, and the peak output power can be 120% to 140% of the value stated here. At low output voltage and short duty cycle, the output power may be less than the value stated here. 2The products suffixed D have an additional OCP function which operates during leading edge blanking period, to operate as protection at the condition such as output windings shorted or unusual withstand voltage of secondary-side diodes. STR-A6000-AN, Rev. 4.1 SANKEN ELECTRIC CO., LTD. http://www.sanken-ele.co.jp/en/ Table of Contents General Description 1 Absolute Maximum Ratings 2 Electrical Characteristics 3 Functional Block Diagram 5 Pin List Table 5 Typical Application Circuit 6 Package Diagram 7 Marking Diagram 7 Functional Description 8 Startup Operation Undervoltage Lockout (UVLO) Circuit Bias Assist Function Constant Voltage Control Operation Auto Standby Mode Function Random Switching Function Brown-In and Brown-Out Function Overcurrent Protection Function (OCP) Overvoltage Protection Function (OVP) Overload Protection Function (OLP) Thermal Shutdown Function (TSD) Design Notes 9 10 11 11 13 13 14 15 15 Peripheral Components 15 PCB Trace Layout and Component Placement 17 8 8 9 Pattern Layout Example 18 Reference Design of Power Supply 19 Important Notes 21 Absolute Maximum Ratings • The STR-A6059H is used as an example for the STR-A6000 series. • Refer to the datasheet of each product for these details. • The polarity value for current specifies a sink as "+," and a source as "−," referencing the IC. Absolute Maximum Ratings Unless otherwise specified, TA = 25°C Characteristic Drain Peak Current1 Avalanche Energy1 Symbol IDPEAK EAS Conditions Single pulse Single pulse, VDD = 99 V, L = 20 mH Pins Rating Unit 8−1 1.8 A 8−1 24 mJ ILPEAK 8−1 1.8 A S/OCP Pin Voltage VOCP 1−3 −2 to 6 V Control Part Input Voltage VCC 5−3 32 V FB/OLP Pin Voltage VFB 4−3 −0.3 to 14 V FB/OLP Pin Sink Current IFB 4−3 1.0 mA BR Pin Voltage VBR 2−3 −0.3 to 7 V BR Pin Sink Current IBR 2−3 1.0 mA Power Dissipation of MOSFET PD1 8−1 1.35 W Mounted on 15 mm × 15 mm printed circuit board Power Dissipation of Control Part PD2 5−3 1.2 W Operating Ambient Temperature2 TOP – −20 to 125 °C Storage Temperature Tstg – −40 to 125 °C Channel Temperature Tch – 150 °C 1Refer 2The to individual product datasheet for details; value differs among products. recommended internal frame temperature, TF , is 115°C (max). STR-A6000-AN, Rev. 4.1 SANKEN ELECTRIC CO., LTD. 2 Electrical Characteristics • The STR-A6059H is used as an example for the STR-A6000 series. • Refer to the datasheet of each product for these details. • The polarity value for current specifies a sink as "+," and a source as "−," referencing the IC. Electrical Characteristics of Control Part Unless otherwise specified, TA = 25°C, VCC = 18 V Characteristic Symbol Conditions Pins Min. Typ. Max. Unit V Operation Start Voltage VCC(ON) 5−3 13.8 15.3 16.8 Operation Stop Voltage1 VCC(OFF) 5−3 7.3 8.1 8.9 V 5−3 – – 2.5 mA Circuit Current in Operation ICC(ON) VCC = 12 V Minimum Start Voltage VST(ON) 5−3 – 38 – V Startup Current ISTARTUP VCC = 13.5 V 5−3 −3.7 −2.5 −1.5 mA Startup Current Threshold Biasing Voltage1 VCC(BIAS) ICC = −100 μA 5−3 8.5 9.5 10.5 V Average Operation Frequency2 fOSC(AVG) 8−3 90 100 110 kHz Frequency Modulation Deviation2 Δf 8−3 – 8 – kHz DMAX 8−3 77 83 89 % On-Time2 tON(MIN) – – 470 – ns Leading Edge Blanking Time2 tBW – – 280 – ns DPC – – 33 – mV/μs DDPC – – 36 – % V Maximum Duty Cycle Minimum OCP Compensation Coefficient2 OCP Compensation Duty Cycle Limit OCP Threshold Voltage at Zero Duty Cycle VOCP(L) 1−3 0.70 0.78 0.86 OCP Threshold Voltage at 36% Duty Cycle VOCP(H) VCC = 32 V 1−3 0.81 0.9 0.99 V Maximum Feedback Current IFB(MAX) VCC = 12 V 4−3 −340 −230 −150 μA Minimum Feedback Current IFB(MIN) 4−3 −30 −15 −7 μA FB/OLP Pin Oscillation Stop Threshold Voltage VFB(STB) 4−3 0.85 0.95 1.05 V OLP Threshold Voltage VFB(OLP) 4−3 7.3 8.1 8.9 V 4−3 54 68 82 ms 5−3 – 300 600 μA V OLP Delay Time OLP Operation Current tOLP ICC(OLP) VCC = 12 V FB/OLP Pin Clamp Voltage VFB(CLAMP) 4−3 11 12.8 14 Brown-In Threshold Voltage VBR(IN) VCC = 32 V 2−3 5.2 5.6 6 V VBR(OUT) VCC = 32 V 2−3 4.45 4.8 5.15 V VBR(CLAMP) VCC = 32 V 2−3 6 6.4 7 V 2−3 0.3 0.48 0.7 V 5−3 26 29 32 V 5−3 – 700 – μA – 135 – – °C Brown-Out Threshold Voltage BR Pin Clamp Voltage BR Function Disabling Threshold Voltage VBR(DIS) VCC Pin OVP Threshold Voltage VCC(OVP) Latch Circuits Holding Current3 ICC(LATCH) Thermal Shutdown Temperature Tj(TSD) VCC = 32 V VCC = 9.5 V 1V CC(BIAS) > VCC(OFF) always. 2Refer to individual product datasheet 3A for details; value differs among products. latch circuit is a circuit operated with Overvoltage Protection function (OVP) and/or Thermal Shutdown Protection function (TSD) in operation. STR-A6000-AN, Rev. 4.1 SANKEN ELECTRIC CO., LTD. 3 Reference Parameter Comparison Between STR-A6000M Type and STR-A6000H/HD Types Different ratings Characteristic Average Operation Frequency Frequency Modulation Deviation Minimum Duty Cycle Leading Edge Blanking Time OCP Compensation Coefficient Symbol STR-A6000M Type STR-A6000H / HD Types Unit Min. Typ. Max. Min. Typ. Max. fOSC(AVG) 60 67 74 90 100 110 kHz Δf ― 5 ― ― 8 ― kHz tON(MIN) ― 540 ― ― 470 ― ns tBW ― 340 ― ― 280 ― ns DPC ― 22 ― ― 33 ― mV/μs Electrical Characteristics of MOSFET Unless otherwise specified, TA is 25°C Pins Min. Typ. Max. Unit Drain-to-Source Breakdown Voltage* Characteristic VDSS 8–1 650 – – V Drain Leakage Current IDSS 8–1 – – 300 μA On-Resistance* RDS(ON) 8–1 – – 6 Ω Switching Time* tf 8–1 – – 250 ns – – – 22 °C/W Thermal Resistance* Symbol Rθch-C Conditions The thermal resistance between the channels of the MOSFET and the case. Case temperature, TC, is measured at the center of the case top surface. *Refer to individual product datasheet for details; value differs among products. STR-A6000-AN, Rev. 4.1 SANKEN ELECTRIC CO., LTD. 4 Functional Block Diagram 5 VCC Startup UVLO 2 BR REG VREG OVP D/ST 7,8 TSD Brown-In/ Brown-Out 6.4 V PWM OSC DRV SQ R OCP 7V VCC Drain Peak Current Compe nsa tion OLP Fe edback Control FB/OLP 4 S/OCP GND Slope Compensation 12.8 V 1 LEB 3 Pin List Table S/OCP 1 8 D/ST BR 2 7 D/ST GND 3 5 VCC FB/OLP 4 Number Name 1 S/OCP STR-A6000-AN, Rev. 4.1 Function MOSFET source, and input for Overcurrent Protection (OCP) signal 2 BR 3 GND Input for Brown-In and Brown-Out detection voltage 4 FB/OLP Feedback signal input for constant voltage control signal, and input of Overload Protection (OLP) signal 5 VCC Power supply voltage input for Control Part and input of Overvoltage Protection (OVP) signal 6 – 7, 8 D/ST Ground (Pin removed) MOSFET drain, and input of the startup current SANKEN ELECTRIC CO., LTD. 5 Typical Application Circuit The following drawings show circuits enabled and disabled the Brown-In/Brown-Out function. • In applications having a power supply specified such that VDS has large transient surge voltages, a clamp snubber circuit of a capacitor-resistor-diode (CRD) combination should be added on the primary-side winding P, or a damper snubber circuit of a capacitor (C) or a resistor-capacitor (RC) combination should be added between the D/ST pin and the S/OCP pin. The following design features should be observed: • The PCB traces from the D/ST pins should be as wide as possible, in order to enhance thermal dissipation. CRD clamp snubber BR1 C1 PC1 P C51 D1 RB S D2 8 D/ST D/ST C4 NC R51 R55 R52 C53 C52 R53 R2 U51 5 7 VCC VOUT R54 R1 C5 RA L51 D51 T1 VAC R56 D C2 U1 GND STR-A6000 S/OCP BR GND FB/OLP C（CR） Dumper snubber 1 RC 2 3 4 C10 C3 PC 1 ROCP C9 Typical application circuit example, enabled Brown-In/Brown-Out function (DC line detection) CRD clamp snubber BR1 PC1 P C51 D1 S D2 8 C4 NC R55 R52 U51 VCC C2 R51 C53 C52 R53 R2 5 7 VOUT R54 R1 C5 C1 D/ST D/ST L51 D51 T1 VAC R56 D U1 GND STR-A6000 S/OCP BR GND FB/OLP C（CR） Dumper snubber 1 2 ROCP 3 4 C3 PC 1 C9 Typical application circuit example, disabled Brown-In/Brown-Out function STR-A6000-AN, Rev. 4.1 SANKEN ELECTRIC CO., LTD. 6 Package Diagram • DIP8 package • The following show a representative type of DIP8. • The pin 6 is removed to provide greater creepage and clearance isolation between the high voltage pins (pins 7 and 8: D/ST) and the low voltage pin (pin 5: VCC). 9.4 ±0.3 5 1 4 6.5 ±0.2 8 1.0 +0.3 -0.05 +0.3 1.52 -0.05 3.3 ±0.2 7.5 ±0.5 4.2 ±0.3 3.4 ±0.1 (7.6 TYP) 0.2 5 + 0. - 0.01 5 2.54 TYP 0.89 TYP Marking Diagram ０～１５° ０～１５° 0.5 ±0.1 Unit： mm STR-A6xxH or STR-A6xxM 8 STR-A6xxHD 8 A60xxx SK YMD Lot Number Y is the last digit of the year (0 to 9) M is the month (1 to 9, O, N, or D) D is a period of days (1 to 3): 1 – 1st to 10th 2 – 11th to 20th 3 – 21st to 31st Sanken Control Number 1 A60xxH SK YMD D Part Number 1 Part Number Lot Number Y is the last digit of the year (0 to 9) M is the month (1 to 9, O, N, or D) D is a period of days (1 to 3): 1 – 1st to 10th 2 – 11th to 20th 3 – 21st to 31st Sanken Control Number Pb-free.Device composition compliant with the RoHS directive. STR-A6000-AN, Rev. 4.1 SANKEN ELECTRIC CO., LTD. 7 Functional Description • All of the parameter values used in these descriptions are typical values, according to the STR-A6059H specification, 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). BR1 T1 VAC Startup Operation C1 Figure 1 shows the VCC pin peripheral circuit, disabled the Brown-In/Brown-Out function by connecting the BR pin trace to the GND pin trace. The built-in startup circuit is connected to the D/ST pin. When the D/ST pin voltage increases to VST(ON) = 38 V, the startup circuit starts operation. In figure 1, the Startup Current, ISTARTUP , which is a constant current of –2.5 mA, is provided from the IC to capacitor C2 connected to the VCC pin, and it charges C2. When the VCC pin voltage increases to VCC(ON) = 15.3 V, the IC starts operation. After that, the startup circuit stops automatically, in order to eliminate its own power consumption. 7,8 D/ST VCC 5 UI BR 2 D2 C2 GND P R2 VD D 3 Figure 1. VCC pin peripheral circuit During the IC operation, the rectified voltage from the auxiliary winding voltage, VD , of figure 1 becomes a power source to the VCC pin. The winding turns of winding D should be adjusted so that the VCC pin voltage is applied to equation (1) within the specifications of the input voltage range and output load range of the power supply. The target voltage of the winding D is about 15 to 20 V. VCC(BIAS)(max) < VCC < VCC(OVP)(min) (1) ICC ICC(ON) = 2.5 mA (max) tSTART z C2 × VCC(ON) – VCC(INT) where: |ISTARTUP| Stop The startup time, tSTART , is determined by the value of C2, and it is approximately given as below: Start ⇒ 10.5 (V) < VCC < 26.0 (V) 8.5 V VCC(OFF) VCC pin voltage 15 V VCC(ON) (2) tSTART is the startup time in s, and VCC(INT) is the initial voltage of the VCC pin in V. Figure 2. VCC versus ICC Undervoltage Lockout (UVLO) Circuit Figure 2 shows the relationship of VCC and ICC . After the IC starts operation, when the VCC pin voltage decreases to VCC(OFF) = 8.1 V, the IC stops switching operation by the UVLO (Undervoltage Lockout) circuit and reverts to the state before startup. STR-A6000-AN, Rev. 4.1 SANKEN ELECTRIC CO., LTD. 8 Bias Assist Function Figure 3 shows the VCC pin voltage behavior during the startup period. When the VCC pin voltage increases to VCC(ON) = 15.3 V, the IC starts operation. Thus, the circuit current, ICC , increases, and the VCC pin voltage begins dropping. At the same time, the auxiliary winding voltage, VD , increases in proportion to the output voltage rise. Thus, the VCC pin voltage is set by the balance between dropping due to the increase of ICC and rising due to the increase of the auxiliary winding voltage, VD . Just at the turning-off of the power MOSFET, a surge voltage occurs at the output winding. If the feedback control is activated by the surge voltage on light load condition at startup, the output power is restricted and the output voltage decreases. VCC pin voltage Startup success IC startup Target Operating Voltage Increasing by output voltage rising Bias Assist period VCC(ON) VCC(BIAS) VCC(OFF) Startup failure Time Figure 3. VCC pin voltage during startup period When the VCC pin voltage decreases to VCC(OFF) = 8.1 V, the IC stops switching operation and a startup failure occurs. In order to prevent this, the Bias Assist function is activated when the VCC pin voltage decreases to the Startup Current Threshold Biasing Voltage, VCC(BIAS) = 9.5 V, during a state of operating feedback control. While the Bias Assist function is activated, any decrease of the VCC pin voltage is counteracted by providing the Startup Current, ISTARTUP , from the startup circuit. Thus, the VCC pin voltage is kept almost constant. By the Bias Assist function, the value of C2 is allowed to be small and the startup time becomes shorter. Furthermore, because the increase of VCC pin voltage becomes faster when the output runs with excess voltage, the response time of the OVP function becomes shorter. UI S/OCP 1 GND 3 VROCP STR-A6000-AN, Rev. 4.1 IFB Target voltage including Slope Compensation VSC – The FB/OLP pin voltage is internally added the slope compensation at the feedback control (refer to Function Block Diagram section), and the target voltage, VSC , is generated. The IC compares the voltage, VROCP , of a current detection resistor with the target voltage, VSC , by the internal FB comparator, and controls the peak value of VROCP so that it gets close to VSC , as shown in figures 4 and 5. C3 Figure 4. FB/OLP pin peripheral circuit + The constant output voltage control function uses current mode control (peak current mode), which enhances response speed and provides stable operation. 4 PC1 ROCP It is necessary to check and adjust the startup process based on actual operation in the application, so that the startup failure does not occur. Constant Voltage Control Operation FB/OLP VROCP FB Comparator OCP pin voltage Drain current ID Figure 5. Drain current, ID , and FB comparator in steady operation SANKEN ELECTRIC CO., LTD. 9 • Light load conditions When load conditions become lighter, the output voltage, VOUT , increases. Thus, the feedback current from the error amplifier on the secondary-side also increases. The feedback current is sunk at the FB/OLP pin, transferred through a photocoupler, PC1, and the FB/OLP pin voltage decreases. Thus, VSC decreases, and the peak value of VROCP is controlled to be low, and the peak drain current of ID decreases. This control prevents the output voltage from increasing. • Heavy load conditions When load conditions become greater, the IC performs the inverse operation to that described above. Thus, VSC increases and the peak drain current of ID increases. This control prevents the output voltage from decreasing. In the current mode control method, when the drain current waveform becomes trapezoidal in continuous operating mode, even if the peak current level set by the target voltage is constant, the on-time fluctuates based on the initial value of the drain current. This results in the on-time fluctuating in multiples of the fundamental operating frequency as shown in figure 6. This is called the subharmonics phenomenon. Target voltage without Slope Compensation tON1 t Even if subharmonic oscillations occur when the IC has some excess supply being out of feedback control, such as during startup and load shorted, this does not affect performance of normal operation. In the current mode control method, the FB comparator and/or the OCP comparator may respond to the surge voltage resulting from the drain surge current in turning-on the power MOSFET. As a result, the power MOSFET may turn off irregularly. In order to prevent this response to the surge voltage in turning-on the power MOSFET, Leading Edge Blanking, tBW = 280 ns (340 ns for STR-A6000M type), is built-in. Auto Standby Mode Function Auto Standby mode is activated automatically when the drain current, ID , reduces under light load conditions, at which ID is less than 15% to 20% of the maximum drain current (it is in the Overcurrent Protection state). The operation mode becomes burst oscillation, as shown in figure 7. Burst mode reduces switching losses and improves power supply efficiency because of periodic non-switching intervals. Generally, to improve efficiency under light load conditions, the frequency of the burst mode becomes just a few kilohertz. Because the IC suppresses the peak drain current well during burst mode, audible noises can be reduced. tON2 t In order to avoid this, the IC incorporates the Slope Compensation function. Because the target voltage is added a down-slope compensation signal, which reduces the peak drain current as the on-duty gets wider relative to the FB/OLP pin signal to compensate VSC, the subharmonics phenomenon is suppressed. t Figure 6. Drain current, ID , waveform in subharmonic oscillation If the VCC pin voltage decreases to VCC(BIAS) = 9.5 V during the transition to the burst mode, the Bias Assist function is activated and stabilizes the standby mode operation, because ISTARTUP is Burst oscillation Output current, IOUT Drain current, ID Below several kHz Normal operation Standby operation Normal operation Figure 7. Auto Standby mode timing STR-A6000-AN, Rev. 4.1 SANKEN ELECTRIC CO., LTD. 10 provided to the VCC pin so that the VCC pin voltage does not decrease to VCC(OFF). However, if the Bias Assist function is always activated during steady-state operation including standby mode, the power loss increases. Therefore, the VCC pin voltage should be more than VCC(BIAS), for example, by adjusting the turns ratio of the auxiliary winding and secondary-side winding and/or reducing the value of R2 in figure 16 (refer to Peripheral Components section for a detail of R2). Random Switching Function The IC modulates its switching frequency randomly within Δf = ± 4% superposed on the average operation frequency, fOSC(AVG) . The conduction noise with this function is smaller than that without this function, and this function can simplify noise filtering of the input lines of power supply. Brown-In and Brown-Out Function by DC Line Detection The BR pin detects a voltage proportional to the DC input voltage (C1 voltage), with the resistive voltage divider RA, RB, and RC connected between the DC input and GND, plus C10 connected to the BR pin, as shown in figure 8-9. This method detects peaks of the ripple voltage of the rectified AC input voltage, and thus it minimizes the influence of load conditions on the detecting voltage. During the input voltage rising from the stopped state of power supply, when the BR pin voltage increases to VBR(DIS) = 0.48 V or more, this function is enabled. After that, when the BR pin voltage increases to VBR(IN) = 5.6 V or more and the VCC pin voltage C1 Brown-In and Brown-Out Function 8 7 5 D/ST D/ST VCC UI This function stops switching operation when it detects low input line voltage, and thus prevents excessive input current and overheating. During Auto Standby mode, this function is disabled. S/OCP BR 1 Disabled Brown-In and Brown-Out Function When the Brown-In and Brown-Out function is unnecessary, connect the BR pin trace to the GND pin trace so that the BR pin voltage is VBR(DIS) = 0.48 V or less, as shown in figure 8. 2 GND FB/OLP 3 4 C3 R OCP PC1 BR pin is connected to GND Figure 8. The circuit used to disable the Brown-In and Brown-Out function EIN ID C1 RA EIN VCC pin voltage 8 RB VCC(ON) VCC(OFF) 5 7 D/ST D/ST NC VCC UI BR pin voltage VBR(IN)= 5.6 V S/OCP BR GND FB/OLP 1 RC 2 3 4 C10 C3 VBR(DIS)= 0.48 V PC1 Drain current, ID ROCP Figure 9. Brown-In and Brown-Out function controlled by DC line detection STR-A6000-AN, Rev. 4.1 VBR(OUT)= 4.8 V SANKEN ELECTRIC CO., LTD. 68 ms 11 increases to VCC(ON) or more, the IC starts switching operation. During the input voltage falling from the operated state of power supply, when the BR pin voltage decreases to VBR(OUT) = 4.8 V or less for about 68 ms, the IC stops switching operation. • Component values of the BR pin peripheral circuit: ▫ RA, RB: A few megohms. Because of high DC voltage applied and high resistance, it is recommended to select a resistor designed against electromigration or use a combination of resistors in series for that to reduce each applied voltage, according to the requirement of the application. ▫ RC: A few hundred kilohms ▫ C10: 100 to 1000 pF for high frequency noise rejection Brown-In and Brown-Out Function by AC Line Detection The BR pin detects a voltage proportional to the AC input voltage, with the resistive voltage divider RA, RB, and RC connected between one side of the AC line and GND, plus C10 connected to the BR pin and R9 connected between the BR pin and the VCC pin, as shown in figure 10.This method detects the AC input voltage, and thus it minimizes the influence from C1 charging and discharging time, or load conditions, on the detecting voltage. more, this function is enabled. After that, when the BR pin voltage increases to VBR(IN) = 5.6 V or more and the VCC pin voltage increases to VCC(ON) or more, the IC starts switching operation. During the input voltage falling from the operated state of power supply, when the BR pin voltage decreases to VBR(OUT) = 4.8 V or less for about 68 ms, the IC stops switching operation. • Component values of the BR pin peripheral circuit: ▫ RA, RB: A few megohms. Because of high DC voltage applied and high resistance, it is recommended to select a resistor designed against electromigration or use a combination of resistors in series for that to reduce each applied voltage, according to the requirement of the application. ▫ RC: A few hundred kilohms ▫ C10: 0.047 to 0.47 μF for AC ripple rejection. This should be adjusted according to values of RA, RB, and RC. ▫ R9: To enable the Brown-In and Brown-Out function, this value must be adjusted so that the BR pin voltage is more than VBR(DIS) = 0.48 V when the VCC pin voltage decreases to VCC(OFF) = 8.1 V. • High-Speed Latch Release This method is set together with the High-Speed Latch Release function. The Brown-In and Brown-Out function by AC line detection shown in figure 10 can quickly release the latch mode when the AC input, VAC, is turned off. During the input voltage rising from the stopped state of power supply, when the BR pin voltage increases to VBR(DIS) = 0.48 V or When the Overvoltage Protection function (OVP) or Thermal Shutdown function (TSD) are activated, the IC stops switching BR1 VAC VAC ID C1 R9 RA 8 VCC pin voltage VCC(ON) V CC(OFF) 5 7 D/ST D/ST NC VCC UI RB BR pin voltage VBR(IN)= 5.6 V S/OCP BR GND FB/OLP 1 RC 2 3 4 C10 C3 V BR(OUT)= 4.8 V V BR(DIS)= 0.48 V PC1 Drain current, I D ROCP 68 ms Figure 10. Brown-In and Brown-Out function controlled by AC line detection STR-A6000-AN, Rev. 4.1 SANKEN ELECTRIC CO., LTD. 12 operation in latch mode. Releasing the latch mode is done by decreasing the VCC pin voltage below VCC(OFF) = 8.1 V after unplugging the AC input, or by decreasing the BR pin voltage below VBR(OUT) = 4.8 V. This method of unplugging the AC input will spend much time until the VCC pin voltage decreases below VCC(OFF) = 8.1 V, because the release time is determined by discharge time of C1. In contrast, the configuration of the BR pin peripheral circuit shown in figure 10 makes the releasing process faster. Because the BR pin voltage immediately decreases to VBR(OUT) = 4.8 V or less when the AC input, VAC, is turned off, and thus the latch mode is quickly released. Overcurrent Protection Function (OCP) The OCP function detects each peak drain current level of the power MOSFET by the current detection resistor, ROCP . When the OCP pin voltage increases to the internal OCP threshold voltage, the IC turns off the power MOSFET on pulse-by-pulse basis, and limits the output power. ICs with PWM control usually have some detection delay time on OCP detection. The steeper the slope of the actual drain current at a high AC input voltage is, the later the actual detection point is, compared to the internal OCP threshold voltage. Thus, the actual OCP point limiting the output current usually has some variation depending on the AC input voltage, as shown in figure 11. Because the compensation signal level is designed to depend upon the on-time of the duty cycle, the OCP threshold voltage after compensation, VOCP(ONTime), is given as below. However, when the duty cycle becomes 36% or more, the OCP threshold voltage after compensation remains at VOCP(H) = 0.9 V, constantly VOCP(ONTime) (V) = VOCP(L)(V) + DPC (mV/μs) × On Time (μs). VOCP(L) is the OCP threshold voltage at zero duty cycle (V), 0.78 V DPC is the OCP compensation coefficient (mV/μs), 33 mV/μs, and On Time is the the on-time of the duty cycle (μs): On Time = On Duty / fOSC(AVG) In addition, the products suffixed D have an additional OCP function which operates during leading edge blanking period, tBW. During tBW from the moment when the power MOSFET is turning on, the OCP threshold voltage becomes VOCP(LEB) = 1.55 V. This function operates as protection at the condition such as output windings shorted or unusual withstand voltage of secondaryside diodes. After tBW , the OCP threshold voltage is changed to the value given by the above equation (3). Overvoltage Protection Function (OVP) When the voltage between the VCC pin and the GND pin is applied to the OVP threshold voltage, VCC(OVP) = 29 V or more, the Overvoltage Protection function (OVP) is activated and the IC stops switching operation. Variance resulting from propagation delay 265 VAC (as an example) 1.0 85VAC (as an example) VOCP(H) About 0.83 VOCP(L) L ow AC in p ut gh Hi inp AC ut Output Current , IOUT（A) Figure 11. Output current at OCP without input compensation STR-A6000-AN, Rev. 4.1 (3) where: OCP Threshold Voltage after Compensated, VOCP(ONTime) (V) Output Voltage, VOUT (V) The IC incorporates a built-in Input Compensation function that superposes a signal with a defined slope into the detection signal on the OCP pin as shown in figure 12. When AC input voltage is lower and the duty cycle is longer, the OCP compensation level increases more than that in high AC input voltage. Thus, the OCP point in low AC input voltage increases to minimize the difference of OCP points between low AC input voltage and high AC input voltage, without any additional components. 0.5 0 0 15 36 50 Duty Cycle, D (%) 80 Figure 12. Relationship of duty cycle and OCP threshold voltage after compensation SANKEN ELECTRIC CO., LTD. 13 When the VCC pin voltage decreases to VCC(BIAS) = 9.5 V, the startup circuit provides the Startup Current, ISTARTUP, to the VCC pin in order to prevent the VCC pin voltage from decreasing to VCC(OFF) = 8.1 V or less. Thus, the IC maintains latch mode. Releasing latch mode is done by decreasing the VCC pin voltage below VCC(OFF) = 8.1 V after unplugging the AC input. In the Brown-In and Brown-Out function by AC line detection, described above, releasing latch mode is done by the High-Speed Latch Release decreasing the BR pin voltage below VBR(OUT) = 4.8 V. When the auxiliary winding supplies the VCC pin voltage, the OVP function is able to detect an excessive output voltage, such as when the detection circuit for output control is open on the secondary-side, because the VCC pin voltage is proportional to the output voltage. UI GND VCC FB /OLP 3 IFB 4 5 D2 PC1 C3 R2 C2 D Figure 13. FB/OLP pin peripheral circuit The output voltage of the secondary-side at OVP operation, VOUT(OVP), is approximately given as below: VOUT(OVP) = VOUT(normal operation) × 29 (V) VCC(normal operation) (4) Overload Protection Function (OLP) Figure 13 shows the FB/OLP pin peripheral circuit, and figure 14 shows each waveform for OLP operation. When the peak drain current of ID is limited by OCP operation, the output voltage, VOUT , decreases and the feedback current from the secondary-side photocoupler becomes zero. Thus, the feedback current, IFB , charges C3 connected to the FB/OLP pin and the FB/OLP pin voltage increases. When the FB/OLP pin voltage increases to VFB(OLP) = 8.1 V or more for the OLP Delay Time, tOLP = 68 ms or more, the OLP function is activated and the IC stops switching operation. When the OLP function is activated, the Bias Assist function is disabled and the VCC pin voltage decreases to VCC(OFF) = 8.1 V. Thus, the IC stops switching operation by the UVLO (Undervoltage Lockout) circuit and reverts to the state before startup. After that, the startup circuit is activated, the VCC pin voltage increases to VCC(ON) = 15.3 V, and the IC starts switching operation again. In this way, the intermittent operation by UVLO is repeated during OLP state. VCC pin voltage VCC(ON) Non-switching interval V CC(OFF) FB/OLP pin voltage VFB(OLP) t OLP t OLP Drain current, ID Figure 14. OLP operation waveforms This operation reduces power stress on the power MOSFET and secondary-side rectifier. Furthermore, this reduces power consumption, because the switching period in this intermittent operation is shorter than non-switching interval. When the fault condition is removed, the IC returns to normal operation automatically. STR-A6000-AN, Rev. 4.1 SANKEN ELECTRIC CO., LTD. 14 Thermal Shutdown Function (TSD) If the temperature of the control part in the IC increases to more than Tj(TSD) = 135°C (min), the Thermal Shutdown function (TSD) is activated and the IC stops switching operation in latch mode, in the same way as the Overvoltage Protection function (OVP), described above. Releasing the latch mode is done by decreasing the VCC pin voltage below VCC(OFF) = 8.1 V after unplugging the AC input. In the Brown-In and Brown-Out function by AC line detection, releasing the latch mode is done by High-Speed Latch Release decreasing the BR pin voltage below VBR(OUT) = 4.8 V. T1 VAC D1 P C1 D2 R2 RA 8 5 7 D/ST D/ST NC VCC RB C2 D UI FB/ S/ OCP BR GND OLP Design Notes 1 Peripheral Components Take care to use the proper rating and proper type of components. RC 2 ROCP 3 C10 4 PC1 C3 • Input and output electrolytic capacitors Apply proper design margin to accommodate ripple current, voltage, and temperature rise. Figure 15. IC peripheral circuit A low ESR type for output smoothing capacitor, designed for switch-mode power supplies, is recommended to reduce output ripple voltage. • Current detection resistor, ROCP D2 Choose a low inductance and high surge-tolerant type. Because a high frequency switching current flows to ROCP , a high inductance resistor may cause poor operation. 5 VCC UI • BR pin peripheral circuit Added D C2 GND 3 The Brown-In and Brown-Out function has two types of detection method: AC line or DC line. Refer to Brown-In and BrownOut Function section for more details. • FB/OLP pin peripheral circuit R2 Figure 16. VCC pin peripheral circuit C3, located between the FB/OLP pin and the GND pin in figure 15, performs high frequency noise rejection and phase compensation, and should be connected close to these pins. The reference value of C3 is about 2200 pF to 0.01 μF, and should be selected based on actual operation in the application. • VCC pin peripheral circuit Figure 16 shows the VCC pin peripheral circuit. The reference value of C2 is generally 10 to 47 μF (refer to Startup Operation section, because the startup time is determined by the value of C2). In actual power supply circuits, there are cases in which the VCC pin voltage fluctuates in proportion to the output current, IOUT (see figure 17), and the Overvoltage Protection function (OVP) on the VCC pin may be activated. This happens because C2 is charged to a peak voltage on the auxiliary winding D, which is caused by the transient surge voltage coupled from the primary-side winding when the power MOSFET turns off. STR-A6000-AN, Rev. 4.1 VCC pin voltage Without R2 With R2 Output Current, I OUT Figure 17. VCC versus IOUT with and without resistor R2 SANKEN ELECTRIC CO., LTD. 15 For alleviating C2 peak charging, it is effective to add some value R2, of several tenths of ohms to several ohms, in series with D2 (see figure 16). The optimal value of R2 should be determined using a transformer matching what will be used in the actual application, because the variation of the auxiliary winding voltage is affected by the transformer structural design. • Phase Compensation VOUT A typical phase compensation circuit with a secondary-side shunt regulator (U51) is shown in figure 18. The reference value of C52 is about 0.047 to 0.47 μF, and should be adjusted based on actual operation in the application. L51 D51 T1 R54 PC1 R51 R55 C51 C53 R52 S • Transformer C52 R53 Apply proper design margin to core temperature rise due to core loss and copper loss. U51 Because the switching currents contain high frequency currents, the skin effect may become a consideration. Choose a suitable wire gauge in consideration of the RMS current and a current density of about 3 to 4 A/mm2. R56 GND Figure 18. Peripheral circuit around secondary-side shunt regulator (U51) If measures to further reduce temperature are still necessary, the following should be considered to increase the total surface area of the wiring: ▫ Increase the number of wires in parallel. Margin tape Fluctuation of the VCC pin voltage by IOUT worsens in the following cases, requiring a transformer designer to pay close attention to the placement of the auxiliary winding D: ▫ Poor coupling between the primary-side and secondary-side windings (this causes high surge voltage and is seen in a design with low output voltage and high output current) ▫ Poor coupling between the auxiliary winding D and the secondary-side stabilized output winding where the output line voltage is controlled constant by the output voltage feedback (this is susceptible to surge voltage) In order to reduce the influence of surge voltage on the VCC pin, figure 19 shows winding structural examples which take into consideration the placement of the auxiliary winding D: ▫ Winding structural example (a): Separating the auxiliary winding D from the primary-side windings P1 and P2. P1 and P2 are windings divided the primary-side winding into two. ▫ Winding structural example (b): Placing the auxiliary winding D within the secondary-side stabilized output winding, S1, in order to improve the coupling of those windings. S1 is a stabilized output winding of secondary-side windings, controlled to constant voltage. STR-A6000-AN, Rev. 4.1 P1 S1 P2 S2 D Margin tape Winding structural example (a) Margin tape Bobbin ▫ Thicken the wire gauge. Bobbin ▫ Use litz wire. P1 S1 D S2 S1 P2 Margin tape Winding structural example (b) P1, P2㧦 Primary main winding D㧦 Primary auxiliary winding S1㧦 Secondary stabilized output winding S2㧦 Secondary output winding Figure 19. Winding structural examples SANKEN ELECTRIC CO., LTD. 16 This is the main trace containing switching currents, and thus it should be as wide and short as possible. If the IC and C1 are distant from each other, placing a capacitor such as a film or ceramic capacitor (about 0.1 μF and with proper voltage rating) close to the transformer or the IC is recommended to reduce impedance of the high frequency current loop. (2) GND Trace Layout: GND pin to C2 (negative pin) to T1 (winding D) to R2 to D2 to C2 (positive pin) to VCC pin This is the trace for supplying power to the IC, and thus it should be as wide and short as possible. If the IC and C2 are distant from each other, placing a capacitor such as a film or ceramic capacitor (about 0.1 to 1.0 μF) close to the VCC pin and the GND pin is recommended. (3) ROCP Trace Layout ROCP should be placed as close as possible to the S/OCP pin. The connection between the power ground of the main trace and the IC ground should be at a single point ground (point A in figure 21) which is close to the base of ROCP , to reduce common impedance, and to avoid interference from switching currents to the control part in the IC. • Secondary-side Rectifier-Smoothing Circuit Trace Layout: T1 (winding S) to D51 to C51 PCB Trace Layout and Component Placement PCB circuit trace design and component layout significantly affect operation, EMI noise, and power dissipation. Therefore, pay extra attention to these designs. In general, trace loops shown in figure 20 where high frequency currents flow should be wide, short, and small to reduce line impedance. In addition, earth ground traces affect radiated EMI noise, and wide, short traces should be taken into account. Switch -mode power supplies consist of current traces with high frequency and high voltage, and thus trace design and component layouts should be done to comply with all safety guidelines. Furthermore, because the power MOSFET has a positive thermal coefficient of RDS(ON) , consider it when preparing a thermal design. Figure 21 shows a circuit layout design example. • IC Peripheral Circuit (1) S/OCP pin Trace Layout: S/OCP pin to ROCP to C1 to T1 (winding P) to D/ST pin This is the trace of the rectifier-smoothing loop, carrying the switching current, and thus it should be as wide and short as possible. If this trace is thin and long, inductance resulting from the loop may increase surge voltage at turning off the power MOSFET. Proper rectifier-smoothing trace layout helps to increase margin against the power MOSFET breakdown voltage, and reduces stress on the clamp snubber circuit and losses in it. Figure 20. High frequency current loops (hatched areas) D51 T1 R1 C5 P C1 C51 D1 S D2 8 D/ST D/ST C4 R2 5 7 NC C2 VCC D U1 Main power circuit trace S/OCP BR GND FB/OLP 1 2 3 4 C3 GND trace for the IC PC1 ROCP A C9 Figure 21. Peripheral circuit example around the IC STR-A6000-AN, Rev. 4.1 SANKEN ELECTRIC CO., LTD. 17 Pattern Layout Example The following show the PCB pattern layout example and the schematic of dual outputs circuit with STR-A6000 series. Figure 22. PCB circuit trace layout example 1 F1 L1 D1 D2 TH1 D4 D3 C1 L2 T1 L51 D51 3 VOUT1 t° C3 3 C4 R1 C55 R4 R54 R51 C2 J1 R55 R52 C51 D5 JW1 P1 PC 1 C53 S1 R53 JW2 D6 8 R6 D/ST NC VCC C5 4 GND 1 OUT2 2 GND D JW51 D52 U1 C8 R56 5 7 D/ST R8 U51 R2 R57 C52 JW52 STR-A6000 R60 R9 S/OCP BR 1 2 JW3 R7 C7 R3 C56 GND FB/OLP 3 C6 R58 C54 4 R61 R59 CP1 C9 CN51 Figure 23. Circuit schematic for PCB circuit trace layout STR-A6000-AN, Rev. 4.1 SANKEN ELECTRIC CO., LTD. 18 Reference Design of Power Supply As an example, the following show circuit schematic, bill of materials, a power supply specification, and transformer specification. F1 1 L1 D1 D2 D4 D3 L2 TH1 C1 T1 L51 D51 t° 3 R1 C3 R4 C4 C2 S1 C51 D5 R51 C55 C53 R53 S2 R8 7 D/ST D/ST NC VCC 4 GND R56 D C5 U1 STR-A6000 S/OCP BR 1 2 GND FB/OLP 3 C7 R7 U51 R57 C52 5 8 C8 R9 R2 5V/1.5A R55 R52 PC1 P1 D6 3 R54 4 C6 CP1 R3 C9 Figure 24. Reference design schematic Bill of Materials Symbol Part type Ratingsa F1 Fuse L1c CM inductor Recommended Sanken Parts Symbol Part type Ratingsa 250 VAC, 3 A R4b Metal oxide 330 kΩ, 1 W 3.3 mH R7 General 330 kΩ L2c Inductor 470 μH R8b General 2.2 MΩ TH1c NTC thermistor Short R9b General 2.2 MΩ D1 General 600 V, 1 A EM01A PC1 Photocoupler PC123 or equivalent D2 General 600 V, 1 A EM01A U1 IC – D3 General 600 V, 1 A EM01A T1 Transformer See the specification D4 General 600 V, 1 A EM01A L51 Inductor 5 μH D5 Fast recovery 1000 V, 0.5 A EG01C D51 Schottky 90 V, 4 A D6 Fast recovery 200 V, 1 A AL01Z C51 Electrolytic 680 μF, 10 V C1c Film, X2 0.047 μF, 275 V C52c Ceramic 0.1 μF, 50 V C2 Electrolytic 10 μF, 400 V C53 Electrolytic 330 μF, 10 V C3 Electrolytic 10 μF, 400 V C55c Ceramic 1000 pF, 1 kV C4 Ceramic 1000 pF, 630 V R51 General 220 Ω C5 Electrolytic 22 μF, 50 V R52 General 1.5 kΩ C6c Ceramic 0.01 μF R53c General 22 kΩ C7c Ceramic 1000 pF R54 General, 1% Short C8c Ceramic Open R55 General, 1% 10 kΩ C9 Ceramic, Y1 2200 pF, 250 V R56 General, 1% 10 kΩ R1c General Open R57 General Open R2c General 4.7 Ω U51 Shunt regulator VREF = 2.5 V, TL431 or equivalent R3 General 1.5 Ω, 1/2 W Recommended Sanken Parts STR-A6059H FMB-G19L aUnless otherwise specified, the voltage rating of capacitor is 50 V or less and the power rating of resistor is 1/8 W or less. bResistors applied high DC voltage and of high resistance are recommended to select resistors designed against electromigration or use combinations of resistors in series for that to reduce each applied voltage, according to the requirement of the application. cIt is necessary to be adjusted based on actual operation in the application. STR-A6000-AN, Rev. 4.1 SANKEN ELECTRIC CO., LTD. 19 Power Supply Specification IC STR-A6059H Input Voltage 85 to 265 VAC Maximum Output Power 7.5 W (max) Output Voltage 5V Output Current 1.5 A (max) Transformer specification ▫ Primary inductance, LP : 704 μH ▫ Core size: EI-16 ▫ AL-value: 87 nH/N2 (Center gap of about 0.26 mm) ▫ Winding specification Location Symbol Number of Turns (T) Wire (mm) Configuration Primary winding P1 73 2UEW-Ø0.18 2 layers, solenoid winding Auxiliary winding D 17 2UEW-Ø0.18×2 Solenoid winding Output winding S1-1 6 TEX-Ø0.3×2 Solenoid winding Output winding S1-2 6 TEX-Ø0.3×2 Solenoid winding D S1-2 S1-1 P1 Bobbin Cross-section view STR-A6000-AN, Rev. 4.1 VDC P1 5V S1-1 GND D/ST VCC D S1-2 GND ٨ mark shows the start point of winding SANKEN ELECTRIC CO., LTD. 20 IMPORTANT NOTES • The contents in this document are subject to changes, for improvement and other purposes, without notice. Make sure that this is the latest revision of the document before use. • Application and operation examples described in this document are quoted for the sole purpose of reference for the use of the products herein and Sanken can assume no responsibility for any infringement of industrial property rights, intellectual property rights or any other rights of Sanken or any third party which may result from its use. Unless otherwise agreed in writing by Sanken, Sanken makes no warranties of any kind, whether express or implied, as to the products, including product merchantability, and fitness for a particular purpose and special environment, and the information, including its accuracy, usefulness, and reliability, included in this document. • Although Sanken undertakes to enhance the quality and reliability of its products, the occurrence of failure and defect of semiconductor products at a certain rate is inevitable. Users of Sanken products are requested to take, at their own risk, preventative measures including safety design of the equipment or systems against any possible injury, death, fires or damages to the society due to device failure or malfunction. • Sanken products listed in this document are designed and intended for the use as components in general purpose electronic equipment or apparatus (home appliances, office equipment, telecommunication equipment, measuring equipment, etc.). When considering the use of Sanken products in the applications where higher reliability is required (transportation equipment and its control systems, traffic signal control systems or equipment, fire/crime alarm systems, various safety devices, etc.), and whenever long life expectancy is required even in general purpose electronic equipment or apparatus, please contact your nearest Sanken sales representative to discuss, prior to the use of the products herein. The use of Sanken products without the written consent of Sanken in the applications where extremely high reliability is required (aerospace equipment, nuclear power control systems, life support systems, etc.) is strictly prohibited. • When using the products specified herein by either (i) combining other products or materials therewith or (ii) physically, chemically or otherwise processing or treating the products, please duly consider all possible risks that may result from all such uses in advance and proceed therewith at your own responsibility. • Anti radioactive ray design is not considered for the products listed herein. • Sanken assumes no responsibility for any troubles, such as dropping products caused during transportation out of Sanken’s distribution network. • The contents in this document must not be transcribed or copied without Sanken’s written consent. STR-A6000-AN, Rev. 4.1 SANKEN ELECTRIC CO., LTD. 21