Application Information STR-W6000S Series PWM Off-Line Switching Regulator ICs General Description The STR-W6000S 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. 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. Not to scale Features and Benefits TO-220F-6L package ▪ 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 < 30 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 ▪ Protection features ▫ Overcurrent Protection function (OCP): pulse-by-pulse, with input compensation function ▫ Overvoltage Protection function (OVP): auto-restart ▫ Overload Protection function (OLP): auto-restart, with timer ▫ Thermal shutdown protection (TSD): auto-restart Applications Switching power supplies for electronic devices such as: • Home appliances • Digital appliances • Office automation (OA) equipment • Industrial apparatus • Communication facilities The product lineup for the STR-W6000S series provides the following options Output Power*, POUT Power MOSFET (W) fOSC Part Number (kHz) VDSS(min) RDS(ON)(max) 85 to 230 VAC (V) (Ω) 265 VAC STR-W6051S STR-W6052S STR-W6053S 67 650 3.95 2.8 1.9 45 60 90 30 40 60 *The 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. STR-W6000S-AN, Rev. 1.0 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 10 11 11 Overcurrent Protection Function (OCP) 13 Overvoltage Protection Function (OVP) 13 Overload Protection Function (OLP) 14 Thermal Shutdown Function (TSD) 15 Design Notes 15 Peripheral Components 15 PCB Trace Layout and Component Placement 17 8 8 9 9 Reference Design of Power Supply 18 Important Notes 20 Absolute Maximum Ratings • 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 Symbol Conditions Pins STR-W6051S Drain Peak Current Drain Peak Current1 IDPEAK IDMAX Rating Unit 5.0 A 7.0 A STR-W6053S 9.5 A STR-W6051S 5.0 A 7.0 A 9.5 A STR-W6052S STR-W6052S Single pulse Single pulse, TA= –20°C to 125°C 1−3 1−3 STR-W6053S 47 mJ 1−3 62 mJ 86 mJ VOCP 3−5 −2 to 6 V Control Part Input Voltage VCC 4−5 32 V FB/OLP Pin Voltage VFB 6−5 −0.3 to 14 V FB/OLP Pin Sink Current IFB 6−5 1.0 mA BR Pin Voltage VBR 7−5 −0.3 to 7 V BR Pin Sink Current IBR 7−5 1.0 mA Avalanche Energy2 EAS S/OCP Pin Voltage STR-W6051S ILPEAK = 2.0 A STR-W6052S ILPEAK = 2.3 A STR-W6053S ILPEAK = 2.7 A STR-W6051S Power Dissipation of MOSFET PD1 STR-W6052S With infinite heatsink STR-W6053S 1−3 Without heatsink 22.3 W 23.6 W 26.5 W 1.3 W Power Dissipation of Control Part PD2 4−5 0.13 W Internal Frame Temperature in Operation3 TF – −20 to 115 °C Operating Ambient Temperature TOP – −20 to 125 °C Storage Temperature Tstg – −40 to 125 °C Channel Temperature Tch – 150 °C VCC × ICC 1The maximum switching current is the drain current determined by the drive voltage of the IC and threshold voltage (Vth) of the MOSFET. pulse, VDD = 99 V, L = 20 mH. 3The recommended internal frame temperature in operation, T , is 105°C (max). F 2Single STR-W6000S-AN, Rev. 1.0 SANKEN ELECTRIC CO., LTD. 2 Electrical Characteristics • 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 Operation Start Voltage VCC(ON) 4–5 13.8 15.3 16.8 V Operation Stop Voltage* VCC(OFF) 4–5 7.3 8.1 8.9 V mA Circuit Current in Operation ICC(ON) Minimum Start Voltage VST(ON) Startup Current ISTARTUP VCC = 13.5 V Startup Current Threshold Biasing Voltage* VCC(BIAS) ICC = −100 μA Average Operation Frequency fOSC(AVG) Frequency Modulation Deviation Maximum Duty Cycle Leading Edge Blanking Time OCP Compensation Coefficient OCP Compensation Duty Cycle Limit VCC = 12 V 4–5 – – 2.5 4–5 – 40 – V 4–5 −3.9 −2.5 −1.1 mA 4–5 8.5 9.5 10.5 V 1–5 60 67 74 kHz Δf 1–5 – 5 – kHz DMAX 1–5 63 71 79 % tBW – – 390 – ns DPC – – 18 – mV/μs DDPC – – 36 – % OCP Threshold Voltage at Zero Duty Cycle VOCP(L) 3–5 0.70 0.78 0.86 V OCP Threshold Voltage at 36% Duty Cycle VOCP(H) VCC = 32 V 3–5 0.79 0.88 0.97 V Maximum Feedback Current IFB(MAX) VCC = 12 V 6–5 −340 −230 −150 μA Minimum Feedback Current IFB(MIN) 6–5 −30 −15 −7 μA FB/OLP Pin Oscillation Stop Threshold Voltage VFB(STB) 6–5 0.85 0.95 1.05 V OLP Threshold Voltage VFB(OLP) 6–5 7.3 8.1 8.9 V tOLP 6–5 54 68 82 ms OLP Delay Time OLP Operation Current FB/OLP Pin Clamp Voltage Brown-In Threshold Voltage Brown-Out Threshold Voltage BR Pin Clamp Voltage ICC(OLP) VCC = 12 V VFB(CLAMP) 4–5 – 300 – μA 6–5 11 12.8 14 V VBR(IN) VCC = 32 V 7–5 5.2 5.6 6 V VBR(OUT) VCC = 32 V 7–5 4.45 4.8 5.15 V VBR(CLAMP) VCC = 32 V 7–5 6 6.4 7 V 7–5 0.3 0.48 0.7 V BR Function Disabling Threshold Voltage VBR(DIS) VCC Pin OVP Threshold Voltage VCC(OVP) 4–5 26 29 32 V Thermal Shutdown Temperature Tj(TSD) – 130 – – °C VCC = 32 V *VCC(BIAS) > VCC(OFF) always. STR-W6000S-AN, Rev. 1.0 SANKEN ELECTRIC CO., LTD. 3 Electrical Characteristics of MOSFET Unless otherwise specified, TA is 25°C Pins Min. Typ. Max. Unit Drain-to-Source Breakdown Voltage Characteristic Symbol VDSS Conditions 1–3 650 – – V Drain Leakage Current IDSS 1–3 – – 300 μA – – 3.95 Ω 1–3 – – 2.8 Ω – – 1.9 Ω STR-W6051S On-Resistance RDS(ON) STR-W6052S STR-W6053S Switching Time tf 1–3 STR-W6051S Thermal Resistance STR-W6000S-AN, Rev. 1.0 Rθch-C The thermal resistance between the STR-W6052S channels of the MOSFET and the internal frame. STR-W6053S SANKEN ELECTRIC CO., LTD. – – – 250 ns – – 2.63 °C/W – – 2.26 °C/W – – 1.95 °C/W 4 Functional Block Diagram 4 VCC Startup UVLO 7 BR REG VREG OVP D/ST 1 TSD Brown-In/ Brown-Out 6.4 V DRV PWM OSC SQ R OCP 7V VCC Drain Peak Current Compe nsa tion OLP Fe edback Control FB/OLP 6 S/OCP GND Slope Compensation 12.8 V 3 LEB 5 Pin List Table D/ST S/OCP 1 3 VCC GND Name 1 D/ST 2 – 3 S/OCP 4 VCC Power supply voltage input for Control Part, and input of Overvoltage Protection (OVP) signal 5 GND Ground 6 FB/OLP 7 BR 4 5 FB/OLP BR Number 6 7 (LF2003) STR-W6000S-AN, Rev. 1.0 Function MOSFET drain, and input of the startup current (Pin removed) MOSFET source, and input of Overcurrent Protection (OCP) signal Feedback signal input for constant voltage control signal, and input of Overload Protection (OLP) signal Input of Brown-In and Brown-Out detection voltage 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. VAC CRD clamp snubber BR1 L51 T1 D51 C5 R1 C1 PC1 P D1 C51 R52 S R51 C52 VOUT R54 R55 C53 R53 U51 R56 RA U1 GND C(CR) damper snubber D/ST S/ OCP V CC GND FB/OLP BR S TR-W6000S 1 3 4 5 6 7 C4 RB D2 R2 C2 C10 ROCP C3 D RC C9 PC1 Typical application circuit example, enabled Brown-In/Brown-Out function (DC line detection) VAC CRD clamp snubber BR1 C5 R1 C1 L51 T1 D51 PC1 P D1 C51 S R52 R51 C52 R55 VOUT R54 C53 R53 U51 U1 R56 GND C(CR) damper snubber D/ST S/ OCP V CC GND FB/OLP BR S TR-W6000S 1 3 4 5 6 7 C4 ROCP D2 R2 C2 D C3 PC1 C9 Typical application circuit example, disabled Brown-In/Brown-Out function STR-W6000S-AN, Rev. 1.0 SANKEN ELECTRIC CO., LTD. 6 Package Diagram • TO-220F-6L package • The pin 2 is removed to provide greater creepage and clearance isolation between the high voltage pin (pin 1: D/ST) and the low voltage pin (pin 3: S/OCP). 10.0±0.2 4.2±0.2 Gate burr φ3.2±0.2 7.9±0.2 16.9±0.3 4±0.2 0.5 2.8±0.2 R-end (5.4) ) -R1 (2 6-0.65 +0.2 -0.1 6×P1.27±0.15=7.62±0.15 Dimensions between roots 10.4±0.5 6-0.74±0.15 5.0±0.5 2.8 2.6±0.1 Dimensions from root 0.45 +0.2 -0.1 5.08±0.6 Dimensions between tips 0.5 1 2 3 4 5 6 7 0.5 Front view 0.5 0.5 Side view Unit: mm Leadform: LF No.2003 Gate burr indicates protrusion of 0.3 mm (max). Pin treatment Pb-free. Device composition compliant with the RoHS directive. Marking Diagram STR W60xxS YMDD X STR-W6000S-AN, Rev. 1.0 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) DD is the day (01 to 31) X is the Sanken Control Symbol SANKEN ELECTRIC CO., LTD. 7 Functional 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). BR1 Startup Operation T1 VAC 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) = 40 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. 1 D/ST VCC 4 UI BR 7 D2 C2 GND P R2 VD D 5 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. VCC(BIAS)(max) < VCC < VCC(OVP)(min) (1) ⇒ 10.5 (V) < VCC < 26.0 (V) 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 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. 8.5 V VCC(OFF) 15.3 V VCC pin voltage VCC(ON) (2) tSTART is the startup time in s, and VCC(INT) is the initial voltage of the VCC pin in V. Undervoltage Lockout (UVLO) Circuit Figure 2. VCC versus ICC 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 again. STR-W6000S-AN, Rev. 1.0 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 3 GND 5 VROCP C3 IFB Figure 4. FB/OLP pin peripheral circuit Target voltage including Slope Compensation Constant Voltage Control Operation – The constant output voltage control function uses current mode control (peak current mode), which enhances response speed and provides stable operation. + STR-W6000S-AN, Rev. 1.0 6 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. 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. FB/OLP VSC 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 = 390 ns, is builtin. 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-W6000S-AN, Rev. 1.0 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 = 5 kHz superposed on the average operation frequency, fOSC(AVG) = 67 kHz. 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 VAC BR1 C1 1 3 BR S/OCP D/ST 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. GND UI Brown-In and Brown-Out Function 5 7 C4 R OCP 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. BR pin is connected to GND Figure 8. The circuit used to disable the Brown-In and Brown-Out function EIN ID C1 VCC pin voltage EIN VCC(ON) VCC(OFF) UI RA 1 3 5 BR GND D /ST S/OCP BR pin voltage RB 7 C10 Drain current, ID RC Figure 9. Brown-In and Brown-Out function controlled by DC line detection STR-W6000S-AN, Rev. 1.0 VBR(OUT)= 4.8 V VBR(DIS)= 0.48 V C4 ROCP VBR(IN)= 5.6 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. 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 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. BR1 VAC VAC ID C1 NC UI VCC RA 3 BR pin voltage R9 5 BR GND S/OCP D /ST 1 VCC pin voltage VCC(ON) V CC(OFF) RB 7 C10 Drain current, I D RC Figure 10. Brown-In and Brown-Out function controlled by AC line detection STR-W6000S-AN, Rev. 1.0 V BR(OUT)= 4.8 V V BR(DIS)= 0.48 V C4 ROCP VBR(IN)= 5.6 V SANKEN ELECTRIC CO., LTD. 68 ms 12 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. Variance resulting from propagation delay Lo w AC in p ut A gh Hi np Ci VOCP(ONTime) (V) = VOCP(L)(V) + DPC (mV/μs) × On Time (μs). ut VOCP(L) is the OCP threshold voltage at zero duty cycle (V), 0.78 V DPC is the OCP compensation coefficient (mV/μs), 18 mV/μs, and On Time is the the on-time of the duty cycle (μs): On Time = On Duty / fOSC(AVG) 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. 265 VAC (as an example) 1.0 85VAC (as an example) VOCP(H) About 0.82 VOCP(L) 0.5 0 0 Output Current , IOUT（A) Figure 11. Output current at OCP without input compensation STR-W6000S-AN, Rev. 1.0 (3) where: VOCP(ONTime) , Typical (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. 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) = 0.88 V, constantly 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 OVP 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 OVP state. This operation reduces power stress on the power MOSFET and secondary-side rectifier diode. 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. 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 VCC 4 FB /OLP GND 6 5 I FB 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 flowing to the 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 intermittent operation by UVLO is repeated in the same way as described in the Overvoltage Protection Function (OVP) section. When the fault condition is removed, the IC returns to normal operation automatically. STR-W6000S-AN, Rev. 1.0 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 SANKEN ELECTRIC CO., LTD. 14 Thermal Shutdown Function (TSD) C1 U1 1 3 4 5 6 7 C4 RA RB C3 D2 R2 C2 C10 ROCP Apply proper design margin to accommodate ripple current, voltage, and temperature rise. P D1 Peripheral Components Take care to use the proper rating and proper type of components. • Input and output electrolytic capacitors C5 R1 S/ OCP V CC GND FB/OLP BR Design Notes T1 BR1 VAC D/ST 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. When the TSD function is activated, the Bias Assist function is disabled and the intermittent operation by UVLO is repeated in the same way as described in the Overvoltage Protection Function (OVP) section. If the factor causing the overheating condition is removed, and the temperature of the Control Part decreases to Tj(TSD), the IC returns to normal operation automatically. D RC PC1 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 in figure 15 , a high inductance resistor may cause poor operation. 4 VCC • BR pin peripheral circuit UI 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. R2 Added D C2 GND 5 • FB/OLP 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, C3 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. Figure 16. VCC pin peripheral circuit VCC pin voltage Without R2 With R2 Output Current, I OUT Figure 17. VCC versus IOUT with and without resistor R2 For alleviating C2 peak charging, it is effective to add some STR-W6000S-AN, Rev. 1.0 SANKEN ELECTRIC CO., LTD. 15 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 L51 D51 T1 VOUT A typical phase compensation circuit with a secondary-side shunt regulator (U51) is shown in figure 18. The reference value of C52 for phase compensation is about 0.047 to 0.47 μF, and should be adjusted based on actual operation in the application. 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-W6000S-AN, Rev. 1.0 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 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 for the IC peripheral circuit and secondary-side rectifier-smoothing circuit. • 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 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 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 T11 C5 R1 C1 P D1 C51 S RA D/ST S/ OCP V CC GND FB/OLP BR U1 1 3 4 5 6 7 D2 R2 C2 C10 C4 ROCP RB C3 Main power circuit trace GND trace for the IC D RC PC1 C9 Figure 21. Peripheral circuit example around the IC STR-W6000S-AN, Rev. 1.0 SANKEN ELECTRIC CO., LTD. 17 Power Supply Specification Reference Design of Power Supply As an example, the following show a power supply specification, circuit schematic, bill of materials, and transformer specification. VAC IC STR-W6053S Input Voltage 85 to 265 VAC Maximum Output Power 56 W (70.4 WPEAK) Output Voltage / Current 8 V / 2.5 A, 12 V / 3 A (4.2 APEAK) F1 L1 BR1 C1 T1 C2 D52 12 V/4.2A TH 1 C4 C3 t° R1 P1 S1 C55 R57 C56 D1 C57 S2 P2 GND L51 D51 8V/2.5A S/ OCP GND FB/OLP BR 1 3 4 5 6 7 R54 C51 R4 V CC D/ST STR-W6053S R51 PC1 R55 R5 C5 D2 S3 R3 R52 C53 C7 R2 PC1 C8 R6 C6 C54 C52 R53 U51 D R56 GND C9 Figure 22. Circuit schematic Bill of Materials Symbol Part type Ratingsa F1 Recommended Sanken Parts Symbol Part type Ratingsa Photo-coupler PC123 or equiv. Recommended Sanken Parts Fuse 250 VAC, 6 A PC1 L1b CM inductor 2.2 mH U1 IC TH1b NTC thermistor Short T1 Transformer See the specification BR1 General 600 V, 6 A L51 Inductor 5 μH D1 Fast recovery 1000 V, 0.5 A EG01C D51 Schottky 100 V, 10 A FMEN-210A D2 Fast recovery 200 V, 1 A AL01Z D52 Fast recovery 150 V, 10 A FMEN-210B C1b Film, X2 0.1 μF, 275 V C51b Ceramic 470 pF, 1 kV C2b Film, X2 0.1 μF, 275 V C52 Electrolytic 1000 μF, 16 V C3 Electrolytic 220 μF, 400 V C53b Ceramic 0.15 μF, 50 V C4 Ceramic 3300 pF, 2 kV C54 Electrolytic 1000 μF, 16 V C5 Ceramic Open C55 Ceramic 470 pF, 1 kV C6 Electrolytic 22 μF, 50 V C56 Electrolytic 1500 μF, 25 V C7b Ceramic 0.01 μF C57 Electrolytic 1500 μF, 25 V STR-W6053S C8b Ceramic 1000 pF R51 General 1.5 kΩ C9 Ceramic, Y1 2200 pF, 250 V R52 General 1 kΩ R1c Metal oxide 56 kΩ, 2 W R53b General 33 kΩ R2 General 0.27 Ω, 1 W R54b General, 1% 3.9 kΩ R3 General 5.6 Ω R55 General, 1% 22 kΩ R4c General 2.2 MΩ R56 General, 1% 6.8 kΩ R5c General 2.2 MΩ R57 General Open R6 General 330 kΩ U51 Shunt regulator VREF = 2.5 V TL431 or equiv. 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. is necessary to be adjusted based on actual operation in the application. cResistors 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. bIt STR-W6000S-AN, Rev. 1.0 SANKEN ELECTRIC CO., LTD. 18 Transformer specification ▫ Primary inductance, LP : 315 μH ▫ Core size: EER28L ▫ AL-value: 163 nH/N2 (Center gap of about 0.8 mm) ▫ Winding specification Location Symbol Number of Turns (T) Wire (mm) Configuration Primary winding P1 26 TEX-Ø0.35×2 1.5 layers, solenoid winding Primary winding P2 18 TEX-Ø0.35×2 Solenoid winding Auxiliary winding D 10 TEX-Ø0.23×2 Space winding Output winding 1 S1 7 Ø0.4×4 Space winding Output winding 2 S2 7 Ø0.4×4 Space winding Output winding 3 S3 5 Ø0.4×4 Space winding VDC P1 S2 D S3 S1 P2 Bobbin Cross-section view STR-W6000S-AN, Rev. 1.0 P1 P2 12V S1 GND D/ST S2 VCC D GND 8V S3 GND ٨ mark shows the start point of winding SANKEN ELECTRIC CO., LTD. 19 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-W6000S-AN, Rev. 1.0 SANKEN ELECTRIC CO., LTD. 20