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TOP254PN Datasheet(PDF) 22 Page - Power Integrations, Inc. |
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TOP254PN Datasheet(HTML) 22 Page - Power Integrations, Inc. |
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22 / 48 page  Rev. F 01/09 22 TOP252-262 www.powerint.com A High Efficiency, 150 W, 250 – 380 VDC Input Power Supply The circuit shown in Figure 42 delivers 150 W (19 V @ 7.7 A) at 84% efficiency using a TOP258Y from a 250 VDC to 380 VDC input. A DC input is shown, as typically at this power level a power factor correction stage would precede this supply, providing the DC input. Capacitor C1 provides local decoupling, necessary when the supply is remote from the main PFC output capacitor. The flyback topology is still usable at this power level due to the high output voltage, keeping the secondary peak currents low enough so that the output diode and capacitors are reasonably sized. In this example, the TOP258YN is at the upper limit of its power capability. Resistors R3, R6 and R7 provide output power limiting, maintaining relatively constant overload power with input voltage. Line sensing is implemented by connecting a 4 M Ω resistor from the V pin to the DC rail. Resistors R4 and R5 together form the 4 M Ω line sense resistor. If the DC input rail rises above 450 VDC, then TOPSwitch-HX will stop switching until the voltage returns to normal, preventing device damage. Due to the high primary current, a low leakage inductance transformer is essential. Therefore, a sandwich winding with a copper foil secondary was used. Even with this technique, the leakage inductance energy is beyond the power capability of a simple Zener clamp. Therefore, R1, R2 and C3 are added in parallel to VR1 and VR3, two series TVS diodes being used to reduce dissipation. During normal operation, very little power is dissipated by VR1 and VR3, the leakage energy instead being dissipated by R1 and R2. However, VR1 and VR3 are essential to limit the peak drain voltage during start-up and/or overload conditions to below the 700 V rating of the TOPSwitch-HX MOSFET. The schematic shows an additional turn-off snubber circuit consisting of R20, R21, R22, D5 and C18. This reduces turn-off losses in the TOPSwitch-HX. The secondary is rectified and smoothed by D2, D3 and C5, C6, C7 and C8. Two windings are used and rectified with separate diodes D2 and D3 to limit diode dissipation. Four capacitors are used to ensure their maximum ripple current specification is not exceeded. Inductor L1 and capacitors C15 and C16 provide switching noise filtering. Output voltage is controlled using a TL431 reference IC and R15, R16 and R17 to form a potential divider to sense the output voltage. Resistor R12 and R24 together limit the optocoupler LED current and set overall control loop DC gain. Control loop compensation is achieved using components C12, C13, C20 and R13. Diode D6, resistor R23 and capacitor C19 form a soft finish network. This feeds current into the control pin prior to output regulation, preventing output voltage overshoot and ensuring startup under low line, full load conditions. Sufficient heat sinking is required to keep the TOPSwitch-HX device below 110 °C when operating under full load, low line and maximum ambient temperature. Airflow may also be required if a large heat sink area is not acceptable. L1 D4 1N4148 C11 100 nF 50 V +19 V, 7.7 A RTN RT1 5 R19 4.7 D3 MBR20100CT R7 4.7 M D2 MBR20100CT C15-C16 820 F 25 V C14 47 pF 1 kV R20 1.5 k 2 W C10 47 F 10 V D1 BYV26C T1 EI35 11 4 13,14 5 12 1 9,10 7 R15 4.75 k 1% C20 1.0 F 50 V C17 47 pF 1 kV C9 10 F 50 V R23 15 k 0.125 W R14 22 0.5 W R3 8.06 k 1% C4 2.2 nF 250 VAC R10 6.8 C3 4.7 nF 1 kV C1 22 F 400 V R22 1.5 k 2 W D6 1N4148 R8 4.7 R1 68 k 2 W F1 4 A C18 120 pF 1 kV R16 31.6 k 1% R2 68 k 2 W VR2 1N5258B 36 V R11 1 k 0.125 W C19 10 F 50 V R12 240 0.125 W U1 TOP258YN R24 30 0.125 W C5-C8 25 V VR1, VR3 P6KE100A R18 22 0.5 W R21 2 W D5 1N4937 U2 PC817A U3 TL431 2% C12 4.7 nF 50 V R17 562 1% R13 56 k 0.125 W C13 100 nF 50 V U2 PC817B 3.3 H R4 2.0 M R5 2.0 1.5 k t O TOPSwitch-HX R6 4.7 M 820 F 250 - 380 VDC PI-4795-092007 D S C V F X CONTROL Figure 42. 150 W, 19 V Power Supply using TOP258YN. |
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