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TOP254PN Datasheet(PDF) 21 Page - Power Integrations, Inc. |
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TOP254PN Datasheet(HTML) 21 Page - Power Integrations, Inc. |
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21 / 48 page 
Rev. F 01/09 21 TOP252-262 www.powerint.com Application Examples A High Efficiency, 35 W, Dual Output - Universal Input Power Supply The circuit in Figure 41 takes advantage of several of the TOPSwitch-HX features to reduce system cost and power supply size and to improve efficiency. This design delivers 35 W total continuous output power from a 90 VAC to 265 VAC input at an ambient of 50 ºC in an open frame configuration. A nominal efficiency of 84% at full load is achieved using TOP258P. With a DIP-8 package, this design provides 35 W continuous output power using only the copper area on the circuit board underneath the part as a heat sink. The different operating modes of the TOPSwitch-HX provide significant improvement in the no-load, standby, and light load performance of the power supply as compared to the previous generations of the TOPSwitch. Resistors R3 and R4 provide line sensing, setting line UV at 100 VDC and line OV at 450 VDC. Diode D5, together with resistors R6, R7, capacitor C6 and TVS VR1, forms a clamp network that limits the drain voltage of the TOPSwitch after the integrated MOSFET turns off. TVS VR1 provides a defined maximum clamp voltage and typically only conducts during fault conditions such as overload. This allows the RCD clamp (R6, R7, C6 and D5) to be sized for normal operation, thereby maximizing efficiency at light load. Should the feedback circuit fail, the output of the power supply may exceed regulation limits. This increased voltage at output will also result in an increased voltage at the output of the bias winding. Zener VR2 will break down and current will flow into the “M” pin of the TOPSwitch initiating a hysteretic overvoltage protection with automatic restart attempts. Resistor R5 will limit the current into the M pin to < 336 μA, thus setting hysteretic OVP. If latching OVP is desired, the value of R5 can be reduced to 20 Ω. The output voltage is controlled using the amplifier TL431. Diode D9, capacitor C20 and resistor R16 form the soft finish circuit. At startup, capacitor C20 is discharged. As the output voltage starts rising, current flows through the optocoupler diode inside U2A, resistor R13 and diode D9 to charge capacitor C20. This provides feedback to the circuit on the primary side. The current in the optocoupler diode U2A gradually decreases as the capacitor C20 becomes charged and the control amplifier IC U3 becomes operational. This ensures that the output voltage increases gradually and settles to the final value without any overshoot. Resistor R16 ensures that the capacitor C20 is maintained charged at all times after startup, which effectively isolates C20 from the feedback circuit after startup. Capacitor C20 discharges through R16 when the supply shuts down. Resistors R20, R21 and R18 form a voltage divider network. The output of this divider network is primarily dependent on the divider circuit formed using R20 and R21 and will vary to some extent for changes in voltage at the 15 V output due to the connection of resistor R18 to the output of the divider network. Resistor R19 and Zener VR3 improve cross regulation in case only the 5 V output is loaded, which results in the 15 V output operating at the higher end of the specification. Figure 41. 35 W Dual Output Power Supply using TOP258PN. D S C M CONTROL PI-4747-020508 R11 33 R12 33 R3 2.0 M R16 10 k R17 10 k R21 10 k 1% R18 196 k 1% R19 10 R14 22 R13 330 R15 1 k R20 12.4 k 1% D9 1N4148 U3 TL431 2% VR3 BZX55B8V2 8.2 V 2% R7 20 1/2 W VR2 1N5250B 20 V VR1 P6KE200A D5 FR106 R4 2.0 M R5 5.1 k R1 1 M R2 1 M R8 6.8 R10 4.7 R6 22 k 2 W U2B PS2501- 1-H-A U2A PS2501- 1-H-A L2 3.3 H L1 6.8 mH L3 3.3 H U1 TOP258PN C9 47 F 16 V C20 10 F 50 V C21 220 nF 50 V C19 1.0 F 50 V C10 10 F 50 V C11 2.2 nF 250 VAC D6 FR106 D8 SB530 D7 SB560 C8 100 nF 50 V D1 1N4937 D2 1N4007 D3 1N4937 D4 1N4007 C13 680 F 25 V C14 680 F 25 V C15 220 F 25 V C18 220 F 10 V C17 2200 F 10 V C12 470 pF 100 V C16 470 pF 100 V 2 T1 EER28 7 11 9 3 6 5 4 C4 100 F 400 V C6 3.9 nF 1 kV C7 2.2 nF 250 VAC C3 220 nF 275 VAC RT1 10 F1 3.15 A TOPSwitch-HX L E N +12 V, 2 A RTN +5 V, 2.2 A RTN t O 90 - 265 VAC |
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