CN2687922Y - Circuit for limiting input power at output end overcurrent for switching power supply - Google Patents
Circuit for limiting input power at output end overcurrent for switching power supply Download PDFInfo
- Publication number
- CN2687922Y CN2687922Y CN 200420019428 CN200420019428U CN2687922Y CN 2687922 Y CN2687922 Y CN 2687922Y CN 200420019428 CN200420019428 CN 200420019428 CN 200420019428 U CN200420019428 U CN 200420019428U CN 2687922 Y CN2687922 Y CN 2687922Y
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- power supply
- vcc
- circuit
- power
- control chip
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Abstract
The utility model relates to a circuit for limiting input power at output end overcurrent for switching power supply. The utility model is composed of a power source input terminal, a power supply output terminal, a transformer T1, a control chip N1, an input port switching tube V7, a grid drive resistor R5 of the switching tube V7, a charging circuit of the power supply control chip VCC and a VCC power circuit. The charging circuit of the power supply control chip VCC feet is made up by two resistors R1 and R2, a capacitor C1, a regulator tube V1, an NPN three-electrode tube V2 and a diode V3. The VCC power circuit is composed of a VCC current supply winding portion of the transformer and the C2. The utility model is characterized in that the charging circuit and the power circuit are provided with a keying circuit composed of a regulator tube V6, an NPN three-electrode tube V5, a capacitor C4 and two resistors R3 and R4. The VCC power circuit is provided with a diode V4 and a capacitor C3. The V5 collector of the keying circuit is connected with the base electrode of the VCC charging circuit. The V4 anode of the power circuit is connected with the V6 cathode of the keying circuit. The utility model has the advantage that the input power can be nicely restricted when the overcurrent of the output terminal of the switch power supply happens. The charging time of the control chip is prolonged when the overcurrent of the output terminal hapens. The utility model reduces the input power of the power supply and improves the reliability of the switch power supply when the overcurrent of the output terminal happens.
Description
Technical field
The circuit of restriction input power can be used for the Switching Power Supply that output has the overcurrent protection needs when the utility model related to a kind of Switching Power Supply output overcurrent, belonged to the switching power circuit technical field.
Background technology
At present, restriction input power circuit during the output overcurrent that on Switching Power Supply, uses, as shown in Figure 1, in Fig. 1, two resistance R 1, R2, capacitor C 1, a voltage-stabiliser tube V1, NPN triode V2, a diode V3 constitute the VCC pin of power supply control chip, some chip is referred to as the VDD pin, charging circuit.In field of switch power when the output overcurrent; no matter common current foldback circuit is sampling input current or sampling output current; usually all the current signal that samples is transported to the overcurrent protection pin of power supply control chip; the output pin of power supply control chip turn-offs the input switch pipe when current signal surpasses the overcurrent thresholding of control chip, thereby limits input power when the output overcurrent.Though this output overcurrent protection mode can play the effect of restriction input power generally speaking; but because the charging circuit of the VCC pin of power supply control chip is not locked; have no progeny in input switch pipe pass; though having to a certain degree, reduces VCC; but be easy to regard to being recharged be increased to again the turning-on voltage of power supply control chip; the result who causes like this is that control chip is easy to restart and drives the conducting once more of input switch pipe when the output overcurrent; so that the input power of limit switch power supply has influenced the reliability of Switching Power Supply when the output overcurrent to a certain extent well.
Summary of the invention
The purpose of this utility model is that invention a kind ofly can limit input power well when Switching Power Supply output overcurrent, and the circuit of restriction input power when improving the Switching Power Supply output overcurrent of the reliability of Switching Power Supply when the output overcurrent.
For realizing above purpose, the circuit of restriction input power when the technical solution of the utility model provides a kind of Switching Power Supply output overcurrent, by power input, power output end, transformer T1, control chip N1, input end switch pipe V7, the gate driving resistance R 5 of switching tube V7, the charging circuit of power supply control chip VCC pin, the VCC power supply circuits are formed, the charging circuit of described power supply control chip VCC pin is by two resistance R 1, R2, a capacitor C 1, a voltage-stabiliser tube V1, a NPN triode V2, a diode V3 constitutes, the described switching circuit of locking action that the VCC charging circuit is risen is by a voltage-stabiliser tube V6, a NPN triode V5, a capacitor C 4 and two resistance R 3, R4 constitutes, it is characterized in that, between charging circuit and power supply circuits, be equipped with one by a voltage-stabiliser tube V6, a NPN triode V5, a capacitor C 4 and two resistance R 3, the switching circuit that R4 constitutes; Be equipped with a diode V4 and a capacitor C 3 on the VCC power supply circuits, the collector electrode of the V5 of switching circuit connects the base stage of VCC charging circuit V2, and the anode of the V4 of power supply circuits connects the negative electrode of switching circuit V6.
Draw the input signal of a level signal VCC ' from the voltage VCC of control chip as switching circuit, V4 plays reverse partition effect between VCC and VCC ', C3 works to stablize VCC ', removes to control the charging circuit of VCC then with the output of this switching circuit; And in this switching circuit, the threshold voltage that a voltage descends as VCC ' is set by voltage-stabiliser tube V6, and the VCC voltage as 1/2 has only as VCC ' to drop to threshold voltage when following, and switching circuit just allows charging circuit that VCC is charged.Control chip turn-offs the input switch pipe because of detected current sampling signal surpasses the overcurrent thresholding when the output overcurrent, VCC ' voltage begins to descend owing to the input switch pipe turn-offs, VCC voltage also descends thereupon, thereby VCC voltage descends and makes the control chip shutoff thoroughly turn-off the input switch pipe, VCC ' voltage then further descends, because VCC ' voltage is not also reduced to below the threshold voltage, so switching circuit still locks the VCC charging circuit and makes it and can not charge to VCC, have only when VCC ' voltage and drop to when making below the threshold voltage that switching circuit is eliminated locking, the VCC charging circuit just begins VCC is charged, thereby the start-up time of power supply control chip when having prolonged the output overcurrent, the startup frequency of power supply control chip when having reduced the output overcurrent, input power when therefore having limited the output overcurrent better, and played the purpose that when the output overcurrent, improves power supply reliability.
The utility model has the advantages that when Switching Power Supply output overcurrent and can limit input power well, when the output overcurrent, prolong the charging interval of control chip, reduce the input power of power supply, improve the reliability of Switching Power Supply when the output overcurrent.
Description of drawings
Fig. 1 is present Switching Power Supply limits input power when the output overcurrent circuit theory diagrams;
Fig. 2 is circuit theory diagrams of the present utility model.
Embodiment
The utility model is described in further detail below in conjunction with drawings and Examples.
Embodiment
As shown in Figure 2, be circuit theory diagrams of the present utility model, the switching circuit that plays locking action by the charging circuit of the gate driving resistance R 5 of power input, power output end, transformer T1, control chip N1, input end switch pipe V7, switching tube V7, power supply control chip VCC pin, VCC power supply circuits, to the VCC charging circuit is formed.Wherein the charging circuit of power supply control chip VCC pin is made of two resistance R 1, R2, capacitor C 1, a voltage-stabiliser tube V1, NPN triode V2, a diode V3, the switching circuit that the VCC charging circuit is played locking action is made of a voltage-stabiliser tube V6, a NPN triode V5, a capacitor C 4 and two resistance R 3, R4, the VCC power supply circuits then are to have increased a diode V4 and a capacitor C 4 on common VCC power supply circuits basis, V4 plays reverse partition effect between VCC and VCC ', C3 works to stablize VCC '.
Tell a signal VCC ' control switch circuit from VCC voltage, the base stage that switching circuit is linked V2 by the collector electrode of V5 controls the charging process of charging circuit.When the output overcurrent of Switching Power Supply, it is that the CS of control chip is a current sensor induction by current pin that current sampling signal is input to N1, when current signal surpasses the overcurrent thresholding, N1 is that to make V7 be that switching tube turn-offs to the OUTPUT pin of control chip, VCC voltage begins to descend, be that VCC ' voltage begins to descend, when VCC ' voltage is not reduced to setting voltage, switching circuit still locks charging circuit makes VCC to charge, can only continue to descend, N1 is that control chip quits work because of the decline of VCC voltage and then make V7 is that switching tube continues to keep off state; When VCC ' voltage was reduced to setting voltage, switching circuit was eliminated the lock-out state to charging circuit, and charging circuit begins the charging to VCC, and VCC voltage begins to rise.The result that VCC ' signal cooperates with switching circuit is exactly that charging circuit can't charge to VCC when VCC voltage does not drop to setting voltage, thereby start-up time of control chip when having prolonged the output overcurrent, the startup frequency of control chip when having reduced the output overcurrent, input power when therefore having limited the output overcurrent better, and played the purpose that when the output overcurrent, improves power supply reliability.
Claims (1)
1. the circuit of Switching Power Supply output overcurrent time restriction input power, by power input, power output end, transformer T1, control chip N1, input end switch pipe V7, the gate driving resistance R 5 of switching tube V7, the charging circuit of power supply control chip VCC pin, the VCC power supply circuits are formed, the charging circuit of described power supply control chip VCC pin is by two resistance R 1, R2, a capacitor C 1, a voltage-stabiliser tube V1, a NPN triode V2, a diode V3 constitutes, described VCC power supply circuits are made of the VCC power supply winding part and the C2 of transformer, it is characterized in that, between charging circuit and power supply circuits, be equipped with one by a voltage-stabiliser tube V6, a NPN triode V5, a capacitor C 4 and two resistance R 3, the switching circuit that R4 constitutes; Be equipped with a diode V4 and a capacitor C 3 on the VCC power supply circuits, the collector electrode of the V5 of switching circuit connects the base stage of VCC charging circuit V2, and the anode of the V4 of power supply circuits connects the negative electrode of switching circuit V6.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200420019428 CN2687922Y (en) | 2004-01-13 | 2004-01-13 | Circuit for limiting input power at output end overcurrent for switching power supply |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200420019428 CN2687922Y (en) | 2004-01-13 | 2004-01-13 | Circuit for limiting input power at output end overcurrent for switching power supply |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN2687922Y true CN2687922Y (en) | 2005-03-23 |
Family
ID=34669138
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 200420019428 Expired - Lifetime CN2687922Y (en) | 2004-01-13 | 2004-01-13 | Circuit for limiting input power at output end overcurrent for switching power supply |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN2687922Y (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101826293B (en) * | 2005-12-20 | 2011-10-12 | 统宝香港控股有限公司 | Circuit device |
| US9614451B2 (en) | 2015-03-19 | 2017-04-04 | Pegatron Corporation | Starting an isolated power supply with regulated control power and an internal load |
-
2004
- 2004-01-13 CN CN 200420019428 patent/CN2687922Y/en not_active Expired - Lifetime
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101826293B (en) * | 2005-12-20 | 2011-10-12 | 统宝香港控股有限公司 | Circuit device |
| US9614451B2 (en) | 2015-03-19 | 2017-04-04 | Pegatron Corporation | Starting an isolated power supply with regulated control power and an internal load |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CX01 | Expiry of patent term | ||
| CX01 | Expiry of patent term |
Expiration termination date: 20140113 Granted publication date: 20050323 |