CN208571589U - Switching Power Supply is lightly loaded short-circuit protection circuit - Google Patents
Switching Power Supply is lightly loaded short-circuit protection circuit Download PDFInfo
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- CN208571589U CN208571589U CN201820815153.5U CN201820815153U CN208571589U CN 208571589 U CN208571589 U CN 208571589U CN 201820815153 U CN201820815153 U CN 201820815153U CN 208571589 U CN208571589 U CN 208571589U
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Abstract
The utility model relates to field of switch power, disclose a kind of Switching Power Supply underloading short-circuit protection circuit, the output end of 5V power supply is connected with the input terminal in anti-interference circuit, the output end in anti-interference circuit is connected with the primary side of optocoupler U1, the secondary side collector 4 of optocoupler U1 is connected with the Vref pin of UC2844 power supply control chip, the secondary collector 3 in collector 4 and pair of optocoupler U1 is also connected with the emitter of PNP type triode T1 and base stage respectively, the collector of PNP type triode T1 is connected with time delay network, time delay network is connected with the base stage of open-drain output pole triode T2 and emitter, the collector of open-drain output pole triode T2 is connected with error amplifier COMP.The utility model Switching Power Supply underloading short-circuit protection circuit goes out the logic of initial state, normal state, fault case, the error amplifier output mouth of final logic level access power supply control chip, to control PWM latch output using basic electronic component design.
Description
Technical field
The utility model relates to field of switch power, and in particular to a kind of Switching Power Supply underloading short-circuit protection circuit.
Background technique
What the short-circuit protection of Switching Power Supply product was strict, the reliability of short-circuit protection determines life of product, often
Short-circuit protection is that driving output is blocked using the electric current comparing unit of power supply control chip, enters Switching Power Supply and " beats
Belch " state, protection power device will not damage.
Tradition is applied to the mistake that Switching Power Supply short-circuit protection is voltage and power supply control chip based on primary side sampling resistor
The output voltage of poor amplifier compares, and by taking UC2844 power supply control chip as an example, if current sample pin voltage is more than 1V, can answer
Position PWM latch, driving output is closed, and after the voltage in the energization pins of UC2844 drops to 10V, Switching Power Supply stops work
Make.
It is the power supply short circuit situation of 3.3V, 5V for secondary side output winding, especially from underloading however in engineer application
To the situation of short circuit, the peak current detection for only relying on UC2844 cannot achieve short-circuit protection.Since UC2844 is based on the period
Modulation, and the inductance of different winding and leakage inductance value are different, current changing rate is inconsistent, and reflection to primary current variation is naturally not yet
Unanimously.If 5V is from underloading to when short circuit, the error amplifier of UC2844 exports high state 6.2V, by current sample comparator reverse side
For pressure stabilizing pipe wrench at 1V, positive terminal does not rise to 1V also, and PWM latch still works, and Switching Power Supply works overweight in 5V output at this time
Load state, auxiliary power supply winding voltage increases instead at this time, and Switching Power Supply continues working.If sampling resistor resistance value is turned up, and meeting
Cause Switching Power Supply less than fully loaded just overcurrent protection.
Summary of the invention
The purpose of this utility model provides a kind of Switching Power Supply underloading short-circuit protection electricity aiming at the deficiency of above-mentioned technology
Road, the logic of initial state, normal state, fault case is gone out using basic electronic component design, and final logic level accesses power supply control
The error amplifier output mouth of coremaking piece, to control PWM latch output.
To achieve the above object, the underloading of Switching Power Supply designed by the utility model short-circuit protection circuit, including 5V power supply,
Anti-interference circuit, optocoupler U1, UC2844 power supply control chip, PNP type triode T1, time delay network, open-drain output pole triode
T2 and error amplifier COMP, the output end of the 5V power supply is connected with the input terminal in the anti-interference circuit, described anti-interference
The output end in circuit is connected with the primary side of the optocoupler U1, the secondary side collector 4 of the optocoupler U1 and the UC2844 power supply control
The Vref pin of coremaking piece is connected, emitter drop-down, the secondary collector 3 in collector 4 and pair of the optocoupler U1 also respectively with
The emitter of the PNP type triode T1 is connected with base stage, will when power supply works normally state with the PNP type triode T1
Logic level negates, and the collector of the PNP type triode T1 is connected with the time delay network, and the time delay network is opened with described
The base stage of leakage output stage triode T2 is connected with emitter, and the open-drain output pole triode T2 is by logic level transition at only
It is in low level in fault case, the collector of the open-drain output pole triode T2 is connected with error amplifier COMP.
Preferably, the anti-interference circuit includes resistance R1, resistance R3 and capacitor C1, the output end of the 5V power supply and institute
The input terminal for stating resistance R1 is connected, and the output end of the resistance R1 is connected with the input terminal 1 of the optocoupler U1 primary side, the optocoupler
The output end 2 of U1 primary side is grounded, and the output end of the resistance R1 is connected with the input terminal of the resistance R3, and the resistance R1's is defeated
Outlet is connected with the input terminal of the capacitor C1, and the output end of the output end of the resistance R3 and the capacitor C1 are grounded.
Preferably, the secondary side collector 3 of the optocoupler U1 is connected with the input terminal of resistance R4, the output end of the resistance R4
It is connected with the base stage of the PNP type triode T1, the output end of the resistance R4 is also connected with the input terminal of resistance R2, the electricity
The output end of resistance R2 is connected with the emitter of the PNP type triode T1.
Preferably, the time delay network includes resistance R5, polar capacitor E1 and zener diode ZD1, when avoiding initial state
Logic level is negated, and maintains initial state logical AND normal state logic consistent, the collector and the electricity of the PNP type triode T1
The input terminal for hindering R5 is connected, and the output end of the resistance R5 is connected with the input terminal of the zener diode ZD1, the resistance R5
Output end be also connected with the anode of the polar capacitor E1, the output end of the zener diode ZD1 and the open-drain output
The base stage of pole triode T2 is connected.
Preferably, the collector of the PNP type triode T1 is connected with the input terminal of resistance R8, the output of the resistance R8
End ground connection, the cathode ground connection of the polar capacitor E1, the input terminal phase of the output end and resistance R6 of the zener diode ZD1
Even, the output end of the zener diode ZD1 is connected with the input terminal of capacitor C2, the output end ground connection of the resistance R6, described
The output end of capacitor C2 is grounded.
Preferably, the secondary side collector 3 of the optocoupler U1 is connected with the input terminal of resistance R7, the output end of the resistance R7
Ground connection.
The utility model compared with prior art, has the advantage that
1, by the way that the working condition of vice-side winding is converted into open-drain output logic level, to control the defeated of PWM latch
Out, to reach short trouble protection；
2, anti-interference circuit broadens low level effective range；
3, sampling vice-side winding state is isolated by optocoupler U1 to be protected in the former secondary side high-low pressure signal of optocoupler U1 isolation
Shield, has abandoned through current sample and has protected, it is therefore prevented that current sample pin is interfered and the possibility accidentally protected.
Detailed description of the invention
Fig. 1 is the circuit diagram that the utility model Switching Power Supply is lightly loaded short-circuit protection circuit；
Fig. 2 is the logical schematic that the utility model Switching Power Supply is lightly loaded short-circuit protection circuit.
Each part numbers are as follows in figure:
Anti-interference circuit 1, time delay network 2.
Specific embodiment
The utility model is described in further detail in the following with reference to the drawings and specific embodiments.
As shown in Figure 1, the utility model Switching Power Supply be lightly loaded short-circuit protection circuit, including 5V power supply, anti-interference circuit 1,
Optocoupler U1, UC2844 power supply control chip, PNP type triode T1, time delay network 2, open-drain output pole triode T2 and error are put
The output end of big device COMP, 5V power supply is connected with the input terminal in anti-interference circuit 1, the output end and optocoupler U1 in anti-interference circuit 1
Primary side be connected, the secondary side collector 4 of optocoupler U1 is connected with the Vref pin of UC2844 power supply control chip, the secondary side of optocoupler U1
Collector 4 is connected with the emitter of PNP type triode T1, and the secondary side collector 3 of optocoupler U1 is connected with the input terminal of resistance R4, electricity
The output end of resistance R4 is connected with the base stage of PNP type triode T1, and the output end of resistance R4 is also connected with the input terminal of resistance R2,
The output end of resistance R2 is connected with the emitter of PNP type triode T1, collector and 2 phase of time delay network of PNP type triode T1
Even, time delay network 2 is connected with the base stage of open-drain output pole triode T2 and emitter, the collector of open-drain output pole triode T2
It is connected with error amplifier COMP.
Wherein, anti-interference circuit 1 includes the defeated of output end and the resistance R1 of resistance R1, resistance R3 and capacitor C1,5V power supply
Enter end to be connected, the output end of resistance R1 is connected with the input terminal 1 of optocoupler U1 primary side, and the output end 2 of optocoupler U1 primary side is grounded, electricity
The output end of resistance R1 is connected with the input terminal of resistance R3, and the output end of resistance R1 is connected with the input terminal of capacitor C1, resistance R3's
The output end of output end and capacitor C1 are grounded；Time delay network 2 includes resistance R5, polar capacitor E1 and zener diode ZD1,
The collector of PNP type triode T1 is connected with the input terminal of resistance R5, and the output end of resistance R5 is defeated with zener diode ZD1's
Enter end to be connected, the output end of resistance R5 is also connected with the anode of polar capacitor E1, and the output end and open-drain of zener diode ZD1 is defeated
The base stage of pole triode T2 is connected out.
In addition, the collector of PNP type triode T1 is connected with the input terminal of resistance R8, and the output end ground connection of resistance R8, pole
Property capacitor E1 cathode ground connection, the output end of zener diode ZD1 is connected with the input terminal of resistance R6, zener diode ZD1's
Output end is connected with the input terminal of capacitor C2, the output end ground connection of resistance R6, the output end ground connection of capacitor C2, the pair of optocoupler U1
Side collector 3 is connected with the input terminal of resistance R7, the output end ground connection of resistance R7.
When the utility model is used, as shown in Fig. 2, it is isolated by optocoupler U1 and is sampled, is set using basic electronic component
Count out the logic of initial state, normal state, fault case, the error amplifier output of final logic level access power supply control chip
Mouthful, to control PWM latch output.
The utility model Switching Power Supply is lightly loaded short-circuit protection circuit by the way that the working condition of vice-side winding is converted into open-drain
Logic level is exported, to control the output of PWM latch, to reach short trouble protection；It is broadened by anti-interference circuit low
Level effective range；Former secondary side high-low pressure signal is isolated by optocoupler U1, by optocoupler U1 be isolated sampling vice-side winding state come
It is protected, has abandoned through current sample and protected, it is therefore prevented that current sample pin is interfered and the possibility accidentally protected.
Claims (6)
1. a kind of Switching Power Supply is lightly loaded short-circuit protection circuit, it is characterised in that: including 5V power supply, anti-interference circuit (1), optocoupler
U1, UC2844 power supply control chip, PNP type triode T1, time delay network (2), open-drain output pole triode T2 and error amplification
Device COMP, the output end of the 5V power supply are connected with the input terminal of the anti-interference circuit (1), the anti-interference circuit (1)
Output end is connected with the primary side of the optocoupler U1, the secondary side collector 4 and the UC2844 power supply control chip of the optocoupler U1
Vref pin be connected, the optocoupler U1 it is secondary while collector 4 and pair while collector 3 also respectively with the PNP type triode T1
Emitter be connected with base stage, the collector of the PNP type triode T1 is connected with the time delay network (2), the delay net
Network (2) is connected with the base stage of the open-drain output pole triode T2 and emitter, the current collection of the open-drain output pole triode T2
Pole is connected with error amplifier COMP.
2. Switching Power Supply is lightly loaded short-circuit protection circuit according to claim 1, it is characterised in that: the anti-interference circuit (1)
Including resistance R1, resistance R3 and capacitor C1, the output end of the 5V power supply is connected with the input terminal of the resistance R1, the resistance
The output end of R1 is connected with the input terminal 1 of the optocoupler U1 primary side, and the output end 2 of the optocoupler U1 primary side is grounded, the resistance
The output end of R1 is connected with the input terminal of the resistance R3, the input terminal phase of the output end of the resistance R1 and the capacitor C1
Even, the output end of the output end of the resistance R3 and the capacitor C1 are grounded.
3. Switching Power Supply is lightly loaded short-circuit protection circuit according to claim 1, it is characterised in that: the secondary side collection of the optocoupler U1
Electrode 3 is connected with the input terminal of resistance R4, and the output end of the resistance R4 is connected with the base stage of the PNP type triode T1, institute
The output end for stating resistance R4 is also connected with the input terminal of resistance R2, the output end of the resistance R2 and the PNP type triode T1
Emitter be connected.
4. Switching Power Supply is lightly loaded short-circuit protection circuit according to claim 1, it is characterised in that: time delay network (2) packet
Resistance R5, polar capacitor E1 and zener diode ZD1 are included, the collector of the PNP type triode T1 is defeated with the resistance R5's
Enter end to be connected, the output end of the resistance R5 is connected with the input terminal of the zener diode ZD1, the output end of the resistance R5
Also it is connected with the anode of the polar capacitor E1, the output end and open-drain output pole triode of the zener diode ZD1
The base stage of T2 is connected.
5. Switching Power Supply is lightly loaded short-circuit protection circuit according to claim 4, it is characterised in that: the PNP type triode T1
Collector be connected with the input terminal of resistance R8, the output end of resistance R8 ground connection, the cathode ground connection of the polar capacitor E1,
The output end of the zener diode ZD1 is connected with the input terminal of resistance R6, the output end and capacitor of the zener diode ZD1
The input terminal of C2 is connected, the output end ground connection of the resistance R6, the output end ground connection of the capacitor C2.
6. Switching Power Supply is lightly loaded short-circuit protection circuit according to claim 1, it is characterised in that: the secondary side collection of the optocoupler U1
Electrode 3 is connected with the input terminal of resistance R7, the output end ground connection of the resistance R7.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201820815153.5U CN208571589U (en) | 2018-05-29 | 2018-05-29 | Switching Power Supply is lightly loaded short-circuit protection circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201820815153.5U CN208571589U (en) | 2018-05-29 | 2018-05-29 | Switching Power Supply is lightly loaded short-circuit protection circuit |
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| Publication Number | Publication Date |
|---|---|
| CN208571589U true CN208571589U (en) | 2019-03-01 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201820815153.5U Active CN208571589U (en) | 2018-05-29 | 2018-05-29 | Switching Power Supply is lightly loaded short-circuit protection circuit |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111176152A (en) * | 2019-12-03 | 2020-05-19 | 上海辛格林纳新时达电机有限公司 | Optical coupling switching input signal source circuit |
-
2018
- 2018-05-29 CN CN201820815153.5U patent/CN208571589U/en active Active
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111176152A (en) * | 2019-12-03 | 2020-05-19 | 上海辛格林纳新时达电机有限公司 | Optical coupling switching input signal source circuit |
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