CN207652017U - A kind of input undervoltage power-down protection circuit - Google Patents
A kind of input undervoltage power-down protection circuit Download PDFInfo
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- CN207652017U CN207652017U CN201721804659.8U CN201721804659U CN207652017U CN 207652017 U CN207652017 U CN 207652017U CN 201721804659 U CN201721804659 U CN 201721804659U CN 207652017 U CN207652017 U CN 207652017U
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Abstract
A kind of input undervoltage power-down protection circuit, including the first sample circuit, the first comparison circuit, hysteresis circuit, control circuit further include the second sample circuit, the second comparison circuit and the second diode；The input voltage of first sampling circuit samples Switching Power Supply simultaneously exports the first sampled signal；First comparison circuit receives the first sampled signal and exports first control signal；Control circuit receives first control signal and exports the working condition of control power supply；Hysteresis circuit receives first control signal and is linked into generation return difference value in the first sample circuit；The input voltage of second sampling circuit samples Switching Power Supply simultaneously exports the second sampled signal；Second comparison circuit receives the second sampled signal and exports second control signal；Control circuit receives second control signal and exports the working condition of control power supply.The utility model realizes that circuit is reliable under high temperature environment, steadily works, and can quickly detect power down and be protected, reduce the production cost of circuit, simplify circuit.
Description
Technical field
The utility model is related to field of switch power, more particularly to a kind of for realizing Switching Power Supply in switch power supply system
The circuit of input undervoltage power-down protection.
Background technology
In current Switching Power Supply product, input undervoltage protection is a kind of essential safeguard measure.For input voltage
Wider range or the larger application scenario of input voltage fluctuation, the input undervoltage defencive function of Switching Power Supply can effectively avoid
When input voltage is too low, causes input current excessive and damage product, meanwhile, it also can avoid Switching Power Supply and be in abnormal work shape
State and influence its load equipment, particularly, when inputting power down, power-supply device needs the data that keep the scene intact, this is also particularly important.
Under-voltage protecting circuit is as shown in Figure 1, circuit includes in the prior art：Sample circuit, comparison circuit, hysteresis circuit,
Control circuit；The input voltage of sampling circuit samples Switching Power Supply simultaneously exports sampled signal to comparison circuit；Comparison circuit receives
Sampled signal and export control signal to control circuit carry out control and hysteresis circuit generate return difference；When input voltage generation is under-voltage
When, control circuit controls the Vcc pin levels for dragging down Switching Power Supply IC, when the Vcc pin levels that Switching Power Supply controls IC are less than
When Switching Power Supply controls the operating voltage range of IC, Switching Power Supply controls IC drivings and stops, and product enters under-voltage protection；Same time lag
Telegram in reply road drags down sampled signal to generate the hysteresis voltage Δ V of under-voltage protection；When the under-voltage recovery of input voltage, control circuit
Stop dragging down the Vcc pin levels of Switching Power Supply control IC, Switching Power Supply controls the Vcc pin levels of IC by external start-up circuit
The operating voltage range of Switching Power Supply control IC is charged to, Switching Power Supply controls IC and restores driving, and product restores output, same to time lag
Telegram in reply road discharges sampled signal to generate the hysteresis voltage Δ V of under-voltage recovery.
Existing under-voltage protecting circuit can be good at working normally when room temperature or low temperature, but work under high temperature environment
When work, since the GS cut-in voltages of the switch metal-oxide-semiconductor TR1 in hysteresis circuit become much lower, so as to cause TR1 in high temperature
It is in the conduction state always under environment, to allow the hysteresis circuit malfunction in under-voltage protecting circuit.
And existing solution is to replace the very high metal-oxide-semiconductor of cut-in voltage, but small signaling switch metal-oxide-semiconductor in the market is very
Difficulty is matched with the very high metal-oxide-semiconductor of cut-in voltage, and only the larger metal-oxide-semiconductor of power just has higher cut-in voltage, therefore only selects
The metal-oxide-semiconductor that power is larger is taken, is possible to ensure that TR1 does not mislead under hot environment, but this will be such that input undervoltage protects
The cost of circuit greatly increases, and hysteresis circuit still has the risk of failure.
Secondly, the sample circuit of existing under-voltage protecting circuit includes a capacitance C1, one end connection sampling electricity of capacitance C1
The output end on road, due to the presence of capacitance C1 in circuit, when causing to input power down, the response speed of under-voltage protecting circuit is very slow,
Power-off signal cannot be timely feedbacked and deprotect field data to controller, eventually cause power-supply device loss of data.
Utility model content
The purpose of this utility model is to be improved existing under-voltage protecting circuit, both can guarantee circuit in high and low temperature item
Under part can reliably working while, and can timely respond input power down and feed back power-off signal deprotected to controller it is existing
Field data, moreover it is possible to which cost of implementation substantially reduces.
To achieve the above object, the utility model is achieved through the following technical solutions：
A kind of input undervoltage power-down protection circuit, including：First sample circuit, the first comparison circuit, hysteresis circuit, control
Circuit；
The input voltage of first sampling circuit samples Switching Power Supply simultaneously exports the first sampled signal to the first comparison circuit；The
One comparison circuit receives the first sampled signal and exports first control signal to control circuit and hysteresis circuit；Control circuit receives
First control signal and the working condition for exporting control power supply；Hysteresis circuit receives first control signal and is linked into the first sampling
Return difference value is generated in circuit；
It is characterized in that：Further include the second sample circuit, the second comparison circuit and the second diode；Second sample circuit
The output end of the input voltage of input terminal connecting valve power supply, the second sample circuit connects the second comparison circuit, and the second comparison is electric
The boost voltage of one end connecting valve power supply on road, the cathode of output end the second diode of connection of the second comparison circuit, second
The anode of diode is connected to control circuit.
The input voltage of second sampling circuit samples Switching Power Supply simultaneously exports the second sampled signal to the second comparison circuit；The
Two comparison circuits receive the second sampled signal and export second control signal to control circuit；Control circuit receives the second control letter
Number and export control power supply working condition and controller.
Preferably, hysteresis circuit includes first resistor, the first diode, and one end of first resistor connects the first diode
Anode, the other end of first resistor connect the output end of the first sample circuit, and the cathode of the first diode is connected to control circuit.
Preferably, the second sample circuit includes second resistance, 3rd resistor, one end connecting valve power supply of second resistance
Input voltage, the tie point of the other end connection 3rd resistor and the second comparison circuit of second resistance, the other end of 3rd resistor
Connection input ground.
Preferably, the second comparison circuit includes the 4th resistance, the first error amplifier, one end connecting valve of the 4th resistance
The boost voltage of power supply, the cathode of the other end the first error amplifier of connection of the 4th resistance, the cathode of the second diode, first
The reference foot of error amplifier connects the second sample circuit, and the anode of the first error amplifier is connected to input ground.
Due to the application of the above technical scheme, the beneficial effects of the utility model are：
(1) existing scheme high temperature failure, reliability higher are solved the problems, such as；
(2) circuit is simple, and cost is lower, easily designed；
(3) solve the problems, such as that existing scheme power down response speed is slow, it is more adaptable.
Description of the drawings
Fig. 1 is existing scheme circuit diagram；
Fig. 2 is the utility model embodiment circuit diagram.
Specifically apply a mode
The utility model is described in further detail in the following with reference to the drawings and specific embodiments：
A kind of input undervoltage power-down protection circuit, as shown in Figure 2, wherein circuit includes sample circuit 1, comparison circuit 1,
Hysteresis circuit, control circuit further include quick power-fail detection circuit.
Wherein, hysteresis circuit includes resistance R4 and diode D3；The output end of one end connection sample circuit 1 of resistance R4,
The anode of the other end connection diode D3 of resistance R4, the cathode of diode D3 connect control circuit.
Quick power-fail detection circuit includes sample circuit 2, comparison circuit 2 and diode D5；Wherein, sample circuit 2 includes
Resistance R7, resistance R8；One end of resistance R7 connects input voltage, one end of the other end connection resistance R8 of resistance R7 and more electric
Road 2, the other end connection ground of resistance R8.Wherein, comparison circuit 2 includes resistance R9 and error amplifier U2 (TL431)；Resistance R9
One end connect boost voltage VCC, cathode, the diode D5 of the other end connection error amplifier U2 (TL431) of resistance R9
Cathode, the output end of the reference foot connection comparison circuit 2 of error amplifier U2 (TL431), the sun of error amplifier U2 (TL431)
Pole is grounded, and the output of comparison circuit 2 is connected to control circuit by diode D5.
The operation principle of the present embodiment circuit：
The sampled circuit 1 of input voltage gives the reference foot ratio of the error amplifier U1 (TL431) of comparison circuit 1 after dividing
Compared with, when input voltage declines, and the reference voltage with reference to foot is less than after partial pressure, the high electricity of No. 2 foot cathodes output of U1 (TL431)
It is flat, output par, c is controlled at this time by boost voltage VCC voltage pull-downs to PWM chip undervoltage turnoff point hereinafter, under-voltage closing power supply,
And control signal is exported, while resistance R4 is parallel in sample circuit 1 by the diode D3 conductings in hysteresis circuit, to generate
One hysteresis voltage value, in case restoring next time to start to use；It is more than the reference voltage with reference to foot after input voltage rising, partial pressure
When, No. 2 foot cathodes of U1 (TL431) export a lower level, control output par, c at this time and release boost voltage Vcc voltage
It puts, the activated circuit of boost voltage Vcc voltage continues charging and rises to PWM chip startup electrical voltage point, thus startup power supply, and it is defeated
Go out and control signal, while the diode D3 cut-offs in hysteresis circuit, the resistance R4 being parallel in sample circuit 1 is disconnected, to
A hysteresis voltage value is generated, in case next undervoltage turnoff is used.
When the unexpected power down of input voltage, the sampled circuit 2 of input voltage gives the U2 of comparison circuit 2 after dividing
(TL431) reference foot is compared, and with sample circuit 1 and comparison circuit 1, different is operation principle：Compare electric
There is no filter capacitor in road 2, when input voltage power down, comparison circuit 2 can timely detect power-off signal and timely to
Go out to control signal, is used for power down protection field data.
The present embodiment is compared with available circuit technology, and reliability higher, cost is lower, under high temperature operating conditions, this reality
Apply example comparison circuit export control signal to control circuit control power supply working condition while, additionally it is possible to control introduce
The under-voltage hysteresis voltage with recovery, and using the very low small signal diode of cost, reduce into production cost, simplify electricity
Road adds quick power-fail detection circuit, can timely detect input and drop out, and provide control signal in time, is used for power down
Keep the scene intact data.
The embodiment of the utility model is without being limited thereto, according to the above of the utility model, utilizes the general of this field
Logical technological know-how and customary means, under the premise of not departing from the utility model above-mentioned basic fundamental thought, the utility model may be used also
To make the modification, replacement or change of other diversified forms, such as triode Q1 is replaced with into metal-oxide-semiconductor and all falls within the utility model
Within rights protection scope.
Claims (4)
1. a kind of input undervoltage power-down protection circuit, including：First sample circuit, the first comparison circuit, hysteresis circuit, control electricity
Road；
The input voltage of first sampling circuit samples Switching Power Supply simultaneously exports the first sampled signal to the first comparison circuit；First ratio
The first sampled signal is received compared with circuit and exports first control signal to control circuit and hysteresis circuit；Control circuit receives first
Control signal and the working condition for exporting control power supply；Hysteresis circuit receives first control signal and is linked into the first sample circuit
Middle generation return difference value；
It is characterized in that：Further include the second sample circuit, the second comparison circuit and the second diode；The input of second sample circuit
The input voltage of connecting valve power supply, the output end of the second sample circuit is held to connect the second comparison circuit, the second comparison circuit
The boost voltage of one end connecting valve power supply, the output end of the second comparison circuit connect the cathode of the second diode, the two or two pole
The anode of pipe is connected to control circuit；
The input voltage of second sampling circuit samples Switching Power Supply simultaneously exports the second sampled signal to the second comparison circuit；Second ratio
The second sampled signal is received compared with circuit and exports second control signal to control circuit；Control circuit receives second control signal simultaneously
The working condition and controller of output control power supply.
2. input undervoltage power-down protection circuit according to claim 1, it is characterised in that：Hysteresis circuit includes the first electricity
Resistance, the first diode, one end of first resistor connect the anode of the first diode, the first sampling of other end connection of first resistor
The cathode of the output end of circuit, the first diode is connected to control circuit.
3. input undervoltage power-down protection circuit according to claim 1, it is characterised in that：Second sample circuit includes second
Resistance, 3rd resistor, the input voltage of one end connecting valve power supply of second resistance, the other end connection third electricity of second resistance
The tie point of resistance and the second comparison circuit, the other end connection input ground of 3rd resistor.
4. input undervoltage power-down protection circuit according to claim 1, it is characterised in that：Second comparison circuit includes the 4th
Resistance, the first error amplifier, the boost voltage of one end connecting valve power supply of the 4th resistance, the other end connection of the 4th resistance
The reference foot of the cathode of the cathode of first error amplifier, the second diode, the first error amplifier connects the second sample circuit,
The anode of first error amplifier is connected to input ground.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201721804659.8U CN207652017U (en) | 2017-12-21 | 2017-12-21 | A kind of input undervoltage power-down protection circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201721804659.8U CN207652017U (en) | 2017-12-21 | 2017-12-21 | A kind of input undervoltage power-down protection circuit |
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| Publication Number | Publication Date |
|---|---|
| CN207652017U true CN207652017U (en) | 2018-07-24 |
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ID=62878222
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201721804659.8U Active CN207652017U (en) | 2017-12-21 | 2017-12-21 | A kind of input undervoltage power-down protection circuit |
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| CN (1) | CN207652017U (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110943429A (en) * | 2019-12-31 | 2020-03-31 | 广州金升阳科技有限公司 | Undervoltage protection circuit and control method thereof |
| CN111969852A (en) * | 2020-07-07 | 2020-11-20 | 国电南瑞科技股份有限公司 | Circuit and method for switching power supply input voltage slow-drop undervoltage protection |
-
2017
- 2017-12-21 CN CN201721804659.8U patent/CN207652017U/en active Active
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110943429A (en) * | 2019-12-31 | 2020-03-31 | 广州金升阳科技有限公司 | Undervoltage protection circuit and control method thereof |
| CN110943429B (en) * | 2019-12-31 | 2022-02-18 | 广州金升阳科技有限公司 | Undervoltage protection circuit and control method thereof |
| CN111969852A (en) * | 2020-07-07 | 2020-11-20 | 国电南瑞科技股份有限公司 | Circuit and method for switching power supply input voltage slow-drop undervoltage protection |
| CN111969852B (en) * | 2020-07-07 | 2022-01-28 | 国电南瑞科技股份有限公司 | Circuit and method for switching power supply input voltage slow-drop undervoltage protection |
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