CN202142841U

CN202142841U - Switch power supply output short circuit protective circuit

Info

Publication number: CN202142841U
Application number: CN201120218348U
Authority: CN
Inventors: 徐成宪
Original assignee: GUANGZHOU KINGPAN INDUSTRIAL Co Ltd
Current assignee: GUANGZHOU KINGPAN INDUSTRIAL Co Ltd
Priority date: 2011-06-24
Filing date: 2011-06-24
Publication date: 2012-02-08
Anticipated expiration: 2021-06-24

Abstract

Provided is a switch power supply output short circuit protective circuit, comprising a starting up delay circuit 100, an output voltage detecting circuit 101, a protecting voltage threshold setting circuit 102, and a control signal time-delay circuit 103. The switch power supply output short circuit protective circuit detects the output voltage by utilizing the characteristic that the voltage instantly falls to 0V when the switch power supply is short circuited, and then outputs a control signal to a power supply management chip, thus to achieve the protective effect by stopping the work of the complete switch power supply. The switch power supply output short circuit protective circuit achieves the protective function by stopping the working of the complete power supply, thereby ensuring the security of the protective function.

Description

A kind of Switching Power Supply output short circuit protection circuit

Technical field

The utility model relates to field of switch power, relates in particular to the Switching Power Supply charger.

Background technology

The application of Switching Power Supply at present more and more widely in the defencive function of Switching Power Supply, generally all needs output short circuit protection, to prevent the Switching Power Supply excessive damage Switching Power Supply of operating current and load when the output short-circuit.And the quality of output short circuit protection performance directly affects the reliability of whole Switching Power Supply.

At present, the short-circuit protection circuit in the Switching Power Supply mostly adopts the inner current peak restricting circuits of pulse width modulating chip to detect the operating current on the former limit of transformer, limits the function that its peak value reaches short-circuit protection.Since this current peak that just limits major loop, frequent always protection and recovery under short-circuit condition, the operating current of major loop is still very big, and it is high to exist Switching Power Supply short circuit output residual voltage, and loss is big, the problem that reliability is low.

Also having the short-circuit protection circuit of part Switching Power Supply is general detection output current, when detect output current when excessive the shutdown switch power work reach the function of protection.The sampling resistor because this detection mode need be connected on output loop along with the increase of Switching Power Supply output-current rating, requires to adopt the sampling resistor of more high-power and littler resistance, and this also makes the volume of short-circuit protection circuit and cost increase.

The utility model content

To above-mentioned the problems of the prior art and shortcoming; This novel practical has proposed a kind of Switching Power Supply short-circuit protection circuit; The operating current and the loss of Switching Power Supply during with the reduction short-circuit protection; Improve the reliability of power supply, and can not increase because of the increase volume and the cost of Switching Power Supply rated current.

The technical scheme of this novel practical is following: a kind of Switching Power Supply short-circuit protection circuit comprises that start delay circuit 100, output voltage detecting circuit 101, protection voltage threshold are provided with circuit 102, control signal delay circuit 103; Wherein:

Start delay circuit 100, Switching Power Supply award the time of output capacitance charging when opening, this time is by the capacity (this capacity is this power supply output capacitance capacity and load input capacitance capacity sum) and the output voltage decision of output capacitance;

The protection voltage threshold is provided with circuit 102, is used to be provided with the short-circuit protection threshold voltage, and this voltage is generally 10%～20% of output voltage;

Output voltage detecting circuit 101, whether be used to detect output voltage has the phenomenon that is lower than the short-circuit protection threshold voltage;

Control signal delay circuit 103 resembles now when output voltage detecting circuit 101 detects short circuit, and described control signal delay circuit 103 can produce delay time, if power supply output breaks away from short-circuit condition, then Switching Power Supply operate as normal in the delay time; If power supply output is in short-circuit condition in the delay time always, control signal delay circuit 103 will send the short-circuit protection signal to Switching Power Supply managing chip off switch power supply.This delay circuit is mainly used in the antijamming capability that strengthens this protective circuit.

The short-circuit protection signal can be used to draw high the pressure feedback port of power management chip, the shutdown switch power work.

The beneficial effect of the utility model patent is:

1, adopts the device that the utility model provided; Carrying out short-circuit protection scheme with the inner current peak restricting circuits of employing pulse width modulating chip that background technology is mentioned compares; Owing to adopt the mode of time-delay and shutdown switch power work; The operating current of Switching Power Supply and loss when having reduced short-circuit protection have effectively improved the reliability of Switching Power Supply.

2, the mode that the employing of mentioning with background technology detects output current is carried out short-circuit protection scheme and is compared, because this circuit only used divider resistance and sampled, makes this circuit can not receive the increase of power supply output-current rating and volume and cost increase.

Description of drawings

Accompanying drawing 1 is the theory diagram of the utility model;

Accompanying drawing 2 is the circuit theory diagrams of the utility model.

Embodiment

Operation principle below in conjunction with Fig. 1,2 pairs of the utility model patents is described further:

Form start delay circuit 100 by R8～R12, Q1, U1B, C2 among Fig. 2, U1B the 7th pin can output low level be pulled to low level through R8 and Q1 with U1A the 1st pin when Switching Power Supply is started shooting; VCC slowly charges to C2 through R11 simultaneously; When C2 is charged to voltage and is higher than the voltage (being U1B the 6th pin voltage) that R9 and R10 dividing potential drop come out; U1B the 7th pin output high level turn-offs Q1 is no longer dragged down U1A the 1st pin voltage by force; The effect of start delay circuit leaves it at that, and will decide the time of delay of this circuit according to the duration of short circuit that the charging interval and the Switching Power Supply of Switching Power Supply output capacitance (comprising the output capacitance of this power supply and the input capacitance of load) can be born, and the time has lacked very much power supply and can't start; Oversize may bring infringement to power supply and load, the time is set between 0.5S～1S usually;

Form the protection voltage threshold by R4～R7 among Fig. 2 circuit 102 is set; Divide an extrusion reference voltage (being U1A the 2nd pin voltage) by R4 and R5; The protection threshold voltage that R6 and R7 convert out according to switch power source output voltage again (be generally output voltage 10%～20%) is confirmed sampled voltage (being U1A the 3rd pin voltage) with the reference voltage of U1A the 2nd pin; When U1A the 3rd pin sampled voltage is lower than the reference voltage of U1A the 2nd pin; U1A the 1st pin is exported high level at once; High level reaches the Switching Power Supply managing chip through the circuit that D1, R3, R2, U2, D3, R1, Q2 form with signal again, through the mode that Switching Power Supply managing chip pressure feedback port level is drawn high Switching Power Supply is closed again;

The voltage detecting circuit of forming by R6, R7 among Fig. 2 101; R6 one end is directly received switch power source output voltage, and when short circuit phenomenon took place, detecting voltage can fall to 0V moment; (antijamming capability of the long more Switching Power Supply of control signal delay time is strong more for the control signal delay circuit of being made up of C1, R6, R7 among Fig. 2 103; But must in the duration of short circuit scope that Switching Power Supply can be born, exceed and brought infringement may for power supply and load, the time is set between 200ms～500ms usually); Slowly discharge; When being discharged to U1A the 3rd pin voltage and being lower than U1A the 2nd pin voltage, U1A the 1st pin can be exported high level, and the circuit of forming through D1, R3, R2, U2, D3, R1, Q2 again reaches the Switching Power Supply managing chip with signal Switching Power Supply is closed.

The Switching Power Supply output short circuit protection circuit that the utility model provided can be widely used in all kinds of switching power units, when particularly requiring power supply short circuit loss little, reliability is high and in the high occasion of small product size and cost requirement.

Above-described the utility model execution mode does not constitute the qualification to the utility model protection range.The modification of being done within any spirit and principle at the utility model, be equal to replacement and improvement etc., all should be included within the claim protection range of the utility model.

Claims

1. a protective circuit that is used for the Switching Power Supply output short-circuit is characterized in that: comprise that start delay circuit (100), output voltage detecting circuit (101), protection voltage threshold are provided with circuit (102) and control signal delay circuit (103);

Said start delay circuit (100) is used for awarding the time that output capacitance is charged when Switching Power Supply is opened;

Described protection voltage threshold is provided with circuit (102), is used to be provided with the short-circuit protection threshold voltage;

Described output voltage detecting circuit (101), whether be used to detect output voltage has the phenomenon that is lower than the short-circuit protection threshold voltage;

Described control signal delay circuit (103); When output voltage detecting circuit (101) when detecting short circuit phenomenon; Described control signal delay circuit (103) can produce delay time, if power supply output breaks away from short-circuit condition, then Switching Power Supply operate as normal in the delay time; If power supply output is in short-circuit condition in the delay time always, control signal delay circuit (103) will send the short-circuit protection signal to Switching Power Supply managing chip off switch power supply; This delay circuit is mainly used in the antijamming capability that strengthens this protective circuit.

2. the protective circuit that is used for the Switching Power Supply output short-circuit as claimed in claim 1 is characterized in that: start delay circuit (100) time is set between 0.5S～1S.

3. the protective circuit that is used for the Switching Power Supply output short-circuit as claimed in claim 1 is characterized in that: control signal delay circuit (103) time is set between 200ms～500ms.