CN201550018U

CN201550018U - A DC switching power supply starting circuit

Info

Publication number: CN201550018U
Application number: CN2009200475363U
Authority: CN
Inventors: 周岩; 王柏林
Original assignee: Hohai University HHU
Current assignee: Hohai University HHU
Priority date: 2009-07-17
Filing date: 2009-07-17
Publication date: 2010-08-11
Anticipated expiration: 2019-07-17

Abstract

The utility model provides a starting circuit for a DC switching power supply, which includes a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a PNP tube Q3, a first NPN tube Q1, a second NPN tube Q2 and diode D1, the utility model not only meets the requirement of switching power supply module to provide starting working voltage for the power supply under the condition of low input voltage, but also overcomes the problem of large static power consumption of the traditional starting circuit when working at high input voltage defect. The starting circuit has the advantages of simple circuit structure, small volume, reliable performance and the like. It has practical application value for switching power supply working under the condition of wide input working voltage and low voltage starting.

Description

A kind of starting circuit for direct-current switch power supply

Technical field

The utility model relates to a kind of starting circuit for direct-current switch power supply, is specifically related to a kind of DC/DC DC power supplier start-up circuit technical field that is applicable to wide input range, low voltage starting.

Background technology

In many comparatively special applied environments, usually can run into to the power electronic equipment input voltage in situation about changing in a big way.For assurance equipment has reliable power supply output under super wide range, low voltage power supply condition, just must at first solve the design problem of power supply start-up circuit under various input voltage conditions.

The exemplary operation magnitude of voltage of the domestic and international low-tension supply control chip of announcing is 8.5V at present, because there is PN junction pressure drop (being generally 0.7V) in the PNP pipe in traditional power initiation circuit, therefore when power work (as 9V) under the low input condition, traditional start-up circuit can only provide the output voltage of 8.3V, can not guarantee the normal startup of power supply.

For some particular application, power module need be operated in super wide input voltage range, and (as 9V ~ 75V), its input voltage adaptive capacity will reach 1: 8, the design difficulty of start-up circuit is apparent simultaneously.Numerous DC/DC DC power voltage stabilizing transformers that present countries in the world are produced to its input voltage changing capability, generally can only be accomplished 1: 2, such as from 9V to 18V, and from 18V to 36V, from 36V to 75V or the like.International in recent years, domestic have report input voltage adaptive capacity to reach as high as 1: 7 (as from products such as 9V ~ 56V), but patent and circuit theory from these product issues, need be divided into 2 different zones to input voltage, in two kinds of input voltage interval ranges of height, to switch different start-up circuits, to reduce the loss of voltage-stabiliser tube current-limiting resistance.Obviously such design exists the peripheral control circuit element of circuit structure complexity, needs many, accounts for remarkable shortcomings such as the PCB circuit board space is big.There is stricter high request in high power density electric power source pair of module efficient and PCB space, and the start-up circuit that how to design in wide input voltage range just seems very important.

The utility model content

The utility model purpose

Technical problem to be solved in the utility model is the high-efficiency power start-up circuit of developing at above-mentioned the deficiencies in the prior art.Can't start under low input at wide region, low input power initiation circuit, the big shortcoming of quiescent dissipation under high input voltage the utility model proposes a kind of power initiation circuit that can work under the low input condition.Simultaneously the utility model need not the high efficiency start-up circuit that voltage-stabiliser tube is set starting resistor, be need not input voltage is divided into zones of different, with simplified design and raise the efficiency.

Technical scheme

The technical scheme that technical problem to be solved in the utility model adopted:

Starting circuit for direct-current switch power supply of the present utility model, comprise first resistance R 1, second resistance R 2, the 3rd resistance R 3, the 4th resistance R 4, the 5th resistance R 5, PNP manages Q3, the one NPN manages Q1, the 2nd NPN pipe Q2 and diode D1, wherein an end of second resistance R 2 respectively with an end of first resistance R 1, the emitter of one end of the 3rd resistance R 3 and PNP pipe Q3 connects, the other end of second resistance R 2 is managed the collector electrode of Q2 respectively with the 2nd NPN, the base stage of the other end of the 3rd resistance R 3 and PNP pipe Q3 connects, the other end of first resistance R 1 is managed the base stage of Q2 respectively with the 2nd NPN, the collector electrode of the one NPN pipe Q1 connects, the emitter of the 2nd NPN pipe Q2 is managed the emitter of Q1 respectively with a NPN, one end of the 5th resistance R 5, accessory power supply output voltage negative pole connects back ground connection when one end of capacitor C 1 and power supply operate as normal, the other end of the 5th resistance R 5 is managed the base stage of Q1 respectively with a NPN, one end of the 4th resistance R 4 connects, the other end of the 4th resistance R 4 is managed the collector electrode of Q3 respectively with PNP, the other end of capacitor C 1, the negative electrode of diode D1 connects, the anode of diode D1 during with the power supply operate as normal accessory power supply output voltage positive pole be connected.

Preferably, starting circuit for direct-current switch power supply of the present utility model also comprises voltage-stabiliser tube Z1, is connected with the other end of the 5th resistance R 5, an end of the 4th resistance R 4 respectively behind the base stage serial connection voltage-stabiliser tube Z1 of described NPN pipe Q1.

Press such scheme, when PNP pipe Q3 conducting, output voltage raises, and the control signal of sample circuit raises, and through two NPN pipe Q1, Q2 negative feedback control, PNP pipe Q3 closes, and output voltage descends; When the control signal of sample circuit reduced, through two NPN pipe Q1, Q2 negative feedback control, Q3 was open-minded for the PNP pipe, and output voltage rises.Therefore the output voltage of start-up circuit can be determined by sample circuit, keeps by the switching of PNP pipe Q3 and sets the stable of output voltage.

Beneficial effect

1, no PN junction pressure drop in the start-up circuit can be satisfied the power reguirements of control chip under the low input condition.

2, start-up circuit need not to set operating voltage by voltage-stabiliser tube, has avoided the high quiescent dissipation of voltage-stabiliser tube current-limiting resistance under the high input voltage condition.

3, during the power supply operate as normal, start-up circuit is in buttoned-up status, and therefore the quiescent dissipation of start-up circuit almost can be ignored when steady operation.

4, the start-up circuit device work is few, the simplicity of design cost is low, is particularly suitable for the harsh requirement in high power density electric power source pair of module device and PCB space.

Description of drawings

Fig. 1 is a power initiation circuit diagram in the prior art.

Fig. 2 is an operation principle flow chart of the present utility model.

Fig. 3 is a circuit block diagram of the present utility model.

Fig. 4 is the circuit block diagram of another embodiment of the utility model.

Embodiment

Further specify the technical solution of the utility model below in conjunction with accompanying drawing:

Fig. 1 is a kind of typical start-up circuit schematic diagram, and its start-up circuit is made up of R1, Z1, Q1.When power on circuitry, the base voltage of Q1 is by the 10V that is set at of voltage-stabiliser tube Z1, because the PN junction pressure drop of Q1 pipe is 0.7V, therefore the emitter at Q1 produces the voltage of 9.3V to chip UC3843 power supply.When the power supply operate as normal, auxiliary winding provides operating voltage 11V to chip, and the Q1 pipe bears back-pressure and closes.There are two remarkable shortcomings in traditional start-up circuit: because the voltage stabilizing operation principle of voltage-stabiliser tube need offer the certain static working current of voltage-stabiliser tube Z1, the maximum resistance that therefore common current-limiting resistance R1 can get is determined by minimum input voltage 9V (1).And when the input voltage of power supply was 75V, the power consumption on the R1 will increase greatly.Even and power work is when stable state, the loss that this current-limiting resistance produces also exists always, is unfavorable for the raising of efficient.(2) because Q1 manages the existence of PN junction pressure drop, when input voltage was 9V, the supply power voltage of chip was 8.3V, and the exemplary operation voltage of existing low voltage control chip is 8.5V, when this just meaned input voltage less than 9.2V, power supply all can't operate as normal, does not obviously meet design requirement.Therefore need a kind of low-power consumption start-up circuit that can be operated under super wide range, the low input condition of design just to seem very important.

As Fig. 2, shown in Figure 3, start-up circuit of the present utility model comprises first resistance R 1, second resistance R 2, the 3rd resistance R 3, the 4th resistance R 4, the 5th resistance R 5, PNP manages Q3, the one NPN manages Q1, the 2nd NPN pipe Q2 and diode D1, wherein an end of second resistance R 2 respectively with an end of first resistance R 1, the emitter of one end of the 3rd resistance R 3 and PNP pipe Q3 connects, the other end of second resistance R 2 is managed the collector electrode of Q2 respectively with the 2nd NPN, the base stage of the other end of the 3rd resistance R 3 and PNP pipe Q3 connects, the other end of first resistance R 1 is managed the base stage of Q2 respectively with the 2nd NPN, the collector electrode of the one NPN pipe Q1 connects, the emitter of the 2nd NPN pipe Q2 is managed the emitter of Q1 respectively with a NPN, one end of the 5th resistance R 5, accessory power supply output voltage negative pole connects back ground connection when one end of capacitor C 1 and power supply operate as normal, the other end of the 5th resistance R 5 is managed the base stage of Q1 respectively with a NPN, one end of the 4th resistance R 4 connects, the other end of the 4th resistance R 4 is managed the collector electrode of Q3 respectively with PNP, the other end of capacitor C 1, the negative electrode of diode D1 connects, the anode of diode D1 during with the power supply operate as normal accessory power supply output voltage positive pole be connected.

The operation principle and the course of work

Start-up circuit of the present utility model is made up of resistance, diode, triode.When power initiation, by start-up circuit to the control IC 9V that powers; After the power supply operate as normal, commutation circuit output 11V voltage is through closing start-up circuit fully behind the diode D1.

Press such scheme, when PNP pipe Q3 conducting, output voltage V o raises, and the sampling control signal of sampling resistor R4, R5 raises.When output voltage reached 9V, just sampled signal voltage was when the base voltage of NPN pipe Q1 is 0.7V, and therefore a NPN manages the Q1 conducting.Turn-off fully owing to the base earth of the 2nd NPN pipe Q2, so the collector electrode generation high voltage on the 2nd NPN pipe Q2, thereby cause the base voltage of PNP pipe Q3 identical with emitter voltage, so PNP pipe Q3 shutoff, output voltage V o reduces.

When PNP pipe Q3 turn-offed, output voltage V o reduced, and the sampling control signal of sampling resistor R4, R5 reduces.When output voltage was lower than 9V, just less than 0.7V, NPN pipe Q1 turn-offed sampled signal voltage at the base voltage of NPN pipe Q1, and causing the base stage of the 2nd NPN pipe Q2 is high level, therefore the complete conducting of the 2nd NPN pipe Q2.Be low in the current collection of the 2nd NPN pipe Q2 low level very thereby cause the base voltage of PNP pipe Q3 this moment, so PNP pipe Q3 conducting, and output voltage V o rises.

When behind the power initiation during operate as normal, the voltage Vn that the auxiliary winding of power supply produces is 11V.Through output voltage V o behind the diode D1 is about 10.3V, so the sampling control signal of sampling resistor R4, R5 is high always.When the voltage that this moment, sampled signal voltage produced on the base stage of NPN pipe Q1 is 0.7V, NPN pipe Q1 conducting.Turn-off fully owing to the base earth of the 2nd NPN pipe Q2, therefore manage the collector electrode generation high voltage of Q2, thereby cause the base voltage of PNP pipe Q3 identical, so PNP pipe Q3 turn-offs fully with emitter voltage at the 2nd NPN.Therefore the quiescent dissipation of start-up circuit is extremely low when the power supply operate as normal, can obtain higher efficient.

Starting circuit for direct-current switch power supply of the present utility model as shown in Figure 4 also comprises voltage-stabiliser tube Z1, is connected with the other end of the 5th resistance R 5, an end of the 4th resistance R 4 respectively behind the base stage serial connection voltage-stabiliser tube Z1 of described NPN pipe Q1.This voltage-stabiliser tube Z1 can be used for suppressing the PN junction temperature of NPN pipe Q1 and float, and improves the precision of voltage regulation of start-up circuit when different temperatures.

The utility model adopts a few control device to realize the start-up circuit design of power supply under super wide range, the low input condition, obtains control characteristic preferably with less peripheral circuit.Start-up circuit of the present utility model cuts out when the power supply steady operation fully, and static working current is extremely low, can obtain greater efficiency.Because this start-up circuit is simple in structure, has saved the pcb board circuit space greatly, the high power density power module that is specially adapted under super wide range, the low input condition starts the power supply design.

Claims

1. starting circuit for direct-current switch power supply, it is characterized in that comprising first resistance R 1, second resistance R 2, the 3rd resistance R 3, the 4th resistance R 4, the 5th resistance R 5, PNP manages Q3, the one NPN manages Q1, the 2nd NPN pipe Q2 and diode D1, wherein an end of second resistance R 2 respectively with an end of first resistance R 1, the emitter of one end of the 3rd resistance R 3 and PNP pipe Q3 connects, the other end of second resistance R 2 is managed the collector electrode of Q2 respectively with the 2nd NPN, the base stage of the other end of the 3rd resistance R 3 and PNP pipe Q3 connects, the other end of first resistance R 1 is managed the base stage of Q2 respectively with the 2nd NPN, the collector electrode of the one NPN pipe Q1 connects, the emitter of the 2nd NPN pipe Q2 is managed the emitter of Q1 respectively with a NPN, one end of the 5th resistance R 5, accessory power supply output voltage negative pole connects back ground connection when one end of capacitor C 1 and power supply operate as normal, the other end of the 5th resistance R 5 is managed the base stage of Q1 respectively with a NPN, one end of the 4th resistance R 4 connects, the other end of the 4th resistance R 4 is managed the collector electrode of Q3 respectively with PNP, the other end of capacitor C 1, the negative electrode of diode D1 connects, the anode of diode D1 during with the power supply operate as normal accessory power supply output voltage positive pole be connected.

2. starting circuit for direct-current switch power supply according to claim 1, it is characterized in that, this start-up circuit also comprises voltage-stabiliser tube Z1, is connected with the other end of the 5th resistance R 5, an end of the 4th resistance R 4 respectively behind the base stage serial connection voltage-stabiliser tube Z1 of described NPN pipe Q1.