CN2357438Y

CN2357438Y - Switch power with over-voltage protection and output soft starting function

Info

Publication number: CN2357438Y
Application number: CN 98249200
Authority: CN
Inventors: 王跃斌
Original assignee: YONGDAHUI SCIENCE AND TECHNOLOGY Co Ltd SHENZHEN CITY
Current assignee: YONGDAHUI SCIENCE AND TECHNOLOGY Co Ltd SHENZHEN CITY
Priority date: 1998-12-15
Filing date: 1998-12-15
Publication date: 2000-01-05
Anticipated expiration: 2008-12-15

Abstract

The utility model relates to a switch power supply with over-voltage protection and output soft starting functions, which comprises a rectification filter unit 1, a DC/DC conversion unit 2 and a feedback loop composed of a feedback and over-voltage protection unit 3, an optical coupling unit 4 and a PWM control unit 5 and connected between an output terminal 7 and the control terminal of the DC/DC conversion unit 2; a voltage stabilizing diode in the input loop of the feedback and over-voltage protection unit 3 is connected with a capacitor in parallel. When the power supply is switched on, even if the power supply feedback is comparatively slow, extremely smooth ascending monotone waveforms can be output by making use of the soft starting technique provided by the utility model, therefore, the utility model can realize the output soft starting when the power supply is switched on and can also achieve over-voltage protection by adopting less components.

Description

Switching Power Supply with overvoltage protection and output soft start function

The utility model relates to power technology, more particularly, relates to a kind of Switching Power Supply with overvoltage protection and output soft start function that adopts light-coupled isolation.

For improving safety that Switching Power Supply uses and reliable, usually the output in Switching Power Supply is added with soft starting circuit, to prevent that output voltage from producing overshoot electric equipment is caused adverse effect when starting shooting, the realization of general soft start, all be that output at voltage feed-back amplifier adds a charging and discharging circuit, if but the feedback of power supply is slow, be difficult for dull output voltage that rises of output generation when start.Simultaneously, general power supply also need be provided with an overvoltage crowbar, adopts the Switching Power Supply of light-coupled isolation, a simple limited pressure protective circuit can be set, as shown in Figure 3.

The purpose of this utility model is to provide a kind of novel Switching Power Supply; this Switching Power Supply has overvoltage protection and output soft start function, can overcome prior art switch power soft-start poor effect, can not take into account the shortcoming of overvoltage protection; and have succinct, with low cost characteristics of circuit.

The purpose of this utility model is to realize like this; construct a kind of Switching Power Supply; comprise the rectification filtering unit 1 that connects input 6; input connects rectification filtering unit 1 output and output is the DC/DC converter unit 2 of Switching Power Supply output 7; and be connected feedback loop between Switching Power Supply output 7 and DC/DC converter unit 2 control ends; described feedback loop comprises by feedback and Overvoltage protecting unit 3; the series loop that optical coupling unit 4 and PWM (pulse-width modulation) control unit 5 is formed is connected in parallel to a capacitor on the voltage stabilizing didoe in the input circuit of described feedback and Overvoltage protecting unit 3.

Implement the Switching Power Supply that the utility model provides; has following remarkable advantage; the output soft Starting Technology of utilizing the utility model to provide; owing to change the DZ1 in original circuit (Fig. 3) into a capacitor, when start, even the power supply feedback is slow; output also can produce a dull waveform that very steadily rises; if simultaneously that a capacitor C is in parallel with DZ1, the output soft start can be realized overvoltage protection again in the time of both can realizing starting shooting.Adopt less components and parts like this, realized overvoltage protection and output soft start.

In conjunction with the accompanying drawings and embodiments, further specify characteristics of the present utility model, in the accompanying drawing:

Fig. 1 is the circuit block diagram schematic diagram of Switching Power Supply of the present utility model;

Fig. 2 is the circuit theory schematic diagram of Switching Power Supply of the present utility model;

Fig. 3 is the schematic diagram that adopts the limited pressure protective circuit of the Switching Power Supply that optical coupling isolates.

As shown in Figure 1; in the logic diagram of Switching Power Supply with overvoltage protection and output soft start function of the present utility model; mainly comprise the rectification filtering unit 1 that connects Switching Power Supply input 6, input connects rectification filtering unit 1 output and output is the DC/DC converter unit 2 of Switching Power Supply output 7; and being connected feedback loop between Switching Power Supply output 7 and DC/DC converter unit 2 control ends, this feedback loop comprises the polyphone loop that feedback and Overvoltage protecting unit 3, optical coupling unit 4 and PWM (pulse-width modulation) control unit 5 are formed.The utility model is exactly that the capacitor (C1 among Fig. 3, C29 among Fig. 2) that is connected in parallel on the voltage stabilizing didoe in the input circuit of described feedback and Overvoltage protecting unit 3 is realized.

Input rectifying filter unit 1 is made up of F1, R22, R1, R1-1, ZN1, L1, C1, C2, C3, C4, C7, C5, C6Z in Fig. 2 among Fig. 1; DC/DC converter unit 2 among Fig. 1 comprises in Fig. 2: R4; C8; D1; R9; C9; R6; D9; R19; C18; C20; C21; L2; R24; D16; C22; R28; D4; R10; C10 etc.; the feedback of feedback loop and Overvoltage protecting unit 3 comprise R29-R33 in the pie graph 1 in Fig. 2; R25; R34; C28; C29; Q3; IC4 etc.; optical coupling unit 4 among Fig. 1 is corresponding to the PC1 among Fig. 2, the R2 that the PWM among Fig. 1 (pulse-width modulation) control unit 5 comprises among Fig. 2; R2-2; R3; R3-3; R5; R7; D2; D3; R8; D5; D7; Q2; Q4; IC1; C11-C15; C17; R11-R18; R37 etc.Wherein: IC1 is a power technique fields pwm chip commonly used, as UC3842A, UC3804N, UC3825, UC3846, TL494 etc.; IC4 is for being built-in with 2.The operational amplifier of 5V benchmark, it can be TL431C, herein as feedback, also can consider to adopt conventional amplifier to replace, as LM328, LM324 etc.; PC1 is optocoupler PC817C.

The output soft Starting Technology that the utility model proposes; only need to change the DZ1 among Fig. 3 into an electric capacity; when start; even the power supply feedback is slow; output also can produce a dull waveform that very steadily rises; if simultaneously that capacitor C is in parallel with DZ1, the output soft start can be realized overvoltage protection again in the time of both can realizing starting shooting.Adopt less components and parts like this, realized overvoltage protection and output soft start.

As shown in Figure 2, when start, output is given the charging of capacitor C 29 two ends, because voltage can not suddenly change on the electric capacity, when output voltage rises, the D end also rises to the secondary ground voltage, make the CE two ends saturation conduction of Q3, and the conducting of Q3 makes have electric current to flow through on the optocoupler PC1, C IC4 this moment output still is in high-impedance state, this moment, R13 two ends were because the electric current of optocoupler flows through, and produced a voltage.This voltage is greater than the 2.5V benchmark of IC1 pressure feedback port, make the interior voltage comparator end output of IC1 narrow down, promptly drive the pulse narrowing of Q1, the fast rise of restriction output, voltage along with the C29 two ends rises like this, output voltage also slowly rises, and just produces the perfectly dull waveform that rises of a comparison.Raise in case the realization of overvoltage protection is an output voltage, make the D12 conducting, and the conducting of D12; cause 03C, E two ends saturation conduction, the electric current that flows through optocoupler PCI diode two ends this moment is big when more normally working, and makes voltage＞2.5V on the R13; 6 pin output pulse narrowing with IC1; make output voltage drop, and voltage drop in a single day, Q3 just ends; the optocoupler electric current diminishes; output is again to rising, and such reverse operation makes output voltage stabilization remain unchanged on some values.

The utility model instead swashs power supply with routine and explains, and also can be applicable to positive activation type simultaneously, recommends half-bridge, in the various topologys such as full-bridge.

Claims

1; a kind of Switching Power Supply with overvoltage protection and output soft start function; comprise the rectification filtering unit 1 that connects input 6; input connects rectification filtering unit 1 output and output is the DC/DC converter unit 2 of Switching Power Supply output 7; and be connected feedback loop between Switching Power Supply output 7 and DC/DC converter unit 2 control ends; it is characterized in that; described feedback loop comprises by feedback and Overvoltage protecting unit 3; the series loop that optical coupling unit 4 and PWM (pulse-width modulation) control unit 5 is formed is connected in parallel to a capacitor on the voltage stabilizing didoe in the input circuit of described feedback and Overvoltage protecting unit 3.

2, Switching Power Supply according to claim 1 is characterized in that, described input rectifying filter unit 1 comprises bridge rectifier (BD1).

3, Switching Power Supply according to claim 1 is characterized in that, described optical coupling unit 4 comprises optical coupling element PC817C (PC1).

4, Switching Power Supply according to claim 1 is characterized in that, described pulse width modulation controlled unit 5 comprises pwm chip, and it can UC3842A, UC3804N, the IC of models such as UC3825, UC3846.