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Method for achieving soft starting of PWM convertor

A realization method and soft-start technology, applied in the direction of output power conversion devices, electrical components, etc., can solve the problems of large switching tube current, long conduction time, and switching tube damage

Inactive Publication Date: 2013-12-11
THE 724TH RES INST OF CHINA SHIPBUILDING IND
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Problems solved by technology

[0003] At the moment when the switching power supply is turned on, if the duty ratio of the driving signal generated by the drive circuit of the converter is the maximum value, the conduction time of the switch tube in one cycle is the longest, and the current passing through the switch tube during the conduction time is very large. Once the passing current exceeds the limit value of the switch tube, the switch tube will be damaged

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  • Method for achieving soft starting of PWM convertor

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Embodiment Construction

[0009] A method for realizing the soft start of a PWM converter of the present invention. For specific implementation steps, see figure 1 :

[0010] 1. Use the sawtooth wave generator circuit to generate a sawtooth wave with the same frequency and duty cycle as the PWM drive signal;

[0011] 2. Send the sawtooth wave to the voltage comparator for comparison with the reference voltage to obtain a voltage signal;

[0012] 3. Send the output voltage of the voltage comparator and the PWM drive signal to the AND gate for comparison to obtain a new drive signal.

[0013] The circuit schematic diagram of a method for realizing soft start of a PWM converter of the present invention can be found in figure 2 , N1 NAND gate in the figure, the model is H006, N2 is the operational amplifier, the model is LM111, N3 is the AND gate, the model is H002.

[0014] 1. N1, R1, R2, R3, V1 and C1 form a sawtooth wave generating circuit. When the input drive signal is low level, pin 3 of N1 outp...

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Abstract

The invention relates to a method for achieving soft starting of a PWM convertor. According to the method, a sawtooth wave generating circuit, a voltage comparator and an AND gate are utilized for achieving soft starting of the PWM convertor. The functional block diagram for achieving the technology is shown as the attached picture. The treatment process comprises that firstly, the sawtooth wave generating circuit is utilized for converting an input drive signal into a sawtooth wave, wherein the frequency and the duty ratio of the sawtooth wave is unchanged; then the voltage comparator is adopted for comparing the sawtooth wave and a slowly-rising reference voltage, and a pulse voltage signal is obtained, wherein the duty ratio of the pulse voltage signal is gradually increased; finally, the pulse voltage signal and an input drive voltage are compared through the AND gate to obtain an output drive voltage, wherein the duty ratio of the output drive voltage is gradually increased. At the moment of starting up, the duty ratio of the drive voltage is gradually increased, after a switching power supply works normally, the voltage comparator outputs a high level all the time, and the output drive voltage and the input drive voltage are completely equal. Therefore, soft starting of the PWM convertor is achieved, and the method has broad application prospects in the field of power sources.

Description

technical field [0001] The invention belongs to special power supply technology, and is a method for realizing soft start of a PWM converter. Background technique [0002] The PWM converter is a kind of switching power supply. In the PWM working mode, the working frequency of the switching tube of the converter remains unchanged. After sampling, comparison and error amplification, the conduction time of the switching tube is controlled, so as to realize the output voltage stability of the switching power supply. pressure control. [0003] At the moment when the switching power supply is turned on, if the duty ratio of the driving signal generated by the drive circuit of the converter is the maximum value, the conduction time of the switch tube in one cycle is the longest, and the current passing through the switch tube during the conduction time is very large. Once the passing current exceeds the limit value of the switch tube, the switch tube will be damaged. Therefore, a...

Claims

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Application Information

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IPC IPC(8): H02M1/36H02M1/08
Inventor 杨香兵蔡宝龙
Owner THE 724TH RES INST OF CHINA SHIPBUILDING IND
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