Switching circuit control circuit and switching circuit

Abstract

The invention discloses a switching circuit control circuit and a switching circuit. The switching circuit control circuit comprises a compensation circuit which comprises an output voltage judging circuit, a timing circuit, a transconductance gain adjusting circuit and a transconductance amplifier, wherein the first input end of the transconductance amplifier receives a first voltage signal representing the output current, and the second input end of the transconductance amplifier receives a reference voltage, the output end of the transconductance amplifier is connected with one end of a compensation capacitor, and the other end of the compensation capacitor is grounded, the output voltage judging circuit and the timing circuit are used for receiving a sampling signal representing the output voltage and are respectively connected to the transconductance gain adjusting circuit, the transconductance gain adjusting circuit controls the transconductance gain of the transconductance amplifier, the charging current of the compensation capacitor is increased in the starting stage of the switching circuit, and the voltage rise of the compensation capacitor is accelerated. According to the invention, the rising rate of the voltage during the initial working state of the compensation capacitor is controlled, so that the compensation capacitor can be rapidly charged, and then rapid starting is completed.

Description

technical field [0001] The invention relates to the field of switch circuits, and more specifically, to a switch circuit control circuit and a switch circuit. Background technique [0002] The block diagram of the traditional LED drive circuit is as follows: figure 1 As shown, the external AC input voltage is rectified by the rectifier bridge to obtain a pulsating DC voltage VIN, and then the DC voltage VIN is converted and processed by the switching circuit to generate an output voltage VO to supply the load. The control circuit receives the DC voltage VIN, the output voltage VO and the output of the switching circuit The sampling signal is used to generate a control signal for controlling the switch state in the switch circuit, so that the switch circuit outputs an expected output voltage signal. [0003] Such as figure 2 As shown, the control circuit generally includes five sub-modules: power supply module, sampling circuit, compensation circuit, on-off control circuit...

AI Technical Summary

Problems solved by technology

[0004] However, in actual work, in order to filter out the power frequency ripple, the compensation capacitor in the compensation circuit and the output capacitor in the switch circuit are often selected very large, resulting in the output voltage VO rising very slowly after the drive circuit is started, and each The conduction time of the switching cycle is very short, so the output voltage VO in the power supply module has a weak ability to effectively charge the capacitor C02. It takes a long time from the start of the drive circuit to the power supply voltage VCC to reach the balance of power supply, and it often needs to be restarted several times. Complete the start-up process, which makes the start-up time very long, and even the start-up process cannot be completed in the case of continuous power-on and off.

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