Control circuit and switching converter using same

Abstract

The invention discloses a control circuit and a switching converter using the same. According to the embodiment of the invention, the detection signal is generated by detecting the difference between the charging charge and the discharging charge on the junction capacitor during the turn-off period of the main switch tube, and the turn-on time of the auxiliary switch tube is adjusted according to the error between the detection signal and the reference signal. Therefore, the voltage between the two power ends when the main switch tube is switched on is reduced, the leakage inductance energy is recovered, and the electromagnetic interference is improved. The control circuit in the embodiment adopts a closed-loop control mode, the continuous change of the conduction time of the auxiliary switch tube is adaptively adjusted by utilizing the charge conservation principle, the control mode is simple, the response is fast, and the control circuit can be suitable for wide-range alternating-current input voltage or direct-current input voltage.

Description

technical field [0001] The invention relates to power electronics technology, in particular to a switch converter and its control circuit. Background technique [0002] At present, switching converters are widely used to rectify the AC power of the mains and provide the DC voltage required by the load. The switching converter has a magnetic element, which stores energy in the magnetic element when the switch tube is turned on, and delivers the energy stored in the magnetic element to the power converter of the load when the switch tube is turned off. When the switching tube works in the hard switching mode, the waveforms of the voltage drop and the current rise overlap during the conduction process, so the turn-on loss is large. In the prior art, an active clamp is usually used to recover energy in the magnetic element to improve efficiency. [0003] Usually the main switch and the auxiliary switch are turned on and off alternately in a complementary manner. When the main...

AI Technical Summary

Problems solved by technology

Since the main switching tube and the auxiliary switching tube are turned on and off alternately in a complementary manner, the detection method and control method are relatively complicated

In addition, when the switching converter inputs AC voltage, the conduction time of the auxiliary switching tube cannot follow the change of the AC input voltage, resulting in unstable zero-voltage turn-on of the main switching tube, thereby affecting the efficiency of the switching converter

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