Active clamp converter and its control method

Abstract

The present invention is an active clamp converter and its control method, including the following steps: detecting a load state, when the load state is light load, controlling the switching frequency of a main switching element according to an omission mode, and when the load When the state is not light load, the switching frequency of the main switching element is controlled according to an active clamp mode. In the omission mode, the switching frequency of the main switching element decreases as the load decreases, so as to meet the energy efficiency condition under light load and provide a power saving mode (power saving) function. In the active clamping mode, the main switching element is controlled to be turned on when reverse current is generated, thereby reducing the switching loss when the main switching element switches.

Description

technical field [0001] The invention is a converter, especially an active clamp converter and its control method. Background technique [0002] see Figure 13 Middle (a)~(f) and Figure 14 As shown, the waveform diagram and equivalent circuit diagram of the control signal of the general active clamp converter, the general active clamp converter has a primary side and a secondary side, the primary side is electrically connected to an AC power source 110, And includes an electromagnetic filter 121, a rectifier 122, a main switching element Q1, a secondary switching element Q2, a magnetizing inductance L1, a primary side leakage inductance L2, a primary side capacitor C1 and a primary side coil W1 . [0003] The electromagnetic filter 121 is electrically connected between the AC power source 110 and the rectifier 122 to isolate the electromagnetic interference in the AC power source 110. The rectifier 122 receives the AC power source 110 and outputs it after rectification, an...

AI Technical Summary

Problems solved by technology

[0012] However, the current level of the excitation current of the general active clamp converter will change with the state of the load 130. Generally speaking, when the load 130 is higher, the current level of the excitation current at the primary side of the active clamp converter will be higher, so when the state of the load 130 exceeds a first critical value, when the current in the oscillation circuit of the primary side is oscillating back and forth, the current minimum value of the valley will be due to the excitation current of the primary side of the active clamp converter The current level of the current level is pulled up to exceed 0 ampere, that is, when the state of the load 130 exceeds a first critical value, no reverse current will be generated, so the body diode (body diode) of the main switching element Q1 does not It will conduct forward, so the voltage difference between the two ends of the main switching element Q1 will not decrease, resulting in too high switching loss when the main switching element Q1 switches

Images