Seamless mode switching system suitable for double-clamp zero-voltage switching converter

Abstract

The invention discloses a seamless mode switching system suitable for a double-clamp zero-voltage switching converter, which improves the efficiency of the converter in a light load by reducing the switching frequency of the converter in the light load. Different timers are switched and used according to the size of the loads to adjust the switching frequency, in order to avoid frequent switching of the timers near a switching point, hysteresis control is introduced, in order to avoid the problem of frequency abrupt change caused by switching of the timers, an amplitude limiting unit is additionally arranged in a variable-frequency timer, the highest frequency of the variable-frequency timer is limited to be equal to the frequency of a fixed-frequency timer, and reasonable parameter design is carried out, so that the switching frequency of the converter is ensured to continuously change along with the change of the load. Furthermore, as the switching frequency of the converter is completely the same as the frequency of the variable-frequency timer, the fixed-frequency timer and a timer selection unit can be removed, and the complexity of the system can be greatly simplified. The seamless mode switching system is easy to implement, safe and effective.

Description

technical field [0001] The invention belongs to the technical field of converters, in particular to a seamless mode switching system suitable for double-clamp zero-voltage switching converters. Background technique [0002] Double-clamp zero-voltage switching converter is an isolated DC / DC circuit topology, which is widely used in communication and military power supply fields due to its simple structure, high efficiency, isolation of primary and secondary sides, and wide input and output ranges. Such as figure 1 The shown double-clamp zero-voltage switching converter includes the first switching tube Q 1 , the second switching tube Q 2 , the third switching tube Q 3 , the fourth switching tube Q 4 and the fifth switching tube Q 5 , where the third switching tube is also called active clamping tube, and a power transformer T, such as figure 1 As shown in the dashed box, one end of the primary side of the power transformer is connected to the first switching tube Q 1 a...

AI Technical Summary

Problems solved by technology

And the switching tube Q 2 , switch Q 3 and switch Q 5 The zero-voltage turn-on needs to rely on the magnetizing inductor current to fully discharge its junction capacitance. When the magnetizing inductor current is reduced to a certain amplitude, the magnetizing inductor current is not enough to charge the switching tube Q within the dead time. 2 , switch Q 3 and switch Q 5 The junction capacitance is fully discharged, at this time the switch Q 2 Q 3 Q 5 It will not be possible to achieve zero-voltage turn-on, resulting in large turn-on losses and reducing the efficiency of the converter

In addition, when the load of the converter is light, the drive loss proportion of the converter will increase, which will also reduce the efficiency of the converter

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