Control method of excited push-pull converter with zero-voltage switching and excited push-pull converter

Abstract

The invention discloses a control method of an excited push-pull converter with zero-voltage switching and the excited push-pull converter. According to the magnitude of exciting current of a coupling transformer in the excited push-pull converter, the dead time of two main power MOS tube driving signals output by a controller is adjusted, in the dead time, the energy of the exciting current of the coupling transformer is used for completely releasing charges stored in a parasitic capacitor of one main power MOS tube, needing to be switched from the switch-off state to the switch-on state, in the excited push-pull converter, when diodes which are arranged in the main power MOS tube and are connected in an anti-parallel mode are switched on, the controller outputs a driving signal to control the main power MOS tube to be switched on, and zero-voltage switching is realized. The conditions for realizing zero-voltage switching of the primary MOS tube are irrelevant to the range of an input voltage and an output load, and it can be ensured that zero-voltage switching of a circuit is realized within the full-load range.

Description

technical field [0001] The invention relates to a push-pull converter, in particular to an excited push-pull converter with zero-voltage switching characteristics, and also to a control method for the excited push-pull converter with zero-voltage switching. Background technique [0002] The circuit structure of the push-pull converter is simple, the drive circuit does not need to be isolated, the transformer is bidirectionally excited when the circuit is working, and the utilization rate of the magnetic core is high. Therefore, this kind of converter has the advantages of small size, high efficiency and good dynamic response, but because the converter When working, the voltage stress of the switch tube is twice the input voltage, so this kind of converter is often used in medium and high power occasions with low voltage input. [0003] The push-pull converter circuit topology is as figure 1 As shown, the two switching tubes Q1 and Q2 in the circuit are respectively connecte...

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Problems solved by technology

The control method of this scheme is: when the input voltage is low or the output is heavy load, the push-pull converter needs to work under the condition that the duty cycle of the driving signal is close to 0.5; and when the input voltage is high or the output is light Under the condition of load, the push-pull converter works in PWM mode. At this time, the duty cycle of the driving signal controlling the two switching tubes on the primary side is significantly reduced. In this working mode, the circuit cannot realize zero-voltage switching.

The disadvantage of this implementation scheme is that the conditions for the circuit to realize zero-voltage switching are always related to the size of the output load, and under the condition of high input voltage or light output load, this control method will not be able to achieve zero-voltage switching, especially at high Under the condition of high frequency, it will bring a large switching loss

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