Asymmetric half-bridge flyback drive circuit

Abstract

The invention discloses an asymmetric half-bridge flyback drive circuit, and the circuit comprises a complementary PWM generator, two drive transformers, and a series asymmetric flyback circuit. The separation of the drive transformers enables on / off switching tubes of the circuit to be respectively controlled, thereby improving the quality of a drive signal, and reducing the false triggering caused by the level changes. The dead zone time between the switching tubes is mainly controlled by a complementary signal because of the separated winding, thereby enabling the impact on the dead zone from the drive transformers to be the minimum. In a wide-range and high-input-voltage switching power application, the circuit, compared with the prior art, enables the reliability of a product to be improved.

Description

technical field [0001] The invention relates to the field of switching converters, in particular to an asymmetrical half-bridge flyback drive circuit. Background technique [0002] The rapid development of the field of power electronics has made the application of high-frequency switching power supplies more and more extensive. The input terminals of traditional industrial and civil switching power supplies often need to take power from the grid. After passing through the internal rectification and filtering circuit of the power supply, it becomes a higher DC power, and then input to the power conversion circuit to become a low-voltage DC power to provide power for the load. In order to adapt to the grid standards of different countries, the general two-phase AC input switching power supply has an input voltage range of 85VAC to 264VAC, and the DC voltage after rectification and filtering is about 120VDC to 373VDC. For the switching power supply used in this occasion, accor...

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Problems solved by technology

[0006] Therefore, in order to meet the above requirements and overcome the shortcomings in the above circuits, the method of series mode of the asymmetrical half-bridge flyback circuit is produced. By connecting the primary side in series, the secondary side adopts the transformer coupling method to solve the problem caused by the wide-range high-voltage input. However, for high-voltage input, in the case of a wide range of input voltage, in order to meet the effective voltage equalization of the input bus capacitor, the driving signal requires a small level voltage change and high timing consistency. Therefore, the switching tube drive in the asymmetrical half-bridge flyback circuit in series mode will become more complicated; most of the existing driving methods are optocoupler drive or isolation drive, and ordinary optocoupler is difficult to meet the requirements, although there are High-speed drive optocouplers are available, but their higher prices will also lead to an increase in power supply costs. At the same time, this high-speed optocoupler needs an isolated power supply to supply power to the optocoupler, which in turn leads to an increase in power supply costs. At the same time, as the power supply itself It is also a kind of contradiction; the existing drive usually adopts a magnetic isolation drive method, but under the condition of multiple sets of drive signals, the coupling between the windings is poor, the consistency of the drive signals is poor, and the dead time is not easy to control. It may even cause the drive to work abnormally; at the same time, with the increase in the number of switch tubes, the power consumption of the drive will further increase, which will also affect the quality of the drive waveform

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