Self-adaptive soft switching control system of primary side feedback active clamping flyback converter

Abstract

The invention discloses a self-adaptive soft switching control system of a primary side feedback active clamping flyback converter, and relates to the technical field of isolated converters, and the system comprises a main topology circuit and a closed-loop control loop; an auxiliary winding is additionally arranged on the secondary side of a transformer, voltage sampling is carried out on the two ends of the auxiliary winding through two divider resistors, and feedback voltage of winding voltage is input into a closed-loop control loop; a current sampling resistor is added between a main switching tube and a ground end, and the voltage of the sampling resistor is input to a closed-loop control loop; the closed-loop control loop comprises a primary side current detection module, an auxiliary winding detection module, a dead zone time calculation module and a PWM driving module; the dead time calculation module calculates the dead time of the control signals of the main switch tube and the auxiliary switch tube according to the time signals and the current signals received by the input end; and the system is connected with a controlled switching power supply to form a closed loop, ZVS of two switching tubes is achieved, switching loss is reduced, and therefore the efficiency of the whole system is improved.

Description

technical field [0001] The invention relates to the technical field of isolated converters, in particular to an adaptive soft-switching control system for primary side feedback active clamp flyback converters. Background technique [0002] With the development of technology, switching power supply is widely used in small and medium power occasions. The isolated switching power supply can realize the electrical isolation of input and output, which has the characteristics of safety isolation and high reliability. With the continuous development and upgrading of smart devices, and rapid With the continuous promotion and application of technologies such as charging and Universal Serial Bus Power Delivery (USBPD), it is expected that the isolated primary-side feedback flyback converter needs to maintain its own portability while increasing power. This requires increasing the switching frequency of the converter to meet the design requirements of power improvement and miniaturizat...

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Problems solved by technology

[0004] The first solution often used at present is to fix the dead time, but in the case of different input voltages and loads, the optimal dead time should be changed, and the fixed dead time may appear or be longer in different situations. Or short, thus affecting the switching loss and affecting the overall efficiency improvement

The second solution is to directly sample the drain-source voltage of the switching tube through a voltage divider circuit, but because the dead time is very short, a high-speed and high-precision sampling capture method is required to achieve optimal dead-time control, which is difficult

The third solution is to calculate the conduction time of the clamp switch tube and control the current valley value and dead time, but the calculation of the control current valley value and dead time is relatively cumbersome, and it is necessary to accurately control the inductor current , and there is a certain loss in accuracy, it is more troublesome to implement

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