Self-oscillation starting output end controlled anti exciting converter

Abstract

The invention discloses a flyback convertor controlled by a self-oscillation start output end, which comprises a flyback power conversion main circuit, a start oscillation circuit, a cut-off device and a PWM control circuit. The start oscillation circuit is connected with an MOS main switch tube grid in the flyback power conversion main circuit, and the cut-off device is connected in a return circuit of the start oscillation circuit. The PWM control circuit outputs two paths of signals, one path of trigger signal is connected to the cut-off control end of the cut-off device for controlling the cut-off of the start oscillation circuit, and the other path of PWM drive signal is connected to the MOS main switch tube grid in the flyback power conversion main circuit. The invention has the following characteristics that the flyback convertor does not need an extra auxiliary power supply to supply power to the PWM control circuit, easily realizes the control mode of synchronous rectification, and also easily realizes various protective circuits, and additional functions such as parallel current equalization, and so on; and the band width of a control loop is not limited to make the dynamic performance of the circuit better.

Description

technical field [0001] The invention relates to a flyback converter, in particular to a flyback converter controlled by a self-excited oscillation starting output terminal. Background technique [0002] At present, there are various forms of self-oscillating flyback converters (that is, RCC circuits) in the industry. Commonly used RCC circuits such as figure 1 As shown, it is generally composed of the main current circuit part, the start-up oscillation circuit part, the negative feedback control voltage circuit part and the regulated output circuit part. Among them, the start-up oscillation circuit part is mainly composed of triode TR2, resistors R1, R2, R1, R2 and capacitors C2 and C3; the negative feedback control voltage loop part is composed of voltage regulator Adj and optocoupler OC1. [0003] The specific working principle is: when the input voltage is applied, the input voltage is applied to the gate of the MOS transistor TR1 through the resistors R1 and R2, so that...

AI Technical Summary

Problems solved by technology

[0007] The self-excited oscillating flyback converter circuit of the first scheme, that is, the RCC circuit has a simple structure and low cost, but there are certain problems in the reliability of the product when it is relatively high-power and mass-produced, and the efficiency is low when it is light-loaded; Due to the presence of linear optocouplers in the two schemes, the bandwidth of the control loop is limited, and the life and reliability of the product are greatly reduced.

Images