Zoomlion F-2250 switching regulated power supply

This is the schematic diagram of Zoomlion F-2250 power amplifier switching regulated power supply . It consists of input power purification and rectification filter
circuit, integrated control module, excitation inverter and switching circuit, step-down and full-wave rectification circuit and feedback adjustment circuit .     After the mains power is input, the power purification filter circuit composed of the inductor Li and the capacitor cl performs purification and filtering to eliminate interference pulses in the power supply. Then, it is rectified by the bridge rectifier circuit CRt, filtered by Q and IC3 and then outputs a smooth DC voltage. Provides power to the pulse switching circuit. The pulse switching circuit with a voltage of about 300V     works in a high-frequency switching state and is the energy conversion part of the switching power supply. It consists of three pairs of 30A/450V VIVIS tubes that work alternately. Under the action of the excitation pulse, the two windings of the secondary winding of the transformer Ti receive two excitation pulses with opposite phases, and are applied to the gates of VTi ~ VT3 and VT4 ~ VT6 respectively. When the gates of VTi ~ VT3 receive positive pulses and enter the conduction state, the gates of VT4 ~ VT6 receive negative pulses and enter the cut-off state. At this time, 300V DC voltage is added to the primary winding of transformer Tz through the conductive tubes VTi~VT3 , causing the current in the primary of Tz to rise linearly. When the positive pulses on the gates of VTi~VT3 end and change to negative pulses , VTi~VT3 are cut off. At the same time, the excitation pulses on the gates of VT4~VT6 change from negative pulses to positive pulses, causing VT4~VT6 to conduct. In this way, the current loop in the Tz primary winding will not be interrupted by the cut-off of VTi-VT3, so VT4~VT are also called freewheeling tubes of the primary winding. Due to the conduction of VT4~VT6, the current in the Tz primary winding begins to be linear decline. It can be seen that what is obtained in the Tz primary winding is a sawtooth waveform pulse current. Due to the on-off of VTi ~ VT3, the pulse voltage formed in the primary of T2 is coupled to the secondary, and supplies power to the power amplifier circuit after rectification and filtering.     The high-frequency voltage output by the secondary of high-frequency transformer T2 is rectified by a bridge full-wave rectifier circuit composed of VD6~VDg, and filtered by Cll~C14 capacitors to form a symmetrical voltage output of ±70V. The other secondary voltage of T2 is half-wave rectified by VDic, and stabilized by a voltage stabilizing circuit composed of VT7 and VIli, etc., and then outputs a positive 12V DC voltage for use by the automatic cooling fan.