Switching power supply circuit of Dongshi IDS-2000F set-top box

Switching power supply circuit of Dongshi IDS-2000F set-top box

The switching power supply circuit of Dongshi IDS-2000F set-top box is mainly composed of AC input circuit , switching oscillation circuit, secondary output circuit and
voltage stabilizing control circuit, as shown in Figure 2.63.
    (1) AC input circuit
    The AC input circuit is composed of switch S, fuse Fl, mutual inductance filter cl, LF1 and bridge rectifier circuit (VDI-VD4).
Its function is to filter out the interference of the AC 220V input voltage and Rectified into a DC voltage of 300V, C2 is a smoothing filter capacitor.
    (2) Switching oscillation and control circuit
    The switching oscillation and control circuit are integrated in Ul TEA1523P. DC 300 V
supplies power to Ul⑧ pin through the primary winding ①～② of the switching transformer Ti. The switching tube is integrated in Ul, and the positive feedback winding Pin @~④ provides power and positive feedback voltage to U1 to make Ul enter the switching
oscillation state.
    (3) The attack stage of the secondary output circuit
    switching transformer Ti has multiple sets of outputs, which are rectified and filtered to output +5 V, +21 V, +30 V and +3.3 V voltages respectively .
    (4) Voltage stabilizing circuit
    The voltage stabilizing circuit is connected to the +5V output circuit. Rl4 and R11 form a voltage dividing circuit. U3 is the error detection and error amplifier. It feeds the error
signal back to the ④ pin of Ul through the optocoupler. Control the oscillation output of Ul.