Other Excitation Switching Power Supply Circuit
1) Power conversion circuit
The core components of the power conversion circuit are power module VIPer12A, switching transformer T, rectifier VD3, VD4, filter capacitors C4, C3.
300V voltage by R1 current limiting, and then filtered by C1, through the T primary winding P1 added to the IC1 (VIPer12A) power supply terminal ⑤ ~ ⑧ feet, the voltage is not only added to the switching tube D pole it power supply, but also through the high-voltage current source on the ④ feet of the external filter capacitor C2 charging. When the voltage established on both sides of C2 reaches 14.5V, IC1 within the 60kHz pulse width modulator and other circuits began to work, the excitation pulse generated by the circuit to make the switching tube work in the switching state. After the switching tube is on, the 300V voltage at the two ends of C1 forms a circuit through the P1 winding and the switching tube to ground, so that the P1 generates an upward positive and downward negative electromotive force, and the P2 and P3 windings are induced to have a downward positive and upward negative electromotive force, and the energy is stored in the internal part of the T because of the reverse bias cutoff of VD1 and VD2. After the switching tube is cut off, the electric potential of each winding of T is inverted, so the pulse voltage output from P2 winding is rectified by VD1 and filtered by C3 to produce about 18V, and one way through VD2 to replace the start-up circuit to supply power for the control part of IC1, and the other way to supply power for the power tube driving circuit, fan motor, oscillator and other circuits. the pulse voltage output from P3 winding is rectified by VD3 and filtered by C4 to produce about 8V, and then passed through VD3 and C4 to produce about 8V, and then passed through VD3 and C4 to produce about 8V. P3 winding output pulse voltage through the VD3 rectifier, C4 filter to produce 8V or so, and then through the R4 current limiting, C5 filtering, for 5V regulator IC2 power supply, which regulates the output 5V voltage. 5V voltage filtered by the C6 microprocessor, the operation of the display, the indicator and other circuits power supply.
2) Voltage regulator control circuit
The core components of the voltage regulator control circuit are power module VIPer12A, voltage regulator VZ, switching transformer T, rectifier VD1, filter capacitor C3.
When the utility voltage rises or the load becomes lighter caused by the switching power supply output voltage rises, the voltage rises at both ends of C3 so that VZ breakdown conduction degree is strengthened, the error voltage provided by R2 for IC1 ③ foot rises, and is processed by the internal circuitry of IC1 so that the switching tube conduction time is shortened, the energy stored in T decreases, and the output voltage of the switching power supply decreases to the normal value. Conversely, the voltage regulator control process is reversed. Therefore, the control of the circuit can ensure that the output voltage of the switching power supply is not affected by the utility power and the load, and realise the regulating control.
3) Undervoltage protection
When VD2 or C2 breaks down so that the voltage above 14.5V cannot be established at both ends of C2 at the instant of switching on, the circuit inside IC1 cannot be started; if VD1, VD2 opens or T abnormally provides a voltage lower than 8V for both ends of C2, the undervoltage protection circuit inside IC1 is operated, which avoids switching tubes being damaged due to insufficient excitation. In addition, over-voltage, over-current and over-temperature protection circuits are also provided inside IC1.
