Discrete component power amplifier circuit diagram

The figure shows the circuit of a power amplifier power supply with superior performance . It has the characteristics of small size, large power and high efficiency.

Working principle: The AC power input is filtered by T1 and divided into two outputs, one of which goes to the step-down transformer T3. A bidirectional thyristor KS is connected in the primary circuit of T3 to change the primary AC power of the transformer T3. The other channel is rectified after being stepped down by capacitor C1, and is stabilized by VD1 to provide DC working voltage to the trigger control circuit. R3, C3, VQ3 and transformer T2 form a relaxation oscillation circuit. R2, R4, VQ1, and VQ2 form a current source to charge capacitor C3 with constant current. When the voltage at both ends of C3 is charged to the breakdown voltage of VQ3, C3 discharges through the emitter and base of VQ3 and the primary coil of transformer T2, and obtains the trigger pulse of the thyristor KS on the secondary side of the transformer T2, controlling the conduction of the thyristor KS. , making transformer T3 work. On the secondary side of transformer T3, the positive and negative symmetrical DC voltage required by the power amplifier is obtained after rectification and filtering. When the voltage across capacitor C3 is discharged to the valley voltage of VQ3, the emitter and base of VQ3 are closed and preparations are made for the charging and discharging of capacitor C3 in the next cycle. R6~R9, VQ4, VD2 and W1 form a voltage comparison amplifier circuit. Adjusting W1 can change the output voltage, and control the current of the VQ1 and VQ2 current sources through IC1 to change the charge and discharge time of C3 and control the conduction angle of the thyristor VKS. , thereby changing the primary AC power of transformer T3 and obtaining a constant output voltage on the secondary side, ensuring the instantaneous power of the power amplifier.

Component selection: Transformer T2 is self-made with a 5mm × 5mm E-type iron core. The primary can be wound with 0.15mm acoustic enameled wire for 200 turns, and the secondary can be wound for 135 turns. Transformer T3 can be wound with a 40mm × 60mm iron core. The primary is wound with Φ0.9mm enameled wire for 352 turns, and the secondary is wound with Φ1.26mm enameled wire for 176 turns, with a tap at 88 turns. Other components are shown in the figure.