Portable thyristor charger circuit diagram

working principle

　　The working principle of the circuit is shown in Figure 1. It consists of three parts: power circuit, trigger circuit and main control circuit. After the 220V mains power is stepped down by the power switch S-S' and the power transformer T1, it is rectified by a full-wave rectifier circuit composed of diodes VD1-VD4 and becomes a pulsating DC power supply. One channel is current limited by resistor R1 and stabilized by voltage stabilizing diode DW, and delivers a trapezoidal wave synchronous regulated power supply of about 18V, which serves as the power supply for the RC delay link of the astable oscillator composed of the time base integrated circuit NE555 and its peripheral components; the other All the way through the three-terminal voltage stabilizing integrated circuit IC1 AN7812, a 12V stable trapezoidal wave synchronous voltage stabilizing power supply IC2 is sent out. The trigger circuit is composed of IC2 NE555 and R2, R3, RP, C1, C2 and other components. The oscillation period is less than 10ms and is fixed. It can only change the output rectangular wave duty cycle of the astable oscillator, R4 and pulse transformer T2 to form the trigger. pulse. The reason why the oscillator uses two synchronous regulated power supplies of 18V and 12V is to increase the duty cycle of the output rectangular wave, that is, to increase the phase shift range of the trigger pulse. The phase shift range of this trigger circuit is greater than 120°. By adjusting the potentiometer RP, trigger pulses with different trigger angles can be output, thereby achieving the purpose of controlling the thyristor VS conduction angle.

　　Experiments have shown that the width of the pulse output by this trigger circuit is several times larger than the pulse output by any trigger circuit composed of a single-junction transistor , and it can reliably trigger the back electromotive force load and the thyristor in the large inductance load circuit to conduct reliably.

　　The main control circuit is composed of fuse FU, ammeter and thyristor VS. After connecting the battery or battery (pack) to be charged, the thyristor VS gets a trigger pulse and controls the conduction angle of VS with pulses of different pulse widths. , adjusting RP can satisfy the charging of batteries (packs) with different charging currents or voltages.

　　Component selection and production

　　See the table below for the component list.

　　No. Name Model Quantity

　　R1 metal film resistor 1K/0.5W 1

　　R2 metal film resistor 1K 1

　　R3 metal film resistor 30Ω 1

　　R4 metal film resistor 110Ω 1

　　RP multi-turn potentiometer 2.2K WXD3-13 type 1

　　C1 electrolytic capacitor 2.2u/16V 1

　　C2 polyester capacitor 0.01u 1

　　C3, C4 electrolytic capacitor 220u/25V 2

　　VD1-VD7 rectifier diode IN4004 7

　　VDW Zener diode 18V/0.5W 1

　　VS unidirectional thyristor 10A/100V 1

　　IC1 three-terminal voltage regulator AN7812 1

　　IC2 time base circuit NE555 1

　　FU1, FU2 fuse 8A 2

　　T1 power transformer 24V/5W 1

　　T2 pulse transformer homemade 1

　　A DC ammeter 10A 1

　　The power transformer T1 uses a transformer with a primary voltage of 220V, a secondary voltage of 24V, and a power of 5W. T2 uses a MX2000GL22X13 magnetic tank. The primary L1 is wound with 100 turns of Φ=0.17mm high-strength enameled wire, and the secondary L2 is wound with the same diameter enameled wire. 200 turns. All resistors use metal film resistors . RP uses WXD3-13 multi-turn potentiometer, and VS uses 10A unidirectional thyristor . The withstand voltage is only greater than 100V. A larger radiator should be added to facilitate long-term operation. The charging current of the charged battery should be less than 8A.