Portable thyristor charger circuit

The charger introduced in this article directly uses 220V AC mains power. Through the control of the trigger circuit, its output voltage can be adjusted from 0V. It is suitable for charging 12V-220V batteries (packs). 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. All the way is current-limited by resistor R1 and voltage-stabilized by zener diode DW. , delivering about 18V trapezoidal wave synchronous regulated power supply, 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 channel sends out 12V stable voltage through the three-terminal voltage stabilizing integrated circuit IC1 AN7812 The working power supply of the trapezoidal wave synchronous regulated power supply IC2 is composed of IC2 NE555 and R2, R3, RP, C1, C2 and other components. The oscillation period is fixed at less than 10ms and can only change the output rectangular wave duty cycle. The steady-state oscillator, R4, and pulse transformer T2 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°. Adjusting the potentiometer RP can output trigger pulses with different trigger angles, thereby achieving the purpose of controlling the thyristor VS conduction angle. Experiments have proved that the pulse output by this trigger circuit is The width 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 reliably conduct. The main control circuit is composed of the fuse FU, the ammeter and the can. It consists of a 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 the VS with pulses of different pulse widths. Adjusting RP can meet different charging currents or voltages. Charging different batteries (packs). See the table below for component selection and component list. No. Name Model Quantity R1 Metal film resistor 1K/0.5W 1 R2 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/0.5 W 1 VS One-way 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 homemade pulse transformer (see text after the table) 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 made of the same The wire diameter is 200 turns of enameled wire, and all resistors are metal film resistors. RP uses WXD3-13 multi-turn potentiometer, VS uses 10A unidirectional thyristor, and 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.