Automatic starter charger. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Automatic starter charger. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Chargers, batteries, galvanic cells

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The device (Fig. 1) is an automatic thyristor rectifier that provides battery charging in a mode close to optimal.

(click to enlarge)

A feature of the device is that the thyristors are installed on one common radiator, which simplifies and reduces the cost of construction. The device is powered from the network through a transformer T1.

The battery charge circuit is connected to the secondary winding T1 through thyristors VS1 and VS2. The diode VD1 and the divider R1-R2 form pulses of positive polarity with a mains frequency (50 Hz), which are fed to the input of the element DD1.1, which implements the EXCLUSIVE OR logic function. Diode VD5 limits the voltage level at input DD1.1 The second input DD1.1 is connected to a common wire, so it serves as a pulse repeater, and capacitor C1 turns the repeater into a Schmitt trigger, which generates output pulses with steep fronts. Thus, rectangular pulses of positive polarity appear at the output of DD1.1 if a positive half-wave of the mains voltage from winding II T1 arrives at the anode of the diode VD1.

A node consisting of elements VD2, R3, R4, VD6, DD1.2, C2 works similarly.

Rectangular pulses of positive polarity appear at the output of DD1.2 if a positive half-wave of the mains voltage from the winding III T2 is supplied to the anode of the VD1 diode.

According to the specifications, control pulses must be applied to the thyristor when a forward voltage is applied to it.

This synchronization scheme allows you to receive opening pulses on the control electrode of thyristors,

only if a direct voltage is acting on it. A high level ("1") from the output of DD1.1 (DD1.2) is transmitted through the inverter DD2.2 (DD2.1), as a result of which the level "2" enters the base of the transistor VT1 (VT0) and it opens.

That is, when a positive half-wave of a sinusoidal voltage acts on the IIT1 winding, and a negative half-wave acts on the winding III, the transistor VT2 is open and VT1 is closed.

To reliably open thyristors VS1 and VS2, their control electrodes are pulsed with a frequency of several kilohertz, generated by a generator based on logic elements DD1.3 and DD1.4.

A voltage comparator is made on the DA1 chip, the inputs of which receive voltage from the battery. The reference voltage is created by the Zener diode VD8.

Part of the battery voltage is removed from the R7 potentiometer slider. If the voltage from R7 is greater (in absolute value) than the voltage from the zener diode, then the output (pin 9) DA2 is a low voltage level. When the voltage from R7 is less than the reference voltage, the DA2 output is high.

Logical elements DD2.1 and DD2.2-3-input matching circuits.

The output signal at the output DD2.1 (DD2.2) appears only when levels 1 are simultaneously present at its inputs from the logic element DD1.1 (DD1.2), the RF generator DD1.4 and the comparator DA1 In this case, to the base of the transistor VT2 (VT1) receives opening pulses, which, after amplification, are transmitted through a pulse transformer. T3 (T2) to the control electrode of the thyristor VS2 (VS1).

As the battery charges, the pulse duty cycle (the ratio of the period to the pulse duration) changes, and the thyristors remain closed for more and more time. When fully charged, the charge current drops to a minimum and is approximately equal to the battery self-discharge current.

The operation of the device is controlled by the devices RA1 and PV1, which measure the charge current and voltage at the battery terminals, respectively.

The logical part of the device is powered by an integral stabilizer DA1. Diodes VD3 and VD4 allow you to decouple the synchronization circuits from DC circuits.

Potentiometer R7 using a voltmeter sets the voltage, which corresponds to a fully charged battery.

Pulse transformers T2, T3 - standard type. MIT-4. they can be wound on ferrite rings MH600 K7x4x2,5. Each winding contains 70 turns of PEV wire 0,12 mm.

Authors: V.Kalashnik, V.Chernikov, Voronezh

See other articles Section Chargers, batteries, galvanic cells.

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