Battery charger 1,2-15 volts 0,1-10 Ah. Encyclopedia of radio electronics and electrical engineering

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

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The proposed device, which allows you to charge any batteries and batteries with a voltage of 1,2 to 15 V and a nominal capacity of 0,1 to 10 Ah, can be used not only in an amateur radio workshop, but also in organizations that operate electronic equipment with autonomous food.

The device is a current stabilizer using frequency-pulse regulation, which made it possible to do without a bulky heat sink for the control transistor.

Main Specifications

Maximum output voltage, V ........ 15
Load current, mA .............10, 25, 50, 100, 1000
The instability of the output current when the voltage on the load changes from 0 to 15 V,%.................................................. 5
Efficiency at a load current of 1000 mA and a voltage of 15 V, % .............................................. 60
Output current instability, %, when the supply voltage changes
by +15% ............................................... .......one
by -15% ............................................... .......3
Output current ripple factor, % ...10

The schematic diagram of the device is shown in fig. 1. It is formed by a network transformer T1, a rectifier VD1 with a filter capacitor C1, a parametric stabilizer R1VD2, a multivibrator on transistors VT2 and VT3 with a current amplifier on a transistor VT4, a composite transistor VT5VT6 operating in switching mode, an inductive-capacitive filter L1C3, a switching diode VD4 . Resistors R13-R17, R7, Zener diode VD3 and transistor VT1 - negative feedback circuit.

Fig. 1

 The device works as follows. When the power is turned on, the capacitor C3 is discharged, the transistor VT1 is closed, the multivibrator generates pulses that follow at a frequency of about 20 kHz. Amplified by the transistor VT4, the multivibrator pulses open the composite transistor VT5VT6. When this transistor is open, current flows through it, inductor L1, load GB1 connected to connectors X1 and X2, resistors P13-R17 (depending on the charging current limit selected by switch SA1) and capacitor C3. When the transistor VT4 is closed, the self-induction current of the inductor L1 closes through the switching diode VD4, capacitor C3, load and resistors R13-R17.

After several pulses of the multivibrator, the voltage drop across the resistors R13-R17 reaches 0,65 V, the transistor VT1 opens and the multivibrator stops working. In steady state, when the load current decreases, the voltage drop across the resistors R13-R17 decreases, the transistor VT1 closes and the multivibrator generates one pulse with a duration of 20 μs. This is followed by a pause lasting from 0,045 to 4,5 ms (depending on the value of the load current) - and the cycle repeats.

Zener diode VD3 and resistor R7 serve to protect the transistor VT1 in case of a short circuit at the output of the device.

Setting up the device comes down to a careful selection of resistors R13-R17, which determine the charging currents of cells or batteries.

Inductor L1, containing 250 turns of PEV-1 0,8 wire, is wound on a Sh10x10 magnetic circuit made of 2000NM ferrite. Textolite pads 1,2 mm thick are inserted between its W-shaped halves.

Network, transformer T1 is made on the magnetic circuit Ш20х20. Winding I contains 2000 turns of wire PEV-1 0,25, winding II - 300 turns of wire PEV-1 0,75.

Most of the parts of the described charger are mounted on a printed circuit board (Fig. 2) made of foil fiberglass 2 mm thick. Transistor VT6 is installed on a heat sink with an area of ​​25 sq. cm, transistor VT5 is pressed against it. The board provides space for resistors connected in parallel with resistors R13-R17 when adjusting the required charging currents.

Fig. 2

PS According to one of the Radio magazine reviewers, the VD3 zener diode is not needed - it will never open, including in the event of a short circuit in the output circuit, since the voltage at the emitter junction of the VT1 transistor cannot be more than 3,3 V.

Authors: V. Dymont, Yu. Pashkovsky, Minsk; Publication: cxem.net

See other articles Section Chargers, batteries, galvanic cells.

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