Power supply with charger for 3-volt devices 70-220 milliamps. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Chargers, batteries, galvanic cells
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The proposed power supply is designed to power 3-volt players, receivers, etc. It allows you to simultaneously charge their batteries (AB). The power supply is built according to a scheme similar to [1]. It provides up to 200mA output current as well as output short circuit protection. When a short circuit occurs at the output of the power supply, the short circuit current does not exceed 50 mA, while the VD13 LED goes out.
The charger provides battery charging with a current adjustable from 70 to 220 mA in 10 mA steps. The required charging current is selected by the respective switches SA2...SA5. Diode VD11 is included in the circuit to increase the stability of the output current. When the battery is turned on for charging, the VD10 LED lights up.
Rice. 1. Schematic diagram of the power supply and charger (click to enlarge)
Instead of transistors VT3, VT5, transistors from the KT835B, KT816 series are suitable. Transistor VT3 must be selected with a gain P21E of at least 25. It must be installed on a heat sink with an effective area of at least 25 cm2. VT5 is mounted on a small radiator (flag).
MP20, MP21, MP25, MP26, it is desirable to choose with G121e at least 30. Transistor VT4 - any of the series KT361, KT3107 with a permissible collector-emitter voltage of at least 20 V. Diodes VD5, VD6, VD8, VD9, VD11 - any silicon. LEDs - from the AL307 series, with VD10 - green, VD13 - red.
Setting up the device consists in selecting resistors R7, R12, R14, R16, R18 to obtain the required charging current. Elements R9, R10, SA4.1, SA5.1 can be excluded from the circuit, but then you will have to install VT5 on a radiator with a larger area.
Literature
- B. Ivanov. Power sources. - To help the radio amateur, 1983, N84.
Author: A. Pshenitsyn, Ertsevo village, Arkhangelsk region; Publication: cxem.net
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