Description of the current regulator circuit, as a universal charger

  • Dec 26, 2019
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In amateur practice it is often necessary to have not only a stable voltage, but current. For example, in devices for charging batteries, or when constructing circuits short circuit protection, is required to limit the maximum possible load current at a certain level it.

Presented here is a simple circuit is a current stabilizer. If you change the settings and use the (selection) of various electronic components, on the basis of this scheme, you can collect a current regulator with the required characteristics.

Driving current regulator
Driving current regulator

When these elements in the diagram it is possible to adjust the stability of the output current value to 30 mA. This current strength is sufficient, for example, for charging rechargeable batteries of small capacity up to 300 mA / h. It may be disk type batteries STS21, STS32, or D-0,1 - D-0,55, battery type 7D-0.1 and even galvanic elements - "finger" or other battery voltage of 1.5... 4.5 volt.

About battery regeneration opportunities, there are many different opinions and available specialized information. But in this article, this issue will not be discussed in detail, since it requires a separate description and will be discussed in the following publications.

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Required charging current set by variable resistor R5. Installed current value will be the same throughout the charging time. And even when a short-circuit output terminals circuit output current value will remain within the set value you.

The circuit is powered by a low-power transformer to the secondary winding voltage of 10-14 volts. This voltage depends on the desired output power supply voltage.

Rectifier diodes may be of the type KD226, LED type AL102, AL307A-G or any similar. Transistors in this case can be any low-power supply structure of n-p-n, for example - KT315, KT3102, S945, VS549.

All resistors type MLT-0,125, variable resistor R5 power of 1 Watt.
Change limits adjustment of the output current value can be the selection of nominal resistor R4.

If necessary, get more stable current value to be applied items, calculated respectively at high power. For example, the transistor T2 can be applied KT805, KT815, and resistor R5 supply wire. In this case, all the other resistors better to use 0.25 watts or higher order power.

Because of its simplicity, the presented scheme leaves scope for improvements and to build on its basis, more sophisticated and versatile device.

This scheme may find application not only as a battery charger. It can also be used as a power supply with short-circuit protection and overcurrent.

For example, during testing and configuring thin devices, without the risk of exceeding the maximum allowable current draw values. In this case, the required input voltage of the circuit can be fed from a DC voltage source, e.g., from laboratory supply unit (deletion of the rectifier circuit VDS1).