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High-Power Car Battery Eliminator(2N3773)

2014-11-28 11:25  
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This article briefly describes the High-Power Car Battery Eliminator (2N3773). This principle is easy to understand, but also very practical. Depth understanding of circuit elements, you can better grasp this principle. In this circuit, you can learn about and purchase these components: 2N3773.

To operate car audio (or video) system from household 230V AC mains supply, you need a DC adaptor. DC adapters available in the market are generally costly and supply an unregulated DC. To overcome these problems, an economical and reliable circuit of a high-power, regulated DC adaptor using reasonably low number of components is presented here. Transformer X1 steps down 230V AC mains supply to around 30V AC, which is then rectified by a bridge rectifier comprising 5406 rectifier diodes D1 through D4. The rectified pulsating DC is smoothed by two 4700μF filter capacitors C1 and C2.

Figure:1 Circuit diagram

Figure 1 Circuit diagram

The next part of the circuit is a series-transistor regulator circuit realised using high-power transistor 2N3773 (T1). Fixed-base reference for the transistor is taken from the output pin of 3-pin regulator IC1 (LM 7806). The normal output of IC1 is raised to about 13.8 volts by suitably biasing its common terminal by components ZD1 and LED1. This simple arrangement provides good, stable voltage reference at a low cost. LED1 also works as an output indicator. Finally, a crowbar-type protection circuit is added. If the output voltage exceeds 15V due to some reason such as component failure, theSCRfires because of the breakdown of zener ZD2.

OnceSCRfires, it presents a short-circuit across the unregulated DC supply, resulting in the blowing of fuse F1 instantly. This offers guaranteed protection to the equipment connected and to the circuit itself. This circuit can be assembled using a small general-purposePCB. A good-quality heat-sink is required for transistor T1. Enclose the complete circuit in a ready made big adapter cabinet as shown in the figure.



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