5V regulated power supply circuit diagram with expanded current overvoltage protection

This 5V regulated power supply has the characteristics of low cost, small size, high efficiency, light weight, low ripple, high stability and accuracy, and has current expansion and overvoltage protection devices. It can be used for laboratory circuit experiments and can be used as power supply for solid-state circuits and microprocessors. It can also be used as a power supply for special instruments, meters and other circuits.

working principle

The circuit is shown in the figure. When the power is turned on, the grid voltage of 220V is transformed by transformer T, rectified by bridge rectifier QL, and filtered by capacitor C3, so that the output terminal obtains a stable voltage of 5V. The maximum output current of W7805 is 1.5A. If you want to increase the output current to >1.5A, you need to expand the output current. Here, a high-power transistor VT1 is connected to the periphery of W7805. It uses a parallel current expansion method, that is, pin 1 of W7805 is connected to the base of VT1, and pin 2 of the output terminal W7805 is connected to the base of VT1. The collectors are connected, so that the sum of the two output currents can meet the output current requirement of 1.6~2A. If a larger output current is needed , 2 to 3 high-power transistors can be connected in parallel.

ck="window.open(this.src)" alt="Click to see larger image" />