Many integrated voltage regulators deliver an output current of 1.5 A. But it is often necessary to obtain high power output, while maintaining the quality of output voltage stabilization.
There are various ways of solving this problem. One of them is a parallel connection of several identical integral stabilisers. But due to the inevitable variation * process variation separate stabilizers their output voltages are always a few different from each other.
In parallel operation stabilizers these differences lead to uneven the distribution of the total load current between the stabilizers: some of them have maximum output current, while the other is a negligible or even are in a disconnected state.
To ensure uniform current distribution requires the use of quite complex leveling devices.
More preferably, the external power transistors, quite simply combine with integral stabilizer and providing substantial the increase of the output current of the power source.
One such source with integral stabilizer 7805 (U1), shown in Fig. 5.73, contains the following components: electrolytic capacitor C1 is 1000 μf, 35 In; diodes VD1-VD4 -50 V, 8 A; a resistor R1 - 6 0m, 0.5 W; the transistor VT - 2N 3792; fuse F1 is 0.5 A.
The transformer has an output voltage of 6.3 V and a rated current of 6 A.
Please note that in order to increase the output power used p-n-p transistor, the collector of which is connected to the output of the power source, and the emitter is connected to the output of the rectifier.
The base of the transistor should be connected to the input terminal of the stabilizer, and the resistor R1 connected between the emitter and the base of the transistor, provides the normal operation of the latter.
When you create a practical device, transistor, and stabilizer, with a suitable type of heat sink.
Author: R. Treister