Variable Voltage and Current Power Supply Circuit Using LM1458

This is another design for power supply that can build or based on LM1458. This is called variable voltage and current power supply. It is a once of regulated power supply. This figure below is shown the circuit;


The operation of this circuit is the power transformer requires an additional winding to supply the op-amps with a bipolar voltage (+/- 8 volts), and the negative voltage is also used to generate a reference voltage below ground so that the output voltage can be adjusted all the way down to 0. Current limiting is accomplished by sensing the voltage drop across a small resistor placed in series with the negative supply line. As the current increases, the voltage at the wiper of the 500 ohm pot rises until it becomes equal or slightly more positive than the voltage at the (+) input of the op amp.

Current limiting range is about 0 - 3 amps with components shown. The TIP32 and 2N3055 pass transistors should be mounted on suitable heat sinks and the 0.2 ohm current sensing resistor should be rated at 2 watts or more. The op amp output then moves negative and reduces the voltage at the base of the 2N3053 transistor which in turn reduces the current to the 2N3055 pass transistor so that the current stays at a constant level even if the supply is shorted. The heat produced by the pass transistor will be the product of the difference in voltage between the input and output, and the load current.

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APD Bias Supply and Current Monitor

This circuit is consists of two circuit but in the figure this circuit is combines. This is the figure of the circuit.

The programmable APD bias supply is as before, except that feedback comes via A2. A2, sensing after the 1kW current shunt, isolates the R1-R2 path loading, preventing it from influencing the shunt’s voltage drop. A2’s action also insures tight output regulation, despite the current shunt’s presence. The current monitor, measures across the 1kW current shunt, presenting its output in Q1’s drain line. As shown, the output has about 1kW output impedance, although either of the circuit output options may be employed.

When considering circuit operation, note that both amplifiers are powered by the charge pump’s high voltage output, with their V– pin returned to the “2/3 VOUT” point. This biasing permits the amplifiers to process high voltage signals, although the voltage across them never exceeds 30V.

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