0V～100V/1A high voltage adjustable regulated power supply

Due to the needs of scientific research, we need to build a 0V~100V/1A continuously adjustable regulated power supply, which is used to power an approximately constant current load. The switching power supply shown in the figure is designed and produced, as can be seen from the circuit in the figure. It is a pulse frequency modulated switching power supply. The switching tube is borne by the high-voltage and high-power field effect tube Q1. It forms the main circuit with L1, D1 and C1, which is the "series switching converter". IC1 (NE555) forms a voltage-controlled oscillator, and the pulses it generates are coupled by a 0.47μF capacitor to drive the switching tube Q1. IC2 is a voltage comparator made of 1/4 LM324 operational amplifier. The potentiometer P1 takes out a part of the output voltage and compares it with the 6V reference voltage. When the output voltage is higher than the reference voltage, the operational amplifier outputs a high voltage, making the NE555 The oscillation frequency decreases and the on-off frequency of Q1 slows down, causing the charging voltage (i.e. output voltage) across C1 to decrease. On the contrary, if the output voltage is higher than the reference voltage, the on-off frequency of Q1 is accelerated, causing the output voltage to rise, thereby achieving the purpose of voltage stabilization. Potentiometer P1 is also an output voltage regulator, which can continuously adjust the output from 0V to 100v. Because Q1 works in a switching state. So its power consumption is very small.

There is another very important part in the circuit. It's short circuit protection. Because the load connected during the experiment cannot be completely constant, the current may sometimes exceed 1A, which may easily cause damage to Q1. If the output current exceeds 1A, the voltage drop across R1 (plus the internal resistance of the ammeter) will exceed 0.7V, and Q2 will suddenly turn on. Its collector current flows through relay J. Its pull-in causes the normally closed contact J1 to open. Immediately cut off the AC power supply to T1. At the same time, the normally open contact J2 is closed and the relay J is locked. After the fault is eliminated, it can be started manually again. To keep relay J locked, the short-circuit protection part cannot be powered off, so T2 is working at any time and is not subject to K1. After rectification, the 9V AC output of T2 not only supplies Q2, but also supplies a 6V small fan to cool Q1.

The output of the other winding of T1. After two voltage doubler rectifiers, it becomes two sets of ±15V power supply. To supply IC1 and IC2 two integrated blocks. L1 is a homemade inductor, made of Φ0.5mm enameled wire wound 120 turns on a 20mm diameter hollow paper tube.