TPR constant voltage constant current high-precision DC stabilized power supply analysis - News - Global IC Trade Starts Here.

First, the working principle is divided into four major blocks: series DC regulated power supply, including adjustable amplification and constant voltage circuit; constant current regulation and constant voltage constant current conversion display part; reference regulated power supply; transformer secondary AC voltage automatic adjustment Circuit.
The whole circuit diagram is shown in the figure.
1. Series DC regulated power supply and constant voltage circuit. Mainly composed of adjustment tubes T1, T2, T10, T11, op amp IC1 and P1, P2 voltage adjustment potentiometer, reference voltage composed of constant voltage circuit, control T2 base voltage, change the conduction level of the adjustment tube, ensure the voltage regulator circuit Normal work. Here, P1 and P2 are used as coarse adjustment and fine adjustment potentiometer to adjust the voltage. The non-inverting terminal of IC1 is connected with the reference voltage and the adjustment voltage, and compared with the sampling voltage of the inverting terminal to change the current of the adjustment tube.
2. Constant current circuit - also known as current limiting circuit. That is, when the predetermined current limit is adjusted, the output current remains unchanged, and the output voltage decreases proportionally as the load further increases. The constant current circuit consists of an operational amplifier IC2 and a sampling resistor of 0.15Ω, plus a constant voltage and constant current conversion display circuit. The IC2 non-inverting terminal obtains the reference voltage from the P3 current adjustment potentiometer and the reference power supply regulation W1, and the inverting terminal is connected to the front end of the sampling resistor of 0.15 Ω through the resistance 1kΩ. When the sampling voltage is greater than the reference voltage, the output voltage of IC2 drops, so that the Vb of T2 drops, the output voltage decreases, but the output current remains unchanged, achieving the purpose of current limiting. At constant voltage, T8 turns on and T9 turns off, so the constant voltage (CV) green light is on, and the constant current (CC) red light is off. Because the IC2 output is high at constant voltage, T8 is made through the Zener diode DZ (6V). Turn on, green light is on. When the current limiting protection acts as a protection, the output of IC2 is 0. At this time, Vb of T2 drops to 0 through the diode voltage, and the regulating tube is turned off.
3. Reference regulated power supply. It consists of TL431 and 78L12, T3. The TL431 not only performs standard voltage, but also plays a role in comparing the error voltage and controlling the T3 tube. The internal reference voltage of the TL431 is 2.5V. The sampling voltage is actually compared with the 2.5V reference voltage of the TL431. The TL431 cathode voltage is changed to adjust the conduction of T3. In addition, the base voltage of T3 is regulated by 78L12 and then passed through the resistor 1kΩ to the base to make the output +15V stable. The output +15V is mainly used in the IC1 and IC2 integrated op amp power supply and the reference voltage of constant voltage and constant current circuits. The reference voltage of the AC voltage switching circuit. +6V is connected to the output positive of the main regulated power supply.
As can be seen from the figure, the high precision of the TPR-3003 DC regulated power supply mainly uses a reference power supply composed of dual high-precision voltage regulators.
4. The AC power supply automatically switches the circuit. Another characteristic of the DC adjustable power supply is that in actual operation, as the input-output voltage difference increases, the output current Io decreases and the junction temperature of the adjustment tube rises, thereby increasing the power consumption of the adjustment tube. The output coil tap of the manual switching transformer is generally used to achieve the purpose of reducing the differential pressure. This circuit uses a detection circuit composed of T4, T5, T6, and T7 transistors to automatically switch the AC voltage. The secondary output of the transformer is 14V, 24V, 32V three kinds of AC voltage, and the general detection is automatically switched at the output of the DC power supply +10V and +20V. The base of T6 is connected to the reference voltage through a 45kΩ resistor, the reference voltage is provided by the reference voltage, and the other of the base is sampled by the 18kΩ resistor and a series diode connected to the output negative pole of the main power supply. When the output voltage is lower than 10V, T6 is turned on, T7 is turned off, relay J2 is released, and the normally closed contact is connected to the input voltage of the AC 14V low gear. When the output DC voltage reaches 10V, the negative voltage of T6 base is cut off. T7 is turned on, relay J2 is closed, and normally closed contact is turned on at 24  high gear. When the total output power of the Zener tube reaches +20V, T5 is cut off, T4 is turned on, J1 is closed, the J1 normally open contact is turned on, and the input voltage of the adjusting tube is switched to the third high gear 32. The TPR adjustable power supply can always guarantee a certain voltage difference when the voltage is adjusted, and it is mainly obtained by automatically adjusting the AC voltage.

Second, the operation method must be used before the instrument is limited current calibration, after the power is turned on to adjust the voltage to the required voltage value, and then turn the power adjustment knob to the constant current (CC) indicator light, it means the machine is in a constant current state. Short-circuit a short-circuit line to the + and - terminals of the power supply output, adjust the current knob to the current limit value. After setting, do not change the current knob position, remove the short-circuit line, and enter the working state.

Third, common faults and normal maintenance 1. The voltage adjustment knob does not work, mainly because the 6V regulator tube in the circuit of the reference regulated power supply breaks down or turns off, causing the voltage adjustment potentiometer to have no sampling voltage. The 6V regulator tube breaks down, the voltage is indicated to the maximum, and the voltage regulator disconnection voltage is indicated to the minimum.
2. The current regulator does not work when the power supply output + and - terminals are short-circuited. In this case, first check if the IC2 op amp is normal, and then check the reference voltage. In this regulated power supply, the reference voltage is the most important. It is the primary inspection object. It is usually caused by the W1 trimming potentiometer on the printed board. If the P3 potentiometer is unsoldered, the current output will reach the maximum value.
3. Turn the potentiometer P3 to the left and keep it in the constant current state. The red indicator light CC should be on, and the green indicator light CC should be off. At this time, the voltage indication is zero. If the voltage indication is not zero, the IC2 op amp integrated block is zeroed. The problem, if the IC2 op amp 1 pin and 4 pin shorted, the voltage display can be zero, this phenomenon is mainly caused by the replacement of the new op amp after the IC2 op amp is damaged. 