High-precision voltage regulator using KTA431 (TL431)

The attached figure is a circuit diagram of a high-precision voltage regulator using a shunt regulator IC. Since negative feedback is introduced into the circuit, a stable output voltage can be obtained.

The output voltage is determined by the ratio of the voltage divider resistors R6 and R7. Vout = Vref × (R6 + R7) / R6, so the output voltage can be set to any value by simply adjusting the ratio of the voltage divider resistors.

Since the regulator uses a PNP transistor as the adjustment tube, the base potential is lower than the input voltage, so the voltage difference between the input and output of the regulator may be lower than the Vce (sat) of the transistor. When the input voltage changes greatly, or even when it is close to the set voltage value, the circuit can still work normally. In order to prevent the parallel voltage regulator IC from causing self-excitation of the circuit, phase compensation measures must be taken in the circuit. Therefore, an RC series circuit is connected between the cathode and base (Ref) of KIA431A. For the series-adjusted regulator, the voltage difference between the input and output is added to the adjustment tube. The product of the voltage difference and the load current is the loss of the transistor. When designing the circuit, be sure not to let the maximum power loss of the transistor exceed the rated power of the transistor, and pay attention to adding a heat sink for heat dissipation.