High-precision voltage regulator using KTA431 (TL431)

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

The output voltage is determined by the ratio of voltage dividing 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 dividing resistors.

Because the regulator tube of this regulator uses a PNP transistor. The base potential is lower than the input voltage, so the voltage difference between the input and output terminals of the voltage regulator may be lower than the Vce(sat) of the transistor. The input voltage fluctuates greatly. The circuit can still operate normally even close to the set voltage value. In order to prevent the parallel voltage stabilizing IC from causing circuit self-excitation, phase compensation measures must be taken in the circuit. So an RC series circuit was connected between the cathode and base (Ref) of KIA431A. For series regulated regulators. The voltage difference between the input and output terminals is added to the regulating tube. The product of the voltage difference and the load current is the transistor loss. When designing the circuit, be sure to ensure that the maximum power loss of the transistor is not greater than the rated power of the transistor. And pay attention to adding heat sinks for heat dissipation.

In order to prevent the voltage regulator from self-excitation. A 1μF ~ 100μF capacitor should be connected in parallel to the output end of the voltage regulator . Author: Zhang Da