Component Selection of Transistor Voltage Stabilizer
The process of selecting components for this circuit is similar to that of a parallel voltage regulator circuit using silicon voltage regulators, mainly considering the following aspects.
(1) Preliminary selection of adjustment tube T1 and voltage regulator tube D1
When selecting the adjustment tube T1, the main consideration is that its rated current ICM should be greater than the output current IO to ensure that the adjustment tube will not be damaged due to excessive current when the load is open circuit. In addition, to ensure that the adjustment tube has a good adjustment effect, it is also required to have a high beta value and low leakage current. When choosing the voltage regulator D1, the main consideration is that the sum of its stable voltage and the T1 emitter junction voltage should be equal to the output voltage.
(2) Select input voltage
To ensure the efficiency of the regulated power supply, the input voltage should generally not be selected too high, and should not exceed 2 UI.
(3) Select current limiting resistor R2
For parallel voltage regulation circuits, the limiting resistor R2 is the key to the overall performance of the circuit. R2 has a large selection and good voltage stabilization effect, but it consumes a lot of power (because the power consumption of the resistor P=I2R). At the same time, it requires an increase in input voltage, and the efficiency of the power supply is relatively low. The specific calculation method can refer to the third step of selecting components for parallel voltage regulation circuits of silicon voltage regulators.
(4) Check the stability of the circuit
The stability of the entire circuit needs to be determined according to the requirements of the actual circuit. If the stability is not sufficient, R1 and UI can be appropriately increased, and adjustment tubes with larger β values and smaller leakage currents can also be selected.
