Selection of DC Stabilized Power Supply Components
Let's take a look at how to design a silicon regulator power supply when the load voltage UR1 and load current IR1 are known.
(1) Primary selection regulator tube D1
In general, you can preliminarily select the regulator tube D1 according to UD1=UR2 and ID1≈(IR2)max. If the load may be open, you should choose (ID1)max≈(2－3)(IR2)max, which is Because all the current will flow through D1 when it is loaded, so ID1 should be selected appropriately larger. .
(2) Select the input voltage
Generally, you can choose UI=(2－3)UR2
(3) Select the current limiting resistor R1
R1=(UI－UR2)/(ID1+IR2)
However, two extreme cases need to be considered:
When UI is the largest and the load is open (that is, IR2=0), the current flowing through D1 is the largest. In order not to exceed the maximum allowable current (ID1) max of D1, there needs to be a large enough current resistance, otherwise D1 will be burned. Then R1 needs to satisfy:
R1>((UI)max-UR2)/ID1)max
When UI is the smallest and the load current is the largest, the current flowing through D1 is the smallest. In order to ensure that D1 can work in the breakdown region to stabilize the voltage at this time, a certain current must flow through D1, generally 5mA-10mA. Then R1 needs to satisfy:
R1<((UI)min-UR2)/(ID1+(IR2)max)
The value of the current limiting resistor R1 should be selected within the range of the above two formulas.
(4) Check circuit stability
The stability of the circuit needs to be determined according to the requirements of the actual circuit. If the stability is not enough, R1 and UI can be appropriately increased, and a Zener tube with a relatively small dynamic resistance r can also be selected.
