The article states how to make a variable stabilized zener diode circuit using transistors, whose voltage is variable, and the zener voltage can be adjusted as per preference.
As anyone would understand the voltage drop across a zener diode is reliant on the current getting through the diode. Consequently, based on the sort and power of the unit, there could be pretty recognizable change from the minimal zener voltage.
This is often a difficulty, specially in circuits in which a stable d.c. voltage is usually crucial. Probably the most rational method of dealing with the thing is to maintain the current in the diode constant in order that the zener voltage is unable to adjust.
To be able that the load hooked up to the zener diode takes in a constant current, the zener may be furnished by technique of a current source. Then this current via the current source is built based upon the zener voltage.
Within our circuit we make use of a zener diode having a zener voltage of Six V. Different zener values could possibly be applied if resistors R1 . . . R4 are altered to match yet another value. Maximum input voltage is principally restricted to the power which may be dissipated by T1 and T2. The d.c. input voltage need to overcome minimum up to the total of the zener voltages of D1 and D2.
The current source composed of T1, R1 and D1 guarantee that the current via D2 continues to be constant Transistor T2, resistor R2 and zener diode D2 consequently shape a current source intended for zener D1 in order that the current through this diode furthermore remains constant.
Diode D3 and also the voltage divider, composed of R3 and R4, guarantee that this particular circuit will be able to ‘start’ (in the same way a thyristor made of transistors). When the voltage is started up a current moves via D3 leading to T2 (and thus T1) to conduct.
The importance of R3 needs to be picked in a way that diode D3 obstructs the moment the voltage over the zener diode get regulated ans stable. Therefore attention has to be considered that the voltage at the anode of D3 is much less compared to zener voltage of D2 in addition the diode’s unique voltage drop of 0.6 V.
This is certainly deﬁned by this formula: R4/(R3+R4) x Ui < UD2 + 0.6V. Likewise R3 the voltage in the junction of R3 and R4 has to be a minimum of 1.2 V, or else T2 would not run.
The circuit diagram for the proposed variable stabilized zener diode circuit can be visualized below: