Tasks and examples of STABILIZER

STABILIZER

1. What is the relative change in voltage at the output of the parametric stabilizer, if the current of the Zener diode has changed by 2 mA, Ust = 8 V, Rdif = 16 Ohm?

Decision:


2. Voltage u = Um (1.5 - 2t / T) B is supplied to a chain of series-connected resistors R = 200 Ohm and Zener diode КС182. Determine the current in the circuit for t = 0.2T, if the differential resistance of the Zener diode Rн = 30 Ohm, Um = 12 V.


Decision:
i = (u - Ust) / (R + Rn)
U (0,2T) = 1,1Um
i (0,2T) = (14 - 8,2) / 230 = 0,025 A




3. Draw a characteristic of the Zener diode with the parameters:
Ust = 12 V, Ist min = 3 mA, Rdif = 25 Ohm
Is max max = 50 mA.

Decision:
∆Ist = Ist max - Ist min = 50 - 3 = 47 mA
∆ Ust = ∆Ist • Rdif = 0.047 • 25 = 1.175 V
Ust min = Ust - Δ Ust / 2 = 11.42 V
Ust max = Ust + ∆ Ust / 2 = 12.59 V

We build the current-voltage characteristics of the Zener diode as shown in the figure.


4. For the stabilizer circuit, the zener diode has the parameters:
Ust = 20 V, Ist min = 1 mA, Rdif = 40 Ohm, Ist max = 71 mA. Determine the current I in the circuit in a graphical way, if In = 20 mA:


Decision:
I = Ist + In
∆Ist = Ist max - Ist min = 71 - 1 = 70 mA
∆ Ust = ∆Ist • Rdif = 0.07 • 40 = 2.8 V
Ust min = Ust - ∆Ust / 2 = 18.6 V
Ust max = Ust + ∆Ust / 2 = 21.4 V

We build the current-voltage characteristics of the zener diode, the voltage-current characteristics of the resistor. We summarize the CVC-ki. Graphically determine the current unbranched part of the circuit.
I = 55 mA


5. To stabilize the voltage in the load Rn = 2 kΩ, a parametric voltage regulator is used. Zener diode has parameters:
Ismin = 1 mA, Ismamax = 23 mA, Rdif = 30 Ohm; the rated output voltage is 11 V, the input voltage is 22 V.
Define Kst and Rbal.


Decision:


6. Determine the voltage at the input of the stabilizer. Options
Zener diode: Ust = 12 V, Ist min = 5 mA, Ist max = 35 mA, Rdif = 20 Ohm
Rbal = 800 Ohm, Rn = ∞.


Decision:
current through the stabilizer


Since the zener diode and the ballast are connected in series in a circuit,


According to the second law Kirchhoff:


7. Determine U2 in the voltage regulator, if U1 = 16 V, R1 = 300 Ohm,
R2 = 1.2 kΩ, Umin min = 12 V, Rst = 15 Ohms.
Note: solve the problem by an analytical method, using a Zener diode equivalent circuit (source emf E = Ust, connected in series with the resistor Rst).



Decision:
Draw the equivalent circuit stabilizer


We use the method of two nodes:

U2 = 12.2 V

8. Periodic voltage u varies according to the law u (t) = 24 (1 - 2t / T), where T is the period. Voltage stabilization of the Zener diode 8 V. R1 = R2 = 1 kΩ.
Build a graph of voltage at the output.
Diode and Zener diode considered ideal.


Decision:
In the positive half-period, the diode VD2 is closed. The voltage Uout at t = 0 will be equal to the stabilization voltage. From the moment of time
t = T / 3 to T / 2 varies from 8 V to zero.
In the negative half-period, the diode VD2 is open. When the branch with zener diodes is disconnected, the voltage across resistor R2 varies from zero (at t = T / 2) to –12 V, at t = T. Connecting the branch with zener diodes limits the output voltage to –8 V.