Diode voltage multiplier

Diode voltage multiplier

1. DIODE VOLTAGE MULTIPLIER By Unsa Shakir

2. What is Voltage Multiplier? A voltage multiplier is an electrical circuit that converts AC electrical power from a lower voltage to a higher DC voltage, typically using a network of capacitors and diodes.

3. Types of Voltage Multiplier Depending on the output voltage, multipliers can be of different types Voltage Doublers Half wave voltage doubler Full wave voltage doubler Voltage Tipplers Voltage Quadrupler

4. Voltage Doubler, Tripler and Quadrupler

5. Voltage Doubler

6. Positive Half-Cycle D 1 conducts D 2 is switched off Capacitor C 1 charges to V m Negative Half-Cycle D 1 is switched off D 2 conducts Capacitor C 2 charges to 2V m V out = V C2 = 2V m Half wave Voltage Doubler

7. 7 Positive Half-Cycle D 1 conducts D 2 is switched off Capacitor C 1 charges to V m Negative Half-Cycle D 1 is switched off D 2 conducts Capacitor C 2 charges to V m Full Wave Voltage Multiplier V out = V C1 + V C2 = 2V m

8. Voltage Tripler

9. Voltage Tripler During first positive half cycle : D iode D 1  is forward biased whereas diodes D 2  and D 3  are reverse biased . Current will flows to the capacitor C 1  and charges it toV m During negative half cycle : Diode D 2  is forward biased whereas diodes D 1  and D 3  are reverse biased. C urrent will flows to the capacitor C 2  and charges it. The capacitor C 2  is charged to twice the peak voltage of the input signal (2V m ). This is because the charge (V m ) stored in the capacitor C 1  is discharged during the negative half cycle .

10. During second positive half cycle : D iode D 3  is forward biased whereas diodes D 1  and D 2  are reverse biased. As a result, the voltage (2V m ) across capacitor C 2  is discharged. This charge will flow to the capacitor C 3  and charges it to the same voltage 2V m . The capacitors C 1  and C 3  are in series and the output voltage is taken across the two series connected capacitors C 1  and C 3 . The voltage across capacitor C 1  is V m  and capacitor C 3  is 2V m . So the total output voltage is equal to the sum of capacitor C 1  voltage and capacitor C 3 voltage i .e . C 1  + C 3  = V m  + 2V m  = 3V m .

11. Voltage Quadrupler

12. Voltage Quadrupler During first positive half cycle : Diode D 1  is forward biased whereas diodes D 2 , D 3  and D4 are reverse biased. C urrent will flows to the capacitor C 1  and charges it to the input voltage I.e. V m . During first negative half cycle : D iode D 2  is forward biased and diodes D 1 , D 3  and D 4  are reverse biased. C urrent will flows to the capacitor C 2  and charges it. The capacitor C 2  is charged to twice the peak voltage of the input signal (2V m ). This is because the charge (V m ) stored in the capacitor C 1  is discharged during the negative half cycle. Therefore, the capacitor C 1  voltage (V m ) and the input voltage (V m ) is added to the capacitor C 2  I.e Capacitor voltage + input voltage = V m  + V m  = 2V m . As a result, the capacitor C 2 charges to 2V m

13. During second positive half cycle : D iode D 3  is forward biased and diodes D 1 , D 2  and D 4  are reverse biased. As a result, the voltage (2V m ) across capacitor C 2  is discharged. This charge will flow to the capacitor C 3  and charges it to the same voltage 2V m . During second negative half cycle : D iodes D 2  and D 4  are forward biased whereas diodes D 1  and D 3  are reverse biased . As a result, the charge (2V m ) stored in the capacitor C 3  is discharged. This charge will flow to the capacitor C 4  and charges it to the same voltage (2V m ). The capacitors C 2  and C 4  are in series and the output voltage is taken across the two series connected capacitors C 2  and C 4 . The voltage across capacitor C 2  is 2V m  and capacitor C 4  is 2V m . So the total output voltage is equal to the sum of capacitor C 2  voltage and capacitor C 4 voltage I.e. C 2  + C 4  = 2V m  + 2V m  = 4V m .

14. Practicle Applications Voltage multipliers are used in : Cathode Ray Tubes (CRTs) Laser systems X-ray systems LCD backlighting Power supplies Oscilloscopes Particle accelerators Copy machines

15. Disadvantages Need Protection Circuit Low Current Delay Greater than transformer Cost depend upon Capacitors Low Cost Produce High Voltage Alternative of Transformer Advantages