rectifier

1. RECTIFIERS
• It is the process of converting AC voltage
to the DC voltage or current.
• Types :
1.HWR
2.FWR

3. OPERATION :
• During positive half cycle A is positive with
respect to B. Hence diode is forward biased
and starts conducting.
• During negative half cycle B is positive with
respect to A. Hence diode is reverse biased
and do not conducts.

4. ANALYSIS OF HWR
• Average Load current (ILDC )
The average value of periodic function is
given by the area under one cycle of the function
divided by the base function.

5. 2.Average load Current (VLDC )
VLDC = ILDC * RL

6. 3.RMS or AC Load Current (ILRMS )

7. 4.RMS or AC Load Voltage (VLRMS )
VLRMS = ILRMS * RL
VLRMS =
𝑽𝒎
𝟐
5.Voltage Regulation :
Ideally the average rectifier output should
remains constant. But practically it varies with
the change in load current.

8. %Load Regulation =
𝑹𝒔+𝑹𝑳
𝑹𝑳
* 100
6.Rectification Efficiency (η):

10. Ripple factor (ϒ)
• The rectifier output consists of AC as well as
DC components. The ripple factor measures
the percentage of AC component in the
rectifier output.
ϒ =
𝑉𝐴𝐶
𝑉𝐷𝐶
• ϒ =1.21
• %ϒ =121

11. • Transformer Utilization Factor :
It is defined as the ratio of DC output power
to the AC power ratings of transformer.
Disadvantages of HWR :
High ripple factor
Low rectification efficiency
Low TUF
Low DC output voltage and current
It required large filter component.

12. FWR USING CENTRE TAPPED
TRANSFORMER
• A circuit which converts the AC
voltage/current into pulsating voltage/current
during both the half cycle of input is called as
FWR.

14. Analysis of FWR
• Average Load current (ILDC )
The average value of periodic function is
given by the area under one cycle of the function
divided by the base function.
ILDC =
𝟐𝑰𝑴
𝝅

15. 2.Average load Current (VLDC )
VLDC = ILDC * RL

16. 3.RMS or AC Load Current (ILRMS )

17. 4.RMS or AC Load Voltage (VLRMS )
• VLRMS = ILRMS * RL
VLRMS =
𝑽𝒎
√𝟐
5.Voltage Regulation :
Ideally the average rectifier output should
remains constant. But practically it varies with
the change in load current.

18. %Load Regulation =
𝑅𝑠+𝑅𝐿
𝑅𝐿
* 100
6.Rectification Efficiency (η):

20. Ripple factor (ϒ)
• The rectifier output consists of AC as well as
DC components. The ripple factor measures
the percentage of AC component in the
rectifier output.
ϒ =
𝑉𝐴𝐶
𝑉𝐷𝐶

21. Disadvantages of FWR :
Use of additional diode and bulky transformer is
needed.
PIV of diode is very high
Advantages of FWR :
 Low ripple factor compared to HWR
 Efficiency is high
 Better TUF
 No core saturation

23. OVERVOLTAGE PROTECTION
• The voltage regulator is used to supply the
regulated dc voltage to an electronic equipment
contains costly Ics and other devices.
• About 10% higher voltage application for short
duration of time is permissible. But very high
voltage, about twice the rated voltage is
destructive for the costly equipment.
• Hence the overvoltage protection is essential.

24. • A simple circuit called crowbar protection
is used. It uses the device SCR which is
normally in the OFF condition.

25. • The zenor diode is used such that its voltage
Vz is 1.2 times the output voltage Vo.
• If there is a voltage surge , then the zener
diode conducts ,developing sufficient voltage
across the resistance R1,to trigger SCR ON.
• When SCR conducts, the drop across the
SCR is very small. The same is the voltage
across the equipment hence the equipment is
saved.

26. The SCR current rating should exceed the
maximum surge current expected and the
voltage regulator circuit should be provided
with the short circuit protection.
The negative surge are protected by the
diode D.

27. Power Supply Performance and Testing
• Power supply is the heart of any electronic
equipment. Hence for high quality and reliable
operation, it is necessary to verify the power
supply performance by conducting the tests.
• The test specifications must include all the
safe operating limits such as temperature, line
conditions , regulation values etc…

28. Testing Procedure and Specifications
1. First switch ON – check the input voltage
2.Inrush Current test – Impedance checking
3.Transient recovery time test
4.Static load regulation test
5.Line regulation test
6.Peridic and random deviation (PARD ) test
7.Efficiency test
8.Power factor
9.Start up time
10.Short circuit output current
11.Overload shutdown
12.Leakage current
13.Holdup time