Switching DC power supplies (SMPS) convert unregulated AC or DC input voltage to a regulated DC output voltage using a high frequency DC-to-DC converter and transformer. SMPS are more efficient than linear power supplies due to using switching components that result in lower losses. SMPS can provide multiple isolated output voltages and have smaller size due to the high frequency transformer. The output is regulated using pulse-width modulation (PWM) control of the switching converter to maintain a constant output voltage despite input variations. Common converter circuit topologies in SMPS include flyback, forward, half-bridge, and full-bridge converters.

2. SWITCHING DC POWER SUPPLIES
INTRODUCTION
LINEAR POWER SUPPLY
OVERVIEW OF SWITCHING POWER SUPPLIES
DC – DC CONVERTER WITH ELECTRICAL
ISOLATION
CONTROL OF SMPS
POWER SUPPLY PROTECTION
APPLICATION

3. Introduction
Like a linear power supply, the SMPS too converts
unregulated ac or dc input voltage to a regulated dc
output voltage
The input voltage is first rectified and filtered using a
capacitor at the rectifier output
unregulated dc voltage across the capacitor is then
fed to a high frequency dc-to-dc converter
The high frequency transformer used in a SMPS

4. Linear Power Supplies

5. Disadvantages of LPS
The output fluctuates with input
which is not desirable
Isolation is not possible
Efficiency is very low
Bulky and noisy

6. SMPS Block Diagram

7. Switching DC Power Supply:
Multiple Outputs
In most applications, several dc voltages are
required, possibly electrically isolated from each other

8. Transformer Analysis
Needed for high-frequency isolated supplies

9. PWM to Regulate Output

10. PWM OUTPUT WAVEFORM

11. Flyback Converter

12. FLYBACK CONVERTER WAVEFORM’S

13. Other flyback converters are:~
1. Two transistor flyback converter
2. Parallelled flyback converter
But these are not commonly used

14. Forward Converter
Derived from Buck; idealized to assume that the
transformer is ideal (not possible in practice)

15. Half-Bridge Converter
Derived from Buck converter

16. Full-Bridge Converter
Used at higher power levels (> 0.5 kW )

17. Input Filter
Needed to comply with the EMI and harmonic
limits

18. Conclusion
One of the most important applications of power
electronics is SMPS
High efficiency and small weight and size
In SMPS multiple outputs are possible
Losses is minimum and only switching losses are
present
Current rating is medium
The high frequency transformer used in a SMPS

19. Switched Mode Power Supply

20. THANK YOU
QUESTION??