1. AC Power Supplies Applications –Standby source for “critical” loads (computer) –Primary source when normal ac not available Uninterrupted Power Supply (UPS) –2 common configurations

2. Configuration 1 Load normally supplied by Main Supply

3. Operating Modes Normal condition –Main supply applied to the load –Rectifier keeps batteries charged Main supply failure –Inverter supplies power to the load –When interruption is over, main supply is applied to the load

4. Configuration 2 Inverter supplies power to the load

5. Operating Modes Normal condition –Inverter operates continuously, powering the load –Rectifier maintains the charge on the batteries –Inverter conditions the supply to the load Inverter failure –Main supply powers the load

6. Typical UPS System

7. Operating Conditions Main supply failure –Battery supplies the inverter –Inverter powers the load Normal conditions –Inverter operates as a bridge rectifier –Main supply powers the load

8. Types of AC Power Supplies Switched-mode Resonant Bidirectional

9. Switched-Mode AC Power Supply

10. Features of the Switched-Mode Configuration Two inverters –Input side: operates at high-frequency –Reduces size of transformer and DC filter components at the input of the output-side inverter

11. Features of the Switched-Mode Configuration Two inverters continued –Output side: operates at output frequency

12. Resonant AC Power Supply

13. Features of the Resonant AC Power Supply Two inverters –Input side is a resonant inverter –Output side operates with PWM control at the output frequency

14. Bidirectional AC Power Supply

15. Features of the Bidirectional AC Power Supply Output inverter and Rectifier are combined into a cycloconverter (converts one frequency ac into another frequency ac) Power flow in either direction

16. Multistage Conversions

17. Multistage Conversions (continued) Four conversions AC-DC – DC-AC – AC-DC – DC-AC Ultimately an AC – AC Conversion

18. Alternative Configuration 2-Forced-Commutated Cycloconverters