AC Power Supplies Applications Standby source for critical

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

Configuration 1 Load normally supplied by Main Supply

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

Configuration 2 Inverter supplies power to the load

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

Typical UPS System

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

Types of AC Power Supplies • Switched-mode • Resonant • Bidirectional

Switched-Mode AC Power Supply

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

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

Resonant AC Power Supply

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

Bidirectional AC Power Supply

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