Resonant Inverters

Resonant pulse Inverters

1. 1 RESONANT PULSE INVERTERS Dr. A. Ravi Professor/EEE FRANCIS XAVIER ENGINEERING COLLEGE TIRUNELVELI- India

2. To get the desired output voltage or current , the switching devices in converters are controlled by with a pulse-width-modulation (PWM) control. Hence the devices are undergone with high switch high di / dt value also high voltage stresses resulting Power loss of a devices. This power losses are increasing with switching frequency. The electromagnetic interference is also produced due to high di / dt and dv / dt in the converter waveforms. 2 Why Resonant Pulse Converter - Introduction

3. The disadvantages of PWM control can be eliminated or minimized if the switching devices are turned “on” and “off” when the voltage across a device or its current becomes zero. The voltage and current are forced to pass through zero crossing by creating an LC-resonant circuit, thereby called a resonant pulse converter. 3 Why Resonant Pulse Converter - Introduction

4. Series resonant inverters Parallel resonant inverters Class E resonant converter Class E resonant rectifier Zero-voltage-switching (ZVS) resonant converters Zero-current-switching (ZCS) resonant converters Two-quadrant ZVS resonant converters Resonant dc-link inverters 4 Resonant Pulse Converter - Types

5. The series resonant inverters produce a near sinusoidal output voltage and the output current depends on the load impedances. The parallel resonant inverter produces a near sinusoidal output current and the output voltage depends on the load impedances. These types of inverters are used for producing high-frequency output voltage or current and are often used as an intermediate between a dc source and a dc power supply. 5 Resonant Pulse Converter -

6. depending on the connections of the switching devices and load. The series inverters may be classified into two categories: 1. Series resonant inverters with unidirectional switches 2. Series resonant inverters with bidirectional switches 6 Series Resonant Inverters

7. 7 Series Resonant Inverters with Unidirectional Switches The series resonant circuit formed by L, C, and load (assumed resistive) must be Underdamped . That is,

8. 8 Series Resonant Inverters with Unidirectional Switches Disadvantages: The power flow from the dc supply is discontinuous

9. 9 Series Resonant Inverters with Unidirectional Switches An improvement of the basic inverter can be made if inductors are closely coupled, as shown here. When Q1 is turned on and current i 1 (t) begins to rise, the voltage across L1 is positive with polarity as shown . The induced voltage on L2 now adds to the voltage of C in reverse biasing Q2; and Q2 can be turned off. The result is that firing of one transistor turns off the other, even before the load current reaches zero. Drawbacks

10. The drawback of high-pulsed current from the dc supply can be overcome in a half-bridge Configuration where L1 = L2 and C1 = C2. The power is drawn from the dc source during both half-cycles of output voltage. One-half of the load current is supplied by capacitor C 1 or C 2 and the other half by the dc source 10 ( i ) Half-bridge series resonant inverter. Series Resonant Inverters with Unidirectional Switches

11. When Q1 and Q2 are turned on, a positive resonant current flows through the load; and when Q3 and Q4 are turned on, a negative load current flows. The supply current is continuous, but pulsating. The resonant frequency and available dead zone depend on the load. 11 (ii)Full-bridge series resonant inverter. Series Resonant Inverters with Unidirectional Switches

12. For the resonant inverters with unidirectional switches, the power devices have to be turned on in every half-cycle of output voltage . This limits the inverter frequency and the amount of energy transfer from the source to the load. In addition, the devices are subjected to high peak reverse v oltage. 12 Series Resonant Inverters with Unidirectional Switches

13. 13 Series Resonant Inverters with Bidirectional Switches When device Q1 is turned on, a resonant pulse of current flows and Q2 is self-commutated at t = t 1 . However , the resonant oscillation continues through diode D1 until the current falls again to zero at the end of a cycle.

14. 14 Series Resonant Inverters with Bidirectional Switches Half-bridge series inverters with bidirectional switches.

15. 15 Full-bridge series inverters with bidirectional switches. Series Resonant Inverters with Bidirectional Switches

16. A parallel resonant inverter is the dual of a series resonant inverter. It is supplied from a current source so that the circuit offers a high impedance to the switching current. 16 Parallel Resonant Inverters

17. 17 Parallel Resonant Inverters Equivalent circuit Equivalent circuit

18. Reference 18 Power Electronics Devices , Circuits, and Applications FOURTH EDITION Muhammad H. Rashid

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