Power Electronics EE3591_introduction.pptx

Power electronics introduction

1. Power Electronics EE3591 SEMESTER – 5 Regulation 2021 ( Anna Univ Chennai) Dr.R.Anand Prof & Head Dept of EEE,MCE Salem

2. Electrical and Electronics Engineering Electrical engineering is an engineering branch that focuses on the generation, transmission, as well as distribution of electrical power. ( GTD) On the other hand, electronics engineering ( sub-discipline of electrical engineering) centers on design and development of electronic devices, circuits, and systems

3. Electrical Engineering

4. Power Electronics - Introduction Power electronics deals with electronic devices used for conversion and control of electric power. Power electronics is the application of solid-state electronics to control and convert one form of electrical power to another form such as converting between AC and DC or changing the magnitude and phase of voltage and current or frequency or combination of these

5. MOSFET dynamic behaviour – T1 – Pg 581 driver and snubber circuits – T1- Pg 667/696 low power high switching frequency switching Power supplies – T1-301 buck, boost, buck-boost converters T1- 164/172/178 Isolated topologies – R esonant converters – T1 – 249 switching loss calculations – thermal design -

6. UNIT I SWITCHING POWER SUPPLIES MOSFET dynamic behaviour - driver and snubber circuits - low power high switching frequency switching Power supplies, buck, boost, buck-boost converters – Isolated topologies – resonant converters - switching loss calculations and thermal design.

7. MOSFET IC

8. MOSFET Dynamic Characteristics/Behavior MOSFET SYMBOLS

9. Switching Characteristics of Power MOSFET

10. Figure shows a steady state switching circuit of a power MOSFET. When a pulse input voltage is applied to the gate of power MOSFET, the device will be turn-on if the gate to source voltage V GS  is greater than threshold voltage V GS( th ) . At time t = t , input voltage at the gate of power MOSFET is Vg = 0 and the gate to source voltage V GS  is less than threshold voltage V GS( th ) . At that moment, the device operates in OFF state and the drain current I D  is equal to zero and the output voltage is V O  = V DS  = V DD . The switching waveforms of a power MOSFET are illustrated in Figure. At time t = t 1 , voltage starts to increase from 0 to V 1  and the input capacitance C gs  starts to charge as depicted in Figure

11. 6. During the turn on delay time t d , the capacitance C gs  is charged to gate threshold voltage V GS( th ) . 7. During rise time t r , the gate to source voltage V GS  increases from gate threshold level V GS( th )  to the full gate voltage, V GSP  to operate the transistor in linear region. 8. In time t r , the drain current increases from 0 to I D . 9. The total turn on time of MOSFET is sum of delay time and rise time.

12. Delay time t d  The delay time td is the time required to charge the input capacitance from its initial value to gate threshold voltage V GS( th ) . Rise time t r  The rise time t r  is the time required to charge the input capacitance Cgs from gate threshold level V GS( th )  to the full gate voltage, V GSP . Turn-on time t turn -on  The turn-on time is the sum of the delay time t d  and the rise time t r  and it can be expressed as t turn -on  = t d  + t r .

13. In the turn-off process, the gate voltage Vg is removed t = t 2 , the input capacitance starts to discharge from gate voltage V 1  to V GSP . V GS  must be decreased significantly so that V DS  starts to increase. The fall time is the time during which input capacitance discharged from V GSP  to gate threshold voltage V GS( th ) . In this time, the drain current decreases from I D  to zero. When V GS <V GS( th ) , the device completely turn off. The turn-off delay time t df  is the time during which the input capacitance discharges from gate voltage V1 to VGSP. The fall time t f  is the time in which the input capacitance discharges from gate voltage V GSP  to V GS( th )  and the drain current becomes zero. The turn-off time is the sum of the turn-off delay time ( t df ) and fall time ( t f ) and it can be represented by t turn -off  = t df  + t f

14. N-Channel MOSFET/NMOS

15. P-Channel MOSFET/PMOS