Drive Circuit. What is “drive circuit”? Circuits that are constructed to turn on/off power...
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Transcript of Drive Circuit. What is “drive circuit”? Circuits that are constructed to turn on/off power...
Drive Circuit
What is “drive circuit”?Circuits that are constructed to turn on/off power devices/switches
Control circuit Gate driver
• Provides an interface between the control signal (small signal electronics) and power circuits
• Sometimes called ‘gate drivers’
Why do we need drive circuit?To amplify control signals to level required to drive the power switches and also to ensure fast turn-on and turn-off
• MOSFET/IGBT typically require voltages between 10V - 20V to ON and initial high current to charge parasitic input capacitance. The capacitor need to be discharged during turn off
• BJT require continuous current to ON – initial high current is needed to reduce turn on time.
Provides electrical isolation between control circuit (small signal) and power circuit • Require for safety reasons and elevated emitter (or source) of the transistor in
bridge configuration
Some examples of drive circuits
Gate drive with totem-pole configuration
Some examples of drive circuits
• Isolated dc power supplies for drive circuits
• Opto-coupler isolation
• Transformer isolation
Electrical isolation methods
Some examples of drive circuits
• Negative half cycle of vs(t) - positive dc rail near safety ground potential. T- emitter potential large and negative with respect to safety and logic ground
• Postive half cycle of vs(t) - negative dc rail near safety ground potential. T+ emitter substantially positive with espect to safety ground if T- is off
• Variation in emitter potentials with respect to safety and logic ground means that electrical isolation of emitters from logic ground is needed.