Electronic Design

Gate Drivers: Key To Power Switching</A><BR><FONT CLASS=body11>Sponsored by: <A HREF="http://www.ixys.com" TARGET=_blank CLASS=body11>IXYS CORP.</A></FONT><A>

Consider all aspects of gate-driver design to ensure power-system reliability and performance.

Power-Switching Enablers
Low-power, logic-level switching signals can't drive moderate- to high-power semiconductor switches, such as the MOSFET (metal-oxide semiconductor field-effect transistor) and IGBT (insulated-gate bipolar transistor). To solve this problem, gate-driver ICs provide the necessary buffer between low-power switching signals and discrete MOSFET/IGBT power semiconductor switches. Gate-driver ICs are essentially power amplifiers that accept low-level switching inputs and produce switched outputs of hundreds of milliamperes to tens of amperes to drive MOSFET and IGBT gates. These MOSFET/IGBTs can then handle loads from milliwatts to kilowatts, depending on the gate-drive current and the power-handling capability of the MOSFET/IGBT.

Performance Basics
To be effective, the gate driver's input stage must be compatible with both TTL and CMOS inputs. It also must be immune to latch-up over its entire operating range. The output stage can supply single-ended, half-bridge, or three-phase bridge drive for MOSFETs/IGBTs. Most gate drivers can handle output loads from 2000 to 3000 pF, which is approximately the input capacitance of a typical power MOSFET or IGBT. Today's gate drivers can exhibit rise and fall times of less than 100 ns with the same order-of-magnitude propagation delays. Because they accept low-voltage inputs and handle higher output voltage levels, gate drivers must have efficient, reliable, and non-latching voltage-level translation circuits. Gate drivers feature shutdown options as well as overcurrent, undervoltage, and overtemperature protection.

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