US 6,275,093 B1Granted

IGBT gate drive circuit with short circuit protection

AssigneeIntersil Corporation

InventorsSampat Singh Shekhawat, Jon Gladish, Anup Bhalla

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Abstract

An IGBT gate driver circuit includes means for detecting when the collector-to-emitter voltage (Vce) of a turned-on IGBT, intended to be operated in the saturation region, increases above a preset level, indicative of a fault condition, such as a short circuit. In response to such an increase in the Vce of a turned on IGBT, the IGBT is turned-off in two steps. First, the turn-on gate drive is decreased to a level that is still above the threshold (turn-on) voltage of the IGBT in order to decrease the current flowing through the IGBT and hence, the peak power dissipation. This decrease in the current through the IGBT and the peak power dissipation increases the length of time the IGBT can withstand a fault condition such as a short circuit. Then, after decreasing the gate drive to the IGBT, the gate drive is gradually decreased until the IGBT is completely turned off.

Claims16

Dependent claims

A combination comprising:

an insulated-gate bipolar transistor (IGBT) having first and second electrodes defining the ends of the main conduction path of the IGBT, and having a control electrode for the application thereto of a control voltage for turning the IGBT on and off;
said IGBT being characterized in that a voltage applied between the control and second electrodes must exceed a certain threshold voltage (VT) in order to turn-on the IGBT and in that it has a saturation voltage, VSAT, which is in the range of a few volts;
means for coupling a load between the first electrode of the IGBT and a load power supply terrninal;
means connecting the second electrode of the IGBT to a point of reference potential;
means for applying a turn-on voltage to the control electrode of the IGBT which is significantly greater than the threshold voltage of the IGBT for operating the IGBT in saturation;
means coupled to the first electrode of the IGBT for sensing its voltage level and which is responsive to the voltage at the first electrode exceeding the saturation voltage by a first amount for:
appling a preset reduced voltage to the control electrode of the IGBT, said preset reduced voltage being less than said turn-on voltage by a preset amount and being greater than the threshold voltage;
and being responsive to the voltage at the first electrode exceeding the saturation voltage by a second amount which is greater than said first amount to gradually decrease the preset reduced voltage applied to the control electrode below the threshold voltage of the IGBT in order to turn it off completely;
and wherein said preset reduced voltage is gradually decreased by the gradual discharge of a resistive capacitance (RC) network;
where the capacitance of the network includes a distinct, independently manufacture, component, having a capacitance which is substantially greater than the typical gate to source capacitance of a metal oxide field effect transistor, and wherein said gradually decreasing voltage is coupled to the control electrode of the IGBT.

7 more elements

A combination comprising:

an insulated-gate bipolar transistor (IGBT) having first and second electrodes defining the ends of the main conduction path of the IGBT, and having a control electrode for the application thereto of a control voltage for turning the IGBT on and off;
said IGBT being characterized in that a certain voltage applied between the control and second electrodes must exceed a certain threshold voltage (VT) in order to turn on the IGBT and in that it has a saturation voltage, VSAT, which is in the range of a few volts;
means for coupling a load between the first electrode of the IGBT and a load power supply terminal;
means connecting the second electrode of the IGBT to a point of reference potential;
gate driving means coupled to the control electrode of the IGBT for normally applying a turn-on voltage to the control electrode of the IGBT which is significantly greater than the threshold voltage of the IGBT for operating the IGBT in saturation,
sensing and control means coupled between the first electrode of the IGBT and the gate driving means for sensing when the voltage level at the first electrode exceeds a first value for applying a preset reduced voltage to the control electrode of the IGBT, said preset reduced voltage being less than said turn-on voltage by a preset amount and being greater than the threshold voltage;
and for sensing when the voltage at the first electrode exceeds a second value said second value being greater than said first value, for then gradually decreasing the preset reduced voltage applied to the control electrode to a level below the threshold voltage of the IGBT in order to turn it off completely;
wherein said preset reduced voltage is gradually decreased by a resistive capacitive network, where the capacitance of the network includes a distinct, independently manufactured, component, having a value which is substantially greater than that of the typical gate to source capacitance of a metal oxide field effect transistor.

5 more elements

Dependencies are inferred from the claim text.