Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Current driver
Reexamination Certificate
1999-11-15
2001-12-04
Cunningham, Terry D. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Current driver
C327S112000, C326S083000
Reexamination Certificate
active
06326819
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to current buffers for driving electronic components and, more particularly, to a current buffer for driving insulated gate bipolar transistors.
BACKGROUND OF THE INVENTION
Switching devices for switching high current to drive high current devices such as an electric motor are well known. Such switch devices include, e.g. Insulated Gate Bipolar Transistors (IGBTs), which are typically controlled by a microprocessor or other digital device to provide desired drive currents to windings of an electric motor. The signals for switching (driving) the IGBTs often require current buffering.
One type of current buffer used to drive an IGBT is a non-inverting bipolar transistor. In other words, the output logic signal of the driver is the same polarity as the output of the current buffer. Additional circuitry (i.e., additional components) is provided to prevent voltage shoot-through as a result of base storage time, as is known. The bipolar transistor also introduces an additional voltage drop (1.4 volts) between the voltage rails and the output, thus requiring a higher voltage bias supply to offset the voltage drop.
Another type of current buffer is a Metal Oxide Silicon Field Effect Transistor (MOSFET), which introduces an inversion of the output of the current buffer. This causes the MOSFETs not to be usable with MOSFET with gate drivers that have built-in fault handling. Additional circuitry is also provided to prevent voltage shoot-through due to mutual conduction of the MOSFETs during the switching time.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a current buffer arrangement for gate drives that takes advantage of the output drive capability of the gate driver itself. This results in fewer components and thereby reduced manufacturing cost and time. The current buffer is also non-inverting so that it can be used with existing gate drivers with built in fault handling capabilities.
The instant invention advantageously uses the gate driver's current driving capability by defining a path which electrically couples the output of the gate driver (input end of buffer) and the input (output end of buffer) of an electronic device, for example, an IGBT. Two switches each having an ON and OFF state are used. During the ON state a positive or a negative voltage power source supplies power to the output end resulting from the introduction of a suitable signal at the input end of the buffer. A control circuit controls the ON or OFF state of the switches. The control circuit can be a set of suitably arranged resistors. However, the control circuit may include other types of suitable components. When desired input signal occurs at the input end of the buffer, one of the switches is triggered to ON state. The output end of the buffer is charged via the electrical connection through the ON switch as well as current driving capability of the gate driver via the path. Upon reaching a threshold point at the output end of the buffer, e.g. a threshold voltage, the switch is switch to OFF state and the only electrical connection between the input and output end of the buffer is via the path. Thus, the current drive capability of the gate driver (via the path) remains the only source in reaching an equilibrium state between the input and output end of the buffer.
REFERENCES:
patent: 4703198 (1987-10-01), Porter et al.
patent: 5223753 (1993-06-01), Lee et al.
patent: 5486777 (1996-01-01), Nguyen
patent: 5698953 (1997-12-01), Shim
patent: 5977814 (1999-11-01), Ishii
Cunningham Terry D.
General Motors Corporation
Simon Anthony Luke
Tra Quan
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