Gate drive circuit
First Claim
1. A drive circuit for controlling the operation of a switching device, the switching device including a control port for receiving a signal from said drive circuit for controlling its conductance state, said drive circuit being responsive to an input control signal having a first state for directing the switching device to enter a first conduction state and a second state for directing the switching device to enter a second conduction state, the input control signal alternating between its first and second states during normal operation and being caused to remain in its second state when operation of the switching device is to be terminated, said drive circuit comprising:
- an output port for coupling to the control port of the switching device;
a transformer having a primary winding and a secondary winding, said secondary winding being coupled to said output port, said primary winding having a first terminal and a second terminal;
coupling means responsive to said input control signal for coupling power to said primary winding when the input control signal is in its first state, said coupling causing a voltage of a first polarity to be applied across said primary winding, a portion of said power being coupled to the control port of the switching device by said secondary winding and causing the switching device to enter its first conduction state, said transformer storing energy in response to the coupling of said power, said coupling means further for uncoupling said power from said primary winding and substantially removing said power from said primary winding when the input control signal enters its respective second state, said portion of said power thereafter being uncoupled from the switching device such that said switching device is caused to enter its second conduction state; and
discharge means coupled to said transformer and responsive to the uncoupling of said power from said primary winding for discharging the energy stored in said transformer during the second state of said control signal such that sufficient power is prevented from being coupled to the switching device to cause it to enter its first conduction state during the time the input control signal is in its second state, said discharge means comprising a reversal means for applying a voltage having a second polarity opposite to said first polarity across said primary winding in a time interval during the second state of said input control signal, said second polarity voltage discharging the energy stored in said transformer, said reversal means comprising a means for applying a first reference voltage to the first terminal of said primary winding and a first capacitance coupled to said second terminal of said primary winding, the energy stored in said transformer being directed into said first capacitance during said second state of said input control signal such that a reversing voltage is generated thereon and a voltage of said second polarity is applied to said primary winding, said discharge means further comprising a second reference voltage and a rectifier coupled between the second terminal of said primary winding and said second reference voltage, said rectifier conducting current to limit the magnitude of voltage across said primary winding having said second polarity to less than a predetermined value during the time said input control signal is in its second state.
1 Assignment
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Accused Products
Abstract
An improved gate drive circuit for use with a switching power device in a power converter and other power-transfer type circuits and the like is described. The gate drive circuit according to the present invention requires fewer components and space that convention prior art gate drive circuits. The drive circuit provides isolation between the control circuitry and the device without storing a significant amount of long-term (i.e., D.C.) energy and is also more energy efficient than many prior art gate drive circuits. Additionally, the present invention comprises means for cleanly terminating the drive signal to the switching power device when the control circuitry terminates operation. This prevents an incorrect signal to the switching power device, which may conduct at an inappropriate time, causing damage to the power converter or power-transfer circuit. Many prior art drive circuits have D.C. blocking capacitors that discharge slowly upon termination and, consequently, cause the switching power device to inadvertently conduct, which may damage the converter.
68 Citations
20 Claims
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1. A drive circuit for controlling the operation of a switching device, the switching device including a control port for receiving a signal from said drive circuit for controlling its conductance state, said drive circuit being responsive to an input control signal having a first state for directing the switching device to enter a first conduction state and a second state for directing the switching device to enter a second conduction state, the input control signal alternating between its first and second states during normal operation and being caused to remain in its second state when operation of the switching device is to be terminated, said drive circuit comprising:
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an output port for coupling to the control port of the switching device; a transformer having a primary winding and a secondary winding, said secondary winding being coupled to said output port, said primary winding having a first terminal and a second terminal; coupling means responsive to said input control signal for coupling power to said primary winding when the input control signal is in its first state, said coupling causing a voltage of a first polarity to be applied across said primary winding, a portion of said power being coupled to the control port of the switching device by said secondary winding and causing the switching device to enter its first conduction state, said transformer storing energy in response to the coupling of said power, said coupling means further for uncoupling said power from said primary winding and substantially removing said power from said primary winding when the input control signal enters its respective second state, said portion of said power thereafter being uncoupled from the switching device such that said switching device is caused to enter its second conduction state; and discharge means coupled to said transformer and responsive to the uncoupling of said power from said primary winding for discharging the energy stored in said transformer during the second state of said control signal such that sufficient power is prevented from being coupled to the switching device to cause it to enter its first conduction state during the time the input control signal is in its second state, said discharge means comprising a reversal means for applying a voltage having a second polarity opposite to said first polarity across said primary winding in a time interval during the second state of said input control signal, said second polarity voltage discharging the energy stored in said transformer, said reversal means comprising a means for applying a first reference voltage to the first terminal of said primary winding and a first capacitance coupled to said second terminal of said primary winding, the energy stored in said transformer being directed into said first capacitance during said second state of said input control signal such that a reversing voltage is generated thereon and a voltage of said second polarity is applied to said primary winding, said discharge means further comprising a second reference voltage and a rectifier coupled between the second terminal of said primary winding and said second reference voltage, said rectifier conducting current to limit the magnitude of voltage across said primary winding having said second polarity to less than a predetermined value during the time said input control signal is in its second state. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A drive circuit for controlling the operation of a switching device, the switching device including a control port for receiving a signal from said drive circuit for controlling its conductance state, said drive circuit being responsive to au input control signal having a first state for directing the switching device to enter a first conduction state and a second state for directing the switching device to enter a second conduction state, the input control signal alternating between its first and second states during normal operation and being caused to remain in its second state when operation of the switching device is to be terminated, said drive circuit comprising:
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an output port for coupling to the control port of the switching device, said output port including first and second terminals; a transformer having a primary winding and a secondary winding, said secondary winding being coupled to said output port; coupling means responsive to said input control signal for coupling power to said primary winding when the input control signal is in its first state, a portion of said power being coupled to the control port of the switching device by said secondary winding and causing the switching device to enter its first conduction state, said transformer storing energy in response to the coupling of said power, said coupling means further for uncoupling said power from said primary winding and substantially removing said power from said primary winding when the input control signal enters its respective second state, said portion of said power thereafter being uncoupled from the switching device such that said switching device is caused to enter its second conduction state; and discharge means coupled to said transformer and responsive to the uncoupling of said power from said primary winding for discharging the energy stored in said transformer during the second state of said control signal such that sufficient power is prevented from being coupled to the switching device to Cause it to enter its first conduction state during the time the input control signal is in its second state, said discharge means comprising a shunting means coupled between the secondary winding of said transformer and the terminals of said output port for shunting said output terminals to one another when said input control signal enters it said second state. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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18. A drive circuit integrated on a semiconductor chip for controlling the operation of a switching device, the switching device being isolated by a transformer having a first winding and a second winding, the second winding being coupled to the switching device, said drive circuit comprising:
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an output port for coupling to the transformer'"'"'s first winding and including a first output terminal and a second output terminal; means for generating a control signal having a first voltage state and a second voltage state, said control signal being coupled to said first output terminal; a transistor having a control terminal coupled to said control signal, a first conduction terminal coupled to a first reference voltage, and a second conduction terminal coupled to said second output terminal, said transistor being rendered conductive in response to said control signal entering its first voltage state and rendered non-conductive in response to said control signal entering its second voltage state, said transistor when closed causing a voltage having a first polarity to be applied across said first and second output terminals; and a first rectifier coupled between said second output terminal and said first reference voltage, said first rectifier oriented such that it may conduct current when a voltage of said first polarity is applied across said output terminals during the time said control signal is in its second voltage state, said first rectifier coupling said first reference voltage to said second output terminal when it is conducting, said second voltage state of said control signal and said first reference voltage having values such that said first rectifier when conducting current limits the magnitude of voltage across said output terminals having said first polarity to less than a first predetermined value during the time said control signal is in its second voltage state. - View Dependent Claims (19, 20)
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Specification