Gate drive circuit for an SCR
AssigneeYork International Corporation
InventorsHarold R. Schnetzka, Dean K. Norbeck, Donald L. Tollinger
Life of this patent
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Abstract
A gate drive circuit for a silicon controlled rectifier (SCR) connected in an a-c power circuit includes a voltage divider network connected between a d-c voltage source and the SCR for developing a varying voltage on a control node, depending upon whether the anode-to-cathode a-c voltage of the SCR is positive or negative. A first switching transistor, responsive to the control node voltage, controls conduction of a second switching transistor connected between the d-c voltage source and a voltage regulated driver circuit. In this way, a constant drive current is applied to the SCR gate only while the anode-to-cathode voltage of the SCR is positive.
Claims11
A gate drive circuit for gating a silicon controlled rectifier (SCR) connected in an a-c power circuit, comprising:
- a d-c voltage source;
- a driver circuit for producing a gate drive current, when connected to the d-c voltage source, to trigger the SCR into conduction;
- and
- a switching circuit including a switch connected between the d-c voltage source and the driver circuit and a voltage divider network connected between the d-c voltage source and the SCR, the switching circuit operating to control the switch such that the switch is closed when the anode-to-cathode a-c voltage reaches a positive value and the switch is open when the anode-to-cathode voltage reaches a negative value.
A gate drive circuit for gating a silicon controlled rectifier (SCR) connected in an a-c power circuit, comprising:
- a d-c voltage source;
- a driver circuit for producing a gate drive current, when connected to the d-c voltage source, to trigger the SCR into conduction;
- and
- a switching circuit including:
- a first semiconductor switch connected between the d-c source and the driver circuit;
- a voltage divider network connected between the d-c voltage source and the SCR, the voltage divider network including:
- a control node;
- a first diode poled to block the control node from sensing a positive anode-to-cathode a-c voltage across the SCR and to communicate a negative anode-cathode voltage to the control node;
- and
- a second diode connected to clamp the control node at a turn-on voltage while the first diode blocks the control node from sensing the anode-to-cathode voltage;
- and
- the switching circuit further including a second semiconductor switch connected to the d-c voltage source and the control node for producing a turn-on voltage to close the first semiconductor switch in response to the turn-on voltage on the control node and to open the first semiconductor switch while the first diode communicates the negative anode-cathode voltage to the control node.
A gate drive circuit for gating a silicon controlled rectifier (SCR) connected in an a-c power circuit, comprising:
- a d-c voltage source;
- a driver circuit for producing a gate drive current, when connected to the d-c voltage source, to trigger the SCR into conduction;
- and
- a switching circuit including a voltage divider network connected between the d-c voltage source and the SCR, the switching circuit controlling the connection of the driver circuit to the d-c voltage source such that the driver circuit is connected to the d-c voltage source when a control node of the voltage divider network senses that an anode-to-cathode voltage of the SCR reaches a positive value and controlling the disconnection of the driver circuit from the d-c voltage source such that the driver circuit is disconnected to the d-c voltage source when the anode-to-cathode voltage reaches a negative value.
Dependencies are inferred from the claim text.