Thermal clamp for an ignition coil driver
First Claim
1. A circuit for driving an inductive load coupled thereto, comprising:
- charging means for providing current through the inductive load when enabled and for inhibiting current through the inductive load when disabled;
a control circuit being responsive to a first input logic signal for providing a first output logic signal for enabling and disabling said charging means when said first output logic signal respectively is in a first and second logic state, said control circuit being responsive to a second input logic signal for both providing a second output logic signal and causing said first output logic signal to be in said second logic state; and
thermal clamping means responsive to said second output logic signal and being coupled between the inductive load and said charging means for providing current to said charging means thereby enabling said charging means to both discharge the inductive load at a predetermined rate and clamp the voltage across the inductive load to a predetermined voltage wherein a collapse of current through the inductive load is prevented.
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Accused Products
Abstract
A circuit in an ignition system having a switchable current drive circuit responsive to a first control signal, and a charging circuit responsive to the switchable current drive circuit for providing a current through a coil to charge the coil when the switchable current drive circuit is enabled by the first control signal being in a first logic state and for collapsing the current through the coil thereby producing a rising voltage across the coil to fire a spark plug, typically coupled across the coil, when the switchable current drive circuit is disabled by the first control signal being in a second logic state. The circuit includes a thermal clamping circuit responsive to a second control signal and coupled to the charging circuit for providing current to the charging circuit to slowly discharge the coil and for clamping the voltage at the coil to a predetermined voltage such that the firing of the spark plug is prevented. The thermal clamping circuit is activated when the temperature of the ignition system exceeds a predetermined temperature.
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Citations
14 Claims
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1. A circuit for driving an inductive load coupled thereto, comprising:
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charging means for providing current through the inductive load when enabled and for inhibiting current through the inductive load when disabled; a control circuit being responsive to a first input logic signal for providing a first output logic signal for enabling and disabling said charging means when said first output logic signal respectively is in a first and second logic state, said control circuit being responsive to a second input logic signal for both providing a second output logic signal and causing said first output logic signal to be in said second logic state; and thermal clamping means responsive to said second output logic signal and being coupled between the inductive load and said charging means for providing current to said charging means thereby enabling said charging means to both discharge the inductive load at a predetermined rate and clamp the voltage across the inductive load to a predetermined voltage wherein a collapse of current through the inductive load is prevented. - View Dependent Claims (2, 3, 4, 5, 6)
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7. In an integrated chip, an ignition coil driver circuit for driving an inductive load coupled thereto, comprising:
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charging means for providing current through the inductive load when enabled and for inhibiting current through the inductive load when disabled; a control circuit being responsive to a first input logic signal for providing a first output logic signal for enabling and disabling said charging means when said first output logic signal respectively is in a first and second logic state, said control circuit being responsive to a second input logic signal for both providing a second output logic signal and causing said first output logic signal to be in said second logic state; and thermal clamping means responsive to said second output logic signal and being coupled between the inductive load and said charging means for providing current to said charging means thereby enabling said charging means to both discharge the inductive load at a predetermined rate and clamp the voltage across the inductive load to a predetermined voltage wherein a collapse of current through the inductive load is prevented. - View Dependent Claims (8, 9, 10, 11, 12)
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13. A method for thermally clamping an ignition coil driver system having switchable current drive means and charging means responsive to the switchable current drive means for charging and discharging an inductive load when the switchable current drive means is enabled and disabled, respectively, the method comprising the steps of:
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disabling the switchable current drive means when the temperature of the ignition coil driver system exceeds a predetermined temperature; sensing a voltage at the inductive load and providing a signal when said voltage at the inductive load exceeds a predetermined threshold; and applying said signal to the charging means for discharging the inductive load at a predetermined rate wherein a collapse of current through the inductive load is prevented. - View Dependent Claims (14)
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Specification