Fault detection circuit
First Claim
1. Fault detection circuit comprising:
- output driver means having a control terminal and at least one output terminal, current through said output driver means determined by signal magnitude at said control terminal;
load means having first and second end terminals, said second end terminal coupled to said output terminal such that currrent through said output driver means determines current through said load means;
current sense resistor means connected in series with said load means by being coupled between said first end terminal and a fixed reference potential such that current through said resistor means normally corresponds to current through said load means;
current control means coupled to said resistor means for, in response to receiving an enable signal having signal transitions to a predetermined logic state, controlling signal magnitude at said control terminal in accordance with current through said resistor means to effectively provide at least a predetermined minimum current level through said load means during said logic state;
wherein the improvement comprises,fault detection means coupled to said load means for detecting short circuits to said fixed reference potential present at either of said first and second end terminals and providing separate fault detection signals in response thereto; and
fault control means coupled to said fault detection means for altering signal magnitude at said control terminal, in response to said fault detection signals, so as to effectively reduce current through at least one of said output driver means and said load means to prevent damage thereto in the event of a short circuit at any of said end terminals.
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Accused Products
Abstract
In a solenoid fuel injection system, an output transistor (16) receives switching signals to control through current therein which is provided to a solenoid fuel injection coil (11) in series with a current sensing resistor (17). A current control circuit (12) provides pulse width modulation control of solenoid current by monitoring the voltage across the sensing resistor. The fault detection circuit provides separate fault signals for short circuits at either the first or second end terminals (E, H) of the solenoid coil. Separate voltage comparators (18, 23) monitor voltages at the first and second end terminals, and separate delay timers (20, 25) effectively gate the comparator outputs to indicate actual detected short circuits. Each of the fault detection signals sets a fault latch (22) which then acts to reduce current through the output transistor and coil. The fault latch is periodically reset. For a fault detection, the output transistor is protected from excessive current resulting from a short circuit at one end terminal (H). The transistor and coil are also protected from a short circuit at the other end terminal (E) which results in the lack of a current sense signal causing the controller (12) to attempt to maintain the output transistor constantly on.
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Citations
30 Claims
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1. Fault detection circuit comprising:
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output driver means having a control terminal and at least one output terminal, current through said output driver means determined by signal magnitude at said control terminal; load means having first and second end terminals, said second end terminal coupled to said output terminal such that currrent through said output driver means determines current through said load means; current sense resistor means connected in series with said load means by being coupled between said first end terminal and a fixed reference potential such that current through said resistor means normally corresponds to current through said load means; current control means coupled to said resistor means for, in response to receiving an enable signal having signal transitions to a predetermined logic state, controlling signal magnitude at said control terminal in accordance with current through said resistor means to effectively provide at least a predetermined minimum current level through said load means during said logic state; wherein the improvement comprises, fault detection means coupled to said load means for detecting short circuits to said fixed reference potential present at either of said first and second end terminals and providing separate fault detection signals in response thereto; and fault control means coupled to said fault detection means for altering signal magnitude at said control terminal, in response to said fault detection signals, so as to effectively reduce current through at least one of said output driver means and said load means to prevent damage thereto in the event of a short circuit at any of said end terminals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. Fault detection circuit for a fuel injector driver comprising:
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output driver means having a control terminal and at least one output terminal, current through said output driver means determined by signal magnitude at said control terminal; load means, comprising a fuel injector solenoid coil, having first and second end terminals, said second end terminal coupled to said output terminal such that current through said output driver means determines current through said load means; current sense resistor means connected in series with said load means by being coupled between said first end terminal and a fixed reference potential such that current through said resistor menas normally corresponds to current through said load means; current control means coupled to said resistor means for, in response to receiving an enable signal having signal transitions to a predetermined logic state, controlling signal magnitude at said control terminal in accordance with current through said resistor means to effectively provide at least a predetermined minumum current level through said load means during said logic state; wherein the improvement comprises, fault detection means coupled to said load means for detecting short circuits to said fixed reference potential present at either of said first and second end terminals and providing separate fault detection signals in response thereto; and fault control means coupled to said fault detection means for altering signal magnitude at said control terminal, in response to said fault detection signals, so as to effectively reduce current through at least one of said output driver means and said load means to prevent damage thereto in the event of a short circuit at any of said end terminals. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. Fault detection circuit comprising:
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output driver means having a control terminal and at least one output terminal, current through said output driver means determined by signal magnitude at said control terminal; load means coupled to said output terminal such that current through said output driver means determines current through said load means; current sense resistor means coupled to said load means such that current through said resistor means normally corresponds to current through said load means; current control means coupled to said resistor means for, in response to receiving an enable signal having signal transitions to a predetermined logic state, controlling signal magnitude at said control terminal in accordance with current through said resistor means to effectively provide at least a predetermined minimum current level through said load means during said logic state; wherein the improvement comprises, fault detection means coupled to said load means and said current sense resistor means for detecting short circuits by effectively monitoring, during said logic state, the voltage applied across the load means and the current through the load means and providing separate first and second fault detection signals in response to either current through said load means being less than said predetermined minimum current level after a first predetermined delay time after said transition of said enable signal to said predetermined logic state or the voltage applied across said load being below a predetermined level, respectively; and fault control means coupled to said fault detection means for altering signal magnitude at said control terminal, in response to said fault detection signals, so as to effectively reduce current through at least one of said output driver means and said load means to prevent damage thereto in the event of a short circuit. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30)
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Specification