Caterpillar Inc.

Long T Le

Paul C Gottshall

A high side driver circuit includes a command voltage source, a first switching transistor having a base connected to the command voltage source, an emitter connected to ground, and a collector connected to a second switching transistor base. The second switching transistor includes an emitter connected to an electrical energy source through an internal voltage source. A power transistor includes a gate connected to the second switching transistor collector through a resistor, a drain connected to the electrical energy source through a sense resistor, and a source connected to a load. A diagnostic circuit portion including a comparator establishes a diagnostic output voltage based upon the state of the power transistor and characteristics of the power transistor drain and source for indicating fault conditions of the driver circuit.

High side driver circuit with diagnostic output

A low side driver circuit includes a command voltage source, a first switching transistor having a base connected to the command voltage source, an emitter connected to ground, and a collector connected to a second switching transistor base. The second switching transistor includes an emitter connected to a first reference voltage. A power transistor includes a gate connected to the second switching transistor collector through a first resistor, a drain connected to an electrical energy source through a load, and a source connected to ground through a sense resistor. A second resistor is connected between the power transistor gate and ground. A diagnostic circuit portion including a first comparator and a second comparator establishes a diagnostic output voltage based upon the voltages at the power transistor drain, gate and source for indicating fault conditions of the driver circuit.

Low side driver circuit with diagnostic output

In one aspect of the present invention, a zero crossing detecting circuit is disclosed. The circuit includes a first comparator having an inverting and non-inverting input connected to an input signal. The non-inverting input of the first comparator is further connected to the first comparator output to provide a feed forward path. A second comparator is additionally included having an output connected to the first comparator inverting input. This provides the inverting input of the first comparator with a reference voltage that is substantially equal to that of the first comparator non-inverting input; thereby, providing the first comparator with balanced inputs.

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Peoria, IL, United States of America

Long T Le