Motorola Corporation

Randall T Wollschlager

John M Hargedon

Keith M Wellnitz

John M Pigott

A half-bridge driver provides a current limit on the low-side driver (20) and a current limit on the high-side driver (16). The current limits are initially set equal. If the low-side driver current limits, then a modulation current from the low-side driver increases the high-side driver current limit threshold to maintain stable operation of the control circuits. In addition, the present invention provides dual conduction paths to charge the main conduction transistor of the low-side driver, while detecting current limit. When current limit is detected, the charging current to the main conduction transistor is switched to current limit mode.

Circuit and method of current limiting a half-bridge driver

A clamp circuit (50) for protecting a MOSFET (52) from destructive voltages includes a clamping element (56), a Zener diode (64), two current mirrors (66 and 62), a current switch (58), a reference current source (68), and a voltage detector (72). When a drain voltage of the MOSFET (52) rises above a clamping voltage of the clamp circuit (50), a clamping current exceeding a current in the current switch (58) flows through the clamping element (56) and activates the MOSFET (52). During the activation, the two current mirrors (66 and 62) generate an output current exceeding a reference current in the reference current source (68) and raise a voltage at an input terminal of the voltage detector (72). The voltage detector (72) generates a signal indicating the activation of the clamp circuit (50), thereby indicating that the clamp circuit (50) and its inductive load (74) are intact.

Clamp circuit and method for detecting an activation of same

An actuator movement detector (10) indicates proper engagement of a solenoid (12). The current flowing through a field coil (16) is converted to a sense voltage that exponentially increases and then follows a dip before increases again to a steady state value greater than the first peak value. The exponentially increasing sense voltage is stored across a capacitor (24). Any AC variation about the stored sense voltage sets the output state of comparators (30, 32) and determines a first peak value of the sense voltage. After the first peak, a counter (44) must count to a predetermined value during the low peak before the sense voltage returns to its first peak value. If the counter reaches at least the predetermined count value before returning to its first peak value and count back down to zero before reaching steady state, then the solenoid is considered engaged.

Circuit and method of detecting actuator movement

A single ended input comparator circuit having an input inverter stage and a voltage reference circuit is provided. The voltage reference circuit modulates the voltage appearing across the inverter stage thereby varying the switching threshold voltage level of the inverter stage and providing hysteresis for the comparator circuit. Further, by appropriately choosing the widths and lengths of the transistors used in the inverter stage and the voltage reference circuit, a zero temperature coefficient for the comparator circuit is achieved.

Zero temperature coefficient comparator circuit with hysteresis

A device including a first semiconductor PN junction which is reverse biased to operate in the avalanche breakdown region. A second semiconductor PN junction is biased to operate in the forward active region such that carriers are injected through the second semiconductor PN junction and diffuse to the first semiconductor PN junction wherein the noise generated from the first semiconductor PN junction operating in the avalanche breakdown region is substantially reduced.

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Chandler, AZ, United States of America

Randall T Wollschlager