Motorola Corporation

Jeffrey P Kotowski

Brian D Chapman

Kevin M Andrews

Jeffrey T Barylak

Overvoltage protection circuit (10) has a power transistor (11) that drives an inductive load (19). A resistor (16) is connected between an output electrode (14) of the transistor and a control electrode (12) of the transistor, and a constant current source (18) is also connected to the control electrode. The resistor and constant current source determine an effective zener voltage to limit the maximum voltage which can exist at the transistor output electrode (14), and this is accomplished without the use of a zener diode while utilizing a minimum number of components. This effective zener diode voltage can be readily adjusted by adjusting either the magnitude of the resistor (16) or the constant current source (18).

Overvoltage protection circuit

A transistor sense electrode (20) is coupled to the input branch (24) of a current mirror (22). The current mirror's branch (26) carries a current substantially equal to the current in the input branch to indicate the current flowing in the transistor. A preferred embodiment includes an amplifier (30) which senses the difference between the voltage at the sense electrode (20) and a reference voltage (Vx). The sensed difference in voltage causes the amplifier to apply a control signal to the current mirror to vary the current in the input branch so as to hold the sense electrode's voltage at the level of the reference voltage (Vx). A preferred package for the system's circuitry is also disclosed.

System for sensing and/or controlling the level of current in a

A method and apparatus is disclosed for measuring and/or controlling the level of current in a Sense FET which includes a power transistor (M1) and a sense transistor (M2). The transistors (M1) and (M2) are both biased to operate in a linear mode, and the Vds of the sense transistor (M2) is compared to a predetermined fraction of the Vds of the power transistor (M1). A control signal is generated that is representative of the results of the comparison, and, in one embodiment, that control signal is used in a feedback arrangement to drive the Vds of the sense transistor (M2) to the predetermined fraction of the Vds of the power transistor (M1). Consequently, the level of current carried by the sense transistor (M2) is caused to be equal to the same predetermined fraction of the current carried by the power transistor (M1).

Current monitoring and/or regulation for sense FET's

A fixed volume receiving cavity (18) of a fuel injector (11) receives fuel from a fuel inlet valve means (23, 24) in accordance with the time duration(T.sub.A) of fuel metering control signal pulses (100). Injection occurrence control signal pulses ( b 101) actuate a compressed air inlet valve means (26-30) connected to the cavity to inject the contents of the cavity through an outlet valve (20) and into a combustion chamber (15) of an engine. The fuel metering pulses (100) are developed by a microprocessor (50). Circuitry (53-66; 70-79,66) separate from and external to the microprocessor receives the fuel metering control signal pulses and provides, in response thereto, the fuel injection occurrence control signal pulses. Use of a fixed volume receiving cavity in the injector, in combination with the time-controlled fuel inlet valve means, eliminates many mechanical likages required in most prior injectors. Deriving the fuel injection occurrence signal pulses from the fuel metering signal pulses allows the microprocessor to produce only a single output signal (Y) to implement fuel injection control.

Growing community of inventors

Rolling Meadows, IL, United States of America

Jeffrey P Kotowski