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MOSFET DIRECT INJECTION SHORT CIRCUIT PROTECTION

IP.com Disclosure Number: IPCOM000245288D
Publication Date: 2016-Feb-25
Document File: 3 page(s) / 53K

Publishing Venue

The IP.com Prior Art Database

Related People

TAVARES Eugene - CONTINENTAL Automotive Systems, Inc.: INVENTOR

Abstract

A typical approach to detecting a short circuit to power or ground on a solenoid fuel injector is to monitor the voltage drop across the MOSFET and compare to a maximum programmed threshold. The problem encountered with this approach is that this threshold is normally set high to accommodate the worst case RDSon of the MOSFET at high temperature. The proposed approach seeks to detect the short circuit to power or ground sooner by continually comparing the VDS of the high side to the VDS low side MOSFET to insure that they are within a specified margin of each other.

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Continental Automotive Systems, Inc.

Inventor Information:

Eugene Tavares

           MOSFETDIRECT INJECTION SHORT CIRCUIT PROTECTION SCOPE OF INVENTION

A typical approach to detecting a short circuit to power or ground on a solenoid fuel injector is to monitor the voltage drop across the MOSFET and compare to a maximum programmed threshold. The problem encountered with this approach is that this threshold is normally set high to accommodate the worst case RDSon of the MOSFET at high temperature. The proposed approach seeks to detect the short circuit to power or ground sooner by continually comparing the VDS of the high side to the VDS low side MOSFET to insure that they are within a specified margin of each other.

PRIOR ART DESCRIPTION

There are no known systems having similar features or solving similar problems.

INVENTION DESCRIPTION

The theory behind this design is that when a short circuit occurs due to either the high side or the low side of the injector shorting to battery or ground, more current will pass through one MOSFET versus the other. This difference in current will lead to a difference in the voltage drop across the high side and low side MOSFET. When this difference in voltage exceeds a preset threshold, the ASIC automatically turns off MOSFETs and sets a fault therefore protecting the MOSFET from high current.

Figure 1 shows a typical Direct injection drive circuit

Figure 2 depicts the proposed diagnostic circuit.

The voltage across each MOSFET is measured by an internal amplifier. The gain is selectable to allow for the use of external MOSFETs with different values of RDSon. Of course if Identical MOSFETS are used for HS and LS then the same gain value would be chosen.

The output of each of these amplifiers is then compared to the output of the other. If the diff...