Quick-On/Off Fuel Injector Control using Nexperia MOSFETs

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Member of the PartQuest Explore Development Team. Focused on modeling and simulation of analog, mixed-signal and multi-discipline systems covering a broad range of applications, including power electronics, controls and mechatronic systems.

Description

This fuel injector and driver example is similar to a companion design that can be found here:https://explore.partquest.com/node/644381In that design, repetitive avalanche rated Power MOSFETs are used to rapidly reduce the solenoid current at the end of the injection event, improving timing control of the fuel injector turn-off.In this design, a voltage doubler circuit is used to improve control of the injector's turn-on behavior. As shown in a separate test schematic:https://explore.partquest.com/node/645255The injector solenoid current rise time is strongly affected by the applied voltage from the drive cirit. A significant reduction in the time required for the current to reach 3A is observed as the supply voltage is increased from 12V to 24V, followed by diminishing returns as that voltage is further increased.This implies that a simple voltage doubler circuit, as shown here in the upper left of the schematic, will improve the turn-on response. The doubler circuit's operation is quite simple. The Nexperia BUK9M85-60E Power MOSFETs M3 and M4 are rapidly and alternately switched on and off. When M4 is ON, the low side of C1 is pulled to ground and the battery charges C1 via diode d2 and inductor L1. When M4 is turned OFF and M3 is turned ON, the low side of C1 is raised up to the battery voltage, so that current flows from the high side of C1, via L1 and diode d2, to charge the output capacitor C2. Depending on the load current, this process can raise the output voltage up to approximately 2x the battery voltage. Note that this a is simple open loop operation, no voltage feedback mechanism is use to regulate the output voltage.

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