Pulse Width Modulator (PWM)

The electronic control module (ECM) especially for fuel injection in cars processes input data

such as the crank angle sensor(timing sensor), air flow potentiometer output signal etc

which are then compared with the stored data in an n-level memory map from which the microprocessor compute results of these Multi-variable data as a function of engine speed to ACTUATORS i.e injector nozzles. Since these input signals are in analog form,they are converted to digital form using A/D converter.The converted digital signal is now modulated using PULSE WIDTH MODULATION technique in which case the pulse duration (width) which is governed by the clock pulses generated by the timing sensor determines precise times nozzle current flows.This timing signal

drags one leg of the nozzles which are connected in a floating bus (bus rail) to ground when nozzles are open (LO) and (HIGH 5V) when nozzles are closed!.Note that the fuel pump is only to deliver fuel at constant pressure (typically 5.0 bar) to the hydraulic lines between the tank and the injector nozzles.

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