Pulse-width modulating circuitry e.g. for controlling motor vehicle solenoid valves - has comparator blocking switching transistor when voltage on capacitor is below reference value but otherwise makes conductive

摘要

The circuitry includes the inductive load, e.g. a solenoid valve (5), as well as a switching transistor (9) and a current-source (3). The appliance load channel of the switching transistor (9) and a current source (3) are connected in series between a supply potential (US) and ground. A capacitor (4) is connected across the series-circuits of the consumer (5) and the transistor (9) load channel. The specified value selected at terminal (1) is set via a control device (2) in relation to the comparator's (10) output signal in order to generate a proportional output signal with a pulse-width modulated (PWM) control signal derived from the comparator's output signal and used to drive the controlled current source (3) providing a constant current for charging either capacitor (4) or the inductive consumer, i.e. solenoid valve (5). ADVANTAGE - Precise control of appliance current with low circuitry easily integratable.