Voltage regulator, particularly for automotive use

Abstract

To improve the regulating response of an automotive-type, solid-state voltage regulator and render it essentially immune to ripple while additionally permitting complete integration of the entire voltage regulator without external discrete filter capacitors, a difference amplifier has the output voltage of the on-board vehicle network, for example from an alternator, applied thereto for comparison with a reference, the difference amplifier, respectively, controlling a capacitor charge current supply and a discharge current drain circuit, both connected to a small capacitor in the order of, for example, only 30 pF which, hence, can be integrated, the voltage across the capacitor being sensed in a high-low window or range-type discriminator which has a dual-state output to control conduction or non-conduction of a transistor in series with the field of the alternator in dependence upon whether the voltage across the capacitor, as it is being charged or drained, is above an upper threshold or below a lower threshold of the discriminator. Preferably, the circuit includes current mirror circuits in which currents in one branch are reflected in another to provide for balance, temperature compensation, and to render the circuit immune to variations in loading on the alternator.