Analog voltage isolation circuit

Abstract

An analog voltage isolation circuit includes an error amplifier-integrator having an error-output voltage, which is compared to a selected value referenced to the same ground potential as the input signal being measured. The comparator output varies the current flowing through the series-connected light-emitting diodes of first and second opto-isolators. The output of the first opto-isolator, with respect to the input ground potential, generates a first current fedback to the error amplifier-integrator, to establish both the frequency and duty-cycle of a rectangular-wave signal periodically varying proportional to the magnitude of the input voltage. The foregoing constitutes a first subcircuit for generating a pulse-width-modulated (PWM) electrical parameter having at least one of a frequency and a duty cycle variably responsive to an input signal value; the same periodically-varying current flows a second subcircuit, isolated from the first subcircuit, for converting the PWM parameter to an output signal substantially equal to the input signal. The current flows through the second opto-isolator input circuit, to generate an output voltage which varies substantially linearly with variance of the circuit input voltage signal, but is referenced to another ground potential, isolated from the input signal ground potential.

Dependencies are inferred from the claim text.