US 4,835,486 A · Isolation amplifier with precise timing of signals coupled across isolation barrier

Abstract

A low cost, high frequency isolation amplifier includes a first voltage-to-frequency converter producing a first pair of complementary pulses in response to an analog input signal and applying them to a pair of low capacitance capacitors constituting the isolation barrier. The isolation barrier differentiates edges of the first pair of pulse signals and applies the resulting signals to inputs of a sense amplifier including a differential amplifier, a pair of comparators, and a flip-flop to precisely reconstruct the first pair of complementary pulse signals, which then are fed into a decoder circuit including a phase locked loop. The phase locked loop includes a phase detector receiving the reconstructed pair of complementary pulse signals and a second pair of complementary pulse signals produced by a second voltage-to-frequency converter. The output of the phase detector is integrated by a filter circuit, the output of which produces a voltage that represents the analog input signal and causes the output of the second voltage-to-frequency converter to be synchronized with the second pair of complementary pulse signals when the analog output signal matches the analog input signal.

Claims10

Dependent claims

A digital isolation circuit comprising in combination:

(a) first means for producing a first pulse signal and a second pulse signal that is the logical complement of the first pulse signal;
(b) first and second isolation barrier means for coupling a portion of each of the first and second pulse signals, respectively, from the first means to a first terminal and a second terminal;
(c) means for differentiating the first and second pulse signals as they are coupled across the first and second isolation barrier means, respectively, to produce differentiated third and fourth pulse signals each having certain edges with times of occurrence corresponding precisely to times of occurrence of the certain edges of the first pulse signal;
(d) means for amplifying the third and fourth pulse signals to produce a differential signal;
(e) first and second comparators;
and
(f) means for applying the differential signal to inputs of the first and second comparators to cause the first and second comparators to sense relative positive and negative excursions of the differential signal, and thereby cause the first and second comparators to switch at times precisely corresponding to times of occurrence of leading and trailing edges, respectively, of the first pulse signal.

4 more elements

Dependencies are inferred from the claim text.

Isolation amplifier with precise timing of signals coupled across isolation barrier

Life of this patent

Isolation amplifier with precise timing of signals coupled across isolation barrier

Life of this patent

Abstract

Claims10