Waveform crossing detector

Patent · Tue Jan 22 04:00:00 EST 1985

OSTI ID:5865638

Gilliam, J E

A waveform crossing detector circuit for a pair of waveforms of a three-phase AC supply applied to respective input terminals. The circuit includes a pair of opto-couplers for isolating an output terminal from the supply. In order to obtain an accurate indication of the instants of crossing the light-emitting diodes of the couplers are driven by respective transistors which act as the actual crossing detectors. The collector circuits of these transistors are driven from the third phase, the potential of which is at a maximum when the relevant instants occur. Two further such arrangements may be connected to the taps of an input potential divider in a cyclical manner and the output signals of the three resulting arrangements combined by means of logic gates to produce pulses which occur once every 60/sup 0/ of the input waveform. The output signal may be used as a reference signal to enable control signals for thyristors included in a control circuit for apparatus energized from the AC supply.

• Assignee: US Phillips Corportion
• Patent Number(s): US 4495461
• OSTI ID: 5865638
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420800* -- Engineering-- Electronic Circuits & Devices-- (-1989)
CONTROL SYSTEMS
DETECTION
ELECTRONIC CIRCUITS
LIGHT EMITTING DIODES
SEMICONDUCTOR DEVICES
SEMICONDUCTOR DIODES
THYRISTORS
TRANSISTORS
WAVE FORMS