Electronic Circuits and Tutorials
Electronics Schematics - P

Phase Sensors and Detectors Circuits

Simple Phase Meter operates to 10 MHz: 07/04/96 EDN-Design Ideas

Typical Application Circuit for Motor Phase Current Sensing

Phase Detector (Type II) - This circuit probably won't actually work; the resistors are wrong. Note that, when a comparator is on, the 10k and 4.7k form a resistor divider that only allows the CMOS gate's input to reach 2/3 +V. The correct wiring, which is on my original induction heater control circuit, has the resistors going to +V. (Note: that circuit is itself faulty, as I soon realized I needed the greater phase margin of a type II over the type I shown.) That said, operation is as follows: the comparators, 100pF capacitors and CD4001B inverter-wired-NORs constitute rising-zero-crossing pulse generators, one for each input, A and B. These pulses, which are perhaps 400ns long (roughly 100pF * 4.7k), set or reset the RS flip-flop. As a result, the flip-flop stays in the high or low state an amount of time corresponding to the delay between edges, in other words, it is a PWM signal proportional to phase. The output filter removes [most of] the switching, leaving a continuous output.

Phase detector - This circuit will detect the input frequency. LED turn-off when it same input frequency.

Phase Locked Loop Phase Detector - In the National Semiconductor LM565 Phase-Locked-Loop seen here in figure 3.2.1, the phase detector is defined as the first subsection in the schematic. Pins 2 and 3 provide an input path for the differential input signal, where pin 5, the phase detector VCO input is connected to pin 4, the VCO output. A Widlar current source integrated throughout the schematic provides the biasing for the phase detector.

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