Reference point potential compensating circuit for use with phase controller

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT Referring to FIG.
4, the primary side of a transformer T.
sub.
1 is connected to a power supply N and the secondary is connected to a resistance R.
sub.
4 and capacitor C.
sub.
4.
The impedance of and voltage across capacitor C.
sub.
4 increases as the frequency changes from 60 to 50 Hz.
The capacitor voltage is rectified through a diode D.
sub.
2 and smoothed by a smoothing circuit comprising capacitors C.
sub.
2, C.
sub.
3 and a resistance R.
sub.
3.
A detected voltage appears at point e and is a function of the power supply frequency and/or amplitude as can be seen in FIGS.
2 or 3 respectively.
This detected voltage corresponds to the voltage V.
sub.
p or V.
sub.
p.
sub.
' in FIGS.
2 or 3.
V.
sub.
p acts as a gate voltage for a programmable unijunction transistor PUT.
The signal developed at terminal a corresponds to V.
sub.
c of FIGS.
1-3.
V.
sub.
c may be taken directly or developed from the power supply N and in FIG.
4, the waveform shown at terminal a is derived by full-wave rectifying the output signal from power supply N.
The signal developed at terminal c corresponds to V.
sub.
d of FIGS.
1-3.
V.
sub.
d is a sensing signal, the amplitude of which varies with changes in the value of the parameter being sensed or measured.
Thus, if temperature is the parameter to be sensed and regulated, V.
sub.
d, in the embodiment of FIG.
4, decreases in value as the temperature increases and vice versa.
This may be done by inserting a phase inverting amplifier between the sensor and the diode D.
sub.
1.
Of course, depending on circuit design, V.
sub.
d could increase with increasing temperature and decrease with decreasing temperature.
At terminal d, the composite signal, V.
sub.
c + V.
sub.
d, as shown in FIGS.
1-3 is formed.
This composite signal is applied to the anode of unijunction transistor PUT.
Transistor PUT fires when the anode voltage, V.
sub.
c + V.
sub.
d, slightly exceeds the gate voltage, V.
sub.
p, to discharge capacitor C.
sub.
1, through transistor PUT and the pulse transformer in the cathode circuit thereof