JPS5797458A - Phase difference detector - Google Patents

Abstract

PURPOSE:To perform the digital display of a phase difference between two signals having the same frequency with simple constitution by using a dual slope type analog/digital converter which uses the same reference voltage source in common for a charging voltage source and a discharging voltage source. CONSTITUTION:Two input signals having the same frequency are applied to terminals 14 and 16 and then supplied to a phase difference detector 22. A phase difference theta between those two input signals is converted into signals (c) and (d) by a detector 22 to control the connections of changeover switches 24 and 32. Only while the signal (c) is at a high level, the output signal (e) of the switch 24 is at +EsV and the output signal (f) of the switch 32 is at 0V, so that an integrator 12 integrates the +EsV signal when the signal (c) is at the high level. Then, a zero potential is applied to the integrator 12 and the uninverted input terminal of an operational amplifier 30 rises up to +EsV, so that the output (g) of the integrator 12 rises by +EsV. The voltage V0 of this signal (g) is expressed by V0=Es(T2-T1)N/CR, where C is the capacity of a capacitor 38 and R is the resistance value of a resistor 28 and when N(T2-T1)=T0, T0=NT(1- theta/pi), calculating the phase difference theta.