Abstract: A duty cycle converter is provided for converting a pulsed input signal exhibiting a first duty cycle to a pulsed output signal exhibiting a second duty cycle. The converter includes an output pulse generator which synchronizes the leading edge of each output pulse with the leading edge of each input pulse. A first capacitor is charged to a first voltage level in response to a first input pulse. A second capacitor is switchably coupled to the first capacitor and, in response to a second input pulse, causes the voltage across the first capacitor to decrease to a second voltage level. A third capacitor is charged to the first voltage level in response to the second input pulse. A comparator determines when the voltage on the third capacitor increases to become equal to the second voltage level on the first capacitor.

Abstract: In a pulse duty ratio discrimination circuit for discriminating duty ratios of input signals by comparing a count value with a threshold value through means of counting, with a counter using clocks, a time period starting with a reference level changing point occurring every predetermined period in the input signal and ending with a level returning point, the present invention is characterized by a pulse duty ratio discrimination circuit that includes not only period determination means for determining the periods of the input signals by resetting the count value of the counter at the period of the input signal and by comparing actual count values for a plural number of count patterns of the counter established in advance, but also clock selection means for selecting the frequency of the clock based on a determination result of the period determination means.

Abstract: A process variable such as the load current supplied through an electrical contactor is encoded as a 4 to 20 mA current signal via an optically coupled pulse width modulated output circuit. A microprocessor produces the pulse width modulated signal at a duty cycle varying with the load current. The LED of an opto-coupler transfers the signal to a phototransistor, and a voltage regulator and switching circuit drive the phototransistor so as to minimize switching times. The voltage regulator maintains a DC voltage at the collector of the phototransistor, which is operated at a constant emitter current. The LED supplies base current to the phototransistor when the pulse width modulated signal is high. An amplifier is coupled to the emitter of the phototransistor, and the output of the amplifier is coupled back to the base of the phototransistor via a Schottky diode pair. The amplifier output varies with whether or not the base current needed to maintain constant emitter current is obtained from the LED.

Abstract: A vertical ramp generator includes a voltage controllable charge current source and a switched discharge current source coupled across a ramp capacitor. A pair of comparators coupled to first and second reference potentials are supplied with the ramp capacitor voltage and drive a flip/flop, the output of which operates the discharge current source. A sync signal voltage is injected into the output of one of the comparators. Another comparator compares the ramp capacitor voltage with a third reference potential corresponding to the midpoint of the desired ramp voltage to control the switching of a pair of current sources that supply a square wave current to a correction capacitor which develops a DC correction voltage. The duty cycle of the square wave current is a function of the deviation of the ramp capacitor voltage from the third reference potential. The correction voltage controls the amount of current supplied by the charge current source.

Abstract: The technique of measuring the duty cycle of a digital signal of known repetition rate is disclosed. It makes use of the fact that the probability of the digital signal being at the high level is related to its duty cycle when the signal is sampled at a frequency incoherent with the repetition rate. The apparatus in one embodiment includes a random sampler for sampling the digital signal under measurement, and digital counters which count the total number of samples and the number of samples whose values are at one of the two digital levels.