Patent ID: 8847810

Claim:
A pulse phase difference coding circuit, comprising: a pulse delay circuit which is formed by connecting a plurality of delay elements in a ring shape, and transmits a pulse signal with the pulse signal being delayed by the delay elements after a pulse for activation representing an activation timing is inputted; a count unit which counts the number of circulations of the pulse signal in the pulse delay circuit; a circulation position detecting unit which detects the position of the pulse signal circulating in the pulse delay circuit when a pulse for measurement representing a measurement timing is inputted; a circulation number detecting unit which detects the number of circulations of the pulse signal in the pulse delay circuit when the pulse for measurement is inputted; and a coding unit which outputs numeric data representing the number of stages of the delay elements through which the pulse signal has passed in the pulse delay circuit during the time period between the input of the pulse for activation and the input of the pulse for measurement, based on the position of the pulse signal detected by the circulation position detecting unit and the number of circulations detected by the circulation number detecting unit; wherein the count unit includes a plurality of partial counters connected to each other in series so that the most significant bit of an output of the previous stage serves as an operation clock of the subsequent stage, and the circulation number detecting unit includes: a first latch circuit which is provided for each of the partial counters and latches an output of the partial counter according to the pulse for measurement, and a first delay circuit which treats the partial counter in the second stage or later as an object counter and delays the pulse for measurement by a total delay time in all the partial counters located at the previous stages of the object counter, the pulse for measurement being inputted into the first latch circuit which latches an output of the object counter.