Patent ID: 8004338
Filing Date: 2011-08-23
Classification: H03K

Abstract:
1. A pulse generator comprising; a first periodic voltage generating circuit which charges and discharges a first capacitor and generates a first periodic voltage that periodically repeats a first changing time-period in which a voltage value changes from a first initial value towards a first main target value with a constant slope; a first main comparator which compares a voltage value of the first periodic voltage with the first main target value, and generates a first main switching signal that makes a level transition when these values are equal; a second periodic voltage generating circuit which charges and discharges a second capacitor and generates a second periodic voltage that periodically repeats a second changing time-period in which a voltage value changes from a second initial value towards a second main target value with a constant slope; a second main comparator which compares a voltage value of the second periodic voltage with the second main target value, and generates a second main switching signal that makes a level transition when these values are equal; and a pulse output circuit which uses the level transition of the first main switching signal and the second main switching signal to output a pulse signal in which an edge appears when the voltage value of the first periodic voltage reaches the first main target value from the first initial value and the voltage value of the second periodic voltage reaches the second main target value from the second initial value; wherein the first periodic voltage generating circuit uses the level transition of the second main switching signal that occurs when the voltage value of the second s eriodic voltage reaches the second main target value from the second initial value, to start the first changing time-period, and the second periodic voltage generating circuit uses the level transition of the first main switching signal that occurs when the voltage value of the first periodic voltage reaches the first main target value from the first initial value, to start the second changing time-period, and wherein the pulse generator further comprises: a first sub-comparator which compares the voltage value of the first periodic voltage with a first sub-target value between the first initial value and the first main target value, and generates a first sub-switching signal that makes a level transition when these values are equal; and a second sub-comparator which compares the voltage value of the second periodic voltage with a second sub-target value between the second initial value and the second main target value, and generates a second sub-switching signal that makes a level transition when these values are equal; wherein the first periodic voltage generating circuit and the second periodic voltage generating circuit are configured such that the first changing time-period and the second changing time-period have equal lengths, and the pulse output circuit uses the level transitions of the first sub-switching signal and the second sub-switching signal to output a pulse signal in which an edge appears when the voltage value of the first periodic voltage reaches the first sub-target value from the first initial value and when the voltage value of the second periodic voltage reaches the second sub-target value from the second initial value.