摘要 |
At an occasion of a level transition when a second periodic voltage becomes equal to a main reference voltage a first periodic voltage generating circuit starts a first monotonically changing time-period in which a voltage value of a first periodic voltage increases monotonically from 0, which is an initial value, towards a voltage value of the main reference voltage. At an occasion of a level transition of a first main switching signal when the first periodic voltage becomes equal to the main reference voltage, a second periodic voltage generating circuit starts a second monotonically changing time-period in which a voltage value of the second periodic voltage increases monotonically from 0, which is an initial value, towards a voltage value of the main reference voltage.
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