Abstract: A pulse generator includes a mode controller that detects a state in which there has been no transition of a pulse signal to the off level for a given cycle (period). When such a state is detected, the pulse generator transits to a skip mode. In the skip mode, the period is repeatedly switched between: (i) a first period in which the pulse signal is maintained at the on level over multiple cycles; and (ii) a second period in which the pulse signal is forcibly switched to the off level so as to charge the bootstrap capacitor by means of a bootstrap circuit.

Abstract: A bootstrap power supply circuit generates a constant voltage VCCBST for charging a bootstrap capacitor. An output transistor is configured as an N-channel MOSFET arranged such that its drain is connected to an input line and such that its source is connected to an output line. A constant voltage circuit connected to the gate of the output transistor stabilizes the gate voltage VG to a constant value. A variable impedance circuit is arranged between the input line and the gate of the output transistor, in order to provide a variable impedance. An impedance controller controls the impedance of the variable impedance circuit according to the state of a step-down DC/DC converter.

Abstract: The present invention relates to improving the reliability of the control IC of DC/DC converters. The present invention provides a control IC 200 of a rectifier diode-type buck DC/DC converter 100. An N-channel DMOS switch transistor M1 is disposed between an input terminal VCC and a switch terminal LX. A first diode D11 and an N-channel DMOS low-side transistor M2 are connected in series with and disposed between the switch terminal LX and a ground terminal GND.

Abstract: A pulse generator includes a mode controller that detects a state in which there has been no transition of a pulse signal to the off level for a given cycle (period). When such a state is detected, the pulse generator transits to a skip mode. In the skip mode, the period is repeatedly switched between: (i) a first period in which the pulse signal is maintained at the on level over multiple cycles; and (ii) a second period in which the pulse signal is forcibly switched to the off level so as to charge the bootstrap capacitor by means of a bootstrap circuit.

Abstract: A bootstrap power supply circuit generates a constant voltage VCCBST for charging a bootstrap capacitor. An output transistor is configured as an N-channel MOSFET arranged such that its drain is connected to an input line and such that its source is connected to an output line. A constant voltage circuit connected to the gate of the output transistor stabilizes the gate voltage VG to a constant value. A variable impedance circuit is arranged between the input line and the gate of the output transistor, in order to provide a variable impedance. An impedance controller controls the impedance of the variable impedance circuit according to the state of a step-down DC/DC converter.

Abstract: The present invention relates to improving the reliability of the control IC of DC/DC converters. The present invention provides a control IC 200 of a rectifier diode-type buck DC/DC converter 100. An N-channel DMOS switch transistor M1 is disposed between an input terminal VCC and a switch terminal LX. A first diode D11 and an N-channel DMOS low-side transistor M11 are connected in series with and disposed between the switch terminal LX and a ground terminal GND.