Abstract: A cellular telephone charging circuit using a dry battery and capable of displaying a charging operation by a light-emitting diode (LED) when the charging operation is actually carried out is provided. The cellular telephone charging circuit using the dry battery as a power supply and including a boost switching regulator that supplies a predetermined charging power to a charging terminal of a cellular telephone, includes: the LED for displaying the charging operation; a control circuit that generates an ON and OFF control signal for driving a boost chopper included in the boost switching regulator; a chopper ON-period detection circuit that detects an ON-period of the boost chopper; and an LED lighting circuit that drives the LED when the ON-period detected by the chopper ON-period detection circuit reaches a predetermined value.