Abstract: A first overcurrent detecting unit to detect whether or not a current supplied from a power source unit to an external device exceeds a first criterion value. A second overcurrent detecting unit to detect whether or not the current supplied from the power source unit to the external device exceeds a second criterion value that is a criterion value higher than the first criterion value, a timer unit in which a time corresponding to a time from a time point at which switching from electric power supplied from the power source unit to the external device in a period, in which a negotiation is performed, to electric power corresponding to a result of the negotiation with the external device is performed to a time before the supply of the electric power becomes stable is set.

Abstract: A first overcurrent detecting unit to detect whether or not a current supplied from a power source unit to an external device exceeds a first criterion value. A second overcurrent detecting unit to detect whether or not the current supplied from the power source unit to the external device exceeds a second criterion value that is a criterion value higher than the first criterion value, a timer unit in which a time corresponding to a time from a time point at which switching from electric power supplied from the power source unit to the external device in a period, in which a negotiation is performed, to electric power corresponding to a result of the negotiation with the external device is performed to a time before the supply of the electric power becomes stable is set.

Abstract: A switching power supply includes: transformer 60 which includes a primary winding and a secondary winding and outputs, through the secondary winding, an AC voltage based on the current supplied to the primary winding; switching element 61 which controls current supply to the primary winding; rectifying/smoothing circuit 65 which converts the AC voltage output from the secondary winding into a DC voltage; voltage detecting circuit 62 which detects the DC voltage converted by rectifying/smoothing circuit 65; feedback amplifier 63 which is supplied with the DC voltage detected by voltage detecting circuit 62 as one input and which is supplied with a reference voltage as the other input, so as to output a difference between the input voltage values; and control circuit 64 which controls switching element 61, so as to eliminate the difference detected at feedback amplifier 63.

Abstract: A switching power supply includes: transformer 60 which includes a primary winding and a secondary winding and outputs, through the secondary winding, an AC voltage based on the current supplied to the primary winding; switching element 61 which controls current supply to the primary winding; rectifying/smoothing circuit 65 which converts the AC voltage output from the secondary winding into a DC voltage; voltage detecting circuit 62 which detects the DC voltage converted by rectifying/smoothing circuit 65; feedback amplifier 63 which is supplied with the DC voltage detected by voltage detecting circuit 62 as one input and which is supplied with a reference voltage as the other input, so as to output a difference between the input voltage values; and control circuit 64 which controls switching element 61, so as to eliminate the difference detected at feedback amplifier 63.

Abstract: A discharge lamp energizing power supply device has a full-wave rectifier circuit for rectifying an AC voltage obtained from a commercial AC power supply system into a full-wave rectified waveform, a booster circuit for boosting the voltage of the full-wave rectified waveform, a boosted-voltage changing circuit for changing the boosted voltage output from the booster circuit, a voltage lowering circuit for lowering an output voltage from the boosted-voltage changing circuit and outputting an activating output voltage for activating a discharge lamp and an energizing output voltage for keeping the discharge lamp energized, and a control device for controlling a boosted voltage in the boosted-voltage changing circuit within a predetermined range based on the voltage of the full-wave rectified waveform when the voltage lowering circuit outputs the energizing output voltage.

Abstract: A discharge lamp energizing power supply device is operable to reduce an electric power loss in a wide range of commercial power supply voltages employed in various parts of the world, and can stably perform its functions without causing a functional shutdown of a boosting circuit due to an increase in the power supply voltage and a functional shutdown of a voltage lowering circuit due to a characteristic deterioration of a discharge lamp.