In a switching voltage power supply, a series regulator circuit interconnects an input voltage section (44) with an output voltage section (20B) of the switching power supply.

The current detecting section is driven with a voltage outputted from the power supply voltage generating section.

The first voltage generating section and the second voltage generating section are connected in parallel, and output a constant bias voltage to a common bias voltage output terminal.

A switching section (13) drives the FET so that an output voltage detected at an output voltage detecting section (12) converges to a target voltage.

In a switching voltage power supply, a series regulator circuit interconnects an input voltage section (44) with an output voltage section (20B) of the switching power supply.

The voltage supply section generates the drive voltage, which is obtained by power-amplifying the reference voltage.

A proximal section in mechanical communication with the core-wire's distal section transmits tension, provided by a tensioning element (20), to the distal section.

The piezoelectric conversion section generates an AC voltage in accordance with the oscillation of the beam section.

On the other hand, the voltage control section controls current flowing through the switching section for stabilizing the DC input voltage at the switching section.

A booster circuit section (24) supplies a current to the capacitor (25), and a voltage measuring section (27) measures the voltage of the capacitor (25).

A voltage measuring section (182) measures an output voltage of the fuel cell (150).

A bias voltage supply section (12) supplies a bias voltage to the light receiving element (11).

A voltage holding section for holding a predetermined voltage level is connected to the wiring segment.

A voltage control section controls a drive voltage for operating the light emission controlling section on the basis of a second control signal.

A correcting section is provided to correct the set voltage based on the detection voltage stored in the storage section to compensate for a variation in detection voltage when the actual flow rate of fluid is zero.