In the present invention, a pump driving circuit includes a step-up unit that steps up a first DC voltage from a power supply and outputs it as a second DC voltage, and an H bridge unit that has first and second series circuits that each include two switching elements connected in series between a high potential corresponding to the second DC voltage and a reference potential. According to a control signal from the control unit, the two switching elements of the first series circuit and the two switching elements of the second series circuit are switched on and off. A voltage generated between a first contact point between the two switching elements of the first series circuit, and a second contact point between the two switching elements of the second series circuit is used as a driving voltage for driving a pump.
