between the cathode terminal and the anode terminal since the load voltage vz makes the cathode terminal and the anode terminal short circuit or open the current flowing through the resistor r 0 204 is controlled for example the shunt regulator 210 performs the control so as to make the voltage drop based on the resistor r 0 204 constant to stably supply the voltage to the load 202 the capacitor c 0 218 may be a capacitor for removing ripple components the capacitor c 0 218 removes the ripple components that occur based on the switching function of the shunt regulator 210 difference current corresponding to the difference between the limited current value i 0 and the load current iz flowing through the load 202 may be referred to as the current ib 1 the current ib 2 the secondary battery bt 1 230 is charged with the current ib 1 in the current ib 1 the current ib 2 and the secondary battery bt 2 236 is charged with the current ib 2 in the current ib 1 the current ib 2 when the load current iz flowing through the load 202 becomes smaller than the current i 0 flowing through the resistor r 0 204 the voltage drop based on the resistor r 0 204 is decreased the decrease in the voltage drop based on the resistor r 0 204 increases the load voltage vz to be applied to the load 202 if the load voltage vz increases to a value higher than or equal to a certain value the shunt regulator 210 makes the cathode terminal and the anode terminal short circuit the occurrence of the short circuit between the cathode terminal and the anode terminal of the shunt.