Patent ID: 8872495

Claim:
A DC-DC converter circuit comprising: a DC-DC converter IC; and an enable control circuit arranged to receive a control signal; wherein the DC-DC converter IC is arranged to: input, via an input terminal connected to a power supply input line, a direct-current voltage converted from an alternating-current voltage and supplied by the power supply input line; output a direct-current voltage having a value converted by operation of the DC-DC converter IC; and operate when a voltage of a specified threshold value or greater is input from an enable terminal; the enable control circuit is arranged to make the voltage input to the enable terminal equal to the threshold voltage or greater when the direct-current voltage supplied from the power supply input line reaches a specified value; the control signal is input into the enable control circuit from a later stage circuit arranged to receive the output direct-current voltage; the enable control circuit includes a zener diode that includes a cathode connected to a side of the power supply input line and an anode connected to a side of the enable terminal, and when the input direct-current voltage supplied from the power supply input line becomes the specified value or greater, the zener diode inputs the voltage to the enable terminal; and the zener diode is arranged in series between the power supply input line and the enable terminal.