An exemplary DC-DC converting circuit (2) includes an input terminal (20), a regulating circuit (21), a bleeder circuit (23), an output terminal (25), a voltage-controlling terminal (26), and a load (24). The input terminal, the regulating circuit, the bleeder circuit, and the output terminal are connected in series. The output terminal is grounded via the load. The voltage-controlling terminal is configured to supply a controlling voltage that controls the regulating circuit, and the bleeder circuit is configured to supply a stable divided voltage to the output terminal for output.