Object of the present invention is to provide a power-on and / or when the power supply is turned off, the current control type DC-DC converter, the control circuit and its control method capable of smoothly ramp control the output voltage of the current control type DC-DC converter . ; And the flip-flop circuit for switching control of the main switching element of the DC-DC converter, is connected to the set terminal of the flip-flop circuit, when the DC-DC converter is in a transition state between the stationary state and the normal operation state, the oscillation frequency DC provided with an oscillation circuit for outputting an oscillation signal which gradually increases or decreases according to the increase or decrease of the output voltage of the -DC converter. The output voltage is, the longer the gradually increasing, gradually lowering the oscillation frequency of the oscillation signal in the process of gradually rising, falling gradually to the time interval that is set in the conduction state the main switch device. Without excessive electric power is supplied with respect to the output voltage, it may be the output voltage to a smooth ramp.
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