DC-DC converter and control circuit for DC-DC converter

A control circuit for a DC-DC converter that generates an output voltage from an input voltage, wherein the DC-DC converter includes a first transistor for receiving the input voltage, a second transistor connected to the first transistor, and a comparator, connected to the second transistor, for detecting current flowing through a choke coil to generate a switching control signal for controlling the second transistor to turn on and off, wherein the choke coil is connected to a node between the first transistor and the second transistor, wherein the control circuit controls the first transistor to turn on and off so as to keep the output voltage constant, the control circuit comprising:

• a pulse generation circuit for generating a pulse signal for turning off the second transistor during a predetermined period from before the first transistor is turned on to after the first transistor is turned on,
• wherein the pulse generation circuit comprises:
• a first one-shot circuit for generating a first one-shot pulse signal which has a first pulse width;
• and
• a second one-shot circuit for generating a second one-shot pulse signal, which has a second pulse width that is greater than the first pulse width,
• wherein the first transistor is turned off for a period corresponding to the first pulse width based on the first one-shot pulse signal, and the second transistor is turned off for a period corresponding to the second pulse width based on the second one-shot pulse signal.

A method for controlling a DC-DC converter that generates an output voltage from an input voltage, wherein the DC-DC converter includes a first transistor for receiving the input voltage, a second transistor connected to the first transistor, and a comparator, connected to the second transistor, for detecting current flowing through a choke coil to generate a switching control signal for controlling the second transistor to turn on and off, the method comprising:

• controlling the first transistor to turn on and off so as to keep the output voltage constant;
• detecting current flowing through the choke coil connected to a node between the first transistor and the second transistor;
• and
• controlling the second transistor to turn on and off based on the current detected, wherein said controlling the second transistor includes generating a pulse signal so as to turn off the second transistor during a predetermined period from before the first transistor is turned on to after the first transistor is turned on,
• wherein the first transistor and the second transistor are controlled using a first one-shot pulse signal that has a first pulse width and a second one-shot pulse signal that has a second pulse width, the second pulse width being greater than the first pulse width,
• wherein the first transistor is turned off for a period corresponding to the first pulse width based on the first one-shot pulse signal, and the second transistor is turned off for a period corresponding to the second pulse width based on the second one-shot pulse signal.