Clamping circuit, power supply device including the same and driving method of power supply device

1. A power supply comprising:

a power switch;

a primary wire configured to receive an input voltage;

an auxiliary wire coupled electromagnetically with the primary wire; and

a switch control circuit configured to:

sense the input voltage during an input voltage detection period in a start-up period;

generate an input sense voltage corresponding to the sensed input voltage using a current supplied for clamping a voltage which is resistance-divided from the auxiliary voltage to a predetermined voltage;

determine a peak voltage by detecting a peak of the input sense voltage;

determine a clamping voltage in an inverse relationship with the peak voltage;

generate a comparison voltage according to an output;

clamp the comparison voltage to the clamping voltage during the start-up period; and

control a switching operation of the power switch using a comparison voltage.

2. The power supply of claim 1 ,

wherein the switch control circuit senses the input voltage using an auxiliary voltage of the auxiliary wire during an input voltage detection period in the start-up period.

3. The power supply of claim 1 , wherein the switch control circuit further comprises:

an operational amplifier configured to generate the comparison voltage using a first source current during the start-up period; and

a first source current source configured to supply the first source current.

4. The power supply of claim 3 , wherein the first source current source supplies the first source current to the operational amplifier during a remaining period, excluding an input voltage detection period in the start-up period, and

supplies the first source current to the operational amplifier during an increasing period in the input voltage detection period.

5. The power supply of claim 3 , wherein the switch control circuit further comprises a second source current configured to supply a second source current to the operational amplifier in a normal state after termination of the start-up period.

6. A driving method of a power supply including a primary wire connected to an input voltage and a power switch connected to the primary wire, comprising:

controlling a switching operation of the power switch using a comparison voltage generated according to an output;

determining a clamping voltage by sensing the input voltage during a start-up period by sensing the input voltage, detecting a peak voltage of the sensed input voltage and determining the clamping voltage in an inverse relationship with the peak voltage; and

clamping the comparison voltage to the clamping voltage during the start-up period,

wherein the power supply further comprises an auxiliary wire coupled with the primary wire; and

sensing the input voltage comprises generating an input sense voltage corresponding to the sensed input voltage using a current supplied to clamp a voltage which is resistance-divided from an auxiliary voltage of the auxiliary wire to a predetermined voltage during an input voltage detection period in the start-up period.

7. The driving method of the power supply of claim 6 , wherein the detecting the peak voltage comprises determining the peak voltage by detecting a peak of the input sense voltage.

8. The driving method of the power supply of claim 6 , further comprising generating the comparison voltage using a first source current during the start-up period.

9. The driving method of the power supply of claim 8 , wherein the generating the comparison voltage comprises:

supplying the first source current to a capacitor during a remaining period, excluding the input voltage detection period in the start-up period; and

supplying the first source current to the capacitor during an increasing period in the input voltage detection period.

10. A clamping circuit for clamping a comparison voltage determined according to an output of a power supply, comprising:

an input voltage detector configured to:

sense an input voltage of the power supply during a start-up period;

generate an input sense voltage corresponding to the sensed input voltage using a current supplied for clamping a voltage which is resistance-divided from the auxiliary voltage to a predetermined voltage; and

determine a peak voltage by detecting a peak of the input sense voltage; and

a clamping voltage generator configured to determine a clamping voltage in an inverse relationship with the peak voltage and to generate the clamping voltage,

wherein the comparison voltage is clamped to the clamping voltage during a start-up period.

11. The clamping circuit of claim 10 , wherein the input voltage detector senses the input voltage using an auxiliary voltage of an auxiliary wire electromagnetically coupled to a primary wire of the power supply during the start-up period.

12. The clamping circuit of claim 10 , further comprising:

a connection switch configured to be turned on during the start-up period; and

a clamper connected to the comparison voltage through the connection switch during the start-up period, and configured to clamp the comparison voltage to the clamping voltage.