Switch control device, power supply device comprising the same, and driving method of power supply device utilizing turn-on period half-on time point detection

1. A power supply comprising:

a rectification circuit configured to be coupled to an AC input and generate an input voltage and an input current;

a power switch configured to receive the input current from the rectification circuit during an on-period; and

a switch controller configured to:

detect a half-on time point that is a half time point of the on-period;

detect a sense voltage based on a current flowing to the power switch during the on-period at the half-on time point;

generate a modulation wave based on a reference wave and the detected sense voltage; and

control switching operation of the power switch based on the modulation wave.

2. The power supply of claim 1 , wherein the switch controller is configured to:

generate a current sense voltage based on the sense voltage at the half-on time point;

generate a feedback voltage based on a difference between the current sense voltage and a predetermined reference voltage; and

control the reference wave based on the feedback voltage.

3. The power supply of claim 2 , wherein the switch controller comprises:

a current detector configured to generate the current sense voltage based on the sense voltage and a half-on pulse, the half-on pulse being synchronized at the half-on time point;

a feedback unit configured to generate a feedback signal that varies based on a difference between the current sense voltage and the reference voltage; and

a sinewave controller configured to generate the modulation wave based on the feedback voltage and the reference wave.

4. The power supply of claim 3 , wherein the current detector comprises:

a buffer including an input terminal configured to receive the sense voltage;

a detection switch having an input connected to an output terminal of the buffer and performing switching based on the half-on pulse; and

a capacitor coupled to an output of the detection switch, the capacitor configured to store the sense voltage transmitted through the detection switch.

5. The power supply of claim 3 , wherein the feedback unit comprises:

an error amplifier configured to generate an output by amplifying a difference between the reference voltage and the current sense voltage; and

a capacitor configured to be charged by the output of the error amplifier.

6. The power supply of claim 1 , wherein the switch controller includes a half-on detector configured to sample a voltage charged during an on-period of the previous switching cycle of the power switch into the half as a half-on reference voltage, and further configured to sense a time point that a voltage charged during an on-period of a present switching cycle reaches the half-on reference voltage as the half-on time point.

7. The power supply of claim 6 , wherein the half-on detector comprises:

a sampling/reset signal generator configured to generate a sampling signal and a reset signal that are synchronized based on a turn-off time point of the power switch;

a charging unit configured to generate an on-period voltage that is determined by an on-period of the power switch;

a sampling unit configured to sample the on-period voltage based on the sampling signal and to generate a half-on reference voltage; and

a half-on pulse generator configured to generate a half-on pulse synchronized at the half-on time point based on a comparison of the half-on reference voltage and the on-period voltage.

8. The power supply of claim 7 , wherein the sampling/reset signal generator comprises:

an inverter outputting an inverse level of a gate voltage that controls switching operation of the power switch;

a first delay unit configured to generate a first delay signal based on the gate voltage delayed by a predetermined first delay period;

an AND gate generating a sampling signal by performing AND operation with an output of the inverter and the first delay signal of the first delay unit; and

a second delay unit configured to generate a second delay signal based on the sampling signal delayed by a predetermined second delay period.

9. The power supply of claim 7 , wherein the charging unit comprises:

a capacitor,

a current source configured to generate a charging current, and

a reset switch switched according to the reset signal, wherein said reset switch is configured to charge the capacitor during the on-period of the power switch.

10. The power supply of claim 7 , wherein the sampling unit comprises:

a sampling switch configured to provide the on-period voltage to a first node based on the sampling signal

a capacitor connected between the first node and a ground; and

a first and a second resistor coupled in series between the first node and a ground,

wherein a voltage at a second node between the first resistor and the second resistor is the half-on reference voltage.

11. The power supply of claim 7 , wherein the half-on pulse generator comprises:

a comparator configured to generate a comparator signal based on a comparison between the on-period voltage and the half-on reference voltage;

an inverter configured to generate an inverse signal based on an inverse of the comparator signal;

a delay unit configured to generate a delayed signal based on the inverse signal delayed by a third delay period; and

an AND gate generating the half-on pulse by performing AND operation with the delayed signal and the comparator signal.

12. The power supply of claim 1 , wherein the reference wave is synchronized with a frequency of the AC input.

13. The power supply of claim 12 , wherein the switch controller detects one cycle of the input voltage by sensing a zero voltage crossing time point of the input voltage, and generates the reference wave, wherein a cycle of said reference wave corresponds to one cycle of the input voltage.

14. The power supply of claim 1 , wherein the reference wave is a DC voltage.

15. A method for driving a power supply, comprising:

providing an input current through a power switch from an AC current during an on-period of the power switch;

detecting a half-on time point that is a half time point of the on-period;

detecting a sense voltage based on a current flowing to the power switch at the half-on time point;

generating a modulation wave by controlling a reference wave based on the detected sense voltage; and

switching the power switch based on a result of the comparison between the modulation wave and the sense voltage,

wherein the reference wave is synchronized with a frequency of the AC input.

16. The method for driving the power supply of claim 15 , wherein detecting the sense voltage at the half-on time point comprises generating a current sense voltage by storing the sense voltage in a capacitor at the half-on time point.

17. The method for driving the power supply of claim 15 , wherein generating the modulation wave comprises generating a feedback voltage based on a difference between the current sense voltage and a predetermined reference voltage and controlling the reference wave based on the feedback voltage.

18. The method for driving the power supply of claim 15 , wherein controlling the reference wave according to the feedback voltage comprises multiplying the feedback voltage to the reference wave.

19. The method for driving the power supply of claim 15 , wherein detecting the half-on time point comprises:

sampling a voltage charged during an on-period of the previous switching cycle of the power switch into the half as a half-on reference voltage, and

sensing a time point that a voltage charged during an on-period of the present switching cycle reaches the half-on reference voltage as the half-on time point.

20. The method for driving the power switch of claim 15 , wherein switching the power switch comprises turning off the power switch when the sense voltage reaches the modulation wave.

21. A switch controller of a power supply that converts an AC input according to switching operation of the power switch, comprising:

a half-on detector configured to:

sample a voltage charged during an on-period of the previous switching cycle of the power switch into the half as a half-on reference voltage, and

sense a time point that a voltage charged during on-period of the present switching cycle reaches the half-on reference voltage as a half-on time point;

a current detector configured to generate a current sense voltage based on the sense voltage at the half-on time point;

a feedback unit configured to generate a feedback voltage based on a difference between the current sense voltage and a predetermined reference voltage; and

a sinewave controller configured to control a reference wave based on the feedback voltage.

22. The switch controller of claim 21 , wherein the half-on detector comprises:

a sampling/rest signal generator configured to generate a sampling signal and a reset signal that are synchronized based on a turn-off time point of the power switch;

a charging unit configured to generate an on-period voltage that is determined by an on-period of the power switch;

a sampling unit configured to sample the on-period voltage based on the sampling signal and to generate a half-on reference voltage; and

a half-on pulse generator configured to generate a half-on pulse synchronized at the half-on time point based on a comparison of the half-on reference voltage and the on-period voltage.