Regulator and operating method thereof

1. A regulator comprising:

a switch array including a plurality of switches connected in parallel and generating an output voltage based on a number of enabled switches from among the plurality of switches;

a feedback circuit generating a feedback voltage which depends on a level of the output voltage;

a first voltage-controlled oscillator generating a first signal having a first frequency which depends on a difference between a reference voltage and the feedback voltage;

a second voltage-controlled oscillator generating a second signal having a second frequency which depends on a difference between the feedback voltage and the reference voltage; and

a switch driver determining a turn-on time point of each of the plurality of switches based on the first signal and determining a turn-off time point of each of the plurality of switches based on the second signal.

2. The regulator of claim 1 , wherein, when the reference voltage is greater than the feedback voltage, the first frequency is greater than the second frequency, and the number of the enabled switches increases depending on a difference between the first frequency and the second frequency.

3. The regulator of claim 1 , wherein, when the feedback voltage is greater than the reference voltage, the second frequency is greater than the first frequency, and the number of the enabled switches decreases depending on a difference between the second frequency and the first frequency.

4. The regulator of claim 1 , wherein, when the reference voltage is equal to the feedback voltage, the first frequency and the second frequency are equal to a reference frequency, and the turn-on time point and the turn-off time point of each of the plurality of switches are repeated at the reference frequency.

5. The regulator of claim 1 , wherein the first voltage-controlled oscillator generates the first signal including a plurality of set signals having different phases and respectively corresponding to the plurality of switches,

wherein the second voltage-controlled oscillator generates the second signal including a plurality of reset signals having different phases and respectively corresponding to the plurality of switches, and

wherein the switch driver turns on the plurality of switches respectively at different time points based on the different phases of the plurality of set signals and turns off the plurality of switches respectively at different time points based on the different phases of the plurality of reset signals.

6. The regulator of claim 5 , wherein the switch driver turns on the plurality of switches respectively corresponding to the plurality of set signals in response to rising edges of the different phases of the plurality of set signals and turns off the plurality of switches respectively corresponding to the plurality of reset signals in response to rising edges of the different phases of the plurality of reset signals.

7. The regulator of claim 1 , further comprising:

a transient detector deactivating the first voltage-controlled oscillator when the level of the output voltage is greater than a first voltage level and deactivating the second voltage-controlled oscillator when the level of the output voltage is smaller than a second voltage level lower than the first voltage level.

8. The regulator of claim 7 , wherein, when the level of the output voltage is greater than the first voltage level, the first voltage-controlled oscillator delays generation of the first signal until the level of the output voltage is smaller than the first voltage level, and

wherein the number of the enabled switches decreases while the generation of the first signal is delayed.

9. The regulator of claim 7 , wherein, when the level of the output voltage is smaller than the second voltage level, the second voltage-controlled oscillator delays generation of the second signal until the level of the output voltage is greater than the second voltage level, and

wherein the number of the enabled switches increases while the generation of the second signal is delayed.

10. A regulator comprising:

a switch array including a plurality of switches connected in parallel between an input terminal and an output terminal;

a feedback circuit generating a feedback voltage which depends on a voltage level of the output terminal;

a bias generator generating a first input signal based on a difference between a reference voltage and the feedback voltage and generating a second input signal based on a difference between the feedback voltage and the reference voltage;

a first voltage-controlled oscillator generating a plurality of set signals having different phases and respectively corresponding to the plurality of switches, based on the first input signal;

a second voltage-controlled oscillator generating a plurality of reset signals having different phases and respectively corresponding to the plurality of switches, based on the second input signal;

a switch driver sequentially turning on the plurality of switches based on respective phases of the plurality of set signals and sequentially turning off the plurality of switches based on respective phases of the plurality of reset signals; and

a transient detector controlling a transfer of the first input signal to the second voltage-controlled oscillator and a transfer of the second input signal to the second voltage-controlled oscillator, based on the voltage level of the output terminal.

11. The regulator of claim 10 , wherein the bias generator generates the first input signal of a level proportional to a difference between the reference voltage and the feedback voltage and generates the second input signal of a level proportional to a difference between the feedback voltage and the reference voltage.

12. The regulator of claim 10 , wherein the first voltage-controlled oscillator includes a first ring oscillator sequentially outputting the plurality of set signals at a time interval which depends on a level of the first input signal, and

wherein the second voltage-controlled oscillator includes a second ring oscillator sequentially outputting the plurality of reset signals at a time interval which depends on a level of the second input signal.

13. The regulator of claim 10 , wherein, during a time when the reference voltage and the feedback voltage are equal, a time interval when each of the plurality of switches is enabled is uniformly maintained, and time intervals when the plurality of switches are enabled are equal.

14. The regulator of claim 10 , wherein, during a time when the reference voltage is greater than the feedback voltage, a time interval when each of the plurality of switches is enabled on increases.

15. The regulator of claim 10 , wherein, during a time when the feedback voltage is greater than the reference voltage, a time interval when each of the plurality of switches is enabled decreases.

16. The regulator of claim 10 , wherein the transient detector includes:

a first comparator generating a first enable signal when the voltage level of the output terminal is smaller than a first voltage level and generating a first disable signal when the voltage level of the output terminal is greater than the first voltage level; and

a second comparator generating a second enable signal when the voltage level of the output terminal is smaller than a second voltage level lower than the first voltage level and generating a second disable signal when the voltage level of the output terminal is smaller than the second voltage level,

wherein the first voltage-controlled oscillator receives the first input signal based on the first enable signal, and

wherein the second voltage-controlled oscillator receives the second input signal based on the second enable signal.

17. The regulator of claim 16 , further comprising:

a network circuit electrically connecting the bias generator and the first voltage-controlled oscillator based on the first enable signal, electrically disconnecting the bias generator from the first voltage-controlled oscillator based on the first disable signal, electrically connecting the bias generator and the second voltage-controlled oscillator based on the second enable signal, and electrically disconnecting the bias generator from the second voltage-controlled oscillator based on the second disable signal.

18. An operating method of a regulator, comprising:

generating an output voltage based on a number of enabled switches from among a plurality of switches included in a switch array;

generating a feedback voltage which depends on a level of the output voltage;

generating a plurality of set signals having a first frequency, which depends on a difference between a reference voltage and the feedback voltage, and having different phases;

generating a plurality of reset signals having a second frequency, which depends on a difference between the feedback voltage and the reference voltage, and having different phases;

sequentially turning on the plurality of switches, depending on respective phases of the plurality of set signals; and

sequentially turning off the plurality of switches, depending on respective phases of the plurality of reset signals.

19. The operating method of claim 18 , wherein, when the reference voltage is greater than the feedback voltage, the first frequency is greater than the second frequency, and a number of enabled switches from among the plurality of switches increases depending on a difference between the first frequency and the second frequency, and

wherein, when the feedback voltage is greater than the reference voltage, the second frequency is greater than the first frequency, and the number of the enabled switches decreases depending on a difference between the second frequency and the first frequency.

20. The operating method of claim 18 , further comprising:

delaying generation of the plurality of set signals until the level of the output voltage is smaller than a first voltage level, when the level of the output voltage is greater than the first voltage level; and

delaying generation of the plurality of reset signals until the level of the output voltage is greater than a second voltage level, when the level of the output voltage is smaller than the second voltage level.