TWI743834B - Constant on-time controller and buck regulator device using the same - Google Patents

Abstract

A constant on-time controller (COT) includes: a voltage dividing circuit to generate a feedback voltage according to an output voltage of a buck regulator; a current ripple extracting circuit to sense a current from an inductor of a buck regulator, and generate an extracted ripple current having no DC component according to a sensed current; a one-shot on-timer to output a constant-on time control signal according to a regulator input voltage of the buck regulator and the output voltage; a comparing circuit to output a comparison result according to a reference voltage signal, the feedback voltage and the extracted ripple current; and a logic circuit to generate a control signal to the buck regulator according to the comparison result and the constant-on time control signal. The current ripple extracting circuit detects the DC component in the present cycle, and compares the detected DC component with the next cycle.

Description

Constant on-time controller and step-down regulation using constant on-time controller Device

The present invention relates to a step-down regulator, and more particularly to a constant on-time (COT) controller used in a step-down regulator device.

COT controllers have been widely used in step-down regulator devices, which can use a regulator to output voltage ripples and thereby start when the regulator output voltage drops to a reference voltage An on-time. Please refer to Figure 1A. Figure 1A illustrates the current waveform of a switch and the corresponding operation. As shown in FIG. 1A, the on-time (that is, the period during which the corresponding logic level is high) can be terminated by the circuit in response to some conditions (such as referring to the level of the regulator input voltage). During the on-time of the pulse wave, electric energy is directly supplied from the regulated input voltage to the regulated output voltage through the electronic switching device. Similarly, when the pulse showing the on-time is terminated, the electric energy stored in the inductor will be supplied to regulate the output voltage.

A step-down regulator device with a COT controller usually includes a circuit that adjusts the on-time length of the pulse wave by adjusting the input voltage and adjusting the output voltage by reference, so it can still present a nearly constant frequency even when the duty cycle is changed. . Adjust the output voltage ripple (ripple) will be affected by the flow The ripple current on the inductor of the equivalent series resistance (ESR) of the output capacitor has a wide range of changes. If a multilayer ceramic capacitor (MLCC) with only a small equivalent series resistance is used, the voltage ripple from the inductor will also be relatively small. This causes two main problems of the COT controller, namely instability and susceptibility to noise.

Generally speaking, COT controller devices benefit from the characteristics of self-oscillating, simple structure, high efficiency at light loads, and fast load transient response. However, COT controller devices encounter some bottlenecks, such as jitter caused by low noise immunity, severe electromagnetic interference (EMI) problems, the need for equivalent series resistance, and Poor DC regulation. Therefore, there is a need for a novel design to solve the above problems.

An object of the present invention is to provide a constant on-time (COT) controller used in a step-down regulator device to increase the noise boundary of the COT controller while maintaining fast load transient response. (noise margin).

Another object of the present invention is to provide a COT controller used in a buck regulator device to reduce the sensitivity of the COT controller to noise, for example, to greatly reduce non-ideal jitter.

Another object of the present invention is to provide a device for a step-down regulator, which includes a step-down regulator and a COT controller electrically connected to the step-down regulator to solve the instability and susceptibility Issues affected by noise.

In order to at least achieve the above objectives, an embodiment of the present invention provides a COT controller, which includes a voltage divider circuit, a current ripple capture circuit, a single-on timer, a comparison circuit, and a logic Circuit. The voltage divider circuit is used to generate a feedback voltage according to the output voltage of a buck regulator. The current ripple capture circuit is used to sense the current from the inductor of the buck regulator, and generate the captured ripple current without a DC component according to the sensed current. extracted ripple current). The one-shot on-timer is used to output a COT control signal according to the regulated input voltage of the step-down regulator and the output voltage. The comparison circuit is electrically connected to the voltage divider circuit and the current ripple extraction circuit for outputting a comparison result according to a reference voltage signal, the feedback voltage and the extracted ripple current. The logic circuit is electrically connected to the single conduction timer and the comparison circuit for generating a control signal to the step-down regulator according to the comparison result and the constant conduction time control signal. The on-time of the buck regulator is determined according to the constant on-time control signal, and the off-time of the buck regulator is determined according to the comparison result; and the current ripple The wave capture circuit detects the DC component of the sensing waveform in the current cycle at the beginning of the off time of the buck regulator, and the DC component sensed in the current cycle is compared with the lower part of the current cycle. The sensing waveforms in one cycle are compared to generate the captured ripple current.

In addition, another embodiment of the present invention provides a step-down regulator device, which includes a COT controller. The COT controller includes a voltage divider circuit, a current ripple capture circuit, a single-on timer, a comparison circuit, and a logic circuit. The voltage divider circuit is used to generate a feedback voltage according to the output voltage of a step-down regulator. The current ripple capture circuit is used to sense the current from the inductor of the buck regulator, and generate a captured ripple without a DC component based on the sensed current Current. The single-on timer is used for outputting a COT control signal according to the regulated input voltage of the step-down regulator and the output voltage. The comparison circuit is electrically connected to the voltage divider circuit and the current ripple extraction circuit for outputting a comparison result according to a reference voltage signal, the feedback voltage and the extracted ripple current. The logic circuit is electrically connected to the single conduction timer and the comparison circuit for generating a control signal to the step-down regulator according to the comparison result and the constant conduction time control signal. The on-time of the buck regulator is determined according to the constant on-time control signal, and the off-time of the buck regulator is determined according to the comparison result; and the current ripple extraction circuit is in the buck regulator Detect the DC component of the sensing waveform in the current period at the beginning of the off time, and compare the DC component sensed in the current period with the sensing waveform in the next period of the current period to generate the capture Take the ripple current.

According to an embodiment of the present invention, the single-on timer includes a capacitor, a resistor, and a hysteresis comparator. The capacitor is electrically connected to the ground, and the resistor is connected in series with the capacitor. The resistor is used for receiving a first voltage on the inductor, wherein the first voltage changes with the regulating input voltage. The hysteresis comparator is electrically connected to a connection end of the capacitor and the resistor, and is used to compare a second voltage between the connection end of the capacitor and the resistor with the output voltage to generate a hysteresis comparison The result signal is used as the constant on-time control signal.

According to an embodiment of the present invention, the logic circuit is an RS flip flop, and a setting end of the RS flip flop is electrically connected to a comparator and the single-on timer, To receive the comparison result signal and an inversion of the constant on-time control signal, and a reset terminal of the RS-type flip-flop is electrically connected to the single-on timer to receive the constant on-time Control signal.

According to an embodiment of the present invention, the single-on timer includes a capacitor, a current source, and a voltage comparator. The current source is electrically connected to a ground terminal through the capacitor, and generates a current proportional to the regulated input voltage to form a first voltage across the capacitor. The voltage comparator is electrically connected to a connection end of the capacitor and the current source for comparing the output voltage with the first voltage to output the constant on-time control signal.

According to an embodiment of the present invention, the COT controller further includes a ramp generator electrically connected to the comparison circuit for generating a ramp voltage signal, wherein the comparison circuit is based on the feedback voltage and the reference The voltage signal, the ramp voltage signal and the extracted ripple current output the comparison result.

According to an embodiment of the present invention, the current ripple capture circuit includes a current sense amplifier, a sample-and-hold circuit, and a subtractor. The current sense amplifier is used to sense the current from the inductor of the buck regulator to obtain the sense current; the sample/hold circuit is electrically connected to the current sense amplifier for The current is sampled and the measured DC component is held; the subtractor is electrically connected to the current sense amplifier and the sample-and-hold circuit, and is used to subtract the sensed waveform in the next cycle from the current cycle The measured DC component in the current cycle generates the extracted ripple current.

According to an embodiment of the present invention, the comparison circuit includes an amplifier, a capacitor, an adder, and a modulator. The amplifier is used to receive the reference voltage signal and the feedback voltage to generate an adjusted reference voltage signal; the capacitor has two terminals, which are electrically connected to the amplifier and the ground terminal; the adder is electrically connected to the amplifier, To self-correlate to the first one of the captured ripple current A voltage signal is subtracted from the adjusted reference voltage signal to generate a second voltage signal; the modulator is electrically connected to the adder for generating the comparison result according to the second voltage signal and the feedback voltage .

According to an embodiment of the present invention, the comparison circuit includes an adder and a modulator. The adder is used for subtracting the reference voltage signal from the extracted ripple current to generate a second voltage signal; the modulator is electrically connected to the adder for generating a second voltage signal according to the second voltage signal and The feedback voltage is used to generate the comparison result.

According to an embodiment of the present invention, the voltage divider circuit includes a plurality of resistors connected in series with each other.

In summary, the present invention provides an enhanced signal boundary and improved load transient response for a COT controller used in a buck regulator device, and in some embodiments, it can also eliminate or reduce non-ideal jitter. In this way, the COT controller can further have improved stability and immunity.

100: Buck regulator device

11: COT controller

12: Buck regulator

M1, M2: Transistor

121: Pre-drive circuit

122: Electronic Switch Device

V _IN : adjust the input voltage

V _OUT : Adjust the input voltage

R _CO : output resistor

C _O : output capacitor

I _SW : current

111: Current ripple capture circuit

112: Voltage divider circuit

113: comparison circuit

114: One-shot on timer

115: RS type flip-flop

116: ramp generator

V _COT : Voltage signal

R _FBH , R _FBL : resistor

FB: Feedback voltage

L _X : Inductor

R _LOAD : load

V _REF : Reference voltage signal

T _ON , T _ON : signal

S: Setting terminal

R: reset terminal

Q, Q: output

21: Hysteresis comparator

R ₁ : resistor

C ₁ , C ₂ : Capacitor

GND: Ground

31: Current Sense Amplifier

32: sample and hold circuit

33: Subtractor

41: Amplifier

42: adder

43: Modulator

V _REF ': reference voltage signal after adjustment

V _SW : Voltage

R _CO : Resistance value

f _sw : frequency

V _REFX : compare voltage signal

Figure 1A shows the current waveform of a switch and the corresponding operation.

FIG. 1B is a circuit diagram of a step-down regulator device according to an embodiment of the present invention.

FIG. 2A is a circuit diagram of a one-shot on-timer according to an embodiment of the invention.

FIG. 2B is a circuit diagram of a single-on timer according to another embodiment of the present invention.

FIG. 3 is a circuit diagram of a current ripple extraction circuit according to an embodiment of the invention.

FIG. 4A is a circuit diagram of a comparison circuit according to an embodiment of the present invention.

FIG. 4B is a circuit diagram of a comparison circuit according to another embodiment of the present invention.

FIG. 5A is a waveform diagram of a signal of a buck regulator device according to an embodiment of the present invention.

Figure 5B is a less ideal modulation situation of the scheme shown in Figure 5A, which illustrates a situation where the DC value of the sensing current is detected at the end of the off time period.

Figure 5C illustrates the comparison between the schemes of Figure 5A and Figure 5B.

In order to make it easier for those skilled in the art to understand the purpose, features, and effects of the present invention, the present invention provides embodiments and drawings for detailed description.

The embodiment of the present invention provides a step-down regulator device, including a constant on-time (COT) controller (for example, the COT controller 11 in Figure 1B) and a step-down device electrically connected to the COT controller A regulator (such as the buck regulator 12 in Figure 1B), in which a current ripple capture circuit of the COT controller senses the equivalent series resistance (ESR) flowing through an output capacitor from the inductor (It is used to sense the low sense current of the buck regulator) to remove the direct current (DC) component of the sense current, thereby generating an extracted ripple current, and generate a ripple current based on the extracted ripple current The ripple voltage signal is sent to a comparator of the COT controller to increase the noise margin of the COT controller while maintaining a fast load transient response.

In addition, in another embodiment of the present invention, the ramp generator is used in the COT controller to provide a ramp voltage signal to the comparator of the COT controller, the COT sensitivity to noise can be reduced, and jitter The phenomenon can also be substantially reduced. Simply put, the COT controller of the buck regulator device provided above can solve the problems of low stability and sensitivity to noise.

Please refer to Figure 1B. Figure 1B is a circuit diagram of a step-down regulator device according to an embodiment of the present invention. The step-down regulator device 100 includes a COT controller 11 and a step-down regulator electrically connected to the COT controller 11 12. However, the COT controller 11 is not limited to the use of constant on-time. The on and off of the step-down regulator 12 is controlled by the COT controller 11. When the buck regulator 12 is turned on, the COT controller 11 transfers _{the energy of the regulated input voltage V IN} to the regulated input voltage V _OUT through the electronic switch device 122 including transistors M1 and M2. For example, the above operation can be realized by turning on the transistor M1 and turning off the transistor M2. When the transistor M1 is off and the transistor M2 is on, _{the energy stored in the inductor L X} will be supplied to the regulated output voltage V _OUT . Please note that the transistor M1 or M2 used in the present invention can actually be replaced by any type of switching element.

COT controller 11 receives a regulated output voltage V _OUT, and the current I _SW on the sensing inductor L _X, then the current I _SW flows through the equivalent series resistance of an output capacitor (i.e. series and output resistor R _CO The total resistance of the output capacitor C _O ), and the current I _SW is also the low side current of the buck regulator 12. The COT controller 11 generates a feedback voltage FB according to the adjusted output voltage V _OUT , and generates the extracted ripple current according to the sensed current. The COT controller 11 can determine the off time of the buck regulator 12 (that is, the period during which the buck regulator 12 is off) according to the feedback voltage FB and the extracted ripple current, and adjust the input voltage V _{IN according to} And adjust the output voltage V _OUT to determine the conduction time of the buck regulator 12.

In the related art, since the captured ripple current has _{the DC component of the current I SW} , the DC component of the current I _SW will be amplified in the COT controller 11, which makes the noise boundary of the COT controller 11 unsatisfactory, resulting in COT The controller 11 cannot accurately control the closing time of the buck regulator 12. In this way, the aforementioned DC component will bring more voltage drop or voltage overshoot to the load transient, which means that the load transient response will deteriorate. This phenomenon will be further described in the embodiment of FIG. 5C later. In addition, the non-ideal jitter phenomenon in the related art is also a problem that needs to be solved.

The detailed description of the buck regulator 12 is as follows. The buck regulator 12 includes a pre-driving circuit 121 (which can be replaced by a logic circuit), transistors M1 and M2, an inductor L _X , and an output capacitor C _O and an output resistor R _CO , wherein the output load R _LOAD can be electrically connected to the regulated output voltage V _OUT . The output capacitor C _O is electrically connected to the output resistor R _CO in series, wherein the output resistor R _CO is electrically connected to the ground terminal through the output capacitor C _O.

The regulated output voltage V _OUT is electrically connected to the output resistor R _CO and the inductor L _X , and the electronic switching device 122 includes at least transistors M1 and M2 (although the NMOS transistors are depicted in this embodiment, some changes are made in the present invention In the example, PMOS can also be used instead). The gates of the transistors M1 and M2 are electrically connected to the pre-drive circuit 121, the drain of the transistor M1 is electrically connected to the regulated input voltage V _IN , and the source of the transistor M1 is electrically connected to the inductor L _X and the transistor The drain of M2 and the source of transistor M2 are electrically connected to the ground. In other words, the transistors M1 and M2 are electrically connected to the COT controller 11, so that the COT controller 11 can sense _{the current I SW.}

The pre-driving circuit 121 is used to receive a control signal from the COT controller 11 and output a gate control signal to the gates of the transistors M1 and M2 according to the control signal. When the transistor M1 is turned on (at this time the transistor M2 is turned off), the entire step-down regulator 12 will be turned on, so that _{the electrical energy for regulating the input voltage V IN} is transferred to the regulating output voltage V _OUT (that is, the current I _SW will increase); and when the transistor M2 is turned on (at this time the transistor M1 is turned off), the entire buck regulator 12 will be turned off as a result, so that the electrical energy _{stored in the inductor L X will be provided} Adjust the output voltage V _OUT (the current I _SW will therefore decrease).

The details of the COT controller 11 are described as follows. The COT controller 11 includes a current ripple capture circuit 111, a voltage divider circuit 112, a comparison circuit 113, a single-on timer 114, and an RS-type flip-flop ( RS flip flop) 115 and a ramp generator 116. The current ripple capture circuit 111 is electrically connected to the drain of the transistor M2, and is also electrically connected to the comparison circuit 113. The voltage divider circuit 112 is electrically connected to the regulated output voltage V _OUT and the comparison circuit 113. The ramp generator 116 is electrically connected to the comparison circuit 113. The input node of the comparison circuit 113 is electrically connected to the reference voltage signal V _REF , and the output node of the comparison circuit 113 is electrically connected to the RS-type flip-flop 115. The RS-type flip-flop 115 is electrically connected to the pre-driving circuit 121 and the single-on timer 114.

The current ripple capture circuit 111 senses _{the current I SW} flowing through the equivalent series resistance of the output capacitor on the _{inductor L X} (that is, the lower side current of the buck regulator 12) to generate a sensed current, and removes the The DC component in the current is sensed to generate the extracted ripple current (this feature will be described later). Then, the current ripple extraction circuit 111 generates a ripple voltage signal to the comparison circuit 113 according to the extracted ripple current.

The ramp generator 116 is used to generate a ramp voltage signal to the comparison circuit 113, where the ramp voltage signal and the ripple voltage signal are combined into a voltage signal V _COT . As mentioned above, the ramp voltage signal is used to reduce the jitter phenomenon caused by noise. If the jitter phenomenon itself is not serious, the use of the ramp voltage signal can be omitted depending on the situation.

The voltage divider circuit 112 includes resistors R _FBH and R _FBL . The resistor R _FBH is electrically connected to the regulated output voltage V _OUT , the comparison circuit 113 and the resistor R _FBL , and the resistor R _FBL is electrically connected to the ground. The voltage divider circuit 112 generates a feedback voltage FB across the resistor R _FBL according to the adjusted output voltage V _OUT , and the feedback voltage FB is provided to the comparison circuit 113.

The comparison circuit 113 generates the addition result according to the addition of the voltage signal V _COT , the feedback voltage FB and the reference voltage signal V _REF , and outputs the addition result to the setting terminal of the RS-type flip-flop 115 (labeled "S in the figure) "). For example, when _{the addition result of the voltage signal V COT} and the feedback voltage FB is less than the reference voltage signal V _REF , the RS-type flip-flop 115 can output a control signal with a high logic level to the pre-driving circuit 121, so that the pre-driving circuit 121 The gate control signal generated by the driving circuit 121 can turn on the transistor M1 and turn off the transistor M2. In other words, when _{the addition result of the voltage signal V COT} and the feedback voltage FB is less than the reference voltage signal V _REF , the off time of the buck regulator 12 can be terminated.

會分別被輸入至RS型正反器115的一重設端(圖中標示為"R")以及該設定端。 The one-time turn-on timer 114 receives the adjusted input voltage V _IN and the adjusted output voltage V _OUT , and generates the on-time control signal T _ON according to the adjusted input voltage V _IN and the adjusted output voltage V _OUT (as shown in FIG. 2A and FIG. 2B Show) and an inversion signal of the on-time control signal T _ON. On-time control signal T _ON and reverse signal

Will be respectively input to a reset terminal (labeled "R" in the figure) and the setting terminal of the RS-type flip-flop 115.

When the on-time control signal T _{ON is} at a low logic level, the RS-type flip-flop 115 will output a control signal with a high logic level to the pre-driving circuit 121, and the gate control signal generated by the pre-driving circuit 121 will be Turn on transistor M2 and turn off transistor M1. In other words, when the on-time control signal T _{ON is} at a low logic level, the on-time of the buck regulator 12 will end. In this way, the COT controller 11 can control the on time and the off time of the buck regulator 12.

Please note that the implementation of the COT controller 11 in Figure 1B is not a limitation of the present invention. Those skilled in the art can understand that some variations that can achieve the functions of the COT controller 11 of the present invention are also available. Belongs to the scope of the present invention. For example, in a variation, the RS-type flip-flop 115 can be replaced by another type of flip-flop.

Please refer to FIG. 1B and FIG. 2A. FIG. 2A is a circuit diagram of a single-on timer according to an embodiment of the present invention. FIG. 2A may be an example of the single-on timer 114 in FIG. 1B. However, the present invention is not limited to this. The one-time on timer 114 includes a hysteresis comparator 21, a resistor R ₁ and a capacitor C ₁ . The resistor R ₁ is electrically connected to the drain voltage V _SW of the transistor M1 and the source of the transistor M2 (that is, the voltage on one end of the _{inductor L X} ), and is further electrically connected to the ground _{through the capacitor C 1} GND. The positive input terminal of the hysteresis comparator 21 is electrically connected to the regulated output voltage V _OUT , and the negative input terminal of the hysteresis comparator 21 is electrically connected to the capacitor C ₁ and the resistor R ₁ .

The hysteresis comparator 21 compares _{the voltage across the capacitor C 1} with the regulated output voltage V _OUT to output a hysteresis comparison result signal as the on-time control signal T _ON . The voltage V _SW changes as the input voltage V _IN is adjusted. The voltage across the capacitor C ₁ is generated according to the voltage V _SW , and the on-time control signal T _ON is determined according to the voltage V _SW and the adjusted output voltage V _OUT . In other words, the on-time of the buck regulator 12 is determined according to the regulation of the input voltage V _IN and the regulation of the output voltage V _OUT .

Please refer to FIG. 1B and FIG. 2B together. FIG. 2B is a circuit diagram of a single-on timer 114 according to another embodiment of the present invention, but the present invention is not limited thereto. The one-time turn-on timer 114 includes a current source 22, a voltage comparator 23, and a capacitor C _{T_ON} . The current source 22 is electrically connected to a supply voltage VDD, and is electrically connected to the ground _{through the capacitor CT_ON.} The positive input terminal of the voltage comparator 23 is electrically connected to the current source 22 and the capacitor C _{T_ON} , and the negative input terminal of the voltage comparator 23 is electrically connected to the regulated output voltage V _OUT .

The current source 22 generates a current flowing through the capacitor C _{T_ON} according to the regulated input voltage V _IN , wherein the current is proportional to the regulated input voltage V _IN . The current flowing through the capacitor C _{T_ON} forms a voltage V _C across the capacitor C _{T_ON} , and the voltage comparator 23 compares the voltage V _C with the regulated output voltage V _OUT to generate a comparison result signal as the on-time control signal T _ON . Therefore, the on-time of the buck regulator 12 can be determined according to the regulation of the input voltage V _IN and the regulation of the output voltage V _OUT .

Next, please refer to Figure 1B and Figure 3 together. Figure 3 is a circuit diagram of a current ripple capture circuit according to an embodiment of the present invention. Figure 3 is a current ripple capture circuit in Figure 1B. Take an example of the circuit 111, but the invention is not limited to this. The current ripple capture circuit 111 includes a current sense amplifier 31 (denoted as CS_AMP), a sample-and-hold circuit 32 (denoted as S/H), and a subtractor 33. An input terminal of the current sense amplifier 31 is electrically connected to the drain of the transistor M1 and the inductor L _X to receive the low-side current of the buck regulator 12 (that is, the current I _SW ), and the current sense amplifier 31 The other input terminal is electrically connected to the ground terminal. The output end of the current sense amplifier 31 is electrically connected to the subtractor 33 and the sample and hold circuit 32, and the subtractor 33 is electrically connected to the sample and hold circuit 32 and the comparator 113.

The current sense amplifier 31 is used to _{sense the current I SW} , where the sense current is generated by the current sense amplifier 31 and sent to the subtractor 33 and the sample-and-hold circuit 32 (labeled S in Figure 3) /H). The DC component of the sensed current can be sampled and held by the sample-and-hold circuit 32. In addition, the subtractor 33 can subtract the held DC component (that is, the DC component of the previously sensed current) from the sensed current to generate the captured The ripple current is extracted, and the extracted ripple current will be output as a ripple voltage signal. The subtractor 33 can further add the ramp voltage signal from the ramp generator 116 to the ripple voltage signal to form a voltage signal V _COT at the input terminal of the comparison circuit 113.

Next, please refer to FIG. 1B and FIG. 4A. FIG. 4A is a circuit diagram of a comparison circuit according to an embodiment of the present invention. FIG. 4A may be an example of the comparison circuit 113 in FIG. 1B. However, the present invention Not limited to this. The comparison circuit 113 includes an amplifier 41 (labeled AMP), a capacitor C ₂ , an adder 42 and a modulator 43. The output terminal of the amplifier 41 is electrically connected to _{one end of the capacitor C 2} , and the two input terminals of the amplifier 41 are electrically connected to the feedback voltage FB and the reference voltage signal V _{REF respectively} . The other end of the capacitor C ₂ is electrically connected to the ground. The two input terminals of the modulator 43 are electrically connected to the feedback voltage FB and the output terminal of the adder 42 respectively, and the output terminal of the modulator 43 is electrically connected to the RS-type flip-flop 115. The positive input end of the adder 42 is electrically connected to the output end of the amplifier 41, and the negative input end of the adder 42 is electrically connected to the voltage signal V _COT .

According to the feedback voltage FB and the reference voltage signal V _REF , the amplifier 41 can generate an adjusted reference voltage signal V _REF ′. The adder 42 subtracts the voltage signal V _COT from the reference voltage signal V _REF ′ after self-regulation to generate a voltage signal V _REFX . Then, the modulator 43 generates a comparison result according to the voltage signal V _REFX and the feedback voltage FB.

Please note that since the amplifier 41 is only used to adjust the reference voltage signal V _REF , its accuracy will not be affected by the noise boundary compensation, but the present invention is not limited to the above design. FIG. 4B is a circuit diagram of a comparison circuit according to another embodiment of the present invention. In the embodiment of FIG. 4B, the amplifier 41 and the capacitor C _{2 in} FIG. 4A are removed. Therefore, the adder 42 in FIG. 4B adds the reference voltage signal V _REF and the voltage signal V _COT to generate the voltage signal V _REFX , and the modulator 43 generates the comparison result according to the voltage signal V _REFX and the feedback voltage FB.

Next, please refer to FIG. 5A, which is a waveform diagram of the signal of the step-down regulator device 12 according to an embodiment of the present invention. As shown in FIG. 5A, first, the current I _SW increases after the step-down regulator 12 is turned on, and then decreases after the step-down regulator 12 is turned off. The voltage V _SW is a positive value during the on time of the step-down regulator 12 and is negative during the off time of the step-down regulator 12. The sensing current is sampled and held at the beginning of the off time period to obtain the maximum DC value of the sensing current. Because the sensing current will decrease with time during the off time period, detecting the maximum DC value at the beginning of the off time period can obtain a more accurate and accurate DC value, and perform detection at other time points in the off time period. Test will get more unstable results.

For example, please refer to Figure 5B and Figure 5C. Figure 5B is a less ideal modulation situation of the scheme shown in Figure 5A, which illustrates a situation where the DC value of the sensed current is detected at the end of the off time period, and Figure 5C shows the scenario of Figure 5A. Figure and the comparison between the schemes in Figure 5B. In the upper left subgraph of Figure 5C, the DC value will be sampled at the end of the off time period and used to subtract the waveform of the next off time period to obtain the subtraction result. The ideal subtraction result should not contain DC components (for example, the ideal waveform detected in the lower right subgraph of Figure 5C). However, once the detected current changes in the next off time period, the detection result will be incorrect. For example, the detection result in the upper right sub-picture in Fig. 5C still contains a DC component, which causes the COT controller 11 in Fig. 1B to have a non-ideal regulated output voltage V _OUT .

It can be seen from the above that the operation of detecting the maximum DC value at the beginning of the off time period is very helpful to obtain a clean captured ripple current (the term "clean" here can mean no DC component or Contains only a small amount of DC component), which is extremely important for realizing an ideal COT controller device. In other words, if the DC component can be completely removed, is adjusted changes in the input voltage V _OUT (i.e., △ V _OUT) that may be transmitted through I _L △, △ where I _L does not have any DC component. Please refer to the right half of Figure 1B, △V _OUT can be calculated according to the following formula:

Where R _CO represents the resistance value of the resistor _{R CO} , and f _sw represents the frequency used.

As described above, since the capture of the ripple current does not have a DC component of the current I _SW, and therefore it will not last DC component current I _SW is amplified at the COT happens the controller 11, whereby the control can be increased COT The noise boundary of the regulator 11 and the COT controller 11 can accurately control the closing time of the buck regulator 12. Since the accuracy of turning on/off of the buck regulator 12 has been enhanced, the load transient response is also improved accordingly. In addition, considering the jitter caused by noise, the COT controller 11 can further generate a ramp voltage signal, and determine the buck regulator based on the feedback voltage FB, the captured ripple current, and the ramp voltage signal The closing time of 12. With the help of the ramp voltage signal, the sensitivity of the COT controller 11 to noise can be reduced, so the jitter caused by the noise can be reduced. In addition, from the comparison chart of the feedback voltage FB and the extracted ripple current shown in the bottom row of Fig. 5A, it can be seen that the noise boundary of the COT controller is indeed greatly improved.

The DC component of the sensing current can be sampled and held according to the sample-and-hold switch. The ripple current extraction circuit 111 can subtract the held DC component from the current sensed to generate the extracted ripple current. The captured ripple current and the reference voltage signal V _REF can be used to generate the aforementioned comparison voltage signal V _REFX . The feedback voltage FB and the comparison voltage signal V _REFX can be used to determine the turn-off time of the buck regulator 12. In particular, when the feedback voltage FB is less than the comparison voltage signal V _REFX , the off time of the buck regulator 12 will end.

In summary, the present invention provides a COT controller for use in a buck regulator device, and the provided COT controller can obtain the extraction by sensing the current flowing through the equivalent series resistance of the output capacitor on the inductor The ripple current, the extracted ripple current and the feedback voltage can be used to determine the turn-off time of the buck regulator. Since the extracted ripple current does not have a DC component, the COT provided The controller may have an enhanced load transient response. In addition, the above-mentioned jitter phenomenon can be improved by using a ramp voltage signal to compensate for the slope of the captured ripple current, and thereby make the controller have better stability and anti-noise ability.

Although the present invention has been described through specific embodiments, those skilled in the art can make various modifications and changes without departing from the scope and spirit taught in the scope of the patent application of the present invention.

The foregoing descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made in accordance with the scope of the patent application of the present invention shall fall within the scope of the present invention.

100: Buck regulator device

11: COT controller

12: Buck regulator

M1, M2: Transistor

121: Pre-drive circuit

122: Electronic Switch Device

V _IN : adjust the input voltage

V _OUT : Adjust the input voltage

R _CO : output resistor

C _O : output capacitor

I _SW : current

V _SW : Voltage

111: Current ripple capture circuit

112: Voltage divider circuit

113: comparison circuit

114: One-shot on timer

115: RS type flip-flop

116: ramp generator

V _COT : Voltage signal

R _FBH , R _FBL : resistor

FB: Feedback voltage

L _X : Inductor

R _LOAD : load

V _REF : Reference voltage signal

T _ON , T _ON : signal

S: Setting terminal

R: reset terminal

Q, Q: output

Claims (16)

A constant on-time (COT) controller includes: a voltage divider circuit for generating a feedback voltage according to the output voltage of a buck regulator; a current ripple capture circuit, Used to sense the current from the inductor of the buck regulator, and generate an extracted ripple current without a DC component according to the sensed current; a single A one-shot on-timer for outputting a constant on-time control signal according to the regulated input voltage of the step-down regulator and the output voltage; a comparison circuit electrically connected to the voltage divider circuit And the current ripple extraction circuit, the comparison circuit is used for outputting a comparison result according to a reference voltage signal, the feedback voltage and the extracted ripple current; and a logic circuit electrically connected to the single conduction timing And the comparison circuit, the logic circuit is used to generate a control signal to the buck regulator according to the comparison result and the constant on-time control signal; wherein the on-time of the buck regulator is based on The constant on-time control signal is determined, and the off-time of the buck regulator is determined according to the comparison result; and the current ripple capture circuit is a part of the off-time of the buck regulator Start to detect the DC component of the sensing waveform in the current cycle, and compare the sensed DC component of the current cycle with the sensing waveform in the next cycle of the current cycle to generate the acquisition Take the ripple current; wherein the constant on-time controller further includes: a ramp generator, electrically connected to the comparison circuit, for generating a ramp voltage signal; The comparison circuit outputs the comparison result according to the feedback voltage, the reference voltage signal, the ramp voltage signal, and the extracted ripple current. The constant on-time controller according to claim 1, wherein the logic circuit is an RS flip flop, and a setting end of the RS flip flop is electrically connected to a comparator and the A single-on timer to receive the comparison result signal and an inversion signal of the constant on-time control signal, and a reset terminal of the RS-type flip-flop is electrically connected to the single-on timer, To receive the constant on-time control signal. The constant on-time controller according to claim 1, wherein the voltage divider circuit includes a plurality of resistors connected in series with each other. A constant on-time controller includes: a voltage divider circuit for generating a feedback voltage according to the output voltage of a buck regulator; a current ripple capture circuit for sensing the voltage from the buck regulator Adjust the inductor current of the regulator, and generate an extracted ripple current without a DC component according to the sensed current; a one-shot turn-on timer (one-shot) on-timer) for outputting a constant on-time control signal according to the regulated input voltage and the output voltage of the step-down regulator; a comparison circuit electrically connected to the voltage divider circuit and the current ripple capture circuit , The comparison circuit is used for outputting a comparison result according to a reference voltage signal, the feedback voltage and the extracted ripple current; and a logic circuit electrically connected to the single-on timer and the comparison circuit, the logic For circuit A control signal is generated to the buck regulator according to the comparison result and the constant on-time control signal; wherein the on-time of the buck regulator is determined according to the constant on-time control signal, and The off-time of the buck regulator is determined according to the comparison result; and the current ripple capture circuit detects the sensing waveform in the current cycle at the beginning of the off-time of the buck regulator The DC component of the current cycle is compared with the sensed waveform in the next cycle of the current cycle to generate the captured ripple current; wherein the single-shot The on-timer includes: a capacitor; a current source through which the capacitor is electrically connected to a ground and generates a current proportional to the regulated input voltage to form a first voltage across the capacitor; and a voltage comparison The device is electrically connected to a connection end of the capacitor and the current source for comparing the output voltage with the first voltage to output the constant on-time control signal. A constant on-time controller includes: a voltage divider circuit for generating a feedback voltage according to the output voltage of a buck regulator; a current ripple capture circuit for sensing the voltage from the buck regulator Adjust the inductor current of the regulator, and generate an extracted ripple current without a DC component according to the sensed current; a one-shot turn-on timer (one-shot) on-timer), used to adjust the output according to the step-down regulator Input voltage and the output voltage to output a constant on-time control signal; a comparison circuit electrically connected to the voltage divider circuit and the current ripple extraction circuit, the comparison circuit is used for a reference voltage signal, the feedback voltage And the extracted ripple current to output a comparison result; and a logic circuit electrically connected to the single-on timer and the comparison circuit, and the logic circuit is used to control the signal according to the comparison result and the constant on-time Generate a control signal to the buck regulator; wherein the on-time of the buck regulator is determined according to the constant on-time control signal, and the off-time of the buck regulator Is determined based on the comparison result; and the current ripple capture circuit detects the DC component of the sensing waveform in the current cycle at the beginning of the off time of the buck regulator, and the current cycle The sensed DC component is compared with the sensed waveform in the next cycle of the current cycle to generate the captured ripple current; wherein the single-on timer includes: a capacitor electrically connected to the ground ; A resistor in series with the capacitor, the resistor for receiving a first voltage on the inductor, wherein the first voltage changes with the regulation input voltage; and a hysteresis (hysteresis) comparator, electrically connected to A connection end of the capacitor and the resistor, and the hysteresis comparator is used to compare a second voltage between the connection end of the capacitor and the resistor with the output voltage to generate a hysteresis comparison result signal as The constant on-time control signal. A constant on-time controller includes: a voltage divider circuit for generating a reverse voltage according to the output voltage of a buck regulator Feeding voltage; a current ripple capture circuit for sensing the current from the inductor of the buck regulator, and generating a capture without a DC component based on the sensed current Extracted ripple current; a one-shot on-timer for outputting a constant on-time control signal according to the regulated input voltage of the buck regulator and the output voltage; A comparison circuit electrically connected to the voltage divider circuit and the current ripple extraction circuit, the comparison circuit is used for outputting a comparison result according to a reference voltage signal, the feedback voltage and the extracted ripple current; and a A logic circuit is electrically connected to the single-on timer and the comparison circuit. The logic circuit is used to generate a control signal to the buck regulator according to the comparison result and the constant on-time control signal; wherein the buck regulator The on-time of the device is determined according to the constant on-time control signal, and the off-time of the buck regulator is determined according to the comparison result; and the current ripple capture circuit Detect the DC component of the sensing waveform in the current cycle at the beginning of the turn-off time of the buck regulator, and compare the sensed DC component of the current cycle to the next cycle of the current cycle Compare the sensing waveforms to generate the captured ripple current; wherein the current ripple capture circuit includes: a current sense amplifier for sensing the current from the inductor of the buck regulator To obtain the sensed current; a sample/hold circuit electrically connected to the current sense amplifier, the sample and hold circuit for sampling the current and holding the measured DC component; and A subtractor is electrically connected to the current sense amplifier and the sample-and-hold circuit. The subtractor is used to subtract the measured DC component in the current period from the sensing waveform in the next period of the current period to Generate the extracted ripple current. A constant on-time controller includes: a voltage divider circuit for generating a feedback voltage according to the output voltage of a buck regulator; a current ripple capture circuit for sensing the voltage from the buck regulator Adjust the inductor current of the regulator, and generate an extracted ripple current without a DC component according to the sensed current; a one-shot turn-on timer (one-shot) on-timer) for outputting a constant on-time control signal according to the regulated input voltage and the output voltage of the step-down regulator; a comparison circuit electrically connected to the voltage divider circuit and the current ripple capture circuit , The comparison circuit is used for outputting a comparison result according to a reference voltage signal, the feedback voltage and the extracted ripple current; and a logic circuit electrically connected to the single-on timer and the comparison circuit, the logic The circuit is used to generate a control signal to the buck regulator according to the comparison result and the constant on-time control signal; wherein the on-time of the buck regulator is determined according to the constant on-time control signal , And the off-time of the buck regulator is determined according to the comparison result; and the current ripple capture circuit detects the sensing in the current cycle at the beginning of the off-time of the buck regulator Measure the DC component of the waveform, and compare the sensed DC component of the current cycle with the sensed waveform in the next cycle of the current cycle to generate the captured ripple current; The comparison circuit includes: an amplifier for receiving the reference voltage signal and the feedback voltage to generate an adjusted reference voltage signal; a capacitor having two terminals electrically connected to the amplifier and the ground terminal; and an addition A device is electrically connected to the amplifier, and the adder is used to subtract the adjusted reference voltage signal from a first voltage signal associated with the captured ripple current to generate a second voltage signal; and a modulator ( modulator), electrically connected to the adder, and the modulator is used to generate the comparison result according to the second voltage signal and the feedback voltage. A constant on-time controller includes: a voltage divider circuit for generating a feedback voltage according to the output voltage of a buck regulator; a current ripple capture circuit for sensing the voltage from the buck regulator Adjust the inductor current of the regulator, and generate an extracted ripple current without a DC component according to the sensed current; a one-shot turn-on timer (one-shot) on-timer) for outputting a constant on-time control signal according to the regulated input voltage and the output voltage of the step-down regulator; a comparison circuit electrically connected to the voltage divider circuit and the current ripple capture circuit , The comparison circuit is used for outputting a comparison result according to a reference voltage signal, the feedback voltage and the extracted ripple current; and a logic circuit electrically connected to the single-on timer and the comparison circuit, the logic The circuit is used for generating a control signal to the buck regulator according to the comparison result and the constant on-time control signal; The on-time of the buck regulator is determined according to the constant on-time control signal, and the off-time of the buck regulator is determined according to the comparison result; and the current The ripple extraction circuit detects the DC component of the sensing waveform in the current cycle at the beginning of the off time of the step-down regulator, and compares the sensed DC component of the current cycle with the current cycle The sensing waveforms in the next cycle are compared to generate the extracted ripple current; wherein the comparison circuit includes: an adder for subtracting the reference voltage from the extracted ripple current Signal to generate a second voltage signal; and a modulator electrically connected to the adder, and the modulator is used to generate the comparison result according to the second voltage signal and the feedback voltage. A buck regulator device includes: a constant on-time (COT) controller, including: a voltage divider circuit for generating a feedback voltage according to the output voltage of a buck regulator ; A current ripple capture circuit for sensing the current from the inductor of the step-down regulator, and based on the sensed current to generate the extracted ripple without a DC component Current; a one-shot on-timer for outputting a constant on-time control signal according to the regulated input voltage of the step-down regulator and the output voltage; a comparison circuit electrically connected to the The voltage divider circuit and the current ripple extraction circuit, the comparison circuit is used for a reference voltage signal, the feedback voltage, and the extracted Ripple current to output a comparison result; and a logic circuit electrically connected to the single-on timer and the comparison circuit, and the logic circuit is used to generate a control signal according to the comparison result and the constant on-time control signal to The buck regulator; wherein the on-time of the buck regulator is determined according to the constant on-time control signal, and the off-time of the buck regulator is based on the comparison result To determine; and the current ripple capture circuit detects the DC component of the sensing waveform in the current cycle at the beginning of the off time of the buck regulator, and the DC component sensed in the current cycle The component is compared with the sensing waveform in the next period of the current period to generate the captured ripple current; wherein the constant on-time controller further includes: a ramp generator electrically connected to the The comparison circuit is used to generate a ramp voltage signal; wherein the comparison circuit outputs the comparison result according to the feedback voltage, the reference voltage signal, the ramp voltage signal and the extracted ripple current. The step-down regulator device according to claim 9, wherein the logic circuit is an RS flip flop, and a setting end of the RS flip flop is electrically connected to a comparator and the A single-on timer to receive the comparison result signal and an inversion of the constant on-time control signal, and a reset terminal of the RS-type flip-flop is electrically connected to the single-on timer, To receive the constant on-time control signal. The step-down regulator device according to claim 9, wherein the voltage divider circuit includes a plurality of resistors connected in series with each other. A buck regulator device includes: a constant on-time (COT) controller, including: a voltage divider circuit for generating a feedback voltage according to the output voltage of a buck regulator ; A current ripple capture circuit for sensing the current from the inductor of the step-down regulator, and based on the sensed current to generate the extracted ripple without a DC component Current; a one-shot on-timer for outputting a constant on-time control signal according to the regulated input voltage of the step-down regulator and the output voltage; a comparison circuit electrically connected to the A voltage divider circuit and the current ripple extraction circuit, the comparison circuit is used for outputting a comparison result according to a reference voltage signal, the feedback voltage and the extracted ripple current; and a logic circuit electrically connected to the The one-time turn-on timer and the comparison circuit, the logic circuit is used to generate a control signal to the buck regulator according to the comparison result and the constant on-time control signal; wherein the on-time of the buck regulator (on- time) is determined based on the constant on-time control signal, and the off-time of the step-down regulator is determined based on the comparison result; and the current ripple capture circuit is used in the step-down regulator At the beginning of the off time, the DC component of the sensing waveform in the current cycle is detected, and the DC component sensed in the current cycle is compared with the sensing waveform in the next cycle of the current cycle to Generate the captured ripple current; wherein the single-on timer includes: A capacitor; a current source through which the capacitor is electrically connected to a ground terminal to generate a current proportional to the regulated input voltage to form a first voltage across the capacitor; and a voltage comparator electrically connected to the A connection terminal of the capacitor and the current source are used to compare the output voltage with the first voltage to output the constant on-time control signal. A buck regulator device includes: a constant on-time (COT) controller, including: a voltage divider circuit for generating a feedback voltage according to the output voltage of a buck regulator ; A current ripple capture circuit for sensing the current from the inductor of the step-down regulator, and based on the sensed current to generate the extracted ripple without a DC component Current; a one-shot on-timer for outputting a constant on-time control signal according to the regulated input voltage of the step-down regulator and the output voltage; a comparison circuit electrically connected to the A voltage divider circuit and the current ripple extraction circuit, the comparison circuit is used for outputting a comparison result according to a reference voltage signal, the feedback voltage and the extracted ripple current; and a logic circuit electrically connected to the The one-time turn-on timer and the comparison circuit, the logic circuit is used to generate a control signal to the buck regulator according to the comparison result and the constant on-time control signal; wherein the on-time of the buck regulator (on- time) is based on the constant on-time control signal The off-time of the buck regulator is determined according to the comparison result; and the current ripple capture circuit detects the current cycle at the beginning of the off-time of the buck regulator And compare the DC component sensed in the current period with the sensing waveform in the next period of the current period to generate the captured ripple current; wherein The one-time turn-on timer includes: a capacitor electrically connected to the ground; a resistor connected in series with the capacitor, and the resistor is used to receive a first voltage on the inductor, wherein the first voltage is adjusted with the Input voltage change; and a hysteresis (hysteresis) comparator electrically connected to a connection end of the capacitor and the resistor, and the hysteresis comparator is used for a second voltage between the connection end of the capacitor and the resistor It is compared with the output voltage to generate a hysteresis comparison result signal as the constant on-time control signal. A buck regulator device includes: a constant on-time (COT) controller, including: a voltage divider circuit for generating a feedback voltage according to the output voltage of a buck regulator ; A current ripple capture circuit for sensing the current from the inductor of the step-down regulator, and based on the sensed current to generate the extracted ripple without a DC component Current; a one-shot on-timer for outputting a constant on-time control signal according to the regulated input voltage of the step-down regulator and the output voltage; A comparison circuit electrically connected to the voltage divider circuit and the current ripple extraction circuit, the comparison circuit being used for outputting a comparison result according to a reference voltage signal, the feedback voltage and the extracted ripple current; and A logic circuit is electrically connected to the single-on timer and the comparison circuit, the logic circuit is used to generate a control signal to the step-down regulator according to the comparison result and the constant on-time control signal; wherein the step-down The on-time of the regulator is determined according to the constant on-time control signal, and the off-time of the buck regulator is determined according to the comparison result; and the current ripple extraction The circuit detects the DC component of the sensing waveform in the current cycle at the beginning of the turn-off time of the buck regulator, and compares the DC component sensed in the current cycle with the DC component in the next cycle of the current cycle Compare the sensing waveforms to generate the captured ripple current; wherein the current ripple capture circuit includes: a current sense amplifier for sensing the current from the inductor of the buck regulator To obtain the sense current; a sample/hold circuit electrically connected to the current sense amplifier, the sample and hold circuit for sampling the current and holding the measured DC component; and a subtractor , Electrically connected to the current sense amplifier and the sample-and-hold circuit, and the subtractor is used to subtract the measured DC component in the current period from the sense waveform in the next period of the current period to generate the acquisition Take the ripple current. A step-down regulator device includes: a constant on-time (COT) controller, including: A voltage divider circuit for generating a feedback voltage according to the output voltage of a buck regulator; a current ripple extraction circuit for sensing the current from the inductor of the buck regulator, and According to the sensed current to generate the extracted ripple current without a DC component; a one-shot on-timer is used according to the step-down regulator The input voltage and the output voltage are adjusted to output a constant on-time control signal; a comparison circuit is electrically connected to the voltage divider circuit and the current ripple capture circuit, and the comparison circuit is used for according to a reference voltage signal and the feedback Voltage and the extracted ripple current to output a comparison result; and a logic circuit, electrically connected to the single-on timer and the comparison circuit, the logic circuit for controlling the signal according to the comparison result and the constant on-time To generate a control signal to the buck regulator; wherein the on-time of the buck regulator is determined according to the constant on-time control signal, and the off-time of the buck regulator ) Is determined based on the comparison result; and the current ripple capture circuit detects the DC component of the sensing waveform in the current cycle at the beginning of the off time of the buck regulator, and the current The DC component sensed during the period is compared with the sensed waveform in the next period of the current period to generate the captured ripple current; wherein the comparison circuit includes: an amplifier for receiving the reference voltage signal and The feedback voltage is used to generate an adjusted reference voltage signal; a capacitor having two terminals, which are respectively electrically connected to the amplifier and the ground terminal; An adder is electrically connected to the amplifier, and the adder is used for subtracting the adjusted reference voltage signal from a first voltage signal associated with the captured ripple current to generate a second voltage signal; and a modulation A modulator is electrically connected to the adder, and the modulator is used to generate the comparison result according to the second voltage signal and the feedback voltage. A buck regulator device includes: a constant on-time (COT) controller, including: a voltage divider circuit for generating a feedback voltage according to the output voltage of a buck regulator ; A current ripple capture circuit for sensing the current from the inductor of the step-down regulator, and based on the sensed current to generate the extracted ripple without a DC component Current; a one-shot on-timer for outputting a constant on-time control signal according to the regulated input voltage of the step-down regulator and the output voltage; a comparison circuit electrically connected to the A voltage divider circuit and the current ripple extraction circuit, the comparison circuit is used for outputting a comparison result according to a reference voltage signal, the feedback voltage and the extracted ripple current; and a logic circuit electrically connected to the The one-time turn-on timer and the comparison circuit, the logic circuit is used to generate a control signal to the buck regulator according to the comparison result and the constant on-time control signal; wherein the on-time of the buck regulator (on- time) is determined based on the constant on-time control signal, and the off-time of the step-down regulator is based on the comparison result To determine; and the current ripple capture circuit detects the DC component of the sensing waveform in the current cycle at the beginning of the off time of the buck regulator, and the DC component sensed in the current cycle The component is compared with the sensed waveform in the next cycle of the current cycle to generate the extracted ripple current; wherein the comparison circuit includes: an adder for self-correlation with the extracted ripple current The reference voltage signal is subtracted to generate a second voltage signal; and a modulator is electrically connected to the adder, and the modulator is used to generate the comparison result according to the second voltage signal and the feedback voltage.

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