Sawtooth wave generation circuit, buck converter and control method

Abstract

The invention provides a sawtooth wave generating circuit, a step-down converter and a control method, the sawtooth wave generating circuit performs product operation according to a feedback signal and a duty ratio signal to generate a sawtooth wave signal, the slope of the sawtooth wave signal changes along with the duty ratio of the step-down converter, and the slope of the sawtooth wave signal and the duty ratio form a function relationship; wherein the feedback signal represents the output voltage or the input voltage of the buck converter, and the duty ratio signal represents the duty ratio of the buck converter. In the sawtooth wave generating circuit provided by the invention, the slope of the sawtooth wave signal changes along with the change of the duty ratio, and the slope of the sawtooth wave and the duty ratio form a function relationship. Therefore, in the full duty ratio range, the phenomenon of overcompensation of the stability parameter is avoided, and the dynamic response performance can be improved while the system stability is maintained in the full duty ratio range.

Description

Technical Field

[0001] The invention belongs to the field of switching power supplies, and in particular relates to a sawtooth wave generating circuit, a buck converter and a control method. Background Art

[0002] In a DC-DC step-down converter, slope compensation is usually used to reduce the ripple of the output voltage and improve the stability and dynamic performance of the step-down converter. That is, a ramp signal related to the output voltage or output current is introduced into the control loop of the step-down converter.

[0003] For example, Figure 1 As shown, in a single-phase BUCK converter, the feedback of the output voltage Vfb is sent to the input of the error amplifier EA and the comparator COM. The output of the error amplifier EA, Vcomp, is used as the reference value of the comparator COM. Vcomp and Vfb are input to the time generator U1 through the comparator COM. The time generator U1 generates a square wave signal based on the logic signal output by the comparator COM as the driving signal of the power tube in the BUCK converter. In order to deal with the problem of reduced system stability margin due to the low equivalent series resistance of the output capacitor Co, an additional triangle wave signal in phase with the inductor current or a sawtooth wave signal based on the switching frequency is usually added to the system for compensation to improve stability. Similarly, if Figure 2 As shown, in a multi-phase buck converter, a triangular wave signal in phase with the inductor current or a sawtooth wave signal based on the switching frequency may be additionally added to the system for compensation to improve the stability of the system.

[0004] However, when a multi-phase system is running, there is a condition where the inductor current ripple is approximately zero, and the more phases there are, the more duty cycle operating points where the inductor current ripple is approximately zero. Therefore, for applications with a wide duty cycle operating range, when the inductor current ripple is approximately zero, it is impossible to use a triangular wave signal in phase with the inductor current to improve the system's stability margin. Therefore, using a sawtooth wave signal for compensation in a multi-phase system has become a preferred solution for adjusting the system's stability margin. Among them, the existing sawtooth wave generating circuit generates a sawtooth wave signal based on the input voltage, and the slope of the sawtooth wave signal is generally independent of the duty cycle; or, the sawtooth wave generating circuit generates a sawtooth wave signal based on the output voltage, and the slope of the sawtooth wave signal is in a linear relationship with the duty cycle, and the proportional coefficient of the linear relationship is related to the input voltage. However, in actual applications, it is found that when stability compensation is performed within the full duty cycle range, a sawtooth signal whose slope is in a linear relationship with the duty cycle (the proportional coefficient is related to the input voltage) will cause over-compensation of the system stability parameters, resulting in insufficient or over-compensated system stability, and thus failure to achieve a compromise between system stability and dynamic response performance. Summary of the invention

[0005] In order to solve the technical problem in the prior art that the sawtooth wave signal cannot simultaneously meet the stability and dynamic response performance requirements of the BUCK converter in the full range of duty cycle, the present invention proposes a sawtooth wave generating circuit, a buck converter and a control method, wherein:

[0006] The sawtooth wave generating circuit generates a sawtooth wave signal by performing a product operation on the feedback signal and the duty cycle signal, wherein the slope of the sawtooth wave signal follows the duty cycle of the buck converter, and the slope of the sawtooth wave signal is in a functional relationship with the duty cycle;

[0007] The feedback signal represents the output voltage or input voltage of the buck converter, and the duty cycle signal represents the duty cycle of the buck converter.

[0008] Furthermore, the coefficient of the functional relationship is related to the output voltage or the input voltage of the buck converter, and the functional relationship represents the functional relationship between the slope of the sawtooth wave signal and the duty cycle.

[0009] Furthermore, the slope of the sawtooth wave signal is in a linear functional relationship with the duty cycle, and the coefficient of the linear term is related to the output voltage.

[0010] Furthermore, the slope of the sawtooth wave signal is in a quadratic function relationship with the duty cycle, and the coefficient of the quadratic term is related to the input voltage.

[0011] Preferably, the sawtooth wave generating circuit integrates the signal representing the output voltage according to the duty cycle signal during the conduction period of the main power tube to generate a voltage signal that is a function of the duty cycle, and generates the sawtooth wave signal according to the voltage signal.

[0012] In one embodiment, the buck converter is an N-phase buck converter, N is a natural number greater than zero, and the sawtooth wave generating circuit includes:

[0013] N first conversion units, the Nth first conversion unit obtains an Nth current signal according to an Nth feedback signal, the Nth feedback signal represents an output voltage of an Nth phase circuit, and the Nth current signal is proportional to the output voltage of the Nth phase circuit;

[0014] N second conversion units, the Nth second conversion unit integrating the current signal during the conduction period of the main power tube in the Nth phase circuit according to the Nth duty cycle signal to obtain the Nth voltage signal, wherein the Nth duty cycle signal represents the duty cycle of the Nth phase circuit;

[0015] The signal generating unit performs current-voltage conversion according to the N voltage signals output by the N second conversion units to output the sawtooth wave signal.

[0016] In one embodiment, the sawtooth wave circuit further includes: N sampling and holding units, the Nth sampling and holding unit samples and holds the Nth voltage signal when the main power tube in the Nth phase circuit is turned on to output a holding signal, and the signal generating unit outputs the sawtooth wave signal according to the holding signal.

[0017] Preferably, the first conversion unit includes a first transconductance amplifier, and the second conversion unit includes a first capacitor and a first switch.

[0018] The first input end of the first transconductance amplifier receives a feedback signal, the second input end of the first transconductance amplifier is grounded, the positive electrode of the first capacitor is connected to the output end of the first transconductance amplifier, the negative electrode of the first capacitor is grounded, and the first switch is connected in parallel with the first capacitor;

[0019] The first switch is turned off during the conduction period of the main power tube, the output current of the transconductance amplifier is a current signal, and the voltage of the first capacitor is a voltage signal when the main power tube is turned on.

[0020] Preferably, the signal generating unit comprises: a second transconductance amplifier, a second capacitor and a second switch.

[0021] The first input terminal of the second transconductance amplifier receives the voltage signal, the second input terminal of the second transconductance amplifier is grounded, the positive electrode of the second capacitor is connected to the output terminal of the second transconductance amplifier, the negative electrode of the second capacitor is grounded, and the second switch is connected in parallel with the second capacitor.

[0022] Wherein, when the second switch is turned off, the voltage of the second capacitor is the sawtooth wave signal.

[0023] Preferably, the sampling and holding unit includes a third capacitor and a third switch, the third capacitor and the third switch are connected in series, the third switch is turned off when the main power tube is turned on, and the third switch is turned on when the main power tube is turned off, and the third capacitor samples and holds the voltage signal.

[0024] A control method for a buck converter comprises the steps of:

[0025] amplifying an error between an output feedback signal and a reference signal to obtain a compensation signal, wherein the output feedback signal represents an output voltage of the buck converter;

[0026] The output feedback signal, the compensation signal and the sawtooth wave signal are processed and compared to output a logic signal, wherein the slope of the sawtooth wave signal follows the duty cycle of the buck converter, and the slope of the sawtooth wave signal is in a functional relationship with the duty cycle;

[0027] A driving signal is output according to the logic signal, and the driving signal controls the on-off of the power tube in the buck converter.

[0028] Furthermore, the method further comprises the steps of: performing calculation processing on the output feedback signal, the inductor current signal, the compensation signal and the sawtooth wave signal and then comparing them to obtain the output logic signal.

[0029] Further, the sawtooth wave signal is generated by performing a product operation on the feedback signal and the duty cycle signal, and the coefficient of the functional relationship is related to the output voltage or input voltage of the buck converter.

[0030] The feedback signal represents the output voltage or input voltage of the buck converter, the duty cycle signal represents the duty cycle of the buck converter, and the functional relationship represents the functional relationship between the slope of the sawtooth wave signal and the duty cycle.

[0031] Furthermore, the slope of the sawtooth wave signal is in a linear functional relationship with the duty cycle, and the coefficient of the linear term is related to the output voltage.

[0032] Furthermore, the slope of the sawtooth wave signal is in a quadratic function relationship with the duty cycle, and the coefficient of the quadratic term is related to the input voltage.

[0033] A buck converter comprising:

[0034] an operational amplifier circuit, amplifying an error between an output feedback signal and a reference signal to obtain a compensation signal, wherein the output feedback signal represents an output voltage of the buck converter;

[0035] an operation circuit, which performs operation processing on the output feedback signal, the compensation signal, and the sawtooth wave signal and then compares them to obtain an output logic signal, wherein the slope of the sawtooth wave signal follows the duty cycle of the buck converter, and the sawtooth wave signal is in a functional relationship with the duty cycle;

[0036] The driving circuit generates a driving signal according to the logic signal, and the driving signal controls the on-off of the power tube in the buck converter.

[0037] Furthermore, the operation circuit performs operation processing on the output feedback signal, the compensation signal, the sawtooth wave signal, and the inductor current signal and then compares them to output a logic signal.

[0038] Furthermore, the sawtooth wave signal is generated by the sawtooth wave generating circuit described in any one of claims 1-10.

[0039] Furthermore, the buck converter includes an N-phase buck converter, where N is a natural number greater than or equal to 1; when N is greater than 1, each phase circuit is provided with a corresponding drive circuit, and also includes a phase distributor, which distributes the logic signal to the drive circuit of each phase circuit.

[0040] In the sawtooth wave generating circuit proposed by the present invention, the slope of the sawtooth wave signal changes with the change of the duty cycle, and the slope of the sawtooth wave is in a functional relationship with the duty cycle. Therefore, within the full duty cycle range, the phenomenon of over-compensation of the stability parameter is avoided, so that within the full duty cycle range, the dynamic response performance can be improved while maintaining the system stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 and Figure 2 They are circuit diagrams of a single-phase buck converter and a multi-phase buck converter in the prior art respectively;

[0042] Figure 3 This is a structural block diagram of the sawtooth wave generating circuit proposed by the present invention (applied in a single-phase buck converter);

[0043] Figure 4 A circuit diagram of a sawtooth wave generating circuit proposed by the present invention (applied in a single-phase buck converter);

[0044] Figure 5 for Figure 4 The working waveform diagram of the sawtooth wave generating circuit shown;

[0045] Figure 6 This is a structural block diagram of the sawtooth wave generating circuit proposed by the present invention (applied in a multi-phase buck converter);

[0046] Figure 7 A circuit diagram of a sawtooth wave generating circuit proposed by the present invention (applied in a multi-phase buck converter);

[0047] Figure 8 for Figure 7 The working waveform diagram of the sawtooth wave generating circuit shown;

[0048] Fig. 9 A single-phase buck converter according to an embodiment of the present invention;

[0049] Fig.10 A single-phase buck converter proposed in another embodiment of the present invention;

[0050] Fig.11 A multi-phase buck converter proposed in one embodiment of the present invention;

[0051] Fig.12 This is a multi-phase buck converter proposed in another embodiment of the present invention. DETAILED DESCRIPTION

[0052] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0053] In a DC-DC buck converter, in order to reduce the ripple of the output voltage and improve the stability and dynamic performance of the buck converter, slope compensation is usually used, that is, a ramp signal related to the output voltage or output current is introduced into the control loop of the buck converter. However, as mentioned in the background art, the sawtooth wave signal in the prior art cannot achieve a compromise between system stability and dynamic response performance when compensating the system in the full range of duty cycle.

[0054] Based on this problem, the present invention proposes a sawtooth wave generating circuit, the sawtooth wave generated by the sawtooth wave generating circuit is applied to a buck converter in COT mode to improve the dynamic response performance on the basis of maintaining the stability of the buck converter, wherein:

[0055] The sawtooth wave generating circuit performs a product operation on the feedback signal and the duty cycle signal to generate a sawtooth wave signal. The slope of the sawtooth wave signal changes with the duty cycle, and the slope of the sawtooth wave signal is in a functional relationship with the duty cycle.

[0056] The feedback signal represents the output voltage or input voltage of the buck converter, and the duty cycle signal represents the duty cycle of the buck converter.

[0057] It can be seen that in the sawtooth wave generating circuit proposed by the present invention, the slope of the sawtooth wave signal changes with the change of the duty cycle, and the slope of the sawtooth wave is in a functional relationship with the duty cycle. Therefore, within the full duty cycle range, the phenomenon of over-compensation of the stability parameter is avoided, thereby ensuring the stability and dynamic response performance of the system within the full duty cycle range.

[0058] Further, a functional relationship is established to characterize the functional relationship between the slope of the sawtooth wave signal and the duty cycle, and the coefficient of the functional relationship is related to the output voltage or input voltage of the buck converter. Specifically, the slope of the sawtooth wave signal and the duty cycle form a linear functional relationship, and the linear term coefficient is related to the output voltage. Alternatively, the slope of the sawtooth wave signal and the duty cycle form a quadratic functional relationship, and the quadratic term coefficient is related to the input voltage.

[0059] The following theoretical analysis explains why the slope of the sawtooth wave signal is a function of the duty cycle to avoid overcompensation of the stability parameters, thereby improving the dynamic response performance while maintaining the stability of the buck converter.

[0060] For a BUCK converter operating in COT mode, the criterion for system stability is:

[0061] Among them, S e Indicates the slope of the sawtooth wave signal, S f Indicates the decreasing slope of the inductor current, T on is the conduction time of the main power tube, C f Represents the output capacitance of the main circuit,

[0062] After conversion, we can get: 2C f *S e / S f =2L f *C f *S e / Vo, T s is the period of the buck converter, L f Indicates the equivalent inductance of the main circuit.

[0063] Therefore, we can finally get:

[0064] It can be seen that the slope of the sawtooth wave signal is controlled to follow the duty cycle, and the slope of the sawtooth wave signal is controlled to form a linear function with the duty cycle, and the coefficient of the linear term of the linear function is related to the output voltage, or the slope of the sawtooth wave signal is controlled to form a quadratic function with the duty cycle, and the coefficient of the quadratic term of the quadratic function is related to the input voltage. Therefore, when the sawtooth wave signal is used to compensate the buck converter, the stability of the system can be compensated within the full range of the duty cycle, and over-compensation of the stability parameter can be avoided. When the sawtooth wave signal generated by the sawtooth wave generating circuit proposed in the present invention is used to compensate the buck converter, within the full duty cycle range, there is no need to adjust the slope value of the added sawtooth wave signal for different duty cycle conditions, and the slope of the sawtooth wave signal will automatically follow the duty cycle.

[0065] It should be noted that there is a relationship of Vo / vin=D between the input voltage, the output voltage and the duty cycle in the buck converter. When the slope of the sawtooth wave signal is in a linear function relationship with the duty cycle, it can be equivalently converted to express that the slope of the sawtooth wave signal is in a quadratic function relationship with the duty cycle. When the buck converter is a multi-phase buck converter, because there is a working condition where the inductor current ripple is approximately zero, the higher the duty cycle corresponding to the working condition where the inductor current ripple is approximately zero, the greater the slope of the sawtooth wave signal required for the system to achieve stability. In this case, according to the stability judgment, it can be concluded that the slope of the sawtooth wave signal is also in a quadratic function relationship with the duty cycle, and the quadratic term coefficient is related to the input voltage. Therefore, using the above sawtooth wave signal for compensation in a multi-phase buck converter can also be used to compensate for the system stability problem encountered by the multi-phase buck converter when the inductor current ripple is approximately zero.

[0066] Specifically, the present invention specifically discloses a sawtooth wave generating circuit, which integrates a signal representing the output voltage according to a duty cycle signal during the conduction period of the main power tube to generate a voltage signal that is in a functional relationship with the duty cycle, and then generates a sawtooth wave signal according to the voltage signal. For example, when the feedback signal represents the output voltage (the feedback signal can be directly obtained from the output end of the buck converter or obtained by filtering the voltage of the node SW), the sawtooth wave generating circuit integrates the output voltage according to the duty cycle signal during the conduction period of the main power tube in the current cycle, and the voltage signal obtained by the integration (the voltage signal represents D*Vo) can be generated by the sawtooth wave generating circuit in the next cycle according to the voltage signal to compensate the buck converter, and the slope of the sawtooth wave signal is in a linear functional relationship with the duty cycle, and the coefficient of the linear term is related to the output voltage. Or for example, when the feedback signal represents the input voltage, the sawtooth wave generating circuit integrates the duty cycle signal and the input voltage in the current cycle to obtain the first voltage or filters the input voltage by simulating the switching behavior of the main power tube to obtain (Vin*D, representing the output voltage), and at the same time integrates the first voltage during the conduction period of the main power tube according to the duty cycle signal to obtain a voltage signal (the voltage signal represents (D 2 *vin), in the next cycle, the sawtooth wave generating circuit can generate a sawtooth wave signal according to the voltage signal to compensate the buck converter. The slope of the sawtooth wave signal is in a quadratic function relationship with the duty cycle, and the quadratic term coefficient is related to the input voltage.

[0067] The process of generating a sawtooth wave signal by performing an integral operation based on the input voltage characterizing signal and the duty cycle signal is more complicated, and the circuit design is more cumbersome. Therefore, preferably, the present invention first performs an integral operation based on the output voltage characterizing signal and the duty cycle signal to generate a sawtooth wave signal, taking the buck converter as a single-phase buck converter as an example, Figure 3 As shown, the sawtooth wave generating circuit includes:

[0068] A first conversion unit, which obtains a current signal according to a feedback signal representing the output voltage, wherein the current signal is proportional to the output voltage;

[0069] The second conversion unit integrates the current signal during the conduction period of the main power tube according to the duty cycle signal in the current cycle to obtain a voltage signal;

[0070] The sampling and holding unit samples and holds the voltage signal when the main power tube ends the conduction, so as to output a holding signal;

[0071] The signal generating unit performs current-voltage conversion according to the holding signal at any time of the next cycle to output a sawtooth wave signal.

[0072] Specifically, Figure 4 As shown, the first conversion unit includes a first transconductance amplifier OTA1, the second conversion unit includes a first capacitor C1 and a first switch M1, the sampling and holding unit includes a third capacitor C3 and a third switch M3, and the signal generating unit includes a second transconductance amplifier OTA2, a second capacitor C2, and a second switch M2. Among them, the first input end of the first transconductance amplifier OTA1 receives the output voltage Vo, the second input end is grounded, the output end of the first transconductance amplifier OTA1 is connected to the positive electrode of the first capacitor C1, the negative electrode of the first capacitor C1 is grounded, the first switch M1 is connected in parallel with the first capacitor C1, the third switch M3 is connected to the positive electrode of the first capacitor C1 and the positive electrode of the third capacitor C3, the first input end of the second transconductance amplifier OTA2 is connected to the positive electrode of the third capacitor C3, the second input end is grounded, the output end is connected to the positive electrode of the second capacitor C2, the negative electrode of the second capacitor C2 is grounded, and the second switch M2 is connected in parallel with the second capacitor C2.

[0073] The working principle of the sawtooth wave generating circuit is as follows: when the buck converter is running, take a cycle, in which the first switch M1 is turned off during the conduction period of the main power tube HS, so the final voltage V1 of the first capacitor C1 = Vo*gm1*T on , gm1 is the transconductance of the first transconductance amplifier OTA1. The third switch M3 is turned on when the main power tube HS is turned on, so the third capacitor C3 samples and holds V1, so the input voltage difference of the second transconductance amplifier OTA2 is V2 = V1 = Vo*gm1*T on In the next cycle, the driving signal of the second switch M2 can drive the second switch M2 to turn on at any time. During the off period of the second switch M2, the voltage of the second capacitor C2 is the sawtooth wave signal V sawtooth , where the sawtooth wave signal V sawtooth The slope of is:

[0074]

[0075] It can be seen that the sawtooth wave signal V sawtooth The slope of the sawtooth signal is proportional to Vo*D or Vin*D. 2 .

[0076] Specifically, when the sawtooth wave generating circuit is applied to a single-phase buck converter and the entire system operates stably, Figure 5 As shown, the driving signal PWM (HS) of the main power tube HS is inverted to obtain the driving signal PWM (M2) of the first switch M1, and the driving signal PWM (HS) of the main power tube HS is reused to drive the second switch M2. Then, the second switch M2 is turned off when the main power tube HS ends conducting. Therefore, the sawtooth wave signal V sawtooth When the main power tube HS is turned on, it starts to generate to compensate the system. It should be noted that in the sawtooth wave signal V sawtooth In the process of generation, the voltage V2 will actually rise and fall, but the voltage difference change is small and can be approximately regarded as V2 remaining stable.

[0077] In another embodiment, when the sawtooth wave generating circuit is applied to an N-phase buck converter (N is a natural number greater than 1), N sawtooth wave generating circuits are correspondingly provided, and the N sawtooth wave generating circuits share one signal generating unit. Figure 6 As shown, the first conversion unit in the N-way sawtooth wave generating circuit obtains the N-th current signal according to the output voltage of the N-phase circuit, and the N-th current signal is proportional to the output voltage of the N-phase circuit; the second conversion unit in the N-way sawtooth wave generating circuit integrates the N-th current signal according to the N-th duty cycle signal during the conduction period of the main power tube in the N-phase circuit to obtain the N-th voltage signal, and the N-th duty cycle signal represents the duty cycle of the N-phase circuit; the sampling and holding unit in the N-way sawtooth wave generating circuit samples and holds the N-th voltage signal when the main power tube in the N-phase circuit is turned on; the signal generating unit performs current-voltage conversion from the first voltage signal to the N-th voltage signal to output a sawtooth wave signal. Preferably, taking a two-phase buck converter as an example, as Figure 7 As shown, the specific circuit structure and working principle of the first conversion unit, the second conversion unit, the sampling and holding unit and the signal generating unit are as follows Figure 4 The sawtooth wave generating circuit shown in FIG. will not be described in detail here. Figure 8 As shown, the driving signal PWM1 of the main power tube HS1 in the first phase circuit is inverted to obtain the driving signal of the first switch M1, and the driving signal PWM2 of the main power tube HS2 in the second phase circuit is inverted to obtain the driving signal of the first switch M1'. At the same time, the falling edge pulses of the driving signals PWM1 and PWM2 are used to control the conduction of the second switch M2. The sawtooth wave signal V sawtoothIt is continuously generated within a period of time and changes to zero when the falling edge pulse of the driving signal PWM1 and PWM2 is generated. It should be noted that Figure 8 The waveform diagram shown only shows that the second switch M2 is driven to turn on by the falling edge pulses of the driving signals PWM1 and PWM2, and the duty cycle represented by the driving signals PWM1 and PWM2 is less than 50%. In other embodiments, the driving signals PWM1 and PWM2 can also be processed by logic to generate a driving signal for controlling the on and off of the second switch M2, thereby controlling the sawtooth wave signal V sawtooth The moment when the slope starts to change.

[0078] After analyzing the sawtooth wave generating circuit used in the above two-phase buck converter, it can be seen that:

[0079]

[0080] It can be seen that the slope of the sawtooth wave signal generated by the sawtooth wave generating circuit in the multi-phase buck converter still follows the duty cycle, and the slope of the sawtooth wave signal is proportional to Vo*D or Vin*D2. Therefore, system stability compensation is achieved in the full range of duty cycle.

[0081] The present invention also provides a control method for a buck converter, comprising the steps of:

[0082] amplifying the error between the output feedback signal and the reference signal to obtain a compensation signal, wherein the output feedback signal represents the output voltage of the buck converter;

[0083] The output feedback signal, the compensation signal and the sawtooth wave signal are processed and compared to output a logic signal. The slope of the sawtooth wave signal changes with the duty cycle, and the slope of the sawtooth wave signal is a function of the duty cycle.

[0084] A driving signal is output according to the logic signal, and the driving signal is used to control the on and off of the power tube in the buck converter.

[0085] Specifically, the sawtooth wave signal and the compensation signal are superimposed and compared with the output feedback signal to output a logic signal. In other embodiments, the sawtooth wave signal and the compensation signal can also be superimposed, and the output feedback signal and the inductor current signal can be superimposed, and then the two superimposed signals can be compared to output a logic signal. When the output capacitor is a ceramic capacitor, its parasitic resistance value is very small. Adding the inductor current signal during the control process can simulate the parasitic resistance value of the output capacitor, thereby improving the stability of the system. In addition, for application scenarios with Load-Line requirements (the output voltage can be adjusted according to the load current), the inductor current signal can be added during the control process to achieve it. In addition, it should be noted that how to amplify the error of the output feedback signal and the reference signal to obtain the compensation signal and how to generate the drive signal according to the logic signal are conventional technical means in this field and will not be elaborated here.

[0086] The slope of the sawtooth wave signal is in a linear function relationship with the duty cycle, and the coefficient of the linear term is related to the output voltage; or, the slope of the sawtooth wave signal is in a quadratic function relationship with the duty cycle, and the coefficient of the quadratic term is related to the input voltage. Specifically, the process of generating the sawtooth wave signal can refer to the sawtooth wave circuit proposed above.

[0087] Furthermore, the buck converter may be a single-phase buck converter or a multi-phase buck converter. As described in the background art, the multi-phase buck converter is provided with a phase distributor compared to the single-phase buck converter. The phase distributor distributes the logic signal to each phase circuit to generate a corresponding drive signal.

[0088] In addition, the present invention further provides a buck converter, the buck converter comprising:

[0089] an operational amplifier circuit, performing error amplification on an output feedback signal and a reference signal to obtain a compensation signal, wherein the output feedback signal represents an output voltage of the buck converter;

[0090] An operation circuit performs operation processing on the output feedback signal, the compensation signal and the sawtooth wave signal and then compares them to output a logic signal, wherein the slope of the sawtooth wave signal changes with the duty cycle, and the slope of the sawtooth wave signal is in a functional relationship with the duty cycle;

[0091] The driving circuit generates a driving signal according to the logic signal, and the driving signal controls the on and off of the power tube in the buck converter.

[0092] Similarly, if Fig. 9 and Fig.11 As shown, the operation circuit in the single-phase buck converter and the multi-phase buck converter compares the sawtooth wave signal and the compensation signal after superposition with the output feedback signal, thereby outputting a logic signal. In other embodiments, such as Fig.10 and Fig.12As shown, the operation circuit in the single-phase buck converter and the multi-phase buck converter can also superimpose the sawtooth wave signal and the compensation signal, superimpose the output feedback signal and the inductor current signal, and then compare the two superimposed signals to output a logic signal. In addition, it should be noted that how to perform error amplification on the output feedback signal and the reference signal to obtain the compensation signal and how to generate the drive signal according to the logic signal are conventional technical means in the art and will not be elaborated here.

[0093] The slope of the sawtooth wave signal is in a linear function relationship with the duty cycle, and the coefficient of the linear term is related to the output voltage; or, the slope of the sawtooth wave signal is in a quadratic function relationship with the duty cycle, and the coefficient of the quadratic term is related to the input voltage. Specifically, the process of generating the sawtooth wave signal can refer to the sawtooth wave circuit proposed above.

[0094] Similarly, the buck converter can be a single-phase buck converter or a multi-phase buck converter. As mentioned in the background technology, the multi-phase buck converter is equipped with a phase distributor compared to the single-phase buck converter. The phase distributor distributes the logic signal to each phase circuit to generate a corresponding drive signal.

[0095] It should be noted that in the two embodiments of the present invention, the slope of the sawtooth wave signal is in a first-order relationship or a second-order relationship with the duty cycle, but this does not mean a limitation on the slope of the sawtooth wave signal. It is only that in the application of the sawtooth wave signal for compensating the stability of the buck converter, the slope of the sawtooth wave signal meeting the above requirements is sufficient to solve the problem. If it is necessary to control the slope of the sawtooth wave signal to be in a third-order, fourth-order or N-order relationship with the duty cycle in other applications, it is reasonable. Only by adding a plurality of first conversion units and second conversion units to the specific circuit proposed by the present invention to realize the multiplication operation, the slope of the sawtooth wave signal can be in an N-order relationship with the duty cycle.

[0096] It should be noted that the specific implementation and corresponding illustrations given are merely a way of describing the implementation method of the present invention, and do not limit the specific structure of the implementation scheme of the present invention. Various changes or modifications can be made to these implementation schemes without departing from the principle and essence of the present invention, but these changes and modifications fall within the scope of protection of the present invention.

[0097] Although the embodiments are described and illustrated separately above, some common technologies are involved. It is the opinion of ordinary technicians in this field that the embodiments can be replaced and integrated. If the content is not clearly recorded in one of the embodiments, reference can be made to another recorded embodiment.

[0098] The above-described implementation methods do not constitute a limitation on the protection scope of the technical solution. Any modification, equivalent replacement and improvement made within the spirit and principle of the above-described implementation methods shall be included in the protection scope of the technical solution.

Claims

1. A sawtooth wave generating circuit, applied to a buck converter, characterized in that: The sawtooth wave generating circuit generates a sawtooth wave signal by performing a product operation on the feedback signal and the duty cycle signal, wherein the slope of the sawtooth wave signal follows the duty cycle of the buck converter, and the slope of the sawtooth wave signal is in a functional relationship with the duty cycle; The feedback signal represents the output voltage or input voltage of the buck converter, and the duty cycle signal represents the duty cycle of the buck converter.

2. The sawtooth wave generating circuit according to claim 1, characterized in that: The coefficients of the functional relationship are related to the output voltage or the input voltage of the buck converter, and the functional relationship represents the functional relationship between the slope of the sawtooth wave signal and the duty cycle.

3. The sawtooth wave generating circuit as claimed in claim 2, characterized in that: The slope of the sawtooth wave signal is in a linear functional relationship with the duty cycle, and the linear term coefficient is related to the output voltage.

4. The sawtooth wave generating circuit as claimed in claim 2, characterized in that: The slope of the sawtooth wave signal is in a quadratic function relationship with the duty cycle, and the quadratic term coefficient is related to the input voltage.

5. The sawtooth wave generating circuit according to any one of claims 1 to 4, characterized in that: The sawtooth wave generating circuit integrates the signal representing the output voltage according to the duty cycle signal during the conduction period of the main power tube to generate a voltage signal that is a function of the duty cycle, and generates the sawtooth wave signal according to the voltage signal.

6. The sawtooth wave generating circuit as claimed in claim 5, characterized in that: The buck converter is an N-phase buck converter, N is a natural number greater than zero, and the sawtooth wave generating circuit includes: N first conversion units, the Nth first conversion unit obtains an Nth current signal according to an Nth feedback signal, the Nth feedback signal represents an output voltage of an Nth phase circuit, and the Nth current signal is proportional to the output voltage of the Nth phase circuit; N second conversion units, the Nth second conversion unit integrating the current signal during the conduction period of the main power tube in the Nth phase circuit according to the Nth duty cycle signal to obtain the Nth voltage signal, wherein the Nth duty cycle signal represents the duty cycle of the Nth phase circuit; The signal generating unit performs current-voltage conversion according to the N voltage signals output by the N second conversion units to output the sawtooth wave signal.

7. The sawtooth wave generating circuit as claimed in claim 6, characterized in that: The sawtooth wave circuit also includes: N sampling and holding units, the Nth sampling and holding unit samples and holds the Nth voltage signal when the main power tube in the Nth phase circuit ends being turned on to output a holding signal, and the signal generating unit outputs the sawtooth wave signal according to the holding signal.

8. The sawtooth wave generating circuit as claimed in claim 6, characterized in that: The first conversion unit includes a first transconductance amplifier, and the second conversion unit includes a first capacitor and a first switch. The first input end of the first transconductance amplifier receives a feedback signal, the second input end of the first transconductance amplifier is grounded, the positive electrode of the first capacitor is connected to the output end of the first transconductance amplifier, the negative electrode of the first capacitor is grounded, and the first switch is connected in parallel with the first capacitor; The first switch is turned off during the conduction period of the main power tube, the output current of the transconductance amplifier is a current signal, and the voltage of the first capacitor is a voltage signal when the main power tube is turned on.

9. The sawtooth wave generating circuit as claimed in claim 8, characterized in that: The signal generating unit includes: a second transconductance amplifier, a second capacitor and a second switch, The first input terminal of the second transconductance amplifier receives the voltage signal, the second input terminal of the second transconductance amplifier is grounded, the positive electrode of the second capacitor is connected to the output terminal of the second transconductance amplifier, the negative electrode of the second capacitor is grounded, and the second switch is connected in parallel with the second capacitor. Wherein, when the second switch is turned off, the voltage of the second capacitor is the sawtooth wave signal.

10. The sawtooth wave generating circuit according to claim 7, characterized in that: The sampling and holding unit includes a third capacitor and a third switch, the third capacitor and the third switch are connected in series, the third switch is turned off when the main power tube is turned on, and the third switch is turned on when the main power tube ends being turned on, and the third capacitor samples and holds the voltage signal.

11. A control method for a buck converter, characterized in that: Includes steps: amplifying an error between an output feedback signal and a reference signal to obtain a compensation signal, wherein the output feedback signal represents an output voltage of the buck converter; The output feedback signal, the compensation signal and the sawtooth wave signal are processed and compared to output a logic signal, wherein the slope of the sawtooth wave signal follows the duty cycle of the buck converter, and the slope of the sawtooth wave signal is in a functional relationship with the duty cycle; A driving signal is output according to the logic signal, and the driving signal controls the on-off of the power tube in the buck converter.

12. The control method according to claim 11, characterized in that: The method further comprises the steps of: performing calculation processing on the output feedback signal, the inductor current signal, the compensation signal and the sawtooth wave signal and then comparing them to obtain the output logic signal.

13. The control method according to claim 11, characterized in that: The sawtooth wave signal is generated by performing a product operation on the feedback signal and the duty cycle signal, and the coefficient of the functional relationship is related to the output voltage or the input voltage of the buck converter. The feedback signal represents the output voltage or input voltage of the buck converter, the duty cycle signal represents the duty cycle of the buck converter, and the functional relationship represents the functional relationship between the slope of the sawtooth wave signal and the duty cycle.

14. The control method according to claim 11 or 13, characterized in that: The slope of the sawtooth wave signal is in a linear functional relationship with the duty cycle, and the linear term coefficient is related to the output voltage.

15. The control method according to claim 11 or 13, characterized in that: The slope of the sawtooth wave signal is in a quadratic function relationship with the duty cycle, and the quadratic term coefficient is related to the input voltage.

16. A buck converter, characterized in that: include: an operational amplifier circuit, amplifying an error between an output feedback signal and a reference signal to obtain a compensation signal, wherein the output feedback signal represents an output voltage of the buck converter; an operation circuit, which performs operation processing on the output feedback signal, the compensation signal, and the sawtooth wave signal and then compares them to obtain an output logic signal, wherein the slope of the sawtooth wave signal follows the duty cycle of the buck converter, and the sawtooth wave signal is in a functional relationship with the duty cycle; The driving circuit generates a driving signal according to the logic signal, and the driving signal controls the on-off of the power tube in the buck converter.

17. The buck converter according to claim 16, wherein: The operation circuit performs operation processing on the output feedback signal, the compensation signal, the sawtooth wave signal, and the inductor current signal, and then compares them to output a logic signal.

18. The buck converter according to claim 16, wherein: The sawtooth wave signal is generated by the sawtooth wave generating circuit described in any one of claims 1-10.

19. The buck converter according to claim 16, wherein: The buck converter includes an N-phase buck converter, where N is a natural number greater than or equal to 1; when N is greater than 1, each phase circuit is correspondingly provided with a drive circuit, and also includes a phase distributor, which distributes the logic signal to the drive circuit of each phase circuit.

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