Fixed-frequency voltage regulation circuit and electronic equipment

Abstract

The invention discloses a fixed-frequency voltage regulation circuit and electronic equipment. The fixed-frequency voltage regulation circuit comprises a voltage regulation module, a signal processing module, a frequency conversion module and a conduction time control module. After a pulse width modulation signal is converted into a frequency feedback voltage through a signal processing module and a frequency conversion module, on one hand, a turn-on time control module can output a turn-on time control signal according to an output voltage, adjust the pulse width modulation signal and further adjust the output voltage, and on the other hand, the turn-on time control module can adjust the output voltage according to the frequency feedback voltage and a reference voltage. And the pulse width modulation signal is adjusted, so that the frequency of the pulse width modulation signal is kept stable, and the switching frequency is prevented from being changed.

Description

Technical Field

[0001] The present application belongs to the technical field of electronic circuits, and in particular relates to a fixed-frequency voltage regulation circuit and electronic equipment. Background Art

[0002] Traditional voltage regulation circuits usually use a DCDC converter architecture with a fixed on-time TON or off-time TOFF. Its switching frequency is variable, and the switching frequency varies by 20% due to changes in input voltage, output voltage, and load current. When the switching frequency is 2MHz, the switching frequency varies by up to 40%. The switching frequency affects the selection of output capacitors and inductors, as well as the design of EMI. Therefore, large changes in the switching frequency will complicate the design of the power supply system. Summary of the invention

[0003] The purpose of the present application is to provide a fixed-frequency voltage regulation circuit and an electronic device, aiming to solve the problem of switching frequency variation of a traditional voltage regulation circuit.

[0004] According to a first aspect of an embodiment of the present application, there is provided a fixed-frequency voltage regulation circuit, comprising: a voltage regulation module, the voltage regulation module being used to generate a pulse width modulation signal, and converting an input voltage into an output voltage according to the pulse width modulation signal; a signal processing module, connected to the voltage regulation module, the signal processing module being used to obtain the pulse width modulation signal, and obtaining a first pulse signal and a second pulse signal based on the pulse width modulation signal; the frequency of the first pulse signal and the frequency of the second pulse signal are both the same as the frequency of the pulse width modulation signal, the rising edge of the second pulse signal is aligned with the rising edge of the pulse width modulation signal, and the rising edge of the first pulse signal is aligned with the falling edge of the second pulse signal; a frequency conversion module, connected to the signal processing module, the frequency conversion module being used to obtain a frequency feedback voltage according to the frequency of the first pulse signal and the frequency of the second pulse signal; an on-time control module, connected to the frequency conversion module and the voltage regulation module, the on-time control module being used to output an on-time control signal according to a ramp signal that periodically returns to zero, the output voltage, the frequency feedback voltage and a reference voltage, the on-time control signal being used to control a high level time and a duty cycle of the pulse width modulation signal.

[0005] In one embodiment, the frequency conversion module includes a frequency conversion unit and a filtering unit; the frequency conversion unit is connected to the signal processing module and the filtering unit, the frequency conversion unit is used to obtain the frequency feedback voltage according to the frequency of the first pulse signal and the frequency of the second pulse signal, and the filtering unit is connected to the on-time control module.

[0006] In one embodiment, the frequency conversion unit includes a first capacitor, a second capacitor, a first conversion switch and a second conversion switch; the first end of the first capacitor is used for current source connection, and the second end of the first capacitor is grounded; the first conduction end of the first conversion switch is connected to the first end of the first capacitor, the second conduction end of the first conversion switch is connected to the second end of the first capacitor, and the control end of the first conversion switch is connected to the signal processing module for receiving the first pulse signal; the first conduction end of the second conversion switch is connected to the first end of the first capacitor, the second conduction end of the second conversion switch is connected to the first end of the second capacitor and the filtering unit, the control end of the second conversion switch is connected to the signal processing module for receiving the second pulse signal, and the second end of the second capacitor is grounded.

[0007] In one embodiment, the filtering unit includes a filtering capacitor and a filtering resistor; the first end of the filtering resistor is connected to the frequency conversion unit, the second end of the filtering resistor is connected to the conduction time control module, the first end of the filtering capacitor is connected to the second end of the filtering resistor, and the second end of the filtering capacitor is grounded.

[0008] In one embodiment, the on-time control module includes: an output sampling unit, a ramp signal output unit, a comparison unit and an on-time control unit; the output sampling unit is used to generate a sampling voltage according to the output voltage, and the sampling voltage is positively correlated with the output voltage; the ramp signal output unit is used to periodically return the ramp signal to zero, and the zeroing period of the ramp signal is equal to the period of the pulse width modulation signal; the comparison unit is connected to the output sampling unit, the ramp signal output unit and the frequency conversion module respectively, and the comparison unit is used to output a first level when the sum of the sampling voltage and the reference voltage is greater than the sum of the ramp signal and the feedback voltage, and output a second level when the sum of the sampling voltage and the reference voltage is greater than or equal to the sum of the ramp signal and the feedback voltage; the on-time control unit is used to output the on-time control signal according to the level output by the comparison unit.

[0009] In one embodiment, the ramp signal output unit is also connected to the signal processing module, and the signal processing module is also used to output a third pulse signal, and the frequency of the third pulse signal is equal to the frequency of the pulse width modulation signal; the ramp signal output unit is used to generate the ramp signal based on the input voltage according to the third pulse signal and the level output by the comparison unit.

[0010] In one embodiment, the ramp signal output unit includes a voltage-dividing resistor, a third capacitor, a third conversion switch and a fourth conversion switch; the first conduction end of the third conversion switch is used to receive the input voltage through the voltage-dividing resistor, the second conduction end of the third conversion switch is connected to the first end of the third capacitor, and the control end of the third conversion switch is connected to the on-time control unit for receiving the on-time control signal; the second end of the third capacitor is grounded; the first conduction end of the fourth conversion switch is connected to the first end of the third capacitor, the second conduction end of the fourth conversion switch is connected to the second end of the third capacitor, and the control end of the fourth conversion switch is connected to the signal processing module for receiving the third pulse signal.

[0011] In one embodiment, the fourth switch is configured to be turned on when receiving a pulse of the third pulse signal.

[0012] In one embodiment, the voltage regulating module is configured to adjust the on-time of the voltage regulating module according to the on-time control signal.

[0013] A second aspect of an embodiment of the present application provides an electronic device, comprising the above-mentioned fixed-frequency voltage regulation circuit.

[0014] Compared with the prior art, the embodiments of the present application have the following beneficial effects: after the pulse width modulation signal is converted into a frequency feedback voltage through the signal processing module and the frequency conversion module, on the one hand, the on-time control module can output an on-time control signal according to the output voltage, adjust the pulse width modulation signal, and then adjust the output voltage. At the same time, the pulse width modulation signal can also be adjusted according to the frequency feedback voltage and the reference voltage to keep the frequency of the pulse width modulation signal stable, thereby avoiding changes in the switching frequency. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic diagram of the principle of a constant frequency voltage regulation circuit provided in one embodiment of the present application;

[0016] Figure 2 A circuit diagram of a frequency conversion module provided in one embodiment of the present application;

[0017] Figure 3 A schematic diagram of a signal waveform provided in an embodiment of the present application;

[0018] Figure 4 A circuit diagram of a conduction time control module provided in an embodiment of the present application. DETAILED DESCRIPTION

[0019] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0020] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0021] It should be understood that the orientation or position relationship indicated by terms such as "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0022] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0023] Figure 1 The following is a structural diagram of a fixed-frequency voltage regulation circuit and an electronic device provided in an embodiment of the present application. For ease of explanation, only the parts related to the present embodiment are shown, which are described in detail as follows:

[0024] The fixed-frequency voltage regulation circuit includes: a voltage regulation module 100 , a signal processing module 200 , a frequency conversion module 300 and a conduction time control module 400 .

[0025] Among them, the voltage regulating module 100 is used to generate a pulse width modulation signal, and convert the input voltage into an output voltage according to the pulse width modulation signal. The signal processing module 200 is connected to the voltage regulating module 100, and the signal processing module 200 is used to obtain the pulse width modulation signal, and obtain the first pulse signal and the second pulse signal based on the pulse width modulation signal. The frequency of the first pulse signal and the frequency of the second pulse signal are the same as the frequency of the pulse width modulation signal, the rising edge of the second pulse signal is aligned with the rising edge of the pulse width modulation signal, and the rising edge of the first pulse signal is aligned with the falling edge of the second pulse signal. The frequency conversion module 300 is connected to the signal processing module 200, and the frequency conversion module 300 is used to obtain a frequency feedback voltage according to the frequency of the first pulse signal and the frequency of the second pulse signal. The on-time control module 400 is connected to the frequency conversion module 300 and the voltage regulating module 100, and the on-time control module 400 is used to output an on-time control signal according to the ramp signal that periodically returns to zero, the output voltage, the frequency feedback voltage and the reference voltage, and the on-time control signal is used to control the high level time and duty cycle of the pulse width modulation signal.

[0026] After the pulse width modulation signal is converted into a frequency feedback voltage through the signal processing module 200 and the frequency conversion module 300, on the one hand, the on-time control module 400 can output an on-time control signal according to the output voltage, adjust the pulse width modulation signal, and then realize feedback adjustment of the output voltage. At the same time, the pulse width modulation signal can also be adjusted according to the frequency feedback voltage and the reference voltage to keep the frequency of the pulse width modulation signal stable, thereby avoiding changes in the switching frequency of the voltage regulation module 100.

[0027] It should be noted that the voltage regulation module 100 generally includes a control unit and a driving unit, the control unit is used to generate a pulse width modulation signal through pulse width modulation (PWM), and the driving unit controls the switching frequency of the switching device in the driving unit according to the received pulse width modulation signal, thereby generating a corresponding output voltage based on the input voltage. Exemplarily, the driving unit may include a DC chopper circuit for DC / DC voltage regulation.

[0028] In one embodiment, if Figure 2 As shown, the frequency conversion module 300 includes a frequency conversion unit 310 and a filtering unit 320. The frequency conversion unit 310 is connected to the signal processing module 200 and the filtering unit 320, and the frequency conversion unit 310 is used to obtain a frequency feedback voltage according to the frequency of the first pulse signal and the frequency of the second pulse signal, and the filtering unit 320 is connected to the conduction time control module 400.

[0029] The filtering unit 320 is used to filter the frequency feedback voltage, so as to make the frequency feedback voltage more stable.

[0030] In one embodiment, if Figure 2 As shown, the frequency conversion unit 310 includes a first capacitor C1, a second capacitor C2, a first conversion switch S1 and a second conversion switch S2. The first end of the first capacitor C1 is used for current source connection, and the second end of the first capacitor C1 is grounded. The first conduction end of the first conversion switch S1 is connected to the first end of the first capacitor C1, the second conduction end of the first conversion switch S1 is connected to the second end of the first capacitor C1, and the control end of the first conversion switch S1 is connected to the signal processing module 200 for receiving the first pulse signal. The first conduction end of the second conversion switch S2 is connected to the first end of the first capacitor C1, the second conduction end of the second conversion switch S2 is connected to the first end of the second capacitor C2 and the filtering unit 320, the control end of the second conversion switch S2 is connected to the signal processing module 200 for receiving the second pulse signal, and the second end of the second capacitor C2 is grounded.

[0031] Whenever the first pulse signal provides a high level pulse to the first conversion switch S1, the first conversion switch S1 is turned on, and both ends of the first capacitor C1 are grounded at the same time, thereby releasing the charge on the first capacitor C1 and returning the voltage on the first capacitor C1 to zero.

[0032] After that, the first conversion switch S1 is turned off, the current source can continue to charge the first capacitor C1, and the voltage on the first capacitor C1 continues to rise. When the second pulse signal provides a high-level pulse to the second conversion switch S2, the second conversion switch S2 is turned on, so that the second capacitor C2 can obtain electrical energy from the first capacitor C1, thereby sampling the voltage on the first capacitor C1.

[0033] For example, the waveform of each signal is as follows: Figure 3 As shown, it can be understood that the longer the interval from the first conversion switch S1 being turned off to the first conversion switch S1 being turned on, the higher the charging voltage V on the first capacitor C1 is. chg The larger the voltage on the second capacitor C2. Since the frequency of the pulse width modulation signal PWM and the frequency of the second pulse signal Tsample are the same as the frequency of the pulse width modulation signal PWM, the smaller the frequency of the pulse width modulation signal PWM, the longer the interval from the first conversion switch S1 being turned off to the first conversion switch S1 being turned on, and the charging voltage V on the first capacitor C1 is chg The larger the voltage on the second capacitor C2, the higher the final output frequency feedback voltage V FSW The larger the frequency of the pulse width modulation signal PWM is, the shorter the interval from the first conversion switch S1 being turned off to the first conversion switch S1 being turned on is, and the charging voltage V on the first capacitor C1 is chg The smaller the voltage on the second capacitor C2, the higher the frequency feedback voltage V FSW The smaller.

[0034] Finally, the frequency of the pulse width modulation signal PWM can be obtained through the frequency feedback voltage VFSW.

[0035] In one embodiment, if Figure 2 As shown, the filter unit 320 includes a filter capacitor C3 and a filter resistor R1. The first end of the filter resistor R1 is connected to the frequency conversion unit 310, the second end of the filter resistor R1 is connected to the conduction time control module 400, the first end of the filter capacitor C3 is connected to the second end of the filter resistor R1, and the second end of the filter capacitor C3 is grounded.

[0036] The filtering unit 320 can be used to perform low-pass filtering on the frequency feedback voltage, so as to make the frequency feedback voltage more stable.

[0037] In one embodiment, if Figure 4 As shown, the on-time control module 400 includes: an output sampling unit, a ramp signal output unit 410, a comparison unit 420 and an on-time control unit 430. The output sampling unit is used to generate a sampling voltage according to the output voltage, and the sampling voltage is positively correlated with the output voltage. The ramp signal output unit 410 is used for a ramp signal that periodically returns to zero, and the zero return period of the ramp signal is equal to the period of the pulse width modulation signal. The comparison unit 420 is connected to the output sampling unit, the ramp signal output unit 410 and the frequency conversion module 300 respectively, and the comparison unit 420 is used to output a first level when the sum of the sampling voltage and the reference voltage is greater than the sum of the ramp signal and the feedback voltage, and output a second level when the sum of the sampling voltage and the reference voltage is greater than or equal to the sum of the ramp signal and the feedback voltage. The on-time control unit 430 is used to output an on-time control signal according to the level output by the comparison unit 420.

[0038] Specifically, the comparison unit 420 may include an operational comparator U1. The output sampling unit may obtain a sampled voltage based on the output voltage by a certain ratio. Exemplarily, the calculation formula of the sampled voltage is:

[0039] Vth=K 1 *VOUT (1)

[0040] In the formula, Vth is the sampling voltage, VOUT is the output voltage, K 1 is the first coefficient. K 1 Greater than 0 and less than 1.

[0041] When the frequency feedback voltage is equal to the reference voltage, it can be regarded that the frequency of the current pulse width modulation signal meets the set frequency, and the on-time control unit 430 can output the corresponding on-time control signal according to the sampling voltage and the ramp signal. In a zeroing cycle of the ramp signal, the comparison unit 420 will first output the first level, and when the voltage of the ramp signal continues to rise and the sum of the ramp signal and the feedback voltage is not less than the sum of the sampling voltage and the reference voltage, before the ramp signal returns to zero again, the comparison unit 420 will continue to output the second level.

[0042] Exemplarily, when the level output by the comparison unit 420 changes from the first level to the second level, the on-time control unit 430 may output a pulse signal, and finally the multiple pulse signals output by the on-time control unit 430 are the on-time control signal. It can be understood that the voltage regulating module 100 may determine the falling edge of the pulse width modulation signal according to each pulse in the on-time control signal, and when the rising edge of the pulse width modulation signal remains unchanged, the length of the on-time of the voltage regulating module 100 is determined.

[0043] When the frequency of the pulse width modulation signal is greater than the set frequency, the frequency feedback voltage is less than the reference voltage, and the voltage difference obtained by subtracting the frequency feedback voltage from the reference voltage is a positive value. Therefore, the ramp signal needs a longer time to rise to a higher voltage so that the ramp signal can be equal to the sum of the sampling voltage and the voltage difference. Therefore, when the output voltage is the same, compared with the frequency feedback voltage being equal to the reference voltage, when the frequency of the pulse width modulation signal is greater than the set frequency, the width of the first level becomes wider, the width of the high level of the pulse width modulation signal generated based on the on-time control signal becomes wider, and the on-time of the voltage regulating module 100 becomes longer, thereby reducing the frequency of the pulse width modulation signal until the frequency of the pulse width modulation signal is equal to the set frequency.

[0044] When the frequency of the pulse width modulation signal is less than the set frequency, the frequency feedback voltage is greater than the reference voltage, and the voltage difference obtained by subtracting the frequency feedback voltage from the reference voltage is a negative value. Therefore, the ramp signal needs a shorter time, and the ramp signal can be equal to the sum of the sampling voltage and the voltage difference. Therefore, when the output voltage is the same, compared with the frequency feedback voltage being equal to the reference voltage, when the frequency of the pulse width modulation signal is less than the set frequency, the width of the first level becomes narrower, the width of the high level of the pulse width modulation signal generated based on the on-time control signal becomes narrower, and the on-time of the voltage regulating module 100 becomes shorter, thereby increasing the frequency of the pulse width modulation signal until the frequency of the pulse width modulation signal is equal to the set frequency.

[0045] In one embodiment, the ramp signal output unit 410 is also connected to the signal processing module 200, and the signal processing module 200 is also used to output a third pulse signal, and the frequency of the third pulse signal is equal to the frequency of the pulse width modulation signal. The ramp signal output unit 410 is used to generate a ramp signal based on the input voltage according to the third pulse signal and the level output by the comparison unit 420.

[0046] It should be noted that the third pulse signal can be used to control the zero return period of the ramp signal so that the zero return period of the ramp signal is equal to the period of the pulse width modulation signal. The ramp signal output unit 410 can return the voltage of the ramp signal to zero each time a pulse provided by the third pulse signal is received. The ramp signal output unit 410 can also output a ramp signal with a continuously rising voltage when the comparison unit 420 outputs a first level, and keep the voltage of the ramp signal unchanged when the comparison unit 420 outputs a second level.

[0047] In one embodiment, the ramp signal output unit 410 includes a voltage-dividing resistor R2, a third capacitor C4, a third conversion switch S3, and a fourth conversion switch S4. The first conduction end of the third conversion switch S3 is used to receive the input voltage through the voltage-dividing resistor R2, the second conduction end of the third conversion switch S3 is connected to the first end of the third capacitor C4, and the control end of the third conversion switch S3 is connected to the on-time control unit 430 for receiving the on-time control signal. The second end of the third capacitor C4 is grounded. The first conduction end of the fourth conversion switch S4 is connected to the first end of the third capacitor C4, the second conduction end of the fourth conversion switch S4 is connected to the second end of the third capacitor C4, and the control end of the fourth conversion switch S4 is connected to the signal processing module 200 for receiving the third pulse signal.

[0048] It can be understood that by controlling the on and off of the fourth conversion switch S4 through the third pulse signal, the zero return period of the ramp signal can be controlled, and each time the fourth conversion switch S4 is turned on, the ramp signal returns to zero. In the case where the sum of the ramp signal and the frequency feedback voltage is equal to the sum of the sampling voltage and the reference voltage, by turning off the third conversion switch S3, the voltage of the ramp signal can no longer rise until it returns to zero due to the turning on of the fourth conversion switch S4.

[0049] In one embodiment, the fourth switch S4 is configured to be turned on when receiving a pulse of the third pulse signal.

[0050] Specifically, the fourth conversion switch S4 is configured to be turned on when the level of the control terminal of the fourth conversion switch S4 is at a high level.

[0051] In one embodiment, the slope of the ramp signal is positively correlated with the input voltage of the on-time control signal.

[0052] It can be understood that, the greater the input voltage is, the greater the charging voltage of the third capacitor C4 is, and thus the greater the slope of the ramp signal is.

[0053] An embodiment of the present application provides an electronic device, including a fixed frequency voltage regulating circuit as in any of the above embodiments. Since the electronic device includes all technical features of the fixed frequency voltage regulating circuit, the electronic device has all the beneficial effects of the fixed frequency voltage regulating circuit, which will not be described in detail in this embodiment.

[0054] The technicians in the relevant field can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In practical applications, the above-mentioned function allocation can be completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated in a processing unit, or each unit can exist physically separately, or two or more units can be integrated in one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, which will not be repeated here.

[0055] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0056] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A fixed frequency voltage regulation circuit, characterized in that: include: A voltage regulating module, the voltage regulating module is used to generate a pulse width modulation signal and convert an input voltage into an output voltage according to the pulse width modulation signal; A signal processing module connected to the voltage regulating module, the signal processing module is used to obtain the pulse width modulation signal, and obtain a first pulse signal and a second pulse signal based on the pulse width modulation signal; The frequencies of the first pulse signal and the second pulse signal are both the same as the frequency of the pulse width modulation signal, the rising edge of the second pulse signal is aligned with the rising edge of the pulse width modulation signal, and the rising edge of the first pulse signal is aligned with the falling edge of the second pulse signal; A frequency conversion module, connected to the signal processing module, and configured to obtain a frequency feedback voltage according to the frequency of the first pulse signal and the frequency of the second pulse signal; A conduction time control module is connected to the frequency conversion module and the voltage regulation module. The conduction time control module is used to output a conduction time control signal according to the periodically zeroed ramp signal, the output voltage, the frequency feedback voltage and the reference voltage. The conduction time control signal is used to control the high level time and duty cycle of the pulse width modulation signal.

2. The constant frequency voltage regulation circuit according to claim 1, characterized in that: The frequency conversion module includes a frequency conversion unit and a filtering unit; The frequency conversion unit is connected to the signal processing module and the filtering unit. The frequency conversion unit is used to obtain the frequency feedback voltage according to the frequency of the first pulse signal and the frequency of the second pulse signal. The filtering unit is connected to the conduction time control module.

3. The constant frequency voltage regulation circuit according to claim 2, characterized in that: The frequency conversion unit includes a first capacitor, a second capacitor, a first conversion switch and a second conversion switch; The first end of the first capacitor is used for connecting to a current source, and the second end of the first capacitor is grounded; The first conducting end of the first conversion switch is connected to the first end of the first capacitor, the second conducting end of the first conversion switch is connected to the second end of the first capacitor, and the control end of the first conversion switch is connected to the signal processing module for receiving the first pulse signal; The first conduction end of the second conversion switch is connected to the first end of the first capacitor, the second conduction end of the second conversion switch is connected to the first end of the second capacitor and the filtering unit, the control end of the second conversion switch is connected to the signal processing module for receiving the second pulse signal, and the second end of the second capacitor is grounded.

4. The constant frequency voltage regulation circuit according to claim 3, characterized in that: The filtering unit includes a filtering capacitor and a filtering resistor; The first end of the filter resistor is connected to the frequency conversion unit, the second end of the filter resistor is connected to the conduction time control module, the first end of the filter capacitor is connected to the second end of the filter resistor, and the second end of the filter capacitor is grounded.

5. The fixed frequency voltage regulating circuit according to any one of claims 1 to 4, characterized in that: The on-time control module comprises: an output sampling unit, a ramp signal output unit, a comparison unit and an on-time control unit; The output sampling unit is used to generate a sampling voltage according to the output voltage, and the sampling voltage is positively correlated with the output voltage; The ramp signal output unit is used for the ramp signal that periodically returns to zero, and the zero-returning period of the ramp signal is equal to the period of the pulse width modulation signal; The comparison unit is connected to the output sampling unit, the ramp signal output unit and the frequency conversion module respectively, and the comparison unit is used to output a first level when the sum of the sampling voltage and the reference voltage is greater than the sum of the ramp signal and the feedback voltage, and output a second level when the sum of the sampling voltage and the reference voltage is greater than or equal to the sum of the ramp signal and the feedback voltage; The on-time control unit is used to output the on-time control signal according to the level output by the comparison unit.

6. The constant frequency voltage regulation circuit according to claim 5, characterized in that: The ramp signal output unit is also connected to the signal processing module, and the signal processing module is also used to output a third pulse signal, and the frequency of the third pulse signal is equal to the frequency of the pulse width modulation signal; The ramp signal output unit is used to generate the ramp signal based on the input voltage according to the third pulse signal and the level output by the comparison unit.

7. The constant frequency voltage regulation circuit according to claim 6, characterized in that: The ramp signal output unit includes a voltage dividing resistor, a third capacitor, a third conversion switch and a fourth conversion switch; The first conduction end of the third conversion switch is used to receive the input voltage through the voltage-dividing resistor, the second conduction end of the third conversion switch is connected to the first end of the third capacitor, and the control end of the third conversion switch is connected to the on-time control unit to receive the on-time control signal; The second end of the third capacitor is grounded; The first conduction end of the fourth conversion switch is connected to the first end of the third capacitor, the second conduction end of the fourth conversion switch is connected to the second end of the third capacitor, and the control end of the fourth conversion switch is connected to the signal processing module for receiving the third pulse signal.

8. The constant frequency voltage regulation circuit according to claim 7, characterized in that: The fourth conversion switch is configured to be turned on upon receiving a pulse of the third pulse signal.

9. The constant frequency voltage regulation circuit according to claim 5, characterized in that: The voltage regulating module is configured to adjust the on-time of the voltage regulating module according to the on-time control signal.

10. An electronic device, characterized in that: It comprises the fixed frequency voltage regulating circuit as claimed in any one of claims 1 to 9.

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