A boost converter and a control circuit and method thereof

Abstract

The application provides a boost converter, a control circuit and a method thereof, an input feedforward signal is generated based on an input voltage, a first difference signal is obtained by subtracting the difference between an error amplification signal and a ramp signal from the input feedforward signal, and a comparison signal is obtained by comparing the first difference signal with an inductor current sampling signal in a conduction stage of a main switch tube; or, a first sum signal is obtained by superimposing the inductor current sampling signal in the conduction stage of the main switch tube and the input feedforward signal, and the comparison signal is obtained by comparing the difference between the error amplification signal and the ramp signal with the first sum signal; and the main switch tube is controlled to be turned off when the comparison signal flips. When the input voltage changes, the input feedforward signal is introduced, the size of the inductor current is controlled by controlling the peak value of the inductor current, and the ripple of the output voltage is optimized, so that the stability of the system is improved.

Description

Technical Field

[0001] This invention relates to the field of power converters, and more specifically to a boost converter and its control circuit and method. Background Technology

[0002] For boost converters, it is necessary to minimize output voltage ripple to avoid affecting system stability and the performance of power supply equipment. When the input voltage changes abruptly, ripple is generated on the output voltage. Figure 1 The diagram illustrates the control method for a voltage-mode controlled buck converter. It utilizes a ramp signal Vramp and an error amplification signal Vcomp to control the duty cycle. The slope of the ramp signal Vramp is proportional to the input voltage Vin, thus the duty cycle Dpwm = Vcomp / (K*Vin) is obtained. Since the duty cycle is inversely proportional to the input voltage Vin, when the input voltage Vin changes rapidly, such as rapidly increasing, the duty cycle decreases accordingly, allowing Vcomp to remain constant and thus improving the output voltage ripple caused by input voltage changes. However, this method is not suitable for boost converters or current-mode control. Figure 2 The diagram shows a schematic of a fixed-frequency peak current controlled boost converter in the prior art. As can be seen from the diagram, its control circuit achieves peak control by comparing the difference between the error amplification signal Vc0 and the ramp signal Vramp with the inductor current sampling signal Visns. When the input voltage Vin increases, Figure 3 To correspond to its operating waveform diagram, before time t3, the input voltage Vin remains constant, and the boost converter operates normally. At time t3, the input voltage Vin increases. Ignoring the effect of converter efficiency, the input power of the converter equals the output power, i.e., Vin * Iin = Vout * Iout. Therefore, with the output current Iout remaining constant, to maintain the stability of the output voltage Vout, the input current Iin should decrease when the input voltage Vin increases. However, after the input voltage Vin increases, during the turn-on period of the main switch Q1, the inductor current rises at a faster rate, and during the turn-on period of the switch Q2, the inductor current falls at a slower rate. Consequently, when the input voltage Vin increases, the inductor current actually increases. Figure 3 As can be seen from the data, after the input voltage Vin increases at time t3, the inductor current sampling signal Visns increases, causing the output voltage to rise rapidly. Figure 2 As can be seen from the schematic diagram, after the output voltage Vout increases, the error amplification signal Vc0 decreases, thereby reducing the inductor current and eventually allowing the output voltage Vout to return to a steady state. However, during this process, the output voltage ripple is relatively large. Therefore, it is necessary to propose a new control scheme to solve the problems existing in the current technology. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a boost converter and its control circuit and method.

[0004] According to a first aspect of the present invention, a boost converter control circuit is provided, the boost converter being used to convert an input voltage into an output voltage, characterized in that the control circuit comprises:

[0005] An error amplification module, which generates an error amplification signal based on the output voltage feedback signal and the reference voltage signal;

[0006] A ramp signal generation module is provided, which is used to generate a ramp signal when the main switch of the boost converter is turned on; when the main switch is turned on, the inductor current of the boost converter increases.

[0007] An input voltage feedforward circuit generates an input feedforward signal based on the input voltage.

[0008] The first comparator takes the difference between the amplified error signal and the ramp signal, and then subtracts it from the input feedforward signal to obtain the signal at the first input terminal of the first comparator. The second input terminal of the first comparator receives the inductor current sampling signal during the conduction phase of the main switch. Alternatively...

[0009] The difference between the error amplification signal and the ramp signal is used as the signal at the first input terminal of the first comparator. The inductor current sampling signal during the conduction phase of the main switch is superimposed with the input feedforward signal as the signal at the second input terminal of the first comparator. When the comparator output flips, the main switch is controlled to turn off.

[0010] Optionally, the input voltage feedforward circuit is any one of a high-pass filter circuit, a low-pass filter circuit, or a band-pass filter circuit, which receives the input voltage and generates the input feedforward signal based on the change of the input voltage.

[0011] Optionally, the larger the average inductance of the step-up transformer, the larger the input feedforward signal.

[0012] Optionally, when the input voltage feedforward path is a high-pass filter circuit, the input voltage feedforward includes a first capacitor, a first resistor, and a second resistor connected in series between the input voltage and the ground terminal, and the input feedforward signal is generated at the common node of the first resistor and the second resistor.

[0013] Optionally, the second resistor is composed of multiple sub-resistors. Based on the magnitude of the average current of the step-up transformer inductor, the multiple sub-resistors are configured with different connection methods so that when the average current of the step-up transformer inductor is greater than a number of progressively increasing threshold values, the resistance value of the second resistor increases accordingly.

[0014] Optionally, the control circuit further includes a logic control and drive signal generation module, which generates a signal to control the corresponding switch in the boost converter to turn on or off based on the output signal and clock signal of the first comparator; and controls the switching cycle of the boost converter based on the clock signal.

[0015] Optionally, the ramp signal generating circuit includes a second capacitor. During the main switch transistor's on-phase, a first current source acts on the second capacitor to generate the ramp signal; after the main switch transistor is turned off, the second capacitor discharges.

[0016] Optionally, the control circuit further includes a compensation module, which is disposed at the output terminal of the error amplifier circuit.

[0017] The present invention also provides a control method for a boost converter, characterized in that the boost converter is used to convert an input voltage into an output voltage, and characterized in that the control method includes:

[0018] An error amplification signal is generated based on the output voltage feedback signal and the reference voltage signal;

[0019] A ramp signal is generated when the main switch of the boost converter is turned on; when the main switch is turned on, the inductor current of the boost converter rises.

[0020] An input feedforward signal is generated based on the input voltage;

[0021] The difference between the amplified error signal and the ramp signal is then subtracted from the input feedforward signal to obtain a first difference signal. This first difference signal is then compared with the inductor current sampling signal during the main switch's conduction phase to obtain a comparison signal; or...

[0022] The inductor current sampling signal during the conduction phase of the main switch is superimposed with the input feedforward signal to obtain a first sum signal. The difference between the error amplification signal and the ramp signal is compared with the first sum signal to obtain a comparison signal. When the comparison signal flips, the main switch is controlled to turn off.

[0023] Optionally, the input voltage is filtered by any one of high-pass filtering, low-pass filtering, or band-pass filtering to generate the input feedforward signal.

[0024] Optionally, the larger the average inductance of the step-up transformer, the larger the input feedforward signal.

[0025] The present invention also provides a boost converter for converting input voltage into output voltage. The boost converter includes the control circuit described above, or controls the main switching transistor in the boost converter based on the control method described above.

[0026] The beneficial effects of the present invention include at least the following:

[0027] The boost converter and its control circuit and method provided by this invention generate an input feedforward signal based on the input voltage. The difference between the error amplification signal and the ramp signal is then subtracted from the input feedforward signal to obtain a first difference signal. This first difference signal is compared with the inductor current sampling signal during the main switch's conduction phase to obtain a comparison signal. Alternatively, the inductor current sampling signal during the main switch's conduction phase is superimposed with the input feedforward signal to obtain a first sum signal. The difference between the error amplification signal and the ramp signal is then compared with the first sum signal to obtain the comparison signal. When the comparison signal flips, the main switch is turned off. When the input voltage changes, this invention introduces an input feedforward signal, which allows control of the inductor current's magnitude by controlling the peak value of the inductor current, thereby optimizing the output voltage ripple and improving system stability.

[0028] Furthermore, the input voltage is filtered by any of the high-pass, low-pass, or band-pass filters to generate an input feedforward signal. Moreover, the amount of the input feedforward signal can be adjusted based on the magnitude of the average current of the step-up transformer inductor, so that the larger the average current of the step-up transformer inductor, the larger the amount of the input feedforward signal, thereby further optimizing the output voltage ripple under different load conditions.

[0029] It should be noted that the above general description and the following detailed description are exemplary and explanatory only, and do not limit the present invention. Attached Figure Description

[0030] Figure 1 This diagram shows a working waveform of a voltage-controlled buck converter in the prior art;

[0031] Figure 2 This diagram illustrates a schematic of a fixed-frequency peak current controlled boost converter in the prior art.

[0032] Figure 3 It shows Figure 2 The corresponding signal's working waveform diagram;

[0033] Figure 4 A schematic diagram of a boost converter control circuit provided by the present invention is shown.

[0034] Figure 5 An embodiment of the input voltage feedforward circuit provided by the present invention is shown;

[0035] Figure 6 An embodiment of the ramp signal generation module provided by the present invention is shown;

[0036] Figure 7 It shows Figure 4 The corresponding signal's working waveform diagram;

[0037] Figure 8 Another embodiment of the input voltage feedforward circuit provided by the present invention is shown;

[0038] Figure 9 Another schematic diagram of the boost converter control circuit provided by the present invention is shown. Detailed Implementation

[0039] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in various forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0040] The main topology of the boost converter in this paper adopts... Figure 2 The structure includes a main switch Q1, an inductor L, and a switch Q2. The inductor L and the switch Q2 are connected in series between the input voltage Vin and the output voltage Vout. The main switch Q1 is connected between the common node of the inductor L and the switch Q2 and the ground terminal. An output capacitor Co is provided at the output terminal. The input voltage Vin is converted into the corresponding output voltage Vout by controlling the conduction or cutoff of the main switch Q1 and the switch Q2 through the control circuit. Figure 4 The diagram shown is a schematic of a boost converter control circuit provided by the present invention. This control circuit includes an error amplification module EA and a ramp signal generation module. The error amplification module EA generates an error amplification signal Vc0 based on the output voltage feedback signal Vfb and the reference voltage signal Vref. The ramp signal generation module generates a ramp signal Vramp during the conduction of the main switch Q1 of the boost converter. When the main switch Q1 is turned on, the inductor current of the boost converter rises. The control circuit also includes an input voltage feedforward circuit and a first comparator CMP1. The input voltage feedforward circuit generates an input feedforward signal Vff based on the input voltage Vin. Wherein, as... Figure 4As shown, the difference between the error amplification signal Vc0 and the ramp signal Vramp is then subtracted from the input feedforward signal Vff, and this difference is used as the signal at the first input terminal of the first comparator CMP1. The second input terminal of the first comparator CMP1 receives the inductor current sampling signal Visns during the main switch's on-state phase. The first comparator CMP1 outputs a comparison signal CP. When the comparison signal CP flips, it indicates that the inductor current has risen to its peak value, controlling the main switch Q1 to turn off. The inductor current sampling can be implemented using existing circuitry. The control circuit also includes a logic control and drive signal generation module, which generates drive signals Q1D and Q2D, respectively, to control the on / off states of switches Q1 and Q2 in the boost converter, based on the output signal CP of the first comparator CMP1 and the clock signal CLK. The switching cycle of the boost converter is controlled based on the clock signal CLK. The clock signal CLK generation module can be implemented using existing structures.

[0041] As some embodiments of the present invention, the input voltage feedforward circuit is any one of a high-pass filter circuit, a low-pass filter circuit, or a band-pass filter circuit. It receives the input voltage Vin and generates an input feedforward signal Vff based on changes in the input voltage Vin. When a low-pass filter circuit is used as the input voltage feedforward circuit, the circuit design complexity is relatively high due to the introduction of a corresponding DC voltage; therefore, a high-pass filter circuit is preferred. The following description uses a high-pass filter circuit as an example. Figure 5 The diagram illustrates one embodiment of an input voltage feedforward circuit, including a first capacitor C1, a first resistor R1, and a second resistor R2 connected in series between the input voltage Vin and ground. An input feedforward signal Vff is generated at the common node of the first resistor R1 and the second resistor R2. Here, the first resistor R1 and the second resistor R2 are used to divide the input voltage Vin to generate Vff. The values ​​of the first resistor R1 and the second resistor R2 can be set as needed. Of course, in other embodiments, the first resistor R1 may be omitted.

[0042] Figure 6 The diagram illustrates one embodiment of the ramp signal generation module described in this paper. It includes a second capacitor C2 and a switch S1. Switch S1 is controlled by a drive signal Q2D (in other embodiments, it may also be controlled by Q1D). During the rising phase of the boost converter inductor current, i.e., when the main switch Q1 is on, the drive signal Q2D is invalid, switch S1 is open, and the first current source I1 acts on the second capacitor C2 to generate the ramp signal Vramp. After the rising phase of the inductor current ends, i.e., after the main switch Q1 is turned off, the drive signal Q2D becomes valid, switch S1 closes, and the second capacitor C2 discharges. Figure 6 This is just one example of a ramp signal generation module; other modules can also be used to achieve the same function.

[0043] To further understand this invention, the following description is provided in conjunction with the working waveform diagram. Figure 7 As shown Figure 4 The waveform diagram of the corresponding signal is shown. At time t1, the clock signal CLK is generated. The logic control and drive signal generation module generates a valid drive signal Q1D and an invalid drive signal Q2D based on the clock signal CLK. Here, a high level indicates that the drive signal is valid. The main switch Q1 is turned on, and the inductor current sampling signal Visns begins to increase. The ramp signal generation circuit generates a ramp signal Vramp based on the drive signal Q2D (other embodiments can also be based on Q1D). Since the input voltage Vin is stable, the input feedforward signal Vff is zero. At this time, the first input terminal of the first comparator CMP1 is... The signal (first difference signal Vc1) is equal to the difference between the error amplification signal Vc0 and the ramp signal Vramp. At time t2, when the inductor current sampling signal Visns rises to the first difference signal Vc1, the comparison signal CP output by the first comparator CMP1 flips. The logic control and drive signal generation module generates an invalid drive signal Q1D and an effective drive signal Q2D based on the comparison signal CP. The main switch Q1 is turned off, the switch Q2 is turned on, the ramp signal Vramp is reset, and the inductor current decreases (not shown in the figure). This process is repeated when the next clock cycle CLK arrives. At time t3, the input voltage Vin increases (taking Vin increasing as an example; the process of Vin decreasing is the opposite, increasing the inductor current through the input feedforward signal Vff). At this time, the input voltage feedforward circuit detects the change in input voltage and outputs the input feedforward signal Vff. Figure 7 As can be seen, the first difference signal Vc1 begins to decrease at time t3. At time t4, when the clock signal CLK is generated, the main switch Q1 is turned on, the current sampling signal Visns begins to increase, and the ramp signal Vramp is generated simultaneously. The first difference signal Vc1 = Vc0 - Vramp - Vff. When Vin increases, Vff is greater than 0. Therefore, the value of the inductor current sampling signal Visns when it rises to the first difference signal Vc1 is less than the value of Visns when it rose to Vc1 before time t3. Therefore, by introducing the input feedforward signal Vff, the inductor current can be reduced, avoiding the problem in the prior art where an increase in input voltage leads to an increase in inductor current, resulting in a large output voltage ripple. The proposed solution reduces the output voltage ripple and improves the system stability. Subsequently, after the input voltage Vin stabilizes, the input feedforward signal Vff will gradually decrease over time, and the error amplification signal Vc0 will also decrease synchronously, eventually reaching a steady state.

[0044] As mentioned above, ignoring the effect of converter efficiency, the input power of the converter equals the output power, i.e., Vin*Iin = Vout*Iout. When the input voltage fluctuates, the input power still needs to equal the output power, i.e., (Vin + ΔVin)*(Iin + ΔIin) = Vout*Iout. Ignoring the effect of higher-order terms, we have... This equation shows that for the same input voltage change ΔVin, the change in input current ΔIin is inconsistent when the input current Iin (i.e., the average inductor current) is different. The larger the input current Iin, the larger the change in input current, indicating that the input feedforward signal Vff needs to be increased. Furthermore, the input voltage feedforward circuit can adjust the input feedforward signal based on the magnitude of the average inductor current of the boost converter, ensuring that the input feedforward signal is larger when the average inductor current of the boost transformer is larger, thereby further optimizing the output voltage ripple under different load conditions.

[0045] Furthermore, the input voltage feedforward circuit will also be explained using a high-pass filter circuit as an example. Figure 8 The diagram shows another embodiment of the input voltage feedforward circuit provided by the present invention, which is similar to... Figure 5 The difference lies in that the second resistor R2 is composed of multiple sub-resistors R21-R2n, where n is greater than or equal to 1. In this embodiment, the sub-resistors R21-R2n are connected in series, and switches S2-Sn are connected in parallel across the sub-resistors R22-R2n. Switches S2-Sn are controlled by the output signals of comparators CMP2-CMPn. The first input terminals of comparators CMP2-CMPn all receive the average inductor current signal Visns_ave, and the second input terminals of comparators CMP2-CMPn receive multiple current thresholds Ire1-Irefn-1, and multiple current thresholds Ire1-Irefn-1, respectively. The input feedforward signal is set to increase sequentially. For example, when the average inductor current signal Visns_ave is less than Iref1, switches S2-Sn are closed, and the equivalent resistance of R2 equals R21, resulting in a relatively small input feedforward signal. When the average inductor current signal Visns_ave is greater than Iref1 but less than Iref2, switch S2 is opened, and switches S3-Sn are closed, increasing the equivalent resistance of R2 to R21+R22 and thus increasing the input feedforward signal. This process continues as the average inductor current signal Visns_ave increases, thereby increasing the value of the second resistor R2 and consequently increasing the input feedforward signal. This paper, based on the magnitude of the average inductor current of the step-up transformer, sets multiple sub-resistors with different connection methods to ensure that when the average inductor current of the step-up transformer exceeds several progressively increasing thresholds, the resistance of the second resistor R2 increases accordingly, thereby increasing the input feedforward signal and optimizing the output voltage ripple under different load conditions.

[0046] like Figure 4 As shown, the control circuit may also include a compensation module, which is set at the output of the error amplifier circuit. The compensation module can be set by a combination of resistors and capacitors according to the actual application to improve the stability of the system.

[0047] As another embodiment of the present invention, such as Figure 9 As shown, the difference between the error amplification signal Vc0 and the ramp signal Vramp is used as the signal at the first input terminal of the first comparator CMP1. The inductor current sampling signal Visns during the conduction phase of the main switch Q1 is superimposed with the input feedforward signal Vff as the signal at the second input terminal of the first comparator CMP1. When the output of the first comparator CMP1 flips, the main switch Q1 is turned off. The specific function and circuit of the input voltage feedforward circuit are described above and will not be repeated here. In this embodiment, by superimposing the input feedforward signal Vff on the current sampling signal Visns, the peak value of the inductor current can be controlled to control the magnitude of the inductor current when the input voltage changes, thereby optimizing the output voltage ripple and improving the system stability.

[0048] This invention also provides a control method for a boost converter, the method comprising: generating an error amplification signal based on an output voltage feedback signal and a reference voltage signal; generating a ramp signal when the main switch of the boost converter is turned on; the inductor current of the boost converter rising when the main switch is turned on; generating an input feedforward signal based on the input voltage; subtracting the difference between the error amplification signal and the ramp signal from the input feedforward signal to obtain a first difference signal; comparing the first difference signal with the inductor current sampling signal during the main switch's on-state to obtain a comparison signal; or, superimposing the inductor current sampling signal during the main switch's on-state with the input feedforward signal to obtain a first sum signal; comparing the difference between the error amplification signal and the ramp signal with the first sum signal to obtain a comparison signal; and controlling the main switch to turn off when the comparison signal flips.

[0049] In addition, this control method also has other functions that the control circuit described above has, which will not be elaborated here.

[0050] The present invention also provides a boost converter for converting input voltage into output voltage, which controls the main switching transistor in the boost converter based on the control circuit described above or the control method described above.

[0051] In summary, the boost converter and its control circuit and method provided by this invention generate an input feedforward signal based on the input voltage. The difference between the error amplification signal and the ramp signal is then subtracted from the input feedforward signal to obtain a first difference signal. This first difference signal is compared with the inductor current sampling signal during the main switch's conduction phase to obtain a comparison signal. Alternatively, the inductor current sampling signal during the main switch's conduction phase is superimposed with the input feedforward signal to obtain a first sum signal. The difference between the error amplification signal and the ramp signal is then compared with the first sum signal to obtain the comparison signal. When the comparison signal flips, the main switch is turned off. When the input voltage changes, this invention introduces an input feedforward signal, which controls the peak value of the inductor current to control its magnitude, thereby optimizing the output voltage ripple and improving system stability.

[0052] Furthermore, the input voltage is filtered by any of the high-pass, low-pass, or band-pass filters to generate an input feedforward signal. Moreover, the amount of the input feedforward signal can be adjusted based on the magnitude of the average current of the step-up transformer inductor, so that the larger the average current of the step-up transformer inductor, the larger the amount of the input feedforward signal, thereby further optimizing the output voltage ripple under different load conditions.

[0053] Finally, it should be noted that the above embodiments are merely examples for clearly illustrating the present invention and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A boost converter control circuit, wherein the boost converter is used to convert an input voltage into an output voltage, characterized in that, The control circuit includes: An error amplification module, which generates an error amplification signal based on the output voltage feedback signal and the reference voltage signal; A ramp signal generation module is provided, which is used to generate a ramp signal when the main switch of the boost converter is turned on; when the main switch is turned on, the inductor current of the boost converter increases. An input voltage feedforward circuit generates an input feedforward signal based on the input voltage. The first comparator takes the difference between the amplified error signal and the ramp signal, and then subtracts it from the input feedforward signal to obtain the signal at the first input terminal of the first comparator. The second input terminal of the first comparator receives the inductor current sampling signal during the conduction phase of the main switch. Alternatively... The difference between the error amplification signal and the ramp signal is used as the signal at the first input terminal of the first comparator. The inductor current sampling signal during the conduction phase of the main switch is superimposed with the input feedforward signal as the signal at the second input terminal of the first comparator. When the comparator output flips, the main switch is controlled to turn off.

2. The control circuit according to claim 1, characterized in that, The input voltage feedforward circuit is any one of a high-pass filter circuit, a low-pass filter circuit, or a band-pass filter circuit. It receives the input voltage and generates the input feedforward signal based on the change in the input voltage.

3. The control circuit according to claim 2, characterized in that, The larger the average inductance of the step-up transformer, the larger the input feedforward signal.

4. The control circuit according to claim 2, characterized in that, When the input voltage feedforward path is a high-pass filter circuit, the input voltage feedforward includes a first capacitor, a first resistor, and a second resistor connected in series between the input voltage and the ground terminal, and the input feedforward signal is generated at the common node of the first resistor and the second resistor.

5. The control circuit according to claim 4, characterized in that, The second resistor is composed of multiple sub-resistors. Based on the magnitude of the average current of the step-up transformer inductor, the multiple sub-resistors are configured with different connection methods so that when the average current of the step-up transformer inductor is greater than a number of progressively increasing threshold values, the resistance value of the second resistor increases accordingly.

6. The control circuit according to claim 1, characterized in that, The control circuit also includes a logic control and drive signal generation module, which generates signals to control the corresponding switching transistors in the boost converter to turn on or off based on the output signal and clock signal of the first comparator. The switching cycle of the boost converter is controlled based on the clock signal.

7. The control circuit according to claim 1, characterized in that, The ramp signal generation circuit includes a second capacitor. During the main switch transistor's conduction phase, a first current source acts on the second capacitor to generate the ramp signal. After the main switch is turned off, the second capacitor discharges.

8. The control circuit according to claim 1, characterized in that, The control circuit also includes a compensation module, which is located at the output of the error amplifier circuit.

9. A control method for a boost converter, characterized in that, The boost converter is used to convert input voltage into output voltage, characterized in that the control method includes: An error amplification signal is generated based on the output voltage feedback signal and the reference voltage signal; A ramp signal is generated when the main switch of the boost converter is turned on; when the main switch is turned on, the inductor current of the boost converter rises. An input feedforward signal is generated based on the input voltage; The difference between the amplified error signal and the ramp signal is then subtracted from the input feedforward signal to obtain a first difference signal. This first difference signal is then compared with the inductor current sampling signal during the main switch's conduction phase to obtain a comparison signal; or... The inductor current sampling signal during the conduction phase of the main switch is superimposed with the input feedforward signal to obtain a first sum signal. The difference between the error amplification signal and the ramp signal is compared with the first sum signal to obtain a comparison signal. When the comparison signal flips, the main switch is controlled to turn off.

10. The control method according to claim 9, characterized in that, The input voltage is processed by any one of high-pass filtering, low-pass filtering, or band-pass filtering to generate the input feedforward signal.

11. The control method according to claim 10, characterized in that, The larger the average inductance of the step-up transformer, the larger the input feedforward signal.

12. A boost converter for converting input voltage into output voltage, characterized in that, The boost converter includes the control circuit according to any one of claims 1-8, or the control method according to any one of claims 9-11 is used to control the main switching transistor in the boost converter.

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