Low-interference and high-compatibility PWM (Pulse Width Modulation) generation circuit and motor controller

Abstract

The invention provides a low-interference and high-compatibility PWM (Pulse Width Modulation) generation circuit and a motor controller. The circuit comprises a PWM signal generation module, a charging and discharging module, a voltage source and a direct current power supply. The PWM signal generation module outputs a PWM signal through a first resistor, a second resistor, a third resistor and a high-speed comparator; the charging and discharging module is composed of a first capacitor and a fourth resistor, and the charging and discharging threshold of the charging and discharging module is set by the PWM signal generation module. The voltage source is electrically connected with the PWM signal generation module, the PWM output frequency is continuously changed by dynamically changing the threshold voltage of the high-speed comparator, harmonic energy is dispersed to a wider frequency band, and the EMI peak intensity is remarkably reduced. According to the design, the electromagnetic compatibility is optimized with a relatively simple structure and low cost, and the circuit is particularly suitable for a high-frequency miniaturized isolated power supply scene.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of new energy vehicles, in particular to a low-interference high-compatibility PWM generating circuit and motor controller. BACKGROUND

[0002] In the motor control system, the PWM generating circuit as the core component of the open loop isolation power supply is widely used to drive the power module and realize high efficiency energy conversion. With the development of motor controller to high frequency and miniaturization, the PWM working frequency has been increased to 1-10MHz range, which puts forward higher requirements for electromagnetic compatibility (EMC). The fixed frequency characteristic of high frequency PWM signal causes the harmonic energy to concentrate in a single frequency point, which causes significant electromagnetic interference (EMI) peak, seriously affecting the stability of adjacent electronic equipment and system. It has become a bottleneck restricting the application of high frequency isolation power supply.

[0003] In the prior art, the scheme for improving EMC performance depends on external control chips or complex filter circuits. For example, although the interference can be suppressed by increasing the EMI filter or optimizing the power device package, the system volume and cost are significantly increased; and the random pulse width modulation (RPWM) strategy can disperse the frequency spectrum energy, but it needs complex algorithm support and introduces additional control delay. In addition, the frequency modulation function of the traditional scheme often needs independent power supply module or multi-stage circuit cooperation, which leads to poor compatibility and is difficult to adapt to wide input voltage range. These problems make the existing technology difficult to balance between cost, complexity and performance, and cannot meet the stringent requirements of high frequency miniaturized isolation power supply.

[0004] Therefore, there is an urgent need for a PWM generating circuit with simple structure, low cost and meeting the electromagnetic compatibility requirements. SUMMARY

[0005] In order to overcome the above technical defects, the purpose of the present application is to provide a low-interference high-compatibility PWM generating circuit and motor controller.

[0006] The present application discloses a low-interference high-compatibility PWM generating circuit. The PWM generating circuit comprises: A PWM signal generating module, the PWM signal generating module comprises a first resistor, a second resistor, a third resistor and a high-speed comparator; the high-speed comparator outputs a PWM signal based on the resistance values of the first resistor, the second resistor and the third resistor; A charge and discharge module, the charge and discharge module comprises a first capacitor and a fourth resistor, and the charge and discharge threshold of the charge and discharge module is determined by the PWM signal generating module; A voltage source, the voltage source is electrically connected with the PWM signal generating module, and changes the threshold of the high-speed comparator, so that the frequency of the PWM signal generating module continuously changes; A direct current power supply is connected with the PWM signal generating module and supplies power for the charging and discharging module.

[0007] Preferably, the voltage source generates at least one wave including square wave, sawtooth wave and sine wave.

[0008] Preferably, the second resistor is arranged between the grounding point and the high-speed comparator; the voltage source is connected in series with the second resistor and arranged on the side of the second resistor close to the grounding point.

[0009] Preferably, the non-inverting input terminal of the high-speed comparator U8 of the PWM generating circuit is connected with the other end of the third resistor R28, the other end of the second resistor R25 and the other end of the first resistor R24; the inverting input terminal is connected with one end of the first capacitor C13 and one end of the fourth resistor R21; the output terminal of the high-speed comparator U8 is connected with the other end of the first resistor R24 and one end of the fourth resistor R21. The third resistor R28 has one end connected with the direct current power supply P5V and the other end connected with the non-inverting input terminal of the high-speed comparator U8. The second resistor R25 has one end connected with the voltage source and the other end connected with the non-inverting input terminal of the high-speed comparator U8. The first resistor R24 has one end connected with the non-inverting input terminal of the high-speed comparator U8 and the other end connected with the output terminal of the high-speed comparator U8. The fourth resistor R21 has one end connected with the output terminal of the high-speed comparator U8 and the other end connected with the inverting input terminal of the high-speed comparator U8, i.e. one end of the first capacitor C13. The first capacitor C13 has one end connected with the other end of the fourth resistor R21 and the other end connected with the grounding point. The voltage source U4 has one end connected with the second resistor R25 and the other end connected with the grounding point. The PWM generating circuit further comprises a resistor R22 having one end connected with the output terminal of the high-speed comparator U8 and the other end connected with the grounding point.

[0010] Preferably, the voltage source comprises the same structure as the PWM signal generating module and the charging and discharging module; the voltage source generates square wave.

[0011] Preferably, the voltage source is electrically connected with the direct current power supply and supplied by the direct current power supply.

[0012] Preferably, the input voltage of the direct current power supply is 3V-6V and the voltage of the voltage source is 0V-1V.

[0013] Preferably, the duty cycle of the voltage source is 40%-60%.

[0014] Preferably, the output frequency of the voltage source is 35kHz-45kHz.

[0015] The second aspect of the scheme also discloses a motor controller, the motor controller comprises an isolated power supply, and the isolated power supply adopts the PWM generation circuit according to any one of the foregoing embodiments.

[0016] After the technical scheme is adopted, compared with the prior art, the following beneficial effects are obtained: 1. The scheme dynamically changes the threshold voltage of the high-speed comparator through the voltage source, so that the PWM output frequency continuously dithers in the set range. Compared with the harmonic energy of the fixed frequency PWM, which is concentrated and accumulated at a single frequency point, resulting in a too high EMI peak value, by providing the voltage source, the harmonic energy can be dispersed to a wider frequency band, significantly reducing the peak intensity. The charging and discharging module cooperates with the voltage source, so that the frequency dithering process does not need external control chip intervention, and only relies on a single power supply to realize frequency spectrum diffusion. This design maintains circuit compatibility and low cost while fundamentally optimizing EMC performance, especially suitable for high-frequency miniaturized isolated power supply scenarios; 2. The voltage source supports multiple waveform outputs, such as square wave and sawtooth wave, providing flexible frequency spectrum dispersion modes for different electromagnetic environments; when the voltage source output is also a square wave, the voltage source can be built with the same method as the PWM generation module, a second PWM generation module is built, the output end of the second PWM generation module is used to provide the voltage source, and the second PWM generation module can also reuse the resistance voltage division structure of the PWM signal generation module. Significantly reduces the number of independent components and reduces costs. By sharing the DC power supply, avoid timing conflicts of multiple power supplies, and ensure the synchronization of the dithering signal and the PWM generation. 3. By directly integrating the foregoing PWM generation circuit into the isolated power supply of the motor controller, the high EMI peak value problem of the high-frequency power module can be solved, and the electromagnetic compatibility performance of the motor controller can be significantly improved by dispersing the harmonic energy peak value of the power supply end. Moreover, only two high-speed comparators and basic passive components are needed, without the need for additional independent control chips, which can effectively reduce the EMI peak value related to the switching tube voltage stress in the flyback power stage circuit and other scenarios, while improving the electromagnetic compatibility performance, maintaining the advantages of circuit miniaturization and low cost. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The structure diagram of the low-interference high-compatibility PWM generation circuit provided in the application; Figure 2 The structure diagram of the voltage source in the low-interference high-compatibility PWM generation circuit provided in the application; Figures 3-4 The data diagram of the PWM generation circuit without a voltage source; Figures 5-6 The data diagram of the low-interference high-compatibility PWM generation circuit provided in the application.

[0018] Reference signs: R24, first resistor; R25, second resistor; R28, third resistor; U8, high-speed comparator; C13, first capacitor; R21, fourth resistor; V4, voltage source; P5V, DC power supply. DETAILED DESCRIPTION

[0019] The advantages of the present application are further set forth in the description that follows, and will be appreciated by persons skilled in the art upon reading and understanding the attached figures and detailed description.

[0020] Exemplary embodiments are described herein below with reference to the accompanying drawings. In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments. It can be evident, however, that the present application can be practiced without these specific details. In other instances, well-known structures and functions have not been described in detail in order to avoid obscuring the description of the one or more embodiments.

[0021] The terminology used in the description of the present application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. As used in the description of the present application and the appended claims, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It also will be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0022] It is to be understood that the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. It is to be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. In the description of the present application, it is to be understood that the terms "longitudinal", "lateral", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like are terms of convenience and are not to be construed as limiting on the present application unless otherwise indicated by context.

[0023] In the description of the present application, unless otherwise specified and limited, it is necessary to explain that the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be mechanical connection or electrical connection, it can be the communication inside two elements, it can be direct connection or indirect connection through intermediate medium, and the specific meaning of the above terms can be understood by the person skilled in the art according to the specific situation.

[0024] In the subsequent description, the suffix such as "module", "component" or "unit" used to represent the element is only for the convenience of the description of the present application, and has no specific meaning itself. Therefore, "module" and "component" can be used mixedly.

[0025] Please refer to Figure 1 , Figure 1 The structure diagram of the low-interference high-compatibility PWM generation circuit provided in the present application is shown.

[0026] As Figure 1 shown, the present application provides a low-interference high-compatibility PWM generation circuit. The PWM generation circuit comprises: A PWM signal generation module, the PWM signal generation module comprises a first resistor R24, a second resistor R25, a third resistor R28 and a high-speed comparator U8; the high-speed comparator U8 outputs a PWM signal based on the resistance values of the first resistor R24, the second resistor R25 and the third resistor R28; A charge and discharge module, the charge and discharge module comprises a first capacitor C13 and a fourth resistor R21, and the charge and discharge threshold of the charge and discharge module is determined by the PWM signal generation module; A voltage source V4, the voltage source V4 is electrically connected with the PWM signal generation module, and changes the threshold value of the high-speed comparator U8, so that the frequency of the PWM signal generation module continuously changes; A DC power supply P5V, the DC power supply P5V is electrically connected with the charge and discharge module and supplies power for the charge and discharge module.

[0027] The scheme dynamically changes the threshold voltage of the high-speed comparator U8 through the voltage source V4, so that the PWM output frequency continuously dithers in the set range. The harmonic energy of the traditional fixed frequency PWM is concentrated and accumulated in a single frequency point, resulting in too high peak value of electromagnetic interference (EMI); and by setting the voltage source V4, the harmonic energy can be dispersed to a wider frequency band, significantly reducing the peak strength. The charge and discharge module works with the voltage source V4, so that the frequency dithering process does not need external control chip intervention, and only relies on a single power supply to realize frequency spectrum diffusion. This design maintains the compatibility and low cost of the circuit, and fundamentally optimizes the electromagnetic compatibility (EMC) performance, especially suitable for high-frequency miniaturized isolation power supply scenarios.

[0028] The above is a description of the basic concept of the present application, and the specific structure of each component of the present application will be described in detail below.

[0029] Those skilled in the art can understand that the specific implementation of the voltage source V4 is not limited.

[0030] In one possible implementation, the voltage source V4 outputs at least one of a square wave, a sawtooth wave, and a sine wave.

[0031] By limiting the voltage source to output multiple waveforms such as square waves, sawtooth waves, or sine waves, the flexibility of the circuit application is enhanced. Different waveforms can adapt to diversified EMI optimization needs, for example, square waves are suitable for fast frequency switching, and sine waves achieve smooth spectrum diffusion. This design provides a multi-mode solution for electromagnetic compatibility optimization without increasing hardware complexity, improving the adaptability of the circuit in a complex electromagnetic environment.

[0032] It can be understood here that the waveform output by the voltage source V4 will directly affect the threshold voltage waveform of the high-speed comparator U8, for example, in one possible implementation, the voltage source V4 outputs a sine wave, which can make the threshold voltage waveform of the high-speed comparator U8 smoother, so that the PWM frequency output by it is continuously dispersed between the set frequency threshold, thereby significantly reducing the peak value of electromagnetic interference (EMI), and thus optimizing electromagnetic compatibility (Electromagnetic Compatibility). In another possible implementation, the voltage source V4 can also output a square wave, at which time the PWM frequency output is dispersedly distributed between the set frequency threshold, and is cyclically switched between several discrete frequency points, which can also significantly reduce the peak value of EMI, thereby optimizing electromagnetic compatibility, and the mechanism of the voltage source V4 itself can also be designed to be relatively simple, thereby achieving low interference and high compatibility of the PWM generation circuit with a low-cost solution. Those skilled in the art can design it according to their needs, and the present application does not make any limitation here.

[0033] Please refer to Figure 2 , Figure 2 The structure diagram of the voltage source in the low-interference and high-compatibility PWM generation circuit provided by the present application.

[0034] As Figure 2 shown, the voltage source internally includes the same structure as the PWM signal generation module and the charge and discharge module structure, etc., so that the voltage source outputs a square wave.

[0035] Here or can be understood as: in a possible implementation, the entire PWM generation circuit can include two layers of the same structure set. The PWM signal generation module and the charge and discharge module of the outer layer are the modules of the PWM generation circuit, and the PWM signal generation module and the charge and discharge module of the inner layer constitute the voltage source V4.

[0036] It should be noted that at this time, although the inner layer and the outer layer are consistent, the specific design parameters can be different (for example, the resistance values of the first resistors R24 of the inner layer and the outer layer are different), and the specific needs are determined according to the overall design requirements of the voltage source U4 and the PWM generation circuit. Those skilled in the art can freely design according to the needs, and the present application does not make any limitation here.

[0037] Through such simple structure reuse, the BOM cost can be greatly reduced, and there is no need to independently design a frequency modulation circuit. The reuse structure ensures the timing synchronization of the frequency modulation signal and the PWM signal, avoids phase conflict, and improves system integration and reliability.

[0038] The above is a possible implementation of the voltage source provided by the present application.

[0039] Those skilled in the art can understand that the specific arrangement position of the voltage source V4 is also not limited.

[0040] In a possible implementation, the second resistor R25 is arranged between the grounding point and the high-speed comparator U8; the voltage source V4 is connected in series with the second resistor R25 and is arranged on the side of the second resistor R25 close to the grounding point.

[0041] By setting the voltage source V4 as such a one-end grounding structure, the voltage source V4 does not need to be set as a differential source, but only needs to be single-endedly connected to the circuit, thereby simplifying the implementation of the frequency jitter function, avoiding additional circuit interference, while ensuring accurate control of the PWM core frequency, and improving the anti-interference ability and frequency response speed.

[0042] At this time, the overall structure of the PWM generation circuit is as shown in Figure 1 . The non-inverting input terminal of the high-speed comparator U8 of the PWM generation circuit is connected with one end of the first capacitor C13 and one end of the fourth resistor R21; the output terminal of the high-speed comparator U8 is connected with the other end of the first resistor R24 and one end of the fourth resistor R21. The third resistor R28 is connected with the direct current power supply P5V at one end and connected with the non-inverting input terminal of the high-speed comparator U8 at the other end. The second resistor R25 is connected with the voltage source at one end and connected with the non-inverting input terminal of the high-speed comparator U8 at the other end. The first resistor R24 has one end connected to the non-inverting input of the high-speed comparator U8 and the other end connected to the output of the high-speed comparator U8; The fourth resistor R21 has one end connected to the output of the high-speed comparator U8 and the other end connected to the inverting input of the high-speed comparator U8, i.e. one end of the first capacitor C13; The first capacitor C13 has one end connected to the other end of the fourth resistor R21 and the other end grounded; The voltage source U4 has one end connected to the second resistor R25 and the other end grounded; The PWM generation circuit further comprises a resistor R22 having one end connected to the output of the high-speed comparator U8 and the other end grounded.

[0043] It should be noted that the power supply mode of the voltage source V4 is also not limited.

[0044] In a possible implementation, the voltage source V4 is electrically connected with the DC power supply P5V and is powered by the DC power supply P5V.

[0045] By sharing the DC power supply P5V with the PWM signal generation module, the need for independent power supply is eliminated. This design drives the core PWM generation and frequency jitter function simultaneously through a single power supply, reduces the complexity of external interface and power management, reduces power consumption and circuit size. Power coordination also avoids the frequency jitter deviation caused by the asynchronous timing of multiple power supplies, improves the stability of frequency jitter, and makes the circuit cost lower and more cost-effective.

[0046] The above is a description of the specific structure and setting method of the voltage source V4 provided by the present application.

[0047] Those skilled in the art can understand that the specific parameters of the voltage source V4 need to be designed according to the specific parameter requirements of the PWM generation circuit. For example, when the frequency of the PWM generation circuit is high and the operating voltage is high, the parameters of the voltage source V4 can be set relatively high to further optimize the electromagnetic compatibility. The present application is also not limited in this regard.

[0048] Therefore, for example, in a possible implementation, the input voltage of the DC power supply P5V is 3V-10V, and the voltage of the voltage source V4 is 0V-1V.

[0049] By reasonably designing the cooperation between the input voltage range of the DC power supply P5V and the voltage range of the voltage source, the circuit can be ensured to work stably under wide input voltage. The low amplitude frequency modulation voltage avoids overloading the PWM core voltage division network, while accurately controlling the frequency jitter amplitude, optimizing the energy consumption performance of the PWM generation circuit.

[0050] Further, the duty cycle and output frequency at this time are also not limited.

[0051] In a possible implementation, the duty cycle of the voltage source V4 is 40%-60%. The output frequency of the voltage source V4 is 35 kHz-45 kHz.

[0052] The voltage source duty cycle is limited to a reasonable range, so that the frequency jitter is symmetrically distributed. This range balances the energy dispersion effect of the high and low frequency bands, avoiding the re-aggregation of spectral energy. Symmetric jitter improves the uniformity of EMI suppression, while maintaining the stability of the PWM main frequency duty cycle, ensuring that the power transmission efficiency is not affected by jitter. The voltage source output frequency is limited to a specific intermediate frequency range, which provides the best modulation frequency band for the high-frequency PWM main frequency. This modulation frequency band ensures sufficient harmonic dispersion width and avoids intermodulation interference with the PWM fundamental frequency. Precise frequency range design optimizes EMI suppression effect, while ensuring that the modulation signal does not affect the core circuit timing.

[0053] The above is an exemplary description of the PWM generation circuit structure and parameters provided by the present application. In order to make those skilled in the art more easily understand the present application, the present application also provides an embodiment for reference, and better illustrates the technical effects of the present application.

[0054] Please refer to Figures 3-4 for the data graph of the PWM generation circuit without a voltage source; Figures 5-6 for the data graph of the low-interference high-compatibility PWM generation circuit provided by the present application.

[0055] As shown in Figures 3-4 , the design parameters of the PWM generation circuit are as follows: the P5V voltage is 5V. The first resistor R24, the second resistor R25, and the third resistor R28 are all 10kΩ. The fourth resistor R21 is 1kΩ, and the first capacitor C13 is 150pF. The PWM frequency is 4.2MHz, and the PWM duty cycle is 50%. The corresponding parameters of the flyback power stage circuit are as follows: the input voltage is 15.7V, the output load is 400Ω, and the output voltage is 23V.

[0056] As shown in Figures 3-4 , when the circuit is in steady state, the charge and discharge module cycles between the lower threshold value 1.67V and the upper threshold value 3.27V, with an output frequency of about 4.2MHz and a duty cycle of 51%.

[0057] At this time, Fourier analysis of the EMI key network (MOS tube drain-source voltage) waveform shows that the main energy of Vds is concentrated at the circuit switching frequency of 4.2MHz, with a maximum amplitude of 25.5V. The rest of the energy is concentrated at the multiple of the switching frequency.

[0058] As shown in Figures 5-6 , the Fourier analysis of the EMI key network (MOS tube drain-source voltage) waveform shows that the main energy of Vds is concentrated at the circuit switching frequency of 4.2MHz, with a maximum amplitude of 25.5V. The rest of the energy is concentrated at the multiple of the switching frequency.As shown, the PWM generation circuit provided in the present application, in the case of consistent design parameters, when the voltage source V4 is 0V, the charging and discharging waveform of the first capacitor C13 is consistent with the waveform when the voltage source V4 is not loaded, that is, the voltage of the first capacitor C13 is cyclically charged and discharged between 1.67V and 3.27V, at this time the PWM output frequency is about 4.2MHz, and the duty cycle is 51%. When the voltage source V4 is 1V, the upper and lower limits of the charging and discharging of the first capacitor C13 will be 2V and 3.6V, and the change of the upper and lower limits of the charging and discharging will cause the change of the charging and discharging time, thereby changing the PWM output, the frequency of the PWM is about 4.07MHz, and the duty cycle is 51%. When the first capacitor C13 switches between 0V and 1V, the output PWM will switch between 4.07MHz and 4.19MHz, thereby realizing frequency jittering.

[0059] From the Fourier analysis of the EMI key network (MOS tube drain-source voltage) waveform, it can be seen that the main energy of Vds is concentrated at the switching frequency of the circuit 4.08MHz, and the maximum amplitude is 14.9V; the rest of the energy is concentrated at the multiple frequency of the switching frequency. It can be seen that when the frequency jittering PWM circuit is used, the harmonic energy concentrated at the switching frequency is obviously reduced and distributed to the rest of the multiple frequency.

[0060] Therefore, the PWM generation circuit provided in the present application can greatly reduce the electromagnetic interference energy while being low in cost and simple in structure, thereby realizing good circuit performance and compatibility, and being suitable for high-frequency isolation power supply scenarios.

[0061] The second aspect of the present application also provides a motor controller, which comprises an isolation power supply, and the isolation power supply adopts the PWM generation circuit according to any one of the preceding embodiments.

[0062] By directly integrating the foregoing PWM generation circuit into the isolation power supply of the motor controller, the high EMI peak value problem of the high-frequency power module can be solved, and the electromagnetic compatibility performance of the motor controller can be significantly improved by dispersing the harmonic energy peak value of the power supply end. Moreover, only two high-speed comparators U8 and basic passive elements are needed, without the need to add an independent control chip, so that the EMI peak value related to the voltage stress of the switching tube in the flyback power stage circuit and the like can be effectively reduced, the electromagnetic compatibility performance is improved, and the circuit is kept small and low in cost.

[0063] It should be noted that the embodiments of the present application have better implementation, and do not limit the present application in any form, and any skilled person in the art can change or modify the above-mentioned disclosed technical content into equivalent effective embodiments, as long as the content of the technical solution of the present application is not deviated, and any modification or equivalent change and modification of the above-mentioned embodiments according to the technical essence of the present application are still within the scope of the technical solution of the present application.

Claims

1. A low-interference, high-compatibility PWM generation circuit, characterized in that, The PWM generating circuit comprises: a PWM signal generating module, which comprises a first resistor, a second resistor, a third resistor and a high-speed comparator; the high-speed comparator outputs a PWM signal based on the resistance values of the first resistor, the second resistor and the third resistor; a charging and discharging module, which comprises a first capacitor and a fourth resistor, and the charging and discharging threshold of the charging and discharging module is determined by the PWM signal generating module; a voltage source, which is electrically connected with the PWM signal generating module, changes the threshold of the high-speed comparator, and makes the frequency of the PWM signal generating module continuously change; a direct current (DC) power supply, which is connected with the PWM signal generating module and supplies power for the charging and discharging module.

2. The PWM generation circuit of claim 1, wherein, The voltage source sends at least one wave including a square wave, a sawtooth wave and a sine wave.

3. The PWM generation circuit of claim 2, wherein, The second resistor is arranged between a grounding point and the high-speed comparator; the voltage source is connected in series with the second resistor and is arranged on the side of the second resistor close to the grounding point.

4. The PWM generation circuit of claim 3, wherein, The non-inverting input end of the high-speed comparator U8 of the PWM generating circuit is connected with the other end of the third resistor R28, the other end of the second resistor R25 and the other end of the first resistor R24; the inverting input end is connected with one end of the first capacitor C13 and one end of the fourth resistor R21; the output end of the high-speed comparator U8 is connected with the other end of the first resistor R24 and one end of the fourth resistor R21; the third resistor R28 has one end connected with the DC power supply P5V and the other end connected with the non-inverting input end of the high-speed comparator U8; the second resistor R25 has one end connected with the voltage source and the other end connected with the non-inverting input end of the high-speed comparator U8; the first resistor R24 has one end connected with the non-inverting input end of the high-speed comparator U8 and the other end connected with the output end of the high-speed comparator U8; the fourth resistor R21 has one end connected with the output end of the high-speed comparator U8 and the other end connected with the inverting input end of the high-speed comparator U8, i.e. one end of the first capacitor C13; the first capacitor C13 has one end connected with the other end of the fourth resistor R21 and the other end grounded; the voltage source U4 has one end connected with the second resistor R25 and the other end grounded; The PWM generating circuit further comprises a resistor R22, which has one end connected with the output end of the high-speed comparator U8 and the other end grounded.

5. The PWM generation circuit of claim 1, wherein, The voltage source comprises the same structure as the PWM signal generating module and the charging and discharging module; the voltage source sends a square wave.

6. The PWM generation circuit of claim 5, wherein, The voltage source is electrically connected with the DC power supply and is powered by the DC power supply.

7. The PWM generation circuit of claim 5, wherein, The input voltage of the DC power supply is 3V-6V, and the voltage of the voltage source is 0V-1V.

8. The PWM generation circuit of claim 5, wherein, The duty cycle of the voltage source is 40%-60%.

9. The PWM generation circuit of claim 5, wherein, The output frequency of the voltage source is 35kHz-45kHz.

10. An electric machine controller characterized by The motor controller comprises an isolation power supply, which adopts the PWM generating circuit as claimed in claims 1-9.

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