Electromagnetic Interference Suppression Circuit of Dash Cam

Abstract

The present invention relates to the technical field of driving recorders, and discloses an electromagnetic interference suppression circuit for a driving recorder, which includes a spread spectrum clock generator that attenuates the peaks of unnecessary electromagnetic interference by slightly modulating the oscillation frequency regularly using an internal modulator; an oscillator for calibrating the crystal frequency input to the spread spectrum clock generator; a spread spectrum frequency adjustment unit for adjusting the crystal frequency input to the spread spectrum clock generator; a spread spectrum frequency output unit for adjusting the spread spectrum frequency output by the spread spectrum clock generator and then outputting it to the system clock of the main chip of the driving recorder; and a power supply unit for providing a working power supply for the spread spectrum clock generator. The present invention does not need to determine the circuit parameters of the electromagnetic interference reduction circuit through a trial-and-error method or calculation, thereby solving the problem of electromagnetic interference suppression in the PCB design of driving recorder products.

Description

Technical Field

[0001] The present invention relates to the technical field of driving recorders, and particularly to an electromagnetic interference suppression circuit for a driving recorder. Background Art

[0002] In the past few decades, more and more applications are being digitalized. The implementation of digital systems is very simple because it is all about logic; however, as the signal speed increases, the complexity grows exponentially, especially issues such as clock synchronization, setup and hold times, jitter, etc. These problems not only affect the function of individual subsystems but also cause electromagnetic interference when high-frequency devices are close.

[0003] Electromagnetic interference is an unwanted system response because it can either be electromagnetic radiation itself or radiation emitted from an external source. This adverse response or interference may interrupt and degrade the effective performance of any electronic system and may lead to the failure of the entire system. Therefore, controlling electromagnetic interference in any electronic system has become an important design issue for electronic system designers.

[0004] Traditional electromagnetic interference design uses magnetic beads or resistor-capacitor matching circuits to suppress electromagnetic interference. Since magnetic beads suppress electromagnetic interference by energy absorption, they are only ideal for suppressing electromagnetic interference at a single frequency point; the resistor-capacitor matching method is to reasonably match the clock or circuit-sensitive signals to reduce signal reflection, so that energy can be transferred to the next-stage circuit more efficiently, and electromagnetic interference can be better suppressed. However, in the actual debugging of a PCB board, it is relatively difficult to determine the impedance of the circuit, and only the trial-and-error method can be used to determine the matching circuit parameters, without a theoretical basis, and it is difficult to find the optimal solution.

[0005] The patent with publication number CN107171545A discloses an electromagnetic interference suppression circuit, including a first input terminal, a second input terminal, a transient voltage suppression module, a filtering module, an anti-backlash interference module, a first output terminal, and a second output terminal. The transient voltage suppression module and the filtering module are both connected to the first input terminal and the second input terminal to receive the signals input from the first input terminal and the second input terminal. The filtering module is also connected to the first output terminal and the second output terminal through the anti-backlash interference module. The transient voltage suppression module is used to absorb the high-voltage noise in the input signal so that the voltage of the signal received by the filtering module is within a preset range. The filtering module performs common-mode filtering and differential-mode filtering on the received signal, and outputs the filtered signal through the anti-backlash interference module, the first output terminal, and the second output terminal. The anti-backlash interference module is used to prevent the backslash interference of external signals.

[0006] The inventor of the present invention believes that the above technical solution is only applicable to the suppression of electromagnetic interference between various systems of electric vehicles and is not applicable to the suppression of electromagnetic interference of driving recorders.

[0007] The patent with publication number CN108039815A discloses an electromagnetic interference suppression circuit and its operation method, including a DC bus. The DC bus is connected to the DC input terminal of an inverter after passing through magnetic rings respectively used for suppressing common-mode interference and differential-mode interference. The AC bridge output of the inverter is respectively connected to the three-phase outgoing lines of the bridge through inductors and circuit breaker QF1. The three-phase outgoing lines of the bridge are respectively connected to three-phase outgoing terminals A, B, and C after passing through a common-mode inductor L11, a differential-mode inductor L12, and a magnetic ring, and high-frequency interference in each frequency band is suppressed through the magnetic ring and inductors.

[0008] The inventor believes that the above technical solution, through the mutual cooperation of the common-mode inductor and the differential-mode inductor, adds a high-frequency suppression device at the source of the high-frequency interference source, that is, by adding a common-mode suppression magnetic ring to the filter inductor of the inverter, to reduce the electromagnetic interference of the inverter, which is applicable to solving the electromagnetic interference of grid equipment and is not applicable to the electromagnetic interference suppression of a dash cam. Summary of the Invention

[0009] In order to overcome the deficiencies of the prior art, the object of the present invention is to provide an electromagnetic interference suppression circuit for a dash cam to solve the problem of electromagnetic interference suppression in the PCB design of dash cam products.

[0010] To achieve the above object, the technical solution adopted by the present invention is: to provide an electromagnetic interference suppression circuit for a dash cam, including

[0011] a spread spectrum clock generator, which attenuates the peak of unnecessary electromagnetic interference by periodically slightly modulating the oscillation frequency using an internal modulator;

[0012] an oscillator, which is used to calibrate the crystal frequency input to the spread spectrum clock generator;

[0013] a spread spectrum frequency adjustment unit, which is used to adjust the crystal frequency input to the spread spectrum clock generator;

[0014] a spread spectrum frequency output unit, which is used to adjust the spread spectrum frequency output by the spread spectrum clock generator and then output it to the system clock of the main chip of the dash cam;

[0015] a power supply unit, which is used to provide a working power supply for the spread spectrum clock generator.

[0016] Further, the oscillator includes a crystal oscillator, a first capacitor, and a second capacitor. One end of the crystal oscillator and one end of the first capacitor are respectively connected to pin 1 of the spread spectrum clock generator. The other end of the crystal oscillator and one end of the second capacitor are respectively connected to pin 2 of the spread spectrum clock generator. The other ends of the first capacitor and the second capacitor are connected together and then grounded.

[0017] Further, the spread spectrum frequency adjustment unit includes a first resistor, a second resistor, a third resistor, a fourth resistor, and a fifth resistor. One end of the first resistor and one end of the second resistor are respectively connected to pin 3 of the spread spectrum clock generator. The other end of the first resistor is connected to the chip power supply 3.3V. The other end of the second resistor is connected to pin 4 of the spread spectrum clock generator and then grounded. One end of the fourth resistor and one end of the fifth resistor are respectively connected to pin 7 of the spread spectrum clock generator. The other end of the fourth resistor is connected to the circuit power supply VCC. One end of the third resistor is connected to pin 6 of the spread spectrum clock generator. The other end of the third resistor is connected to the fifth resistor and then grounded.

[0018] Further, the spread spectrum frequency output unit includes a sixth resistor and a seventh resistor. One end of the seventh resistor is connected to pin 5 of the spread spectrum clock generator. The other end of the seventh resistor is respectively connected to the main chip system clock of the driving recorder and one end of the sixth resistor. The other end of the sixth resistor is grounded.

[0019] Further, the power supply unit includes an eighth resistor and a third capacitor. One end of the eighth resistor and one end of the third capacitor are respectively connected to pin 8 of the spread spectrum clock generator. The other end of the eighth resistor is connected to the circuit power supply VCC. The other end of the third capacitor is grounded.

[0020] Further, the model of the spread spectrum clock generator is SSDCI1108AF.

[0021] Further, pin 1 of the spread spectrum clock generator is XIN / CXIN, and pin 1 is the input end of the internal oscillation circuit of the spread spectrum clock generator; pin 2 of the spread spectrum clock generator is XOUT, and pin 2 is the output end of the internal oscillation circuit of the spread spectrum clock generator.

[0022] Further, pin 3 of the spread spectrum clock generator is FREQ0, and pin 4 of the spread spectrum clock generator is FREQ1. Pins 3 and 4 are used to select to output high level or low level according to the input crystal frequency range; pin 7 of the spread spectrum clock generator is ADS, and pin 7 is used to set the input crystal frequency range.

[0023] Further, pin 5 of the spread spectrum clock generator is Mod Out, and this pin 5 is used for the spread spectrum frequency output of the spread spectrum clock generator.

[0024] Further, the second resistor is set to NC, the fourth resistor is set to NC, and the sixth resistor is set to NC.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows. The electromagnetic interference suppression circuit of the driving recorder provided by the present invention attenuates the peaks of unnecessary electromagnetic interference by using the internal modulator of the spread spectrum clock generator to periodically and slightly modulate the oscillation frequency through frequency modulation; calibrates the crystal frequency input to the spread spectrum clock generator through the oscillator, the spread spectrum frequency adjustment unit adjusts the crystal frequency input to the spread spectrum clock generator, the spread spectrum frequency output unit adjusts the spread spectrum frequency output by the spread spectrum clock generator and then outputs it to the system clock of the main chip of the driving recorder, and the power supply unit provides a working power supply for the spread spectrum clock generator, without the need to determine the circuit parameters of the electromagnetic interference reduction circuit through a trial-and-error method or calculation, thus solving the problem of electromagnetic interference suppression in the PCB design of driving recorder products. Description of the Drawings

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can also obtain other drawings based on these drawings without creative efforts.

[0027] Figure 1 It is a functional block diagram of the electromagnetic interference suppression circuit of the driving recorder provided by the embodiment of the present invention.

[0028] Figure 2 It is a circuit schematic diagram of the electromagnetic interference suppression circuit of the driving recorder provided by the embodiment of the present invention.

[0029] Figure 3 It is a schematic diagram of the generation principle of electromagnetic interference of the electromagnetic interference suppression circuit of the driving recorder provided by the embodiment of the present invention.

[0030] Figure 4 It is a schematic diagram of the center spread spectrum frequency of the system clock of the main chip of the driving recorder after modulation of the electromagnetic interference suppression circuit provided by the embodiment of the present invention.

[0031] Figure 5 It is a schematic diagram of the comparison of electromagnetic interference before and after circuit processing of the electromagnetic interference suppression circuit of the driving recorder provided by the embodiment of the present invention.

[0032] Figure 6It is the schematic diagram of the center frequency spread spectrum method of the electromagnetic interference suppression circuit of the driving recorder provided by the embodiment of the present invention.

[0033] Figure 7 It is the schematic diagram of the corresponding relationship between the spectrum output by the electromagnetic interference suppression circuit of the driving recorder provided by the embodiment of the present invention and the modulation domain.

[0034] Figure 8 It is the schematic diagram of the electromagnetic interference test effect of the electromagnetic interference suppression circuit of the driving recorder provided by the embodiment of the present invention.

[0035] The marks in the above figures are: U1, spread spectrum clock generator; 2, oscillator; 3, spread spectrum frequency adjustment unit; 4, power supply unit; 5, spread spectrum frequency output unit. Specific embodiments

[0036] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0037] In the accompanying drawings of this embodiment, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", etc. indicating the orientation or positional relationship, they are based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the accompanying drawings are only for illustrative purposes and cannot be understood as a limitation of this patent. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0038] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] As Figures 1 to 8 shown, it is a preferred embodiment provided by the present invention.

[0040] Referring to Figure 1, the electromagnetic interference suppression circuit of the driving recorder provided in this embodiment includes a spread spectrum clock generator U1. The spread spectrum clock generator U1 attenuates the peaks of unnecessary electromagnetic interference by periodically slightly modulating the oscillation frequency using an internal modulator; an oscillator 2 for calibrating the crystal frequency input to the spread spectrum clock generator U1; a spread spectrum frequency adjustment unit 3 for adjusting the crystal frequency input to the spread spectrum clock generator U1; a spread spectrum frequency output unit 5 for adjusting and outputting the spread spectrum frequency output by the spread spectrum clock generator U1 to the system clock of the main chip of the driving recorder; and a power supply unit 4 for providing a working power supply for the spread spectrum clock generator U1.

[0041] The electromagnetic interference suppression circuit of the driving recorder provided by the above technical solution attenuates the peaks of unnecessary electromagnetic interference by periodically slightly modulating the oscillation frequency using the internal modulator of the spread spectrum clock generator U1 through a frequency modulation method; calibrates the crystal frequency input to the spread spectrum clock generator U1 through the oscillator 2, adjusts the crystal frequency input to the spread spectrum clock generator U1 through the spread spectrum frequency adjustment unit 3, adjusts and outputs the spread spectrum frequency output by the spread spectrum clock generator U1 to the system clock of the main chip of the driving recorder through the spread spectrum frequency output unit 5, and the power supply unit 4 provides a working power supply for the spread spectrum clock generator U1, without the need to determine the circuit parameters of the electromagnetic interference reduction circuit through a trial-and-error method or calculation, thus solving the problem of electromagnetic interference suppression in the PCB design of driving recorder products.

[0042] Specifically, referring to Figure 2 , pin 1 of the spread spectrum clock generator U1 is XIN / CXIN, and pin 1 is the input end of the internal oscillation circuit of the spread spectrum clock generator U1; pin 2 of the spread spectrum clock generator U1 is XOUT, and pin 2 is the output end of the internal oscillation circuit of the spread spectrum clock generator; pin 3 of the spread spectrum clock generator U1 is FREQ0, pin 4 of the spread spectrum clock generator U1 is FREQ1, and pins 3 and 4 are used to select to output a high level or a low level according to the input crystal frequency range; pin 7 of the spread spectrum clock generator U1 is ADS, and pin 7 is used to set the input crystal frequency range; pin 5 of the spread spectrum clock generator U1 is Mod Out, and pin 5 is used for the spread spectrum frequency output of the spread spectrum clock generator U1; pin 4 of the spread spectrum clock generator U1 is GND, and pin 4 is used for grounding; pin 8 of the spread spectrum clock generator U1 is VDD, and pin 8 is used to connect to the working power supply.

[0043] As an implementation manner of this embodiment, referring to Figure 2, the oscillator 2 includes a crystal oscillator Y1, a first capacitor C1, and a second capacitor C2. One end of the crystal oscillator Y1 and one end of the first capacitor C1 are respectively connected to pin 1 of the spread spectrum clock generator U1. The other end of the crystal oscillator Y1 and one end of the second capacitor C2 are respectively connected to pin 2 of the spread spectrum clock generator U1. The other ends of the first capacitor C1 and the second capacitor C2 are connected together and then grounded. In this way, pin 1 and pin 2 together with the crystal oscillator Y1 form the oscillator 2. The first capacitor C1 and the second capacitor C2 are compensation capacitors for the crystal, thereby realizing the calibration of the crystal frequency input to the spread spectrum clock generator U1.

[0044] As an implementation manner of this embodiment, referring to Figure 2 , the spread spectrum frequency adjustment unit 3 includes a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, and a fifth resistor R5. One end of the first resistor R1 and one end of the second resistor R2 are respectively connected to pin 3 of the spread spectrum clock generator U1. The other end of the first resistor R1 is connected to the chip power supply 3.3V. The other end of the second resistor R2 is connected to pin 4 of the spread spectrum clock generator U1 and then grounded. One end of the fourth resistor R4 and one end of the fifth resistor R5 are respectively connected to pin 7 of the spread spectrum clock generator U1. The other end of the fourth resistor R4 is connected to the circuit power supply VCC. Pin 6 of the spread spectrum clock generator U1 is connected to one end of the third resistor R3. The other end of the third resistor R3 is connected to the fifth resistor R5 and then grounded. In this way, the adjustment of the crystal frequency input to the spread spectrum clock generator U1 is realized. The corresponding relationship between the input crystal frequency after adjustment and the outputs of FREQ0 and FREQ1 is shown in the following table:

[0045] FREQ0 FREQ1 Input frequency range H (High level) H (High level) 10 MHz to 30 MHz L (Low level) H (High level) 66 MHz to 134 MHz H (High level) L (Low level) 20 MHz to 67 MHz L (Low level) L (Low level) 40 MHz to 80 MHz

[0046] As an implementation manner of this embodiment, referring to Figure 2 , the spread spectrum frequency output unit 5 includes a sixth resistor R6 and a seventh resistor R7. Pin 5 of the spread spectrum clock generator U1 is connected to one end of the seventh resistor R7. The other end of the seventh resistor R7 is respectively connected to the system clock of the main chip of the driving recorder and one end of the sixth resistor R6. The other end of the sixth resistor R6 is grounded. In this way, the spread spectrum frequency output unit 5 adjusts the spread spectrum frequency output by the spread spectrum clock generator U1 and then outputs it to the system clock of the main chip of the driving recorder.

[0047] As an implementation manner of this embodiment, referring to Figure 2 , the power supply unit 4 includes an eighth resistor R8 and a third capacitor C3. One end of the eighth resistor R8 and one end of the third capacitor C3 are respectively connected to pin 8 of the spread spectrum clock generator U1. The other end of the eighth resistor R8 is connected to the circuit power supply VCC. The other end of the third capacitor C3 is grounded. In this way, the power supply unit 4 provides a working power supply for the spread spectrum clock generator U1.

[0048] Preferably, the model of the spread spectrum clock generator U1 is SSDCI1108AF.

[0049] Preferably, the second resistor R2 is set to NC, the fourth resistor R4 is set to NC, and the sixth resistor R6 is set to NC.

[0050] The principle of electromagnetic interference suppression of the electromagnetic interference suppression circuit is as follows:

[0051] Since the fundamental cause of electromagnetic interference lies in that the rectangular wave has many harmonic components, therefore, from the mechanism principle of electromagnetic interference formation, the energy of these harmonic components is suppressed to achieve the purpose of electromagnetic interference suppression.

[0052] Refer to Figure 3 , in the figure, EMI represents electromagnetic interference, F represents the center frequency of spread spectrum, and T represents the digital signal; the repeated digital signal T generates electromagnetic interference through the energy accumulation of the center frequency F of spread spectrum. The ideal square wave generates electromagnetic interference through energy accumulation at odd harmonics (3x, 5x,...). The real square wave generates electromagnetic interference at all harmonics (2x, 3x, 4x, 5x).

[0053] Refer to Figure 4 , in the figure, EMI represents electromagnetic interference, S1 represents the energy distribution curve after modulation, and S2 represents the energy distribution curve before modulation; the system clock of the main chip of the driving recorder is modulated through the electromagnetic interference suppression circuit, the clock is controlled to change periodically, and the period change steps are taken at a certain time. So that the energy is distributed over a wider bandwidth (the peak EMI is reduced). The calculation formula is as follows:

[0054] F = 1 / T = 24 MHz

[0055] F1 = 1 / (T + ΔT1) = 24.997 MHz

[0056] F2 = 1 / (T + ΔT2) = 24.994 MHz

[0057] …

[0058] Fn = 1 / (T + ΔT n ) = 24.994 MHz

[0059] Among them, F represents the center frequency of spread spectrum, T represents the digital signal, n represents a natural number, ΔT1, ΔT2... ΔT n represents the difference value of 30 KHz, F1 represents the frequency of spread spectrum reduced by 30 KHz based on F, F2 represents the frequency of spread spectrum reduced by 30 KHz based on F1, and so on, Fn represents the frequency of spread spectrum reduced by 30 KHz based on F(n - 1).

[0060] Refer to Figure 5, in the figure, EMI represents electromagnetic interference, S1 represents the EMI energy distribution curve after being processed by the electromagnetic interference suppression circuit, and S2 represents the EMI energy distribution curve before being processed by the electromagnetic interference suppression circuit; the reduction of electromagnetic interference is related to the modulation bandwidth, and the modulation bandwidth is a% of the center frequency (a = ±1 - ±5). The larger the modulation bandwidth, the wider the EMI energy distribution curve of S1, and the smaller the EMI energy distribution. This fundamentally and effectively reduces the impact of electromagnetic interference on the entire vehicle recorder product.

[0061] Refer to Figure 6 , in the figure, Fmax represents the maximum frequency of frequency spreading, Fcenter represents the center frequency of frequency spreading, and Fmin represents the minimum frequency of frequency spreading; as an implementation manner of this embodiment, the modulation frequency of the 24 MHz system clock is 30 kHz, and the center frequency spreading method of + / -1.25% is used. The change of the modulation frequency is as Figure 6 shown by the curve S0 in the figure. The modulation frequency is selected to be greater than 20 kHz to stay above the audio band and small enough (<120 KHz) to avoid the phase-locked loop tracking problem in the main chip of the vehicle recorder. The design of the present invention is not to keep a constant frequency, but to modulate the system clock to reduce the peak EMI (electromagnetic interference) output power at its source, that is, the system clock. The modulation frequency is selected to be greater than 30 kHz to stay above the audio band and slow enough to avoid system timing and tracking problems (usually much lower than 90 kHz). The correspondence between the output spectrum and the modulation domain is as Figure 7 shown in the figure, where Fmax represents the maximum frequency of frequency spreading, Fcenter represents the center frequency of frequency spreading, Fmin represents the minimum frequency of frequency spreading, S0 represents the modulation frequency change curve, S1 represents the EMI energy distribution curve after being processed by the electromagnetic interference suppression circuit, and S2 represents the EMI energy distribution curve before being processed by the electromagnetic interference suppression circuit.

[0062] As an implementation manner of this embodiment, the EMI (electromagnetic interference) test effect is as Figure 8 shown in the figure. F represents the center frequency of frequency spreading, F = 24 MHz, S1 represents the EMI energy distribution curve after being processed by the electromagnetic interference suppression circuit, and S2 represents the EMI energy distribution curve before being processed by the electromagnetic interference suppression circuit. Compared with S2, the EMI peak of S1 is reduced by 12 dB, indicating that the electromagnetic interference is suppressed in the test result.

[0063] Since the present invention achieves the purpose of suppressing electromagnetic interference through frequency modulation, there is no need for high requirements on the PCB design of the dash cam product; electromagnetic interference can be suppressed for any frequency between 10 MHz and 130 MHz through the electromagnetic interference suppression circuit and pass the electromagnetic interference test, thereby effectively suppressing the electromagnetic interference of the dash cam product.

[0064] The embodiments of the present invention have been described in detail above, but the creation of the present invention is not limited to these embodiments. Those skilled in the art can make many equivalent variations or substitutions without departing from the spirit of the present invention, and these equivalent variations or substitutions are all included in the protection scope defined by the claims of this application.

Claims

1. The electromagnetic interference suppression circuit of a driving recorder, characterized in that, including a spread spectrum clock generator that attenuates the peaks of unnecessary electromagnetic interference by periodically slightly modulating the oscillation frequency using an internal modulator; an oscillator for calibrating the crystal frequency input to the spread spectrum clock generator; a spread spectrum frequency adjustment unit for adjusting the crystal frequency input to the spread spectrum clock generator; a spread spectrum frequency output unit for adjusting the spread spectrum frequency output by the spread spectrum clock generator and outputting it to the system clock of the dash cam main chip; a power supply unit for providing a working power supply for the spread spectrum clock generator; the oscillator includes a crystal oscillator, a first capacitor, and a second capacitor. One end of the crystal oscillator and one end of the first capacitor are respectively connected to pin 1 of the spread spectrum clock generator. The other end of the crystal oscillator and one end of the second capacitor are respectively connected to pin 2 of the spread spectrum clock generator. The other ends of the first capacitor and the second capacitor are connected together and then grounded; the spread spectrum frequency adjustment unit includes a first resistor, a second resistor, a third resistor, a fourth resistor, and a fifth resistor. One end of the first resistor and one end of the second resistor are respectively connected to pin 3 of the spread spectrum clock generator. The other end of the first resistor is connected to the chip power supply 3.3V. The other end of the second resistor is connected to pin 4 of the spread spectrum clock generator and then grounded. One end of the fourth resistor and one end of the fifth resistor are respectively connected to pin 7 of the spread spectrum clock generator. The other end of the fourth resistor is connected to the circuit power supply VCC. Pin 6 of the spread spectrum clock generator is connected to one end of the third resistor. The other end of the third resistor is connected to the fifth resistor and then grounded; the spread spectrum frequency output unit includes a sixth resistor and a seventh resistor. One end of the seventh resistor is connected to pin 5 of the spread spectrum clock generator. The other end of the seventh resistor is respectively connected to the system clock of the dash cam main chip and one end of the sixth resistor. The other end of the sixth resistor is grounded; 2. The electromagnetic interference suppression circuit of the driving recorder according to claim 1, wherein, the power supply unit includes an eighth resistor and a third capacitor. One end of the eighth resistor and one end of the third capacitor are respectively connected to pin 8 of the spread spectrum clock generator. The other end of the eighth resistor is connected to the circuit power supply VCC. The other end of the third capacitor is grounded; 3. The electromagnetic interference suppression circuit of the driving recorder according to any one of claims 1 or 2, characterized in that the model of the spread spectrum clock generator is SSDCI1108AF; 4. The electromagnetic interference suppression circuit of the driving recorder according to claim 1, characterized in that, pin 1 of the spread spectrum clock generator is XIN / CXIN, and pin 1 is the input end of the internal oscillation circuit of the spread spectrum clock generator; pin 2 of the spread spectrum clock generator is XOUT, and pin 2 is the output end of the internal oscillation circuit of the spread spectrum clock generator; 5. The electromagnetic interference suppression circuit of the driving recorder according to claim 1, wherein pin 3 of the spread spectrum clock generator is FREQ0, and pin 4 of the spread spectrum clock generator is FREQ1. Pins 3 and 4 are used to select to output a high level or a low level according to the input crystal frequency range; pin 7 of the spread spectrum clock generator is ADS, and pin 7 is used to set the input crystal frequency range.

6. The electromagnetic interference suppression circuit of the driving recorder according to claim 1, characterized in that, Pin 5 of the spread spectrum clock generator is Mod Out, and Pin 5 is used for the spread spectrum frequency output of the spread spectrum clock generator.

7. The electromagnetic interference suppression circuit of the driving recorder according to claim 1, characterized in that, The second resistor is set to NC, the fourth resistor is set to NC, and the sixth resistor is set to NC.

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