Spectrum spread modulation system and method applied to PWM (Pulse Width Modulation)

Abstract

The invention relates to a spectrum spreading modulation system and method applied to PWM, and belongs to the technical field of electronic information. By adopting the system and the method provided by the invention, a duration counter module outputs a period cycle control signal according to a spread spectrum period control signal, a spread spectrum range control signal and a CLK signal; the periodic cycle generator module generates an N-bit control bit according to the periodic cycle control signal; and the built-in oscillator module adjusts the frequency range of the output CLK signal by using the N-bit control bit, so that the purposes of expanding the frequency spectrum distribution of PWM and reducing EMI interference are achieved. The method is convenient to implement, the EMI interference problem is solved, meanwhile, the EMI design of the whole chip is simplified, and therefore the overall application cost of adopting a spectrum spreading modulation scheme in a PWM control application scene is reduced.

Description

Technical Field

[0001] The present invention relates to the field of electronic information technology, in particular to the field of PWM signal control technology, and specifically refers to a spectrum spread modulation system and method applied to PWM. Background Art

[0002] At present, EMI interference is a problem of great concern in electronic devices, and the fixed-period PMW electromagnetic interference generated by the fixed oscillation frequency inside the chip is relatively common, especially in the design of some LED driver chip solutions.

[0003] Therefore, how to provide an anti-interference design for a fixed oscillation frequency inside a chip to solve the EMI interference problem has become an urgent problem to be solved in this field. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and to provide an easy-to-implement digital method for frequency expansion. The present invention digitally periodically controls the frequency range of the built-in oscillator so that the PWM frequency generated by it fluctuates periodically within a certain range, thereby dispersing the spectrum distribution of the PWM waveform and achieving the purpose of reducing EMI interference.

[0005] In order to achieve the above-mentioned purpose, the spectrum spread modulation system applied to PWM of the present invention has the following constitution:

[0006] The spectrum expansion modulation system applied to PWM includes: a built-in oscillator module, a periodic cycle generator module and a periodic cycle generator module.

[0007] Among them, the built-in oscillator module is used to adjust the frequency range of the output CLK signal using the N bit control bit;

[0008] The cycle generator module is used to generate the N bit control bit according to the spread spectrum range control signal and the CLK signal and based on the state cycle jump principle;

[0009] The cycle generator module is used to output a cycle control signal according to the spread spectrum cycle control signal, the spread spectrum range control signal and the CLK signal, and the cycle control signal is used to control the duration of a single cycle of the cycle generator module; the frequency range of the output CLK signal of the built-in oscillator module is modulated by modulating the spread spectrum cycle control signal and the frequency range control signal to expand the spectrum distribution of PWM.

[0010] In the spectrum spread modulation system applied to PWM, the built-in oscillator module is an RC oscillation circuit including resistors and capacitors or a constant current source oscillation circuit including a constant current source and a capacitor; accordingly, the frequency range of the output CLK signal is adjusted by adjusting one or both of the resistance value, the capacitance value or the constant current source current value using the N bit control bit.

[0011] In the spectrum spread modulation system applied to PWM, the cycle generator module is a digital control logic STEP cycle generator, which is used to generate the N bit control bit by using increasing and decreasing cycle cycles or disordered cycle cycles.

[0012] In the spectrum spread modulation system applied to PWM, the random periodic cycle is generated by adopting a pseudo-random number method.

[0013] In the spectrum spread modulation system applied to PWM, the duration counter module is a single-STEP duration counter.

[0014] The present invention also provides a spectrum spread modulation method applied to PWM, the method comprising:

[0015] The duration counter module outputs a period cycle control signal according to the modulated spread spectrum period control signal, the spread spectrum range control signal and the CLK signal;

[0016] The cycle generator module generates the N bit control bit according to the spread spectrum range control signal, the CLK signal and the cycle control signal, and based on the state cycle jump principle. The cycle control signal is used to control the duration of a single cycle of the cycle generator module.

[0017] The built-in oscillator module uses the N bit control bit to adjust the frequency range of the output CLK signal and expand the spectrum distribution of PWM.

[0018] In the spectrum spread modulation method applied to PWM, the built-in oscillator module is an RC oscillation circuit including a resistor and a capacitor or a constant current source oscillation circuit including a constant current source and a capacitor;

[0019] The built-in oscillator module uses the N bit control bit to adjust the frequency range of the output CLK signal and expand the spectrum distribution of PWM, specifically,

[0020] The frequency range of the output CLK signal is adjusted by adjusting one or both of the resistance value, the capacitance value or the constant current source current value using the N bit control bit, thereby expanding the spectrum distribution of the PWM.

[0021] In the spectrum spread modulation method applied to PWM, the cycle generator module is a digital control logic STEP cycle generator.

[0022] The N bit control bit is generated based on the state cycle jump principle, specifically, the N bit control bit is generated by using an increasing and decreasing cycle cycle or a random cycle cycle.

[0023] In the spectrum spread modulation method applied to PWM, the random periodic cycle is generated by adopting a pseudo-random number method.

[0024] In the spectrum spread modulation method applied to PWM, the duration counter module is a single-STEP duration counter.

[0025] The spectrum spread modulation system and method for PWM of the invention is adopted, which outputs a periodic cycle control signal according to the spread spectrum period control signal, the spread spectrum range control signal and the CLK signal through the duration counter module; the periodic cycle generator module generates N bit control bits according to the periodic cycle control signal; and then the built-in oscillator module uses the N bit control bits to adjust the frequency range of the output CLK signal to achieve the purpose of expanding the spectrum distribution of PWM and reducing EMI interference. The method of the invention is easy to implement, and while solving the EMI interference problem, it is also conducive to simplifying the EMI design of the entire chip, thereby reducing the overall application cost of the spectrum spread modulation scheme in the PWM control application scenario. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram of a spectrum spread modulation system applied to PWM of the present invention;

[0027] Figure 2 A schematic diagram of the state transition of the periodic cycle generator module in the present invention using an increasing and decreasing periodic cycle to generate an N-bit control bit;

[0028] Figure 3 A schematic diagram of the state transition of the cycle generator module in the present invention using an out-of-order cycle to generate an N-bit control bit;

[0029] Figure 4 A schematic diagram showing the comparison between the spectrum expanded by the method of the present invention and the original spectrum;

[0030] Figure 5 The figure is a flow chart of the spectrum spread modulation method applied to PWM of the present invention. DETAILED DESCRIPTION

[0031] In order to more clearly understand the technical content of the present invention, the following embodiments are given in detail.

[0032] See also Figure 1 FIG. 1 is a schematic diagram of the structure of the spectrum spread modulation system applied to PWM of the present invention.

[0033] The spectrum expansion modulation system applied to PWM includes: a built-in oscillator module, a periodic cycle generator module and a periodic cycle generator module.

[0034] Among them, the built-in oscillator module is used to adjust the frequency range of the output CLK signal using the N bit control bit;

[0035] The cycle generator module is used to generate the N bit control bit according to the spread spectrum range control signal and the CLK signal and based on the state cycle jump principle;

[0036] The cycle generator module is used to output a cycle control signal according to the spread spectrum cycle control signal, the spread spectrum range control signal and the CLK signal, and the cycle control signal is used to control the duration of a single cycle of the cycle generator module; the frequency range of the output CLK signal of the built-in oscillator module is modulated by modulating the spread spectrum cycle control signal and the frequency range control signal to expand the spectrum distribution of PWM.

[0037] In the spectrum spread modulation system applied to PWM, the built-in oscillator module is an RC oscillation circuit including resistors and capacitors or a constant current source oscillation circuit including a constant current source and a capacitor; accordingly, the frequency range of the output CLK signal is adjusted by adjusting one or both of the resistance value, the capacitance value or the constant current source current value using the N bit control bit.

[0038] In the spectrum spread modulation system applied to PWM, the cycle generator module is a digital control logic STEP cycle generator, which is used to adopt Figure 2 As shown in the increasing and decreasing cycle cycle or as Figure 3 The out-of-order cycles shown generate the N bits of control bits.

[0039] In the spectrum spread modulation system applied to PWM, the random periodic cycle is generated by adopting a pseudo-random number method.

[0040] In the spectrum spread modulation system applied to PWM, the duration counter module is a single-STEP duration counter.

[0041] The present invention also provides a spectrum spread modulation method applied to PWM, the method is as follows Figure 5 As shown, including:

[0042] The duration counter module outputs a period cycle control signal according to the modulated spread spectrum period control signal, the spread spectrum range control signal and the CLK signal;

[0043] The cycle generator module generates the N bit control bit according to the spread spectrum range control signal, the CLK signal and the cycle control signal, and based on the state cycle jump principle. The cycle control signal is used to control the duration of a single cycle of the cycle generator module.

[0044] The built-in oscillator module uses the N bit control bit to adjust the frequency range of the output CLK signal and expand the spectrum distribution of PWM.

[0045] In the spectrum spread modulation method applied to PWM, the built-in oscillator module is an RC oscillation circuit including a resistor and a capacitor or a constant current source oscillation circuit including a constant current source and a capacitor;

[0046] The built-in oscillator module uses the N bit control bit to adjust the frequency range of the output CLK signal and expand the spectrum distribution of PWM, specifically,

[0047] The frequency range of the output CLK signal is adjusted by adjusting one or both of the resistance value, the capacitance value or the constant current source current value using the N bit control bit, thereby expanding the spectrum distribution of the PWM.

[0048] In the spectrum spread modulation method applied to PWM, the cycle generator module is a digital control logic STEP cycle generator.

[0049] The N bit control bit is generated based on the state cycle jump principle, specifically, the N bit control bit is generated by using an increasing and decreasing cycle cycle or a random cycle cycle.

[0050] In the spectrum spread modulation method applied to PWM, the random periodic cycle is generated by adopting a pseudo-random number method.

[0051] In the spectrum spread modulation method applied to PWM, the duration counter module is a single-STEP duration counter.

[0052] In practical applications, the present invention provides a simple digital implementation method for frequency expansion. The invention periodically controls the frequency range of the built-in oscillator by digital, so that the PWM frequency generated by it fluctuates periodically within a certain range, thereby dispersing the spectrum distribution of the PWM waveform and achieving the purpose of reducing EMI interference.

[0053] The specific implementation scheme of the present invention includes three modules. The oscillator structure of the built-in oscillator module can be implemented by resistor R and capacitor C, or by constant current source and capacitor C. The module uses N bit control bits to adjust the frequency range of the output CLK. The N bit frequency modulation method can be implemented by adjusting the value of resistor R, adjusting the value of capacitor C, or adjusting the current value of the constant current source. The digital control logic STEP cycle generator is used to periodically generate N bit control bits, which can be generated by increasing and decreasing cycle cycles or by random order (pseudo-random number method) cycle cycles. Taking a 4-bit control bit as an example, the state jump diagram generated by the increasing and decreasing cycle cycles is shown in the figure. Figure 2 As shown, the state jump diagram generated by random order (pseudo-random number method) is as follows Figure 3 As shown. Other bit widths can also be implemented using similar state loop jump principles. The single step duration counter module is used to control how long the digital control logic step cycle generator changes. The duration of a single step can be controlled by the spread spectrum cycle control and frequency range control signals.

[0054] The clock signal CLK output by the built-in oscillator module is directly used as the clock input of the digital control logic STEP cycle generator and the single STEP duration counter module. Designers can use channel modulation spread spectrum period control and frequency range control signals to modulate the frequency output of the built-in oscillator module, thereby completing the frequency control of the entire oscillator. In actual PWM control application scenarios, as long as the duty cycle (the ratio of pulse width to period) remains unchanged, changes in the period (that is, the inverse of the frequency) do not affect the results. However, changes in the period will cause changes in the frequency. If the period fluctuates in a fixed pattern, the frequency will fluctuate in a fixed pattern, thereby dispersing the distribution of the spectrum, which is beneficial to reducing EMI interference with concentrated frequencies, such as Figure 4 As shown, the spectrum before expansion is concentrated at one point, while the spectrum after expansion using the method of the present invention is dispersed around the original spectrum, and the amplitude is also reduced. The purpose of dispersing the output signal spectrum is thereby achieved. This effectively reduces the EMI interference of the frequency in the entire chip concentration, and is very suitable for application scenarios of PWM control. Among them, the digital cycle control period and the modulatable range of the oscillator are the key design parameters that determine the dispersion of the spectrum, and the designer can flexibly design the parameters according to the actual application scenario.

[0055] The spectrum spread modulation system and method applied to PWM of the invention is adopted, which outputs a periodic cycle control signal according to the spread spectrum period control signal, the spread spectrum range control signal and the CLK signal through the duration counter module; the periodic cycle generator module generates N bit control bits according to the periodic cycle control signal; and then the built-in oscillator module uses the N bit control bits to adjust the frequency range of the output CLK signal to achieve the purpose of expanding the spectrum distribution of PWM and reducing EMI interference. The method of the invention is easy to implement, and while solving the EMI interference problem, it is also conducive to simplifying the EMI design of the entire chip in the application of PWM control scenarios, thereby reducing the overall application cost of the spectrum spread modulation scheme in the PWM control application scenario.

[0056] In this specification, the present invention has been described with reference to specific embodiments thereof. However, it is apparent that various modifications and variations may be made without departing from the spirit and scope of the present invention. Therefore, the specification and drawings should be regarded as illustrative rather than restrictive.

Claims

1. A spectrum spread modulation system applied to PWM, characterized in that: include: Built-in oscillator module, used to adjust the frequency range of the output CLK signal using N bit control bits; A cycle generator module, used for generating the N bit control bit according to the spread spectrum range control signal and the CLK signal and based on the state cycle jump principle; A duration counter module, used for outputting a periodic cycle control signal according to the spread spectrum period control signal, the spread spectrum range control signal and the CLK signal, wherein the periodic cycle control signal is used for controlling the duration of a single cycle of the periodic cycle generator module; The frequency range of the output CLK signal of the built-in oscillator module is modulated by modulating the spread spectrum period control signal and the frequency range control signal, thereby expanding the spectrum distribution of PWM.

2. The spectrum spread modulation system applied to PWM according to claim 1, characterized in that: The built-in oscillator module is an RC oscillation circuit including resistors and capacitors or a constant current source oscillation circuit including a constant current source and a capacitor; accordingly, the frequency range of the output CLK signal is adjusted by adjusting one or both of the resistance value, the capacitance value or the constant current source current value using the N bit control bit.

3. The spectrum spread modulation system applied to PWM according to claim 2, characterized in that: The cycle generator module is a digital control logic STEP cycle generator, which is used to generate the N bit control bit by using an increasing or decreasing cycle or a disordered cycle.

4. The spectrum spread modulation system applied to PWM according to claim 3, characterized in that: The random cycle is generated by using a pseudo-random number method.

5. The spectrum spread modulation system applied to PWM according to claim 3, characterized in that: The duration counter module is a single-STEP duration counter.

6. A spectrum spread modulation method applied to PWM, characterized in that: include: The duration counter module outputs a period cycle control signal according to the modulated spread spectrum period control signal, the spread spectrum range control signal and the CLK signal; The cycle generator module generates N bit control bits according to the spread spectrum control signal, the CLK signal and the cycle control signal, and based on the state cycle jump principle. The cycle control signal is used to control the duration of a single cycle of the cycle generator module. The built-in oscillator module uses the N bit control bit to adjust the frequency range of the output CLK signal and expand the spectrum distribution of PWM.

7. The spectrum spread modulation method applied to PWM according to claim 6, characterized in that: The built-in oscillator module is an RC oscillation circuit including a resistor and a capacitor or a constant current source oscillation circuit including a constant current source and a capacitor; The built-in oscillator module uses the N bit control bit to adjust the frequency range of the output CLK signal and expand the spectrum distribution of PWM, specifically, The frequency range of the output CLK signal is adjusted by adjusting one or both of the resistance value, the capacitance value or the constant current source current value using the N bit control bit, thereby expanding the spectrum distribution of the PWM.

8. The spectrum spread modulation method applied to PWM according to claim 7, characterized in that: The cycle generator module is a digital control logic STEP cycle generator. The N bit control bit is generated based on the state cycle jump principle, specifically, the N bit control bit is generated by using an increasing and decreasing cycle cycle or a random cycle cycle.

9. The spectrum spread modulation method applied to PWM according to claim 8, characterized in that: The random cycle is generated by using a pseudo-random number method.

10. The spectrum spread modulation method applied to PWM according to claim 8, characterized in that: The duration counter module is a single-STEP duration counter.

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