TECHNICAL FIELD

Embodiments of the present disclosure relate to a clock spread spectrum circuit, an electronic equipment, and a clock spread spectrum method.

BACKGROUND

Electromagnetic interference (EMI) refers to the influence of the circuit system on the surrounding circuit system through conduction or radiation. Electromagnetic interference may degrade the circuit performance, and may even cause the failure of the entire circuit system. The clock signal is usually the signal with the highest frequency and steepest edge in the circuit system, and most electromagnetic interference problems are related to high frequency clock signals. Methods for reducing electromagnetic interference include shielding, filtering, isolation, signal edge control, layout of the printed circuit board (PCB) such as providing a power layer and a ground (GND) layer in the PCB, etc. However, these methods have high cost and low efficiency, and also have a certain negative impact on the performance of the circuit system.

Clock spread spectrum is another effective method for reducing the EMI. The clock spread spectrum disperses the energy concentrated in a narrow frequency band to a predetermined wide frequency band by means of frequency modulation, so that the amplitude (energy) of the clock at the fundamental frequency and the odd harmonic wave frequency may be reduced to achieve the purpose of reducing the peak value of electromagnetic radiation of the system.

SUMMARY

At least one embodiment of the present disclosure provides a clock spread spectrum circuit, comprising: a control circuit, configured to generate a frequency control word according to a modulation parameter, the frequency control word changing discretely with time; and a signal generation circuit, configured to receive the frequency control word and generate and output a spread spectrum output signal that is spectrum-spread according to the frequency control word, the spread spectrum output signal corresponding to the frequency control word.

For example, in the clock spread spectrum circuit provided by at least one embodiment of the present disclosure, the frequency control word is expressed as: F(t)=I+r(t), where F(t) is the frequency control word, I is an integer part of the frequency control word, I is a constant and an integer, r(t) is a decimal part of the frequency control word, r(t) is a decimal and discretely changes with the time, and t represents the time.

For example, in the clock spread spectrum circuit provided by at least one embodiment of the present disclosure, the modulation parameter comprises a spread spectrum depth coefficient, a spread spectrum reference value, a modulation rate, a reference frequency, and a modulation mode, which correspond to the spread spectrum output signal, and the control circuit comprises: a decimal generation sub-circuit, configured to generate the decimal part according to the spread spectrum depth coefficient, the spread spectrum reference value, the modulation mode, and the modulation rate; an integer generation sub-circuit, configured to generate the integer part according to the reference frequency; and a synthesis sub-circuit, configured to receive the decimal part and the integer part and generate the frequency control word based on the decimal part and the integer part.

For example, in the clock spread spectrum circuit provided by at least one embodiment of the present disclosure, the decimal generation sub-circuit comprises: a frequency modulation control module, configured to generate a frequency modulation clock signal according to the modulation rate to control a rate of change of the frequency control word; and a decimal generation module, configured to generate and output the decimal part to the synthesis sub-circuit according to the modulation mode, the spread spectrum depth coefficient, and the spread spectrum reference value under control of the frequency modulation clock signal.

For example, in the clock spread spectrum circuit provided by at least one embodiment of the present disclosure, the decimal generation module comprises a modulation mode sub-module, the modulation mode comprises a triangle modulation mode, a sawtooth modulation mode, a sinusoidal modulation mode, or a random modulation mode, and the modulation mode sub-module is configured to generate the decimal part by using any one modulation mode selected from a group consisting of the triangle modulation mode, the sawtooth modulation mode, the sinusoidal modulation mode, and the random modulation mode.

For example, in the clock spread spectrum circuit provided by at least one embodiment of the present disclosure, the frequency modulation control module comprises: a counting sub-module, configured to count a reference clock signal to obtain a count value of the reference clock signal; and a timing sub-module, configured to determine a count period according to the modulation rate and determine the frequency modulation clock signal based on the count period and the count value.

For example, in the clock spread spectrum circuit provided by at least one embodiment of the present disclosure, the signal generation circuit comprises: a base time unit generation sub-circuit, configured to generate and output a base time unit; and a spread spectrum sub-circuit, configured to generate and output the spread spectrum output signal according to the frequency control word and the base time unit.

For example, in the clock spread spectrum circuit provided by at least one embodiment of the present disclosure, the base time unit generation sub-circuit comprises: a voltage-controlled oscillator, configured to oscillate at a predetermined oscillation frequency; a phase-locked loop circuit, configured to lock an output frequency of the voltage-controlled oscillator to a base output frequency; and K output terminals, configured to output K base output signals with phases evenly spaced, K is a positive integer greater than 1, and the base output frequency is expressed as fd, the base time unit is a time span between any two adjacent base output signals output by the K output terminals, the base time unit is expressed as Δ, and Δ=1/(K·fd).

For example, in the clock spread spectrum circuit provided by at least one embodiment of the present disclosure, the spread spectrum sub-circuit is a time average frequency direct period synthesizer.

For example, in the clock spread spectrum circuit provided by at least one embodiment of the present disclosure, a maximum value of the frequency control word and a minimum value of the frequency control word satisfy a formula: 0≤Fmax−Fmin<1, and Fmin represents the minimum value of the frequency control word, and Fmax represents the maximum value of the frequency control word.

At least one embodiment of the present disclosure also provides an electronic equipment, comprising: the clock spread spectrum circuit according to any one of the above embodiments.

At least one embodiment of the present disclosure also provides a clock spread spectrum method, applied to the clock spread spectrum circuit according to any one of the above embodiments, and the clock spread spectrum method comprises: generating the frequency control word according to the modulation parameter, the frequency control word changing discretely with the time; and receiving the frequency control word, and generating and outputting the spread spectrum output signal that is spectrum-spread according to the frequency control word, the spread spectrum output signal corresponding to the frequency control word.

For example, in the clock spread spectrum method provided by at least one embodiment of the present disclosure, the frequency control word comprises a decimal part and an integer part, the modulation parameter comprises a spread spectrum depth coefficient, a spread spectrum reference value, a modulation mode, a modulation rate, and a reference frequency, which correspond to the spread spectrum output signal, and generating the frequency control word according to the modulation parameter comprises: generating the decimal part according to the spread spectrum depth coefficient, the spread spectrum reference value, the modulation mode, and the modulation rate, the decimal part being a decimal and changing discretely with the time; generating the integer part according to the reference frequency, the integer part being an integer; and generating the frequency control word according to the decimal part and the integer part.

