Frequency jittering system and frequency jittering method

Abstract

The invention discloses a frequency jittering system and a frequency jittering method. The frequency jittering system comprises an oscillator, a weighting operation module and a digital-to-analog converter, wherein the oscillator is used for outputting and generating a plurality of digital sequences; each digital sequence comprises a periodic sequence and a pseudorandom sequence; the weighting operation module is connected with the oscillator and used for carrying out weighting operation on a plurality of digital sequences; the digital-to-analog converter is connected with the weighting operation module and the oscillator and used for converting an output signal of the weighting operation module into an analog signal, and the analog signal is used for controlling the frequency of the oscillator. The frequency jittering system and the frequency jittering method generate frequency jittering in a mixing frequency jittering way and can provide a flexible and optimal frequency jittering wayfor the system.

Description

technical field [0001] The invention belongs to the technical field of integrated circuit design, and relates to a frequency dithering system, in particular to a frequency dithering system applicable to a switching power supply; in addition, the invention also relates to a frequency dithering method of the frequency dithering system. Background technique [0002] Power converters are essential components in electronic systems. As we all know, power conversion includes two main types: linear converter and switching power converter. Most electrical equipment contains internal power converters or external power adapters. For example, internal power converters are used in products such as televisions and computers, which are widely used in mobile phones, DSL modems, printers, notebook computers and game consoles. The most important is the external power adapter, these power converters or adapters use switching power converters to provide power. Compared with linear converters,...

AI Technical Summary

Problems solved by technology

[0012] use Figure 4 The system described in has a disadvantage as a frequency shaking method: because its pseudo-random series spectrum is too white noise, it will cause the system to be unstable

[0014] Figure 5 and Image 6 The frequency shaking method of the fixed digital cycle sequence shown has two defects: (1) Since the frequency shaking is repeated periodically, the effect of spectrum spreading will be relatively reduced

(2) The selected value of the frequency shaking repetition period may conflict with the system bandwidth

If the frequency shaking repetition period is very low, it is entirely possible to fall within the system bandwidth, which will cause the system to be unstable and even produce audible noise (audio noise)

[0015] Figure 3 to Figure 6 The fixed digital sequence frequency jitter method shown has two defects: first, the frequency spectrum jitter effect is not flexible

Because the jitter method is fixed, the resulting spectrum spread effect is also fixed, so if the energy of a certain frequency point is high during the EMI test, resulting in a small EMI margin, this frequency jitter method cannot be adjusted. In many cases, the system EMI test will fail

Second, there is another defect in the fixed digital sequence frequency jitter method: the spectrum jitter effect cannot be adaptively adjusted with the system output power

Because the EMI test of the system is basically at full load, and the system does not have high requirements for EMI at light load, so that the stability of the system at light load decreases, especially when the system is in burst mode at no load. , then the frequency jitter will deteriorate the stability of the system

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