Switch power supply as well as used frequency jitter generating device and method thereof

Abstract

The invention relates to a switch power supply as well as used frequency jitter generating device and method thereof. The switch power supply comprises an input circuit, an output circuit and a feedback control loop, wherein the feedback control loop comprises a transformer, a controller and a power switch tube; the drain electrode of the power switch tube is connected to the primary coil of the transformer, and the source electrode and the grid electrode thereof are connected to the controller; and the output circuit is connected to the secondary coil of the transformer. The controller changes the switching period of the switch tube according to a jitter frequency which is generated by the controller per se and has output adaptive frequency amplitude and a feedback signal provided by the feedback control loop so as to regulate output voltage. By implementing the switch power supply and the frequency jitter scheme and device, a cheap and simple EMI (Electro-Magnetic Interference) filter can be utilized to carry out EMI filtering, and the output noise of the switch power supply can be kept at a lower level under the light load condition. Moreover, the invention can also further adjust the frequency jitter amplitude through sensing load current.

Description

technical field [0001] The present invention relates to a switching power supply, and more particularly, to a switching power supply with a frequency jitter generating function and a frequency jitter generating device and method therefor. Background technique [0002] A common problem with switching power supplies is that their switching frequency is usually high, and this high-frequency signal couples to and becomes a component of the grid voltage, causing noise to other electrical equipment connected to the grid. In addition, the high-frequency signal is also conducted or radiated in the form of electromagnetic waves, thereby causing electromagnetic interference (EMI) to the communication equipment around the power supply. [0003] A common method of suppressing EMI is to introduce frequency jitter in order to extend the switching frequency to a wider frequency band, thereby reducing the peak EMI generated by the power supply at a certain frequency. Existing frequency jit...

AI Technical Summary

Problems solved by technology

[0004] Although in figure 1 The frequency dithering scheme shown eliminates the need for bulky and expensive EMI filters, but it increases the average noise floor, which is unacceptable in certain applications such as high-fidelity audio systems

This is because hi-fi audio systems can tolerate a higher average output noise floor generated by switching power supplies at higher volumes, but become very noise sensitive at lower volumes

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