External clock synchronization circuit of switching power supply

Abstract

The invention discloses an external clock synchronization circuit of a switching power supply. In the prior art, a circuit structure is complex, external synchronization time is long and frequency jitter exists. By using the external clock synchronization circuit of the switching power supply, the above disadvantages can be overcome. The circuit comprises: a frequency-halving circuit, a frequency cap detection circuit, a lower limit frequency detection circuit, an external synchronization stopping detection circuit and a frequency selection circuit. An external synchronous clock is connected to the lower limit frequency detection circuit and the frequency cap detection circuit through the frequency-halving circuit so as to detect whether the external synchronous clock frequency is in a preset numerical interval. The lower limit frequency detection circuit is connected with the synchronization stopping detection circuit so as to determine whether the external synchronous clock is removed. Control signals output by the lower limit frequency detection circuit and the frequency cap detection circuit are connected to the frequency selection circuit so that the frequency selection circuit is controlled to select one from an internal clock and the external synchronous clock to output so as to be taken as a working clock of the switching power supply. A circuit structure is simple. The external clock can be rapidly and accurately synchronized and the external clock synchronization circuit of the invention can be applied in various kinds of the switching power supplies.

Description

technical field [0001] The invention belongs to the technical field of electronic circuits, and relates to an analog integrated circuit, in particular to an external clock synchronization circuit of a switching power supply. Background technique [0002] Switching power supply is widely used in various electronic devices due to its light weight, small size, high conversion efficiency and many other advantages. However, since it works at a certain frequency, frequency-related problems such as electromagnetic interference and switching noise are unavoidable. In particular, the problem of difference frequency noise in parallel or series systems of multiple switching power supplies with close frequencies is particularly prominent. The operating clock of the switching power supply is generally provided by an internal oscillator, but because the frequency provided internally is fixed, it cannot be changed at any time to adapt to different application environments. Therefore, for...

AI Technical Summary

Problems solved by technology

[0004] Since the phase-locked loop technology is used to realize the clock external synchronization function, it is necessary to consider the loop stability of the phase-locked loop, the circuit is relatively complicated, and it takes a long time to lock the frequency, and the time for the entire clock external synchronization is relatively long. In addition, due to the lock Due to the non-ideal characteristics of the phase loop, there is frequency jitter, so it cannot accurately synchronize the external clock signal

Images