Triangular wave generation circuit based on frequency modulation

Abstract

The invention discloses a triangular wave generation circuit based on frequency modulation. The circuit comprises a current transformer, an inductance phase-shift circuit, a zero-crossing comparison circuit, a frequency multiplier circuit and a triangular wave generation circuit body, wherein a primary winding of the current transformer is connected with an alternating-current input signal, the inductance phase-shift circuit is connected with a secondary winding of the current transformer, the zero-crossing comparison circuit is connected with the two ends of the inductance phase-shift circuit and used for converting alternating-current voltage signals at the two ends of the inductance phase-shift circuit into square wave signals by means of zero-crossing comparators respectively, the frequency multiplier circuit is connected with the output end of the zero-crossing comparison circuit and is used for enabling the frequency of the square wave signals to be twice that of the alternating-current input signals, and the triangular wave generation circuit body is connected with the output end of the frequency multiplier circuit and used for driving a triode by means of the square wave signals to carry out charging and discharging control on a capacitor to generate triangular wave signals with the modulated frequency. According to the circuit, the triangular wave signals can be changed long with change of the frequency of the input alternating-current signals, and intensity of electromagnetic interference can be greatly reduced.

Description

technical field [0001] The invention relates to a waveform generating circuit, in particular to a triangular wave generating circuit whose frequency and amplitude vary with the frequency of an input signal. Background technique [0002] In order to automatically stabilize the output voltage and not be affected by operating conditions (input voltage fluctuations, load changes) and external disturbances, in the feedback control system of switching power supplies, closed-loop control modes are usually used: voltage control mode and current control mode and voltage and current double loop control mode. In these control modes, the set signal is usually compared with the feedback signal, adjusted by a PI regulator to obtain the output signal of the feedback control system, and the output signal is used to cut the triangular wave to obtain the drive to control the operation of the switch tube square wave. [0003] Traditional PWM technology generally uses a fixed-frequency triang...

AI Technical Summary

Problems solved by technology

The traditional PWM chopping technology adopts a fixed frequency modulation scheme. In its high-order harmonic distribution law, the interference level of integer multiples of the switching frequency and its side frequency is quite high, and the fixed frequency is also difficult to increase the output power.

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