Pulse width modulation signal generation circuit and pulse width modulation signal generation method

Abstract

The invention provides a pulse width modulation (PWM) signal generating circuit and method. The PWM signal generating circuit comprises a reference signal generating circuit, a variable ramp signal generating circuit and a comparator circuit, wherein the reference signal generating circuit is used for generating a reference signal according to an input voltage; the variable ramp signal generating circuit is used for generating a variable ramp signal; the comparator circuit is used for comparing the reference signal and the variable ramp signal, and generating a PWM signal according to the comparative result. The rising slope rate and / or the descending slope rate of the variable ramp signal are / is changeable.

Description

Technical field [0001] The present invention relates to a pulse width modulation (PWM) signal generation circuit and a pulse width modulation signal generation method, in particular to a method for determining the duty ratio of a PWM signal by adjusting the slope of a variable ramp signal ratio) PWM signal generating circuit and PWM signal generating method. Background technique [0002] Figure 1A A schematic circuit diagram of a typical PWM signal generating circuit 10 is shown. Such as Figure 1A As shown, the PWM signal generating circuit 10 includes a reference voltage generating circuit 11, a fixed ramp signal generating circuit 13, and a comparator circuit 15. The comparator circuit 15 compares the reference signal Comp with a ramp signal Ramp having a fixed waveform and level to generate a PWM signal; wherein the reference signal Comp has a linear relationship with the input voltage Vin, and the ramp signal Ramp is a triangular wave with a fixed slope and amplitude Or saw...

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Problems solved by technology

[0006] However, the disadvantage of this prior art is that the peaks and troughs of the ramp signal OSC1 or OSC2 have upper and lower limits, that is, the level variation range of the ramp signal OSC1 or OSC2 is limited. When the potential of the input voltage Vin is close to the upper limit or the lower limit, the ramp The signal OSC1 or OSC2 is limited by its level variation range, and cannot be adjusted to a suitable corresponding position to generate a PWM signal in a certain duty ratio range, that is, it cannot achieve rail-to-rail adjustment and control

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