Voltage reference circuit of pulse width modulation

Abstract

This invention discloses a voltage primary circuit for a pulse width modulator including a soft start-up circuit, a band-gap primary circuit and a small current charge circuit, in which, the soft start up circuit provides suitable offset to the band-gap primary circuit to start it up smoothly, the output end of the primary signal VREFO is connected with the small current charge circuit, which uses the obtained small current to charge a rather big capacitor to rise the output signal VREF of the entire primary circuit steadily.

Description

1. Technical field [0001] The DC / DC pulse width modulator belongs to a class of power management chips, and the invention relates to a voltage reference circuit suitable for the pulse width modulator. 2. Background technology [0002] DC / DC pulse width modulators occupy a large proportion in power management chips, and are widely used in portable products, especially consumer electronics. [0003] figure 1 The basic circuit structure of a commonly used pulse width modulator (PWM) is given, which consists of error amplifier, startup circuit and reference circuit, phase compensation, pulse width modulation controller, comparator, ramp generator and oscillator, buffer drive These modules are composed, and the reference voltage module is a common bandgap reference circuit. [0004] figure 2 It is an architecture diagram of a step-up DC / DC converter based on the principle of pulse width modulation, and the chip part is figure 1 content shown. [0005] Let's take the step-up...

AI Technical Summary

Problems solved by technology

[0012] The above is the reason for the overshoot phenomenon when the existing pulse width modulator system is just started. The most fundamental reason is that there is a time difference between the start-up of the bandgap voltage and the establishment of the output voltage Vo.

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