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Low-Pass Filtering Method for PWM Square Wave

A pulse width modulation, low-pass filter technology, applied in the direction of pulse duration/width modulation, impedance network, digital-to-analog converter, etc., can solve the problems of high implementation cost and large size, and achieve the effect of reducing cost

Inactive Publication Date: 2017-11-24
深圳云朵数据技术有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

For example, the time constant of a low-pass filter composed of resistors and capacitors is quite large, and the corresponding resistor and capacitor values ​​are quite large; the size of the corresponding resistor and capacitor is quite large; in the switched capacitor filter circuit, the capacitance ratio is required to be quite large, and The switching frequency is required to be much higher than the signal frequency; in the switching current filter circuit, the corresponding storage current has a large variation range, and the switching frequency is required to be much higher than the signal frequency; these requirements make the low-pass filter for low-frequency PWM square wave signals Realization cost is relatively high

Method used

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  • Low-Pass Filtering Method for PWM Square Wave
  • Low-Pass Filtering Method for PWM Square Wave
  • Low-Pass Filtering Method for PWM Square Wave

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0038] Embodiment 1, a kind of low-pass filter circuit, such as figure 2 Shown:

[0039] Select add-subtract counter 20 as the step-by-step accumulation increment function block 2;

[0040] The combination of the comparator 10 and the logic NOT gate and the AND gate "&" forms a positive and negative increment judgment function block 1; specifically: the output of the comparator 10 is the input of the logic NOT gate and the AND gate "&";

[0041] Select digital-to-analog converter 30 as digital-to-analog converter 3;

[0042] Select the addition frequency voltage-controlled oscillator 40 as the variable positive increment controller 4;

[0043] The combination of the subtraction frequency voltage controlled oscillator 51 and the modulus subtractor 52 forms the variable negative increment controller 5 .

[0044] Input one of the comparator 10, that is, the input of the low-pass filter, is connected with the pulse width modulated square wave signal Vin; as figure 2 shown. ...

Embodiment 2

[0059] will be like figure 2 The first-order low-pass filter cascading can obtain high-order low-pass filter; image 3 As shown, place 2 figure 2 The cascading of the low-pass filters can obtain a second-order low-pass filter.

[0060] At this time, the analog voltage output by the digital-to-analog converter 30 may be used as the input of the next-stage low-pass filter. In this way, two stages of first-order low-pass filters are cascaded to obtain a second-order low-pass filter function.

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Abstract

The invention discloses a low-pass filter method for pulse width modulation square wave. The low-pass filter is composed of the following functional blocks: a positive and negative incremental judgment functional block, a step-by-step accumulation incremental functional block, a digital-to-analog converter, Variable positive incremental controller, variable negative incremental controller. The present invention makes full use of the characteristics of the pulse width modulated square wave, that is, the two levels of high level and low level; so that in the whole pulse period, relative to the DC level corresponding to the pulse width modulated square wave, there are only two levels greater than and less than two states. In this way, the low-pass filter function can be completed with positive increments and negative increments; that is, when it is greater than the state, the corresponding DC level is increased step by step by increasing the positive increment; decrease the corresponding DC level in steps. Further, the method of variable increment is adopted to make the corresponding DC level closer to the output level of the low-pass filter.

Description

technical field [0001] The invention relates to a low-pass filtering method for pulse width modulated square waves. Background technique [0002] There are many ways to low-pass filter the pulse width modulated square wave signal inside the integrated circuit, such as using a low-pass filter circuit composed of resistors and capacitors (which can be high-order); using a switched capacitor filter circuit, that is, using a switched capacitor To replace the resistor; use a switch current filter circuit (close to the concept of a digital filter); use a digital filter circuit to achieve. All of these implementation methods have a problem of implementation cost. Especially for the case where the frequency of the pulse width modulated square wave signal is relatively low, such as 100 Hz, the implementation cost is a problem. For example, the time constant of a low-pass filter composed of resistors and capacitors is quite large, and the corresponding resistor and capacitor values ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H03H17/00H03M1/66H03K7/08
Inventor 翁大丰孙建中魏其萃
Owner 深圳云朵数据技术有限公司