Buzzer PWM-to-Square-Wave Conversion Without Filters or Amplifiers
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Solution Overview
Problem
Existing facsimile communication apparatuses require complex circuits with filters and amplifiers to convert PWM waves to square waves for buzzer control, leading to increased complexity and noise issues.
Innovation Solution
A buzzer control apparatus that generates a square wave by determining pulse width differences in PWM waves, eliminating the need for filters and amplifiers by directly converting PWM waves to square waves using a processing unit with a first and second counter for pulse width determination and switching the square wave state based on difference value sign changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If filters and amplifiers are used to convert PWM wave to square wave, then the conversion is achieved, but the circuit complexity increases
Solution Approach 1:
The patent extracts and eliminates the unnecessary filters and amplifiers from the PWM-to-square-wave conversion circuit, retaining only the essential components. This removal of redundant elements directly reduces circuit complexity while maintaining the core conversion function through a simplified comparator-based approach.
Solution Approach 2:
The patent changes the operating parameters and configuration of the conversion circuit by using a comparator with hysteresis instead of traditional filter-amplifier stages. This parameter change enables direct PWM-to-square-wave conversion without requiring the complex filtering and amplification stages, thereby reducing circuit complexity.
2Object-affected harmful factors
If filters and amplifiers are used in the conversion circuit, then noise is reduced, but the circuit complexity increases
Solution Approach 1:
The patent removes the filter and amplifier components that were traditionally used to reduce noise in PWM conversion circuits. Instead, it relies on the inherent noise-rejection capabilities of the comparator-based conversion mechanism, thereby eliminating the need for additional noise-reduction hardware and reducing overall circuit complexity.
Solution Approach 2:
The conversion circuit performs its own noise filtering function through the comparator's inherent characteristics and hysteresis mechanism, without requiring external filter components. The circuit serves its own noise-reduction needs through its core conversion mechanism, eliminating the need for separate noise-reduction stages.
3Device complexity
If a simplified circuit without filters and amplifiers is used, then circuit complexity is reduced, but noise control becomes difficult
Solution Approach 1:
The patent introduces a hysteresis mechanism as an intermediary element within the comparator-based conversion circuit. This hysteresis acts as a built-in noise filter that prevents false triggering and stabilizes the conversion process, effectively controlling noise without requiring external filter components.
Solution Approach 2:
The patent modifies the operational parameters of the comparator by implementing hysteresis, which creates different threshold levels for rising and falling edges. This parameter change enables the simplified circuit to inherently reject noise and prevent false conversions, maintaining noise control capabilities without complex filtering hardware.
4Ease of manufacture
If an IC-based configuration is used, then ease of manufacture is improved, but circuit complexity may increase
Solution Approach 1:
The patent merges the PWM-to-square-wave conversion function into a single integrated circuit (comparator with hysteresis), combining multiple functions that would traditionally require separate filter, amplifier, and conversion components into one unified IC. This integration simplifies the overall system and improves ease of manufacture despite the sophisticated internal circuitry.
Solution Approach 2:
The comparator-based IC performs multiple functions simultaneously: PWM signal reception, noise filtering through hysteresis, threshold comparison, and square-wave generation. This multi-functionality within a single IC component reduces the total number of discrete components needed and simplifies the overall circuit while maintaining robust noise control capabilities.
Data Source
AI summary
An apparatus includes: a generation unit that generates a PWM wave based on a sound signal; and a processing unit that converts the PWM wave to a square wave. The processing unit includes: a first counter that determines a pulse width of the PWM wave; a comparison unit that compares a first difference value, obtained by subtracting the pulse width in a second cycle being a cycle immediately preceding a first cycle from the pulse width in the first cycle, and a second difference value obtained by subtracting the pulse width in a cycle immediately preceding the second cycle from the pulse width in the second cycle; and an output unit that outputs the square wave while switching a state thereof in a case where a sign of the first difference value changes from that of the second difference value.