PWM Heater Control for Stable Water Temperature and Low Flicker
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Solution Overview
Problem
Smart toilets with water heating systems face flickering disturbances due to insufficient heating capacity, leading to fluctuations in water temperature during high flow rates, which exceed or fall below electromagnetic compatibility (EMC) limits, increasing product complexity and costs.
Innovation Solution
A heater control method that sets a target temperature, detects inlet and outlet temperatures, calculates required output power using PID control, and converts it into a duty cycle combination of PWM signals to control the heating process, reducing flicker noise by regulating the number of upper and lower clocks of modulation signals, while ensuring compliance with EMC requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the heating power is increased to maintain constant water temperature at high flow rates, then the temperature stability is improved, but the flicker noise exceeds EMC limit values
Solution Approach 1:
The heating assembly is divided into two or three independent stages (e.g., 1600W split into two 800W halves). Each stage can be controlled independently, allowing the system to meet temperature stability requirements while keeping individual power regulation fluctuations within EMC limits.
Solution Approach 2:
The system uses PWM (pulse width modulation) to regulate power output by varying the duty cycle. This periodic switching control allows precise power adjustment while reducing flicker noise through controlled on/off cycles that keep individual regulation fluctuations within acceptable ranges.
2Object-affected harmful factors
If multi-level control capabilities are added to reduce flicker noise, then the flicker measurement requirements are met, but the product structure and electronic control circuitry complexity increases
Solution Approach 1:
Multiple heating assemblies are controlled through a unified PWM control system. The control circuitry integrates the regulation of multiple stages into a single control architecture, reducing overall system complexity while still achieving flicker noise reduction through staged power delivery.
Solution Approach 2:
The system adjusts the duty cycle parameter of PWM signals to control power output. By varying this single parameter across different heating stages, the system achieves multi-level control without adding complex circuitry, as all stages use the same control mechanism with different duty cycle settings.
3Productivity
If the heating capacity is increased to handle large water flow rates at constant temperature, then the temperature stability is improved, but the flicker noise during power regulation exceeds EMC limits
Solution Approach 1:
The heating system is segmented into multiple independent heating assemblies that can operate simultaneously. This allows the system to handle large water flow rates with increased total heating capacity while each individual assembly operates at a power level that produces acceptable flicker noise within EMC limits.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method allows for arbitrary regulation of output power within 0-2000W, maintaining constant water temperature and reducing flicker noise without increasing product complexity, enhancing temperature control response speed and stability.
Implementation Method 1
a heating system of an electric water heater
Implementation Method 2
The recorded temperature result can also be passed on to the board processor. After the calculation by the processor, the heating system is controlled depending on the result and the heating output is adjusted in order to keep the water outlet temperature constant.
Implementation Method 3
converting the output power into a duty cycle combination of PWM signals, controlling the respective number of upper and lower clocks of the modulation signals
Data Source
Figure 1
Figure 2~3
AI summary
The present invention relates to a heating control method and a heating control device for reducing flickering disturbances, comprising the following steps: setting a target temperature (S101); detecting a water inlet temperature and a water outlet temperature (S102); calculating the output power required for heating based on the detected water inlet and outlet temperatures and the set target temperature (S103); converting the output power into a duty cycle combination of PWM signals; controlling the respective number of upper and lower clock cycles of the modulation signals based on the duty cycle combination of PWM signals (S104); controlling the heating process based on the respective number of upper and lower clock cycles of the modulation signals (S105); determining whether a stop command is present; if so, terminating the heating process; if not, returning to step S102 (S106).The heating control method according to the invention adequately meets the requirements for flicker measurement within the framework of electromagnetic compatibility, but without increasing the complexity of the product structure and the electronic control circuit, thus reducing component costs and assembly effort.