Induction Hob Control Algorithm for Beat Noise Reduction
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Solution Overview
Problem
Simultaneous operation of induction heaters in household cooking hobs often results in beat noise and light flickering due to uncoordinated power delivery, which is not compliant with electromagnetic emission regulations and can be annoying for users.
Innovation Solution
A control algorithm that coordinates the operation of two induction heaters using power characteristic curves to deliver preset power levels smoothly, by adjusting the driving frequencies and activation times of the converters, allowing for simultaneous operation without beat noise and minimizing light flickering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If two induction heaters operate simultaneously with independent control, then each heater can deliver its required power level, but beat noise and light flickering occur due to uncoordinated power delivery
Solution Approach 1:
The patent merges the control of two independent induction heaters into a unified coordinated control system. The electronic control unit synchronizes the driving frequencies and power delivery timing of both heaters, making them operate as a coordinated system rather than independent units, thereby eliminating beat noise and light flickering while maintaining individual power requirements.
Solution Approach 2:
The patent implements dynamic frequency adjustment where the driving frequencies of the two heaters are continuously adapted to maintain synchronization. The control system dynamically modifies operating parameters based on real-time conditions to prevent the generation of beat frequencies, transforming the static independent operation into dynamic coordinated operation.
2Productivity
If the driving frequency of induction heaters is increased to improve power delivery speed, then heating efficiency improves, but electromagnetic emissions increase violating regulations
Solution Approach 1:
The patent changes the operating parameters by synchronizing driving frequencies and adjusting power delivery timing. By coordinating the operation phases and frequencies of multiple heaters, the system achieves efficient heating while controlling electromagnetic emissions to comply with regulations, resolving the contradiction between productivity and harmful emissions.
3Ease of operation
If converters operate at different frequencies to deliver different power levels, then individual power control is achieved, but acoustic noise becomes audible and annoying
Solution Approach 1:
The patent applies asymmetry by allowing different power levels for each heater while maintaining frequency symmetry. The control system coordinates the heaters to operate at the same driving frequency but with different power delivery magnitudes, achieving individual power control without generating audible beat frequencies that would result from frequency differences.
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
Enables simultaneous operation of induction heaters to deliver smooth power levels, reducing acoustic noise and electromagnetic interference, while optimizing efficiency and component stress, and ensuring compliance with emission standards.
Implementation Method 1
Vessel heating occurs by the inductive coupling of the metallic pan with the time-varying magnetic field generated by the appliance
Implementation Method 2
The so-called 'eddy currents' are induced in the bottom side of the metallic pan from the electromagnetic field generated by the inductor coil
Implementation Method 3
The induced currents generate heat according to the Joule effect
Data Source
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AI summary
Method for controlling the power delivery to a pair of induction heaters/coils belonging to a household cooking hob. The method comprises a simultaneous activation of both the induction heaters at the same frequency during a first fraction of the control period, and the activation of only one induction heater at a second frequency for a second fraction of the control period.