Induction Cooktop Inverter Phase Control for Flicker Reduction
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Solution Overview
Problem
Conventional induction hobs face challenges in independently setting heating outputs for multiple inductors while complying with flicker standards and avoiding interference hum, often requiring complex time-division multiplex methods that can lead to voltage jumps and flicker issues.
Innovation Solution
A hob design featuring at least two heating inductors connected to a common resonant circuit capacitor, with a control unit that operates the inverters at the same frequency and adjusts the phase shift and pulse lengths to independently control the heating powers, eliminating the need for time-division multiplex and reducing electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If independent oscillating circuits are used for each heating inductor, then heating outputs can be set independently, but interference hum and flicker problems occur
Solution Approach 1:
The patent combines multiple heating inductors into a single common oscillating circuit, sharing resonant capacitors and control electronics. This merging eliminates the independent oscillating circuits that cause interference hum and flicker, while the control unit maintains independent heating output control through phase-shifted PWM signals to each inductor.
2Ease of operation
If time-division multiplex method is used, then different heating outputs can be achieved, but the control becomes complex and voltage jumps occur
Solution Approach 1:
The patent uses periodic PWM switching signals with phase shifts to control each heating inductor. Instead of complex time-division multiplexing, the control unit generates synchronized periodic waveforms that are phase-shifted relative to each other, enabling independent power control through simple phase adjustment rather than complex timing sequences.
Solution Approach 2:
The control unit independently adjusts the phase shift and pulse width parameters of PWM signals sent to each inductor. By changing these parameters continuously rather than switching between discrete time windows, the system achieves smooth heating output adjustment without the complexity and voltage jumps associated with time-division multiplexing.
3Adaptability or versatility
If multiple resonant circuit capacitors are used for each inductor, then independent frequency control is possible, but the number of components and cost increase
Solution Approach 1:
The patent merges the resonant circuit capacitors into a shared common oscillating circuit that serves all heating inductors. Instead of having separate capacitors for each inductor, the system uses a set of resonant capacitors that can be switched or combined to provide the necessary frequency control flexibility for all inductors simultaneously, reducing the total component count and cost.
Solution Approach 2:
The common resonant capacitors serve multiple functions: they form the oscillating circuit for all inductors, provide frequency selection through switching configurations, and enable independent power control when combined with phase-shifted PWM signals. This multi-functionality replaces the need for dedicated capacitors for each inductor while maintaining frequency control flexibility.
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 solution allows for flexible and efficient adjustment of heating outputs without complex calculations, reduces flicker and interference, and improves electromagnetic emission characteristics by using a common resonant circuit capacitor and two inverters, enabling independent control of heating powers over a wide range.
Implementation Method 1
The series resonant circuit is supplied with high-frequency heating current by an inverter. The frequency of the heating current determines the heating capacity of the heating inductor, which generates high-frequency alternating magnetic fields. The alternating magnetic fields generate eddy currents in the base of a cookware element placed on the hob, which heats up this base.
Implementation Method 2
The frequency of the heating current determines the heating capacity of the heating inductor, which generates high-frequency alternating magnetic fields. The alternating magnetic fields generate eddy currents in the base of a cookware element placed on the hob
Implementation Method 3
The series resonant circuit is supplied with high-frequency heating current by an inverter
Data Source
Figure 1~2
Figure 3~5
AI summary
The invention relates to a cook top comprising at least two heating inductors (10a, 10b), each of which is connected to at least one resonant circuit capacitor (26a, 26b) to form a resonant circuit. In order to provide a cost-saving cook top, at least one common resonant circuit capacitor (26a, 26b) is connected to the two heating inductors (10a, 10b). DRAWING: Fig. 1: