Heating Element Zero-Crossing Switching for Flicker Reduction
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Solution Overview
Problem
High power electrical loads in kitchen appliances cause visible flickering of lights due to voltage/current fluctuations in the power mains, which existing technologies fail to adequately address without incurring costly electromagnetic compatibility (EMC) filter solutions.
Innovation Solution
The implementation of zero crossing switching for high power loads, using a switching signal with frequency components above 24 Hz to minimize observable flicker, achieved through independent switching of each load over half or full cycles, with the switching sequence generated from a lookup table or controlled by a processor to maintain desired power levels and temperature profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If heating elements are switched on and off to control power output, then power control is achieved, but voltage fluctuation causes visible light flickering
Solution Approach 1:
The patent applies periodic action by switching heating elements in a repeating sequence of half-cycles or full-cycles. The switching pattern is designed to repeat every 5 or fewer half-cycles (or 3 or fewer full-cycles) of the mains power, creating a periodic control mechanism that achieves power regulation while maintaining frequency components above the human visual detection threshold of 24 Hz.
Solution Approach 2:
The patent changes the frequency parameter of the switching signal to resolve the flicker issue. By ensuring the switching sequence repeats frequently enough (5 or fewer half-cycles for 60 Hz mains, 4 or fewer for 50 Hz mains), the frequency components are pushed above 24 Hz, making the flickering imperceptible to humans while maintaining effective power control.
2Power
If dimming circuit is used to control heating elements, then different power profiles are achieved, but electromagnetic interference requires costly EMC filter circuits
Solution Approach 1:
The patent extracts and eliminates the need for costly EMC filter circuits by using a different approach - simple zero-crossing switching control. Instead of using dimming circuits that generate electromagnetic interference requiring filtering, the invention uses direct switching of heating elements at zero-crossing points, achieving the same power profile control without the harmful electromagnetic emissions that would require EMC filtering.
3Object-affected harmful factors
If switching frequency is increased to reduce flicker, then light flickering is reduced, but power control precision may be affected
Solution Approach 1:
The patent uses dynamic switching sequences that can be adjusted based on the required power level and heating stage. The switching pattern is not fixed but can be modified to provide different power profiles (such as high power for initial heating, then reduced power for temperature maintenance), allowing both effective flicker reduction and precise power control through adaptive switching strategies.
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 approach effectively reduces or eliminates observable flickering of lights connected to the same power circuit by ensuring that frequency components above 24 Hz dominate, thereby avoiding the need for costly EMC filter circuits and providing flexible power control while maintaining efficient temperature management.
Implementation Method 1
each load is independently switched using a switching signal for zero crossing switching to achieve a desired average power output
Implementation Method 2
one or more switched high power loads (or heating elements), each high power load being powered from a common alternating current power source
Data Source
AI summary
An apparatus for controlling one or more switched high power loads (or heating elements). The apparatus including: one or more switched high power loads (or heating elements), each high power load being powered from a common alternating current power source, and wherein each load is independently switched using a switching signal for zero crossing switching to achieve a desired average power output; the switching signal is generated that comprises a repeated switching sequence; the switching sequence indicates a respective selecting activation for each of the switched high power load over a sequence of half or full cycles.