Induction Cooking Power Control with Capacitor Discharge Cooling
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Solution Overview
Problem
Existing induction cooking appliances face reduced lifespan due to thermal stress on switching elements caused by high voltage switching and hard switching conditions, leading to increased power dissipation and acoustic noise.
Innovation Solution
A method and system that includes a discharging phase to reduce capacitor voltage before heating, followed by a stop phase to allow cooling, ensuring the switching element operates below its maximum temperature, thereby reducing thermal stress and improving lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the capacitor is discharged in the discharging phase before the heating phase, then the voltage provided to the switching element is reduced and power dissipation due to thermal losses is reduced, but considerable stress on the switching device occurs and temperature in the switching element rises during discharging
Solution Approach 1:
The capacitor is discharged in a discharging phase that occurs before the heating phase, preparing the circuit by reducing capacitor voltage to a safe level (50 V or lower) before the switching element needs to operate. This preliminary action prevents high voltage stress during subsequent heating operations.
Solution Approach 2:
The operating cycle is divided into distinct phases: discharging phase, first stop phase, and heating phase. This segmentation allows the circuit to perform different functions at different times, separating the capacitor discharge operation from the heating operation to manage thermal and electrical stress on the switching element.
2Object-generated harmful factors
If the discharging phase is provided to reduce capacitor voltage, then switching-on of the switching element at high voltage levels is avoided and acoustic noise is reduced, but the lifespan of the switching device is reduced due to temperature rise during discharging
Solution Approach 1:
The capacitor is discharged before the heating phase begins, eliminating the harmful high voltage switching conditions that cause acoustic noise. By preparing the circuit in advance, the switching element operates under safe voltage conditions during heating.
Solution Approach 2:
The system operates in periodic cycles consisting of discharging phase, first stop phase, and heating phase. This periodic operation allows thermal management by inserting cooling intervals between high-stress operations, enabling the switching element to return to safe operating temperatures before the next cycle.
3Duration of action of stationary object
If the first stop phase is provided between the discharging phase and the heating phase, then the switching element has time to cool down and lifespan is increased, but the operation time of the appliance is extended
Solution Approach 1:
The operating cycle is segmented into distinct phases including the first stop phase that provides cooling time. This segmentation makes the thermal management explicit and controllable, allowing the system to manage heat dissipation systematically.
Solution Approach 2:
The system uses periodic operation with defined phases including cooling intervals. The periodic nature allows the switching element to cool down systematically between high-stress operations, with the cycle time optimized to balance cooling requirements against operational efficiency.
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
The method extends the lifespan of switching elements by minimizing thermal stress and power dissipation, while maintaining efficient power control through sequential phases, enhancing the overall appliance's durability.
Implementation Method 1
controlling the circuitry of the induction cooking appliance to enter into a discharging phase to discharge the capacitor
Implementation Method 2
the switching element provides pulsed electric power to the resonance circuit (in particular to the induction coil of the resonance circuit)
Implementation Method 3
a resonance circuit with an induction coil and a resonance capacitor
Data Source
Figure 1~2
Figure 3
AI summary
The invention provides a method for controlling the supply of electric power to an induction cooking appliance (1). The induction cooking appliance (1) comprises a circuitry (10) having: an AC-voltage input (11) for receiving an AC-voltage signal (Vin), a resonance circuit (17) with an induction coil (20) and a resonance capacitor (18), at least one switching element (12) for providing pulsed electric power to the resonance circuit (17), and a capacitor (16) being connected in parallel to the series of the switching element (12) and the resonance circuit (17). The method comprises: receiving an AC-voltage signal (Vin) at the AC-voltage input (11), controlling the circuitry (10) of the induction cooking appliance to enter into a discharging phase (D1) to discharge the capacitor (16), after at least partially discharging the capacitor (16), controlling the circuitry (10) to enter into a first stop phase (D2) in which the switching element (12) is in an off-state, and after the first stop phase (D2), controlling the circuitry (10) to enter into a heating phase (D3) in which the switching element (12) provides pulsed electric power to the resonance circuit (17).