Induction Coil Power Control via Capacitor Discharge
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Solution Overview
Problem
Induction cooking appliances with quasi-resonant architecture face limitations in power variation due to increased switching losses and acoustic noise at low power levels, restricting the range of power levels that can be controlled.
Innovation Solution
A method for controlling the provision of electric power to an induction coil by discharging a capacitor before switching operations to reduce the voltage applied to the switching element, thereby mitigating hard switching conditions and associated thermal and acoustic issues, using a circuitry with a switching element and a capacitor connected in parallel, and controlling the discharging and switching operations based on the rectified AC-voltage slope.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If power level is reduced to low levels, then power control range is improved, but switching losses and thermal losses increase due to hard switching conditions
Solution Approach 1:
The capacitor is discharged before the switching operation to pre-reduce the voltage level. This preliminary action ensures that when the switching element turns on, the voltage is already lowered, preventing hard switching conditions and reducing switching losses while enabling low power level operation
Solution Approach 2:
The voltage parameter is dynamically changed by controlling the capacitor discharge level before switching. By adjusting the discharge degree of the capacitor, the voltage applied to the switching element is optimized for each operating condition, reducing switching losses at low power levels while maintaining control flexibility
2Adaptability or versatility
If power level is reduced to low levels, then power control range is improved, but acoustic noise increases due to hard switching conditions
Solution Approach 1:
The capacitor is discharged before the switching operation to pre-reduce the voltage level. This preliminary action ensures that when the switching element turns on, the voltage is already lowered, preventing hard switching conditions and reducing acoustic noise while enabling low power level operation
Solution Approach 2:
The voltage parameter is dynamically changed by controlling the capacitor discharge level before switching. By adjusting the discharge degree of the capacitor, the voltage applied to the switching element is optimized for each operating condition, reducing acoustic noise at low power levels while maintaining control flexibility
3Loss of energy
If capacitor is discharged before switching operation, then switching losses are reduced, but additional control complexity is introduced
Solution Approach 1:
The capacitor serves multiple functions: it smooths rectified voltage, stores energy for switching operations, and acts as a voltage reduction mechanism before switching. By making the capacitor multi-functional, the patent reduces power dissipation without requiring separate components for each function, thereby limiting the increase in control complexity
4Adaptability or versatility
If switching operation is optimized for low power, then power control range is improved, but thermal losses in switching element increase
Solution Approach 1:
The capacitor is discharged before the switching operation to pre-reduce the voltage level. This preliminary action ensures that when the switching element turns on, the voltage is already lowered, preventing hard switching conditions and reducing thermal losses while enabling low power level operation
Solution Approach 2:
The voltage parameter is dynamically changed by controlling the capacitor discharge level before switching. By adjusting the discharge degree of the capacitor, the voltage applied to the switching element is optimized for each operating condition, reducing thermal losses at low power levels while maintaining 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 approach reduces power dissipation and acoustic noise, enabling a broader range of power control while maintaining safe operating temperatures and minimizing switching pauses, thus enhancing the efficiency and usability of induction cooking appliances.
Implementation Method 1
a capacitor (C) connected in parallel to the switching element (S). The method comprises the steps of receiving rectified AC-voltage at an input of the circuitry; discharging the capacitor (C) in order to reduce the voltage provided to the switching element (S)
Implementation Method 2
an induction coil (L) electrically coupled with the switching element (S) for creating an alternating magnetic field
Implementation Method 3
for transferring heating power to a foodstuff or a cooking liquid, preferably contained in a cookware item
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a method for controlling the provision of electric power to an induction coil (L) of an induction cooking appliance (1), the induction cooking appliance (1) comprising a circuitry (10) with an input (11), at least one switching element (S) for providing pulsed electric power to the induction coil (L) and a capacitor (C) being connected in parallel to the switching element (S), the method comprising the steps of: - receiving rectified AC-voltage (Vin) at the input (11) of the circuitry (10); - discharging the capacitor (C) in order to reduce the voltage provided to the switching element (S); - after at least partially discharging the capacitor (C), starting a switching operation of the switching element (S); - stopping the switching operation after a switching operation time; and - iterating the steps of discharging of capacitor (C), starting of switching operation and stopping of switching operation in subsequent periods of rectified AC-voltage (Vin).