Multi-Coil Induction Heating Control for Lower Switching Loss
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Solution Overview
Problem
Induction heating devices experience increased switching loss when using multiple heating coils due to large currents generated by summed currents flowing through the coils.
Innovation Solution
The induction heating device employs a control mechanism that alternately drives inverter circuits out-of-phase and in-phase for different heating coils, using a time-sharing method to reduce switching loss by controlling power distribution across multiple coils.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple heating coils are driven simultaneously with large currents, then heating power and productivity are improved, but switching loss increases and device reliability deteriorates
Solution Approach 1:
The patent applies periodic action by alternately driving different combinations of heating coils in a cyclic manner. The control device switches between multiple driving patterns (e.g., driving first and second coils simultaneously, then first and third coils, then second and third coils) in a repeating sequence. This periodic alternation allows the system to maintain high overall heating power while giving each inverter circuit periodic rest periods, thereby reducing cumulative switching loss and thermal stress on individual components.
Solution Approach 2:
The patent implements dynamics by making the driving pattern adaptive and changeable over time. The control device dynamically switches between different coil activation patterns based on timing signals, creating a time-varying operating regime. This dynamic approach allows the system to optimize power distribution continuously, ensuring high productivity when needed while periodically reducing switching stress on any single inverter circuit, thus resolving the contradiction between sustained high power and reduced switching loss.
2Power
If multiple heating coils are driven simultaneously, then heating capability is improved, but current imbalance and resonance occur reducing device stability
Solution Approach 1:
The control device employs periodic action by systematically alternating between different coil activation patterns over time. Instead of continuously driving all coils simultaneously (which causes current imbalance), the system cycles through patterns where different subsets of coils are active in different time periods. This periodic switching prevents sustained current imbalance and avoids resonance conditions that would occur with continuous simultaneous driving of all coils.
Solution Approach 2:
The patent applies dynamics by implementing time-varying control of coil activation. The driving patterns are not static but change continuously according to timing signals, creating a dynamic current distribution that adapts over time. This dynamic approach ensures that no single coil or inverter circuit is continuously overloaded, maintaining current balance while preserving overall heating capability through the cumulative effect of alternating high-power patterns.
3Productivity
If inverter circuits operate continuously at high load, then productivity is improved, but device lifespan decreases due to increased stress
Solution Approach 1:
The patent applies periodic action by implementing cyclic alternation between different inverter circuit operating states. The control device schedules periods where different inverter circuits are active while others are in lower-stress states, creating a repeating pattern that distributes cumulative stress evenly across all components. This periodic rest-cycles approach allows the system to maintain high average productivity while ensuring no single inverter circuit operates continuously at maximum load, thereby extending overall device lifespan.
Solution Approach 2:
The control system implements dynamics by continuously varying the operating state of inverter circuits over time. Rather than maintaining a static high-load state, the system dynamically switches between different activation patterns, creating time-varying stress profiles. This dynamic operation ensures that while the overall heating output remains high, individual inverter circuits experience periodic reduction in stress, preventing premature failure and extending device lifespan through load distribution over time.
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 switching loss and stabilizes the lifespan of the device by equalizing current flow through half-bridge circuits, preventing resonance and maintaining optimal power distribution across heating coils.
Implementation Method 1
An induction heating method is a method of causing a heating object to be heated by generating eddy currents in the heating object including a metal component by using a magnetic field generated around a coil when high frequency power of a certain magnitude is applied to the coil
Implementation Method 2
causing a heating object to be heated by generating eddy currents in the heating object including a metal component
Implementation Method 3
heating a heating object by generating eddy currents
Data Source
AI summary
An induction heating device includes a first heating coil and a second heating coil, a first half-bridge circuit connected to an end of the first heating coil, a second half-bridge circuit connected to an end of the second heating coil, a third half-bridge circuit connected to the respective other ends of the first heating coil and the second heating coil, and a control device configured to drive the first half-bridge circuit and the second half-bridge circuit out-of-phase. The control device alternately executes a first mode and a second mode according to a defined time ratio, wherein in the first mode, the second half-bridge circuit and the third half-bridge circuit are controlled to be driven in-phase, and in the second mode, the first half-bridge circuit and the third half-bridge circuit are controlled to be driven in-phase.