Induction Heating Switch Stress Reduction via Controlled Turn-Off
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Solution Overview
Problem
Induction heating devices face challenges with switch stress and noise issues due to over-currents, which can lead to voltage spikes and increased manufacturing costs from the use of Free Wheeling Diodes, and occupy significant circuit space.
Innovation Solution
An induction heating device design that includes a working coil unit with parallel-connected coils, an inverter unit for resonance current application, and an over-current protection unit with a control system to manage semiconductor switches, eliminating the need for Free Wheeling Diodes and relays, thereby reducing switch stress and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Free Wheeling Diodes are added to reduce switch stress, then switch stress is reduced, but heat generation increases and manufacturing cost increases
Solution Approach 1:
The patent removes the Free Wheeling Diode from the circuit by implementing a controlled turn-off sequence where the semiconductor switch is turned off before the inverter switch. This extraction eliminates the diode's heat generation and associated manufacturing costs while maintaining switch stress reduction through proper switching control.
Solution Approach 2:
The patent applies preliminary action by turning off the semiconductor switch before turning off the inverter switch. This predetermined switching sequence prevents over-current flow and reduces switch stress without requiring a Free Wheeling Diode, thereby avoiding the heat generation and cost issues associated with adding such a diode.
2Reliability
If Free Wheeling Diodes are added to reduce switch stress, then switch stress is reduced, but manufacturing cost increases
Solution Approach 1:
The patent removes the Free Wheeling Diode from the circuit by implementing a controlled turn-off sequence where the semiconductor switch is turned off before the inverter switch. This extraction eliminates the diode's heat generation and associated manufacturing costs while maintaining switch stress reduction through proper switching control.
Solution Approach 2:
The patent applies preliminary action by turning off the semiconductor switch before turning off the inverter switch. This predetermined switching sequence prevents over-current flow and reduces switch stress without requiring a Free Wheeling Diode, thereby avoiding the heat generation and cost issues associated with adding such a diode.
3Reliability
If relays and Free Wheeling Diodes are used for switching control, then switching protection is provided, but circuit volume increases
Solution Approach 1:
The patent removes both the relay and Free Wheeling Diode from the circuit by implementing a controlled turn-off sequence where the semiconductor switch is turned off before the inverter switch. This extraction eliminates the need for additional protective components, significantly reducing circuit volume while maintaining switching protection through proper control sequencing.
Solution Approach 2:
The patent applies preliminary action by turning off the semiconductor switch before turning off the inverter switch. This predetermined switching sequence provides inherent protection against over-current and voltage spikes without requiring additional protective components like relays or diodes, thereby minimizing circuit volume.
4Adaptability or versatility
If semiconductor switches are used for coil switching, then independent output control is achieved, but switch stress increases due to over-current
Solution Approach 1:
The patent applies preliminary action by turning off the semiconductor switch before turning off the inverter switch. This predetermined switching sequence prevents over-current flow and reduces switch stress without requiring a Free Wheeling Diode, thereby avoiding the heat generation and cost issues associated with adding such a diode.
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 design enables independent output control of multiple working coils, reduces switch stress and noise, prevents voltage spikes, and minimizes circuit volume, enhancing product reliability and user convenience by eliminating Free Wheeling Diodes and relays.
Implementation Method 1
an inverter unit (IV) configured to perform a switching operation by applying a resonance current to at least one of the first working coil (WC1) or the second working coil (WC2)
Implementation Method 2
a first semiconductor switch (S1) connected to the first working coil (WC1) and configured to turn on and turn off the first working coil (WC1)
Implementation Method 3
an over-current protection unit (230) that is connected to the first semiconductor switch (S1), that is configured to generate first information based on a current that flows in the first semiconductor switch (S1)
Data Source
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AI summary
An induction heating device includes first and second working coils connected electrically in parallel, an inverter unit configured to switch at least one of the first working coil or the second working coil, an inverter driving unit connected to the inverter unit; a first semiconductor switch connected to the first working coil, a first semiconductor switch driving unit connected to the first semiconductor switch, an over-current protection unit connected to the first semiconductor switch, configured to generate information based on a current that flows in the first semiconductor switch, and configured to, based on the information, determine whether to turn off the inverter driving unit, and a control unit that is configured to receive the information, and determine, based on the information, whether to block a pulse signal to the inverter driving unit and whether to turn off the first semiconductor switch driving unit.