Induction Heating Power Supply Intermittent PWM Control
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Solution Overview
Problem
Electromagnetic induction heating devices experience noise production and increased switching loss when performing intermittent PWM control, particularly when transitioning between control periods, due to sudden changes in electromagnetic flux, which can lead to deformation of the heating component and overheating of the switching element.
Innovation Solution
Implementing uneven gradual intermittent control, where the electric power supplied to the resonant circuit gradually increases in more steps than it decreases, during the transition from the PWM control stop period to the execution period, and vice versa, to reduce noise and switching loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If intermittent PWM control is performed to reduce switching loss, then switching loss is reduced, but noise is produced due to sudden changes in electromagnetic flux
Solution Approach 1:
The control device performs preliminary action by gradually changing the duty cycle before completely stopping or starting PWM control. When transitioning from control to stop, the duty cycle is gradually reduced to a predetermined value before being set to zero. When transitioning from stop to control, the duty cycle is gradually increased from zero to the target value. This preliminary gradual adjustment prevents sudden electromagnetic flux changes that cause noise while maintaining the intermittent control structure that reduces switching loss.
Solution Approach 2:
The control device applies dynamics by making the duty cycle adjustable and transitionable through multiple stages rather than fixed or abrupt changes. The duty cycle dynamically transitions from the target value to a predetermined value, then to zero, and vice versa, creating a smooth, adaptive control profile that balances switching loss reduction with noise prevention based on real-time operational requirements.
2Loss of energy
If the duty cycle is suddenly changed during intermittent control, then switching loss is reduced, but the heating component deforms due to rapid electromagnetic flux changes
Solution Approach 1:
The control device performs preliminary action by gradually changing the duty cycle before completely stopping or starting PWM control. When transitioning from control to stop, the duty cycle is gradually reduced to a predetermined value before being set to zero. When transitioning from stop to control, the duty cycle is gradually increased from zero to the target value. This preliminary gradual adjustment prevents sudden electromagnetic flux changes that cause noise while maintaining the intermittent control structure that reduces switching loss.
Solution Approach 2:
The control device applies dynamics by making the duty cycle adjustable and transitionable through multiple stages rather than fixed or abrupt changes. The duty cycle dynamically transitions from the target value to a predetermined value, then to zero, and vice versa, creating a smooth, adaptive control profile that balances switching loss reduction with noise prevention based on real-time operational requirements.
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 constrains switching loss occurrence and prevents noise production by smoothing the power transitions, ensuring the switching element operates within safe temperature thresholds and reducing perceived noise levels.
Implementation Method 1
an electromagnetic induction heating device that controls electric power supplied to a resonant circuit that is connected to a switching element by performing control of ON and OFF switching by a switching element, and has an inductor and a capacitor, and that performs electromagnetic induction of heating a component subject to heating through electromagnetic flux in the inductor
Data Source
AI summary
An electromagnetic induction heating apparatus comprises: a resonance circuit that includes a inductor and a capacitor; a direct-current electric power supply; and a switching element performing ON and OFF switching of electric power supplied to the resonance circuit by the direct-current electric power supply; performs intermittent control of the electric power supply by controlling the ON and OFF switching at regular intervals, and by performing control to stop the electric power supply when not controlling the ON and OFF switching, wherein during the intermittent control, the switching control unit performs gradual control such that, upon beginning the control of the ON and OFF switching, the electric power supply gradually increases to reach a target value, and upon stopping the control of the ON and OFF switching, the electric power supply gradually decreases from the target value until stopping, such that the gradual decrease involves fewer steps than the gradual increase.