IGBT Drive Voltage Switching for Low-Power Induction Heating
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Solution Overview
Problem
Electromagnetic heating apparatuses face issues with high instant current peaks and heat dissipation problems when operating at low power, leading to potential damage to IGBTs and noise during turn-on, especially in discontinuous heating modes.
Innovation Solution
A heating control circuit with a driving and transforming unit that adjusts the driving voltage of the power switch transistor, allowing it to turn on via a voltage-changing method, reducing open current and noise, and preventing hard turn-on damage by controlling the transistor's operation before the zero-crossing point of the AC power source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the electromagnetic heating apparatus operates at low power using a single IGBT in parallel resonance mode, then the heating function is maintained, but high instant current peaks occur at IGBT turn-on which may damage the transistor
Solution Approach 1:
The patent applies dynamics by making the driving voltage of the IGBT changeable over time. A driving voltage changing unit is introduced that dynamically adjusts the driving voltage from a first voltage (during voltage buildup) to a second voltage (during normal operation). This dynamic voltage adjustment prevents hard turn-on current peaks while maintaining reliable operation across different power levels.
Solution Approach 2:
The patent changes the driving voltage parameter of the IGBT based on operating conditions. The driving voltage changing unit switches between a first driving voltage (lower, during startup/voltage buildup) and a second driving voltage (higher, during normal operation). This parameter change resolves the contradiction by preventing excessive turn-on current while maintaining effective heating control.
2Power
If the IGBT is driven with high power to achieve effective heating, then heating performance is improved, but the IGBT emits great heat requiring strengthened heat dissipation
Solution Approach 1:
The patent uses dynamic driving voltage adjustment to optimize the balance between heating performance and heat generation. By switching between a first driving voltage (lower, during voltage buildup) and a second driving voltage (higher, during normal operation), the system achieves effective heating while reducing unnecessary heat emission during critical phases like turn-on.
Solution Approach 2:
The patent applies preliminary action by building up the driving voltage gradually through a first voltage phase before switching to full power. The driving voltage changing unit first applies a lower first voltage to establish stable oscillation, then transitions to the second voltage for full heating power. This preliminary voltage buildup prevents sudden high current peaks and reduces heat stress on the IGBT.
3Use of energy by moving object
If discontinuous heating mode is used to achieve low power operation, then power consumption is reduced, but hard turn-on phenomenon occurs due to filter capacitor voltage which may damage the IGBT
Solution Approach 1:
The patent resolves this contradiction by dynamically adjusting the driving voltage based on the heating mode. The driving voltage changing unit detects whether the system is in continuous or discontinuous mode and applies appropriate voltage levels. In discontinuous mode, it uses a first driving voltage during voltage buildup to prevent hard turn-on, while maintaining the ability to switch to second driving voltage when needed, thus protecting the IGBT while enabling low power operation.
Solution Approach 2:
The patent employs feedback mechanisms where the control unit monitors the operating state and adjusts the driving voltage accordingly. The driving voltage changing unit receives feedback about the voltage buildup state and switching timing, and dynamically adjusts between first and second driving voltages to prevent hard turn-on in discontinuous mode while maintaining heating effectiveness.
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 solution reduces the risk of damaging the power switch transistor, minimizes noise during turn-on, and broadens the range of heating power by effectively managing the voltage and current in the electromagnetic heating apparatus.
Implementation Method 1
a voltage zero-crossing detecting unit, in which the voltage zero-crossing detecting unit is configured to detect a voltage zero-crossing signal of an alternating current power source input to the electromagnetic heating apparatus
Implementation Method 2
a resonance heating unit; a power switch transistor configured to control the resonance heating unit to perform resonance work
Implementation Method 3
an electromagnetic resonance circuit with a single insulated gate bipolar transistor (IGBT for short) generally adopts a parallel resonance mode
Implementation Method 4
a rectifier and filter unit, in which the rectifier and filter unit is configured to perform rectifying and filtering processing on the alternating current power source which is provided to the resonance heating unit
Implementation Method 5
a rectifier and filter unit, in which the rectifier and filter unit is configured to perform rectifying and filtering processing on the alternating current power source
Implementation Method 6
a driving and transforming unit, in which the driving and transforming unit is coupled to the driving end of the power switch transistor so as to change a driving voltage of the power switch transistor
Data Source
Figure 1~2
Figure 3~4A
Figure 4B~5
AI summary
Disclosed are an electromagnetic heating device and a heating control circuit thereof, and a low power heating control method. The heating control circuit comprises: a voltage zero-crossing detection unit for detecting a voltage zero-crossing signal of an alternating current power source; a resonance heating unit; a rectification and filtering unit; a power switch tube; a drive unit, connected to a drive end of the power switch tube to drive the power switch tube to be turned on and off; a drive voltage transformation unit, connected to the drive end of the power switch tube to change a drive voltage of the power switch tube; and a main control unit for controlling the power switch tube to operate under the drive of a first drive voltage if determining, according to the voltage zero-crossing signal, that is before the zero-crossing point of the alternating current power source, and controlling, when a collector voltage of the power switch tube oscillates to the minimum, the power switch tube to operate under the drive of a second drive voltage, such that the power switch tube is started with a variable voltage, thereby reducing the damage risk of the power switch tube and reducing tum-on noises.