AC Chopper Inductive Energy Release Path
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing AC choppers face challenges in inhibiting surge voltages generated in reactors due to inductive energy accumulation, especially when the load current or power source current includes ripple components, and this can lead to breakdown of bidirectional switches, particularly near zero cross conditions, requiring complex control circuits and increased dead time to manage harmonics.
Innovation Solution
The AC chopper divides the voltage period into specific periods and controls the switching elements to ensure a release path for inductive energy, preventing surge voltages by alternately switching ON/OFF the first and second bidirectional switches, thereby maintaining a stable energy flow and reducing the need for complex gate signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If bidirectional switches are simultaneously switched OFF in dead time, then voltage control is achieved, but surge voltage is generated due to cut-off inductive energy release path
Solution Approach 1:
A diode is introduced as an intermediary component connected in parallel with the reactor. When bidirectional switches are simultaneously turned OFF during dead time, the diode provides an alternative path for inductive energy release, preventing surge voltage generation while maintaining voltage control functionality
Solution Approach 2:
The harmful inductive energy that would otherwise cause surge voltage is converted into a beneficial effect by routing it through the diode's forward conduction path. The energy is safely dissipated through the diode rather than causing breakdown of switching elements
2Object-affected harmful factors
If complex control circuits are used to detect current polarity for surge inhibition, then surge voltage is prevented, but device complexity increases
Solution Approach 1:
The diode automatically activates based on the polarity of inductive energy without requiring external detection or control. When switches turn OFF and inductive energy needs release, the diode's inherent forward bias characteristic automatically provides the release path, eliminating the need for complex polarity detection circuits
3Object-generated harmful factors
If dead time is increased to manage harmonics, then harmonic formation is reduced, but productivity decreases
Solution Approach 1:
The function of providing an inductive energy release path is extracted from the switching control system and implemented through the passive diode component. This allows dead time to be minimized for high-speed switching while the diode independently handles energy release, separating harmonic management from switching timing constraints
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 inhibits surge voltages in reactors, even with ripple components in the current, without requiring complex control circuits and minimizes harmonic formation, ensuring reliable operation and reduced risk of switch breakdown.
Implementation Method 1
the bidirectional switch 2 and the bidirectional switch 3 are repeatedly and alternately ON/OFF operated on the basis of pulse-width-modulated gate signals
Implementation Method 2
the path for releasing the inductive energy accumulated in the reactor L is cut off. At this time, a surge voltage is generated at both terminals of the reactor L
Data Source
Figure 1
Figure 2(a)~2(c)
Figure 3
AI summary
Provided are a first period in which a voltage Vin is equal to or higher than a positive first reference voltage, a second period in which the voltage Vin is equal to or lower than a negative second reference voltage, and a third period in which the voltage Vin is between the first reference voltage and the second reference voltage. In the first period, second and third switching elements are switched ON, and first and fourth switching elements are alternately switched ON/OFF. In the second period, the first and fourth switching elements are switched ON, and the second and third switching elements are alternately switched ON/OFF. In the third period, the first and second switching elements are switched ON, and the third and fourth switching elements are switched OFF. The voltage Vin is stepped down to a predetermined AC voltage Vo while ensuring a release path for inductive energy accumulated in a reactor.