Flyback Diode Control for Unidirectional Energy Transmission
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In power switching apparatuses, the existing control methods for free-wheeling diodes can lead to negative inductance currents when operating in discontinuous current mode, causing energy to be transmitted from the output end to the input end, which compromises the reliability of the circuit system.
Innovation Solution
A control method that dynamically adjusts the pulse width values of the free-wheeling diode based on inductance current and volt-second balance laws to ensure unidirectional energy transmission, using different pulse width values for continuous and discontinuous current modes to prevent negative inductance currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the control apparatus controls conduction of the free-wheeling diode according to the principle that the pulse width of the main control transistor is complementary to the pulse width of the free-wheeling diode, then the control system maintains a simple control logic, but negative inductance current appears in discontinuous current mode causing energy to transmit from output end to input end
Solution Approach 1:
The patent applies dynamics by transitioning from a static complementary pulse width control method to a dynamic control method that adapts to different current modes. The control apparatus dynamically determines whether the power switching apparatus is operating in continuous current mode or discontinuous current mode, and adjusts the free-wheeling diode conduction control accordingly. In discontinuous current mode, the free-wheeling diode is controlled to conduct for a duration that ensures inductance current returns to zero without forcing complementary timing, thereby preventing negative inductance current while maintaining reliable unidirectional energy transmission.
2Productivity
If the sum of pulse width values of main control transistor and free-wheeling diode is less than the switching period in discontinuous current mode, then the power switching apparatus operates efficiently in DCM, but the conventional complementary control principle causes negative inductance current and energy backflow
Solution Approach 1:
The patent applies parameter changes by modifying the control parameters of the free-wheeling diode based on the detected current mode. When discontinuous current mode is detected (where the sum of main control transistor pulse width and free-wheeling diode pulse width is less than the switching period), the control apparatus adjusts the free-wheeling diode conduction duration to match the actual current waveform characteristics rather than enforcing a fixed complementary relationship. This parameter adaptation eliminates negative inductance current while preserving the efficiency benefits of discontinuous current mode operation.
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 1E
AI summary
Embodiments of this application provide a free-wheeling diode control method and apparatus and a power switching apparatus. The method includes: determining whether a sum of a first pulse width value of a free-wheeling diode obtained according to an inductance current law and a third pulse width value of a main control tube meets a first preset condition, and obtaining a determining result; and further determining, according to the determining result, to control conduction of the free-wheeling diode according to the first pulse width value or a second pulse width value of the free-wheeling diode obtained according to a volt-second balance law. In the free-wheeling diode control method and apparatus and the power switching apparatus that are provided in the embodiments of this application, conduction of the free-wheeling diode may be controlled by flexibly using different pulse width values according to different running scenarios of the power switching apparatus, so that energy in the power switching apparatus is always unidirectionally transmitted from an input end to an output end. In this way, reliability of a circuit system is ensured.