DC Link Circuit Discharge Control for Thermal Management
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Solution Overview
Problem
Existing DC link circuits in electric power converters face overheating issues due to the thermal load from discharging units, which is not adequately managed by splitting the discharging current between multiple units.
Innovation Solution
The DC link circuit employs a control unit to manage the discharging current by allowing it to flow during the on-time and reducing it during the off-time, with offset on-times and periodic control signals to ensure balanced heat dissipation, using a voltage-controlled current source and a heat sink for efficient cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If multiple discharging units are used in parallel to split the discharging current, then the thermal load of each discharging unit is reduced, but the discharging units still overheat due to continuous current flow
Solution Approach 1:
The patent applies periodic action by switching the discharging units on and off in alternating intervals. Each discharging unit operates periodically rather than continuously, allowing it to dissipate heat during off periods. The control unit alternates between first and second discharging units, ensuring that while one unit is active (converting electrical energy to thermal energy), the other is inactive (cooling down), thus preventing overheating while maintaining continuous discharging capability.
2Productivity
If discharging current flows continuously through discharging units, then the capacitor discharges rapidly, but the discharging units generate excessive heat
Solution Approach 1:
The patent implements periodic action by controlling the switching elements to alternately connect the first and second discharging units to the smoothing capacitor in periodic intervals. This ensures that the discharging process continues without interruption (maintaining productivity) while each discharging unit receives periodic rest periods to cool down (reducing temperature). The control unit manages the switching timing to optimize both discharging speed and thermal management.
3Temperature
If switching elements are used to control discharging units alternately, then heat dissipation is balanced, but the control system complexity increases
Solution Approach 1:
The patent uses periodic action with a straightforward alternating switching pattern controlled by a control unit. The control unit generates switching signals that alternately activate the first and second discharging units based on predetermined time intervals. This periodic control approach achieves balanced heat dissipation while keeping the control logic relatively simple, as it relies on regular alternation rather than complex real-time temperature monitoring and adjustment.
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 significantly reduces overheating by allowing discharging units to cool down during off-times, achieving a substantially continuous discharging behavior and balanced heat dissipation among units, with the average discharging current during off-times being at most 10% of the on-time average.
Implementation Method 1
two discharging units being connected in parallel... each having a resistor... converting the electric energy stored in the smoothing capacitor into heat
Implementation Method 2
a heat sink for efficient cooling
Implementation Method 3
a heat sink for efficient cooling
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
DC link circuit (5) for an electric power converter (1), comprising a smoothing capacitor (12) and at least two discharging units (15, 16, 17) being connected in parallel, with a control unit (18), which is configured to provide control signals (22, 23, 24) each controlling one discharging unit (15, 16, 17) and causing the discharging unit (15, 16, 17) to allow a flow of a discharging current (27) through the discharging unit (15, 16, 17) from the smoothing capacitor (12) during an on-time (29) and to suppress or reduce the flow of the discharging current during an off-time (30) , wherein the on-times (29) have a temporal offset to each other.