Bus Capacitor Discharge Control in DC-DC Converters
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Solution Overview
Problem
Conventional discharging methods for bus capacitors in DC-DC converters and inverters require additional circuits, leading to energy loss, low efficiency, and increased hardware costs, while also posing design challenges for small volume and high-density modular systems.
Innovation Solution
A discharging method that utilizes a switch and reactor to form a current loop with the bus capacitor after power-off, controlling the switch based on voltage thresholds to discharge the capacitor without an additional discharging circuit, thereby eliminating the need for extra hardware and reducing energy loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a discharging resistor with high resistance is directly connected in parallel to the bus capacitor, then the bus capacitor can discharge continuously, but this results in energy loss and low efficiency during system operation
Solution Approach 1:
The patent applies the dynamics principle by making the discharging circuit dynamic rather than static. A switching unit is introduced to control the connection of the discharging unit to the bus capacitor based on system state. The switching unit is turned on during power-off state to enable discharging, and turned off during operation to prevent energy loss, thus making the discharging function adaptive to different operating conditions.
Solution Approach 2:
The patent implements periodic action through the switching unit that periodically connects and disconnects the discharging circuit based on power state. The controller periodically activates the switching unit during power-off to discharge the capacitor, and deactivates it during operation, creating a periodic on-off pattern that ensures discharging only when necessary.
2Reliability
If a switching unit and discharging unit connected via the switching unit are used, then discharging can be controlled during power-off state, but two discharging circuits are required in high-voltage DC-DC converter, resulting in high hardware cost and large structural space
Solution Approach 1:
The patent applies universality by designing the discharging circuit to serve multiple voltage levels. The same discharging unit with switching unit can be used in both high-voltage and low-voltage DC-DC converters through appropriate configuration. The discharging unit is connected to the bus capacitor via the switching unit, and the controller manages the switching based on power state, allowing one circuit to handle multiple voltage scenarios without requiring separate discharging circuits for each voltage level.
Solution Approach 2:
The patent merges the discharging function with the existing controller and switching unit infrastructure. Rather than adding completely separate discharging circuits, the invention integrates the discharging unit control into the existing controller architecture, combining multiple functions (switching control, discharging management, power state detection) into a unified system that reduces overall hardware requirements.
3Reliability
If conventional discharging circuits are used, then the bus capacitor can be discharged, but insulation, heat dissipation and installation methods need to be taken into account for high-voltage applications
Solution Approach 1:
The patent introduces the switching unit as an intermediary between the controller and the discharging unit. This intermediary component enables precise control over when the discharging circuit is activated, allowing the system to manage heat dissipation by limiting discharging operations to only when necessary (power-off state). The switching unit acts as a mediator that isolates the high-voltage bus capacitor from the discharging resistor during operation, preventing unnecessary heat generation while enabling controlled discharge when safe.
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 method effectively discharges the bus capacitor without additional circuits, avoiding energy loss and hardware costs, and aligns with design trends for small volume and high-density modular systems by integrating the discharging function within the existing controller.
Implementation Method 1
controlling, in a case that the voltage across the bus capacitor meets the preset condition, the switch to be turned on or turned off to cause the bus capacitor, the switch and the reactor to form a current loop
Implementation Method 2
a discharging resistor with a high resistance is directly connected in parallel to a bus capacitor
Data Source
Figure 1
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AI summary
A discharging method of a bus capacitor, a controller, a DC-DC converter and an inverter are provided. After a DC-DC converter or an inverter is powered off, in a case that a detected voltage across a bus capacitor of the DC-DC converter or the inverter is determined to meet a preset condition, a switch of the DC-DC converter or the inverter is controlled to be turned on or turned off to cause the bus capacitor, the switch, and a reactor of the DC-DC converter or the inverter to form a current loop, until the voltage does not meet the preset condition. Based on the method, discharging function is achieved for the bus capacitor after the DC-DC converter or the inverter is powered off, without the need for an additional discharging circuit, which solves problems caused by the additional discharging circuit required in the conventional technology.