Bridge Rectifier Discharge Control for On-Board Charger Capacitors
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Solution Overview
Problem
Existing on-board chargers for automotive applications face challenges in meeting increased efficiency requirements and higher power density, particularly in discharging components safely during loss of communication or critical faults, and in efficiently managing capacitor discharge without additional hardware.
Innovation Solution
A system comprising an AC-DC converter with a bulk capacitor and a DC-DC converter, including a bridge rectifier and filter capacitor, controlled by controllers to manage the discharge of capacitors in both grid-to-battery and battery-to-grid operations, ensuring safe discharge below HV safety values and efficient energy transfer without additional hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If capacitor discharge control is implemented without additional hardware, then device complexity is reduced, but discharge safety and efficiency may be compromised
Solution Approach 1:
The bridge rectifier switch is made multi-functional by using it for both normal rectification operations and capacitor discharge operations. The controller activates the bridge rectifier switch to discharge the filter capacitor to the bulk capacitor, eliminating the need for dedicated discharge hardware while maintaining discharge safety through controlled operation.
Solution Approach 2:
The system uses its existing components (bridge rectifier switch, filter capacitor, bulk capacitor) to perform the discharge function without requiring external or additional hardware. The controller manages the discharge process by controlling the bridge rectifier switch, allowing the system to service its own safety requirements using internal resources.
2Device complexity
If capacitor discharge is controlled using existing components, then device complexity is reduced, but energy transfer efficiency may deteriorate
Solution Approach 1:
The bridge rectifier switch serves dual purposes: normal rectification during charging operations and controlled discharge during fault conditions. This multi-functionality maintains energy efficiency by utilizing existing low-loss components for discharge rather than introducing additional energy-dissipating discharge resistors or circuits.
Solution Approach 2:
The bulk capacitor acts as an intermediary energy storage element that receives discharged energy from the filter capacitor. This intermediary approach allows energy to be transferred and managed efficiently through the existing capacitor-coupled circuitry rather than being dissipated, maintaining high discharge efficiency.
3Power
If power density is increased to meet efficiency requirements, then charging speed improves, but safety risks during fault conditions increase
Solution Approach 1:
The system implements preliminary discharge control by detecting fault conditions (loss of communication or critical faults) and immediately activating the bridge rectifier switch to discharge capacitors before hazardous voltage levels can persist. This preliminary action ensures that high power density operation does not compromise safety, as discharge mechanisms are ready and controlled.
Solution Approach 2:
The controller continuously monitors system status including communication integrity and fault conditions. When faults are detected, the controller provides feedback control by activating the bridge rectifier switch to discharge capacitors, creating a closed-loop safety mechanism that responds to actual system conditions rather than relying on fixed timing or conservative design margins.
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
The system effectively discharges capacitors safely and efficiently, maintaining high efficiency and power density while ensuring HV safety, without the need for additional hardware, thus addressing the limitations of existing technologies.
Implementation Method 1
a filter capacitor; wherein the filter capacitor is configured to filter a high frequency ripple from electric power supplied to the battery
Implementation Method 2
a bridge rectifier connected to the secondary side of the one or more transformers, the bridge rectifier including a bridge rectifier switch
Implementation Method 3
an alternating current (AC) to direct current (DC) converter (AC-DC converter) including a bulk capacitor, the AC-DC converter connectable to a line voltage
Implementation Method 4
a DC to DC converter (DC-DC converter) connected to the AC-DC converter, the DC-DC converter including: one or more transformers
Data Source
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AI summary
A system includes: an alternating current (AC) to direct current (DC) converter (AC-DC converter) including a bulk capacitor, the AC-DC converter connectable to a line voltage; a DC to DC converter (DC-DC converter) connected to the AC-DC converter, the DC-DC converter including: one or more transformers having a secondary side connectable to a battery, a bridge rectifier connected to the secondary side of the one or more transformers, the bridge rectifier including a bridge rectifier switch, and a filter capacitor; and one or more controllers configured to control an operation of the bridge rectifier switch to control a discharge of the filter capacitor to the bulk capacitor.