Mid-Pack Relay Voltage Disconnect Architecture
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Solution Overview
Problem
Existing voltage disconnect architectures for high-voltage battery systems are cumbersome due to the need for heavy-duty mechanical contactors and pre-charge resistors, which increase size, weight, and cost while posing risks of damage from high inrush currents.
Innovation Solution
A voltage disconnect architecture that employs a mid-pack low-power relay and semiconductor switches to divide voltage across the battery pack, eliminating the need for pre-charge resistors and reducing the size and cost of fuses, with a sequencer circuit for coordinated current flow during faults.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-voltage mechanical contactors and pre-charge resistors are used in the voltage disconnect architecture, then galvanic isolation and inrush current protection are achieved, but the size, weight, and cost of the system increase
Solution Approach 1:
The patent replaces heavy-duty mechanical contactors with semiconductor switches (MOSFETs or IGBTs) that provide the same galvanic isolation function without the mechanical moving parts. The semiconductor-based disconnect architecture eliminates the need for pre-charge resistors by using the intrinsic resistance of the semiconductor switches during their turn-on transition, thereby reducing size, weight, and cost while maintaining reliability.
2Strength
If heavy-duty mechanical contactors are used to handle high inrush currents, then the system can withstand transient currents, but the cost and size of the disconnect system increase
Solution Approach 1:
The patent changes the operational parameters of the semiconductor switches by controlling their turn-on speed and using parallel switching sequences. The sequencer circuit coordinates the turn-on of multiple semiconductor switches in a controlled manner, distributing the inrush current over time and among multiple devices, thereby protecting them without requiring oversized, expensive components.
3Reliability
If pre-charge resistors are used to limit inrush current, then contactor damage is prevented, but the complexity and cost of the circuit increase
Solution Approach 1:
The patent extracts and eliminates the pre-charge resistor component from the circuit by using the inherent resistance characteristics of semiconductor switches during their turn-on phase. The controlled switching sequence inherently limits inrush current without requiring separate protective components, thereby reducing circuit complexity and cost while maintaining contactor protection.
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 solution reduces the size and cost of the disconnect system, provides galvanic isolation, and maintains internal short circuit protection without pre-charging, while optimizing hardware and reducing transient high-current and voltage ratings on HV contactors.
Implementation Method 1
The mid-pack LP relay, which is a high-voltage/current LP relay, is strategically placed in conjunction with the pack fuse so as to divide a voltage across the battery pack when the mid-pack LP relay is commanded open.
Implementation Method 2
a pair of semiconductor switches positioned in electrical parallel with the mid-pack LP relay. Additionally, a sequencer circuit is configured to coordinate a flow of electrical current through the semiconductor switches and the mid-pack LP relay
Implementation Method 3
The LP relays can selectively open to provide galvanic isolation in the system, e.g., when the system is turned off.
Data Source
AI summary
A disconnect architecture for use with a system having a battery pack and positive and negative bus rails includes a mid-pack low-power (LP) relay, a fuse, semiconductor switches, and a sequencer circuit. The mid-pack LP relay is positioned between the rails at a mid-stack point of the battery pack, and divides a voltage across the battery pack when commanded open. The fuse is positioned between the mid-pack LP relay and the positive bus rail, and opens in response to a dead short condition of the system. The semiconductor switches are positioned in electrical parallel with the mid-pack LP relay. The sequencer circuit selectively turns on the semiconductor switches and thereby coordinates a flow of electrical current through the semiconductor switches and the mid-pack LP relay in response to a detected partial short condition of the system. A system includes the battery pack, bus rails, and disconnect architecture.