Flying Capacitor Battery Voltage Detector Temperature Dispersion
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Solution Overview
Problem
Conventional flying capacitor type battery voltage detectors face issues with signal-to-noise ratio degradation due to temperature-dependent on-state resistances of analog switches, electromagnetic and electrostatic coupling, and increased wiring resistances, leading to inaccurate voltage readings and reduced efficiency in high-voltage battery packs.
Innovation Solution
The design involves a multiplexer with portions on both the front and back surfaces of the circuit substrate, connected via floating lines, which reduces temperature dispersion and noise interference, and uses photo MOS switches with controlled on-state resistances to improve signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large number of photo MOS switches are disposed in discrete units on a circuit substrate to detect cell voltages, then the battery pack voltage detection capability is achieved, but the on-state resistances of the switches vary widely due to temperature dispersion, degrading the signal-to-noise ratio
Solution Approach 1:
The patent applies three-dimensional integration by disposing the multiplexer in two layers (front and back surfaces) of the circuit substrate. The first photo MOS switches are disposed on the front surface and the second photo MOS switches are disposed on the back surface, with corresponding switches substantially lying over each other. This spatial arrangement reduces the area each switch occupies and minimizes temperature dispersion, thereby stabilizing on-state resistances and improving signal-to-noise ratio.
2Adaptability or versatility
If photo MOS switches are disposed in a wide area of the circuit substrate, then all cell voltages can be detected, but the temperature dispersion across the substrate increases, causing variation in on-state resistances
Solution Approach 1:
By transitioning from a two-dimensional layout to a three-dimensional stacked configuration, the patent reduces the horizontal spread of switches on the circuit substrate. The multiplexer is distributed across two layers with corresponding switches positioned vertically above each other, concentrating the thermal load in smaller areas and improving temperature uniformity across the substrate.
3Adaptability or versatility
If the multiplexer is disposed in a wide area to accommodate many photo MOS switches, then all cells can be monitored, but the wiring lengths increase, increasing wiring resistances and noise
Solution Approach 1:
The patent reduces wiring lengths by implementing the multiplexer in a two-layer configuration. Switches and their associated wiring are concentrated in vertically stacked positions rather than spread out horizontally, significantly reducing the path length for signal transmission and lowering both wiring resistance and electromagnetic noise.
4Reliability
If discrete photo MOS switches are used instead of integrated circuits, then high voltage isolation is achieved, but the circuit size and complexity increase enormously
Solution Approach 1:
The patent merges multiple discrete photo MOS switches into an integrated circuit configuration while maintaining high voltage isolation through the use of a circuit substrate with controlled impedance and grounding structures. The multiplexer integrates switch control and signal routing functions, dramatically reducing circuit complexity compared to fully discrete implementations.
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 configuration enhances the signal-to-noise ratio by minimizing temperature-induced resistance variations and noise interference, resulting in more accurate and consistent voltage readings across the battery pack cells.
Implementation Method 1
Each photo MOS switch requires both a light emitting device (LED) and a silicon photo detector
Implementation Method 2
a flying capacitor holds an output voltage of each selected cell
Implementation Method 3
a differential amplifier detects the output voltage of the cell sent from the flying capacitor through an output side analog switch
Data Source
AI summary
In a flying capacitor type battery voltage detector on a circuit substrate, a large number of photo MOS switches having performance highly depending from temperature are dividedly disposed on front and back surfaces of the circuit substrate such that the photo MOS switches of the back surface are lying over the photo MOS switches of the front surface. Each of pairs of photo MOS switches connects a pair of surface lines with first and second floating lines to transmit an output voltage of each cell of a battery pack connected with the surface lines to a differential amplifier through a flying capacitor connected with the floating lines. Because of the division of the photo MOS switches on the surfaces of the circuit substrate, temperatures of the photo MOS switches have less dispersion, and an S/N ratio of each signal indicating the output voltage can be improved.