Battery Voltage Equalizer Diagnostic Circuit Design
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Solution Overview
Problem
Conventional voltage equalizers for battery packs require numerous steps for failure diagnosis and may falsely detect nonconformity in the equalization switch operation, leading to undetected failures in the driving system.
Innovation Solution
A voltage equalizer with discharge resistors, equalization switches, an equalization controlling unit, and an equalization diagnostic unit, which generates and compares control signals and detection signals to determine the operational status of each battery block, reducing the number of steps needed for diagnosis and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage detection is performed in two states (switch on and off) to diagnose equalization switch conformity, then diagnostic accuracy is improved, but the number of diagnosis steps increases
Solution Approach 1:
The patent applies preliminary action by pre-configuring the equalization control unit to generate control signals that automatically sequence the voltage detection process. The system pre-establishes the diagnostic protocol where voltages are detected in different states (equalization on/off) without requiring manual intervention for each step, thus maintaining diagnostic accuracy while reducing the perceived number of steps through automation.
2Reliability
If multiple voltage detection steps are used to diagnose equalization circuit failures, then diagnostic reliability is improved, but system complexity increases
Solution Approach 1:
The patent merges the control function and diagnostic function into a single integrated equalization control unit. This unit both controls the equalization switches and performs voltage detection and diagnosis. By combining these functions, the system maintains reliable multi-state voltage detection while reducing overall system complexity through functional integration rather than separate dedicated circuits.
Solution Approach 2:
The equalization control unit serves multiple functions: it controls the equalization switches during normal operation, detects voltages in different states, diagnoses switch conformity, and identifies circuit failures. This multi-functionality reduces the need for separate dedicated diagnostic hardware, thereby maintaining diagnostic reliability while reducing system complexity.
3Reliability
If conventional voltage equalization diagnosis is performed, then equalization function is achieved, but false positives occur in nonconformity detection
Solution Approach 1:
The patent implements feedback by having the equalization control unit continuously monitor voltages across battery blocks during equalization operation and use this information to diagnose switch conformity. The system compares detected voltages against expected values and adjusts its diagnosis accordingly, reducing false positives by verifying actual circuit behavior rather than relying on simple presence/absence detection.
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
Enables swift and accurate detection of nonconformity in the equalization circuit, ensuring that the output voltages of battery blocks are maintained within a desired range, thereby preventing false positives and improving system reliability.
Implementation Method 1
discharge current flows in the discharge resistor 53 and electric power of the unit cell 51 is consumed, thus reducing a voltage of the unit cell 51
Data Source
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AI summary
A voltage equalizer for a battery pack includes equalization switches (SW1 to SW3) provided corresponding to respective battery blocks (BT1 to BT3, BT11 to BT13) that construct the battery pack (23, 23a), an equalization controlling unit (15), and an equalization diagnostic unit (14). The equalization diagnostic unit obtains an equalization control signal outputted from the equalization controlling unit, and an equalization detection signal detected at connection points (P1 to P3) of the equalization switches. Then, the equalization diagnostic unit compares the equalization control signal and the equalization detection signal, and diagnoses whether or not equalization processing in each of the battery blocks is executed in conformity based on a result of the comparison. For example, the equalization diagnostic unit determines that the equalization processing is conformity when the equalization control signal and the equalization detection signal coincide with each other, and that the equalization processing is nonconformity when both of the signals do not coincide with each other.