Charging Relay Welding Detection With Switched Parallel Resistance
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Solution Overview
Problem
The existing charging control devices for electric vehicles face challenges in accurately detecting the welding of relays on the battery charging path without generating excessive heat, which can lead to erroneous detection due to insulation resistance variations and high impedance in the voltage measurement circuit.
Innovation Solution
A charging control device with a series circuit of a resistor and a resistance regulation relay connected in parallel to the voltage measurement circuit, where the resistance regulation relay is controlled to be closed only during welding determination, and a photocoupler is used to detect the optical signal for fault determination, minimizing heat generation and preventing erroneous relay detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a voltage measurement circuit with high impedance is used to detect relay welding, then measurement precision is improved, but heat generation increases due to current flow through insulation resistance
Solution Approach 1:
The patent implements periodic welding determination at specific timing points (when relays are switching or after stable operation) rather than continuous monitoring. This allows the system to use high impedance measurement only when necessary, minimizing heat generation while maintaining detection accuracy when actually needed
Solution Approach 2:
The patent changes the impedance parameter of the voltage measurement circuit dynamically by controlling relays to switch between high impedance (during welding detection) and low impedance (during normal charging) states. This allows accurate welding detection when needed while minimizing heat generation during normal operation
2Temperature
If a resistor with low resistance value is added to reduce heat generation, then heat generation is suppressed, but device complexity increases
Solution Approach 1:
The patent uses existing components (relays, voltage measurement circuit, insulation resistance) to achieve heat suppression without adding external resistors. The system leverages its own operational states and existing insulation characteristics to solve the heat problem, avoiding increased device complexity
Solution Approach 2:
The patent makes the existing voltage measurement circuit serve multiple functions: both normal voltage measurement during charging and welding detection. By controlling relay states, the same circuit adapts to different measurement requirements without needing separate dedicated components
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 effectively suppresses heat generation during charging while accurately preventing erroneous detection of relay welding on the battery charging path, without the need for large resistors or increased substrate size.
Implementation Method 1
a photocoupler is used to detect the optical signal for fault determination
Data Source
AI summary
A charging control device including: a first and second electrode supply path; a voltage measurement circuit configured to measure a voltage between the first and second electrode side supply paths; a first and second electrode side relays on the first and second electrode side supply paths which are located closer to the battery than the voltage measurement circuit; a series circuit of a resistor and a resistance regulation relay, the series circuit being connected in parallel to the voltage measurement circuit; and a controller configured to control opening and closing the first electrode side relay, the second electrode side relay and the resistance regulation relay, wherein the controller is configured to control the resistance regulation relay to be closed when performing welding determination of the first electrode side relay and/or the second electrode side relay.