Parallel Relay Precharge Circuit for In-Vehicle Power Supply
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Solution Overview
Problem
Relays in in-vehicle power systems deteriorate rapidly due to repeated on-off cycles, leading to premature failure and the need for device replacement.
Innovation Solution
An in-vehicle power supply device with a configuration of multiple relays connected in parallel, controlled by a circuit that performs precharge operations and selectively switches relays to manage inrush currents, ensuring uniform wear and reducing current flow through individual relays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single relay is used to connect the battery and load device, then the device structure is simple, but the relay deteriorates rapidly due to repeated on-off cycles and inrush current
Solution Approach 1:
The single relay is segmented into multiple relays connected in parallel. Each relay handles a portion of the total current, reducing the current burden on each individual relay. This segmentation also allows the system to distribute switching operations across multiple relays, reducing wear on each component and extending overall system reliability.
Solution Approach 2:
Multiple relays are merged into a parallel configuration to work together as a single functional unit. The precharge circuit is combined with the relay system to collectively manage inrush current. This merging creates a more robust system where the failure of one relay does not cause complete system failure.
2Ease of operation
If the relay is repeatedly turned on and off to control power flow, then the power supply can be controlled, but the relay deteriorates due to repeated operation
Solution Approach 1:
The control function is segmented across multiple relays. Instead of one relay performing all switching operations, multiple relays share the control tasks. This distribution reduces the number of on-off cycles each individual relay must endure, extending their operational life while maintaining full power control capability.
Solution Approach 2:
The precharge circuit performs preliminary action by charging the capacitor before the main relays close. This preliminary charging reduces the inrush current that would otherwise cause severe stress and rapid deterioration during relay closing operations.
3Speed
If the relay closes directly without precharging, then the response speed is fast, but inrush current causes relay deterioration
Solution Approach 1:
The precharge circuit performs preliminary action by charging the capacitor before the main power relays close. This preliminary charging eliminates the inrush current problem that would otherwise cause relay deterioration, while the relays can still close quickly to establish full power connection.
Solution Approach 2:
The precharge circuit acts as an intermediary between the battery and the main power system. It provides a controlled path for initial charging that protects the relays from inrush current, while still enabling fast power connection when needed.
Data Source
AI summary
An in-vehicle power supply device is used in an in-vehicle power supply system The in-vehicle power supply system includes a battery a power path to which power based on the battery is supplied, and a capacitor electrically connected to the power path The in-vehicle power supply device includes a first circuit (e.g., a precharge circuit and a second circuit (e.g., a relay circuit The first circuit (e.g., the precharge circuit performs a precharge operation of precharging the capacitor. The second circuit (e.g., the relay circuit has a configuration in which a plurality of relays (e.g., first relays are connected in parallel, and is provided on the power path closer to the battery than is the capacitor