DC/DC Converter Relay Isolation for External Charging Durability
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Solution Overview
Problem
Existing electric power storage systems for vehicles face durability issues with converters due to external charging, and they have a high component count, which increases system size and complexity.
Innovation Solution
An electric power storage system with a DC/DC converter that steps down voltage for an auxiliary machine battery, using relays to isolate the converter during external charging, ensuring the auxiliary machine battery is charged without flowing current through the converter, and sharing the DC/DC converter for both output to the auxiliary machine and battery, reducing component count and system size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the auxiliary machine battery is charged via the inverter and boosting circuit during external charging, then the auxiliary machine battery can be charged, but the durability of the inverter and boosting circuit is reduced
Solution Approach 1:
The patent divides the charging system into separate paths: the inverter/boosting circuit handles power conversion for the traveling motor, while a dedicated DC/DC converter handles charging of the auxiliary machine battery during external charging. This segmentation prevents the auxiliary battery charging current from flowing through the inverter and boosting circuit, thereby protecting their durability while maintaining functional independence of each circuit segment.
Solution Approach 2:
The patent introduces a dedicated DC/DC converter as an intermediary component specifically for charging the auxiliary machine battery during external charging. This intermediary device acts as a mediator that handles the auxiliary battery charging function separately, preventing direct current flow through the inverter and boosting circuit, thus resolving the durability issue while maintaining system functionality.
2Reliability
If a dedicated DC/DC converter for the auxiliary machine battery is disposed on the charger side, then the auxiliary machine battery can be charged without current flowing through the inverter, but the number of components increases and system size increases
Solution Approach 1:
The patent makes the DC/DC converter a universal component that performs multiple functions: it operates as a boosting circuit during normal vehicle operation to step up voltage from the auxiliary machine battery to the inverter, and serves as a dedicated auxiliary battery charger during external charging. This multi-functionality eliminates the need for separate dedicated charging components, reducing overall system complexity while maintaining converter durability.
Solution Approach 2:
The patent merges the DC/DC converter's normal boosting function with its external charging function into a single component. By combining these functions, the system avoids adding extra dedicated charging components, thereby reducing the total number of components and system size while still protecting the inverter and boosting circuit from excessive current during external charging.
3Ease of operation
If the main battery and inverter are connected for auxiliary machine battery charging, then the auxiliary machine battery can be charged, but electric power flows through the inverter causing durability reduction
Solution Approach 1:
The patent implements dynamic switching of circuit configurations using relays. During external charging, the system dynamically switches to a configuration where the DC/DC converter is connected to charge the auxiliary machine battery while the inverter is disconnected from this charging path. During normal operation, the system dynamically switches back to connect the inverter for its intended function. This dynamic reconfiguration enables easy operation for auxiliary battery charging while protecting converter durability through conditional disconnection.
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 suppresses the reduction in converter durability during external charging and reduces the number of components, maintaining system efficiency and compactness.
Implementation Method 1
a DC/DC converter stepping down an output voltage from the current path to an auxiliary machine and/or an auxiliary machine battery
Data Source
AI summary
An electric power storage system for a vehicle includes: an electric power storage device; a converter configured to perform voltage conversion between the device and the motor; a DC/DC converter configured to step down an output voltage to an auxiliary machine or an auxiliary machine battery; a charger configured to charge the device with external electric power; and first and second relays disposed on first and second connection lines connecting the device to the converter, respectively. One end of the DC/DC converter is connected to the first connection line between the first relay and the converter and the other end is connected to the second connection line between the device and the second relay. The charger is disposed on a current path capable of charging the device with the external electric power when the first relay is in an ON state and the second relay is in an OFF state.