Bypass Circuit for DCDC Converter Miniaturization
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Solution Overview
Problem
Existing power supply systems for vehicles are not adequately miniaturized due to the need for multiple DCDC converters and batteries with different chemistries, leading to increased complexity and size.
Innovation Solution
A power supply system incorporating a high voltage battery, a step-down DCDC converter, a low voltage lead battery, a low voltage lithium battery, a second DCDC converter, a bypass circuit, and a control device that manages the switch unit to bypass the second DCDC converter during constant voltage charging, reducing the number of FETs and capacity required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a second DCDC converter is provided between the low voltage lead battery and the low voltage lithium battery, then the low voltage lithium battery can be charged, but the number of FETs and capacity of the DCDC converter increases leading to larger system size
Solution Approach 1:
The bypass circuit includes a switch unit that dynamically changes the circuit configuration based on charging conditions. When constant current charging is required, the switch unit opens to enable current flow through the second DCDC converter. When constant voltage charging is performed, the switch unit closes to bypass the second DCDC converter, reducing the number of active FETs and minimizing system size.
Solution Approach 2:
The charging function is segmented into two paths: one through the second DCDC converter for constant current charging, and another through the bypass circuit for constant voltage charging. This segmentation allows the system to use only the necessary components for each charging mode, reducing overall system size while maintaining full charging capability.
2Adaptability or versatility
If multiple DCDC converters are provided for different battery configurations, then various charging modes can be supported, but the device complexity and number of circuits increases
Solution Approach 1:
The bypass circuit serves multiple functions: it provides an alternative charging path for constant voltage charging, acts as a dark current path, and reduces system complexity by allowing the second DCDC converter to be partially deactivated. This multi-functionality enables the system to support various charging modes without requiring separate dedicated circuits for each mode.
Solution Approach 2:
The switch unit dynamically reconfigures the circuit topology based on charging requirements, transforming a single complex circuit into two simpler operational modes. This dynamic reconfiguration maintains adaptability for different charging scenarios while reducing overall circuit complexity through selective component activation.
3Reliability
If the second DCDC converter is always active to ensure charging capability, then charging reliability is maintained, but the system cannot be miniaturized due to increased component capacity requirements
Solution Approach 1:
The switch unit periodically or conditionally activates the bypass circuit based on charging stage requirements. During constant current charging phase, the bypass is inactive and charging flows through the second DCDC converter. During constant voltage charging phase, the bypass is activated to provide an alternative path. This conditional activation reduces the required capacity of the second DCDC converter while maintaining charging reliability throughout different charging stages.
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 allows for miniaturization of the power supply system by using the second DCDC converter only when necessary, reducing the number of circuits and components, and enabling efficient charging methods based on the state of charge and voltage of the batteries.
Implementation Method 1
a bypass circuit connected to the low voltage power supply circuit to bypass the second DCDC converter
Implementation Method 2
a control device configured to watch the low voltage lithium battery and control on/off of a switch unit provided in the bypass circuit
Implementation Method 3
a dark current may flow in the bypass circuit
Data Source
Figure 1
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Figure 3
AI summary
A power supply system (1) includes a high voltage battery (3), a first DCDC converter (5) connected to the high voltage battery (3), a low voltage lead battery (7) configured to be charged from the high voltage battery (3) via the first DCDC converter (5), a low voltage lithium battery (9) connected to a low voltage power supply circuit (6), the low voltage lead battery (7), and a load (8,10), a second DCDC converter (12) connected to the low voltage power supply circuit (6) and disposed between the low voltage lead battery (7) and the low voltage lithium battery (9), a bypass circuit (13) connected to the low voltage power supply circuit (6) to bypass the second DCDC converter (2), and a control device (11) configured to watch the low voltage lithium battery (9) and control on/off of a switch unit (14) provided in the bypass circuit (13).