Power Supply System Backflow Prevention Circuit
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Solution Overview
Problem
In in-vehicle systems with main and sub-batteries, switching from the main battery to the sub-battery due to power interruptions causes a temporary delay in power supply, leading to potential function stops in critical loads, especially in advanced driving assistance and automation systems, and incorporating large capacity capacitors or batteries is undesirable due to size, weight, and cost concerns.
Innovation Solution
A power supply system with a main power source, sub-power source, and switches, along with a backflow prevention circuit using diodes and a power source control unit that allows immediate current passage from the sub-power source to the load during main power source interruptions, eliminating the need for an additional current path and reducing component count by utilizing body diodes in semiconductor switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a switch is controlled to switch from the main battery to the sub-battery when power interruption is detected, then power supply continuity to the load is improved, but a temporal operation delay occurs causing power supply interruption
Solution Approach 1:
The backflow prevention circuit is pre-configured with diodes that automatically enable current flow from the sub-battery to the load before the control unit detects power interruption and actuates the switch. This preliminary arrangement of current paths eliminates the temporal delay by having the backup power path ready in advance, so when the main battery fails, power continuity is maintained immediately without waiting for detection and control actions.
2Reliability
If an additional current path is provided from the sub-power source to the load, then power supply continuity is improved, but the device complexity increases
Solution Approach 1:
The backflow prevention circuit merges the sub-battery current path with the existing main battery circuit by using diodes that allow current from either source to flow to the load through the same circuit path. This combining approach provides redundant power supply continuity while avoiding the need for completely separate parallel circuits, thereby reducing overall device complexity compared to fully independent backup circuits.
Solution Approach 2:
The backflow prevention circuit with diodes serves multiple functions: it prevents current backflow from sub-battery to main battery during normal operation, enables automatic current routing from sub-battery when main battery fails, and maintains power supply continuity without requiring active control. This multi-functionality achieves reliability improvement while keeping the circuit configuration relatively simple.
3Device complexity
If body diodes of semiconductor switches are utilized as backflow prevention diodes, then the number of components is reduced, but the switch control complexity increases
Solution Approach 1:
The body diodes of the semiconductor switches are designed to serve dual functions: their primary function as part of the switch device and their secondary function as backflow prevention diodes in the power supply circuit. By making the body diodes perform both switching-related and backflow prevention functions, the need for separate backflow prevention components is eliminated, reducing overall component count while the control remains integrated within the existing switch control logic.
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 ensures continuous power supply to critical loads without temporary interruptions, enhancing the reliability of driving assistance and automation systems while minimizing the need for large capacity components and reducing system costs.
Implementation Method 1
a backflow prevention circuit configured to prevent current backflow between the main power source and the sub-power source, and the backflow prevention circuit allows current passage in a direction from the sub-power source to the load
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
A power supply system includes: a first switch (14) connected between a main power source (11) and loads (22, 23); a second switch (15) connected between a sub-battery (13) and the loads; and backflow prevention circuit (14a, 15a) that prevent current backflow between the main power source and the sub-battery, and polarity of the backflow prevention circuit (15a) is devised so as to allow current passage in a direction from the sub-power source to the loads even when the second switch is in an off state. When power from the main power source (11) is interrupted, the power source power of the sub-power source (13) is supplied to the loads via the backflow prevention circuit (15a) even the second switch (15) remains in the off state, so that the power supply is not interrupted.