Non-Isolated DC-DC Converter Current Limiting for Battery Bus Protection
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Solution Overview
Problem
Existing power conversion devices lack effective overcurrent protection mechanisms, particularly for non-isolated DC-DC converters, which can lead to overcurrents during short circuits or load changes, potentially damaging batteries and other components.
Innovation Solution
Incorporation of a current limiting means, comprising a semiconductor switch and a freewheeling diode, to independently limit input and output currents, allowing rapid response to overcurrent conditions and preventing damage by controlling current values within safe limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If no current limiting means is provided in non-isolated DC-DC converters, then the device complexity is reduced, but overcurrent protection capability deteriorates
Solution Approach 1:
The patent combines the current limiting function with the existing DC-DC converter circuit by integrating a semiconductor switch and freewheeling diode into the converter's switching structure. This merging approach adds overcurrent protection capability while minimizing additional complexity, as the current limiting function is embedded within the existing power conversion topology rather than being a completely separate system.
Solution Approach 2:
The patent introduces a semiconductor switch as an intermediary element that acts as a controllable current limiter. This switch serves as a mediator between the power source and the load, rapidly responding to overcurrent conditions by adjusting its resistance state. The freewheeling diode acts as another intermediary that provides a safe current path during switching transitions, protecting other components from voltage spikes.
2Reliability
If a current limiting means is added to protect against overcurrent, then the protection capability is improved, but the response time may be delayed
Solution Approach 1:
The patent replaces mechanical protection mechanisms (such as fuses or circuit breakers) with a semiconductor-based current limiting system. The semiconductor switch can respond to overcurrent conditions in microseconds, dramatically faster than mechanical devices. This substitution of mechanical systems with electronic control enables rapid response time while maintaining robust protection capability.
Solution Approach 2:
The patent implements a feedback control mechanism where the controller continuously monitors the current through the DC-DC converter and rapidly adjusts the semiconductor switch's duty cycle in response to detected overcurrent conditions. This closed-loop feedback enables the system to detect and respond to overcurrent events almost instantaneously, maintaining both fast response time and effective protection.
3Reliability
If independent current limiting for both input and output currents is implemented, then the protection coverage is improved, but the device complexity increases
Solution Approach 1:
The patent designs the current limiting system with multi-functionality, where the same controller and semiconductor switch structure serve dual purposes: limiting both input current from the power source and output current to the load. The controller intelligently manages the semiconductor switch to provide appropriate current limiting on both sides of the DC-DC converter, achieving comprehensive protection coverage while avoiding the need for completely separate limiting circuits for each current path.
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
The current limiting mechanism effectively suppresses overcurrents, protecting the power conversion device and battery from damage, enabling rapid recovery from transient overcurrent events and maintaining stable operation.
Implementation Method 1
a current limiting means 22... to independently limit input and output currents... controlling current values within safe limits
Implementation Method 2
a current limiting means 22, comprising a semiconductor switch and a freewheeling diode
Data Source
AI summary
There is provided a power conversion device including: a non-isolated DC-DC converter provided between a battery and a DC bus to which one or more batteries are connected and a bus voltage is applied; and current limiting means which limits at least one of an input current to the non-isolated DC-DC converter or an output current from the non-isolated DC-DC converter, in which the non-isolated DC-DC converter performs an operation to convert a battery voltage of the battery to the bus voltage for outputting to the DC bus when the battery is discharged, and performs an operation to convert the bus voltage to the battery voltage for outputting to the battery when the battery is charged, and the current limiting means is connected between the non-isolated DC-DC converter and the battery, or between the non-isolated DC-DC converter and the DC bus.