Vehicle Power Supply Control Device with External Commutation Diodes
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Solution Overview
Problem
Existing power supply control devices for on-vehicle electrical loads face challenges in protecting against shorting faults and ground faults on the positive pole side, leading to potential over-stress on switching elements and excessive surge voltages within the control device due to inadequate current limiting and grounding configurations.
Innovation Solution
A power supply control device with a microprocessor-based system that includes individual abnormality detection, negative line breakage detection, and abnormality processing circuits, utilizing commutation diodes connected in parallel with electrical loads and external to the internal ground circuit, preventing load currents from flowing into the internal ground and stabilizing the electrical potential within the control unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the current detection resistor is connected to the negative terminal of the electrical load, then the current can be detected, but connectors are required for both positive and negative pole side wirings, increasing device complexity
Solution Approach 1:
The patent extracts the current detection function from the negative terminal wiring path and relocates it to the positive terminal side. The current detection resistor is connected between the positive terminal of the electrical load and the switching element, allowing current detection without requiring a separate negative pole connector. This reduces the number of connectors while maintaining accurate current measurement capability.
2Speed
If the switching element has very small current limiting resistance, then the switching element can be turned off quickly, but over-current flows through the switching element during shorting or ground faults, causing temporary over-stress
Solution Approach 1:
The patent implements preliminary protective action by placing the current detection resistor in series with the switching element on the positive terminal side. This resistor provides current limiting before any fault condition occurs, preventing over-current from damaging the switching element during shorting or ground faults, while still allowing fast turn-off when the resistor is properly sized.
3Duration of action of moving object
If the commutation diode anode is connected to the internal ground circuit, then the load current can be returned, but excessive surge voltage is applied to the current detector when wiring breakage or connector contact failure occurs, causing breakage
Solution Approach 1:
The patent introduces an intermediary protective structure by connecting the commutation diode anode to the positive terminal side through the current detection resistor, rather than directly to the internal ground circuit. This intermediary path limits surge voltage magnitude when wiring breakage or connector failure occurs, protecting the current detector and other sensitive components from excessive voltage while still providing a return path for load current during normal operation.
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 solution effectively protects against shorting and breakage abnormalities by preventing load currents from entering the internal ground circuit, stabilizing the electrical potential, and improving maintenance efficiency through abnormality history storage and notification.
Implementation Method 1
When a switching element is turned off, the commutation diode returns a load current which has been passed through the electrical load until that time, whereby the load current is smoothed and the generation of a surge voltage is suppressed.
Data Source
AI summary
A power supply control device for on-vehicle electric loads is proposed, the control device being capable of detecting breakages at a plurality of electrical loads, a positive side wiring thereof, a negative side wiring thereof, and a commutation circuit. Energization of electrical loads from driving power supply is controlled using switching elements. Anode terminals of commutation diodes connected in parallel with the electrical loads are connected to a load ground by an external common negative line or external individual negative lines. A breakage abnormality at the external common negative line or external individual negative lines is detected by negative line breakage abnormality detection circuit. Load currents at the electrical loads are detected by current detection resistors and current detecting differential amplifier circuits, and it is determined that there is an individual abnormality when a detected current is greatly different from a target current.