Inductive Load Switch Control for Reverse Current During GND Loss
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Solution Overview
Problem
In electronic control devices with multiple inductive loads connected in parallel, a reverse current can be generated when the ground line is disconnected, leading to shift shocks and reliability issues due to the need for additional circuits for reverse current detection.
Innovation Solution
The implementation of a control method that uses synchronous rectification control and reflux control for high-side and low-side switch elements, preventing reverse currents without requiring additional circuits for detection, by managing the ON/OFF states based on target current thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional circuits are added to detect reverse current, then reverse current detection capability is improved, but device complexity and component count increase
Solution Approach 1:
The control device uses its existing current detection circuit to simultaneously detect both load current and reverse current, making the existing circuit serve multiple functions. The microcontroller processes both normal operation current and reverse current detection using the same hardware resources, eliminating the need for separate detection circuits.
Solution Approach 2:
The existing current detection circuit is designed to universally detect both forward load current during normal operation and reverse current during ground disconnection events. The same circuit hardware performs multiple functions depending on the operational state, reducing overall system complexity.
2Reliability
If additional circuits are added to detect reverse current, then reverse current detection capability is improved, but device size increases
Solution Approach 1:
The control device uses its existing current detection circuit to simultaneously detect both load current and reverse current, making the existing circuit serve multiple functions. The microcontroller processes both normal operation current and reverse current detection using the same hardware resources, eliminating the need for separate detection circuits.
3Device complexity
If ground line is disconnected, then wiring simplicity is improved, but reverse current generation occurs causing shift shock
Solution Approach 1:
The control device proactively detects ground disconnection events and immediately responds by turning off switch elements to prevent reverse current flow before it can cause harmful effects. The system takes preliminary protective action rather than waiting for damage to occur.
Solution Approach 2:
The control device continuously monitors current flow direction and magnitude, providing real-time feedback about ground connection status. When reverse current is detected or ground disconnection is inferred from current patterns, the control system adjusts switch element states to eliminate the reverse current path.
Data Source
AI summary
A highly reliable electronic control device capable of preventing a reverse current at the time of GND disconnection in advance without requiring an additional circuit for reverse current detection is provided as an electronic control device in which a plurality of inductive loads are connected in parallel. There are provided a first high-side switch element that allows conduction between a battery power supply and a first external load; a first low-side switch element that allows conduction between a ground and the first external load; a second high-side switch element that allows conduction between the battery power supply and a second external load; and a second low-side switch element that is connected to the common ground with the first low-side switch element, and allows conduction between the ground and the second external load, synchronous rectification control for ON/OFF-controlling the first high-side switch element and the first low-side switch element is performed during a period in which a target current to the first external load is greater than a predetermined threshold value, and reflux control for ON/OFF-controlling the first high-side switch element while the first low-side switch element is turned off is performed during a period in which the target current to the first external load is equal to or less than the predetermined threshold value.