Solenoid Current Control Using Low-Side Switch Duration Cutoff
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Solution Overview
Problem
Current current control devices for solenoids face challenges in controlling currents in reverse directions, particularly when a ground line disconnection occurs, leading to unintended reverse currents that can cause valve operations and shift shocks, especially in solenoids controlling lock-up clutches.
Innovation Solution
A current control device with a high-side switch element connecting the solenoid to a battery power source, a low-side switch element connecting it to the ground power source, and a switch control circuit that measures the ON duration of the low-side switch element, temporarily turning it off when a predetermined time is reached to prevent reverse currents, ensuring normal feedback control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the low-side switch element is kept ON to allow reverse current flow for solenoid control, then the solenoid can be controlled in reverse direction, but unintended reverse currents occur when ground line disconnection happens causing valve operations and shift shocks
Solution Approach 1:
The control device measures the ON duration of the low-side switch element and proactively turns it OFF when a predetermined time threshold is reached, before unintended reverse current can occur. This preliminary action prevents the harmful effect by anticipating the potential ground line disconnection issue and cutting off the reverse current path in advance.
Solution Approach 2:
The control device continuously monitors the ON duration of the low-side switch element and uses this feedback information to make real-time control decisions. When the measured duration exceeds the predetermined threshold, the feedback mechanism triggers the switch element to turn OFF, thereby preventing unintended reverse current flow while maintaining normal bidirectional control capability.
2Object-affected harmful factors
If the low-side switch element is temporarily turned off to prevent reverse current, then unintended valve operations are prevented, but the control complexity increases due to duration measurement and conditional switching
Solution Approach 1:
The control device uses its existing duration measurement circuit (originally designed for PWM control) to simultaneously detect potential reverse current conditions. The system serves multiple functions with the same hardware resources, avoiding additional complex circuits while achieving reverse current prevention through intelligent utilization of existing capabilities.
Solution Approach 2:
The control device changes the operating parameter of the low-side switch element from a static ON state to a dynamically controlled state based on measured duration. By monitoring the time parameter and comparing it against a predetermined threshold, the system achieves reverse current prevention through parameter-based control logic rather than adding complex hardware circuits.
3Reliability
If the ON duration of low-side switch element is continuously monitored to detect reverse current conditions, then reverse current can be prevented, but the measurement and control time increases
Solution Approach 1:
The control device proactively turns off the low-side switch element when the predetermined time threshold is reached, preventing the need for continuous monitoring beyond this point. This preliminary action reduces the measurement time requirement while maintaining high detection accuracy, as the system knows when to expect potential reverse current conditions based on the time threshold.
Solution Approach 2:
The control device performs duration measurement and comparison at periodic intervals corresponding to the PWM control cycle. By checking the ON duration at regular intervals and comparing against the predetermined threshold, the system achieves reliable reverse current detection without requiring continuous monitoring, thereby reducing the time loss while maintaining detection accuracy.
Data Source
AI summary
Provided is a current control device capable of continuing feedback control for a solenoid in normal feedback control while preventing occurrence of an unintended valve operation due to flow of a reverse current.