Relay Drive Circuit That Holds State During MCU Reset
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Solution Overview
Problem
The potential unexpected reset of a microcontroller in a battery management system of an electric vehicle can cause safety hazards due to abrupt switching of relays, leading to vehicle stoppage and relay wear.
Innovation Solution
A drive circuit with a delay module is introduced to maintain the state of a low-side driver module during microcontroller resets, using a delay signal to ensure the relay remains in its previous state, thereby preventing abrupt state changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a microcontroller is used to control relay switching in a battery management system, then the switching control function is achieved, but the system becomes vulnerable to unexpected resets causing safety hazards
Solution Approach 1:
The delay module is pre-configured with a delay time constant that is longer than the maximum expected microcontroller reset duration. When a reset occurs, the delay module automatically extends the control signal to ensure the relay maintains its state throughout the reset period, preventing abrupt switching before the microcontroller recovers.
Solution Approach 2:
The delay module acts as an intermediary between the microcontroller and the relay. It receives the control signal from the microcontroller and introduces a deliberate time delay, allowing the relay to maintain its state during microcontroller resets while still responding to legitimate control commands.
2Device complexity
If relay switching is controlled directly by microcontroller output, then control logic is simple, but relay wear increases due to frequent abrupt switching
Solution Approach 1:
The delay module is pre-configured with a delay time constant that is longer than the maximum expected microcontroller reset duration. When a reset occurs, the delay module automatically extends the control signal to ensure the relay maintains its state throughout the reset period, preventing abrupt switching before the microcontroller recovers.
Solution Approach 2:
The delay module acts as an intermediary between the microcontroller and the relay. It receives the control signal from the microcontroller and introduces a deliberate time delay, allowing the relay to maintain its state during microcontroller resets while still responding to legitimate control commands.
3Duration of action of moving object
If the microcontroller reset duration is extended for stable operation, then processing stability improves, but relay state maintenance becomes difficult
Solution Approach 1:
The delay module is pre-configured with a delay time constant that is longer than the maximum expected microcontroller reset duration. When a reset occurs, the delay module automatically extends the control signal to ensure the relay maintains its state throughout the reset period, preventing abrupt switching before the microcontroller recovers.
Solution Approach 2:
The delay module acts as an intermediary between the microcontroller and the relay. It receives the control signal from the microcontroller and introduces a deliberate time delay, allowing the relay to maintain its state during microcontroller resets while still responding to legitimate control commands.
Data Source
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AI summary
Embodiments of this application relate to the field of electricity, and disclose a drive circuit. In some embodiments of this application, the drive circuit includes a low-side driver module and a delay module, the delay module is configured to output a delay signal of preset duration to the low-side driver module in a case that a control module is being reset; and the low-side driver module is configured to: according to on the delay signal of preset duration, maintain a first state within the preset duration, the first state being the same as a second state; where the second state is a working state of the low-side driver module before the control module is reset, and the second state includes being on or off. The embodiments can help avoid safety hazards caused by unexpected disconnection of a drive signal of the control module.