Load Driver Ground-Relay Layout for Reverse Battery Protection
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Solution Overview
Problem
Conventional load drivers face challenges in downsizing and high integration due to the need for high-voltage drivers to operate reverse connection protective relays, especially with the increasing voltage tolerance of auxiliary batteries in electric vehicles, which can exceed 12 volts to 24 or 48 volts, and the protection of polar capacitors against negative bias voltages.
Innovation Solution
The load driver incorporates a power converter, control circuit, and a reverse connection protective relay located on the ground line, allowing gate drive at low voltage without the need for a high-voltage driver, and utilizes a charge pump to boost battery voltage for driving the relay, simplifying the configuration and protecting polar capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high voltage driver is used to manage increasing battery voltages, then the battery voltage tolerance is improved, but the device complexity and size increase
Solution Approach 1:
A charge pump circuit is introduced as an intermediary device to generate the high voltage gate drive signal from the battery voltage itself. The charge pump acts as a mediator between the battery and the reverse connection protective relay, eliminating the need for external high voltage drivers while still providing the necessary gate drive voltage for proper relay operation at elevated battery voltages
2Reliability
If a dedicated high voltage driver is added to protect against reverse connection, then the protection reliability is improved, but the downsizing and integration are hindered
Solution Approach 1:
The charge pump circuit is integrated within the existing motor driver IC, merging the reverse connection protection function with the primary motor control functions. This consolidation eliminates the need for separate high voltage driver components and external protection circuits, achieving both reliable reverse connection protection and compact integration in a single device
Solution Approach 2:
The charge pump circuit serves multiple functions: it generates the high voltage gate drive signal for the reverse connection protective relay, provides over-voltage protection, and enables the relay to operate correctly at elevated battery voltages. This multi-functionality reduces the overall component count and device size while maintaining comprehensive protection capabilities
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
This configuration enables miniaturization and integration of the load driver while protecting capacitors from negative bias voltages, preventing avalanche breakdown, and maintaining efficient operation across varying battery voltages.
Implementation Method 1
a multiphase pre-driver circuit using a charge pump to boost the battery voltage and drive the reverse connection protective relay
Data Source
AI summary
A power converter is connected between a power supply line and a ground line, and the power supply line is connected to a battery. The power converter supplies converted power to a load by converting direct current power of the battery. A control circuit controls the power converter by a voltage applied from the battery. A reverse-connection protective relay is connected to the ground line, and interrupts a current flowing from the ground line to the power supply line via the power converter in a case where the battery is connected in a reverse direction. A voltage required for turning on the reverse-connection protective relay is applied to a gate of the reverse-connection protective relay in a case where the battery is connected in a forward direction, and is not applied to the gate of the reverse-connection protective relay in a case where the battery is connected in the reverse direction.