CAN Transceiver Regulation Circuit for High-Voltage Pulse Immunity
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Solution Overview
Problem
CAN transceivers are susceptible to abnormal high-voltage interference, leading to errors in output signals due to reverse recovery currents in diodes or field effect transistors, affecting the stability of differential signals in complex electromagnetic environments.
Innovation Solution
The CAN transceiver incorporates regulation circuits that sample terminal voltages to detect abnormal high-voltage pulses, generating regulation signals to adjust the forward currents through high-side and low-side switching transistors, ensuring stable differential signals by compensating for reverse recovery currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protection diode is used in the output stage circuit to protect against high-voltage interference, then the transceiver gains protection capability, but reverse recovery current is generated during switching from forward conduction to reverse cutoff, causing output state changes and affecting signal stability
Solution Approach 1:
The patent introduces a control circuit as an intermediary between the protection diode and the output stage. This control circuit detects the output state and dynamically adjusts the gate voltage of the switching transistor to compensate for reverse recovery current effects, thereby maintaining signal stability while preserving protection capability
Solution Approach 2:
The patent implements a feedback mechanism where the control circuit continuously monitors the output state of the transceiver and adjusts the switching transistor's gate voltage accordingly. When reverse recovery current causes the output to transition from dominant to recessive state, the feedback loop detects this change and applies corrective gate voltage to restore the intended output state
2Adaptability or versatility
If the CAN transceiver operates in a complex electromagnetic environment with high-voltage interference, then it must maintain communication functionality, but high-voltage pulses couple into the CAN bus causing reverse recovery currents that generate signal errors
Solution Approach 1:
The patent applies preliminary anti-action by using the control circuit to anticipate and counteract the effects of high-voltage interference before it causes signal errors. The control circuit proactively adjusts the switching transistor's operating state based on detected interference conditions, preventing reverse recovery current from disrupting communication
Solution Approach 2:
The patent converts the harmful reverse recovery current effect into a beneficial control signal. The control circuit detects the voltage changes caused by high-voltage interference and uses these changes to trigger compensatory actions, transforming the interference-induced signal transition into a controlled adjustment that maintains communication integrity
Data Source
AI summary
A CAN transceiver including a data transmission port, a high-side bus port, a low-side bus port, an output stage circuit, a first regulation circuit and a second regulation circuit. The first regulation circuit and the second regulation circuit eliminate errors of differential signals by receiving abnormal voltage signals and outputting regulation signals to increase a pull-up current or a pull-down current in the output circuit, the first regulation circuit regulates errors generated by abnormal positive high-voltage pulses coupled into the high-side bus port, and the second regulation circuit regulates errors generated by abnormal negative high-voltage pulses coupled into the low-side bus port; after the CAN transceiver applies the first regulation circuit and the second regulation circuit, influence of abnormal high-voltage pulse signals in a CAN bus on errors of output signals of the CAN transceiver is reduced, and EMC performance of the CAN transceiver is improved.