Open Pin Detection Circuit for Switching Regulator Feedback
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Solution Overview
Problem
Integrated circuits, particularly switching regulators, face the challenge of detecting an open pin condition, which can lead to damaging voltage or current being applied to the load due to a disconnection in the feedback connection, potentially causing damage.
Innovation Solution
An integrated circuit open pin detector is implemented, comprising a current source, a comparator, and a controller. The detector compares the voltage at the pin to threshold voltages, initiates open pin detection by sourcing current, and indicates an open pin condition if the voltage exceeds a second threshold within a predetermined time, while preventing the voltage from exceeding a predetermined level using a current sink and pull-down resistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a relatively small current is introduced into the feedback input to detect open pin condition, then the open pin condition can be detected, but the feedback voltage increases causing the control loop to drive output voltage low and possibly trip overvoltage protection
Solution Approach 1:
The patent applies preliminary action by introducing a small detection current into the feedback input before the open pin condition occurs. This proactive current injection allows the system to detect potential open pin conditions by monitoring feedback voltage changes, enabling preventive action before actual damage can occur to the load or circuit.
Solution Approach 2:
The patent uses an intermediary approach by introducing a small detection current as a mediator between the feedback input and the control loop. This intermediary current allows the system to sense open pin conditions without directly disrupting the main feedback signal, thereby detecting faults while minimizing impact on normal operation.
2Reliability
If the feedback connection is disconnected (open pin condition), then the integrated circuit may increase output to the load, but this provides damaging voltage or current to the load
Solution Approach 1:
The system performs preliminary detection by continuously monitoring the feedback input for signs of disconnection before the open pin condition can cause damaging output voltage. The small detection current establishes a baseline feedback voltage that, when changed, indicates an open pin condition, allowing preventive shutdown before load damage occurs.
Solution Approach 2:
The patent employs feedback by using the feedback input signal itself as the detection mechanism. When the feedback connection is disconnected, the change in feedback voltage (caused by the detection current) provides immediate feedback to the control loop, triggering a response that prevents the harmful high output voltage condition from developing.
3Object-affected harmful factors
If the switch is turned off in response to open pin signal, then damaging voltage to load is prevented, but the regulated output voltage may drop
Solution Approach 1:
The patent converts the harmful effect of turning off the switch (which causes output voltage drop) into a beneficial protective action. By detecting the open pin condition through the feedback voltage change caused by the detection current, the system can intentionally shut down the switch to prevent much more severe damage to the load, transforming a minor operational disruption into a major protective measure.
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
Effectively detects and responds to open pin conditions, preventing voltage escalation and ensuring safe operation by turning off the switch and maintaining the regulated output voltage within safe limits, allowing for automatic recovery from open pin faults.
Implementation Method 1
introduce a relatively small current into the feedback input of the regulator
Implementation Method 2
comparator having a first input coupled to the pin, a second input responsive to a threshold voltage
Data Source
AI summary
An integrated circuit an open pin detector includes a current source coupled to the pin, a comparator having a first input coupled to the pin, a second input responsive to a threshold voltage, and an output at which a comparator output signal is provided. A controller is responsive to the comparator output signal to provide an enable signal to the current source and an open pin signal indicative of an open pin condition at the pin. A method for detecting an open pin condition of a pin of an integrated circuit includes comparing the pin voltage to a first threshold voltage level, initiating open pin detection in response to the pin voltage falling below the first threshold voltage level, such as by providing a current to the pin, and indicating an open pin condition if the pin voltage rises to exceed a second threshold voltage level within a predetermined time interval. Also described is preventing the pin voltage from exceeding a predetermined voltage level during open pin detection.