Two-Stage Overvoltage Protection Circuit for Micro-USB Power Lines
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Solution Overview
Problem
The widespread use of Micro-USB connectors in portable devices poses a challenge due to the potential for unstable voltage from commercial power supplies exceeding the breakdown voltage, leading to increased circuit size and power consumption in protection circuits.
Innovation Solution
A protection circuit with a first voltage dividing circuit, a comparator, and a protection switch is integrated into the input/output circuit to monitor and regulate the voltage, turning off the power switch when excessive voltage is detected, and a regulator stops operation when even higher voltages are detected, thereby protecting the internal circuit while reducing circuit size and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an element with high breakdown voltage is used to protect against voltage exceeding breakdown voltage, then reliability is improved, but device complexity and circuit size increase
Solution Approach 1:
The protection circuit is divided into two independent stages: first protection circuit (comparator + protection switch) for detecting and responding to overvoltage conditions, and second protection circuit (regulator + stop switch) for handling extreme overvoltage conditions. Each stage uses elements with appropriate breakdown voltages for its specific function, avoiding the need for a single high-breakdown-voltage element throughout the circuit.
Solution Approach 2:
The voltage dividing circuit acts as an intermediary that scales down the high voltage from the power feeding line to a level suitable for the comparator. This allows the comparator to detect overvoltage conditions using low-breakdown-voltage elements, while the protection switch provides the necessary high-voltage protection capability.
2Reliability
If high breakdown voltage elements are used, then reliability is improved, but power consumption increases
Solution Approach 1:
The protection function is segmented into two stages with different power consumption characteristics. The first protection circuit operates at lower power for normal overvoltage detection, while the second protection circuit activates only for extreme overvoltage conditions, reducing overall power consumption compared to continuously operating high-voltage protection elements.
Solution Approach 2:
The circuit changes its operational parameters based on the voltage level detected. For moderate overvoltage, the first protection circuit activates with lower power consumption. For extreme overvoltage, the second protection circuit takes over, optimizing power consumption for each operating condition rather than maintaining high power consumption continuously.
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
The solution effectively protects internal circuits from irregular voltages, reduces circuit size, and lowers power consumption by implementing a two-staged overvoltage protection mechanism, ensuring stable voltage supply within a certain range and simplifying internal circuit design.
Implementation Method 1
a first voltage dividing circuit that is connected between a power feeding line to feed power from an external power supply to an internal circuit, and a predetermined fixed potential to divide a voltage of the power feeding line
Implementation Method 2
a first comparator that compares a divided voltage, which has been divided by the first voltage dividing circuit, with a reference voltage
Implementation Method 3
The first protection switch is turned on when the voltage of the first node exceeds a first set voltage
Implementation Method 4
a regulator that receives the voltage fed from the power supply terminal to supply a constant voltage to the first protection circuit
Data Source
AI summary
A first voltage dividing circuit is connected between a power feeding line to feed power from an external power supply to an internal circuit, and a fixed potential to divide a voltage of the power feeding line. A first comparator compares a divided voltage, which has been divided by the first voltage dividing circuit, with a reference voltage, and outputs a signal to turn off a power switch inserted into the power feeding line when the divided voltage exceeds the reference voltage. A first transistor is connected between a first node where the divided voltage, which has been divided by the first voltage dividing circuit, is generated, and the fixed potential, and is turned on when the voltage of the first node exceeds a set voltage.