Bridged Output Stage Protection via Reference Voltage Comparison
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Solution Overview
Problem
Conventional power output devices with protection circuits for short circuit and overload suffer from reduced power efficiency and increased thermal dissipation due to the need for resistors to detect abnormal currents, which also consume power and reduce output power.
Innovation Solution
A power output device with a bridged output stage and a reference voltage generator, utilizing transistors and comparators to detect voltage differences across the output stage, allowing for precise shutdown during short circuits or overloads without the need for additional resistors, thus maintaining power efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a resistor is used to detect abnormal current for protection, then the protection function is achieved, but power efficiency is reduced and thermal dissipation increases
Solution Approach 1:
The patent extracts the detection function from the main current path by using a separate detection transistor connected in parallel with the output transistor. This allows current detection without forcing all current through a resistive element, thereby maintaining power efficiency while achieving protection functionality.
Solution Approach 2:
The detection transistor serves multiple functions: it detects abnormal current conditions, generates detection signals for protection, and operates as part of the overall power output circuitry. This multi-functionality eliminates the need for separate resistive detection elements that would consume power.
2Device complexity
If a resistor is integrated into the IC for detection, then the protection circuit is compact, but thermal dissipation issues arise in the IC package
Solution Approach 1:
The patent extracts the heat-generating resistive detection element from the IC structure and replaces it with a transistor-based detection mechanism. Transistors have much lower power consumption and heat generation compared to resistors, thus maintaining integration benefits while solving thermal dissipation problems.
3Measurement precision
If a resistor is used for current detection, then abnormal current can be detected, but output power is reduced due to power consumption
Solution Approach 1:
The patent uses a detection transistor that replicates the electrical characteristics of the output transistor in a separate detection path. This copying approach allows accurate current detection without the power loss inherent in resistive detection, as the detection transistor operates with minimal power consumption compared to resistive elements.
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 prevents damage from short circuits and overloads while maintaining power efficiency by using proportional transistor sizes and reference circuits to generate a reference voltage range, allowing for immediate shutdown of the output stage when abnormal conditions are detected, thereby reducing power consumption and thermal issues.
Implementation Method 1
The detecting unit receives voltage differences across two terminals of each of the transistor when it is turned on, and the voltage difference is compared with the reference voltage range produced by the reference voltage generator
Implementation Method 2
the size of the reference transistor is proportional to that of the transistor implemented in the bridged output stage, and this proportional relation is the same as that between the reference resistor and the setting value of the minimum allowable load value
Data Source
AI summary
A power output device includes a bridged output stage, a reference voltage generator and a detecting unit to compare the output voltages from the aforementioned two units. The bridged output stage may be implemented by a full-bridge or a half-bridge configuration. The reference voltage generator is symmetric to the bridged output stage to generate a reference voltage, which is served as a reference voltage range for the voltage difference of the two terminals of the turned-on transistors in the bridged output stage during operation. When the detecting unit detects the voltages across the two terminals of the turned-on transistors in the bridged output stage exceed the reference voltage range, all the transistors are turned off and no power is outputted to the load. Therefore, the circuit is capable of preventing damages caused by a large current due to overload or short circuit.