Semiconductor Overcurrent Protection with Correction Current
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Solution Overview
Problem
Conventional semiconductor devices with overcurrent protective circuits face issues of low current detection accuracy and delayed response due to the variation in element temperatures, leading to inconsistent operation levels and potential damage to switching elements.
Innovation Solution
A semiconductor device with a switching element having a cell isolating structure, a sense resistor, a correction current generating circuit, and an overcurrent protective circuit that adjusts the operation level by supplying correction currents to the sense resistor, allowing independent adjustment of sense voltage without changing the reference voltage, thereby maintaining consistent operation despite temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a current sensing element with cell structure is used for overcurrent detection in IPMs, then the response speed is high, but the current detection accuracy becomes low leading to large variation of overcurrent levels
Solution Approach 1:
The patent introduces a correction current as an intermediary element to compensate for the inherent inaccuracies in the current sensing element. The correction current is injected into the sense resistor to offset errors caused by temperature variations and manufacturing tolerances, thereby improving detection accuracy without sacrificing the high response speed of the hardware-based sensing element
Solution Approach 2:
The patent dynamically adjusts the correction current parameter based on temperature conditions and operating states. By changing the correction current magnitude and direction (positive or negative) according to temperature compensation requirements, the system maintains accurate overcurrent detection across varying operating conditions while preserving the fast response characteristics
2Measurement precision
If the reference voltage is changed to adjust the operation level of overcurrent protective circuit, then the current detection accuracy improves, but the device complexity increases
Solution Approach 1:
Instead of changing the reference voltage, the patent modifies the sensing side by injecting a correction current through the sense resistor. This approach achieves the same effect of adjusting detection thresholds but through a simpler mechanism that doesn't require modifying the reference voltage generation circuitry, thus avoiding increased device complexity
Solution Approach 2:
The patent creates a compensated version of the sense voltage by adding the correction current to the raw sense voltage. This copied and corrected voltage signal accurately represents the true current level without requiring complex reference voltage adjustment circuits
3Reliability
If temperature compensation is implemented to maintain consistent operation level, then the reliability improves, but the device complexity increases
Solution Approach 1:
The correction current acts as a temperature compensation intermediary that is automatically adjusted based on temperature conditions. This intermediary element compensates for temperature-induced variations in the sensing element characteristics, maintaining reliable and consistent operation levels without requiring complex temperature sensing and adjustment circuits
Solution Approach 2:
The correction current mechanism is designed to automatically adapt to temperature changes and operational conditions without requiring external intervention or complex control systems. The circuit self-regulates the correction current to maintain accurate overcurrent protection across varying temperatures
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 adjusts the operation level of the overcurrent protective circuit without altering the reference voltage, reducing erroneous operations and noise-related malfunctions, while maintaining consistent performance across varying temperatures.
Implementation Method 1
a sense resistor one of whose ends is connected to the sense terminal and the other end is grounded; a correction current generating circuit that supplies a correction current in both directions of discharge and suction to an end of the sense resistor
Implementation Method 2
an overcurrent protective circuit that inputs a sense voltage generated when the sense current and the correction current flow via the sense resistor, and outputs a stop signal when the sense voltage is larger than a predetermined reference voltage
Data Source
AI summary
A semiconductor device includes a switching element outputting from a sense terminal a sense current at a fixed rate relative to a main current flowing in the switching element; a sense resistor connected at a first end to the sense terminal and to ground at a second end; a correction current generating circuit that supplies and extracts a correction current to at the first end of the sense resistor; an overcurrent protective circuit that receives a sense voltage generated when the sense current and the correction current flow through the sense resistor, and outputs a stop signal when the sense voltage is larger than a reference voltage; and a driving circuit that stops driving the switching element when the stop signal is received from the overcurrent protective circuit.