Semiconductor Device Current Limiting Circuit Compensation
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Solution Overview
Problem
Existing semiconductor devices face variations in current limiting due to manufacturing variations in detection resistor and protection transistor values, leading to inconsistent output current in high-side switch configurations, which can cause malfunction and parasitic diode conduction issues.
Innovation Solution
A semiconductor device with a limited current generation circuit that includes a compensation transistor and resistor to offset variations in threshold voltage and resistance values, ensuring consistent output current by converting the limit setting current based on these variations and supplying it to the protection transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a detection resistor and protection transistor are used to limit output current, then current limiting function is achieved, but variations in resistance value and threshold voltage cause variations in the limited current
Solution Approach 1:
The patent implements a feedback mechanism where the limited current generation circuit continuously monitors the output current through the protection transistor and detection resistor, and automatically adjusts the gate-source voltage of the protection transistor to maintain a stable limited current value despite manufacturing variations. This closed-loop control ensures that the limited current remains consistent across different devices.
Solution Approach 2:
The patent changes the operating parameters of the protection transistor by dynamically adjusting its gate-source voltage based on the detected current level. By varying the voltage parameter in response to current conditions, the circuit compensates for manufacturing variations in threshold voltage and resistance, maintaining a stable limited current output.
2Manufacturing precision
If manufacturing variations are reduced to achieve consistent current limiting, then current stability improves, but device complexity and manufacturing cost increase
Solution Approach 1:
The limited current generation circuit is designed to be self-regulating, using its own output current as the feedback signal. The circuit automatically adjusts its operation based on the actual current flow through the protection transistor, eliminating the need for external adjustment mechanisms or complex calibration procedures, thereby maintaining simplicity while achieving high precision.
3Measurement precision
If the detection current is increased to improve detection accuracy, then current monitoring precision improves, but power consumption increases
Solution Approach 1:
The patent uses a partial action approach where the detection transistor processes only a small fraction of the total output current. By designing the detection path to handle a minimal necessary current level rather than the full output current, the circuit achieves sufficient detection accuracy for current limiting control while keeping power consumption low.
Data Source
AI summary
A semiconductor device of the present invention includes an output transistor connected between a power supply terminal and an output terminal; a detection transistor generating a detection current that is proportional to a current flowing through the output transistor; a detection voltage generation unit generating a detection voltage based on a detection current; a protection transistor drawing a current from a control terminal of the output transistor to the output terminal according to the detection voltage; and a limited current generation circuit that generates a limited current that is obtained by converting a limit setting current that sets a current flowing through the output transistor in a protection state according to a variation of a threshold voltage of the protection transistor and a variation of the detection voltage with respect to the detection current, and supplies the limited current to a first terminal of the protection transistor.