Solid State Power Controller Semi-Analog Overcurrent Protection
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Solution Overview
Problem
Conventional solid state power controllers rely on microcontrollers for implementing I2t functions, leading to increased error frequencies and certification efforts, with capacitors affecting accuracy and long-term stability, and neglecting thermal behavior and non-overload energy balance.
Innovation Solution
A solid state power controller design that uses a power switch, current sensor, and control unit with a counter that increments or decrements based on current thresholds, implementing the I2t characteristic without a microcontroller, utilizing a comparator, differentiator, multiplier, and voltage-to-frequency converter to manage current flow and prevent overcurrents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a microcontroller is used to implement I2t functions, then the power controller can achieve flexible control and protection functions, but the error frequency increases and certification effort increases
Solution Approach 1:
The patent extracts the critical I2t protection function from the digital microcontroller domain and implements it using dedicated analog circuitry (capacitor C1 charged by overcurrent, counter circuit monitoring charge cycles). This separation removes the reliability concerns of software execution while preserving the essential protection functionality.
Solution Approach 2:
The patent replaces the mechanical/software-based microcontroller control with an analog electrical system where capacitor charging cycles physically represent the I2t integration process. The counter circuit mechanically counts these charge cycles to detect shutdown conditions, substituting digital computation with analog physical processes that are inherently more reliable.
2Adaptability or versatility
If a microcontroller is used to implement I2t functions, then the power controller can achieve flexible control and protection functions, but the certification effort increases
Solution Approach 1:
The patent extracts the critical I2t protection function from the digital microcontroller domain and implements it using dedicated analog circuitry (capacitor C1 charged by overcurrent, counter circuit monitoring charge cycles). This separation removes the reliability concerns of software execution while preserving the essential protection functionality.
Solution Approach 2:
The patent replaces the mechanical/software-based microcontroller control with an analog electrical system where capacitor charging cycles physically represent the I2t integration process. The counter circuit mechanically counts these charge cycles to detect shutdown conditions, substituting digital computation with analog physical processes that are inherently more reliable.
3Device complexity
If capacitors are used to implement I2t function, then the control can be simplified, but the accuracy and long-term stability are affected
Solution Approach 1:
The patent incorporates a discharge module with resistor R2 and capacitor C2 that continuously discharges the storage capacitor C1 at a controlled rate. This feedback mechanism compensates for charge accumulation over time and ensures that the capacitor voltage accurately reflects only the current overcurrent event, improving both accuracy and long-term stability.
Solution Approach 2:
The patent uses the counter circuit to monitor the number of charge cycles of capacitor C1, converting the continuous analog charging process into discrete digital count values. This parameter transformation allows precise detection of shutdown conditions while maintaining the simplicity of analog capacitor-based I2t integration.
4Device complexity
If thermal behavior is neglected in the control design, then the device complexity is reduced, but the protection accuracy deteriorates
Solution Approach 1:
The patent implements a continuous discharge mechanism using resistor R2 and capacitor C2 that constantly manages the charge state of capacitor C1. This continuous action ensures that the capacitor accurately reflects the current thermal state of the protected device, mapping thermal behavior without requiring complex thermal modeling or additional sensors.
Data Source
AI summary
The present disclosure relates to a solid state power controller, comprising: a power switch for interrupting a line; a current sensor for measuring a current flow on the line; and a control unit for controlling the power switch and that is configured to prevent a time-dependent overcurrent on the line on the basis of the current measured by the current sensor, wherein the control unit comprises a counter that is adapted to increment a count when the measured current is larger than a threshold value and to decrement the count when the measured current is smaller than the threshold value; and wherein the power switch is adapted to interrupt the line when the counter reaches or exceeds a predefined count.