Adaptive Power Limiter for Variable Input Voltage SMPS
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Solution Overview
Problem
Conventional switched mode power supplies (SMPS) face challenges in managing variable input voltages, leading to potential overloads or short circuits due to fixed current or voltage limits, which are not adaptable to changing conditions, resulting in component damage and inefficiencies.
Innovation Solution
An adaptive input power limiter is introduced, comprising an operational amplifier and comparator circuit within a microcontroller, which adjusts the current limit inversely proportional to input voltage changes, using resistor networks to generate an inverse-proportional waveform, allowing dynamic power management and preventing overloads by controlling the duty cycle and pulse-width modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If fixed current or voltage limits are used in SMPS, then the circuit protection is simple and reliable, but the system cannot adapt to variable input voltages, leading to potential overloads or short circuits
Solution Approach 1:
The patent implements dynamic current limiting where the maximum current limit is not fixed but varies with input voltage conditions. The system continuously monitors input voltage and adjusts the current limit accordingly, transitioning from static protection to adaptive protection that responds to changing operating conditions.
Solution Approach 2:
The system employs feedback mechanisms by monitoring the input voltage level and using this information to adjust the current limit setting. The power management circuit receives feedback about voltage conditions and automatically modifies protection parameters to match the current operating environment.
2Loss of energy
If conventional fixed power limits are implemented, then the control circuit is simple, but the system efficiency decreases under varying input conditions due to unnecessary limiting or insufficient protection
Solution Approach 1:
The system dynamically changes the current limit parameter based on input voltage conditions. Instead of using a single fixed threshold, the patent implements a variable threshold that is calculated and applied in real-time based on the relationship between input voltage and maximum power capacity.
Solution Approach 2:
The system performs preliminary calculations to determine appropriate current limits before power delivery occurs. By pre-calculating safe operating parameters based on expected voltage conditions, the system可以避免 unnecessary energy loss while maintaining protection.
3Adaptability or versatility
If the current limit is reduced as input voltage increases to maintain constant power, then overprotection is avoided, but the control mechanism becomes more complex
Solution Approach 1:
Instead of directly controlling current limit as a function of voltage, the system inverts the approach by using operational amplifiers and comparators to create a control signal that naturally responds to voltage changes. The circuit topology is arranged so that voltage changes automatically produce the appropriate current limit adjustments through the feedback network.
Data Source
AI summary
A power limiter for a switched mode power supply includes an operational amplifier and a comparator circuit. The operational amplifier is configured to receive an input voltage supplied to the SMPS as a first input and a reference voltage as a second input. The comparator circuit is configured to receive an output of the operational amplifier, receive a current sense signal, and generate an output signal configured to control a power generator. The output signal is based on a comparison between the output of the operational amplifier and the current sense signal.