Power Supply Controller Current Limiting via Negative Sense Voltage
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Solution Overview
Problem
Existing semiconductor power supply controllers face challenges in accurately limiting output power due to propagation delays and complex circuitry, leading to inaccuracies in output voltage regulation and increased costs.
Innovation Solution
A power supply controller is designed with a current compensation circuit that uses a negative sense voltage to adjust the peak current through the power switch, eliminating the need for complex circuitry and improving accuracy by directly using voltage for sensing without requiring current-to-voltage translation, thereby reducing component count and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current limiting is based on time interval and rate of change, then output power can be limited, but complex circuitry is required that increases cost
Solution Approach 1:
The patent replaces complex time-based measurement circuitry with a simpler voltage-based sensing system. Instead of measuring current over time and calculating rate of change, the system uses a sense resistor to generate a voltage proportional to current, which is then directly compared to a reference voltage threshold. This substitution of mechanical/electrical measurement methods eliminates the need for complex timing and calculation circuits while maintaining accurate current limiting.
Solution Approach 2:
The patent changes the sensing parameter from time-based current measurement to voltage-based current sensing. By using a sense resistor to convert current into a proportional voltage signal, the system can directly compare voltage levels using simple comparator circuitry instead of complex time-interval measurement and rate-of-change calculation circuits, thereby reducing device complexity while maintaining reliability.
2Reliability
If time interval determination is used for current limiting, then power can be controlled, but inaccuracies in output voltage occur
Solution Approach 1:
The patent replaces imprecise time-based current measurement with direct voltage sensing across a sense resistor. The voltage signal is immediately proportional to the instantaneous current value, eliminating timing errors and rate-of-change calculation inaccuracies. This direct voltage comparison method provides more precise measurement of the actual current flowing through the power switch, resulting in better output voltage regulation.
Solution Approach 2:
The sense resistor automatically generates a voltage signal that is directly proportional to the current flowing through it, requiring no external calibration or complex processing. The voltage signal self-represents the current state, allowing direct comparison with the reference voltage to accurately determine when the current limit threshold is reached, thereby improving measurement precision without additional complexity.
3Difficulty of detecting and measuring
If current-to-voltage translation circuitry is used, then current sensing can be performed, but component count and power consumption increase
Solution Approach 1:
The patent extracts the current sensing function into a simple passive sense resistor that generates a voltage signal proportional to current. This eliminates the need for complex active current-to-voltage translation circuits, operational amplifiers, and associated components. The sense resistor performs the translation function passively through Ohm's law, significantly reducing component count while maintaining full current sensing capability.
Solution Approach 2:
The patent substitutes complex active current-to-voltage translation circuitry with a simple passive voltage sensing approach using a sense resistor. The resistor naturally converts current to voltage according to Ohm's law, eliminating the need for additional translation circuits, operational amplifiers, and associated components, thereby reducing both component count and power consumption while maintaining accurate current detection.
Data Source
AI summary
In one embodiment, a power supply controller is configured to receive a sense signal (CS) having a negative value that is proportional to the input voltage. The power supply controller uses the sense signal to limit the switch (27) current through the switch responsively to the value of the input voltage.