Protection Voltage Circuit With Cross-Feedback for Monotonic Supply Behavior
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Solution Overview
Problem
Existing protection voltage generating circuits exhibit non-monotonic and potentially unstable behavior over a range of power supply voltages, particularly at lower voltage ranges where the differential between positive and negative power supply voltages is minimal.
Innovation Solution
A protection voltage generating circuit is designed with two voltage generating circuits that produce voltages with differing dependencies on the power supply voltage, coupled with amplifier circuits providing negative feedback to each other, ensuring the protection voltage is monotonic with respect to power supply voltage variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple passive minimum selector or maximum detector is used for protection voltage generation, then the circuit complexity is reduced, but the protection voltage exhibits non-monotonic and unstable behavior at lower voltage ranges
Solution Approach 1:
The patent introduces feedback mechanisms where the output of each amplifier is fed back to its own input and cross-coupled to the other amplifier. This feedback ensures that when one voltage source approaches equality with the other, the feedback action prevents both transistors from being simultaneously on, eliminating the non-monotonic behavior and ensuring stable protection voltage generation across the full power supply range.
2Device complexity
If transistors are cross-coupled to form an automatic multiplexer, then the protection voltage generation is simplified, but both transistors remain on together at equal voltages causing linear or unstable operation
Solution Approach 1:
The patent applies preliminary anti-action by introducing feedback that anticipates and prevents the problematic condition before it occurs. When the voltage difference between the two sources becomes small, the feedback mechanism activates to ensure one transistor turns off before both can be simultaneously on, thereby preventing the unstable linear operation region and ensuring clean multiplexing behavior throughout the voltage range.
Data Source
AI summary
A circuit and method for generating a protection voltage includes a pair of voltage-generating circuits that generate voltages from the power supply voltage. The voltages have a differing dependence on the power supply voltage so that a difference between the first voltage and the second voltage changes sign for a particular value of the power supply voltage. The voltages are supplied to a protection voltage generating circuit that includes a pair of amplifiers having inputs that receive a respective one of the voltages and each of the amplifiers provides negative feedback to the other. An output circuit generates the protection voltage according to a maximum or a minimum value among the amplifier outputs, so that the protection voltage is monotonic with respect to variation of the power supply voltage.