Constant Voltage Source Current Limitation Oscillation
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Solution Overview
Problem
Existing constant voltage sources exhibit undesirable oscillation tendencies and are limited by the dependence of maximum output current on input or supply voltage, which restricts their ability to handle higher voltages and requires additional stabilization measures.
Innovation Solution
A constant voltage source design that eliminates the second feedback loop by using a current mirror with a high output resistance and independent control signal limitation, allowing for higher input voltages and reducing oscillation tendencies, achieved through a control current branch with a transistor diode and a series connection of transistor pairs, and a voltage divider with a center tap for precise voltage regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a second feedback loop with current shunt and transistor is used to limit output current, then output current can be limited, but oscillation tendency increases and stability deteriorates
Solution Approach 1:
The patent extracts and eliminates the second feedback loop (current shunt and limiting transistor) from the circuit. Instead of using feedback-based current limitation, the invention uses a direct control signal limitation approach where the control signal is clamped to a maximum value, removing the source of oscillation while maintaining current limitation functionality.
Solution Approach 2:
The patent introduces a control signal limitation mechanism that acts as an intermediary between the control circuit and the power transistor. By limiting the control signal voltage to a maximum value (U_GS,max), it directly prevents excessive output current without requiring feedback measurement, thus avoiding oscillation issues.
2Device complexity
If conventional transistor configuration is used, then circuit is simple, but maximum output current depends on input voltage due to channel length modulation
Solution Approach 1:
The patent changes the control parameter from direct current control to voltage-clamped gate control. By limiting the gate-source voltage to a maximum value independent of input voltage, the output current becomes independent of supply voltage variations, eliminating the channel length modulation effect's impact on current accuracy.
3Adaptability or versatility
If higher input voltages are applied to conventional constant voltage source, then voltage range is extended, but transistor breakdown occurs
Solution Approach 1:
The patent segments the voltage handling function between the control circuit and the power transistor. The control circuit operates at lower control voltages while the power transistor handles the full input voltage range. This segmentation allows the use of higher input voltages without exposing the sensitive control transistors to breakdown conditions.
Data Source
AI summary
A constant voltage source is disclosed having an output current control element, which adjusts an output voltage of the constant voltage source by varying its output current, a control circuit, which acquires a measure for an actual value of the output voltage and processes it to a control signal for the control of the output current control element, and a limiting circuit, which limits the output current to a predefined maximum value by action on the control signal, whereby the limitation is independent of an actual value of the output current. Wherein the limiting circuit has a first pair comprising a first transistor and a second transistor and a second pair comprising a third transistor and a fourth transistor, whereby the first and fourth transistor belong to a first conductivity type, the second and third transistor belong to a second conductivity type, operating current paths of the first pair lie in series between a reference current source and a supply potential, the operating current paths of the second pair are integrated in series into the control branch, control terminals of transistors of the same type are connected to one another, control terminals of transistors of the first conductivity type are connected to the reference current source, and control terminals of transistors of the second conductivity type to a first voltage source. Further, a method for generating a load-independent constant output voltage is disclosed.