Feedback Level Shift Circuit for Supply Voltage Offset Control
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Solution Overview
Problem
Level shift circuits using differential amplification circuits experience large offsets in output signal DC levels when supply voltages of optical pickups and signal processing LSIs change, leading to malfunctions in signal processing.
Innovation Solution
A level shift circuit with a differential amplification circuit, a current generation circuit, a capacitor, a holding circuit, and a switching circuit, which forms a feedback loop to stabilize the output signal level independently of supply voltage variations, using feedback resistors and control signals to maintain a constant output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a differential amplification circuit is used for level shifting, then the signal level can be adjusted to match different supply voltages, but large offsets occur in the output signal DC level when supply voltages change
Solution Approach 1:
The patent applies feedback by connecting a feedback resistor between the output terminal and the inversion input terminal of the differential amplification circuit. This feedback mechanism automatically adjusts the output signal DC level to maintain stability even when supply voltages change, resolving the contradiction between adaptability and reliability.
Solution Approach 2:
The patent changes the operating parameters of the differential amplification circuit by introducing a current generation circuit that varies the bias current based on the detected output signal level. This dynamic parameter adjustment compensates for supply voltage variations and prevents large offsets in the output DC level.
2Adaptability or versatility
If the supply voltage of the optical pickup and signal processing LSI are different, then level shifting is necessary to interface between them, but the output signal DC level becomes unstable when supply voltages fluctuate
Solution Approach 1:
The feedback resistor continuously monitors the output signal DC level and adjusts the inversion input terminal voltage accordingly, maintaining stable output levels despite fluctuations in either the optical pickup or LSI supply voltages.
Solution Approach 2:
The patent introduces an intermediary control mechanism where the current generation circuit acts as a mediator between the supply voltage variations and the differential amplification circuit, adjusting the bias conditions to compensate for voltage changes and maintain stable output.
3Reliability
If a feedback mechanism is added to stabilize output signal level, then output stability improves, but device complexity increases
Solution Approach 1:
The patent implements a simple feedback loop using a single feedback resistor connected between output and inversion input terminals, providing output stabilization with minimal additional circuitry.
Solution Approach 2:
The differential amplification circuit with feedback operates as a self-regulating system that automatically compensates for supply voltage variations without requiring external control circuits or additional complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution prevents large offsets in output signal levels, ensuring stable signal processing independent of supply voltage fluctuations, and maintains consistent output levels even during temporary input signal errors.
Implementation Method 1
a capacitor connected to an output terminal of the current generation circuit so as to be charged with an electric current generated by the current generation circuit to induce a voltage in the capacitor
Data Source
AI summary
The invention provides a level shift circuit that prevents an offset when the supply voltage changes. A level shift circuit has a differential amplification circuit, a current generation circuit, a capacitor and a holding circuit. An input signal from the optical pickup is inputted to the non-inversion input terminal of the differential amplification circuit. First, by turning on a first switch, a feedback loop is formed by the differential amplification circuit, the current generation circuit and the capacitor to perform a level shift, and the voltage charged in the capacitor is held by the holding circuit. Then by turning off the first switch and turning on a second switch, the voltage held by the holding circuit is applied to the non-inversion input terminal of the differential amplification circuit to perform a level shift.