Parallel Hybrid Amplifier for Low-Distortion Capacitive Drive
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Solution Overview
Problem
Existing hybrid amplifiers for capacitive loads, such as piezoelectric print heads, face challenges in maintaining low distortion and power efficiency, especially when dealing with wide ranges of capacitive loads, often requiring high switching frequencies that increase power dissipation.
Innovation Solution
A parallel hybrid amplifier design that combines a linear amplification stage with a switching amplification stage, where the linear stage controls voltage and the switching stage manages current, allowing for reduced power dissipation and energy recovery without excessive switching frequency increases, using a measurement and control circuit for self-oscillating control and threshold/hysteresis control to limit current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a linear amplifier is used to drive a capacitive load, then the fidelity of reproduction is improved, but the power dissipation increases and energy recovery is not possible
Solution Approach 1:
The amplifier is divided into two separate stages: a linear amplification stage for voltage control and a switching amplification stage for current management. This segmentation allows each stage to operate in its optimal mode, with the linear stage ensuring fidelity and the switching stage minimizing power dissipation and enabling energy recovery.
2Loss of energy
If a switching amplifier is used to drive a capacitive load, then the power dissipation is reduced, but the fidelity of reproduction deteriorates when high bandwidth and high slew rate are required
Solution Approach 1:
The amplifier is divided into two separate stages: a linear amplification stage for voltage control and a switching amplification stage for current management. This segmentation allows each stage to operate in its optimal mode, with the linear stage ensuring fidelity and the switching stage minimizing power dissipation and enabling energy recovery.
3Adaptability or versatility
If the switching frequency is increased to maintain low current output from the linear amplifier stage across a wide range of capacitive load values, then the adaptability is improved, but the power dissipation increases and efficiency decreases
Solution Approach 1:
The amplifier is divided into two separate stages: a linear amplification stage for voltage control and a switching amplification stage for current management. This segmentation allows each stage to operate in its optimal mode, with the linear stage ensuring fidelity and the switching stage minimizing power dissipation and enabling energy recovery.
Solution Approach 2:
The invention changes the operating parameters of the two stages differently: the linear stage operates at low frequency with high voltage control, while the switching stage operates at optimized frequency with current management. This parameter differentiation allows adaptability across wide capacitive load ranges without requiring high switching frequencies that would increase power dissipation.
Data Source
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AI summary
An amplifier (1) comprises an input terminal (IIN) adapted to receive an input voltage signal (v_i) comprising a first phase (to, ti) with a trend monotonically increasing from a substantially null value to a maximum voltage value (Vmax), comprising a second phase (ti, t2) with a substantially constant trend equal to the maximum voltage value (Vmax), and comprising a third phase (t2, t3) with a trend monotonically decreasing from the maximum voltage value (Vmax) to a minimum value lower than the maximum value. The amplifier further comprises an output terminal (lo) adapted to drive a capacitive load (5), an amplification stage of the linear type (2) adapted to receive the input voltage signal (v_i), an amplification stage of a switching type (3) adapted to receive a driving voltage signal (S_drv_sw), and being configured to switch between a switched off mode and a switched on mode.