Chopper Amplifier Demodulator Coupling for Ripple Suppression
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Solution Overview
Problem
Chopper amplifiers generate unwanted chopper ripple due to offset voltages being amplified and demodulated, leading to unwanted alternating voltage, which existing techniques often address inefficiently or at high cost.
Innovation Solution
A chopper amplifier circuit design with a modulator and demodulator circuit tuned to a chopper frequency, employing alternating direct and capacitive coupling of amplifier outputs to summing circuit inputs, and using discharge resistors and stacked capacitors to reduce chopper ripple.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional demodulator circuit coupling is used, then circuit simplicity is maintained, but chopper ripple is amplified and appears as unwanted alternating voltage
Solution Approach 1:
The demodulator circuit is segmented into multiple coupling paths: direct coupling paths and capacitive coupling paths. Each path processes the signal differently, with direct paths preserving low-frequency components and capacitive paths blocking DC offset while passing AC components. This segmentation allows the circuit to simultaneously achieve ripple reduction and maintain signal integrity without requiring a complete redesign of the demodulator architecture.
Solution Approach 2:
The invention merges direct coupling and capacitive coupling techniques within the same demodulator circuit. By combining both coupling methods in parallel, the circuit leverages the advantages of each: direct coupling provides low impedance paths for signal transmission while capacitive coupling blocks DC offset voltages that cause chopper ripple. The merged approach achieves superior ripple reduction compared to using either method alone.
2Power
If offset voltages are amplified by the amplifier circuit, then signal amplification is achieved, but unwanted alternating voltage (chopper ripple) is generated
Solution Approach 1:
Capacitors are introduced as intermediary elements between the amplifier output and the summing circuit inputs. These capacitors act as mediators that block DC offset voltages from being transmitted to the output while allowing the amplified AC signal components to pass through. The capacitors enable the amplifier to perform its signal amplification function without propagating the harmful DC offset that would otherwise be converted to chopper ripple by the demodulator.
3Adaptability or versatility
If chopper frequency modulation is used, then DC measuring voltage can be converted to AC, but offset voltages are amplified and create ripple
Solution Approach 1:
Different coupling paths are assigned different local qualities: direct coupling paths provide low impedance for signal transmission while capacitive coupling paths provide high impedance to DC offset voltages. By giving different parts of the circuit different coupling characteristics, the system achieves both effective signal transmission and offset voltage blocking, resolving the contradiction between voltage conversion capability and ripple generation.
Data Source
AI summary
The present disclosure relates to chopper amplifier circuits featuring inherent chopper ripple suppression. A chopper amplifier circuit includes a modulator circuit tuned to a chopper frequency, and configured, in accordance with the chopper frequency, to convert a voltage into an AC voltage; an amplifier circuit having inverting and non-inverting inputs for the AC voltage, and having inverting and non-inverting outputs for an amplified AC voltage; a demodulator circuit tuned to the chopper frequency, and configured to convert the amplified AC voltage into an amplified DC voltage, the inverting output being coupled, via a first capacitance in a first signal path, to a first input of the demodulator circuit, the non-inverting output being coupled, via a second capacitance in a second signal path, to a second input of the demodulator circuit; and a discharge resistor circuit coupled on an output side of both capacitances between the first and second signal paths.