Sinusoidal Driver Using Analog Multipliers for Silicon Area Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing 8-bit sinusoidal DACs require high dynamic range and precision, often achieved with 12-bit or higher linear DACs, which are area-intensive and wasteful in bit combinations, making them inefficient for applications like bipolar stepper motors that need high step resolution at waveform peaks and relaxed resolution at zero current.
Innovation Solution
A method using an 8-bit linear DAC to generate a one-half sinusoidal waveform through interconnected analog current multipliers and a summing junction, achieving high resolution with lower-resolution DACs by approximating sin(x) = x - A*x^2 - A*B*x^3, and converting linear voltage to current, with optional current mirrors and transconductance amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a 12-bit or higher linear DAC is used to achieve high dynamic range and precision for sinusoidal waveforms, then the measurement precision and manufacturing precision are improved, but the area of stationary object increases significantly
Solution Approach 1:
The patent divides the sinusoidal waveform generation into multiple segments: a linear DAC generates a triangular waveform, which is then processed through separate analog computational blocks (multiplication by constants, squaring, cubing) to synthesize the sinusoidal waveform. This segmentation allows using a low-resolution DAC while achieving high effective precision through analog signal processing.
Solution Approach 2:
The patent introduces an intermediary analog computational system between the digital DAC and the final sinusoidal output. This intermediary consists of analog multipliers and summing junctions that transform the linear DAC output into a sinusoidal waveform, effectively bridging the gap between low-resolution digital input and high-precision sinusoidal output.
2Measurement precision
If a 12-bit or higher linear DAC is used to achieve high dynamic range, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
The patent segments the high-precision function into a simple linear DAC plus separate analog computational blocks. Each block performs a specific mathematical operation (multiplication, squaring, cubing), making the overall system easier to design and layout compared to implementing a single high-resolution DAC with all precision requirements concentrated in one component.
3Productivity
If an 8-bit sinusoidal DAC is used for bipolar stepper motor application, then the productivity is improved, but the measurement precision deteriorates at waveform peaks
Solution Approach 1:
The patent changes the parameter of the input waveform from sinusoidal to triangular (linear ramp), which can be easily generated by an 8-bit DAC. The sinusoidal shape is then synthesized through analog parameter transformations (multiplication by constants A and B, squaring, cubing operations) in subsequent stages, allowing the system to achieve high step resolution at waveform peaks while maintaining micro-stepping capability.
Data Source
AI summary
Input codes are sequenced at a lower-resolution linear DAC and the output is converted to a linear current waveform. A first of two interconnected analog current multipliers multiplies the linear current by itself and by the inverse of a first constant current source to create a quadratic current output. A second current multiplier multiplies the quadratic output current by the linear current and by the inverse of a second constant current source to generate a cubic current output. The quadratic and cubic currents are subtracted from the linear current to generate an approximation of the first 180 degrees of a sine wave current. Alternate (pi to 2*pi) positive-going one-half sine waves may be polarity reversed to create a complete positive-going and negative-going sine-shaped electrical current of higher resolution than is available from a sine DAC of resolution equivalent to that of the lower-resolution linear DAC.