Single-Ended Current Driver Crossover Distortion Control
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Solution Overview
Problem
Existing single-sided current drivers for camera motors and haptic devices face distortion issues due to current crossover, which affects the accuracy and efficiency of position control in electronic devices.
Innovation Solution
A system with a single-ended driver, loop filter, and control circuitry that minimizes error between target and output currents, and resets the loop filter state variable when the load current changes polarity, reducing distortion and improving power efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-sided driver is used to reduce electromagnetic radiation and switching nodes, then device complexity and electromagnetic interference are reduced, but signal distortion occurs during current polarity crossover
Solution Approach 1:
The loop filter is reset before current polarity crossover occurs, preparing the driver to maintain accurate current control during the transition. This preliminary action prevents the accumulation of integration errors that would otherwise cause distortion during the polarity change
Solution Approach 2:
The system uses feedback from the current sense amplifier to monitor the actual output current and compares it with the target current. This feedback loop allows the system to detect and correct distortion during polarity transitions by adjusting the drive signal based on the integrated error signal
2Use of energy by moving object
If PWM drive mode is used to maximize power efficiency, then energy consumption is reduced, but noise increases compared to linear drive
Solution Approach 1:
The driver dynamically switches between PWM and linear drive modes based on operating conditions. The system can transition from high-efficiency PWM mode during normal operation to low-noise linear mode when precision is critical, optimizing both power efficiency and signal quality as needed
Solution Approach 2:
The system changes the operating parameters of the driver by switching between different drive modes. By adjusting the drive mode parameter, the system can optimize for either power efficiency (PWM) or low noise (linear) depending on the specific operational requirements
3Measurement precision
If linear current drive is used to improve accuracy with lower noise, then measurement precision is improved, but power efficiency decreases compared to PWM drive
Solution Approach 1:
The driver dynamically switches between PWM and linear drive modes based on operating conditions. The system can transition from high-efficiency PWM mode during normal operation to low-noise linear mode when precision is critical, optimizing both power efficiency and signal quality as needed
Solution Approach 2:
Instead of using linear drive continuously, the system applies it only partially - specifically during polarity transitions or when high precision is required. This partial use of linear drive minimizes its power consumption penalty while still achieving the necessary accuracy improvements
Data Source
AI summary
A system may include an output stage comprising a single-ended driver for driving a load at an output of the output stage, a loop filter coupled at its input to the output of the output stage and configured to minimize an error between a target current signal received by the loop filter and an output current driven on the load, and control circuitry configured to, when the load current is driven in a manner such that the load current changes polarity, reset a state variable of the loop filter.