MEMS Mirror Driver Switching Scheme for Lower Power Dissipation
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Solution Overview
Problem
High-frequency microelectromechanical system (MEMS) mirrors experience significant power dissipation when driven with high-voltage signals, particularly in low-power applications like wearable augmented reality glasses, due to inefficiencies in converting electrical energy into mechanical oscillation, with a substantial portion of power lost in charging and discharging capacitors.
Innovation Solution
The proposed solution involves an oscillator driver system that toggles the driving signal between a low voltage level and a high voltage level, with the stator voltage fixed at a lower value, reducing the voltage difference and thereby minimizing power dissipation while maintaining sufficient torque for MEMS mirror operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If high voltage levels are applied to drive high-frequency MEMS mirrors, then sufficient torque and oscillation amplitude are achieved, but power dissipation increases significantly
Solution Approach 1:
The patent changes the voltage level parameters from traditional single-polarity switching (0V to +Vhigh) to dual-polarity switching (-Vhigh to +Vhigh). This parameter change allows the voltage difference across the capacitor to be reduced while maintaining the same torque output, since torque depends on the voltage difference squared and the dual-polarity scheme optimizes the average voltage difference throughout the oscillation cycle.
Solution Approach 2:
The patent implements periodic switching of the driving signal between positive and negative voltage levels at the resonance frequency of the MEMS mirror. This periodic action ensures that the mirror oscillates at its natural frequency, maximizing mechanical output while minimizing the energy required to sustain the oscillation, thereby reducing power dissipation.
2Speed
If high voltage switching is used to drive MEMS mirrors at resonance frequency, then oscillation amplitude is maintained, but energy is lost in charging and discharging capacitors
Solution Approach 1:
The patent changes the voltage waveform from unipolar to bipolar, allowing the capacitor to charge and discharge more efficiently. By switching between -Vhigh and +Vhigh, the capacitor experiences smaller voltage transitions on average compared to switching from 0V to +Vhigh, reducing the energy lost during charging and discharging cycles while maintaining the same oscillation frequency.
Solution Approach 2:
The dual-polarity driving scheme maintains continuous useful action by ensuring that the voltage difference across the capacitor always contributes to driving the mirror in the correct direction during each half-cycle of oscillation. This eliminates idle or counterproductive voltage transitions, keeping the system operating at maximum efficiency throughout the entire oscillation period.
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
This approach significantly reduces power dissipation, optimizing energy conversion and extending battery life in low-power devices by adjusting the voltage levels to achieve the same torque and deflection angles with reduced energy loss.
Implementation Method 1
the oscillator structure is driven about the rotation axis according to a voltage difference between the rotor voltage and the stator voltage
Data Source
AI summary
An oscillator driver system includes an oscillator structure and a driver circuit. The oscillator structure includes a rotor terminal configured to receive a rotor voltage and a stator terminal configured to receive a stator voltage, and is driven about a rotation axis according to a voltage difference between the rotor and stator voltages. The driver circuit is configured to generate a driving signal and output the driving signal as the rotor voltage, wherein the driving signal toggles between low and high voltage levels at an actuation frequency to drive the oscillator structure about the rotation axis, and wherein the stator voltage is a fixed voltage. The low and high voltage levels are greater than the stator voltage such that the voltage difference toggles between a low voltage difference and a high voltage difference as the driving signal toggles between the low voltage level and the high voltage level, respectively.