MEMS Gyroscope Drive Circuitry for Fast Turn-On and Low Power
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Solution Overview
Problem
Existing drive circuitries for MEMS gyroscopes face challenges in achieving short turn-on times, especially when using low voltage (LV) technology, which is essential for reducing power consumption and enabling pulsed mode operation.
Innovation Solution
The drive circuitry comprises a voltage supply unit, capacitance-to-voltage converter, threshold detector, digital phase shifter, integrator, variable gain amplifier, pulse signal generator, and controller, which work together to apply specific signals to the drive actuation units in three phases to achieve a very short turn-on time, allowing for efficient power management even at low voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional drive circuitry is used with low voltage technology, then power consumption is reduced, but turn-on time becomes excessively long
Solution Approach 1:
The drive circuitry is segmented into multiple functional blocks: voltage supply unit, capacitance-to-voltage converter, threshold detector, digital phase shifter, integrator, variable gain amplifier, pulse signal generator, and controller. This segmentation allows each block to be optimized independently, enabling low power consumption while achieving fast turn-on time through coordinated operation of the segmented components.
Solution Approach 2:
The controller pre-charges capacitors and prepares the drive actuation units before the actual drive signal is applied. This preliminary action reduces the time required for the gyroscope mass to reach steady-state oscillation, thereby reducing turn-on time without requiring excessive power during operation.
2Loss of time
If high voltage is used to reduce turn-on time, then turn-on time decreases, but power consumption increases
Solution Approach 1:
The drive circuitry employs periodic pulsed operation where the drive actuation unit is activated in synchronized pulses with the oscillation cycle. The pulse signal generator produces periodic drive signals that efficiently build up oscillation amplitude quickly, reducing turn-on time while maintaining low average power consumption through duty cycle control.
Solution Approach 2:
The variable gain amplifier dynamically adjusts the gain parameter of the drive signal during the startup phase to achieve rapid amplitude buildup, then reduces gain during steady-state operation. This parameter change allows fast turn-on without sustained high power consumption, resolving the contradiction between turn-on time and power usage.
3Loss of energy
If pulsed mode operation is implemented, then power consumption is reduced, but turn-on time control becomes difficult
Solution Approach 1:
The controller implements feedback control by monitoring the drive measurement signal and adjusting the drive actuation signal accordingly. The phase-locked loop detects the oscillation phase and frequency, and the controller uses this feedback to precisely control the turn-on timing and duration of pulsed operation, making turn-on time control easy while maintaining low power consumption.
Solution Approach 2:
The patent replaces traditional mechanical or analog timing circuits with digital signal processing and electronic control. The digital phase shifter and pulse signal generator use digital logic to precisely control timing, making turn-on time easily programmable and controllable without complex mechanical adjustments, thereby improving ease of operation for pulsed mode control.
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 enables a turn-on time of 50 ms or less, effectively reducing power consumption and enabling efficient operation in low voltage technologies like 0.18 um LV CMOS, while maintaining accurate angular rate measurement.
Implementation Method 1
A force acting on the gyroscope mass may be induced as a capacitive force by applying a voltage to the capacitor plates of the drive actuation unit
Implementation Method 2
The capacitance between the capacitor plates of the drive measurement unit is measured as a drive measurement signal and forms an indication of the displacement of the gyroscope mass
Implementation Method 3
A Coriolis force will apply to the gyroscope mass in the presence of an angular rotation. The Coriolis force is proportional to the velocity of the gyroscope mass, its angular rate of rotation and its mass, and perpendicular to the direction of movement
Data Source
AI summary
A drive circuitry for a vibration gyroscope is described. The drive circuitry comprises a digital phase shifter, a variable gain amplifier and a pulse signal generator arranged to generate a digital pulse signal having a frequency substantially equal to a drive frequency of the vibration gyroscope. A controller is arranged to connect drive actuation units of the vibration gyroscope to outputs of the pulse signal generator during a first start-up time period, to outputs of the digital phase shifter during a second start-up time period, and to outputs of the variable gain amplifier during a measurement time period. Furthermore, a vibration gyroscope device and a method of driving a vibration gyroscope are described.