Bridge-Tied Transducer Driver With Charge-Pump Voltage Segmentation
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Solution Overview
Problem
Conventional switching driver circuits face challenges in generating high-amplitude drive signals for transducers while minimizing voltage stress on switches and electromagnetic interference (EMI), especially when using high driving voltages required by piezoelectric or ceramic transducers in portable devices.
Innovation Solution
A driver apparatus with a bridge-tied-load configuration utilizing first and second charge pumps to generate boosted voltages, allowing the output nodes to be switched between different voltage levels, including supply voltages and boosted voltages, with a controller managing the switching modes and duty cycles based on the input signal to achieve a desired output voltage range with reduced voltage differences across switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high driving voltages are used to generate high-amplitude drive signals for piezoelectric or ceramic transducers, then the output power and driving capability are improved, but the voltage stress across the switches increases requiring high voltage tolerance devices that add to cost and complexity
Solution Approach 1:
The output voltage range is segmented into multiple levels using charge pumps to generate intermediate voltage levels (e.g., +VP, -VP, +2VP, -2VP). The switch network selectively connects output nodes to these segmented voltage levels, allowing high output power to be achieved through multi-level switching rather than requiring single high-voltage switches.
Solution Approach 2:
Charge pumps are introduced as intermediary devices that generate boosted voltage levels from the input supply voltage. These intermediary voltage levels serve as intermediate steps between the input voltage and the desired high output voltage, reducing the voltage stress on individual switches while achieving high output power.
2Adaptability or versatility
If the output node is switched between high-side and low-side voltages defining the full output range, then the desired output voltage range is achieved, but the voltage variation at the output node increases impacting load current ripple and EMI generation
Solution Approach 1:
The full output voltage range is segmented into multiple discrete voltage levels. Instead of switching between only two extreme voltages (high-side and low-side), the output node switches among multiple intermediate levels generated by charge pumps. This segmentation reduces the voltage step size during switching, thereby minimizing voltage variation, load current ripple, and EMI while maintaining the ability to cover the full output voltage range.
3Device complexity
If conventional switching driver circuits are used with fixed high-side and low-side voltages, then the circuit complexity is kept low, but the ability to generate high-amplitude drive signals with reduced voltage stress is limited
Solution Approach 1:
The switching driver transitions from a static configuration with fixed high-side and low-side voltages to a dynamic configuration where voltage levels are dynamically generated by charge pumps. The controller dynamically selects which voltage level to switch to based on the input signal requirements, enabling adaptive drive signal amplitude while managing voltage stress through dynamic voltage level selection rather than fixed voltage rails.
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
The solution enables the generation of high-amplitude drive signals with reduced voltage stress on switches and minimized EMI, allowing for efficient operation across a wide output voltage range (+3VP to -3VP) while maintaining low circuit complexity and power efficiency.
Implementation Method 1
first and second charge pumps for generating, in use, first and second charge pump voltages that are different from the first and second supply voltages
Data Source
AI summary
This application relates to methods and apparatus for driving a transducer connected between two output nodes in a bridge-tied-load configuration. A driver receives first and second supply voltages and has charge pumps that generate respective first and second boosted voltages. The driver is operable in a first driver mode in which each output node is modulated between the first and second supply voltage; a second driver mode in which one output nodes is modulated between the first and second supply voltages and the other output node is modulated between either the first boosted voltage and the first supply voltage or between the second supply voltage and the second boosted voltage; and a third driver mode in which one of the output nodes is modulated between the first supply voltage and the first boosted voltage and the other output node is modulated between the second supply voltage and the second boosted voltage.