Capacitive Load Driver Circuit Energy Recovery
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Solution Overview
Problem
Existing driver circuits for capacitive stylus systems suffer from high power consumption due to energy losses when charging and discharging capacitive loads, particularly at high voltage frequencies, which affects the efficiency of signal transmission between the stylus and touch screens.
Innovation Solution
The implementation of an enhanced driver circuit with an energy transfer circuit that includes an energy storage element and switching elements to manage energy transfer at the edges of the drive signal, reducing energy loss by temporarily storing and retransferring energy, thereby enhancing efficiency and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional driver circuits charge and discharge capacitive loads at high voltage frequencies, then signal transmission speed is improved, but power consumption increases significantly
Solution Approach 1:
The patent recovers energy that would otherwise be dissipated during capacitor discharge by redirecting it through a second switch to charge the capacitor in the opposite polarity. This energy recovery mechanism reduces power consumption while maintaining high-frequency signal transmission capability
Solution Approach 2:
The patent introduces an intermediary energy storage element (inductor or second capacitor) that mediates the energy transfer between the capacitive load and the power supply. This intermediary enables efficient energy recovery and reduces direct power consumption during frequent charging cycles
2Productivity
If driver circuits operate at high voltage and high frequency, then data transmission efficiency is improved, but energy loss increases
Solution Approach 1:
The patent implements energy recovery by capturing the energy normally lost during capacitor discharge and redirecting it to charge the capacitor with opposite polarity, thereby reducing energy loss while maintaining high-frequency operation for efficient data transmission
Solution Approach 2:
The patent employs periodic switching of two complementary square wave signals to alternately charge and discharge the capacitive load in opposite polarities. This periodic action enables continuous energy recovery and reduces average energy loss while maintaining high data transmission efficiency
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 solution significantly reduces power consumption, from approximately 2.5 mW to 0.2 mW, improving battery life and efficiency while enabling precise stylus location determination with smaller electrodes and supporting a wider range of frequencies and higher voltages.
Implementation Method 1
an energy storage element; and an energy transfer circuit configured to transfer electric charge from the capacitive load to the energy storage element
Implementation Method 2
an energy transfer circuit configured to transfer electric charge from the capacitive load to the energy storage element at a first edge of the drive signal and to transfer electric charge from the energy storage element to the capacitive load
Data Source
AI summary
An apparatus and method for a voltage driver circuit where a path between a ground node and an output node includes an inductor and/or another storage element and an energy transfer circuit composed of at least two switching elements (e.g., transistors) and at least two valve elements (e.g. diodes). The energy transfer circuit operates to discharge a capacitive load (e.g. output capacitor) into the storage element and facilitate transition from low to high voltage while increasing efficiency. An additional path to ground may be included via another switching element to prevent crosstalk and hold the output at ground potential.