Stylus Driving Circuit Stepped Waveform Power Reduction
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Solution Overview
Problem
High power consumption in styluses due to high-voltage square wave driving schemes, particularly at the tip electrode, resulting from rapid voltage changes and high driving frequencies, leading to increased instantaneous charging currents and wasted charge recovery.
Innovation Solution
A driving circuit with energy storage capacitors and a switch assembly that converts PWM square waves into stepped waveforms, allowing the driving electrode to output multiple voltages, reducing instantaneous charging currents and enabling charge recovery, thereby lowering power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high-voltage square wave driving scheme is used, then driving frequency can be high (50Khz-500Khz), but power consumption at the tip electrode becomes high
Solution Approach 1:
The patent divides the single high-voltage square wave into multiple stepped voltage levels (first voltage, second voltage, third voltage) during each driving cycle. The switch assembly controls different combinations of energy storage capacitors to generate these segmented voltage steps, transforming the abrupt square wave into a gradual stepped waveform that reduces instantaneous current spikes while maintaining the required driving frequency.
Solution Approach 2:
The patent changes the voltage parameter from a single high-voltage level to multiple progressive voltage levels. By controlling the switch assembly to connect different numbers of energy storage capacitors in series at different time periods within each driving cycle, the output voltage transitions through multiple stages (e.g., 0V → V1 → V2 → V3), effectively changing the voltage application pattern to reduce power consumption.
2Speed
If voltage changes quickly at the edge position of square wave, then driving frequency can be maintained, but instantaneous charging current increases
Solution Approach 1:
The patent applies beforehand cushioning by introducing intermediate voltage levels before the full high voltage is applied. The switch assembly progressively connects energy storage capacitors to bring the voltage up in steps, cushioning the abrupt voltage transition. This pre-cushioned approach prevents instantaneous current spikes while still achieving the required voltage change rate for maintaining driving frequency.
3Device complexity
If traditional square wave driving is used, then circuit structure is simple, but charge recovery is wasted
Solution Approach 1:
The patent implements charge recovery by using the switch assembly to redirect and recycle the charge from the tip capacitor during the driving cycle. Instead of dissipating the charge when the voltage transitions, the switch assembly recovers the energy stored in the tip capacitor and transfers it back to the energy storage capacitors or power supply, reducing energy loss while adding moderate circuit complexity.
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 significantly reduces power consumption by slowing down voltage changes and recovering charges, achieving a power consumption reduction of up to 75% compared to traditional square wave driving circuits.
Implementation Method 1
at least one energy storage capacitor, a switch assembly and a driving electrode, wherein the switch assembly is configured to control a voltage of the at least one energy storage capacitor to be connected to the power supply assembly, so that the at least one energy storage capacitor reaches an energy storage voltage
Data Source
AI summary
Disclosed are a driving circuit, a stylus and an electronic device. The driving circuit includes: a power supply assembly, at least one energy storage capacitor, a switch assembly and a driving electrode. In a driving cycle: the switch assembly is configured to control connections among the power supply assembly, the at least one energy storage capacitor and the driving electrode, so that the driving electrode outputs a first voltage, at least one second voltage and a third voltage, wherein the first voltage and the third voltage are respectively a maximum voltage and a minimum voltage output by the driving electrode, and the sum of energy storage voltages of the at least one energy storage capacitor is less than the first voltage. The driving circuit, the stylus and the electronic device of the embodiment of the present application could reduce a power consumption.