Current-Based Charge Source Circuit for High-Resolution OLED Touch ADC
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Solution Overview
Problem
Conventional charge source circuits for OLED touch technology face challenges with insufficient resolution, large circuit layout area, high cost, and complexity due to the use of voltage division techniques and operational amplifiers, which limit the adjustability and precision of charge output.
Innovation Solution
A charge source circuit that uses a reference current generation block, current mirror block, and charge output block to provide a precise amount of charge (Qdc) based on the formula Qdc=Idc*t, where Idc is the current and t is divided into time intervals with ratios equal to a power of 2, enabling continuous adjustability of the charge output with a small layout area and low voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage division technique and drive operational amplifier are used to provide precise voltage Vcom, then measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent extracts the voltage division technique and drive operational amplifier from the charge source circuit, replacing them with a current source that directly provides precisely controlled current. This removes the complex voltage reference generation hardware while maintaining measurement precision through current-based charge control.
Solution Approach 2:
The patent substitutes the voltage-based control mechanism (voltage division and operational amplifiers) with a current-based control mechanism. By using a current source with precisely controllable current magnitude, the system achieves the same measurement precision without requiring complex voltage reference circuitry.
2Adaptability or versatility
If multiple capacitors with different bit representations are used to achieve charge adjustability, then adaptability is improved, but area of stationary object increases
Solution Approach 1:
The patent changes the control parameter from voltage (Vcom) to current (Idc). By controlling the current magnitude through digital-to-analog conversion of the input digital signal, the system achieves charge adjustability without requiring multiple physical capacitors. The charge amount is determined by Qdc = Idc × t, where both Idc and t are digitally controllable.
Solution Approach 2:
The patent introduces a periodic time interval t during which the current Idc is applied to generate the charge Qdc. By controlling the duration and magnitude of this periodic current pulse, the system achieves precise charge control with a single current source, eliminating the need for multiple capacitors of different sizes.
3Measurement precision
If voltage division technique and operational amplifier are used, then measurement precision is improved, but ease of manufacture deteriorates
Solution Approach 1:
The patent removes the voltage division network and drive operational amplifier from the circuit, significantly simplifying the manufacturing process. The remaining circuit consists primarily of a current source and timing circuitry, which are easier to manufacture with standard integrated circuit processes while maintaining the required measurement precision through current-based charge 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 solution allows for precise and adjustable charge output within a wide range, reducing circuit complexity and cost, and enhancing the resolution of charge output, thereby improving reference subtraction and touch detection capabilities in OLED touch panels.
Implementation Method 1
a current mirror block coupled to the reference current generation block and configured to mirror the reference current
Implementation Method 2
a charge output block coupled to the current mirror block and configured to convert the mirrored current from the current mirror block into a corresponding amount of charge according to the following formula: Qdc=Idc*t
Data Source
AI summary
A charge source circuit, an analog-to-digital converter (ADC) and an organic light-emitting diode (OLED) touch panel are disclosed. The charge source circuit includes a reference current generation block, a current mirror block and a charge output block. The charge output block is configured to provide an amount of charge as current times time, rather than voltage times capacitance as conventionally done. This dispenses with the use of a voltage division technique, a drive operational amplifier or a great number of capacitors, resulting in circuit simplicity, reduced cost and circuit layout area savings. Moreover, current and time interval sequences can be designed to enable, with a very small area and voltage, continuous adjustability of the amount of charge within a desired range at a higher resolution. An equivalent capacitance corresponding to the amount of charge can be adjusted within a range from tens to hundreds of pF.