Current Driving Device High-Speed Calibration
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Solution Overview
Problem
Current driving devices face challenges in achieving uniformity of output currents, particularly when the reference current is small or changes, leading to non-uniformity in display images due to insufficient charging of voltage holding capacitance elements and variations in transistor characteristics across different positions in slim-layout elements.
Innovation Solution
A current driving device with three operation modes: voltage supply mode, current supply mode, and current output mode, where the device uses a first voltage supply part and a first current supply part to charge the voltage holding part efficiently, allowing for high-speed calibration and accurate reference current generation, even with small reference currents, and includes a second current supply part for proportional current and a current-voltage converting part to generate the target voltage, reducing power consumption and electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single current supply part is used for calibration, then device complexity is reduced, but calibration speed becomes insufficient when reference current is small
Solution Approach 1:
The calibration function is segmented into two independent parts: a voltage supply part that provides high-current voltage charging capability, and a current supply part that provides accurate reference current. This segmentation allows each part to specialize in its function, resolving the contradiction between simple structure and fast calibration speed.
Solution Approach 2:
A voltage holding capacitance element is introduced as an intermediary between the voltage supply part and the current supply part. The voltage supply part charges this capacitance element to a predetermined voltage, which then serves as the basis for the current supply part to generate the reference current. This intermediary enables the voltage supply part to provide high-speed charging without directly interfering with the precision current path.
2Use of energy by moving object
If reference current value is reduced, then power consumption is reduced, but calibration accuracy deteriorates due to insufficient charging capacity
Solution Approach 1:
The power consumption is reduced by using a small reference current from the current supply part, while calibration accuracy is maintained by using the voltage supply part to pre-charge the voltage holding capacitance element to a high voltage level. The segmentation allows the system to benefit from both low power consumption and high calibration accuracy simultaneously.
Solution Approach 2:
The system changes the voltage parameter of the holding capacitance element to a high predetermined voltage before calibration. This parameter change allows the small reference current to still achieve accurate calibration because the high voltage provides sufficient charging capacity even with low current.
3Device complexity
If multiple current output parts are calibrated sequentially, then device complexity is reduced, but time consumption increases
Solution Approach 1:
The voltage supply part performs a preliminary action by charging the voltage holding capacitance element to the predetermined voltage before the current supply part begins the calibration process. This preliminary voltage charging enables faster subsequent calibration operations, reducing the overall time consumption when multiple current output parts need to be calibrated.
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 high-speed calibration and reduced non-uniformity in display images by efficiently charging the voltage holding part, maintaining accurate reference currents, and minimizing power consumption and electromagnetic interference, thus improving the uniformity of output currents across multiple current output parts.
Implementation Method 1
a voltage holding capacitance element C1 connected to a ground terminal and a node N2
Implementation Method 2
the Nch transistors QN1-QNm generate, at the node N2, a gate voltage that is necessary for allowing the electric current from the reference current source I1 to flow through the transistors themselves
Data Source
AI summary
A current driving device comprises: a voltage supply part; a current supply part; and a plurality of current output parts, each comprising a current-voltage converting function, a voltage-current converting function, and a voltage holding capacitance element. The current output part takes three operation modes. Under a voltage supply mode, the current output part receives a voltage from the voltage supply part and holds the voltage in the voltage holding capacitance element. Under a current supply mode, the current output part receives the current from the current supply part, generates a second voltage by the current-voltage converting function and holds the voltage in the voltage holding capacitance element. Under a current output part, the current output part outputs an output current according to the voltage held in the voltage holding capacitance element by the voltage-current converting function. By charging the current output part with the reference voltage before the calibration performed by using the reference current, calibration of the current output part is performed at a high speed.