Display Power Supply Dynamic Mode Switching for Efficiency
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Solution Overview
Problem
Power supplies for display devices, particularly those using DC-DC converters, often experience reduced current and power efficiency in continuous conduction mode, especially when the load of pixels is relatively low, leading to increased power loss and inefficiency.
Innovation Solution
The power supply selectively adjusts the off-duty cycle, channel capacitance, switching frequency, and slew rate of transistors based on the load condition, and shifts the clock signal's frequency to minimize power loss and interference, allowing for improved efficiency by switching to alternative modes such as discontinuous conduction or pulse skip modes when the load is low.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the DC-DC converter operates in continuous conduction mode (CCM) to stably provide driving current to pixels, then the stability of power supply is improved, but current and power efficiency deteriorate when pixel load is relatively low
Solution Approach 1:
The patent applies dynamics by enabling the DC-DC converter to dynamically switch between continuous conduction mode (CCM) and discontinuous conduction mode (DCM) based on real-time load conditions. When pixel load is high, CCM provides stable power; when load is low, DCM reduces switching operations and power loss. This dynamic mode adjustment resolves the contradiction between stability and energy efficiency.
Solution Approach 2:
The patent changes the conduction mode parameter of the DC-DC converter based on load conditions. By detecting pixel load levels and adjusting the operating mode (CCM or DCM), the system optimizes the balance between power supply stability and energy efficiency. This parameter change allows the converter to adapt to varying load requirements.
2Reliability
If the DC-DC converter switches internal transistors continuously in CCM to maintain stable power output, then the stability of current provision is improved, but the switching frequency increases leading to higher power loss
Solution Approach 1:
The patent implements periodic action by allowing the transistor switching to occur periodically rather than continuously when operating in DCM. During periods when the inductor current reaches zero, switching is paused, reducing the overall switching frequency and power consumption while still maintaining adequate current provision to pixels during active periods.
Solution Approach 2:
The system dynamically adjusts the switching behavior based on load conditions. In DCM, the converter transitions from continuous switching to periodic switching with idle periods, reducing power consumption while maintaining necessary current delivery to pixels during active switching periods.
3Speed
If the power supply operates at high switching frequency to respond to pixel power requirements, then the responsiveness to load changes is improved, but interference with the scan driver increases
Solution Approach 1:
The patent applies dynamics by making the switching frequency adaptive rather than fixed. The converter adjusts its operating frequency based on actual load conditions, using higher frequencies when needed for responsiveness and lower frequencies when possible to minimize interference with the scan driver, thus dynamically balancing responsiveness and interference reduction.
Solution Approach 2:
The system changes the switching frequency parameter according to load requirements and interference considerations. By adjusting this critical parameter, the power supply maintains responsiveness to pixel power needs while minimizing harmful electromagnetic interference with the scan driver's clock signal.
4Loss of energy
If the power supply increases off-duty and decreases channel capacitance to improve efficiency, then the power loss is reduced, but the ability to maintain stable voltage under varying load conditions deteriorates
Solution Approach 1:
The patent applies dynamics by making the off-duty ratio and channel capacitance adjustable parameters rather than fixed values. The system dynamically optimizes these parameters based on operating conditions, achieving low power loss during light loads while maintaining voltage stability during heavier loads or transient conditions.
Solution Approach 2:
The system changes operating parameters (off-duty ratio, channel capacitance) based on load conditions. During low-load operation, increased off-duty and decreased capacitance reduce power loss. During higher-load or transient conditions, parameters are adjusted to maintain voltage stability, resolving the contradiction between efficiency and stability.
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 approach enhances current and power efficiency, reduces power loss, and minimizes interference with the scan driver by optimizing the switching operations and transistor configurations according to the load conditions, thereby improving the overall performance of the power supply.
Implementation Method 1
transistors to convert an input power voltage into a first power voltage through a switching operation of the transistors
Data Source
AI summary
A display device includes: a display panel including scan lines, a first power line, a second power line, and pixels connected to the scan lines and the first and second power lines; a gate driver to sequentially provide scan signals to the scan lines based on a clock signal; and a power supply including transistors to convert an input power voltage into a first power voltage through a switching operation of the transistors and to supply the first power voltage to the first power line through a first output terminal. In response to an amount of current flowing through the pixels being less than a first reference current amount, the power supply is configured to change one or more of an off-duty of at least one of the transistors, a channel capacitance of at least one of the transistors, a switching frequency of at least one of the transistors, and a slew rate of at least one of control signals for the transistors.