OLED Display Power Supply Switching for Low-Power Efficiency
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Solution Overview
Problem
Buck-boost converters in OLED displays experience high switching losses and low efficiency during low-power operations, reducing battery usage time due to increased switching loss ratios, especially when operating in always-on display modes.
Innovation Solution
In low-power modes, the operation of the inverting buck-boost converter circuit is stopped, and a boost converter circuit is used to supply ELVDD of 4.6V and ELVSS of -2.3V, with a charge pump circuit converting the voltage to -2.3V, and a pulse voltage with a peak-to-peak ripple is produced to maintain efficient power supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If an inverting buck-boost converter circuit is used to generate negative-level voltage for OLED display, then the display can operate with proper voltage levels, but switching losses increase and efficiency decreases during low-power operations
Solution Approach 1:
The patent dynamically switches between two different power supply circuits based on display operation mode: using a boost converter circuit for low-power modes (AOD) and an inverting buck-boost converter circuit for normal modes. This dynamic adaptation allows the system to optimize efficiency for each operating condition, reducing switching losses during low-power operations while maintaining proper voltage levels during full operation.
Solution Approach 2:
The patent changes the operating parameters by selecting different converter topologies based on the required output voltage level and power consumption mode. For low-power modes, the boost converter with charge pump is selected to operate at higher efficiency points, while the inverting buck-boost converter is used for normal operation. This parameter-based selection resolves the contradiction between maintaining voltage levels and reducing switching losses.
2Use of energy by stationary object
If the negative-level voltage is lowered to -2V for low-power display operation, then power consumption is minimized, but the buck-boost efficiency drops to 60% or less
Solution Approach 1:
The patent segments the power supply function into two distinct circuits: a boost converter circuit for low-power modes and an inverting buck-boost converter circuit for normal modes. This segmentation allows each circuit to be optimized for its specific operating range, preventing the efficiency degradation that would occur if a single circuit had to handle both low-power and full-power operations.
Solution Approach 2:
The patent introduces a charge pump circuit as an intermediary component that works in conjunction with the boost converter during low-power modes. This intermediary mechanism enables the system to achieve the required negative voltage levels with higher efficiency than a standalone buck-boost converter would provide at low power consumption levels.
3Productivity
If the inverting buck-boost converter operates at minimum power consumption mode, then the display achieves low-power operation, but the switching loss ratio increases significantly
Solution Approach 1:
The patent implements dynamic circuit selection that adapts to power consumption requirements. During low-power modes (AOD), the system dynamically switches to the boost converter circuit configuration, which has lower switching loss ratios at low power levels. This dynamic adaptation directly addresses the issue of increased switching loss ratios during minimum power consumption operation, thereby extending battery usage time.
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 the efficiency of the power supply, increasing battery usage time by reducing switching losses and maintaining power supply efficiency in low-power modes.
Implementation Method 1
the power supply device may generate a positive-level voltage (e.g., ELVDD voltage) of about 4.6V using a boost converter
Implementation Method 2
a charge pump circuit converting the voltage to -2.3V
Data Source
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Figure 3A
AI summary
An electronic device is provided. The electronic device includes a display including a display driver integrated circuit (IC), a power supply device configured to supply driving power to the display, a processor operatively connected to the display driver IC and the power supply device, and a memory operatively connected to the processor. The memory may store instructions that, when executed, cause the processor to control the power supply device to supply different driving power depending on a display mode of the display.