Flash LED Driver Headroom Switching for Lower Energy Loss
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Solution Overview
Problem
Conventional flash LED drivers operate with a constant voltage headroom (VHR), leading to inefficient energy usage and increased manufacturing costs due to the need for larger field-effect transistors to reduce on-resistance, which is undesirable in size-reduction efforts and consumer applications.
Innovation Solution
A dynamic VHR system that adjusts voltage headroom based on a programmed brightness for LEDs, using a processing element to generate a partition control signal that switches transistors into or out of the signal path, reducing VHR without increasing transistor size, thereby enhancing efficiency and reducing energy waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a constant voltage headroom (VHR) is used in flash LED drivers, then the circuit operation is simplified, but energy efficiency deteriorates and manufacturing costs increase due to larger transistor requirements
Solution Approach 1:
The patent implements dynamic voltage headroom adjustment by switching between different transistor configurations (single transistor vs. parallel transistor pairs) based on the brightness code value. This dynamic reconfiguration allows the circuit to optimize energy efficiency at different operating points while maintaining operational simplicity through automated control.
Solution Approach 2:
The invention changes the electrical parameters (voltage headroom, transistor on-resistance) by dynamically switching transistor configurations. When the brightness code indicates lower LED forward voltage requirements, the system switches to parallel transistor configurations to reduce VHR and improve efficiency, whereas higher brightness codes use single transistor configurations.
2Loss of energy
If transistor size is increased to reduce on-resistance, then energy efficiency improves, but device area increases which is undesirable in size-reduction efforts
Solution Approach 1:
The patent segments the transistor functionality by using multiple smaller transistors that can be configured in parallel when needed. Instead of relying on a single large transistor, the system divides the current handling capability across multiple transistors, achieving low on-resistance only when required for specific brightness levels.
Solution Approach 2:
The system dynamically switches between single-transistor and parallel-transistor configurations based on operating conditions. This allows the circuit to achieve low on-resistance (and thus high efficiency) only when the brightness code requires it, rather than always using large transistors, thereby reducing overall device area.
3Loss of energy
If larger transistors are used to reduce on-resistance, then voltage headroom efficiency improves, but manufacturing costs increase
Solution Approach 1:
The patent implements dynamic switching between different transistor configurations based on the brightness code. This allows the circuit to achieve optimal voltage headroom efficiency only when required, rather than always using large transistors, thereby reducing manufacturing costs while maintaining efficiency when needed.
Solution Approach 2:
The system changes transistor configuration parameters dynamically - switching between single-transistor and parallel-transistor modes based on LED forward voltage requirements. This parameter change allows efficient operation at different brightness levels without requiring consistently large transistors, reducing manufacturing costs.
4Loss of energy
If voltage headroom is reduced dynamically, then energy efficiency improves, but circuit complexity increases
Solution Approach 1:
The patent implements dynamic voltage headroom reduction through automated switching of transistor configurations controlled by the brightness code. The circuit monitors operating conditions and dynamically reconfigures transistors to optimize efficiency, managing complexity through systematic control based on brightness requirements.
Data Source
AI summary
Aspects of the disclosure provide for a circuit including a binary-weighted DAC, a first transistor, a second transistor, a switch, a first current mirror, a second current mirror. The binary-weighted DAC is coupled between a first node and a second node and configured to receive a plurality of bits of a digital control signal. The first transistor has a source coupled to the first node, a drain coupled to a third node, and a gate coupled to a fourth node. The second transistor has a source coupled to the first node, a drain coupled to the third node, and a gate. The switch is coupled between the gate of the second transistor and the fourth node and configured to receive a partition control signal. The first current mirror is coupled to the third node and the second node. The second current mirror is coupled to the first current mirror.