Shift Register LED Driver With Flip-Flop And Register Cells
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Solution Overview
Problem
Existing solutions for driving LED arrays face challenges in accurately controlling individual LEDs, managing heat gradients, and providing diagnostic functionality for over-current protection and temperature sensitivity, especially in compact configurations with close pixel spacing.
Innovation Solution
A semiconductor device with a shift register comprising flip-flops and registers, connected in series and driven by a clock signal, allows for precise control of LEDs through a data signal, incorporating a common circuitry for communication and diagnosis, and utilizing current mirrors for efficient current regulation and protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a shift register with flip-flops and registers is used to control individual LEDs, then control precision is improved, but device complexity increases
Solution Approach 1:
The control system is divided into multiple cells, each containing a flip-flop and a register. Each cell independently controls one or more LEDs, allowing precise individual control while maintaining modular simplicity. The segmentation of control functions across multiple small units reduces the complexity of any single control element.
Solution Approach 2:
The patent introduces a temporal dimension to control by using sequential clock cycles to load data into flip-flops and then transfer to registers. This time-based control mechanism allows precise LED control without requiring complex simultaneous control circuits, effectively trading spatial complexity for temporal sequencing.
2Area of stationary object
If close pixel spacing is used in LED arrays, then area efficiency is improved, but heat gradient management becomes more difficult
Solution Approach 1:
The patent implements local quality by providing dedicated current control circuits for each LED or small groups of LEDs. Each cell in the shift register can independently adjust current parameters for its associated LED, allowing localized compensation for heat gradients without affecting the entire array. This enables tight pixel spacing while maintaining uniform temperature distribution.
3Reliability
If diagnostic functionality is added for over-current protection, then reliability is improved, but device complexity increases
Solution Approach 1:
The diagnostic functionality is merged with the existing control circuitry. The same shift register and control cells that drive the LEDs also monitor their operation. Over-current detection is integrated into the current control circuits, and diagnostic information is transmitted back through the serial interface, eliminating the need for separate monitoring hardware and reducing overall device complexity.
4Device complexity
If serial control through shift register is used, then device complexity is reduced, but control speed decreases
Solution Approach 1:
The patent uses preliminary action by pre-loading data into the flip-flops during the first phase of each control cycle. This allows the actual LED control to proceed at full speed during the second phase, as the data is already prepared in the registers. The serial loading happens in advance, separating the data preparation time from the execution time, thereby maintaining high control speed despite serial input.
Data Source
AI summary
A device for driving several light sources is suggested comprising a shift register comprising at least two cells, wherein an output of each cell controls one of the several light sources; wherein the at least two cells are connected in series and are driven by a clock signal; wherein each cell of the shift register comprises a flip-flop and a register; wherein the output of the flip-flop is connected with the input of the register; wherein the register is arranged to store the output of the register based on an update signal and wherein the output of the register controls one of the light sources; wherein the flip-flops of the at least two cells are filled with a data signal based on the clock signal; and wherein after a predetermined number of cycles of the clock signal the update signal is conveyed to the registers driving the light sources according to the values stored in the flip-flops of the cells.