LED Driver Circuit Alternating Switches to Reduce Output Ripple
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Solution Overview
Problem
Existing light emitting diode (LED) driver circuits for LCD backlights suffer from output ripple due to switching operations, which affects image quality and power consumption.
Innovation Solution
A light emitting diode driver circuit that alternately switches a plurality of switch devices, including a first and second LED driving circuit, and a driving controller to control these switches to supply current to the LED array, minimizing output ripple by operating in either discontinuous or continuous current modes, and adjusting switching modes based on dimming signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If switching operations are performed in LED driver circuit, then current can be supplied to LED array, but output ripple occurs
Solution Approach 1:
The LED driver circuit is divided into multiple independent driving circuits (first LED driving circuit and second LED driving circuit), each with its own switch device. These segmented circuits operate alternately to supply current to the LED array, which distributes the switching operations and reduces the amplitude of output ripple compared to a single switching circuit.
Solution Approach 2:
The multiple LED driving circuits are configured to operate in alternating periodic cycles. The driving controller switches between different driving circuits in a periodic manner, so that when one circuit is switching, another is in a different state. This periodic alternation smooths the overall current output and minimizes output ripple while maintaining continuous current supply to the LED array.
2Manufacturing precision
If multiple switch devices are used to reduce output ripple, then image quality improves, but device complexity increases
Solution Approach 1:
Multiple LED driving circuits are merged into a single integrated driver circuit structure that shares common components such as the LED array connection, control logic, and power supply interfaces. This merging approach allows the use of multiple switch devices for ripple reduction while avoiding the full complexity of completely separate circuits, as the shared components reduce the overall component count and interconnection complexity.
3Loss of energy
If alternate switching is used to minimize output ripple, then power efficiency improves, but startup time increases
Solution Approach 1:
The driving controller is configured to perform preliminary simultaneous switching of all switch devices during the initial startup phase to quickly establish current flow and illuminate the LED array. After the startup period, the controller transitions to the alternate switching mode for normal operation. This preliminary action ensures fast startup while maintaining the energy-efficient alternate switching during steady-state operation.
Data Source
AI summary
A light emitting diode driver (LED) circuit and method are provided. The light emitting diode driver circuit includes an LED array; a LED driving circuit configured to supply current to the LED array through switching operations of a plurality of switches; and a driving controller configured to control the plurality of switches to supply current, corresponding to a dimming signal, to the LED array using a clock signal of a preset frequency. The driving controller may be further configured to control the plurality of switches to alternately perform switching operations.