Backlight Control Circuit Using Inverted Capacitor Topology
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Solution Overview
Problem
Existing backlight control circuits require high voltage rating capacitors to achieve high output voltage, leading to increased costs and limitations in the number of LEDs that can be connected in series or parallel, which restricts their application in larger displays.
Innovation Solution
A backlight control circuit design that uses a low voltage rating capacitor by electrically connecting the output capacitor between the output and input terminals, along with a noise filtering circuit and a power supply with low internal impedance to generate a high output voltage efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a high output voltage is achieved by using high voltage rating capacitors, then the output voltage capability is improved, but the cost increases
Solution Approach 1:
The patent inverts the conventional capacitor connection method by connecting the output capacitor between the output terminal and input terminal instead of between output terminal and ground. This inversion allows the capacitor to experience only the voltage difference (Vout - Vin) rather than the full output voltage, enabling the use of lower voltage rating capacitors while maintaining high output voltage capability
Solution Approach 2:
The patent changes the voltage parameter that the capacitor must withstand by altering its connection topology. Instead of the capacitor bearing the full output voltage stress, it now only experiences the voltage differential between output and input, effectively reducing the required voltage rating parameter
2Illumination intensity
If the number of LEDs connected in series is increased to achieve higher brightness, then the illumination intensity is improved, but the required output voltage increases requiring higher voltage rating capacitors
Solution Approach 1:
By inverting the capacitor connection from ground-referenced to input-referenced, the patent enables the system to achieve higher output voltages (for more series LEDs) without proportionally increasing the capacitor voltage rating requirements, thus supporting higher illumination intensity without the usual cost penalty
3Device complexity
If the output capacitor is connected between output terminal and ground as in conventional circuits, then the circuit structure is simple, but high voltage rating capacitors are required for high output voltage applications
Solution Approach 1:
The patent applies the inversion principle by reversing the capacitor's reference connection from ground to input terminal. This maintains relative structural simplicity while fundamentally changing the voltage stress characteristics, allowing lower voltage rating capacitors to be used in high output voltage applications
Data Source
AI summary
The present invention discloses a backlight control circuit, comprising: a voltage supply circuit, which is a boost converter circuit for receiving an input voltage from an input terminal and generating an output voltage to an output terminal, the output voltage being provided as an operating voltage for a plurality of light emitting devices; at least one input capacitor electrically connected between the input terminal and ground; and at least one output capacitor electrically connected between the output terminal and the input terminal.