Backlight Control Circuit Frequency Setting for Temperature Adaptation
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Solution Overview
Problem
Conventional backlight control circuits for CCFLs in liquid crystal displays have a fixed startup frequency, which can be suboptimal at varying environment temperatures, making it difficult to maintain proper lamp lighting, especially at low temperatures.
Innovation Solution
A backlight control circuit with a frequency setting circuit that includes a temperature sensor, look-up table, encoder, and digitally adjustable resistor to dynamically adjust the frequency of the pulse control signal based on ambient temperature, ensuring the startup frequency remains optimal across temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed startup frequency is used in the backlight control circuit, then the circuit structure is simple, but the lamp cannot be reliably lit at low environment temperatures
Solution Approach 1:
The patent applies the dynamics principle by transforming the fixed frequency setting into a dynamic adjustable one. The frequency setting circuit includes a digitally adjustable resistor whose resistance value can be changed based on environment temperature, allowing the startup frequency to adapt to different temperature conditions. This resolves the contradiction by making the frequency dynamic rather than fixed, improving reliability without excessive complexity.
Solution Approach 2:
The patent applies parameter changes by modifying the resistance value of the adjustable resistor in the frequency setting circuit based on temperature parameters. The look-up table stores different resistance values corresponding to different temperature ranges, and the encoder adjusts the resistor value accordingly. This changes the electrical parameter (resistance) to adapt the frequency to environmental conditions, solving the reliability issue at low temperatures.
2Reliability
If the startup frequency is increased to ensure lamp lighting at low temperatures, then the lamp can be lit reliably, but the frequency may be too high at normal temperatures causing performance degradation
Solution Approach 1:
The patent applies parameter changes by storing multiple frequency parameters in the look-up table corresponding to different temperature ranges. When the temperature changes, the system selects the appropriate frequency parameter and adjusts the digitally controllable resistor accordingly. This ensures the startup frequency is high enough for low-temperature reliability but returns to optimal values for normal temperature performance.
Solution Approach 2:
The patent applies dynamics by making the frequency adaptive rather than fixed. The frequency setting circuit dynamically adjusts the resistance value based on real-time temperature detection, allowing the system to optimize performance for current environmental conditions. This resolves the contradiction between high frequency for reliability and optimal frequency for performance.
3Adaptability or versatility
If fixed resistor values are used in the frequency setting circuit, then the circuit is simple to manufacture, but the startup frequency cannot adapt to temperature variations
Solution Approach 1:
The patent applies parameter changes by replacing fixed resistors with digitally adjustable resistors that can change their resistance values based on temperature. The look-up table stores pre-calibrated resistance values for different temperature ranges, and the encoder automatically selects and applies the appropriate value. This provides temperature adaptability while keeping the manufacturing process relatively simple through the use of standard adjustable resistor components.
Solution Approach 2:
The patent applies preliminary action by pre-calculating and storing the optimal resistance values for different temperature ranges in the look-up table during manufacturing. This preliminary preparation allows the circuit to simply retrieve and apply the correct parameter when needed, rather than requiring complex real-time calculations. This maintains ease of manufacture while achieving temperature adaptability.
Data Source
AI summary
An exemplary backlight control circuit includes an inverter, a pulse width modulation (PWM) circuit, and a frequency setting circuit. The inverter is configured to provide an alternating current voltage to a lamp. The PWM circuit is configured to provide a pulse control signal to the inverter. The frequency setting circuit configured to regulate a frequency of the pulse control signal provided by the PWM circuit according to an environment temperature.