Backlight Driving Circuit Soft-Start Time Reduction
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Solution Overview
Problem
The existing backlight driving circuits for liquid crystal displays have a long soft-start time, which affects the boot speed of display devices due to high switching losses and inrush currents, potentially damaging components.
Innovation Solution
A backlight driving circuit with a voltage detection circuit that adjusts the driving signal frequency to reduce the resistance value, increasing the charging speed of a capacitor and decreasing the current through the inductor and thin film transistor, thereby shortening the soft-start time and reducing inrush currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the driving frequency is set lower to prevent high switching loss and affect operating temperature, then the switching loss is reduced, but the soft-start time becomes longer
Solution Approach 1:
The patent applies dynamics by making the driving frequency adjustable rather than fixed. During soft-start, the frequency is dynamically increased to reduce startup time, while during normal operation it returns to the lower frequency to minimize switching losses. This is achieved through a frequency control module that responds to the工作状态 of the circuit.
Solution Approach 2:
The patent uses preliminary action by pre-charging the capacitor connected to the soft-start pin before the main switching operation begins. This preliminary charging action reduces the inrush current and allows the circuit to reach operational state faster without subjecting components to damaging current peaks.
2Reliability
If the duty of the driving signal is slowly opened during soft-start to prevent damage from high current, then component damage is prevented, but the boot speed becomes slower
Solution Approach 1:
The patent changes parameters during soft-start by temporarily increasing the driving frequency and adjusting the duty cycle progression rate. This allows the system to reach operational state faster while still preventing component damage through controlled current ramp-up. The parameters are automatically adjusted based on the charging state of the soft-start capacitor.
3Loss of time
If the resistance value is reduced to increase charging speed of the capacitor, then the soft-start time is reduced, but the current through the inductor and thin film transistor increases
Solution Approach 1:
The patent uses periodic action in the form of oscillating charging cycles during soft-start. The capacitor is charged in controlled periodic pulses rather than continuous DC charging, which limits the peak current through the inductor and transistor while still achieving rapid voltage buildup on the soft-start pin. This pulsed charging approach reduces thermal stress on components.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution reduces the soft-start time, decreases the current through the inductor and thin film transistor, and extends the service life by controlling the driving signal frequency and adding a voltage detection circuit to manage resistance values during boot-up.
Implementation Method 1
adds the voltage detection circuit of the soft-start pin, thereby controlling the driving signal frequency
Implementation Method 2
increasing the charging speed of the second capacitor, reducing the boot soft-start time
Implementation Method 3
decreasing the current through the inductor and the first thin film transistor
Data Source
AI summary
The present invention provides a backlight driving circuit and a method for reducing the soft-start time of the backlight driving circuit. The backlight driving circuit comprises a constant current driving chip 22, a first circuit part 24 which is electrically connected to the constant current driving chip 22, and a second circuit part 26 which is electrically connected to the constant current driving chip 22. In the backlight driving circuit and the method for reducing the soft-start time of the backlight driving circuit according to the present invention, it controls the driving signal frequency of the constant current driving chip to set the resistance value by adding a voltage detection circuit on the soft-start pin, and further changes the frequency of the driving signal of the first thin film transistor. During the soft-start time, it increases the charging speed of the second capacitor, reducing the boot soft-start time, decreasing the current flowing through the inductor and the first thin film transistor during boot time, and increasing the life time.