Auxiliary Step-Up Circuit Stabilizes Ceramic Capacitor Voltage
Solution Overview
Problem
Ceramic capacitors used in liquid crystal display devices as smoothing capacitors for backlight voltage step-up circuits generate noise and deform due to voltage fluctuations, and alternatives like aluminum electrolytic or functional polymer capacitors have shorter lifespan, higher internal resistance, larger size, and limited temperature range.
Innovation Solution
A liquid crystal display device design incorporating a ceramic capacitor as the smoothing capacitor in the main voltage step-up circuit, with an auxiliary step-up circuit that compensates for potential changes using a coil, diode, and switching elements controlled by a main and auxiliary control circuit, stabilizing the ceramic capacitor's voltage and preventing deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a ceramic capacitor is used as the smoothing capacitor in the main voltage step-up circuit, then the device size is reduced and cost is lowered, but the capacitor generates noise and deforms due to voltage fluctuations during PWM control
Solution Approach 1:
The voltage step-up function is divided into two separate circuits: a main voltage step-up circuit and a sub voltage step-up circuit. The main circuit handles most of the voltage stepping up, while the sub circuit compensates for voltage drops during PWM control, preventing excessive voltage fluctuations that cause ceramic capacitor noise and deformation.
Solution Approach 2:
The sub voltage step-up circuit acts as an intermediary that compensates for voltage changes in the main voltage step-up circuit. When the main circuit's switching element turns off during PWM control, the sub circuit's switching element turns on to maintain voltage levels, thereby protecting the ceramic capacitor from harmful voltage fluctuations.
2Stability of the object's composition
If aluminum electrolytic or functional polymer capacitors are used as smoothing capacitors, then voltage stability is improved, but the lifespan is shortened, internal resistance increases, size increases, and temperature range is limited
Solution Approach 1:
By dividing the voltage step-up function into main and sub circuits, the system achieves voltage stability comparable to aluminum electrolytic or functional polymer capacitors while using a ceramic capacitor. This segmentation allows the ceramic capacitor to operate within safe voltage fluctuation ranges, thereby extending its lifespan and maintaining its superior characteristics.
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
Enables the use of ceramic capacitors, which are low-cost and compact, while maintaining stability and extending the lifespan of the LED driving circuit, reducing noise and maintaining performance across a wider temperature range.
Implementation Method 1
a coil of which one end is connected to a power supply, a main switching element which is connected between the other end of the coil and a ground potential
Implementation Method 2
a diode which is connected to the other end of the coil
Implementation Method 3
a smoothing capacitor which is connected to the diode, in which the smoothing capacitor is a ceramic capacitor
Data Source
AI summary
A main voltage step-up circuit includes a coil which one end thereof is connected to a power supply; a main switching element which is connected between the other end of the coil and a ground potential, and which is controlled by the main control circuit; a diode which is connected to the other end of the coil; a smoothing capacitor which is connected to the diode and is a ceramic capacitor; and an auxiliary voltage step-up circuit which is connected to the other end of the coil. The auxiliary voltage step-up circuit is ON when the main step-up voltage circuit is OFF, and compensates a potential change in the smoothing capacitor. The auxiliary voltage step-up circuit includes an auxiliary switching element which is connected between the other end of the coil and a ground potential; and an auxiliary control circuit which controls the auxiliary switching element.