At present, many electronic devices with built-in displays use W LED type backlights. If you do not really understand the implementation methods and advantages and disadvantages of various methods, it is not easy to find the correct LED dimming method. This article will briefly explain the power supply mode of the LED, and then describe the two LED dimming methods and their advantages and disadvantages. Through this information, you can select the appropriate dimming method and LED driver IC for application.
Configure the voltage regulator converter to achieve WLED power supply
The brightness of the WLED changes linearly with the passing current. To achieve optimum WLED current accuracy and uniform brightness for each serial, the LED driver should adjust the current and voltage through the LED instead of adjusting the current and voltage across the LED. Figure 1 shows how the current-regulated DC-DC converter that resets any adjustable output becomes a stable power supply to drive the series in parallel with the output being greater than the sum of the LED forward voltages and the voltage (VLED) falling. Multiple WLEDs.
After adjusting the voltage across the current-sense resistor (RSENSE) (VSENSE) instead of the output voltage (VO), the driver stabilizes the power supply so that the VO can self-adjust as the ΣVLED changes due to voltage and temperature. The voltage drop of WLED ranges from 3 to 4 volts. This drop is directly affected by the LED current and is inversely proportional to temperature. Recent low-power drivers have replaced external sense resistors with one or more current sinks, especially single junction field effect transistors (FETs) (Figure 2).
The driver has two functions, not only to adjust the driving voltage of the FET to achieve the appropriate current (relative to the bias current) through the FET, but also to adjust the integrated DC-DC converter (usually a boost converter) The output power is such that the FET has the lowest germanium source voltage required for this current. This type of driver with an integrated boost converter and eight integrated current sinks, one of which is the TPS61195.
Eliminating noise is the primary issue of PWM dimming
In order to improve the display effect and optimize the LED driver efficiency of different ambient lighting brightness, a new dimming range can be achieved compared with the new LED backlight electronic device. There are two ways to use LED dimming: pulse width modulation (PWM) dimming and analog dimming (Figure 3).
For PWM dimming, a digital signal processor (DSP) or microcontroller (MCU) transmits PWM signals of different duty cycle (D) to enable and disable the WLED driver converter for the driver shown in Figure 1. Or enable and disable current intrusion for the driver shown in Figure 2. Therefore, the average current through the WLED series is equal to the duty cycle multiplied by the maximum current, ie ILEDavg = D x ILEDmax.
Since the maximum current through the LEDs is the same, the PWM dimming results will exhibit a fairly linear change in brightness. In addition, since the spectrum of the LED illumination changes due to the voltage drop, and the voltage drop varies due to the ILED that maintains the maximum value, the chromaticity of the LED backlight (ie, the color, hue, or actual white light level) is used. Excellent results can be achieved with PWM dimming.
The key drawback of PWM dimming is noise. If the PWM signal is used to enable and disable the converter, the upper limit of the dimming ratio of the driver is limited by the time required to start the converter, charge the output capacitor, and reach the maximum individual current. Even if the WLED driver is capable of operating the converter at a switching frequency above 1 MHz, the control loop response time and/or startup time of the converter can take hundreds of microseconds to several milliseconds. Therefore, in order for the driver to have time to reach the maximum current, the PWM dimming frequency can only be a factor of 100 Hz.
The piezoelectricity of the ceramic output capacitor causes the capacitor to charge and discharge in the audible noise range (20k to 20kHz) at the PWM signal frequency. At this time, the capacitor will vibrate and the capacitor and printed circuit board will generate noise due to vibration. . The degree of vibration, the amplitude of the voltage change, and the size of the ceramic capacitor package are proportional, so reducing the size of the capacitor package reduces noise.
Electric Kettle
Electric Kettle are made by food grand stainless steel and
Polypropylene. It helps you to have a 1.8L bottle of boiled water in 5 minutes.
Type 201 Stainless stell is the main material for the electric kettle housing.
sometimes called a tea kettle or teakettle, is a type of pot, typically metal,
specialized for boiling water, with a lid, spout, and handle, or a small
kitchen appliance of similar shape that functions in a self-contained manner.
Kettles can be heated either by placing on a stove, or by their own internal
electric heating element in the appliance versions.
Features:
360-degree swivel base: Great way with
cordless pouring; kettle lifts off base for cord. Separate base to move kettle
conveniently, 360°rotation design.The cord can be wrap neatly into the base
bottom for easy storage. The concealed stainless steel heating element brings
fresh hot water with no metal Taste.
Soft Handle for easy using: Comfortable
stay-cool handle; brushed stainless steel finish. Cool-touch buttons and
ergonomic stay-cool handle.
Large Capacity for Multiple Cups: 1.8 L large
capacity, with Max. water level inside the kettle. almost 1.5x the size of most
tea makers. Brew up to 6oz at once! Perfect for small gatherings & parties!
Fully Stainless Steel Faster Boils: Stainless
Steel Interior cover with no plastic taste. Boils water rapidly, save more time
and energy. Faster than the microwave & safer than your traditional
stovetop teapot.
On/off switch with LED light.: Automatic
On/Off switch makes life easier. No need standing by for hot water. It shuts
down when reaches a full rolling boil. Boil-dry and overheat protection to
ensure the safety use.
Time Saver & Higher Safety: 1500 watts
energy efficient for quick heat-up time brings water to a boil, Fast boil, auto
shut off and boil dry protection technology with three-prong plug.
Brushed stainless steel housing
Applications
Making hot water for tea brewing.
Making Coffee.
Cool milk-tea.
Steaming eggs.
Any occation if you need hot water in short time.
Any
color of plastic is available to produce but in big quantity. Its
Electric Kettle
Electric Kettle,Stainless Steel Electric Kettle,Electric Boiler,Big Capacity Electric Kettle
Guangzhou Taipeng Electrical Appliances Technology CO., LTD. , https://www.kettles.pl