How many volts lcd backlight

When you first come across these code Browse our collection of articles, how-to's and guides on various lighting applications as well as in-depth color science articles. Other Posts. Things to know about flexible LED strip substrates When you look at and compare flexible LED strip types, you probably focus on the color temperature, LED count and pairing the correct po What is the difference between LED package types such as , , and ?

Oddly, when I put more of the strips in parallel the current doesn't increase linearly. All 3 strips only draws about mA. I expect that the supply has been a switched mode constant current supply. Output mA resulting in a V when all the leds are in series. The open voltage of such a supply is most probably higher. An LMHV in constant current mode with a supply of V could be a simple solution but does not solve the inefficiency.

If a high voltage switching supply is difficult you could try to connect the strings in parallel with 4 LM in constant current mode maintaining mA for each string and use a 33 to 35V DC power source for all of the strings. In that case the efficiency would be acceptable. Easiest solution would be to cut the strips at their 8 led sections.

With 4 sections, that's And even some common wall warts. You could drive them at a lower voltage as well, so a 24V laptop power can be used. Alternatively a boost regulator or a boost led driver can be used with any suitable lower voltage supply. It would seem that a series buck regulator to drop 60V from a bridge cap source with CC regulated is the most efficient.

Adjustable CC. Then with a series choke to smoothen the current, you now have a Buck regulator except the duty cycle is modulated to match sensed current with a PWM. If just one single led dies, and the strips are in series, no backlight. It seem high brightness can shorten LED life, especially if marginal cheaper ones were used in the design. The glue placement strips mean those raised of the backplate miss thermal cooling.

I also added a hole and threaded test wires to light some strips if one failed again. And when open, consider a speaker upgrade. Most have 3 speaker size mount points, meaning a quick screwdriver upgrade. Recycle Hint. Even junked ones contain perspex plates or diffuses.

Useful for picture frames,greenhouses or photographers. Figure 4. Nevertheless, in recent years, LED arrays can be found directly driven by an LLC or a Flyback system, while the voltage of the previous stage is adjustable by controller ICs.

Figure 5 is the application schematic diagram of a power solution. The RT, as a Current Regulator, provides constant current and dimming function. When the backlight module is turned on, the forward voltage, Vf, of the LED will decrease due to the increasing temperature. It will cause both the power dissipation and the temperature of the RT to rise.

Consequently, it will result in the decrease of overall efficiency and the failure of surface temperature requirement for the ICs.

Therefore, there must be a mechanism to make the boost converter lower down its output voltage. This voltage has a linear relationship with the LED current. If the pin voltage for that lowest-voltage channel is higher than the corresponding value in Figure 6, the RT V FB pin will be set high. Vice versa, if the pin voltage is too low, V FB pin will be set low and the output voltage will be pulled higher.

Figure 7 shows the schematic and the corresponding equations, which are based on the Superposition Theorem. For different applications, the wattages of their backlight modules will be different.

The power dissipations for ICs and power devices will thus be increased, which deteriorates the thermal performance. Compared to the power solutions for the backlights of notebook computers, the desktop monitors demand greater power.

For applications of even higher wattages, such as LCD TVs, even the drivers of current source devices will be connected externally in order to lower down the surface temperature of ICs.

The following lists Richtek LED backlight power solutions for various applications. All electronics products have specifications with regard to audible noises. When portable electronics products become more and more prevalent, the noise specifications for their backlight modules are even stricter.

The audible noises usually arise when the applications operate in PWM dimming mode. The noises mainly results from the resonance, caused by the output capacitance, MLCC, and the output current switch. The abrupt changes of the loads will increase the ripples of the output voltage. Such ripples to human ears are audible noises.

Figure 9 shows the waveform diagram of the RT when dimming. Figure 9. The waveform diagram of the RT when dimming. There are many ways to solve the problem of audible noises. Below are a few examples for users as references:.

Increase output capacitance values to reduce the output ripples: this method is simple and straightforward, but the drawback is the increase of cost. Change the PWM dimming frequency to avoid the audible frequency range, which is about 20 kHz. However, the drawback is dimming linearity will be compromised. Replace with an MLCC from the noise reduction solution: The output capacitance will affect how large the ripples are. Large ripples may cause resonance in between the layers, which will induce noises.

The noise-reduction capacitors have the superior performance over the cross-voltages, that is, less capacitance change at higher DC biases. Figure 10 shows the comparison of the equivalent MLCC capacitances between the new noise-reduction and conventional fabrication processes. Figure