标签：residential LED lights

residential led lights and OLED Use

OLED and led lights, also known as OEL (Organic Light-Emitting Devices). This device has a self-luminous, clear and bright, thin, fast response, wide viewing angle, low power, low cost, simple manufacturing process, characteristics of its inception, has been regarded as the most promising after the following LCD display. Currently, cellular phones, personal assistants (PDAs), digital cameras and other areas, OLED has been widely used, but very strict requirements for OLED power bias circuit, generally require high efficiency, small size, light weight the step-up transformer step-up transformer should also have good electromagnetic compatibility.

The MAX8570 is a MAXIM company launched the OLED step-up transformer chip. It is not only advanced design, perfect function, and the external circuit is simple, very flexible to use, design OLED power bias circuit is an ideal device.

Characteristics and working principle of the MAX8570 converter The MAX8570 converter characteristics

The MAX8570 converter main features are as follows:

(1) The chip power MOSFET, energy-saving circuit, control logic circuit and protection circuit integrated to simplify the peripheral circuit design, reduce costs, enhance system reliability;

(2) Working frequency up to 800kHz, allows the use of miniature table-mount components;

(3) ultra-low power consumption: quiescent current is 25mA, in True shutdownTM mode, current consumption as low as 0.05μA (typical);

(4) open-circuit protection to prevent the output capacitor and load damage;

(5) allows the use of the battery, the output voltage up to 20V, to meet the high voltage requirements of the OLED power bias circuit. working principle

(1) control mode

Figure 1 shows the internal block diagram of the MAX8570. When the MAX8570 power its chips inside the P-channel MOSFET on, the power supply voltage VCC through the inductor L1 is divided into two: one sent to the drain of the internal N-channel MOSFET, another path VD1 to C4 charge. When the N-channel MOSFET on, the current flowing through L1 gradually increases from zero, while the electrical energy stored in L1, once the current limit is reached, the N channel MOSFET turns off, L1 current by VD1 the load. In the way of the switching frequency will vary with the size of the load and supply voltage of up to 800kHz.

(2) shutdown (SHDN)

SHDN pin is pulled low, the device will enter the True shutdownTM Mode (off state), in True shutdownTM mode, the circuit’s current consumption as low as 0.05μA output and the input is disconnected, the LX pin is in high resistance state in the conventional boost converter circuit, the converter shutdown, the output and input will always be through the inductor and freewheeling diode connected to the load to draw some power from the input. The MAX8570 converter with True Shutdown, in True shutdownTM mode, it will make use of a P-channel MOSFET switch to disconnect the input and output, thus eliminating the shutdown, the power drawn from the input side.

residential led lights and OLED Use

(3) separate to the inductance power supply

Can be a separate supply of the IC and the inductor, the inductor supply voltage range of 0.8-28V, as shown in Figure 2 is a separate application to the inductor supply circuit, this circuit structure of the SW pin should be vacant, so that the power supply directly connected inductance, then output and input is disconnected, but no longer shutdown shutdown, the output voltage than the low inductance power supply voltage one diode drop.

(4) soft-start

When in True shutdownTM function, the circuit will slowly open the gate of the internal P-channel switch, to be fully open SW, the internal N-channel switch turns on, so to avoid inrush currents when VFB is lower than 0.5V , the internal N-channel switch off-time from 1μs to extend to 5μs, to control the inrush current.

(5) open-circuit protection

Open-circuit failure occurs when the upper feedback resistor or external diode The MAX8570 converter will immediately stop switching, in order to avoid too much damage to the output filter capacitor and load output voltage.

OLED power bias circuit design

The limit the current settings

Design, according to the following formula to estimate the value of the limiting current:

Where, POUT (MAX), maximum load power; VBATT (MIN) is the minimum supply voltage; POUT (MAX) for the maximum converter output voltage.

The output voltage setting

The MAX8570’s output to GND is connected between a resistor divider between the point then the FB voltage divider ratio determines the output voltage (the voltage adjustment range for the VCC-28V), the range of R2, 10-600KΩ So according to the following formula R1:

In order to improve the accuracy of the output voltage, VFB 1.266V; value of VOUT VCC to 28V, the design should be to ensure minimum bias current flowing through the feedback resistor 2μA.

The inductance of the Select

The inductor is a key component of the boost converter, its value directly affects the size of the normal work of the entire circuit. If you need to pursue a high-performance, the best choice for low inductance and inductance, MAX8570 work in the lower frequency, the inductor will produce magnetic saturation, causing ripple current increases or damage to the inductance, it is in the choice of inductance , according to the output current The MAX8570’s operating frequency of the inductor, the inductance of the rated current and ripple voltage conditions to the decision here Recommended inductor values ​​range from 10-100μH.

The diode of choice

Diode switching losses to a fifth sixth of the total system loss is a major factor affecting the efficiency of the boost converter, including forward losses and reverse recovery loss, and recommend the use of a fast recovery time and forward voltage small drop of the Schottky diode, the rated current value should be greater than the peak switch current, reverse breakdown voltage greater than the output voltage. The Schottky diode MBR0520, MBR0530, ZHCS400.

The capacitance of the Select

The output capacitor can maintain the output voltage can also smooth the ripple voltage due to MOSFET switch (N-channel MOSFET on the output capacitor to the load). Therefore, under the premise of ensuring sufficient bandwidth, you should select ESR (equivalent series resistance) ESL (series equivalent inductance) is small, high pressure value of the output capacitor such as X5R or X7R dielectric material in ceramic capacitors, most applications, circuit design, its capacity is desirable 1μF.

The input capacitance is mainly used to filter out the ripple voltage in the power supply, it is recommended that ceramic capacitors with X5R or X7R dielectric materials, capacitance values ​​between 1-6.8μF.

Increase a feedback capacitance, and improve the stability of the output voltage, it is recommended to use a 47pF ceramic capacitor in the the MX85701 output and FB.

Misunderstandings of residential LED lights (2)

LED tubes:

The working principles of fluorescent lamps determined their tubular structures. Lamp bases applied to filament lamps cannot be used on fluorescent tubes. However, fluorescent tubes were widely used, in spite of the oversized lamp body and noise coming from ballasts. Because fluorescent tubes have a most important advantage: energy saving. Designers continued to use the design concept of fluorescent tubes, and created LED tubes. However, this tubular structure has nothing to do with principles of LEDs, just a copy of the traditional design concept. The oldest fluorescent tubes are T10 tubes. In order to improve the lighting efficiency, designers then invented T8 fluorescent tubes. Until today, T5 and T4 tubes have been used in many places. According to the working principles of fluorescent lights, the longer and thinner the lamp body, the better the lighting effect. Thus diameters of tubes became smaller and smaller. However, it does not mean that this kind of design is also suitable for LED tubes. As a type of residential LED lights, LED tubes cannot work in high temperatures. Designers did not take this into account. From the oldest T10 LED tubes to T8 LED tubes and nowadays T5 LED tubes, the cooling system has become the biggest problem for LED tubes designers. It is not to say that LED tubes cannot be made as tubular structure. But they should have their own sizes and shapes, which is consistent with their own characteristics.

 

The working principles of fluorescent lamps determined their tubular structures. Lamp bases applied to filament lamps cannot be used on fluorescent tubes.

 

LED High Bay bulbs:

LED bulbs are the oldest residential LED lights in LED lighting industry. However, there are a lot of unreasonable places in their shape designs. For instance, LED chips have much better lighting efficiency, but designers applied opaque covers which obstruct up to 30%-50% lights. This is a rather ridiculous design. Similar to LED tubes, LED bulbs is another LED lamps that followed the design steps of traditional filament lamps. These spherical-shaped LED bulbs actually go against working principles of LEDs. Designers have to reduce the entire volume of cooling sections to have this shape. As a result, most currently used LED bulbs are low powered, with limited luminous flux. Under such circumstances, designers still use opaque covers to reduce brightness further, it is really ridiculous.

 

Misunderstandings of residential LED lights (1)

LED used for residential purpose, who will be replaced?

With the continuous development of LED lighting technology, the luminous flux of LED lamps becomes higher and higher. Nowadays, many LED technique has been used in outdoor lighting, not to mention indoor lighting. Residential LED lights occupy more than 40% in current indoor LED lighting market. There is no doubt that traditional filament lamps have regularly replaced by LED lamps. No matter in energy-saving area or in lighting effect area, LED lamps are much better than filament lamps. What about other traditional lights? What about fluorescent lamp and energy-saving lamps? Can LED lamps shake their positions? LED lighting technique has many advantages, compare with traditional lighting. However, LED lamps should not follow the steps of traditional lamps. Take LED bulbs for instance, they have much similar shapes with filament bulbs.  Designers have to reduce the volume of radiators to keep this shape. That is the main reason why high powered LED bulbs cannot be found in the market. If we can get rid of the restrictions coming from traditional design, take full advantage of LED technique, LED lamps will replace fluorescent lamp and energy-saving lamps in the future.

 

With the continuous development of LED lighting technology, the luminous flux of LED lamps becomes higher and higher.

 

LED spot lights:

Ф5 MR16 spot lights are obsolete. Designers misunderstood the requests and lighting effect of spot lamps, as well as “MR”. They just used MR16 lamp cups as covers. As a matter of fact, LED spot lights can also be made by other lamp cups. Nowadays, substitutes of MR16 LED spot lights use aluminum plates as radiators. People still call them MR spot lights. Only a small part of LED spot lights are used as residential LED lights. Some of them are used for decoration purpose. Usually, this type of spot lights can create beautiful spots on the ground, and enhance the aesthetic effect. Most of them are used for focus lighting. This type of lamps needs a very strong condensation effect. Different from the parallel rays emitted by searchlights, LED spot lights used for focus lighting always have very strong light intensity in the middle of the beam. The external light should be soft. Ф5 MR16 spot lights cannot create such lighting effect.

The constant and rapid development of residential LED lights in China

According To rough estimation, the proportion of global lighting electricity consumption is as much as 20% within total global electricity consumption. Up to 90% electrical energy was converted into heat energy (wasted). This amazing data shows us that traditional energy-saving lights are actually incompetent. And meanwhile, more and more evidences prove that LED lighting technology plays a significant role in energy saving projects promoting all around the world. However, focus always is a money-making point. Governments from the countries all over the world tended to pay their attention on this new type energy-saving and environment friendly lighting technology. At the same time, business men from these countries also started their LED lighting business strategy. Invariably, they made their start point in residential LED lights.

 

According To rough estimation, the proportion of global lighting electricity consumption is as much as 20% within total global electricity consumption. Up to 90% electrical energy was converted into heat energy (wasted).

 

It is understood that the advantages of LED lighting is obvious compare to traditional lamps, higher luminous, more efficiency, a longer life, etc. The luminous efficiency is 2.5 times as much as fluorescent lamps, 13 times as much as filament lamps. This advantage is more obvious in residential LED lights. After ten years developing, LED lighting technology has showed a sign of mature, especially in residential LED lighting area. Not mention Shanghai and Guangzhou, there are more than 100 large-sized LED manufactures emerged in Jiangsu Province in past ten years. Over 70 among them are manufacturers for residential LED lights. “LED has a higher content of technology. The interaction between people and light is possible as a result of intelligent lighting design. This cannot be realized by traditional lights. Another point, LED performs a very strong decorative function, which is significant in residential LED lighting. With the improvement of living standard, people tend to choose products which are both practical and aesthetic. They don’t care about the price. Actually, the price of LED lamps is not much more expensive than that of traditional lamps.” Said Qiang Wang, a designer from a household LED lighting companies in Wuxi.

 

Energy crisis gives birth to energy saving and environment protection awareness, and also promotes the development of global LED lighting industry. Experts are always optimistic about the LED high bay market. They believe this is a market with strong potential. The constant and rapid development of Chinese LED lighting business is also affirmed. Not only in residential LED lighting industry, but also in other LED lighting business, like outdoor landscape lighting and entertainment lighting.