OLED power supply design

Organic light emitting diode ( OLED ) The biggest characteristic is that it is from the light, do not need to back light and color filter, the thickness of the thinner than LCD. In addition, it also has a wider scope, faster response speed, low driving voltage, the color and contrast is relatively higher than LCD, can achieve more low consumption in theory, simple design, is widely recognised after LCD display star. The Oled has so many advantages, but its life is shorter than the LCD, because Oled is driven current from the luminous body, the material and component life is relatively short.

the power of the OLED specifications generally small size of the OLED needs a set of positive voltage ( Vdd) And a set of negative voltage ( Vss) Power supply, power supply architecture can be divided into two kinds of digital camera and a mobile phone architecture. Digital camera is power supply specifications: Vdd voltage range is 3 v to 6 v, Vss for - voltage range 7 v to - 10V; Mobile power supply specifications are: Vdd voltage is about 2. 5 v, Vss for - voltage range 7 v to - 10V。 And this two kinds of products of input power is usually a lithium battery, voltage range is about 3 v to 4. 2V。

digital camera Vdd solutions

the Vdd voltage range is 3 v to 6 v, so Vdd power architecture should be Buck/Boost or Boost. If we can't find the Buck/Boost the power of the architecture, also can use a very common Buck architecture, designs the Buck/Boost structure, using a set of normal step-down power control IC, as long as plus a MOSFET and one output diode, can be designed to Buck/Boost output, as shown in figure 1. The working principle of the voltage regulator is when Lx for high voltage, the slope of the inductor current according to the Vin/L increases; Lx for low voltage, inductance current according to the ( 输出电压+ VD) / L of the slope. Input and output current is discontinuous, it allows output voltage above or below the input voltage.

the designer may also directly with a group of Buck/Boost the output voltage of the power supply IC produce need, figure 2 is a set of l/step-down conversion IC directly. It combines a set of boost converter and linear voltage regulator, provide either booster, can also be step-down transformation scheme. This converter in the input voltage is higher or lower than the output voltage can provide a stable output, allows input range: 1. V 8 to 11 v, can be preset to 3. 3 v or 5 v output, also can use two partial pressure resistance, be adjustable output voltage: 1. 25 v to 5. 5 v, the efficiency can reach 85%. If you need 3. Between 5 v to 4 v output, you can use boost converter combined with linear regulators. Such as: MAX1606 boost converter with combination of MAX8512 linear regulators.

from the perspective of cost reduction, can choose to charge pump, no need for inductance and output diodes, such as MAX1759 l/step-down structure is used in charge pump to produce a stable output. Despite its working frequency is higher than 1. 5 MHZ, still can maintain a low static current to 50 ua. Some designers in pursuit of high conversion efficiency, chose the way of booster, produce a stable output of a group is higher than the input, as shown in figure 3 booster architecture. Due to the power switch MOSFET is external, can provide greater output power. Under the condition of the power output of a license, you can also choose a built-in booster of MOSFET power switch converter, such as MAX1722, can save a space effectively, reduce the cost.

phone Vdd solution for mobile phone Vdd, can choose the Buck circuit provides the voltage needed to. Figure 4 is a built-in MOSFET power switch synchronous buck structure, provides the output current of 400 ma. Working frequency up to 1. 2 MHZ, allowing designers to choose the small size of capacitance, inductance and output efficiency is as high as above 90%.

negative voltage Vss solutions as mentioned above, if a designer temporary find a negative voltage output power IC, can also use the Buck power IC. As shown in figure 5, the suspension grounding produces negative voltage Vss architecture, its principle is: the normal output meet the input power, from the converter to the stability of the negative pressure output, if you need a different output voltage, can be between two jumper in the output resistance and FB, set the output voltage.

can also choose to load voltage output converter, and figure 6 is the commonly used PWM converter, negative pressure external components, design simple, less work in fixed frequency PWM structure interference is smaller.

conclusion although OLED is the emerging technology industry, the specification is not very clear, but the power supply architecture basically remain unchanged. ISuppli research shows that the display from monochrome to color, under the demand of OLED display market is expected to reach $1 billion in 2006. OLED is illuminated, the advantages of the ultra-thin become DSC, choice of handheld game consoles or mobile phones and other products, these products provide development prospect extremely. In a word, technology and market potential is a key factor in an industry to grow. Technically, OLED domestic manufacturers effort is appreciated, if you can further enhance the brand effect, product positioning on the strength, will stand in the OLED industry gradually take off the remarkable position.