Chopper regulators even out handheld backlights

Two new CMOS step-up chopper regulators respond to growing demands placed on components used in compact mobile devices.

With the market launch of its PQ6CU11X1APQ and PQ6CB11X1AP CMOS step-up chopper regulators, Sharp Microelectronics Europe is adding two efficient voltage regulators to its portfolio.

In so doing, the company is responding to the growing demands placed on components used in compact, mobile devices.

Increasingly, these components must satisfy competing demands, combining higher performance capabilities with lower power consumption and minimum space requirements.

In many portable devices, such as mobile phones or industrial handheld devices, the LED backlight is the component that uses the most energy.

Connected in parallel, the white light-emitting diodes can be powered by using a charge pump with a lithium-ion battery that supplies less than 5V.

The problem with this arrangement is that fluctuations in the required power supply to individual LEDs can cause variations in luminous efficiency.

This leads to significant variations in the brightness of the background lighting and, over time, reduces the lifespan of the LEDs.

The Sharp CMOS step-up chopper regulator offers an alternative.

This makes it possible to deliver exactly the same current to the LEDs which are connected in series.

The result is a very high and consistent luminous efficiency.

In contrast to LEDs that are connected in parallel, the step-up chopper regulator must generate a higher switching voltage of 24V, for example to activate a set of six LEDs.

The new component requires less energy than a traditional charge pump to increase the voltage provided by the battery.

This is achieved using low loss CMOS technology with the power MOS (LDMOS) structure.

In addition, the power required for switching is reduced considerably by the high degree of voltage isolation and the low internal resistance.

The step-up chopper regulator can generate an output voltage of up to 30V from an input voltage varying between 2.7 and 5.5V, with a 90% efficiency rate.

The available charge current ranges up to 250mA.

In standby mode, power consumption can be reduced to less than 1uA.

The high switching frequency of 1.2MHz provided by the oscillator chip integrated into the chopper regulator makes it possible to achieve particularly compact component dimensions.

The integrated overvoltage protection means it is not necessary to use an external Zener diode, which also substantially reduces the amount of space required on the printed circuit board.

This is an important feature as the trend in mobile devices is toward ever smaller models.

The new semiconductor chip therefore combines high performance with low power loss while saving space.

By using the step-up chopper regulator, the battery time in mobile handheld devices can be increased by up to 50% over that achievable with charge pumps.

With an eye on environmental management certification in accordance with standard ISO14001 and the RoHS Directive which becomes effective in 2006, Sharp is now offering this product exclusively as a "lead-free" alternative.

The PQ6CU11X1APQ and PQ6CB11X1AP components are now in volume production and can be obtained worldwide through Sharp's sales offices and distribution partners.

Back to top