New high efficiency white light emitting diode driver

This section uses three charge pump driver can drive up to 6 parallel connected light emitting diodes, ensure display backlight uniformity

Global power management technology leader National Semiconductor Corporation Ns (National Semiconductor Corporation) (New York stock exchange code: NSM) recently announced the launch of three does not need to add a new white light-emitting diode drive inductor. These drivers are most suitable for mobile phones, personal digital assistants, portable video games and MP3 media player, the advantage is to ensure that these electronic products display backlight uniformity. These three models are LM27951, LM27952 and LM27964 drive without the support of external inductors, so the light emitting diode system can be greatly reduced volume. In addition, the introduction of a number of high efficiency switching capacitor technology, which can further extend the battery life of portable electronic products.

The three white LED driver using dual gain structure, the utility model has the advantages of allowing regulators due to choose the appropriate input voltage / output voltage gain, so that regulators can give full play to its efficiency. The regulator will compare the input voltage and the forward voltage of the LED, and then decide which one to use.

National semiconductor power management product marketing director Mark Davidson said: because of this new chip dual gain structure, it can not only improve efficiency, but also helps to prolong the battery life of portable electronic products, coupled with the current distribution is very uniform, so as to ensure the brightness of the backlight display uniform thin portable system.

These white light-emitting diode driver can provide unified drive current, so that the input current of each light-emitting diode will not exceed 1%, to ensure that the display backlight brightness uniformity. LM27951, LM27952 and LM27964 are switched capacitor current driver, can be automatically selected to gain (1.5 times or 1 times), and three chips are also provided with a pulse width modulation (PWM) brightness control function. LM27964 chip also has a built-in I2C compatible interface to facilitate the control of the brightness of the light-emitting diode, and to ensure that the total output current up to 180mA.

National Semiconductor LM27951 and LM27952 white light emitting diode driver:

LM27951 and LM27952 chip is a charge pump driver, can drive up to 4 LEDs, and provide 30mA drive current for each light-emitting diode. The driver is provided with 4 output stable current supply sources, which can provide the same drive current for each light emitting diode to ensure the uniform brightness of each other. The size of the drive current can be set by external resistors. These drivers are suitable for 3.0V to 5.5V input voltage range, and only need to add 4 low-cost ceramic capacitors.

Since the LM27951 and LM27952 drivers use a dual gain structure with charge pump operation, it is possible to achieve high efficiency without the use of an inductor. The driver can select the gain (1.5 times or 1 times) according to the forward voltage required by the light-emitting diode, so the driver can play the highest efficiency in the specified input voltage range.

LM27951 and LM27952 drivers use constant frequency pre regulator, to ensure that the input signal conductance noise can be reduced to a minimum. Two drivers are fixed 750kHz switching frequency, which is the most suitable for portable electronic switching frequency. After the system shutdown, these two drivers only consume no more than 1uA of the supply current, help save electricity.

National Semiconductor LM27964 white light emitting diode driver:

LM27964 drive is a charge pump driver, can drive up to 6 parallel connected light-emitting diodes as well as a number of small keyboard light-emitting diode, the total output current up to 180mA. The internal current supply of the driver is very stable to ensure that each LED has a constant drive current.

LM27964 light-emitting diode driver has two sets of current supply source, each group can be independently controlled. There are a total of 4 LEDs for the main screen of the mobile phone, while the other one has a total of two LEDs that provide a backlight for the small screen. A small keyboard LED driver can drive up to 16 small keyboard LEDs, and can provide 5mA drive current for each light emitting diode. LM27964 chip is also built-in I2C compatible interface, allowing users to independently control the brightness of each light-emitting diode.

The LM27964 chip can be powered by a lithium battery, and can operate in a wide input voltage range from 2.7V to 5.5V. The driver can use a 1.5 fold gain or transfer (pass) mode with the charge pump operation, so without the use of inductors can also play a very high efficiency. In addition, the driver can also according to the requirements of the light emitting diode forward voltage, flexible selection of the appropriate gain to stabilize the current drive, so as long as the specified input voltage range, can be guaranteed to play the highest efficiency.

National semiconductor power management products

According to iSuppli in 2005 for the regulator / voltage reference circuit market survey shows that the national semiconductor is the world's largest supplier of power management integrated circuit, the market share of up to 14.1%. In the fiscal year of 2004, the U.S.