September 06, 2012

Low pressure difference linear voltage regulator

LDO low dropout regulator, meaning low dropout linear voltage regulator, is compared with the traditional linear regulator. The traditional linear regulators, such as 78xx series chips are required to input voltage to output voltage higher than 2v~3V above, otherwise it can not work normally. But in some cases, this condition is obviously too severe, such as 5V 3.3V, Dynamic LED luminous characters input and output of the differential pressure of only 1.7V, is clearly not meet the conditions of. In this case, only the class LDO power conversion chip.

LDO is a linear regulator. Linear regulator used in the linear region of operation of the transistor or FET, from the application of the input voltage is subtracted from the excess voltage, LED thermal resistance factor to produce a regulated output voltage. The so-called drop voltage regulator, refers to maintain the output voltage at its rated value 100mV is required within the input voltage and the output voltage of the minimum variance. Positive output voltage regulator ( LDO low voltage drop ) usually use the power transistor ( also known as transmission equipment ) as PNP. This transistor to allow the saturated, so the regulator can have a very low drop voltage, usually about 200mV; compared with the use of NPN composite power transistor,ITO chip application in LED the traditional linear regulator of pressure drop of about 2V. Negative output LDO uses NPN as its transmission device, its operation mode and positive output LDO PNP device similar to. Update on the development of the use of CMOS power transistor, it can provide the lowest pressure drop voltage. The use of CMOS, through the regulator voltage drop is the only power equipment load current resistance caused by ON. If the load is small, the resulting voltage drop of only a few tens of millivolts.

DCDC is a DC to DC ( to ) ( different DC power transformation of values ), as long as consistent with this definition can be called DCDC converter, including LDO. But the general argument is that the DC ( to ) by means of DC switch device called DCDC.

LDO is a low pressure drop point, Fiber optic lighting it has an explanation: pressure drop ( LDO ) linear regulator of low cost, low noise, small quiescent current, which is its outstanding advantages. It requires external components are rare, usually only need one or two bypass capacitor. The new LDO linear regulators can achieve the following indexes: the output noise of 30 μ V, PSRR for 60dB, the static current of 6μ A, voltage drop of only 100mV. LDO linear regulator performance can reach this level, main reason depends on the adjustment of pipe is used P channel MOSFET, but the common linear regulator is the use of PNP transistor. P channel MOSFET is driving voltage, electric current is not needed, so greatly reduces the device itself current consumption; LED Dimmer Switch dab5d58ck on the other hand, using the PNP transistor circuit, in order to prevent PNP transistor saturation and lower the output capacity, between the input and output of the voltage drop can not be too low; and P channel MOSFET the voltage drop is roughly equal to the output current and the on-resistance. Because MOSFET conduction resistance is very small, so it 's very low voltage drop.

Posted by: GIGI858 at 08:58 AM | No Comments | Add Comment
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