如何提高降壓轉(zhuǎn)換器的輕負(fù)載效率與LDO

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　　設(shè)計(jì)一個(gè)DC / DC轉(zhuǎn)換器，只消耗微安培電流在無(wú)負(fù)載可以相比，以增加肌肉車與較輕的流體-你可能會(huì)得到它的工作，但它不會(huì)是容易的。在全負(fù)載電流的高效率在大多數(shù)現(xiàn)代DC / DC轉(zhuǎn)換器是司空見(jiàn)慣的，但是，實(shí)現(xiàn)高效率時(shí)，負(fù)載被禁用或斷開(kāi)仍然是一個(gè)困難和/或昂貴的任務(wù)。

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　　許多汽車和工業(yè)應(yīng)用需要高效率的12 V或24 V降壓電源轉(zhuǎn)換從主電源下降到負(fù)載點(diǎn)（電壓）在滿負(fù)荷電壓，但也需要非常低的電流消耗時(shí)，該設(shè)備是在空閑或關(guān)機(jī)狀態(tài)。為了實(shí)現(xiàn)這樣的低電流，您可以輕松地使用降壓轉(zhuǎn)換器（LDO）并聯(lián)降壓轉(zhuǎn)換器，以實(shí)現(xiàn)最小的電流從電池中汲取時(shí)，系統(tǒng)進(jìn)入輕負(fù)載/空載狀態(tài)。

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　　Ultimately， the ideal situation to prolong battery life in the system would be to disable every possible device from the input supply. In some cases though， a sub-regulated voltage is still necessary for certain components within the system to allow communication with other system blocks during the shutdown state （i.e. a CAN bus transceiver in an automotive application）。 DC/DC converters that are not specifically designed for light-load efficiency can consume several milliamps with no load. Additionally， converters that do exhibit high light-load efficiency will utilize frequency-foldback schemes and discontinuous mode operation， resulting in noisy output voltages and excessive EMI emissions. An LDO is ideal for light load situations because they can be designed to consume very low currents while maintaining a low noise output voltage. The no-load current into the input （also called “ground current”） can be on the order of a few micro amps or lower. Combining the performance of both converter and LDO， therefore， has obvious benefits.

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　　A simple method of using both in parallel is possible if the designer has the ability to disable the DC/DC converter when the loads will be minimal， i.e. using the same enable/disable signal for the converter that is used for the load. An example of this can be seen in Figure 1.

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