One of the main requirements when designing any electronic devices, reducing power consumption. This applies especially to the mouth of the starters, fed by autonomous lane primary power sources such as batteries, saline or alkaline galvanic cells, when about duration of continuous operation devices directly depends not only on capacity power supply, but also on the load current consumption. Not wel Yes such power sources connected directly to the load current. As a general rule, most devices require a stable voltage and, therefore, requires stabilization of voltage jam, with high efficiency, otherwise the duration of continuous work ensuring uninterrupted will shrink.
Автора интересовало схемотехническое решение этой проблемы применительно к устройствам, питаемым стабильным выходным напряжением 5 В при токе нагрузки 50…100 мкА. При решении задачи сначала встал выбор первичного источника. Применение солевых или щелочных элементов подразумевает замену отработавших на новые. Это вполне допустимый вариант несмотря на некоторые финансовые расходы, но привлёк другой Наверное, у каждого из нас имеются, если не утилизировать как 01х0ды, отслужившие свой срок Li-Ion аккумуляторы. Например, от сотовых телефонов. Зачастую причина их неработоспособности — возросшее внутреннее сопротивление или частичная потеря емкости. Но при малом токе нагрузки внутреннее сопротивление не имеет особого значения, и такой аккумулятор может иметь даже заявленную производителем ёмкость. Вариант “бесплатного приобретения” такого источника питания меня вполне устраивал, а зарядка, например, раз в полгода, не представляла проблемы.
Since the operating voltage Li-ion (or polymer) battery-3.7 v, to obtain the required 5 to vyshajushhij converter, as already mentioned above, with relatively high efficiency. To build it, you can apply the thread of affordable and cheap impulse ful NCP1402 series converters. Unlike a close analogue of NCP1400A series, in which the output voltage is regulated by the proposal with the help of SHI-modulation (PWM) at a frequency 180 kHz, series NCP1402 applied frequency-modulation (PFM). When Ma small-scale loads this gives a gain in efficiency, since the switching frequency silo vågå key made 5ghzactivefet drops significantly (up to tens of Hz), and thus reduced losses and switching from several different parties instances MI Mick roshem NCP1402SN50T1 were conducting experiments on us 50 load currents. 100 µA. Typical Schematic of the converter on this chip is shown in the figure.
When cumulative 47 UH choke inductor (recommended by the manufacturer) and load current 50 µA (resistor 100 kΩ) current from the source — tat Lo 150 µA, Such EFFICIENCY was clearly too com. So were are the ex perimenty, the meaning of which was the measurement of EFFICIENCY for the specified load current and different inductances cumulative throttle. The impact of those, it turned out that maximum efficiency (78%) achieved with inductance choke 300 ... 600 μh. By trebljaemyj from the source current (80 μA) grew to throttle with induktiv fully outside the specified Ying tervala. All measurements were performed at a supply voltage 4 b. Accumulate neck choke L1-pin ES24 series. For another load current minimum inductance value can best choke should pick up pilot talno maximum efficiency.
Also revealed that straighten Le preferably Schottky Diode applied with the maximum permissible voltage 30th back Tog ... 40 in MRB0530LT1, for example. Application of diodes with less valid reverse voltage statement leads to a decrease in EFFICIENCY due to the influence of larger reverse current.
Author: With. GLIBIN, Moscow
Source: Radio No. 5/2017
