Скачать с ютуб #084 в хорошем качестве

#084

Features : Output : Adjustable (1.2 V to 37 V) Output Current : 1.5 A Load Regulation : 0.5 % Input Voltage MAX : 40 V Line Regulation : 0.04 % / V Maximum Operating Temperature : + 125 C Mounting Style : Through Hole Package / Case : TO-220 Linear Voltage Regulators are low-efficiency compared to switching mode regulators, which came around in the late 60s. If you know what a voltage divider with resistors does, imagine one of those resistors is a transistor, which is biased by how far off the output is to that desired. Pretty simple. Because all the load current has to flow through them, the greater the difference between the input & output voltage, the more heat needs to be dissipated, which is why they are larger, have heat sinks, etc. ("Without a heat sink with an ambient temperature at 50 ⁰C such as on a hot summer day inside a box, a maximum power dissipation of (TJ-TA)/RθJA = ((125-50)/80) = 0.98 W can be permitted. (A piece of shiny sheet metal of Aluminum with the dimensions 6 x 6 cm and 1.5 mm thick, results in a thermal resistance that permits 4.7 W of heat dissipation." ~ wikipedia link below). Also 0.04%/V regulation accuracy is pretty tight. Efficiencies can be compared to their switching mode counterparts in terms of expected efficiencies. With Linear Regulators, efficiency is a linear measure of the ratio between input and output voltages, where: Vout/Vin ratio is 0.1 = 10% efficiency Vout/Vin ratio is 0.5 = 50% efficiency Vout/Vin ratio is 0.9 = 90% efficiency [See this article for the chart, application circuits, etc.: http://cds.linear.com/docs/en/applica...] Q: Why would you ever use one of these over a switching regulator? "Applications Where Linear Regulators Are Preferable There are many applications in which linear regulators or LDOs provide superior solutions to switching supplies, including: 1. Simple/low cost solutions 2. Low noise/low ripple applications 3. Fast transient applications 4. Low dropout applications" There is no oscillator switching the output on & off, requiring large capacitance to try to smooth out the ripple. There is nothing causing ripple-just like in a resistor divider. I'm having a h*ll of a time with radio clones of chips like the nRF24L01+ that are notoriously sensitive to noise on their DCin, and I hope to create some bench/lab tests to compare this chip to the 7805, 1117, and other bench supplies I've made here. Will the cleanest regulation I can do at the component level help? Couldn't hurt! :) If you just want to go from 37vdc to 3.3vdc, use a switching mode regulator, as they will run cool at typically over 95% efficiency (less efficiency = heat (I2R) loss). For sensitive stuff that isn't behaving like you expected, try one of these $0.10 variable regulators and see if you find a difference... :) Thanks! pat :) reference: Datasheet: http://pdf1.alldatasheet.com/datashee... Wikipedia: https://en.wikipedia.org/wiki/LM317 10 LM317T for $1USD (delivered) on eBay: http://www.ebay.com/itm/New-10pcs-LM3... The complete PS I show at the end: http://www.ebay.com/itm/LM317-DC-DC-S...