Power Supply 40-80V - LM317HV? - Page 1
Forum section: electronics / general

author: 9a6aag
author_rank: Contributor
timestamp: January 28, 2021, 01:50:54 pm
content: Hi, this is my very first post here, despite i am following EEV for years already....to jump on subject;I have a need of bench power supply for testing logic boards of battery chargers for golf cars, their logic monitors the battery charging voltage and operate with charging mode states depending on measured Voltage, some are working in range of 36V, most are at 48V and sometimes i have a need even of a 72Volt.....so in order to be able to test the logic boards i need to simulate "battery Voltage" that inputs the logic board to test does the logic works...including the auto shut down option when max charging Voltage is reached so as calibrating the charger....example; PCB of logic; MK115304As i have explained what and why do i need that high regulated voltage power supply here is a question;If i am using LM317HV with transformer with AC output 82Volts i did already get, after adding filter capacitor after rectifier i will get the peak Voltage up to 115VDC, will it damage the LM317HV if i am adjusting output voltage below 40V since i did read in datasheet that 317HV can operate in range of max 60V from max input to the min output measured average voltage, so does the peak voltage count or not ?!?My actual need is to have adjusting range from 36 up to 80Volt @ 200 to max 300mA, 500mA is more then enough....that would be ideal!!In order to avoid huge dissipation on LM, i would get out the wire from transformer secondary coil to make a 2 or 3 step AC outputs with a switch selector and get around 45, 65 and highest 82Volts, depending of what logic board i tend to use/test!!BTW, if anyone knows or have better suggestion or advice in sense of what LDO i could use, i welcome it

author: bdunham7
author_rank: Super Contributor
timestamp: January 28, 2021, 09:57:17 pm
content: Take a look at TL783. 200Vin, 125Vout, 700mA (not all at the same time, of course)https://www.ti.com/lit/ds/slvs036n/slvs036n.pdf?ts=1611870447572&ref_url=https%253A%252F%252Fwww.google.com%252FI just used one to convert a tube radio to DC operation at 108VDC from rectified line voltage. Watch the dropout voltage at full load as it approaches 20 volts (!) and you can use either transformer taps or dropping resistors to reduce thermal load at the various ranges. You'll need a good heat sink as well.

author: 9a6aag
author_rank: Contributor
timestamp: January 29, 2021, 07:56:32 am
content: TL783....just peeked in datasheet and seems thats the best answer so far despite it is one and only...thank you, thats exactly what i was looking for....btw, i wont use it below 35V, will do the minimum output voltage preset with series fixed resistor combined with VR so it never goes below 30-something.....35 up to 80 is my goal....for less then 35V i already have several lab power supplies 0-30VThanks once again

author: HB9EVI
author_rank: Frequent Contributor
timestamp: January 29, 2021, 12:47:37 pm
content: if you have a center tapped transformer, I'd stack 2 LM317HV; so one Vss->centertap, the second centertap->VddI'd also think about a switched mode supply due to the otherwise high losses/high temperatures creating there