Power Supply AC/DC OK Signal Control - Page 1
Forum section: electronics / beginners

author: renni1080
author_rank: Newbie
timestamp: October 13, 2020, 10:07:07 pm
content: Hi all, I am newbie about ac/dc converter logics. If you can help me , I will appreciate. I will combine 4 ac/dc converter ( 1000W ) by using parallel operation mode to create 4kW unit. I will add 4 leds to observe converter signal health. There are digital output including POWER ON SIGNAL, AC GOOD SIGNAL and POWER OK SIGNAL. I added related piece of datasheet. I want to ask that can I use these digital outputs to drive directly 5V LED or Do I have to use a external microcontroller (like Arduino) to determine HIGH/LOW state and drive LED by usign external microcontroller(like Arduino) digital outputs? And Which of ac/dc converter digital outputs(POWER ON SIGNAL and POWER OK SIGNAL) should I use to determine that ouput dc is OK? Datasheet : (https://product.tdk.com/info/en/documents/instruction_manual/ac-dc-converter/cpfe1000fi_apl.pdf),

author: Manul
author_rank: Super Contributor
timestamp: October 14, 2020, 12:16:14 am
content: From what I see, you want POWER OK SIGNAL because it is the combined signal of all.The proper, reliable way of indication would be to connect LED between +5V and PWR_OK. The LED should have aprox 470 Ohms series resistor added. It will light up if power is OK. The problem is, there is no +5V output (as far as I see) from the module itself, so you need to make +5V from the output (for example small dc/dc converter). +5V ground must be connected to COM terminal. Maybe you already have +5V. In that case it is straightforward to hook those LED's.

author: renni1080
author_rank: Newbie
timestamp: October 14, 2020, 07:05:37 am
content: Thank you for your answer. So I connect V+(28V) and PWR_OK signal , how can I handle that led turns on and/off. There is 5V source with 4.99 kohm pull-up. But I cannot make led turn off while Power is OK. I added a schematic that I understand from datasheet. What should I do to do proper operation with led and 28V without extra circuit?Is what I draw correct for that solution? 15.5 mA can make led turn on, Is 3.38 mA(if 1.8k is used as limiter resistor and LED forward voltage is 0 assumed for the sake of example) enough for turning on LED? Actually 3.38 mA could be enough to turn on led. How can I overcome this problem? ( If there is a missing point, can you fix me? and sorry for this questions I am newbie)

author: Manul
author_rank: Super Contributor
timestamp: October 14, 2020, 10:45:21 am
content: If you want LED to light up when power is OK, this circuit will not work. Because it will be light up in both conditions (just different current), because of 5k resistor to internal 5V. In fact it may be dangerous, because you are injecting some current into internal 5V, which may rise the regulated voltage. But I think this module allows some current to be injected this way.Anyway. If you want POWER OK = LED ON, then you need to have 5V as I wrote in the last post. Either by using dc/dc converter driven from main output or at least a resistor divider. Resistor divider may not be a solid solution, but if you do not want to invest a lot into this solution, it will be fine I guess. Something like 4.7K and 1K resistor will get you near 5V point from 28V output. Calculate yourself.

author: m k
author_rank: Super Contributor
timestamp: October 14, 2020, 11:02:21 am
content: For a health check you shoud get more info, it's >16A for 240V.I would use an MCU and read all of those signals.For some reason my Adobe Reader DC couldn't handle that datasheet.

author: Renate
author_rank: Super Contributor
timestamp: October 14, 2020, 01:21:09 pm
content: Manul is right, you can't feed the LED from 28 V, especially if you are trying to use that pin as a logic input.When the signal is off it will got to 20 V!(28v-5v-2v)*4.99kohm/(1.8kohm+4.99kohm)+5V = 20.433V(Presuming that the LED is about 2V.)Quote from: m k on October 14, 2020, 11:02:21 amYes, this has an I²C interface, why not read everything from all four supplies?

author: renni1080
author_rank: Newbie
timestamp: October 14, 2020, 02:02:17 pm
content: Yes you are right, if I connect led between 28V and PWR_OK , led will always turn on. But I realize that there is two different datasheet version. One of them says that PWR_OK signal is open collector output and other says that PWR_OK signal is internally connected to a 5V source via a 4.99kΩ pullup resistor. I added of two version of them in attachment. I checked from digikey and same smps in digikey have open collector output. I attached a design according to open collector. Is that correct that I can achieve my goal? Do I understand correctly?

author: Manul
author_rank: Super Contributor
timestamp: October 14, 2020, 02:58:33 pm
content: Yes, exactly, if it is just open collector without internal pull-up resistor - then all is good with your circuit, you just choose a series resistor for your LED (to limit the current) and thats all.Version with 5k pull-up to internal supply is a little bit different. I explained how it can be made to work. But yeah, it is not ideal if you want to drive LED, makes additional complication.Edit: One more question is if -V is connected to COM internally (I mean, is output referenced to COM or isolated / floating). I do not have time to look datasheet now. I expect that it is not floating, based on what you wrote about your experiment with LED.

author: renni1080
author_rank: Newbie
timestamp: October 14, 2020, 04:49:58 pm
content: Yes,page 12 tells that -V is connected to COM internally. So I have to correct which version smps that have open collector.

author: Renate
author_rank: Super Contributor
timestamp: October 14, 2020, 06:59:09 pm
content: It doesn't matter if there is or there isn't a pullup when they are so ambiguous.5 years from now when one of the PS blows up and you replace it and they decided that it will or will not have a pullup?Presume that there is no pullup.Presume that the output can't go above 5 volts.