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Recent content by Cecemel

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    Design of an isolated dc-dc power supply

    Hi, thanks for your replies. Treez, I’ll look into the files you’ve sent once I’m at my laptop. Application is a 64 cell li-ion active balancer, my plan is to step down the pack voltage from 190-260v (3-4.1 per cell) to about 5v while isolating it. Then use a buck converter to regulate balancing...
  2. C

    Design of an isolated dc-dc power supply

    Hi, I need a 100-150w isolated power rail. Here’s how I would probably try to achieve this: drive a transformer with a half bridge and a 555 generated high frequency square wave, rectify the output of the transformer, add a capacitor, use a linear or switching converter to get a more stable...
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    LTspice Wolfspeed mosfet model doesn't seem to be working

    Thanks for your replies. Connecting Tj and Tc to ground fixed my issue. I thought I could leave them floating because when searching the internet for a fix, I came across this manual. On page 7, it says Tj can be left floating, and it says Tc can be left floating, but I failed to read the...
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    LTspice Wolfspeed mosfet model doesn't seem to be working

    Hi, I've set up a simple circuit in LTspice using a model of Wolfspeed's C3M0075120K. I'm feeding the gate a square wave but I'm only seeing tiny current spikes at rise and fall going through the mosfet. This probably isn't the ideal way to drive a mosfet, but it's just a simple test I set up...
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    Calculating switching losses of a mosfet when switching energy is not given

    Thanks for your replies. I guess what it comes down to is that it's quite hard to calculate switching losses as they depend on a lot of factors, and that the calculations from my first post are about twice as high as a typical worst case scenario because they assume max voltage and current...
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    Calculating switching losses of a mosfet when switching energy is not given

    Thanks for your reply. I don’t really understand what you’re saying. Could you please elaborate or maybe give an example for this mosfet at say 500V and 10A drain-source driven by a 1kHz square wave?
  7. C

    Calculating switching losses of a mosfet when switching energy is not given

    Hi, The title pretty much says it all. I’m not sure what factors these losses are based on. I saw somewhere you need to multiply the sum of the rise and fall time by the drain-source voltage and current, but I don’t think the losses are this high. Thanks
  8. C

    How do i check whether an I2C device works?

    The master is working, I know that because the onboard barometer (I2C slave) works. I’ve been doing some more research and came across an Arduino I2C Scanner sketch. It says it found a device at address 0x0E, so I guess now I just need to find out how I can change the magnetometer address in my...
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    How do i check whether an I2C device works?

    Hi, I ordered a gps and magnetometer module from eBay for my quadcopter. The gps works fine, but i can’t get the I2C mag to work. (I’m using a Matek F405-CTR running iNav.) Before i ask for a replacement and have to wait for shipping from China, i would like to make sure this one really is...
  10. C

    Transistor max power?

    Thanks but i don’t fully understand, could you give an example with a circuit like this?
  11. C

    Transistor max power?

    Thanks for the replies, cleared up a lot. So basically the 94 watts is the max output of R*I(squared) assuming you have an ideal heatsink. I’ve heard that the switching of the transistor generates heat as well, is there an easy way to calculate this?
  12. C

    Transistor max power?

    Hi, I’ll use the irfz44n as an example to explain what i would like to know. On the datasheet it sais max current is 49a, max voltage is 55v, resistance is 17.5mOhms and max power dissipation is 94w. When you calculate heat being produced, you get about 42w. I’m pretty sure that’s more than...
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    Effects of antenna shape and smps interference

    Hi, I’m hacking a pair of walkie talkies (446MHz) and i was wondering whether bending the antenna (90 degrees to the left, to fit the new case) would affect the range. I don’t think so but i just wanted to make sure. Also, there will be a 100kHz boost converter right next to it, will this...
  14. C

    4ohm speaker with 8ohm amplifier

    Hi I've got an old amplifier (Pioneer SA-2001), it's got 4 channels (65w/channel). On the back, it says that it supports 8 and 16 ohm speaker and that you need to see the manual for 4 ohm use. I looked up the manual online, but can't seem to find anything. For years, I've used 4, 4 ohm speakers...
  15. C

    [SOLVED] High power, small transformer?

    So the combined power of the transformers on the board is 300w, al their primaries are in parallel, connected to mains. And their secondaries go to separate smps's?
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