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  1. R

    MOSFET Gate drive rise time with TC4428 driver

    Hi, I have a TC4428 driving a IXFH12N50F MOSFET. Supply is 12V DC. I expected to get a pretty good rise time from this, but it seems to be at almost 300ns. If I disconnect the driver from the gate and just measure the output of the IC, it still shows around 300ns. Looking at the data sheet, I...
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    High voltage power supply - need help

    I agree 2n3055's are no good. They were used years ago for this sort of thing because there was not much choice. Modern IGBT's or MOSFET's are much better. Check this one out.. http://www.rmcybernetics.com/projects/DIY_Devices/homemade_pulse_controller.htm
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    Understanding Safe Operating Area

    Oh good! I couldn't understand how the physics of what I thought I was reading could work! Thanks for clearing that up  ;D
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    Understanding Safe Operating Area

    Hi, I just want to check if I am understanding the SOA graphs correctly on a datasheet.. The STP30NF10 MOSFET is rated for 100V and 35A. http://www.datasheetcatalog.org/datasheet/stmicroelectronics/7817.pdf The SOA graph shows that the actual current it can pass varies with Vds. Now the graph...
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    Trigger an SCR to switch a negative voltage

    Yes, that is what I thought, and that is what the wiki says. I was hoping Lyker would explain how he thinks that a resistor can change this as he seems quite adamant that it can be done.
  6. R

    Trigger an SCR to switch a negative voltage

    Specifically the part saying "...the holding current specified by the manufacturer." This seems to contradict the idea that a resistor could change the holding current.
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    50V, 50A H-Bridge IC needed

    Ok, I reduced R2 and R4 to 4k7 as it seemed the gate voltage needed to be about -11V to have it fully on. I've also got zeners in parallel for when the voltage input gets higher. This seems to work pretty well!
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    Trigger an SCR to switch a negative voltage

    Lyker Says: How would I calculate this? The short circuit current from the 1kV source will be 270mA, so how can I use a resistor to make the holding current say 300mA? I'm a bit confused by this idea, I also thought it was not possible to do it like this. Here'a a quote from Wikipedia (yes I...
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    50V, 50A H-Bridge IC needed

    I just measured Vgs during the pulse to be about -5.8 V (Vth is -4V max on the datasheet). I will reduce those resistor values slightly (R2, R4) to pull the gates a bit lower.
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    50V, 50A H-Bridge IC needed

    It makes no difference unfortunately. I've even tried just pulsing bridgeA and leaving the other off. The high side MOSFET still gets hot quickly. For example using a 1R resistive load, 24V input (drops to 22V)  from an SLA. Pulsing to give avearge current of about 9A. After 10 secs, low side...
  11. R

    50V, 50A H-Bridge IC needed

    The battery voltage drops to 22 when I connect the coil directly, so this should be fine. I replaced the MOSFETs, and I've noticed that the circuit draws some current even when no load is connected. If I put the 4k7 resistors across the zeners, it stops this happening. Could the values of...
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    50V, 50A H-Bridge IC needed

    oh yes, sorry, I never worked with p-types before. I made the changes and it did seem to work better. When I switched to the 24V SLA though, it melted again. It did seem to take about half a second this time rather than being instant as before. The heat sink is pretty big so it can't be that...
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    50V, 50A H-Bridge IC needed

    I see, so those zeners being in the wrong place would be why the p-types were not switching as I expected. I had the other excess zeners like that just as some overkill really. I can see they are not needed, but there's no harm in leaving them there is there (they are already soldered to my...
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    50V, 50A H-Bridge IC needed

    Yes, that makes sense, they have twice the resistance (0.06 vs the 0.033 of the n types). I'm using IRF5210PBF and STP40NF10L. With the current limited to 5A, I can turn up the voltage without it blowing, but I do notice that if I feel the case of the p-types, they are very hot within seconds...
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    50V, 50A H-Bridge IC needed

    Ok, I melted it! (not so suprising :-[) Wen I tested with 18V, it was simply a pair of 9V PP3 batteries in series. The test load was a little solenoid with a resistance of 54 ohms. When I replaced the 18V with a 24V SLA battery, the MOSFETs (rated for 40A) blew immediatley. I had a 30A car...
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    Trigger an SCR to switch a negative voltage

    Thanks everyone. I'll probably end up switching off the charging source prior to the discharge then.
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    Solar battery charger question

    Not necessarily. All it means is that it is using PWM as part of the charging process rather than a constant DC. There still may (or not) be some voltage conversion / regulation involved.
  18. R

    Trigger an SCR to switch a negative voltage

    Hi, Just wondering about how to trigger an SCR for discharging a negatively charged capacitor into a coil. I assume the gate must be set at some voltage relative to the cathode voltage. If this is the case, the cathode being at up to -1kV relative to ground would need a transformer right? Is...
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    50V, 50A H-Bridge IC needed

    Great, thanks. I tested with 18V input and its working fine  :)
  20. R

    50V, 50A H-Bridge IC needed

    Hi there, I have another question about the diagram posted by Hero999. On the gates for the high side transistors, there is a pair of resistors (R1, R2). When input A goes high, this should activate Q1 and pull down the gate voltage of Q5. My question is, How did you choose those resistor...
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