Yeah, I’m only applying PWM to the lowside FETs, the highside FETs are not modulated so the deadtime og dead-band delay is when the motor should change direction and this can’t be what happens here. Articles Top Articles Search resources. It might be difficult to control the power up and power down phases so you might want to see if your application can tolerate those 0. The body diode is in the wrong direction to clamp the motor voltage. Usually the power supply has enough capacitance to absorb the spike. I have had the circuit working just fine and my code seems to work like it should, I could run the motor at different duty cycles and different frequencies. Deadtime, is that the time between changing motor direction?
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In practice, with the current levels you are working with, it may be better if an external diode conducts that current. When building custom H bridges I always add some logic to prevent such situations happening i.
This protection mechanism is best implemented at the driver IC-Mosfet’s gate interface. I haven’t tried anything yet.
A fuse isnt a bad idea but sometimes they are not fast enough. Also add some clamp diodes while you are at it to prevent overvoltage spikes when the FETs turn off.
TSM CS, power MOSFETs – elpro Elektronik
A quick scan on the TC datasheetdoes not show that feature. You also might want to kill the drives for all fer transistors before you actually power down the PIC and the driver chips.
You can always “deadbug” a resistor across G-S. It seems to me that k is fine, the gates should discharge real fast when power is removed with k pulldown and about pF MOSFET input capacitance. In other words, is the time in which both Mosfets are completely off between transitions. Media New media New comments Search media. If they have a little internal resistance though that helps too. I even wait to the end of a duty cycle before enabling the output drivers.
TSM 4424 CS
It is worthwhile to investigate. Small motor circuits usually can get away with this.
I follow your explanation, this SHOULDN’T matter, but one thing I’ve learned 4244 painful experience is that one should remove first additional uncertainties from 44424 misbehaving circuit. Deadtime is the very short period one must have between the time a Mosfet is turned off and the time the opposite Mosfet is turned on. Thread starter Futterama Start date Feb 6, Electro Tech is an online community with overmembers who enjoy talking about and building electronic circuits, projects tet gadgets.
My advise to you But these seem pretty fast. You can then look across each resistor with a scope to see if there are any large spikes which would indicate that the bridge is not being switched properly.
Yeah, I’m only applying PWM to the lowside FETs, the highside FETs are not modulated so the deadtime og dead-band delay is when the motor should change direction and this can’t be what happens here.
I was running the unloaded motor at a frequency and would just change it in my code, so I disconnected the circuit from Vin, did the quick change in code, recompiled, reprogrammed the PIC and connected the Vin again, this took around seconds. I am suspecting the high side and low side FET’s turned on at the same time, in either leg of the H bridge or both resulting in pretty much a direct short across the rail. Any idea what went wrong?
In the end, it will be far cheaper and easier than replacing transistors and ICs. The body diode is in the wrong direction to clamp the motor voltage.
Futterama Member Feb 6, Hi, So then you are keeping one upper transistor turned on all the time and the other upper off, and turning only one of the lower transistors on and off? The body diode will clamp it.
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But fer of it this way, if you have a 12v supply voltage and 1 ohm resistor the maximum current would be 12 amps.