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108 Threads found on Fet Switching
Most often the chosen frequency is not limited by the fet's own capability, but outcome tradeoffs like the switching losses you can stand, EMI, available external components and the BOM cost thereof. Often MOSfet selection is done to optimize the efficiency and cost, without regard to the ultimate cutoff frequency or the like. A rough (...)
The "problem" is that even if the fet turns off instantly, the rise time of VDS will be determined by its drain source capacitance (Coss) and the load current. If your load is just a 1K resistor, this will result in a fairly slow rise time of VDS. You need to increase the load current greatly to see the true switching times of the fet. (...)
i don't think that will make difference No big difference. But you should analyze the switching behavior (fet current and voltage) to be sure that the circuit doesn't involve additional switching losses, due to diode reverse recovery, slow switching caused by unsuitable gate signals or whatsoever.
Because dynamic current does flow through the gate to charge and discharge the gate capacitance when the MOSfet switches. So a low gate poly resistance will reduce the gate charge and discharge time, increasing the maximum operating switching speed of the transistor.
As Klaus says, Burst mode is often seen in pwm controllers which are controlling a power supply which has gone into light load?(often called ?low power burst mode?)?in light load, you don?t want to keep switching the fet on and off, as it results in too-large switching losses, so what you do instead , is you just have the controller pulsing (...)
when I am using the HCPL3120 for driving the high side (cascaded BUCk+Boost converter for high voltage around 600V) fet, there is dip in the gate drive supply voltage and negative current flowing through to gate drive supply during the switching period. please someone help me, thank you127638
there is a timer which switches the mosfet off after that time has elapsed. The drain pin looks at the voltage there and when it is low it turns the fet on again. The advantage is that you are always in DCM but not too deeply. Also you can know your average led current is peak/2, so you choose the right sense resistor, and you get th exact current
Have you ever seen a sync buck controller that does not have the facility to detect overly high reverse current flow in the synchronous fet? Yes. Many buck converters are just switching the low side transistor unconditionally, in other words implement forced CCM operation. This involves higher losses at low output current but also
ZCS converter is like many DCM converters, where the fet current is zero at the point that the fet is switched on. ZVS , is like in the Quasi resonant flyback where you have ?valley detection?, so that you switch the fet on at the point where its voltage is zero and avoid Cds capacitive switching loss??however, its not (...)
I picked one igbt from mouser with 600 V voltage and 11 A current rating. The IGBT is optimized for 40 kHz and could be ok for SMPS but I don't know if it is better choice than mosfet. Saying this iGBT is "optimized for 40 kHz" somehow abridges the facts. I think you would better say it can be operated up to 40 kHz under circumstanc
Hello, In Full Bridge SMPS type converters, why do people use pulse transformers on the bottom fet drives as well as the hi side fet drives? I mean, presumably its so that the propagation delay of the switching signal is equal for both top and bottom fets, but isn?t this pointless? The 70ns or so delay is too short to be of any
What's the highest switching frequency that the method of page 12, figure 4 (datasheet below) can be used for? This is with reference to a full bridge LLC converter with vin = 400VDC. The actual signal to drive the fet drive ic is coupled up to the hi-side via a pulse transformer. 1EDI60N datasheet
any calculation of fet switching losses will be subject to considerable error. There are a huge number of factors involved. The following by Balogh though, summarises the process of calculation. As you can see from Balogh document, there is a turn-on switching loss associated with the gate voltage rising from Vth to Vgs(miller)?this (...)
what are the switching conditions for fetIn short words: The driver need to have enough peak current to quickly charge the gate capacitance, the supplied voltage to gate has to be higher than VTH.
Hi, ..and you can also use a Pchannel fet for highside switching, then you don`t need a charge pump. *** N-Ch fets are more common and easy to drive. There are logic level MOSfetS that can be directely driven by a 5V or even 3.3V logic output. But in cars you have a common "minus" system. All the chassis is connected to (...)
As you connect the secondary, can you confirm what waveform the mosfets produce at that moment? Is it narrow pulses (narrow duty cycle)? Or do they conduct continually so that they burn up?
..more than .. just a guess MARKING CODE LIST P(2) * , ** , *** , ****,_=date code,Lot No. etc. PM RTL035N03 ROHM - TUMT6 6 2.5V drive N-ch MOS fet for symbol : PM - - - Upda
It is common to use a control IC which is made to regulate a switched-coil converter. I suppose you will use one which works from a positive supply. Obtain an IC which specifically states it can create a buck-boost converter. Then it should be able to read feedback from the negative output voltage, one way or another. (Or else it is common to use
For the first look, this MP3 fet is used to preventing cut-off of a MP2 when the output is in low state. Yes, apparently a clamp circuit for the MN3/MP2 drain node to speed up comparator switching.
'afternoon all, I've been working on a two-independently-controllable-axes motorised platform for a local charity for the past while and I've run into some difficulties with my motor driver circuits. In a moment of stupidity, I decided it would be a good idea to reinvent a brushed motor driver rather than buy a convenient module, so I opted to