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101 Threads found on Mosfet Turn Off
Hello I am working on 3 phase motor control by V/F control. my circuit consist microcontroller > IR2110> IRF640. Pwm freqency is 1KHZ Design is non isolated my problem that while mosfet switch on and switch off it create posivite and negative spikes upto +/- 25volts resultant +5v and +15 for microcontroller and ir2110 contant spikes or trans
Hi, No speed control. Just ON and off: * GND of arduino and GND of supply and Q1_GND need to be connected. * 9V, 3W means about 330mA. But expect a much higher starting current. Let´s say 1A. (if you use a BJT with B of 25, then you need a base current of about 40mA. I don´t recommend this. ) * Therefore I´d use a mosfet. rated for 20V, 1A, R-d
Hi, I am experimenting with a half bridge built arount the IR2110. When trying to determine the turn-on/turn-off times by using an oscilloscope and changing the values of the gate resistor, I found a weird problem: As I reduce the gate resitor value I observe that the turn-on time decreases, as expected. (...)
Hai, Can Anyone please help me!! I am designing a 4V lead acid battery charger using a PIC MCU. the charger section is ok what my problem is i have used a IRFZ44 mosfet to turn the LED load on and off. I want turn off the load when the battery is discharged to ~3V. the circuit diagram is (...)
R1 connects the gate to the source causing the mosfet to be turned off then the voltage at Node 1 is 0V.
Hi, your document is the "Demo Manual". But if you read the LT3752 datasheet you will find sections for mosfet seletion. Klaus
Hi, I was wondering whether switches in an inverter get rid of ringing completely by utilizing soft switching techniques. For instance suppose I have a full-bridge series-loaded resonant converter using mosfet switches . Is it possible to eliminate ringing at the turn on and turn off instant by using zero voltage (...)
Hi, I was wondering whether switches in an inverter get rid of ringing completely by utilizing soft switching techniques. For instance suppose I have a full-bridge series-loaded resonant converter using mosfet switches . Is it possible to eliminate ringing at the turn on and turn off instant by using zero voltage (...)
I hoped that the Resistor across gate and source can discharge the capacitance but it is not happening. I checked at the source point of the high side mosfet Q1 which turns off only when its source is grounded. I think you are misinterpreting the waveforms in post #1. The mosfet does turn (...)
123367 I have searched and cant seem to find the solution, This design has always worked fine for low power outputs, but this seems to be destroying mosfets on higher loads I am using it to light a 55w halogen, if you turn it off and on slowly, then this is fine, but flash it a few times and the mosfet goes short a
can i use the following mosfet circuit to turn the Anode voltage on or off thus enabling or disabling the backlit ? 122664
Firstly. A certain impact of miller effect is normal operation. What's your specific problem with it? Secondly. We need to see the actual gate driver circuit to understand how far "driver ouput" can be different from "mosfet gate" voltage. Ringing suggests existence of wiring inductance, which can be generally considered "avoidable". But may be
ideal result is when i did not put in 24v to my CW or ACW U1 & U2: Pin 2 (IN) = 0v Pin 5 (LO) = 0V Pin 7 (HO) = 0V which means none of my mosfet is turn on. But the Ideal result is when IN is 0(CW or ACW is 0V) then the LO is 15V and HO is 0V. (with no off signal) The HO will give output only after turning ON and (...)
Is this a trick question? Am I missing something? If you have a common-emitter PNP transistor, pulling the base to ground through a resistor will turn it on. Or use a P-channel mosfet.
The main reason BJTs are considered slower is as Dick stated. The saturation delay for the BJT to turn off can be very long. But if you prevent the BJT from saturating (such as connecting a Schottky diode from base to collector as is used in Schottky TTL logic circuits) then you can basically eliminate the saturation delay and BJT speeds can be c
It's not clear what the gate resistor is, it looks like 1.1K to me, but I'm not sure; in fact, I can't really read anything on that schematic. That 1.1K would be inexplicably large, but shouldn't cause a static problem. It's also not clear what "1 Volt at low state" means. You mean when the mosfet is on? (Low). Or when the Gate voltage is low
No, you will have to use another mosfet/npn transistor.
You can use a mosfet transistor to control the LEDs from an external 12V source (such as a wall-wart). Use a logic-level type N-mosfet as a low-side switch (12V to LEDs to mosfet drain with mosfet source to common ). The mosfet will turn on when the gate is at 5V and (...)
At least this problems: - RCD not working (wrong D4 polarity) - very slow mosfet turn-off due to bad gate driver circuit. Should use push-pull transistor buffer. It's also unclear if the transformer has right winding polarity for flyback operation.
Hi ArticCynda, R23 is for turn on and off Q1, so i turn on and off the switch. This is controlled buy a mcu. But if i omit R21 the VGS of the Q6 and Q7 wil be like 30V. the limit for the mosfet is +-20 VDC. Hi SunnySkyguy, So what do you propose?
greetings, To evaluate a mosfet driver IC, I have implemented shown circuit. The upper switch work well. it means when it switch ON, upper lamp gets ON and the other lamp get off. but when down switch is fired, the down lamp does not get off, however the upper lamp get ON, even when I provide continuous high gate signal the gate resistor (...)
There are IC's made to regulate switched coil converters. The control pin sends pulses, which turn the mosfet on and off. The IC has sense wires, to detect output voltage, detect coil current, have a reference voltage applied, etc. I don't know whether it can be done just using control techniques or the topology should be changed anyway.[
I don't have LSpice loaded here at the moment but I see you are using STD5NM60 , N-channel 650 V@Tjmax, 0.9 Ω, 8 A MDmesh? Power mosfet The key factor is latency from input and output capacitance with driving gate & source resistance* capacitance in each case for turn off delay. 1. Coss eq. is defined as a constant equivalent (...)
Page 7 (LHS) of the following (below) article is totally wrong, do you agree? It says that regarding active clamp forward converters, ?With sufficiently fast gate drive, the turn off of Q1 can be virtually lossless.? (Q1 being the main power mosfet). This is impossible, current cannot suddenly go to zero in Q1 and cannot (...)
OVP is to limit the output voltage. Use a P mosfet switch to pass the input to output with no voltage drop. Then use a PNP transistor to turn off the switch. It can be regulated using a comparator with a 2.5V reference and divider on the output. the open collector driver can now drive the PNP base for a precision 40V series pass switch with (...)
Guys, I need some help with my circuit which I have attached circuit is intended to be a very cheap solution of a transmitter-receiver channel - the receiver is comprised of R1 and D1 and the rest components are the transmitter. The problem is with the gate voltag
You would be better off, I suspect, using a mosfet as a switch as the voltage drop across a transistor would drop the voltage below GPS voltage requirement. I am sure you can find many mosfet switch circuits on the internet.
The body diode "can" act as a freewheeling diode if the mosfets are in the correct setup. For instance an H-bridge or half bridge arrangement. When driving an inductive load like a motor the "bottom" fets diode will circulate the current until the fet turns on. In your case the body diode is doing nothing :0) Neddie
Hi, I have attached 2 application notes that are available on the internet for free. In application note 1, refer to figure 9 and 10 on page number 13. -> In the dc-dc step down converter, when the high side (control) mosfet is turned off, why do we see a large spike and some oscillations if the gate-drain capacitance is low ?? ->
That's the complicated way. Use the transistor a Bradthe Rad suggests and use a PWM output from the PIC but forget the AND gate, just enable or disable the PWM output to turn it on and off. It will work better if you can use a logic level mosfet instead of a bipolar transistor. I control lighting using PWM from a PIC through a 2SK2989 (...)
Can I use an RF mosfet in switching application? I need to turn on and off about 200mA current at a rate of 100MHz. Can I use an RF mosfet for this? Those FETs that are marketed as switching FETs have turn on and turn off times in the range of 20ns or much more. To be (...)
You can use some temperature sensor ICs with I2C interface which can be placed on the monitoring region & you can turn on/off your relay/mosfet according to the temperature reading. You can use a fan also for lowering the temperature fast.
Another thing about mosfet parameters: The "threshold voltage" is the gate-source voltage where the mosfet is beginning to turn on with a very low drain-source current or when it is almost turned off. The threshold voltage spec is rarely used in a circuit design. The threshold voltage for a (...)
How to make a simple switch to turn off a led during daylight using only one transistor, jfet or mosfet, and a light dependent resistor ? No other components, besides the white led and a 3.5V cell ? Is there a way to turn on at dusk, off at dawn with that minimum of components ? Or, does a reverse (...)
If output depends only on transformer turns ratio, it means there are no feedback regulations in your simulation circuit. Primary wiring current ramps up until reaches comparator's (current sense) threshold causing mosfet transistor to turn off. Then voltage on the secondary wiring goes as high as turn (...)
Normally turning a motor off rapidly is not a concern, but if you need rapid turn off, then a resistor in series with the diode clamp or a zener clamp will more rapidly dissipate the inductive and rotational energy in the motor. If you have only the diode then most of the energy is dissipated in the motor itself, which (...)
I'm try to run mosfet with high frequency..30 khz..10 duty cycle. i got turn off switching in mickro second but when i read data sheet is about nano second. Is it normal?, or is anybody have idea to reduce this turn off switching90037
I'm try to run mosfet with high frequency..30 khz..10 duty cycle. i got turn off switching in mickro second but when i read data sheet is about nano second. Is it normal?, or is anybody have idea to reduce this turn off switching90037
1. An N-mosfet has its gate referenced to the source terminal. In order to turn on, the gate voltage needs to be higher than the source terminal. The source terminal should have a definite path to ground, for proper operation. However your upper two mosfets appear not to have this at times when the lower two mosfets have (...)
For the switching device you have some choices. You can use: Triac SCRs Relay Solid State Relay mosfet (with some supporting circuitry to allow switching of AC) IGBT (with some supporting circuitry to allow switching of AC) Your method of drive will depend on the selected device. For the controlling you will need
Both BJTs and mosfets are much faster then the multiplexing frequency:
I used this setup with the sources coupled together, however this was a very high power application (several channels of 100+ Ampere's) and I used N-mosfets. The reason I chose this setup was lower dissipation then with a P-mosfet since they have a higher RDSon. I think it all depends on what power You want to switch, is it mA's or 100's of Amper
You can think about these methods: You could sense the output current and turn off the mosfet if the current is too high. You may also use a linear current limiter at the output (since output power is pretty low). Also, as current flow increases, battery voltage decreases (due to internal resistance). So, maybe you could use the (...)
You can use the same mosfet for high side or low side drivers. Handling the Vgs signal to turn on/off will be different. In some applications using a P channel for high side and a N channel for low side simplifies the driving of the gates. So mosfets are not specific for an application or the other.
I think the 150Hz refers to the maximum switching speed, not the 600V frequency. The 600V is DC according to the diagram, am I correct? If so, a triac won't turn off. How about an IGBT? For instance, the NGTB15N120FL from OnSemi, or a power mosfet, e.g. the NDD03N80Z from OnSemi. I like OnSemi! Do you really need to switch the negative (...)
The N-channel mosfet high-side drive is more difficult. The N-channel mosfet needs about 8V VGS to fully turn on. If the mosfet is on, the voltage at source would be 12V. However, with respect to ground, gate voltage would be about 12V. So, VGS (voltage at gate with respect to source) is 12-12=0. So, the (...)
Well he states his reasoning clearly once: During turn off at no-load or light-load condition, when the inductor current is negative, if both mosfets are turned off, this negative current can only find a way through the body diode of Qrect to the input dc source. In an isolated converter, this produces (...)
Well, first of all, you've got your half-bridge drawn wrong-the upper mosfet is upside down. I'm not quite sure how this all works with those caps driving the gate, but I'm suspicious about those 10K resistors. If you are counting on those to turn your devices off, you're in trouble. The mosfets have a huge input (...)
hello every one.. i got struck in a project where i need to turn on and off three motors depending on the operation using pic 16f877.. 1. 24v dc motor 2. 230v ac motor 3. 24v ac motor can any one please suggest me how to operate these motors with pic 16f877.. do i need any triac or mosfet or any other circuit to add in between motor (...)
Hi, I am working on a similar project: I have verified that using a isolated power supply for the gate drive circuit will turn the N channel mosfet on and off in a Buck circuit configuration with a 12 volt battery as a load. I configured the gate drive circuit with a 555 time and used a Schmitz

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