3V – 5V high current 150A power supply – I have been asked to generate a 100A RMS precise sinusoidal current. It will have negligible burden/load. Luckily I’ve done something very similar in the past where I used a LEM sensor, a dsPIC33, and an inductive load and a current-controlled PWM inverter based on a PI controller. It worked and I could inject any required current (sine, square, ramp etc) of desired magnitude by providing it with the desired reference. So all I have to do is scale that system up for high current levels. Getting high current MOSFETs is no problem. Only thing I need now is about 150A of current. Where to get that? Read more
Determining SMPS transformer type and primary turns – I need help determining what type of transformer I have how many turns it would require on the primary. I was driving a transformer but after a while it gets hot and it should let more power through. All I know is that this transformer came from an older Philips TV set which had an SMPS power supply. Below is the schematic of my SMPS. Read more
Eliminating gate ringing of parallel MOSFETs – If I want to use parallel MOSFETs in a half bridge to increase output current, (I use IR2113 for gate drive), the MOSFETs blow up in few minutes after power is ON. I suspect gate ringing. If I use two separate gate drivers for each arm of half bridge, can I eliminate this fault ? Read more
High power motor control – I am working on a project for controlling an AC three phase asynchronous machine of 11KW. I want to use six MOSFETS and do it with SPWM. Could you please advise on the components and codes to use? Read more
Design of a LED driver circuit – I am using eight green LEDs in series for my project and I need a driver circuit with forward voltage of 3.1V and 20 mA. Is it ok to use this circuit? Read more
Earthing in SMPS for EMI noise reduction – This 3kw electric car charger is totally encased in a metal enclosure which is connected to earth ground. I assume multiple parts of the internal PCB are electrically connected at various points to this earthed enclosure. The reason for earthing is safety but it also is good for EMI noise reduction. We see how essential an earth connection is for EMI noise reduction. So how do European plugs manage to avoid this noise problem? They have no earth connection. The power supply would not be earthed and the noise will run wild? Read more
BTL class D filter design – I’m looking at designing a BTL filter for a class D type. The PWM signal will be around 300 KHz and the sinewave will be 2-20KHz at about 50V p-p with a185 Ω load. I need the filter to be pretty flat and cut off at about 25-30 KHz and I want as high attenuation as possible at 300 KHz. What is the best way with this design to achieve this with a high attenuation at 300 KHz. Would it be a case of higher order filter and, if so, how does it work with a BTL design? When designing the inductor how does having a PWM on one leg and a sinewave wave on the other effect the inductors saturation, do you only care about the lower frequency signal and the p-p voltage or is it more complex then that? Read more
PSU schematics – I need a simple 1A, 0-50V adjustable PSU for the lab. I have found this which looks ok for it’s simplicity. However, I wonder if a single regulator can do this, such as the LM317 which is used up to 30V. I see that the LM317 can go as high as 37V. Can you help me design a PSU with this one for 1V – 37V or so? I am not sure about the transformer and bridge/capacitor values so as not to exceed 40V (max input for LM317). Read more
Problem with power line disturbances – Is the last method for suppressing power line disturbances using a UPS? I used an isolated transformer and line filter in my design but when I turn on s single-phase motor manually, my board receives an interrupt. It’s surprising. because it happens even though I disconnect it from my device and I use a laptop USB port for its power supply. Read more
Coupling factor in LTspice – For a transformer in LTspice, can you confirm that the k factor (coupling factor) gives the leakage inductance by this formula….(1-k^2)*L(pri)? Also, that this leakage inductance value is that inductance value that you would measure if you shorted the secondary and measured the inductance at the primary terminals? Read more
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