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IGBT circuit problems – I have some doubts on a result I’ve obtained. I’m using a circuit, as shown in the attached picture, to drive one IGBT of a module.

The waveforms shown are the voltage at the Load (yellow) and the current at the load (blue).

The load is a 28Ω resistor. Since the load is a resistor I was expecting the current to follow the voltage. Instead, it appears to have some delay (as if there was some inductance?) Can it be that my drive circuit is not performing as it should? Or the problem may be with the load? Any ideas or suggestions on how to improve the drive circuit? circuit? Read more

Preamplifier circuit design – Normally, when I build preamplifiers I would use it to control bass and treble, but now I would like a preamplifier that doesn’t cut any frequencies. All it would do is increase and decrease volume. Does anyone have a schematic of a good working version I could try? Read more

Designing a 60Ah lithium ion battery charger – Having an AC source of 220V, 50Hz, I intend to design a charger for a 48V, 60Ah Li-ion battery. I want to evaluate design cost with and without a transformer. Any input? Read more

100A AC current measurement – Yes, it’s an easy job to do with a CT and shunt resistor. But if I use an ACS sensor (hall effect current sensor) instead of a shunt resistor, will it be a wise decision? Will it be enough to measure up to 100A AC current? I’m using 100A:5A CT and a shunt resistor to the ADC of the microcontroller. Read more

Trying to find a replacement sensor – I am trying to rectify an issue on a machine. The sensors use reflectors and water spills on them all the time. The sensors are used for counting so at some point or the other when water is on the sensor I have to be standing around to watch the sensor and quickly wipe it off for it to count, or use my finger to pass the sensor so that it counts and doesn’t mess up the sequence of the operation. What I wanted to know is if it’s possible to replace the sensors with some that don’t use reflectors and would also ip67 certified. Read more

Ripple factor calculation problem – I am trying to calculate the correct values for a capacitor for a PSU I am going to simulate and I am having difficulty finding a reasonable value. Here are the specs I am working from and what I have tried so far:
-A 230 V smoothed [but unregulated] power supply is required to meet the following specification:
-Output voltage 12 V
-Output current 2 A
-ripple factor < 0.024 I have assumed this to be a percentage and that is probably where I am going wrong. Read more

DC-DC step-up converter efficiency – I have designed a simple, low power boost converter – Vin 1.8V vout 2v fsw=2M. How can I calculate efficiency with error tolerance? Read more

Ground on tube filaments or floating? – In this transmitter, two 220V to 6V transformers are used back-to-back to feed the 12AU7 filaments on parallel mode (6.3v) and also high voltage for its anodes. Should I ground (connect to chassis ground) one end of the 6V side of the transformers (i.e. the pin9 of the 12AU7) or shall I leave it floating (balanced)? Which is the best way to do it? Read more

Building a high power, high voltage (565V) DC power supply – I need to build a fixed-voltage DC power supply to emulate a large lithium-ion battery pack in order to drive an inverter as part of an evaluation test bed. I would like to rectify 400V 3-phase power and use this to make a fixed 565V DC power supply. I would appreciate any guidance on this. Is it as straightforward as implementing a 3-phase full wave rectifier circuit and then put sufficient capacitance on the output to meet my target ripple voltage? Read more

How to amplify small signal to high voltage – I’d like to generate the transient in power line system from D/A as shown in the image below.

There are 2 points that I want to know including.
1. How to amplifying the small signal from D/A to a very high voltage of  220V?
2. How can I accomplish the rise/fall time of such level (10u Sec at more than 500V)?
This signal is just a voltage-based supply to power analyzer. It will not drive to actual load anymore so the current can be very small. Read more