Power Electronics Top Talks in October 2019 on EDABoard.com

Peer-to-peer, engineer-to-engineer questions and answers from the EDABoard.com engineering community around power electronics. Click the “Read more” link and follow the entire conversation and maybe add your two cents by logging in to EDAboard.com

Buck converter vs. buck-boost converter – I need to design an induction cooktop circuit having 4kW output power. I have 1kW and lower power levels SMPS background, but I don’t have any experience in resonant converter topologies. As I have read from app notes, it is very similar to resonant converters except the transformer. In formulas, I see the transformer turns ratio and output voltage, but in this design, I don’t know what the output voltage is. I would like to ask whether I can apply the resonant converter formulas to the induction cooktop circuit design? Read more

Bridge diode thermal problem – I am talking about a basic bridge rectifier made of RS601m. Take a look at my circuit that has been used for 20V/5A AC application, the problem is a diode and caps temperature is rising to 52 and 45 degrees respectively. My senior said, ” add more two similar capacitors to reduce ripple,” then “heating can be minimized” Don’t you think its a wrong idea! Read more

Which transformers can pass approvals testing regarding isolation voltage testing? – Our contractor designed a 10W, 24Vout, offline flyback SMPS for 240VAC input. He had a split primary and a bias coil on the primary side, both wound with enameled copper wire. He also had a secondary of triple Insulated wire. He used an SMD transformer, which was EFD25 (Page 423 of the below Ferroxcube datasheet). This failed approvals testing involving testing at 3.5kV for 1 minute. Read more

400v power supply design – I need to design a power supply, which is having input as 400Vdc and input power of 7.4Kwatt. Now it will have 50V dc output voltage. How to calculate inrush current limiter resistor value and capacitor bank before conversion. Please help me by suggesting a way forward. Read more

Voltage spikes on the gate-source of upper H-bridge MOSFETs – I was testing an LLC converter I designed under high voltage (500V), and after a couple of tests under low power (100kHz, 300ns dead time), upper MOSFETs (SCT3160) of H-bridge got damaged. Both of the damaged MOSFETs had gate and source shorted. I replaced both MOSFETs with new ones and checked the drain source voltage with a differential probe and saw there was a voltage spike of 30V on each of the upper side MOSFETs. However, there were no visible spikes on the MOSFET gate of the lower bridge. Read more

Film capacitor failed in flyback SMPS at high temperature – We are using the ECW-FD2J185 (1.8uf, 630v) film capacitor in our offline flyback SMPS, 240vac input. It is for 24v, 10w output. We sent it off for extreme temperature testing, and it eventually failed with the TNY287 flyback controller showing a short from BP/M pin to Ground. The testing was done at 190VAC and 10W load. We are a little surprised that it failed. Read more

SMPS power supply of about 12VDC and 1A output – Please let me know that about SMPS power supply 12VDC@1A. I want to make it for the digital voltmeter I will make. I want to make a transformerless power supply. I googled and found attached here. But I want to learn it and make it by myself. Read more

Battery cutoff voltage vs. 0% battery voltage – I have a battery which has:
Maximum voltage: 4.35V cut-off discharge voltage: 3V. I want to know what is the voltage which my product should be in 0% battery. Is it 3V? Are we supposed to discharge until 3V or we should shut down the embedded system at higher voltage, e.g., 3.3V? What is the norm for battery-operated embedded systems? What do they do in mobile phone design? Read more

AC consumption in an adapter –  I have a DC device with input rating 12V–2A which means it consumes 12×2= 24 Watt DC. Does it consume the same amount of AC (by adapter) also while using AC to DC adapter? Read more

Induction cooktop circuit design –  I need to design an induction cooktop circuit having 4kW output power. I have 1kW and lower power levels SMPS background but I don’t have any experience in resonant converter topologies. As I have read from app notes, it is very similar to resonant converters except the transformer. In formulas, I see the transformer turns ratio and output voltage but in this design, I don’t know what the output voltage is. I would like to ask whether I can apply the resonant converter formulas to the induction cooktop circuit design? I am struggling applying formulas especially turns ratio and output voltage calculations. Read more