Top power electronics threads on EDAboard.com – July

(editor’s note: Intrigued by these power electronics problems? Have a question or optional solution? Then click the “Read more” link and follow the conversation on EDAboard.com or log in to EDAboard and participate in the forum thread.)

12 V DC to 115 V AC sine wave inverter – I am making a 12 V DC to 115 V AC sine wave inverter with the circuit below. But I don’t know how much power it can deliver. Can anyone help me with it and please suggest the components if I need to increase the output power? Read more

Switching problem in Triac – Triac of 3-quadrant does not operate in 4-quadrant but when we trigger the Triac with a silicon-controlled rectifier the gate of the Triac is always triggered with a positive supply.
Since 3-quadrant Triac doesn’t work in 4-quadrant, then the Triac only switch half of the AC sine wave. But I am seeing that the Triac is switching both the halves of the AC sine wave. Why? Read more

CUK PFC vs boost PFC – Boost PFC topology and its variants are widely used topologies in electric vehicle battery chargers. Does a CUK PFC have any advantages over BOOST PFCs as far as EMI/EMC is concerned? Read more

Limiting AC current – I am designing a 230V dimmer using a 12A output Triac which I control via aCPUu (through optocoupler etc). Is there any way to limit the output current to some 4A (max load about 900W)? Using a fuse before the load would just blow the fuse in case the load needs more current, so it is not an option. The same is for the output of an AC relay. The capacity of the relay output contact is 250V/10A. I would like to limit this to 7A (about 1600W or so). Read more

Discontinuous flyback transformer switching – I am using a discontinuous flyback transformer with a current rating of 8A. The frequency is 100 kHz with 60 percent on and 40 percent duty cycle. I am using FOD3184 optocoupler to drive the IGBT which supports upto 150 kHz. using this transformer, i have to charge 25uf/1100v capacitor upto 950v. While connecting the capacitor, it will charge up to 100v and but didn’t charge after that. I want to charge the capacitor every 1 Sec up to 950. Can anyone please give me a solution to the problem? Read more

Assuring stability of SMPS power module – We are trying to calculate the feedback loop Bode plots for a 48Vin to 48Vout, 3A converter using a PRM48 SMPS module. As such, we wish to calculate the gain and phase margin of this converter so that we can check it for stability. The details of the power stage inside the PRM48 module are not given in the datasheet, so we need them to provide the small signal power stage and modulator transfer functions in order for us to calculate the “open loop small signal transfer function”. We can then add in the external output capacitance that we add externally, and get the overall “open loop small signal transfer function”. However, the PRM48’ datasheet only provides the “Closed Loop output impedance” of the PRM48’ module. Help? Read more

Shoddy quality control? – This specific Chinese-supplied power adapter had much more output ripple than the rest of the batch. On closer inspection, the series inductor in the 2nd-stage ripple filter was shorted out. On the rest, this was not shorted. It makes one wonder how this slipped through? It is almost like a reject PCB made its way into the production line. The ripple level returned to normal when the track section was removed. Read more

DC-DC buck converter with hysteretic comparator loop design – I am designing a DC-DC buck converter. The circuit works perfectly when I use a vpulse in cadence to control the switching mechanism but I want to replace it with hysteretic comparator to be more stable and all these advantages. The main issues is that I cannot control the hysteretic window since everything is dynamically changing. Read more

Using DCM mode of DC-DC converters – Can anybody tell me why and when we use the DCM mode of DC DC converters? Specifically a buck-boost converter? Has it got anything to do with low power and low current applications? Most of the converters I have encountered in low power applications like energy harvesting use converters in DCM mode. I was wondering why? Read more

MOSFET in series – I want to make switch circuit to drive a 1800 voltage load. For that, I am using a 500V MOSFET. For making above 1800 volt, do I  connect 4 MOSFETs in a series to divide the voltage across the MOSFETs for 1800V? Is my demo circuit below correct for a series? Read more