Flyback design problems – I am developing an open loop flyback converter. The image below is the result observed at 70v (Dc) Input. The waveform is of the voltage across drain to the source. I have used the diode-zener snubber but there is still some ringing. Read more
Why is the damping resistor in our Bootstrap high side FET drive blowing up? – When the bootstrap diode of this circuit was using a silicon carbide bootstrap diode, the circuit worked okay. Then that SiC diode went obsolete, so we changed to the US1M ultra fast bootstrap diode and ever since then, the damping resistor keeps blowing up. Read more
Synchronous buck converter without reverse current detection – Have you ever seen a sync buck controller that does not have the facility to detect overly high reverse current flow in the synchronous FET? Read more
Transformer feedback winding – I’m building a sinewave inverter and I’m using a low-frequency transformer at its output. As I need an isolated feedback signal to control the output voltage, I was wondering if I could make an extra winding (few turns) to get a proportional voltage. Will it be proportional enough with the main secondary voltage (230V)? If the main load (output current) is changing (thus the main voltage will change too), will the feedback voltage closely follow the main voltage? Read more
Connecting two TRIACs with each other to common load – I am trying to connect two TRIACs to control common load as an incandescent lamp. I just want to switch it ON/OFF no dimming. I also tried connecting TRIAC like normal two switch connections but it damaged one TRIAC (it shorted and is always ON without gate) so how can I connect two TRIACs to control common load safely? Read more
Designing an H-bridge – I need to switch 230v dc supply from the capacitor bank to load in a clockwise and anti-clockwise direction (when the q1 and q3 igbts are ON the load should get +230v and when the q2 and q4 gbts are ON the load should get -230v from the capacitor bank). The IGBT I am going to use is G160N60. I want to know which driver is suitable for performing the above-mentioned operation. Read more
1.2V AAA to 12V 50mA converter – I am looking for a simple way (joule thief?) to convert 1.2v AAA to 12V 50mA. It has to be done with discrete components. Read more
Explanation for high power switching – I need an explanation for the switching supply circuit below. What is the topology used in this design? What is the purpose of D7 and D7′? Read more
TIG welder, inverter gate driver – I’ve started to analyze an inverter with an H-bridge composed of three paralleled n-channel MOSFETs (23N50E – each with a 68ohm gate resistor) per branch. The output of the H-bridge goes to three power transformers (via 3 4,7uF capacitors). The chip controlling the bridge (via an isolation transformer) is a KA3525A; the calculated switching frequency is 115khz (c=1nF, R=6.2k). The first thing that I notice is bad oscillation on the high side (why is present on the high side but not on the low side? Error introduced by oscilloscope?). The second thing is the little ringing is also on the low side. Finally, the gate is driven at much less than the 10v recommendation for complete gate closing. Read more
New and adequate topology for off grid battery inverters – off grid inverters (convert 12,24 or 48V DC to 220V AC) are definitely not new stuff. Our company is starting a project to develop an off grid inverter 24Vdc/220Vac 2kW. I would like to make some improvements on this inverter. It needs to be isolated, high efficiency, input voltage 20V to 28V, DC bus 370V, AC voltage 220V 60Hz. Do you think a single LLC DC/DC converter would be a good choice for this power? Read more