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AC DC full bridge power supply – I’m designing a variable output full bridge power supply and I found an interesting design from Microchip but its DC-DC. Could you please help me wth an AC input 230V and DC and 30V 5A as maximum output? Read more

LT3750 capacitor charger problem – I’m trying to design a 240V 6A capacitor charger system. I made calculations according to the LT3750 datasheet and then I constructed the circuit. The circuit has worked but is not reliable at the desired voltage. Read more

20A SMPS battery charger – I designed 20A charger using TL494 but the MOSFET is damaged once I connect the mains rectified DC volt. The IC is also damaged. Read more

PWM ON and OFF states – I was really confused when reading about the theory of H bridges. To rotate the motor at lower slower speeds the document says we use PWM signals. That point is understandable for me, but it says in PWM OFF states several combinations are possible. For example, H1 can be ON. I was assuming that PWM off means all switches are in OFF state. Read more

Paralleled IGBTS – When IGBTs are parallel we cannot discriminate failed IGBT measuring GS and DS voltages. I was wondering what is the best way to discriminate failed IGBTs in a parallel set? Read more

LYTSwitch-7 modifications for 100mA to 200mA – I am building a circuit by taking the application example from the LYTSwitch-7 from the Power Integrations.Now I want to make some changes:
When input voltage range:85-135VAC, the IC should provide me a constant current of 80mA

When input voltage range:150-210VAC, the IC should provide me a constant current of 160mA

How can it be accomplished? Read more

Implementing SMPS charger – I want to design charger with an SMPS transformer. I will use a TL494 for PWM and a MOSFET driver for the primary side of the transformer for a range 150 to 240 v AC. What is the correct feedback for an SMPS charger? Read more

PCB fails common mode emissions  – We have a 1W buck converter (bias supply) on our offline 150W LED driver PCB (which uses linear current regulators). It firs failed EMC due to having the buck’s switching node copper laid out all over the bottom PCB layer, where it was next to the earthed heatsink (common mode emissions). We have removed the switching node copper from the bottom layer. However, do you believe that we should shield the switching node copper (which is now only on the top layer) from the earthed heatsink by putting some “quiet node” copper underneath the switching node of the buck, in order to shield the switching node from the earthed heatsink on which the PCB sits? Read more

Looking for a semiconductor circuit breaker – In my current design I’m taking advantage of the over-current limit feature of an LM317 and using it as a fast acting short circuit protection device. This is a bad solution as the voltage drop across it is too big. I’m wondering if there are dedicated chips for this purpose? A simple two-pin device that cuts current flow if the current gets too big? I need it to act fast so a PTC or polyfuse is not going to work. Read more