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Designing adjustable voltage SMPS – I am planning to make an adjustable voltage SMPS. How do I find the proper output inductor value? According to the textbook of “Switch-Mode Power Supplies Spice Simulations and Practical Designs,” output inductor value becomes about 2 mH for minimum output voltage which has been taken to about 0.1V. I don’t know whether this inductor value is ridiculous. And do I need to do feedback and other calculations according to the minimum and maximum output voltages? Read more

Building a class E power amplifier in driving wireless power coil – I am new to power amplifiers and am building a class E PA to drive a wireless power coil. I can get the sinusoidal waveform at the coil, but it is still not functional. Below is my schematic. Read more

Measuring the energy used to recharge a μF electrolytic capacitor – We are trying to measure the energy delivered to the 820μF capacitor connected to the output of our offline flyback SMPS when it charges this capacitor back up to 300V from 62V. The problem is that this figure did not agree with the calculation which is done by simply subtracting the energy in the capacitor at 62V (0.5*C*62^2) from the energy in the capacitor at 300V (0.5*C*300^2). Read more

Design for a pure sinewave inverter – What do you think is the most straightforward approach to designing a pure sinewave inverter to convert 12VDC into 230VAC 50Hz is? Read more

Battery capacity tester – I am trying to design a relatively simple capacity tester for a 12 V battery. I want to put the battery under a load and measure the time it takes to drop the voltage to 10-10.5 V. I can’t work out the Zener voltage or resistor values to get it to shut off at the target voltage. Read more

Switching power supply for TOP246 – I have an interesting situation with a failing diode D1 in the snubber of a switching power supply. According to the diode specification and the design of the snubber, I can’t imagine what could possibly damage the diode. Read more

Leakage issue in forward converter – I have a situation where I need to use a forward converter. I have never previously worked with forward converters. I am feeling a bit hesitant about using it due to the leakage between the primary bi-filar windings. Even with good coupling between the bifilar winding with a total of 1000μH, there should be at least 5μH of leakage between the bifilar windings itself (guessing). This is enough to spike down the MOSFET. I have chosen a 100V, 220mΩ MOSFET in an SOT23 package (IRLML0100TRPbF). Even with snubbers, I don’t see how the effect of a large leakage (5μH) can be suppressed. Read more

Power supply calculations – I made a basic linear AC/DC power supply and wanted to ask why my calculations, based on the Hammond Rectifier Relationships pdf, were way off reality. It’s a dual secondary: 2VA. 2 x 12V AC secondaries; 83mA AC per secondary. Read more

Seeking advice regarding structure of a DC/DC/PMW regulator – I am designing my own driver circuit for a personal vaporizer. It’s a device containing batteries, an LCD/OLED and a couple of buttons. The device’s function is to supply power to an atomizer to vaporize a liquid containing nicotine. I want to keep the device as small as possible but the max output power will be 100W, possibly 80W. And I have to decide whether to use a DC-DC buck-boost solution or a boost converter plus PWM. Does anyone know of any boost/buck-boost converter IC which uses external MOSFETs? Read more

MPPT design using LTspice – I am trying to design a buck converter for a PV panel. I know that I can purchase a commercial MPPT or even find a chip that offers MPPT. I am planning to build one using a microcontroller, temperature sensors, etc. for a project. I would like to simulate a basic boost converter with the model I have for my PV panel in LTspice. Are there any clever ways to implement MPPT in LTspice on a simple buck converter? Read more