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Resistor mounting conditions for full power rating at 70degC ambient? – For the PF2512FKF7W0R007L (7mΩ) 2512 SMT resistor, what is the mounting description (i.e. area of surrounding thermal copper pour) that corresponds to the rating of this resistor as being 100% full power (ie 1W) up to 70°C ambient? Read more
Fast(est) shoot-through protection – I want to design a shoot-through (and short-circuit) protection for a full-bridge MOSFET. Currently, I have an LEM current transducer on the positive rail (DC-link) and I’m reading its output every 100μs using an ADC (for power monitoring purpose only). I don’t think that polling interval is short enough to save the MOSFETs on a short-circuit/shoot-through condition. Is that delay (7μs) short enough to protect the power MOSFETS? Read more
Issues with instrumentation amplifier for current sensing – I am using an instrumentation amplifier circuit to measure current on my jig. The instrumentation amplifier has a Gain of 2.I am wondering if someone could help me to understand what exactly is going on here and why I am getting offset with No load at input. Read more
Active clamp voltage – I have a high-side active clamp forward design with 350V in, but I am seeing 760V on the switching node (very similar to setup as pic). Does the clamp capacitor control the amount of voltage seen at this point? Read more
Application of sine-wave – What is the application of a sine-wave oscillator? Read more
IR2153 + regulation and protection, modification, calculating the values – I modified this circuit
to this
and need help calculating the values for the protection and for the feedback because I tried the feedback and it outputs only 2V-3V instead 23V I want. I’m confused because there are a lot of power types – peak power, RMS power, average power, etc. I need an average 250W limit. Read more
Inductor current in the buck converter – Attached the table that’s confusing me. In the table below, it shows that increasing the duty cycle of a buck converter reduces the inductor current. Isn’t that wrong? Read more
Sub-harmonic oscillation at low duty cycle – I’m running an active clamp forward design (LT3752) with Vin 170-350V and Vout 24 @ 1.25A. For some reason at 200V input the system seems fine, but as soon as the Vin goes to 240V+, I seem to be getting some sub-harmonic oscillation (Gate goes to small and large pulses). I thought this normally happens at higher duty cycles (closer to 50%), but it seems to be happening at the lower duty cycle end. Any ideas or experience with why this is the case? Is it a case of trying higher slope compensation? Read more
MOSFET gate current calculation – I want to use a MOSFET for switching power supply. I want to know how much current gate will source/sink? I am getting the PWM from a microcontroller. Can I directly connect the MOSFET gate to the microcontroller or do I have to use a specific driver? Is there any formula to calculate gate current? Read more
DC motor control – is this schematic good? – Here is a schematic for DC motor control. Using this I can drive motor in both directions and also send short pulses to the motor, to move it only a little bit in the desired direction. Is this ok? Is there something I should change? Read more
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