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Showing posts from February, 2013

N-Channel MOSFET High-Side Drive: When, Why and How?

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I had previously shown how to drive N-channel MOSFETs in low-side configuration. You can find the tutorial here: http://tahmidmc.blogspot.com/2012/12/low-side-mosfet-drive-circuits-and_23.html I’ve been requested to write a tutorial/article regarding high-side MOSFET drive. So, here I’ll talk about N-channel MOSFET high-side drive. Let’s first look at the common low side configuration.  Fig. 1 - N-channel MOSFET configured as low-side switch Now let’s look at a MOSFET configured as a high-side switch. Fig. 2 - N-channel MOSFET configured as high-side switch You can quite easily see the difference between the high-side configuration and the low-side configuration. In the low-side configuration, the load is connected between the drain and +V, while the source is connected to ground. Thus, the gate drive is referenced to ground. So by applying a voltage of >7V (for Power MOSFETs) or >4V (for Logic Level MOSFETs), the MOSFET can be fully turned on. Now let’s talk about the high-side

Ferrite Transformer Turns Calculation for Offline SMPS Half-Bridge Converter

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On different forums, I often find people asking for help in calculating the required turns for a ferrite transformer they are going to use in offline SMPS half-bridge converter s . The half-bridge topology is very popular for offline converters in the power range 100W to 500W, sometimes goin g up to even 1000W. In an offline SMPS half-bridge converter, the line voltage is rectified and filtered and is then converted to high frequency with 2 MOSFETs – one in high-side configuration and the other in low-side configuration. This high frequency high voltage AC is fed to the ferrite transformer to step down the voltage to low voltage high frequency AC which is then rectified to DC and filtered to provide clean DC output. A vital thing to remember is that in a half-bridge converter, the 2 MOSFETs work along with 2 capacitors to create the high voltage high frequency AC. The configuration of the capacitors, MOSFETs and transformer causes the transformer to be supplied half the voltage of the

Sine Wave Generation with "Fast PWM Mode" of AVR - using ATmega16

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I had previously shown how to generate sinusoidal pulse width modulation (SPWM) signals using the ECCP module in a PIC for generating a sine wave output for use in DC-AC inverter. I have had requests from people asking how to generate the same SPWM signals with other microcontrollers that don't have the ECCP module, such as the super popular PIC16F877A. And so I had written another article where I showed how to generate sine wave using SPWM with the CCP module of a PIC. This concept, as I had mentioned in that tutorial, can be extended to use for any microcontroller that has a PWM module. And so, I’ve decided to demonstrate how to generate sine wave using SPWM with an Atmel AVR microcontroller. The microcontroller I’ve chosen is the ATMEGA16. However, the concept can be used on any AVR that has a PWM module. The output sine wave is to have a frequency of 50Hz. I have chosen to use a switching frequency of 16kHz for SPWM. So, here I talk about how to generate sine wave using sinusoi

Sine Wave Generation without ECCP - Using single CCP Module of PIC16F877A

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I had previously shown how to generate sinusoidal pulse width modulation (SPWM) signals using the ECCP module in a PIC for generating a sine wave output for use in DC-AC inverter. I have had requests from people asking how to generate the same SPWM signals with other microcontrollers that don't have the ECCP module, such as the super popular PIC16F877A. So, here I talk about how to generate the same SPWM signals using just one CCP module as can be commonly found on so many microcontrollers. This allows much greater flexibility in microcontroller selection. You should go through the other articles related to generating SPWM with the ECCP module (if you haven't already gone through them, that is) to get an idea of what I'm talking about regarding sine wave generation with the ECCP module and about sine wave generation in general, really: Generation and Implementation of Sine Wave Table Smart Sine - Software to generate sine table Generation of sine wave using SPWM i