White papers on UCD also mention that there are no patents on the bridge topology as it is a complex subject. I thought of an old fashioned approach that could sort things out Transformer output will do two things: 1.
Impedance matching 2. Isolation Unlike linear amplifiers, the output transformer can be small in Class-D topology. I am not an expert in power switching or magnetics and so would like to invite the members here to give an opinion. I hope that I have not missed anything obvious, if so, my apologies in advance.
One very obvious error in your thought. Class D is a rail to rail switching PWM amplifier. A transformer will only see the rail to rail frequency and level that doesn't vary. The PWM will not cause any difference in the flux of the core and therefore will not transform any audio frequency modulation. Find More Posts by Pafi. Class-D Bridge. I was too hasty in my thoughts and got carried away and missed these basics. Sorry and thanks!! Further, is it not possible to modulate a switching power supply PWM driver like sg, tl, etc.
There are many class D bridge amp IC's. Everything goes somewhere I was looking for a way to reduce the size of the output transformer for V line output application. But then that is not possible.
Theoretically I could eliminate it completely if I have a bridge amplifier operating on single supply of say Vdc. Originally Posted by bimbla.
BB code is On. Smilies are On. Forum Rules. All times are GMT. The time now is AM. Resources saved on this page: MySQL SparkyGSX: Thanks for taking the time to reply thoughtfully to what musta seemed like a newb question. Heh, you mention RL time constants and not having "even thought about"s… I've been making-use-of RC time-constants quite a bit recently, but somehow the idea of an RL time-constant had completely slipped my mind, even in thinking about this PWM-Frequency question.
Thanks for jogging my memory. Sparky, the OC1A has a complimentary inverted output pin, so while one is on, the other is off and vice versa. The PWM output value is double buffered, right? Such that the updated value is only copied into the actual compare register when the timer overflows? You could also trigger it from software if you enabled the overflow interrupt of the timer, and use the ADC conversion complete interrupt to update the PWM value.
Assuming that register is double buffered, the new value would only take effect after the next overflow. ADC is completing conversion, in current setup, at Perhaps I should double ADC clock prescaler to increase accuracy. I need to revisit this. You are correct that compare values are double buffered in PWM mode. Lots of focus on precision, in these comments… one consideration, of course, is that the ear is better at doing some sorts of filtering than a microcontroller.
The write up is inaccurate and without research. Real life class-D runs at much higher frequency. I agree. Of course a true integrated class-D IC will give you nice things like fault detection and shut-off. But I agree this is a very nice hack! And nicely demonstrates the principles of class-D amps!
Sub amplifier can easily filter out the switching frequency as the audio bandwidth is in the lower hundred Hz couple of decades below. The general rule of thumb is to operate the Class D switching frequency at atleast 10x the highest frequency you want to play, for a 20kHz audio signal that would be in the kHz range.
For the cost of these discrete parts you can probably just buy a ready-made part from Maxim or TI. This can only be used for demonstration purposes or with a proper low-pass filter added, and then it would only be useable for low-to-midrange audio frequencies.
Please be kind and respectful to help make the comments section excellent. Comment Policy.
0コメント