Discrete Class BD Concept

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Simple circuit of class BD design can be achieved with discrete design.
 

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I found a thread on this forum mentioning the class BD used by Rockford. There was no elaborate description of how class BD differs from a self-oscillating class D like the UCD. I see no lead network in the circuit.
Do you know the idea behind class BD? It is the first time I hear about it.
 
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ÑBD modulation has each comparator for out A and B
Please zoom plot voltage in second post. That is a specific switching result from a class BD.

As a result BD class only need half switching speed of other class D because ripple out A and B is cancel each other
 
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Many tanks to you both.

I believe to have understood a concept:
The Class BD relates to a balanced input with two signal lines (a signal balancing circuit is shown to the left in the schematics) and BTL output configuration with two output lines. Each input signal is modulated separately with an individual comparator and controlling only one output. If a traditional clock-controlled modulator is used, the same triangle reference-signal is used for the two comparators such that switching of the output lines is synchronized but differ in switching moment. If the modulation is through a self-oscillating design, the two outputs may not be synchronous. Due to the two individual comparators, the switching moments of the two outputs are normally displaced such that the resulting switching frequency appears higher than if fully synchronous switching at the same moment is used. Thereby, the output filter becomes more efficient or the switching frequency can be reduced with the same effect of the output filter.

What confuses me a bit is discussions about “AD Vs BD modulation” where AD modulation is described as a two-level modulation and BD modulation as a three-level modulation.
AD Vs BD Modulation in Class-D, posting #23.
How many modulation methods in Class D amplifier ?, posting #3.
From what kartino shows, this design is apparently a two-level design which the switching simulation confirms. Or, does temporary current recirculation at one of the rails count as a third level?

“Eva” is once more the expert (I still have my doubts if her/(his?) small tumb-nail photo shows 25% of Eva's face) and Chris has a nice HK amplifier running class BD.

Please correct me if I am wrong.
 
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Hi

As you know my knowledge is limited.;)
i understand from the experiment that the DDX -->STA chipset is BD modulated.


e.g. STA 326 datasheet:
Three channels of DDX® processing are provided. This high-quality conversion from PCM
audio to patented DDX® 3-state PWM switching provides over 100 dB of SNR and dynamic
range.


maybe i am wrong

chris
 
Thanks for your posting, Chris.
It is a very complex chip. Fig.6 of the datasheet shows a 3-state output signal with a dead-time. It seems to be a very futuristic product with DSP and power amplifier integrated in one chip. Impressive, but only for experienced DIY'ers.
In your case, did you find the fault on the HK?
 
Thanks for your posting, Chris.
It is a very complex chip. Fig.6 of the datasheet shows a 3-state output signal with a dead-time. It seems to be a very futuristic product with DSP and power amplifier integrated in one chip. Impressive, but only for experienced DIY'ers.
In your case, did you find the fault on the HK?

Hi

Th HK is actually working im my toughters room..feeded with her smartphone:rolleyes:
actually i have no interest to searching at the HK200 or HK500 any more.
i guess in february i was absolutly at my beginning of my DIY career:D...so i did a lot of nonsens :D including the measurments.

with the knowledge today i guess it was the outputfilter which doesn´t fit to my speakers....

chris
 
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