Just asking, do you mean dc-blocking filter? (learning alongside....)but where's your filtering feeding the speaker?.
No, for a class-D amp you require a low-pass filter to the speaker to remove the HF carrier, it's a combination of inductors and capacitors.Just asking, do you mean dc-blocking filter? (learning alongside....)
I presumed the frequency in the simulation was nothing to do with the actual project?, unless of course he's simply making a sounder - and not a class-D amp?.Not sure I understand what you are trying to do.
Such a low PWM frequency will be reproduced by the speaker as a very loud sound.
For audio reproduction the PWM frequency has to be much higher than highest audio frequency.
You're confusing the issue by referring to it as PWM, which it's not - it's just a crude squarewave buzzer.The PWM signals hitting the speaker (after the H-Bridge) are the same pulse widths you see on the scope, just 0-12Vp-p (amplified).
The schematic in my opening post shows those 2 resistors as being 100Ω each, which is what the RATO RT0618 datasheet specifies in its example application circuit, but the siren you see in my video uses two 220Ω instead. In my testing, the difference between 100Ω and 220Ω is negligible on the final output amplitude. But increasing them to 1.5kΩ each drops the amplitude from 11.9V to about 6.0V.Your original schematic and the schematic from RATO do not have the 220 ohm resistors that you are trying to use as volume controls. Which resistors?
I didn't look at the datasheets for your (Oriental?) transistors because sometimes they are not written in English but transistors all have a wide range of current gain. RATO probably used 100 ohms so that all of them turn on properly so your might have high gain and work with higher resistance.The schematic in my opening post shows those 2 resistors as being 100Ω each, which is what the RATO RT0618 datasheet specifies in its example application circuit, but the siren you see in my video uses two 220Ω instead. In my testing, the difference between 100Ω and 220Ω is negligible on the final output amplitude. But increasing them to 1.5kΩ each drops the amplitude from 11.9V to about 6.0V.