Im trying to build the eval board of si8244 which is basically a half bridge design. I want to drive subwoofers with it. Is there any issue with bus pumping which is usually observed in Half bridge design?
Did anyone listened to the si8244 eval board? how is bus pumping with it? these days some diy members say that bus pumping was old generation issue but with new gen its not a problem.
Did anyone listened to the si8244 eval board? how is bus pumping with it? these days some diy members say that bus pumping was old generation issue but with new gen its not a problem.
Any half bridge amplifier has the bus pumping phenomenon and Si8244 based boards are no exception. The reason for the pumping action is that the non-zero speaker return current enters the neutral (mid-point) of the power supply and thereby charges one of the bus capacitors and discharges the other. Dead-time has nothing to do with bus pumping.
Solutions (in order of increasing difficulty):
Solutions (in order of increasing difficulty):
- Inverting the phase of one of the channels and inverting the same later at the speaker reduces bus pumping.
- Using a full-bridge amplifier keeps the current from supply unidirectional giving no pumping.
- Batteries / larger capacitors can reduce the pumping voltage.
- A bidirectional power supply can send the pumped energy back to the battery / grid as applicable.
It depends on the model, but Icepower has something they call ASPC (Adaptive Supply Pump Cancellation), which I assume is an active rectifier like Hypex has on their power supplies that allows the supply to sink current. I've seen Pascal recommend the simple trick of inverting a channel.
You don't seem to get the point...
Since you're running subwoofers, your best bet would to run half the subs inverted with appropriate polarity swap after the amplifier stage.
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Just a note to consider if we use LT1711 as comparator and LT1208 as triangle wave generator at 500KHz with si8244 what are the considerations for Pcb design? like short paths and reduced capacitive coupling between traces etc. Any inputs on this will be quite helpful. I want to try to even 1MHz and see what happens so the pcb layout needs to be stable even at that speeds. Any recommendations in the PCB design?
For any arrangement at any switching frequency the rule is to use the shortest trace lengths possible, especially between the driver and MOSFETs, no other special methods required.
We used 8244 in one of the products and eventually replaced this chip with 8234. Since precision deadtime does not bring any advantages, and we
faced the problem of the initial start of generation. 8244 charges bootstrap capacitor extremely poorly. Another feature is a fairly low output current. At 12V it will be about 1A. Gates 70nC are already a lot.
In general - using this driver for the subwoofer channel is quite strange. You will have to add quite specific current protection and, possibly, a discrete gate driver. Why not use IRS20957?
faced the problem of the initial start of generation. 8244 charges bootstrap capacitor extremely poorly. Another feature is a fairly low output current. At 12V it will be about 1A. Gates 70nC are already a lot.
In general - using this driver for the subwoofer channel is quite strange. You will have to add quite specific current protection and, possibly, a discrete gate driver. Why not use IRS20957?
why not IRS20957 is I would like to have a full bridge post filter feedback with unipolar supply.
As you understand, the output stage and the driver do not really need the ground. If you need to tie input PWM to the negative bus, you can use the IRS20965S or add level shifter. And there is no difference in relation to the feedback circuit.
We have a project of an amplifier with a single-polar power supply and feedback after the ind., I posted the block diagram here, there is even a schematic diagram on other forums.
To operate the modulator, we used the simplest virtual ground circuit and a level shifter circuit on one transistor to control the output stage relative to Vcom.
We have a project of an amplifier with a single-polar power supply and feedback after the ind., I posted the block diagram here, there is even a schematic diagram on other forums.
To operate the modulator, we used the simplest virtual ground circuit and a level shifter circuit on one transistor to control the output stage relative to Vcom.