Electronics > Projects, Designs, and Technical Stuff
Texas Instruments 3116D (ClassD) amp chip
DW1961:
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--- Quote from: TimFox on August 16, 2020, 05:13:25 pm ---The conflict between voltage and current limits is why vacuum tube amps use transformers with secondary taps for different load impedance, to get the same power output at different loads. From the tube’s “characteristic curves” one can determine the higher impedance load line (at the plates) that satisfies the voltage and current limits without exceeding the plate dissipation power.
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Here is something. According to this calculator, you're never ging to get 200 watts out of that amp, not continuous. As Tim has said, sure, with caps and for brief burst, but nowhere near 200 watts continuous. That is, unless the calculator is not taking into consideration other amp related/audio related parameters:
Most importantly, the power supply is 24V and 5 Amps. Anyway, I have no idea, again, why they would use two chips with a 24v/5A driver. There must be some reason, at least that's what my head is telling me. In fact, at 2 Ohms, in order to not exceed the driver's 5 Amp max, you get 50 watts total because the voltage drops to 10V. In order to get 200 watts total, you would have to go to 10 Amps/ 20V. (All according to the calculator).
The images are suppose to display inline full size, so if they are not, no idea. All options default to end of post thumbnails.
tooki:
You still don’t understand the practical significance of the whole RMS vs peak voltage thing I laid out for you in detail.
DW1961:
--- Quote from: tooki on August 16, 2020, 07:41:17 pm ---You still don’t understand the practical significance of the whole RMS vs peak voltage thing I laid out for you in detail.
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Gonna go back and read that again.
DW1961:
--- Quote from: tooki on August 15, 2020, 12:54:26 pm ---
3. In a sine wave, the peak voltage is only reached for a tiny amount of time. Most of the time is less. So we measure using RMS, the value of the AC signal given as the DC voltage with the equivalent heating power. For a pure sine wave, the RMS value is the square root of 2 (about 0.707) times the peak voltage (which in an amp is at most the VCC). So for your 24V VCC, the RMS becomes 24x0.707, or about 17V. And that gives you a maximum average power of 36W into 8 ohms (a current draw of 2.125A). (You can also calculate it as VCC2/2x(impedance).)
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Ok, so I see how you get peak power from a 24V power supply. I did it like this, becasue the rated power on the supply is 24V RMS:
So:
24/.707 = 34V
and
34*.707=24.7V
Yes, they are talking about "max" power output, so sure, you can get 200 watts out of a 24V RMS power supply rated at 5A.
Back to my original problem, I'm not seeing how you get anymore than 100 watts continuous power at 4 Ohms using that 24V/5A power supply.
I think some of my problem is that I don't see where contious power or peak power is stated int eh Texeas Instruments spec file:
The chips are rated at peak power of x2 50 watts at 4 Ohms. (Peak, Continuous?)
Top of document:
https://www.ti.com/lit/ds/symlink/tpa3116d2.pdf?ts=1596921462063&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FTPA3116D2
Each 3116D chip is rated for a continuous power of 50 watts @ 21V and 4 Ohms. (Total or x2?)
Section 6.6AC Electrical Characteristics (Same document)
If the continuous power spec means 50 watts total at 4 Ohms @ 21V, then ok:
So you can get 100 watts @ 20V and 5A and 4 Ohms from a 24V/5A continuous power supply.
So using two 3116D chips, you can get double the power, then, at 4 Ohms. (two chips at 2 Ohms bridged = 4 Ohms.)
How am I doing?
rsjsouza:
--- Quote from: DW1961 on August 17, 2020, 12:02:20 am ---
Yes, they are talking about "max" power output, so sure, you can get 200 watts out of a 24V RMS power supply rated at 5A.
Back to my original problem, I'm not seeing how you get anymore than 100 watts continuous power at 4 Ohms using that 24V/5A power supply.
I think some of my problem is that I don't see where contious power or peak power is stated int eh Texeas Instruments spec file:
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Table at section 6.6 of the datasheet indicates 50W continuous at 4 ohms with 21Vcc. According to the description, this is per channel - in BTL it will do 100W under the same conditions. A side note: keep in mind this is under 10% of signal distortion - far from a hi-fi under these conditions (it will have less distortion if driven at lower power).
--- Quote from: DW1961 on August 17, 2020, 12:02:20 am ---So you can get 100 watts @ 20V and 5A and 4 Ohms from a 24V/5A continuous power supply.
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The output power equals the supply power minus losses - in other words, the efficiency of the circuit. 24V/5A will give you 120W of supply, which may be just enough for continuous operation of 100W total or 50W per channel - the efficiency is shown at figure 23 of the datasheet.
Higher peak power may or may not be attained. Section 7 describes the drivers will pull up to 7.5A at peak conditions (which gives a 200W peak under 4 ohms).
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