Now , i just search some IC to do the triangle wave generator.
do you have any suggest for any IC ???
Now , i using LF347 , but it still not good enought.
The photo i posted , it generated by LF347.
do you have any suggest for any IC ???
Now , i using LF347 , but it still not good enought.
The photo i posted , it generated by LF347.
HI ,
I search the IC you said , but it seems not easy to buy.
But I contact to the LT company.
I will search some LT's IC , looks if it have something suitable for me.
Do you still have others suggestion ???
I think about the feedback network so much .
you ever asked me about does the output of comparator lt1016 saturated.
I think that , if the feedback RC-lp filter , the Fc set too high.
The voltage of waveform that feedback to error amp , will too high to let the error amp go to saturate.
Is that right ??
So , if the Fc of feedback RC-lp filter set too low to good but higher for audio band??
I search the IC you said , but it seems not easy to buy.
But I contact to the LT company.
I will search some LT's IC , looks if it have something suitable for me.
Do you still have others suggestion ???
I think about the feedback network so much .
you ever asked me about does the output of comparator lt1016 saturated.
I think that , if the feedback RC-lp filter , the Fc set too high.
The voltage of waveform that feedback to error amp , will too high to let the error amp go to saturate.
Is that right ??
So , if the Fc of feedback RC-lp filter set too low to good but higher for audio band??
Hey y'all,
First of all, I'd like to say hi to all present
Going onto the high current subject, I do see that on your schematic you only have a 10R resistor going from HO, LO to the gates of the mosfets. By looking at the drive onto the IR chip, I see that you have no control of dead times, causing you to have too high a shoot-through current in your mosfets.
B/c your rising and falling edges are occurring at the same times on BOTH inputs of your IR chip, your mosfets are both turning off and on at the same time. One way to solve this and possibly your main problem, is to increase the gate resistors to a value in the range of 100 to 270R.
To further increase your deadtime you can place a 74HC14 buffer between the PNP drivers before the IR chip and the IR chip input themselves. The best way is to do this and isolate the 74HC inputs with a 330R resistor in series with its inputs while placing a 56pF cap between the 74HC input to ground .
Using both methods you can achieve a 150nS deadtime between each mosfet activation and turning off. Remember that too high a DT will mean a higher THD, especially since you don't have a double compensated NFB like the ones used in the Crest LT series amp.
As far as the mosfets goes, I would suggest the IRF540NS which have a Cgs of roughly 1800pF which are easy to drive.
Also, place a schottky diode parallel with each mosfet, making sure they are connected from source to source and from drain to drain. Redundantly said, these diodes are to "replace" the mosfets' internal body diodes as fly-back suppressors. The mosfets' internal diodes are far too slow and have a high turn on transient voltage causing lots of internal losses.
For more ideas, visit my website for more info: http://www.geocities.com/riggerman2375/
The class d amp I feature is capable of running 150 watts into 4 ohms with a heatsink of 10x5x0.3cm without fins. That's for both channels. I built this design based on common topologies elsewhere in the net, none of the design ideas are mine. I did take the time to refine the ideas around to build my version.
Currently I am designing a 500 Watt monoblock for a local partner.
Good luck to all and happy amping!!!
First of all, I'd like to say hi to all present
Going onto the high current subject, I do see that on your schematic you only have a 10R resistor going from HO, LO to the gates of the mosfets. By looking at the drive onto the IR chip, I see that you have no control of dead times, causing you to have too high a shoot-through current in your mosfets.
B/c your rising and falling edges are occurring at the same times on BOTH inputs of your IR chip, your mosfets are both turning off and on at the same time. One way to solve this and possibly your main problem, is to increase the gate resistors to a value in the range of 100 to 270R.
To further increase your deadtime you can place a 74HC14 buffer between the PNP drivers before the IR chip and the IR chip input themselves. The best way is to do this and isolate the 74HC inputs with a 330R resistor in series with its inputs while placing a 56pF cap between the 74HC input to ground .
Using both methods you can achieve a 150nS deadtime between each mosfet activation and turning off. Remember that too high a DT will mean a higher THD, especially since you don't have a double compensated NFB like the ones used in the Crest LT series amp.
As far as the mosfets goes, I would suggest the IRF540NS which have a Cgs of roughly 1800pF which are easy to drive.
Also, place a schottky diode parallel with each mosfet, making sure they are connected from source to source and from drain to drain. Redundantly said, these diodes are to "replace" the mosfets' internal body diodes as fly-back suppressors. The mosfets' internal diodes are far too slow and have a high turn on transient voltage causing lots of internal losses.
For more ideas, visit my website for more info: http://www.geocities.com/riggerman2375/
The class d amp I feature is capable of running 150 watts into 4 ohms with a heatsink of 10x5x0.3cm without fins. That's for both channels. I built this design based on common topologies elsewhere in the net, none of the design ideas are mine. I did take the time to refine the ideas around to build my version.
Currently I am designing a 500 Watt monoblock for a local partner.
Good luck to all and happy amping!!!
good ideas for a triwave generator...
datasheet design for the NE566 (My preffered choice) Simple to set up and gives a fully symmetrical output. can eb DC isolated without loss of purity.
the MAX038 which can do PWM and can be sinchronised with a second one to do a stereo version but can be as high as $20 (US Dollars)
I'd stay away from opamp based generators as they can be troublesome to linearize and isolate from PSU noise.I tried that route before. The NE566 worked much better in all regards.
Happy Amping!
datasheet design for the NE566 (My preffered choice) Simple to set up and gives a fully symmetrical output. can eb DC isolated without loss of purity.
the MAX038 which can do PWM and can be sinchronised with a second one to do a stereo version but can be as high as $20 (US Dollars)
I'd stay away from opamp based generators as they can be troublesome to linearize and isolate from PSU noise.I tried that route before. The NE566 worked much better in all regards.
Happy Amping!
hi !
classdrigger,
do you think that I have experiencing certain amount of dissipation on fets and IR2113 due to lack of ultra-fast clamping diodes on irf640 ? btw I use 100ohm resistor in gate branch and 15ns 200V 2A diode for fast discharge of gate.
classdrigger,
do you think that I have experiencing certain amount of dissipation on fets and IR2113 due to lack of ultra-fast clamping diodes on irf640 ? btw I use 100ohm resistor in gate branch and 15ns 200V 2A diode for fast discharge of gate.
Hi Zkaiser
I can guess that if you're only using the internal body diode of the mosfets as clamping diodes, if this is true, indeed you are having heating issues in your mosfets. body diodes aren't fast enough to clamp the back EMF fro the output chokes. As always, use only schottky diodes for this such as MBR820 or the RBR820. F303 do work ok in small applications but for larger amps over 50 watts the MBR's are far better. Another diode that you can use is the MBR460 or the MBR490 which are rated at 3A with a VF of 345mV and a Vr of 1Kv Depending on your particular topology, 100 ohms sounds reasonable for DT control.
Remember that the IR2113 does not provide good DT control so is important to create it before the IR chip or as far as in the gate resistors. For them, you can use up to 270 ohms without issues. The IRF640's need at least 12 to 14 volts pk/pk of drive in order to fully enhance the oxide channel. As a general rule you can go safely with 15 volts, but remember that with a higher pulse swing, the dead time must increase as the Miller plateau is reached sooner causing the mosfet to begin turning on sooner.
A good way to control Dead Time and Shoot Through current problems is by placing a small coil in series with each of your sources and the central connection to your low pass filter. Usually this coil is made with 20 to 25 turns close-wound single-layer with solid 1mm enamelled wire. noferrite core is used and overall length of the coil is about 25mm. I've used this method with great results each time.
I hope this answers some of your questions
Happy Amping!
I can guess that if you're only using the internal body diode of the mosfets as clamping diodes, if this is true, indeed you are having heating issues in your mosfets. body diodes aren't fast enough to clamp the back EMF fro the output chokes. As always, use only schottky diodes for this such as MBR820 or the RBR820. F303 do work ok in small applications but for larger amps over 50 watts the MBR's are far better. Another diode that you can use is the MBR460 or the MBR490 which are rated at 3A with a VF of 345mV and a Vr of 1Kv Depending on your particular topology, 100 ohms sounds reasonable for DT control.
Remember that the IR2113 does not provide good DT control so is important to create it before the IR chip or as far as in the gate resistors. For them, you can use up to 270 ohms without issues. The IRF640's need at least 12 to 14 volts pk/pk of drive in order to fully enhance the oxide channel. As a general rule you can go safely with 15 volts, but remember that with a higher pulse swing, the dead time must increase as the Miller plateau is reached sooner causing the mosfet to begin turning on sooner.
A good way to control Dead Time and Shoot Through current problems is by placing a small coil in series with each of your sources and the central connection to your low pass filter. Usually this coil is made with 20 to 25 turns close-wound single-layer with solid 1mm enamelled wire. noferrite core is used and overall length of the coil is about 25mm. I've used this method with great results each time.
I hope this answers some of your questions
Happy Amping!
I am succesfully using IRF640N mosfets with IR2110 and 10 ohm gate resistors, with +/-60V supplies and 12V gate drive voltage. I get high efficiency and no heating at all with no signal.
My sw. frequency is 300KHz with around 50ns rise/fall times (measured at the switching output waveform) and I don't use parallel schottkys...
Hope this helps.
My sw. frequency is 300KHz with around 50ns rise/fall times (measured at the switching output waveform) and I don't use parallel schottkys...
Hope this helps.
I try to down the triangle frequency to 50KHz.
But it seem can't work .
I probe the output of the mosfet.
The square waveform not good enought.
The eage of rise up , looks has a radius .
Looks like a square waveform using snubber network.
It burned out my resistor serise with High-side mosfet.
And Mosfet also burned out.
If i have limited the input signal bandwith between 15Hz to 500Hz.
Do i need so high modulation freqency ,like 200KHz.???
I will post some photo later.
But it seem can't work .
I probe the output of the mosfet.
The square waveform not good enought.
The eage of rise up , looks has a radius .
Looks like a square waveform using snubber network.
It burned out my resistor serise with High-side mosfet.
And Mosfet also burned out.
If i have limited the input signal bandwith between 15Hz to 500Hz.
Do i need so high modulation freqency ,like 200KHz.???
I will post some photo later.
titanchen68
some suggestion about burned fets, try to use current limited power supply, use two lab pow.suppy and set curret limit at 1A for +/- rail to be sure that you wont burn power mosfets !
I think that you have to use at least 250kHz to be able to have good carrier suppresion at output filter (choke and cap) but for more resolution in sound you need more carrier freq. some tripath solutions goes to 1MHz with carrier signal . . .so try and inform us about work progress .... cya.
regards
Zeljko Kaiser
some suggestion about burned fets, try to use current limited power supply, use two lab pow.suppy and set curret limit at 1A for +/- rail to be sure that you wont burn power mosfets !
I think that you have to use at least 250kHz to be able to have good carrier suppresion at output filter (choke and cap) but for more resolution in sound you need more carrier freq. some tripath solutions goes to 1MHz with carrier signal . . .so try and inform us about work progress .... cya.
regards
Zeljko Kaiser
btw, are you still having trouble with big turn on get current ?;
if so you need to add dead time before ir2110, I was also having same problem when I first build iraudoamp and adding 3k res 33p cap and discharge path diode 1n4148 added just enough dead time to reduse unwanted crossconduction and lowered turnon and idle current. And try with 47-100ohm res. at mosfet gates
if so you need to add dead time before ir2110, I was also having same problem when I first build iraudoamp and adding 3k res 33p cap and discharge path diode 1n4148 added just enough dead time to reduse unwanted crossconduction and lowered turnon and idle current. And try with 47-100ohm res. at mosfet gates
You mean i have to use 250KHz at least ...
I use 200kHz yet , now i want to use 50KHz to build.
Because i only need to handle 15Hz to 500Hz signal.
so , i think 50KHz is enought for me. Is that right ??
Thank , i had have not this problem.
But i still will add a dead time control ... thanks a lot.
I use 200kHz yet , now i want to use 50KHz to build.
Because i only need to handle 15Hz to 500Hz signal.
so , i think 50KHz is enought for me. Is that right ??
zkaiser said:
Thank , i had have not this problem.
But i still will add a dead time control ... thanks a lot.
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