Hi
I make 400w SMPS with TL494 (input 11V,output 300V)
i use 4+4 turns for pri and 110 turns for sec
my schematic not have feedback and just controll pwm by pin3(with 5k pot)Which should also be fixed on the middle, unless the Output goes down
I want to get feedback from 300v of output, but I did not notice the work of op amps in TL494 (I just want to use an op amp of TL494)
can you help me please?
sorry for my bad english🙂
I make 400w SMPS with TL494 (input 11V,output 300V)
i use 4+4 turns for pri and 110 turns for sec
my schematic not have feedback and just controll pwm by pin3(with 5k pot)Which should also be fixed on the middle, unless the Output goes down
I want to get feedback from 300v of output, but I did not notice the work of op amps in TL494 (I just want to use an op amp of TL494)
can you help me please?
sorry for my bad english🙂
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There is a lot of information on the internet about using the TL494.
I forget what Vref is on the TL494 but feedback is simply a matter of a voltage divider across the output to provide a feedback voltage = Vref at the output voltage.
I forget what Vref is on the TL494 but feedback is simply a matter of a voltage divider across the output to provide a feedback voltage = Vref at the output voltage.
Attachments
It is usual to use an opto isolator sensing the output voltage. When it increases above the threshold set by you, the receiver signals pin 1 to turn off.
this is my sch for Oscillator
is this have problem?
when i turned the pot (pot installed to pin3 in test) just output voltage is decreasing
and the current on the input increases strongly
I think if the problem is not resolved, I will have the same problem with feedback (the feedback will be attached to pin 3 in the end)
is this have problem?
when i turned the pot (pot installed to pin3 in test) just output voltage is decreasing
and the current on the input increases strongly
I think if the problem is not resolved, I will have the same problem with feedback (the feedback will be attached to pin 3 in the end)
The dead time resistance is 47 ohms. Almost this problem was resolved.
But when the potentiometer pin 3 is rotated to the negative (almost close to zeroing pin 3 of 494), the output will fall instead of the gain
But when the potentiometer pin 3 is rotated to the negative (almost close to zeroing pin 3 of 494), the output will fall instead of the gain
The diagram is incomplete. Do you have a complete diagram?
Why the 47 ohm resistor on pin 4?
For now, connect pins 1 and 16 to pin 7. Connect pins 2 and 15 to pin 14.
Why the 47 ohm resistor on pin 4?
For now, connect pins 1 and 16 to pin 7. Connect pins 2 and 15 to pin 14.
I struggled with any feedback I tried
I decided to make the output voltage without receiving feedback (no trouble getting feedback from the output voltage)
Pin 3 in this case is negative (The potentiometer connected to it is completely negative)
The schematic is being completed and will be sent.
The 47 ohm resistor added a friend's suggestion to control DeadTime, but I do not see any effect (I do not have an oscilloscope now)
The last method that I used to control the chips of the emps replied (two params were parallel and connected to VREF and GND)
My problem is with the feedback of high voltage drops
, in which case the switching goes to the short circuit and a lot of flow goes on 12 volt switching inputs.
One of the MOSFETs also heats up
I decided to make the output voltage without receiving feedback (no trouble getting feedback from the output voltage)
Pin 3 in this case is negative (The potentiometer connected to it is completely negative)
The schematic is being completed and will be sent.
The 47 ohm resistor added a friend's suggestion to control DeadTime, but I do not see any effect (I do not have an oscilloscope now)
The last method that I used to control the chips of the emps replied (two params were parallel and connected to VREF and GND)
My problem is with the feedback of high voltage drops
, in which case the switching goes to the short circuit and a lot of flow goes on 12 volt switching inputs.
One of the MOSFETs also heats up
Your friend may be confusing the 494 DT control with the DT control on the SG type driver ICs.
What do you mean that pin 3 is negative?
For now, disconnect the potentiometer and connect the IC as suggested in post #9.
What do you mean that pin 3 is negative?
For now, disconnect the potentiometer and connect the IC as suggested in post #9.
and IC works well
Thats output:
But when I turn pot pin 3, one of the MOSFETs gets hot.
I do this "connect pins 1 and 16 to pin 7. Connect pins 2 and 15 to pin 14. "and IC gave a very low output for a second, and then it turned on
If the IC is constantly detecting Vin < Vref then it will try to increase the output. As this will not increase Vin the IC will eventually result in 100% duty cycle. Hence one MosFET will be hard ON.
Do you mean Vin to the input voltage to the comparator?
My circuit dont have feedback now
How do I set the Duty cycle to 49 or 50%?
Should I set pin 4 voltage between 2.5 and 2.7?
In the datasheet there is a Duty cycle_dead time control voltage diagram.
My frequency is 22 kHz.
when i turn pin3 pot What features of ic changed?
Pin3 is connected to gnd(because the pot of the pin is turned to the gnd completely)
Duty cycle will be 50% when Vin = Vref. Depending on the output transformer of course.
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