Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

[budm]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

That AUX winding is for supplying the power once the IC starts running, when the 5v supply output which is also used as the feedback to regulate the output on the FB pin of the IC, since AUX winding is on the same transformer, if the 5V output goes up the AUX voltage will go up at the same time, when the feedback from 5 volt regulate the Voltage both windings, the AUX out put will follow the 5V winding. The spike that damage the Viper is when the circuit first starts up, it can be higher than max VCC, that is why they (I) use ZENER diode to clamp down the AUX output just below the VCC. I used VIPER series our UPS design.
Use the scope and monitor the AUX winding when you first apply the power to the circuits, you will see what I am talking about.
By the way, I use 10 Ohms on the output of the AUX winding in my products. We use a lot of VIPER series in a lot of our products designs due to low cost and reliable as long as you watch for that spike during startup time due the lag time for the regulation loop to become stable.
Another improvement is to put 1/2W 6.2V Zener at the 5v output to clamp down the out to 6.2V max during start up or if the regulation loop has gone bad. Also to find out how well the regulation loop reaction time is, you can switch in and out the max load and min load while monitoring the AUX, and 5V winding outputs.
One good thing about buying 1000's of the IC a year is that you have access to the application engineers that will help you analyze and get the tips and tricks support.

[ben7]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

I am going to use what I have on hand. I plan on using a 9.1V and 12V in series so it should equate to ~21V.

I've had issues before, when trying to use two zeners in series.

Try to find a 16v or 18v or 20v zener. Usually, there will just be a number on the diode, like, '5.1' - that would be a 5.1v zener. Sometimes, they have numbers and letters, so you have to go digging on the web...

[LDSisHere]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

Hm, It will vary, but try using a 100 ohm 1/2 watt resistor. I've seen them be as high as 220 ohms, or as low as 10 ohms.

What is the voltage rating of your zener diode?

I am going to use what I have on hand. I plan on using a 9.1V and 12V in series so it should equate to ~21V.

[ben7]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

Guys, what do you suggest the wattage rating of the resistor for the Vdd circuit should be? It has been almost 20 years since my last AC/DC class and my analysis skills are not up to par to figure this one out.

Thanks,
Lloyd

Hm, It will vary, but try using a 100 ohm 1/2 watt resistor. I've seen them be as high as 220 ohms, or as low as 10 ohms.

What is the voltage rating of your zener diode?

[LDSisHere]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

@Budm

I want to elaborate a little more on what Everell said. His 5VSB mod using the DIP version of the Viper22a works great just as he has laid it out. Somewhere along the line someone suggested an all SMD version of the 5VSB mod. The SOIC-8 version of the Viper22a may not handle the desired 2A load or if it does it would be operating at its' limits. That is where the Viper27 comes into play as the SOIC-16 version has an even higher output rating than the DIP version of the 22A but it is limited by a max 23.5V Vdd.


Guys, what do you suggest the wattage rating of the resistor for the Vdd circuit should be? It has been almost 20 years since my last AC/DC class and my analysis skills are not up to par to figure this one out.

Thanks,
Lloyd

[ben7]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

You are invited to get an old power supply with the two transistor 5vsb circuit, build a small circuit board with the VIPer 27, remove the two transistor circuit components, install the VIPer 27 mod board, and check the results. Just another learning experience opportunity............

I might try this too. I have a cheapo smps which I haven't taken fully apart yet (remember, the 'CS180' PSU? ). I will be ordering some other parts from Mouser soon, so might as well get a Viper27 or two.

I might just draw a circuit of the 5vsb, then take the parts off the board, and build the circuit again on a new board. (I'm not planning on using that cheapo PSU, ever.....)

BTW, that DVD player PSU board does have a Viper22A on it. The capacitors are cheapos, but the design of the PCB is quite nice. Some 'Sunpower' brand.

[everell]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

Bud: we need to get on the same page.....we are talking about a zener circuit for the VIPer 27, not the VIPer 22A. Take a look at the data sheet, the maximum operating voltage is 23.5 volts. The output (5vsb) is regulated by voltage going to the feedback pin. That is correct. But the Vdd to the VIPer chip comes from the feedback winding of the 5vsb transformer. The power supply typically allows for zero to 2 amps of loading on the 5vsb rail. I doubt that your monitor has to deal with that much loading variation. But on the power supply, as loading increases, the Vdd from the feedback winding does increase, sometimes beyond the maximum operating voltage - in this case 23.5 volts. On most of these pwm chips the maximum operating voltage point causes the chip to turn off as a protection to the power supply.

You are invited to get an old power supply with the two transistor 5vsb circuit, build a small circuit board with the VIPer 27, remove the two transistor circuit components, install the VIPer 27 mod board, and check the results. Just another learning experience opportunity............

[budm]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

Well, for example in Dell monitor, they put 22V zener right after the rectifier to limit the spike from AUX winding during first couple cycle of the startup. the Viper is usually will be running at around 14~15VDC range, max input to VCC pin is 38VDC.

[ben7]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

https://cdn.badcaps-static.com/pdfs/...1660d59539.pdf
Are you trying to limit the output volatge by controlling the VCC of the Viper? The out out is controlled by the opto feed back, the AUX winding of the transformer is for running the IC once the circuit starts up.
The VCC operating range is 9 V to 38 V.
"Power supply of the control circuits. Also provides a charging current during start up
thanks to a high voltage current source connected to the drain. For this purpose, an
hysteresis comparator monitors the VDD voltage and provides two thresholds:
- VDDon
: Voltage value (typically 14.5 V) at which the device starts switching and turns
off the start up current source.
- VDDoff
: Voltage value (typically 8 V) at which the device stops switching and turns on
the start up current source."

No, we are just trying to find the best way (currently a zener and resistor) to limit the AUX voltage, so the chip doesn't get blown up.

[budm]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

https://cdn.badcaps-static.com/pdfs/...1660d59539.pdf
Are you trying to limit the output volatge by controlling the VCC of the Viper? The out out is controlled by the opto feed back, the AUX winding of the transformer is for running the IC once the circuit starts up.
The VCC operating range is 9 V to 38 V.
"Power supply of the control circuits. Also provides a charging current during start up
thanks to a high voltage current source connected to the drain. For this purpose, an
hysteresis comparator monitors the VDD voltage and provides two thresholds:
- VDDon
: Voltage value (typically 14.5 V) at which the device starts switching and turns
off the start up current source.
- VDDoff
: Voltage value (typically 8 V) at which the device stops switching and turns on
the start up current source."

[ben7]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

I'll give an honest answer (no jokes!)......I don't know. Would be an interesting experiment to try. I did try inserting a regulator chip, a regulator circuit, and a low power regulator in series with the diode. In all three cases, the 5vsb was dead. No Vdd to the pwm chip. My conclusion is that the current coming from this feedback winding is very low, too low to drive a voltage regulator in series. That is why the circuit I was suggesting MIGHT work. As for your capacitor idea, try it and report back to us on how well it works, doesn't work, or blows up!

Actually, I could try it! I think I still have the PSU from some DVD player, and as far as I can remember, it used a Viper22 chip

[everell]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

A few suggestions, first, you should try to have an insulating pad in-between the PSU heatsink, and the VIPER board. I am talking about the kind they put 'tween power transistors and heatsinks. This could help cool it off a little more.

Second, since the operating frequency of the smps remains just about constant, you can use a capacitor of the correct value to limit the current. This is called capacitive reactance. The capacitor would go before the rectifying diode, where the AC is present. The capacitor also dissipates very little heat(MUCH less than a resistor).
However, everell, do you think this would work? I don't know if the varying duty cycle would interfere.

I'll give an honest answer (no jokes!)......I don't know. Would be an interesting experiment to try. I did try inserting a regulator chip, a regulator circuit, and a low power regulator in series with the diode. In all three cases, the 5vsb was dead. No Vdd to the pwm chip. My conclusion is that the current coming from this feedback winding is very low, too low to drive a voltage regulator in series. That is why the circuit I was suggesting MIGHT work. As for your capacitor idea, try it and report back to us on how well it works, doesn't work, or blows up!

I would expect the capacitor idea to work great if it were the flux capacitor (just kidding)!!!

[ben7]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

I think I will work on making a board for the Viper27 with this voltage limiting circuit. I think I will make it so I can easily change out the resistor so it will be easy to see what effect different values have on the overall performance. It may be crude as I will end up using through hole parts as SMD until I have enough data to know what values work, then I will order the correct SMD parts. I think this circuit may make the Viper27 usable on Antecs so thanks for taking the time to post it.

Also, I hope to have my load tester built by Thursday or Friday but this depends on how much free time I have between now and then.

A few suggestions, first, you should try to have an insulating pad in-between the PSU heatsink, and the VIPER board. I am talking about the kind they put 'tween power transistors and heatsinks. This could help cool it off a little more.

Second, since the operating frequency of the smps remains just about constant, you can use a capacitor of the correct value to limit the current. This is called capacitive reactance. The capacitor would go before the rectifying diode, where the AC is present. The capacitor also dissipates very little heat(MUCH less than a resistor).
However, everell, do you think this would work? I don't know if the varying duty cycle would interfere.

[LDSisHere]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

How is the temperature of the VIPer27 compared to the VIPer22, after, say, 10 minutes?

I have not had much time to work with these boards yet. I did not check the 22 but the 27 was ~175 F at the legs after about 5 minutes with a 16 ohm external load. The board for the 27 has ~205mm^2 of copper on the drain which is twice what the data sheet shows. I put even more copper under the SOIC 22 but I have not taken the time to calculate the actual area. The Viper22 calls for 200mm^2 so hopefully it does not get too hot.

With Vdd at about 17 volts, the first ten ohm load resistor should put it about 5 volts higher or about 22 volts, right on the edge of overvoltage shut down. So how can we get around this?

Here is the drawing of the 5vsb for a Thermaltake Toughpower 1500 watt power supply I am currently working on. The 5vsb circuit is rated for 6 amps fully loaded, thats 30 watts! So how do they get around Vdd voltages climbing?

Notice at the bottom of the drawing, the feedback winding of the 5vsb transformer, feeds the diode, then a 110 ohm resistor, then a zener to ground along with the filter capacitor to ground. This provides the Vdd to the pwm chip.

This might work with the VIPer 27 circuit. The 110 ohm resistor is a current limiter for the zener. As long as the 110 ohm resistor does not drop the voltage too much under no load, the zener could be selected for 18 to 20 volts, and the problem would be solved.......I hope. We will have to wait and see how it responds once you get your load tester built.

I think I will work on making a board for the Viper27 with this voltage limiting circuit. I think I will make it so I can easily change out the resistor so it will be easy to see what effect different values have on the overall performance. It may be crude as I will end up using through hole parts as SMD until I have enough data to know what values work, then I will order the correct SMD parts. I think this circuit may make the Viper27 usable on Antecs so thanks for taking the time to post it.

Also, I hope to have my load tester built by Thursday or Friday but this depends on how much free time I have between now and then.

[everell]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

You should start a new thread for it!

30 watts on 5vsb?! Thats the first time I've heard of that... overkill??

Uses the new flux capacitor..................

[ben7]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

With Vdd at about 17 volts, the first ten ohm load resistor should put it about 5 volts higher or about 22 volts, right on the edge of overvoltage shut down. So how can we get around this?

Here is the drawing of the 5vsb for a Thermaltake Toughpower 1500 watt power supply I am currently working on. The 5vsb circuit is rated for 6 amps fully loaded, thats 30 watts! So how do they get around Vdd voltages climbing?

Notice at the bottom of the drawing, the feedback winding of the 5vsb transformer, feeds the diode, then a 110 ohm resistor, then a zener to ground along with the filter capacitor to ground. This provides the Vdd to the pwm chip.

This might work with the VIPer 27 circuit. The 110 ohm resistor is a current limiter for the zener. As long as the 110 ohm resistor does not drop the voltage too much under no load, the zener could be selected for 18 to 20 volts, and the problem would be solved.......I hope. We will have to wait and see how it responds once you get your load tester built.

You should start a new thread for it!

30 watts on 5vsb?! Thats the first time I've heard of that... overkill??

[budm]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

NCP1200 spec-OPERATION. The output voltage is done through the opto on FB pin.

[everell]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

With Vdd at about 17 volts, the first ten ohm load resistor should put it about 5 volts higher or about 22 volts, right on the edge of overvoltage shut down. So how can we get around this?

Here is the drawing of the 5vsb for a Thermaltake Toughpower 1500 watt power supply I am currently working on. The 5vsb circuit is rated for 6 amps fully loaded, thats 30 watts! So how do they get around Vdd voltages climbing?

Notice at the bottom of the drawing, the feedback winding of the 5vsb transformer, feeds the diode, then a 110 ohm resistor, then a zener to ground along with the filter capacitor to ground. This provides the Vdd to the pwm chip.

This might work with the VIPer 27 circuit. The 110 ohm resistor is a current limiter for the zener. As long as the 110 ohm resistor does not drop the voltage too much under no load, the zener could be selected for 18 to 20 volts, and the problem would be solved.......I hope. We will have to wait and see how it responds once you get your load tester built.

[ben7]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

Check out the second picture, I have marked the capacitor you are suggesting.



From what I saw from your DM211 design and the Viper27 datasheet I was thinking that the feedback circuit would not need a resistor but I was not sure. I figured it would be easier to have one I could remove than than it would be to add one later if it actually was needed. Plus I was curious to see what it would do to the circuit, I was surprised by the result as it was opposite of what I expected. I did remove it and I replaced it with just a wire as you suggested and as you can see from the picture it is now working properly. With the 16 ohm load my ATX tester puts on it the Vdd was running at ~17V. I cannot wait to make the load tester to see what both chips will do compared to the DIP Viper22A.

Thanks for the feedback everyone.

Good job!

P.S. - The datasheets don't lie! (VIPer27 datasheet shows no resistor for feedback)

How is the temperature of the VIPer27 compared to the VIPer22, after, say, 10 minutes?

[LDSisHere]

Re: Antec Smart Power SP-350 5VSB mod using VIPer 22A pwm chip

I say the same. Also, there should be a small capacitor (10nF?) across the opto transistor, to help make it stable.

Check out the second picture, I have marked the capacitor you are suggesting.

You have blue wire going to 9.1k to ground. Remove the 9.1k resistor and replace it with a small piece of wire. This will short the blue wire to ground. Now measure the emitter of the optoisolator (pin 3) with respect to ground....should measure zero ohms. Now measure the feedback pin of the VIPer 27 with respect to optoisolator collector (pin 4)......should also measure zero ohms.

The VIPer 27 does not use that 9.1k resistor. Wiring to the optoisolator pins 3 & 4 is backwards from the VIPer 22A.

From what I saw from your DM211 design and the Viper27 datasheet I was thinking that the feedback circuit would not need a resistor but I was not sure. I figured it would be easier to have one I could remove than than it would be to add one later if it actually was needed. Plus I was curious to see what it would do to the circuit, I was surprised by the result as it was opposite of what I expected. I did remove it and I replaced it with just a wire as you suggested and as you can see from the picture it is now working properly. With the 16 ohm load my ATX tester puts on it the Vdd was running at ~17V. I cannot wait to make the load tester to see what both chips will do compared to the DIP Viper22A.

Thanks for the feedback everyone.