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TNY290 tryes to start but pauses

Posted by: MFog on

Hello PI...

I have a fairly straight forward design with at TNY290 with a Wurth designed trafo.
Designs attached :
The components used are SMD and vary slightly but are as true to the schematics as possible.

Issue :
The design powers on with one switch-puls that looks fairly ok and similar to TNY290 datasheet
- After first switch pulse, it then enters into some kind of fault conditions for ~30uS and tries with another start pulse and repeat this pattern.

This start-pulse @30uSec is enough to keep low-voltage rails up with ~10k loads. Larger loads and the rails collapses and the TNY enters 2.5sek start pattern.... like a short has happened.
There is a nice ringing between each start pulse of ~500kHz. Where does that derive from? Is it a resonance of VR1 / R3 / D5 and the trafo?

Things that I have been trying are :
- Removal of RC-snubber, only having zener-diode snubber. No major changes.
- Changing VR1 from SMCJ130 to SMCJ200 with no other change than peak voltage and power dissipation.
- Removal of EN/UV resistors to VRail without any results.
- Changing the BP/M Capacitor from 100nF, 1uF, 10uF without any result.

I can not determine what kind of fault-condition it is in or if it relate to layout issues.
My best guess is that the trafo do not match somehow, but it was done to attached schematics.

Any suggestions ?

/Michael

回應

Submitted by MFog on 03/04/2020

More info :

I have not been zooming out for the wider picture. There is more going on.

A wider time-line shows that the TNY is switching. In 5mS interval thou..

A closer look shows that at first the switching is with 130kHz (8uSec), but after some time it slows to the 30uSec switching.

A even closer look shows the first initial switch that looks OK although the VOR seem to collapse quickly. I would have liked to see the VOR extend a bit more...

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Submitted by MFog on 03/05/2020

Found it!
Some smuck routed the opto's input to the output of the 15V snubber diode => very noisy feedback.
It was routed as the red connections.
Routing it as the blue, everything works fine

Thank you for you patience. :-)

/Michael

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Routing_of_opto_input.PNG 53.3 KB
Submitted by PI-Lupin the Third on 03/05/2020

Hi Mfog,

Glad that your circuit works fine now. Please let us know if you still have further question on this.

Thanks and Regards,

PI-Lupin the Third

Submitted by anurag lokhande on 08/21/2021

Hi PI,

I have TNY290PG board designed. OUTPUT 12V 2A. 

But circuit works fine till 12V/700 mA.

Above 700mA it goes to hiccup mode. Output tries to build 12V but it couldn't. 

A circuit as application note of TNY290 -  

Reference Design Report for a 20 W Standby

Power Supply Using TinySwitchTM-4

TNY290PG

Any suggestion to check on circuit or layout. 

Submitted by PI-Chloe on 08/24/2021

Hi 

Good day!

Please provide send schematic, bom, PCB, and PIexpert computation so that we can help you.

If you waveform, please send it. 

Thanks 

Regards 

Patrick 

Hi Patrick,

Attached sch. The changed is the feedback resistor to get 12V (R6=1000 ohm, R7=250 ohm) and transformer redesigned for 12V 2.4A

Obseravtions:

1. Cirucit works at VIN AC 230V for load 12V, 120mA, 

2. Cirucit works at VIN AC 160V for load 12V, 700mA

I am using variac to increase the input voltage gradually, it works fine for both above condition, beyond mentioned load, it goes to hiccup mode. 

 

 

 

Attachment 大小
schematic 164.48 KB
Submitted by PI-Chloe on 08/26/2021

Hi 

Good day! 

Please send me the transformer turns ratio 

Please also send me the reference PIexpert computation. 

Thanks 

Regards 

 

PI-CHLOE 

Hi,

Please see transformer details

Np 44 Turns
Ns 8 Turns
Nbias 10 Turns
Lprimax 198 uH

 

N87 core, EE25

 

Please also send me the reference PIexpert computation. --> I have not performed.

 

Please see below phenomenon observed for circuit

Input AC Input AC Output
Vin (V) I (A) Vout (V)  R load (Ohm) Iout (A) W (Watt)
234 0.001 12.58 38.12121 0.33 4.1514
142 0.03 12.58 38.12121 0.33 4.1514
62 0.1 12.58 38.12121 0.33 4.1514
142 0.1 12.58 22 0.571818 7.193473
120 0.02 12.58 44.6 0.282063 3.54835
120 0.1 12.58 22.3 0.564126 7.0967
55 0.28 12.58 16 0.78625 9.891025
220 0.001 12.58 31 0.33 4.1514
230 0.001 12.58 31 0.3 3.774

Case 1: if I increase the input voltage, SMPS goes to hiccup for 0.33A current.

OR 

if I increase the load current, SMPS goes to hiccup for more than 0.33A current.

 

Thanks, 

Anurag

Submitted by PI-Hiro on 08/31/2021

Hello Anurag,

I tried to replicate your design in PI XLS and have found that with the current transformer design, core saturation is very likely to happen. Also, the maximum primary inductance that you have provided is quite low which may limit the energy delivered to the output of the power supply.

Below is the suggested transformer design using PI XLS:

Primary Winding Turns: 61

Secondary Winding Turns: 7

Bias Winding Turns: 13

Lpri: 1187 uH

I will also attach the PI XLS design for your reference.

You can also create your own design by logging in here PI Expert Online (power.com). Designing with PI XLS will give you information on possible warnings on the design to make adjustments before building the power supply. You can start a new design or use the values from the attached file to tweak some other variables in the design. 

As for the feedback resistors that you have used, we recommend using higher valued resistors (around kΩ range) so as to not act as additional load to the power supply especially at low loading conditions. For your design a possible setup would be R6 = 10 kΩ and R7 = 2.7 kΩ. 

Thank you.

Regards,

PI-Hiro

 

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TinySwitch-4 Design1.pixls 58 KB
Submitted by anurag lokhande on 09/13/2021

Hi,

Thank you for your input.

We tried various primary turns and 100 turns worked out.

We are trying to find our why this calculation differs when N87 core data used. 

We are facing an output voltage drop from 12.15V to 9V when SMPS loaded.

Thank you.

Regards,

Anurag

 

 

Submitted by PI-Hiro on 09/14/2021

Hello Anurag,

May I ask for the transformer turns ratio and primary inductance you have measured?

Also, have you used PI Expert or PI XLS? Can you send the reference design?

Have you changed other components on the schematic aside from the feedback resistors?

Thank you.

Regards,

PI-Hiro

Submitted by anurag lokhande on 01/16/2022

HI Pi,

Thank you for your inputs.

Due to some other issue. We could not come to you.

 

First point 1-->

But what is happening with designed transformer, with N87 core, EE25, primary turns = 120, secondary turns = 16, we get the output of 12V (We don't know the primary inductance)

Here we have a hand wounded transformer. it works for 230V input voltage, if input voltage changed to 160V, output voltage gets ripple of ~ 2 volts.

What can be the issue here?

Little noise is coming, how to reduce?

 

Second point 2--> is that, 

We got the transformer N87 core, EE25, primary turns = 120, secondary turns = 16 Lpri = 1100 uH, But it is not working at 230V input voltage, getting output high ripple. 

 

Third point 3--> how to measure Lpri with minimum setup?

 

Fourth point 4--> How much we can rely on PI XLS? We are new to these converters. Is there try and error method applied to PI XLS values?

Fith point 5--> Which core to use, according to power rating?

Sixth point6--> I am unable to download your attached PI LXS file. how to download?

 

Regards,

Anurag

 

 

 

 

 

Submitted by PI-Lupin the Third on 01/18/2022

Hi Anurag,

Good day!

Thank you for reaching out to us through this page. If may I request, can you please create first another new post for this inquiry? If you think that this thread is still related to this present inquiry, then you may include the link of this thread in your new post. I will wait for your post.

Regards,

PI-Lupin the Third