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18-265V AC-DC Wide Input Power Supply with 3 Isolated Outputs using TNYIII Family Switch

Posted by: majinbuu8 on

Hi,

I am looking for a power supply design with a wide Input Supply Range. The Input supply must vary from 18VAC/DC to 265VAC/DC. Also, I require 3 Isolated Outputs from the Flyback Design. I have tried using the PI Expert Tool as well as the PIXL tool, however, I was  unable to come up with the proper solution.

 

1. Can you help me with this design? The specfications are as follow:

Vin: 18VAC/DC to 265VAC/DC

Vout1: 5V-0.7A Controlled/Regulated

Vout2: 26V-0.1A Floating

Vout3: 26V-0.1A Floating

Power: 8.7W

Transformer Core: EE13 or EE16 Horizontal 10 PIN.

 

2. If not, then kindly send me all the possible formulae and documentation related to designing the required power supply. I want every possible construction and design details including that of transformer. I have referred the DI-152 Design Idea. However, I was unable to come up with the exact solution for my design requirement.

 

3. If not, then please send me the design steps involved in the designing of the above specifications.

 

4. I have a doubt in the design. If I implement the constant current source circuit on the TNYIII Bypass pin and design the transfomer from the PI Expert software with Vin selected as 85-265VAC, will I be able to get the exact same results as expected for 18-265VAC/DC input supply?

 

Note: I am attaching the power supply design of PI Expert with 85-265VAC Input schematics.

Hope to hear from you soon.

Regards,

Omkar Gawde.

 

Files

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Power Supply Schematics 144.91 KB

Comments

Submitted by PI-LeoDavinci on 04/18/2017

Hi Omkar,

 

Thank you very much for using Power Integration's TNYIII. Let us check first your schematic and design requirements. By the way what is the application for such design? Thanks.

 

 

Submitted by majinbuu8 on 05/14/2017

In reply to by PI-LeoDavinci

Hi PI-LeoDavinci,

Application: Signal Isolators Industrial Deisgn witn universal Power Input. 

This is the reason behind two different Isolated 24V Windings.

I have developed the design for the same, however, I am having trouble with TNY278 heating beyond expectations.

There seemed to be no heating issues in other power supply designs.

I am attaching the schematic for the same alongwith the various diodes and componenets used. 

Hope, you can help me out with my query and give a solution to the same.

Also, Please do guide me if I am making any mistakes in the design. 

My prioirty so far is to resolve the heating issues of the design since they seem to affect other components in the product.

Submitted by PI-LeoDavinci on 05/21/2017

In reply to by majinbuu8

Hi,

The schematic looks fine however as you've said there is a heating issue. We are not familiar with your transformer design and may we request if you have some waveform measurements of the component heating up (TNY278)? We woudl like to verify if the drain voltage is still within the limits and also to see if the snubber is working properly. Thank you very much.

Submitted by majinbuu8 on 05/31/2017

In reply to by PI-LeoDavinci

Hi,

 

I do not have the proper equipment to provide you the waveform charts. However, I can provide you with the PI document which had been modified as per my requirement. 

 

I hope you can help me out with only this much information. The components used are as per the schematic provided earlier. 

Regards,

Omkar.

Submitted by PI-LeoDavinci on 06/09/2017

Hi Omkar,

 

Based on your schematic, design specs, and some of your provided information here are my thoughts:

1. TNY278 is enough to handle your design since it is rated at 10W since your design is rated 8.7W. However depending on your efficiency target the power loss might cause your TNY278 to heat too much and therefore may cause excessive heating and eventually component failure.

2. Since your design is three output the transformer construction will therefore play a big role in the overall efficiency of the power supply. Depending on your construction, the leakage inductance must be checked carefully and must be kept at the minimum. Tight coupling of each winding must be observed (primary, secondary) in order to lessen parasitic capacitances and large leakage inductance. Excessive leakage inductance will cause too much voltage spike in your primary thus requiring heavy suppression through snubber circuit. Improper snubber circuit design will damage your primary Mosfet, in this case TNY278.

3. Key Design Points

Verify that the maximum drain voltage is <650 V at high line and maximum overload condition. Adjust the values of snubber circuit as necessary. However, avoid making the clamp circuit too dissipative

Use a slow blocking diode for the snubber and a low value resistor (say 100 Ω series resistor). Use only a glass-passivated (GP) diode type to ensure a low reverse recovery time. If unavailable, a fastdiode such as FR107 may be used instead. These diode selections recycle some of the clamp energy and improve effi ciency at no load.

 

 

4. I noticed that your minimum input voltage is 18VAC, is this correct? because TNY278 is NOT catered for this low input voltage. It can only cater as low as 85VAC. please verify.

 

5. For the PCB design, the drain pin must be kept to a required creepage/clearance requirement. I suggest you keep at least 2.5mm spacing for high voltage tracks.

 

Hope this helps. 

Submitted by majinbuu8 on 06/09/2017

In reply to by PI-LeoDavinci

Hi,

Thankyou for your valuable response. I will look into the matter myself and revert back to you.

 

Yes, I want my circuit to work from 18VAC.

 

As per your query, I want the circuit to work from 18VAC to around 265VACUltra Wide Supply Range. This specifications have been decided based on the PI Application Note DI-152. I hope the same applies for TNY278. 

This way I can keep a single power supply design for DC as well as AC Applications.

I have provided the schematic in the same terms. Kindly check for any possible errors in the design and revert back is possible.

 

Regards,

Omkar Gawde.

Submitted by PI-LeoDavinci on 06/15/2017

In reply to by majinbuu8

Hi Omkar,

You are welcome. Kindly give us an update whatever the status may be after checking. As for the TNY278, let me verify if this can be applicable as per DI-152 document since this was designed using TNY 280. For now please check the items that was suggested for verifications and hope  it may deem helpful for your design.