TL494: How can start-up resistor and aux winding be used together?

Enes AKTAS

Part Number: TL494
Other Parts Discussed in Thread: TL431

Hello,

I will design with analog ICs for the first time. I do not know how to connect the starting resistor and aux winding to the IC.
Is there a reference, tutorial document for this? I am waiting for your suggestions.

over 1 year ago

0 Hong Huang over 1 year ago

TI__Guru 74115 points

Hi,

What is your converter circuit? Can you provide your converter circuit so I can help to add how to connect AUX and startup resistor on to your circuit?

0 Enes AKTAS over 1 year ago in reply to Hong Huang

Prodigy 60 points

Hi,

I will make a half-bridge converter. 230Vac input. 12Vdc output. I will use TL494 pwm ic.

0 Hong Huang over 1 year ago in reply to Enes AKTAS

TI__Guru 74115 points

Hi,

See the below. Connect VDD1 to TL494 Vcc.

0 Enes AKTAS over 1 year ago in reply to Hong Huang

Prodigy 60 points

Is that right?

0 Hong Huang over 1 year ago in reply to Enes AKTAS

TI__Guru 74115 points

Hi,

Yes for connection on the AUX. The half bridge not correct. See my circuit for half bridge, the transformer one end needs to connect the center of two half bridge capacitors..

0 Enes AKTAS over 1 year ago in reply to Hong Huang

Prodigy 60 points

To tell you the truth I don't know how I should place the capacitors. Can you show me in the photo I sent?

0 Hong Huang over 1 year ago in reply to Enes AKTAS

TI__Guru 74115 points

Hi,

Look at my circuit sent to you, transformer one end to the middle of the two transistors, the other end to the center of the two capacitors.

I suggest you to search for a half-bridge converter design on the internet.

0 Enes AKTAS over 1 year ago in reply to Hong Huang

Prodigy 60 points

I arranged the capacitors in this way. In this case, can I not use the other input capacitors?

Also, why do you control the aux voltage with a transistor structure in the photo you sent?

0 Hong Huang over 1 year ago in reply to Enes AKTAS

TI__Guru 74115 points

Hi,

What do you mean "the other capacitors"?

The transistor forms an LDO type to regulate the AUX voltage to make bias. Without this transistor the VCC from AUX is not regulated which usually not acceptable. But in your case, it depends on your design to be ok from your check.