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Unclear circuit element (Shunt Voltage Reference Diode) in eDesignSuite

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EDokm
Associate II

‎2024-03-07 09:31 AM

I am trying to simulate a 220VAC/24VDC 240W converter. According to eDesignSuite BOM, there is a Shunt Voltage Reference Diode which is called as SHUNT (Reference 1.24V). 

But when i checked the schematic diagram, i cannot find this diode. 

Am i missing something? Can anybody explain this Shunt Voltage Reference Diode which is called as SHUNT? 

My project is given in the attachment.

Thanks.

 

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Peter BENSCH
ST Employee

‎2024-03-07 10:13 AM - edited ‎2024-03-07 10:14 AM

Sorry that the BOM is somewhat misleading here. For electronics engineers who have been in the business for a while, this is a familiar term and refers to a so-called shunt regulator. In the schematic of your report, this is VR (far right, below Vout).

Such shunt or parallel regulators work slightly similar (but much more precisely and with a narrower tolerance) to a zener, which also produces a (reasonably) stable voltage as long as the current drawn is significantly lower than its cross-current.

In your example, the TS3431AILT compares the voltage at the voltage divider with its internal reference voltage of 1.24V and allows a current to flow through the optocoupler OPTO that is proportional to the deviation of the output voltage. If the output voltage is too high, the COMP pin is increasingly pulled to GND, which realises the regulation.

Hope that answers your question?

Regards
/Peter

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.

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Peter BENSCH
ST Employee

‎2024-03-07 10:13 AM - edited ‎2024-03-07 10:14 AM

Sorry that the BOM is somewhat misleading here. For electronics engineers who have been in the business for a while, this is a familiar term and refers to a so-called shunt regulator. In the schematic of your report, this is VR (far right, below Vout).

Such shunt or parallel regulators work slightly similar (but much more precisely and with a narrower tolerance) to a zener, which also produces a (reasonably) stable voltage as long as the current drawn is significantly lower than its cross-current.

In your example, the TS3431AILT compares the voltage at the voltage divider with its internal reference voltage of 1.24V and allows a current to flow through the optocoupler OPTO that is proportional to the deviation of the output voltage. If the output voltage is too high, the COMP pin is increasingly pulled to GND, which realises the regulation.

Hope that answers your question?

Regards
/Peter

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.
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