Topologies Discussions - Step up or down with isolation

[Bjtpower]

Dear Friends

I am new For this forum and Power Electronics Passionate.

I Have some doubts for the Magnetics.

Kindly suggest me Which Topology is good for the Buck Purpose & Boost Purpose in Isolation

Like
1) High Voltage to Low Voltage Conversion With Isolation (Isolated topologies)
2) Low Voltage to High Voltage Conversion with Isolation.

I read Microchip AN1114 Where They Clearely mentioned WIth power & Voltage Terms.

Kindly Suggest Good Articles for the Knowledge Enhancements.


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Better Questions expects Better n Simple Answers..

 

[BradtheRad]

When you want isolation, the reliable method is a transformer. This can step up or down. It is common to use a fast switching frequency, which allows use of a small, lightweight transformer.

To maintain isolation of regulating circuitry, an optocoupler is a handy method.

 

[treez]

depends on your power level, but full bridge can do step up or step down. also 2 transistor forward, etc.

 

[Bjtpower]

I read somewhere where application note mentioned:
1) If you are input is higher than output then only Flyback/2switch Forward converter is possible.
2) If your input is lower than Output you can use Push-pull topology.

I was doing with the help of Push pull design when input was 360-480V & output was 48 volt for Telecom.
at the end of Transformer Design, my TUF was exceeding the Limit.it was coming 1.46
normally it should be 0.3-0.4 in ranges.

 

[Bjtpower]

When you want isolation, the reliable method is a transformer. This can step up or down. It is common to use a fast switching frequency, which allows use of a small, lightweight transformer.

To maintain isolation of regulating circuitry, an optocoupler is a handy method.

One gentleman asked me Question "Why isolation is necessary & I coudnt answer the same"
Can you please tell me why isolation is so Important as it degrades the efficiency of Project.
Kindly help

 

[smijesh]

Normally isolation required when input and output voltage difference is more than 50V

Advantage of isolation are given below
1. Isolation will prevent shock hazards, For example if we make a 5V power supply from 230V with resistor divider method it will work but, we shock if we touch the ground of 5V.
2. Isolation will help prevent ground loops it will help to reduce interference
3. In isolated circuit dangerous primary high voltages won't pass to secondary, even in the case of component failure in secondary
4. Isolation is recommended in line voltage because line voltage having interference, surge etc it will reduce the life of electronic circuit
5. Isolation is must to getting safety regulatory approvals