# High range input voltage isolated topology

#### kobi209

Joined May 28, 2017
8
Hi All,
I need to design a DC/DC isolated converter, with a high range of input DC voltage: 50-950V and output 12Vdc, ~30W.
The first topology I thought about was Flyback, which is cheap and easy, however has some drawbacks.
Have somebody had the chance to design high voltage range power supply?
I'd love to hear your suggestions.
Thanks.

#### Irving

Joined Jan 30, 2016
820
950v is exceptionally high! Why so big a range?

Its going to be difficult to find a solution to that breadth of range. You'll need some form of pre-regulator stage. I'd look at a resonant LLC converter, which can handle a wider input range than Flyback. Even so, probably not all in one go.

#### ronsimpson

Joined Oct 7, 2019
726
Part of the problem is you need high voltage silicon and high current silicon.
1000V x 30mA = 30 watts AND 50V x 600mA = 30 watts
non isolated simple buck wide range I remember this part only good to 1000V. Good read if you are thinking about preregulator.

Power Integrations has a application note I can't find now for wide range. Most of their parts are only good to 850 to 1000V but there a application note on going to 1500V to 2kv. Will look 8 hours later. I did a design this way years ago. Flyback type. If you go looking for it "power supply for power metering".

#### DickCappels

Joined Aug 21, 2008
6,463
The pre-regulator would be a buck/boost (the term is frequently misused. By this I mean the converter can be used in either mode and adjusts its operation as needed to achieve the desired regulation). Otherwise, you can (?) switch ranges, by driving different windings or taps.

Sanyo has a pretty good collection of medium current 1500 volt transistors. The lower current dynamic focus transistors are included here because when working with voltages in that range (over 900V) they might come in very handy.

#### andrewmm

Joined Feb 25, 2011
403
Hi All,
I need to design a DC/DC isolated converter, with a high range of input DC voltage: 50-950V and output 12Vdc, ~30W.
The first topology I thought about was Flyback, which is cheap and easy, however has some drawbacks.
Have somebody had the chance to design high voltage range power supply?
I'd love to hear your suggestions.
Thanks.

Whats your experience in Power supply designs, especially at high voltages ?

#### SiCEngineer

Joined May 22, 2019
217
Do you have any other requirements, such as transient response performance, does it need to be fixed frequency, etc. As much as you can say will help with suggestions more.

#### kobi209

Joined May 28, 2017
8
Hi All,
I need to design a DC/DC isolated converter, with a high range of input DC voltage: 50-950V and output 12Vdc, ~30W.
The first topology I thought about was Flyback, which is cheap and easy, however has some drawbacks.
Have somebody had the chance to design high voltage range power supply?
I'd love to hear your suggestions.
Thanks.
950v is exceptionally high! Why so big a range?

Its going to be difficult to find a solution to that breadth of range. You'll need some form of pre-regulator stage. I'd look at a resonant LLC converter, which can handle a wider input range than Flyback. Even so, probably not all in one go.
The big range is due to the solar panel string voltage range can be implemented. This is anauxiliary psu for dc/ac 3-ph inverter. The nominal inverter input voltage is 750V, and this is the 30w working point of the dc/dc. 950V is for the largest string, and the low voltages are for a case of off grid mode, when the system is expected to wake up with minimal panels voltage (i.e at early morning).

#### Irving

Joined Jan 30, 2016
820
Would be a damn sight simpler, cheaper and easier to have a 12v 30Ah LiFe battery pack charged off one of the AC phases. It'll physically last >15y under these conditions, and will deliver 30W for 12 hours on a single charge!

#### kobi209

Joined May 28, 2017
8
Whats your experience in Power supply designs, especially at high voltages ?
I'm working as a power engineer 8 years, RnD of DC/AC solar inverters and all its additional circuits.