jdbakker
Well-known member
Hi all,
I need a low-noise DC-DC converter for my portable HDD recorder, to get +/-12V, +/-24V and P48 for the analog bits. Some searching has turned up the LT1533, a push-pull converter with a shaped drive waveform to reduce switching noise to low levels.
So now I need a transformer. This is my first transformer-based switcher, and the data sheet and app note both refer to a non-documented Coiltronics-part (with no hints on finding a replacement other than 'ask the manufacturer').
I would prefer to use a ready-made part available from Digi-Key or the like. What I'm looking for is a transformer with a 1:2 ratio, with center taps on both primary and secondary. Power would be ~20W, to be on the safe side. Switching frequency is either 100kHz or 200kHz (depending on whether I choose to support 192k sampling. The best I have found so far are the JW Miller PM600/610/620 series and the TDK PCA series, which all consist of six-winding transformers (1:1:1:1:1:1). However, all these only specify winding inductance, how do I translate that to switching frequency ?
Plan B would be to wind my own. Any suggestions for (toroid) cores for 20W/200kHz ? Could I just use an existing toroid or common-mode choke and add a secondary winding ?
I don't care about RoHS, since this is DIY use only. I do care about EOL status, since I'd like others to be able to re-build the design. I also care about affordable shipping to Europe (which nowadays sadly excludes Mouser).
Any suggestions ?
JDB.
I need a low-noise DC-DC converter for my portable HDD recorder, to get +/-12V, +/-24V and P48 for the analog bits. Some searching has turned up the LT1533, a push-pull converter with a shaped drive waveform to reduce switching noise to low levels.
So now I need a transformer. This is my first transformer-based switcher, and the data sheet and app note both refer to a non-documented Coiltronics-part (with no hints on finding a replacement other than 'ask the manufacturer').
I would prefer to use a ready-made part available from Digi-Key or the like. What I'm looking for is a transformer with a 1:2 ratio, with center taps on both primary and secondary. Power would be ~20W, to be on the safe side. Switching frequency is either 100kHz or 200kHz (depending on whether I choose to support 192k sampling. The best I have found so far are the JW Miller PM600/610/620 series and the TDK PCA series, which all consist of six-winding transformers (1:1:1:1:1:1). However, all these only specify winding inductance, how do I translate that to switching frequency ?
Plan B would be to wind my own. Any suggestions for (toroid) cores for 20W/200kHz ? Could I just use an existing toroid or common-mode choke and add a secondary winding ?
I don't care about RoHS, since this is DIY use only. I do care about EOL status, since I'd like others to be able to re-build the design. I also care about affordable shipping to Europe (which nowadays sadly excludes Mouser).
Any suggestions ?
JDB.