My first SMPS design was a multiple output flyback. This was in 1976, when there were no PWM controllers. So I used a 556 (1\/2 osc -30 kHz, and 1\/2 PWM generator) plus used a 3904 NPN where the VBE was the reference and also provided gain for the error amp function. I hap-hazardly wound the windings on a 25 mm torroid. It ranglike a tank circuit. I quickly abandoned the transformer and after a year, and many hours on the bench, I had a production-grad SMPS.
\nSince it went into a private aircraft weather reader system, I needed an exterier SMPS which was a buck converter. I used an LM105 linear regulator with positive feedback to make it oscillate (one of nationals ap notes). It worked, but I soon learned that the electrolytic capacitors lost all of their capacitance at -25 deg C. It later worked with military-grade capacitors. <\/p>\n
I had small hills of dead MOSFETs and the directly attached controllers. When the first power MOSFETs emerged in 1979, I blew-up so many that I almost wrote them off. They had some real issues with D-S voltage overstress. They have come a long way since.<\/p>\n
As far as very wide range flyback converter, please dig-up AN1327 on the ONSEMI website. This describes a control strategy (fixed off-time, variable on-time) and the transformer design.
\nThe processor to that was a 3W flyback that drove 3 floating gate drive circuits and had an input range of 85 VAC to 576 VAC. It was for a 3 phase industrial motor drive. The toughest area was the transformer. To meet the isolation requirements of the UL, and IEC, it would have required a very large core, and bobbin plus a lot of tape. The PCB had the dimensions of 50 mm x 50 mm and 9 mm thick A magnetics designer named Jeff Brown from Cramerco.com is now my magnetics God. He designed me a custom core and bobbin that was 10 mm high on basically an EF15 sized core. The 3 piece bobbin met all of the spacing requirements without tape. The customer was expecting a 2 – 3 tier product offering for the different voltage ranges, but instead could offer only one. They were thrilled. <\/p>\n
Can be done, watch your breakdown voltages, spacings and RMS currents. I found that around 17 -20 watts is about the practical limit for an EF40 core before the transformer RMS currents get too high.<\/p>\n","protected":false},"excerpt":{"rendered":"
My first SMPS design was a multiple output flyback. This was in 1976, when there were no PWM controllers. So I used a 556 (1\/2 osc -30 kHz, and 1\/2 PWM generator) plus used a 3904 NPN where the VBE was the reference and also provided gain for the error amp function. I hap-hazardly wound the windings on a 25 mm torroid. It ranglike a tank circuit. I quickly abandoned the transformer and after a year, and many hours on the bench, I had a production-grad SMPS.
\nSince it went into a private aircraft weather reader system, I needed an exterier SMPS which was a buck converter. I used an LM105 linear regulator with positive feedback to make it oscillate (one of nationals ap notes). It worked, but I soon learned that the electrolytic capacitors lost all of their capacitance at -25 deg C. It later worked with military-grade capacitors. <\/p>\n
I had small hills of dead MOSFETs and the directly attached controllers. When the first power MOSFETs emerged in 1979, I blew-up so many that I almost wrote them off. They had some real issues with D-S voltage overstress. They have come a long way since.<\/p>\n
As far as very wide range flyback converter, please dig-up AN1327 on the ONSEMI website. This describes a control strategy (fixed off-time, variable on-time) and the transformer design.
\nThe processor to that was a 3W flyback that drove 3 floating gate drive circuits and had an input range of 85 VAC to 576 VAC. It was for a 3 phase industrial motor drive. The toughest area was the transformer. To meet the isolation requirements of the UL, and IEC, it would have required a very large core, and bobbin plus a lot of tape. The PCB had the dimensions of 50 mm x 50 mm and 9 mm thick A magnetics designer named Jeff Brown from Cramerco.com is now my magnetics God. He designed me a custom core and bobbin that was 10 mm high on basically an EF15 sized core. The 3 piece bobbin met all of the spacing requirements without tape. The customer was expecting a 2 – 3 tier product offering for the different voltage ranges, but instead could offer only one. They were thrilled. <\/p>\n
Can be done, watch your breakdown voltages, spacings and RMS currents. I found that around 17 -20 watts is about the practical limit for an EF40 core before the transformer RMS currents get too high.<\/p>\n","protected":false},"author":0,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[67],"tags":[],"class_list":["post-14020","post","type-post","status-publish","format-standard","hentry","category-iacdrive_blog"],"_links":{"self":[{"href":"http:\/\/iacdrive.com\/index.php?rest_route=\/wp\/v2\/posts\/14020","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/iacdrive.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/iacdrive.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"replies":[{"embeddable":true,"href":"http:\/\/iacdrive.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=14020"}],"version-history":[{"count":0,"href":"http:\/\/iacdrive.com\/index.php?rest_route=\/wp\/v2\/posts\/14020\/revisions"}],"wp:attachment":[{"href":"http:\/\/iacdrive.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=14020"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/iacdrive.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=14020"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/iacdrive.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=14020"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}