{"id":95295,"date":"2017-01-31T07:00:00","date_gmt":"2017-01-31T22:00:00","guid":{"rendered":"https:\/\/blogs.msdn.microsoft.com\/oldnewthing\/?p=95295"},"modified":"2019-03-13T01:05:19","modified_gmt":"2019-03-13T08:05:19","slug":"20170131-00","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/oldnewthing\/20170131-00\/?p=95295","title":{"rendered":"Why does my Surface power brick keep blinking on and off?"},"content":{"rendered":"

If you try to charge your phone and your Surface from the same power brick, keep a close eye on the charger: See if the charging light is blinking. <\/p>\n

Here’s the deal. There’s an issue with some phones in the way they negotiate current with Surface power brick. The two get into a current negotiation fight. <\/p>\n

    \n
  1. The power brick detects that there is a phone plugged in.<\/li>\n
  2. The power brick says, “Hey, I can give you 1.2mA, is that okay?” (Note: All numbers in this story are made up.)<\/li>\n
  3. The phone says, “I’m cool with that.”<\/li>\n
  4. The power brick says, “Okay, heres 1.2mA. Enjoy.”<\/li>\n
  5. The phone gets confused and draws 1.3mA instead of 1.2mA.<\/li>\n
  6. The power brick shuts down due to overcurrent. The charging light goes off.<\/li>\n
  7. Your Surface is now running on battery.<\/li>\n
  8. The phone says, “Okay, well, easy come easy go.” It stops drawing power.<\/li>\n
  9. The power brick says, “Whew, that overcurrent situation is over. I sense no load. The user must have unplugged the curling iron or whatever it was. Let me turn myself back on.” The charging light goes on.<\/li>\n
  10. The Surface is now running on AC power.<\/li>\n
  11. Go to step 1.<\/li>\n<\/ol>\n

    The result of this issue is that the PC is constantly switching between battery and AC, and the phone doesn’t charge. Basically, everybody loses. <\/p>\n

    The Lumia folks issued a firmware update to address this issue, but if you’re using some other phone model, then who knows when\/if it’ll get fixed. But at least you know what’s going on. <\/p>\n","protected":false},"excerpt":{"rendered":"

    Power negotiations break down.<\/p>\n","protected":false},"author":1069,"featured_media":111744,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1],"tags":[104],"class_list":["post-95295","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-oldnewthing","tag-tipssupport"],"acf":[],"blog_post_summary":"

    Power negotiations break down.<\/p>\n","_links":{"self":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/95295","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/users\/1069"}],"replies":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/comments?post=95295"}],"version-history":[{"count":0,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/95295\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/media\/111744"}],"wp:attachment":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/media?parent=95295"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/categories?post=95295"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/tags?post=95295"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}