{"id":5955,"date":"2013-01-26T19:33:36","date_gmt":"2013-01-27T03:33:36","guid":{"rendered":"http:\/\/rustybolt.info\/wordpress\/?p=5955"},"modified":"2013-11-01T21:15:04","modified_gmt":"2013-11-02T04:15:04","slug":"2013-01-26-dc-dc-converter-1-5v-to-9v","status":"publish","type":"post","link":"https:\/\/rustybolt.info\/wordpress\/?p=5955","title":{"rendered":"2013-01-26 DC-DC Converter 1.5V To 9V"},"content":{"rendered":"

\"\"<\/a>I’ve been trying to get a stable 5 milliamps of current from this circuit, which is a Supercharged Joule Thief with the LED replaced with a rectifier, filter capacitor and zener shunt regulator.\u00a0 I’m getting about 9V with no load, but when I put a 2.2k load resistor on I get 8.5V which is drawing about 3.8 milliamps.\u00a0 I think 4 or 5 mA would be enough to run the DMM.\u00a0 The total current through the ZD1 is about 7 milliamps no load, so if the voltage drop doesn’t cause the DMM to complain, then this circuit might be able to fulfill its job of replacing the 9V battery.\u00a0 One other thing: it should have a bypass capacitor across the battery – 220 uF or more.<\/p>\n

The circuit is not efficient overall because the output is shunt regulated.\u00a0 The Zener diodes just waste the excess that isn’t being used.\u00a0 But the inverter “Joule Thief” part of the circuit is efficient because it’s a Supercharged Joule Thief,\u00a0 This keeps the total current drawn from the battery down to 75 milliamps.\u00a0 If it was a conventional JT, the current would be over 100 mA.\u00a0 Since the DMM is used only intermittently, I figure that the single AA cell should last more than a dozen hours, which is weeks even in my extreme case of using the DMM every day.\u00a0 I could have used two AA rechargeable cells, which would be about 2.5V, and just keep trickle charging them when they’re not in use,\u00a0 I should experiment with another one that is optimized for 2.5V.<\/p>\n

\"\"<\/a>I built a circuit in April, 2007 which used two transistors to drive the output.\u00a0 This lightened the current load for each transistor.\u00a0 The two push-pull transistors balanced the DC in the core and the center tapped output winding had two diodes for full wave rectification.\u00a0 I don’t remember whether or not the feedback regulated the output well or not.\u00a0 The blog I wrote about it went away along with that information when watsonseblog was removed.<\/p>\n

I think there could be a few improvements.\u00a0 There should he a bypass capacitor from the center tap of the feedback (bottom) winding to ground.\u00a0 The 47 uF capacitor could be larger, 220 uF or more.\u00a0 The BC338 should be changed to BC337-25 to give a bit more balance to the two transistors.\u00a0 The 8.2k and 1k resistors should be higher, maybe 22k and 2.7k, to minimize wasted power.\u00a0 It might be a good idea to change the 2.7k to a 2.2k and 1k pot to allow adjustment of the output voltage.<\/p>\n","protected":false},"excerpt":{"rendered":"

I’ve been trying to get a stable 5 milliamps of current from this circuit, which is a Supercharged Joule Thief with the LED replaced with a rectifier, filter capacitor and zener shunt regulator.\u00a0 I’m getting about 9V with no load, but when I put a 2.2k load resistor on I get 8.5V which is drawing <\/p>\n

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