Timeline for Soft latching power switch
Current License: CC BY-SA 4.0
11 events
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| Sep 23, 2018 at 4:03 | comment | added | jonk | @oliver Understood. The leakage, using the 2-MOSFET approach, can achieve a small number of microamps of leakage. But not zero. I gathered your circuit isn't operating as hoped, though I admit I didn't know exactly why. So I offered something else. However, if you are happy with what you have -- it's working for you, with or without Jack's comments -- then I didn't really add anything. | |
| Sep 23, 2018 at 3:52 | comment | added | oliver | thanks again for your design. The reason I am using the improved original circuit from EEVBlog: with your solution at any time either Q1 or Q2 is ON imposing a constant power drain on the battery. By contrast my favorized circuit only consumes power when completely ON (apart from leakage currents and switching charges of course). But probably yours will help somebody with different requirements. | |
| Sep 21, 2018 at 21:07 | comment | added | jonk | @oliver Yes. It's one or the other, but not both. | |
| Sep 21, 2018 at 19:29 | comment | added | oliver | I see, so either (Q1=on, Q2=off) or (Q1=off, Q2=on), right? Probably I just misunderstood your sentence "that when the momentary switch is closed again that Q1 will be turned ON (as opposed to this time when C1 was mostly discharged and turned Q1 OFF.)". | |
| Sep 21, 2018 at 18:53 | comment | added | jonk | @oliver (I have to admit, after re-reading your question a few times, I'm still not entirely sure what's being asked. But maybe I do. I'm just not sure. So bear with me. If I answer the wrong question, it's just me not understanding you and nothing more.) When \$Q_2\$ is on, it keeps \$Q_1\$ off. When \$Q_1\$ is off, \$R_3\$ and \$R_2\$ supply the base current for \$Q_2\$. \$C_2\$ isn't terribly important then (though it does need to be charged a little to reach the \$V_\text{BE}\$ of \$Q_2\$.) | |
| Sep 21, 2018 at 18:44 | comment | added | oliver | thank you for the design and your detailed explanations. I have finally found the calmness to read through it. There is one thing that I don't understand: in the quiescent state you basically say "with Q1 on C2 is held close to ground", but after the first state change Q1 is also on. What should keep C2 from discharging via Q1 again and almost immediately turn Q2 off again - just like in the quiescent state? | |
| Sep 16, 2018 at 1:15 | history | edited | jonk | CC BY-SA 4.0 |
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| Sep 14, 2018 at 23:11 | history | edited | jonk | CC BY-SA 4.0 |
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| Sep 14, 2018 at 22:42 | history | edited | jonk | CC BY-SA 4.0 |
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| Sep 14, 2018 at 22:29 | history | edited | jonk | CC BY-SA 4.0 |
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| Sep 14, 2018 at 22:24 | history | answered | jonk | CC BY-SA 4.0 |