| ??? 04/12/06 02:19 Read: times |
#114127 - Step-up, step-down Responding to: ???'s previous message |
Suresh said:
and, what you have said have made me think like this.
I require 24V at 1A = 24VA So when 12V rectified o/p is stepped up the same 24VA power would be drawn, leading to increase in rating of the Transformer. Did i got that right? Roughly spoken: If you need 1A at 24V and would use a step-up scheme basing on 12V, then from the 12V 2A would be drawn. In both cases 24VA. Suresh said:
Secondly, the LM2675 option seems to be a nice one when planning to step down.
But i thnk it would also dissipate the same power as that a 7805 do, since it has to power the micro continuously (referring my project) and there would be no switching 'OFF' of 2675 in between. Roughly spoken: The LM2675 step-down switcher contains an ultra low loss switch (very low ohmic when "on"), which is either "on" or "off" and which is opened and closed about 200,000 times a second. The duty cycle is varied in order to regulate the output voltage. If the switch is "off", no relevant power is consumed, because no current is flowing. If the switch is "on", negligible power is dissipated in the switch, because voltage drop across switch is negligible. By using such a scheme you can achieve efficiencies of more than 95%! Kai |
| Topic | Author | Date |
| step up voltage regulator | 01/01/70 00:00 | |
| 12V rectified output? | 01/01/70 00:00 | |
| additional Transformer occupies space | 01/01/70 00:00 | |
| 18V Center Tap Transformer? | 01/01/70 00:00 | |
| size ? | 01/01/70 00:00 | |
| Mistake in analysis | 01/01/70 00:00 | |
| why two? | 01/01/70 00:00 | |
| Of course! | 01/01/70 00:00 | |
| easier | 01/01/70 00:00 | |
| You are righ Kai. I didnt analyse this w | 01/01/70 00:00 | |
| nope, that is why it is called a switche | 01/01/70 00:00 | |
| Step-up, step-down | 01/01/70 00:00 | |
| ON/OFF(active low) pin? | 01/01/70 00:00 | |
| Shutdown pin | 01/01/70 00:00 | |
Thanks. | 01/01/70 00:00 | |
| Try this simple circuit. It might work | 01/01/70 00:00 | |
| LM2577 | 01/01/70 00:00 | |
| expensive is relative | 01/01/70 00:00 | |
| Charge pump | 01/01/70 00:00 | |
| Thank you all | 01/01/70 00:00 | |
| Two are needed! | 01/01/70 00:00 |