voltage regulator for USB power

Thread Starter

yuhao

Joined Dec 28, 2015
3
Hi everyone, I am trying to build a power supply from a set of resonator circuit. The circuit can provide 8W for a 43 ohms load at 19V. I want to charge my phone (5V, 1A, 5W) with it so I use a voltage regulator (LT1375). But when I connect it to my circuit, the voltage output become very low (50 mV).

Any advice would be very helpful. Below is the resonator circuit to supply power (replace the source in voltage regulator circuit) and the voltage regulator circuit (replace the load in the resonator circuit).
 

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wayneh

Joined Sep 9, 2010
16,124
Hi everyone, I am trying to build a power supply from a set of resonator circuit. The circuit can provide 8W for a 43 ohms load at 19V.
Are you saying that the circuit was tested and shown to be able to perform?
I want to charge my phone (5V, 1A, 5W) with it so I use a voltage regulator (LT1375). But when I connect it to my circuit, the voltage output become very low (50 mV).
This sounds like an error in wiring. Perhaps a short or the pin out was wrong. With a fuse in place, you could try a know good power supply such as a car battery.
 

Thread Starter

yuhao

Joined Dec 28, 2015
3
Thank you for the reply!

It is simulated in LTspice, and show to provide 8W.

The regulator works well in LTspice when connected to a ideal source, but not to my resonantor circuit.
 

sailorjoe

Joined Jun 4, 2013
361
The resonator can put out 8 W at 19 V. That's about 400 ma.
The load is set to draw an amp, right?
That may be your mismatch. Try decreasing the load current and see what happens.
 

Thread Starter

yuhao

Joined Dec 28, 2015
3
The resonator can put out 8 W at 19 V. That's about 400 ma.
The load is set to draw an amp, right?
That may be your mismatch. Try decreasing the load current and see what happens.
Thanks for the reply.
1) It does not work with even lower current such as 250 ma (e.g. change load to 2.5 ohms)
2) There is a input of 8 W 19V, and I want a output of 5 W 5V, I thought there must be some way of using buck converter to achieve this ?
 

sailorjoe

Joined Jun 4, 2013
361
Just to be clear, we're talking about an actual circuit, right, not a simulator?

If so, you want to try *decreasing* the load current by *increasing* the load resistance. Don't drop the load resistor to 2.5 ohms, raise it to 50 ohms, and see what happens.
 

ronv

Joined Nov 12, 2008
3,770
Thanks for the reply.
1) It does not work with even lower current such as 250 ma (e.g. change load to 2.5 ohms)
2) There is a input of 8 W 19V, and I want a output of 5 W 5V, I thought there must be some way of using buck converter to achieve this ?
To get lower current you would need a larger resistor - maybe 10 ohms.
To ask again. Is it the actual circuit that does not work or is it the simulation that does not work.
If it is the circuit. What is the voltage going into the regulator when it fails.
Things it might be:
1- The coupling between the coils may not be as good as you have shown.
2- The actual components may not be resonant at 205Khz because of tolerances.
 

wayneh

Joined Sep 9, 2010
16,124
It is simulated in LTspice, and show to provide 8W.

The regulator works well in LTspice when connected to a ideal source, but not to my resonantor circuit.
OK, so this is all in simulation so far. Both circuits appear to work separately in simulation but fail when connected to each other.

What does the voltage out of the resonator look like when the load is placed on it? It has an AC component? What are the peak voltages, high and low?
 
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