Capacitor Charger Circuit

Thread Starter

Mark34

Joined Sep 23, 2016
24
Ok, you modified the circuit, now it makes sense, do I need a simple diode or rectifying diode ? the post #20 circuit will charge the cap to 250V ?
 

MisterBill2

Joined Jan 23, 2018
11,646
The graph shows it charging to 3.6 volts. There is a limit because the cap can not charge above the breakdown voltage of the transistor. That is a rather serious limitation. It is also a big part of why a circuit with both windings as part of the driver is rather limited. A five terminal, or six terminal, transformer has much different capabilities.
And what is the motivation for not wanting a tapped primary circuit???
 

Papabravo

Joined Feb 24, 2006
18,161
Ok, you modified the circuit, now it makes sense, do I need a simple diode or rectifying diode ? the post #20 circuit will charge the cap to 250V ?
Those terms are rather imprecise because all diodes willl rectify. The major difference is the amount of forward voltage they require to conduct. A silicon diode will require 0.65 to 0.72 Volts when fully conducting, but the Schottky, being of a different constructionhas a lower forward voltage in the range of 0.2 to 0.4 Volts. This would seem to be a major benefit given the low value of your voltage source. At some point in the battery discharge cycle there won't be enough voltage to sustain the operation.
 

Thread Starter

Mark34

Joined Sep 23, 2016
24
It's simpler if you just draw me the circuit that's charging the cap to 250V post #5 and #20 seem close.
 
Last edited:

MisterBill2

Joined Jan 23, 2018
11,646
While the forward voltage drop of a diode does matter, the reverse breakdown voltage and the forward current capacity are the major and most important specifications most of the time.

The most recent circuit, shown in post #20, charges the capacitor to 3.6 volts, and can not charge beyond the breakdown voltage of the transistor. The requirement for Charging to 250 volts does not seem to be getting much attention, but probably it is not possible with the circuit as shown,
 

Papabravo

Joined Feb 24, 2006
18,161
It simpler if you just draw me the circuit that's charging the cap to 250V post #5 and #20 seem close.
I'm reluctant to say anything further based on the concept that charging a capacitor to 250 Volts seems like a less than prudent course of action. If the TS is bound and determined, he can do it on his own for which none of us need be responsible.
 

MisterBill2

Joined Jan 23, 2018
11,646
I'm reluctant to say anything further based on the concept that charging a capacitor to 250 Volts seems like a less than prudent course of action. If the TS is bound and determined, he can do it on his own for which none of us need be responsible.
SUCH FEAR!!
Charging a cap to some higher voltage for a flash system or a magnetic pulse system or to drive an acoustic sounder is totally reasonable. The world does not run on 3.3 volts DC!
Of course, a system to charge a car body to 10 KV to deter carjackers with guns would not be supported here, but that is very much different.
 

Papabravo

Joined Feb 24, 2006
18,161
SUCH FEAR!!
Charging a cap to some higher voltage for a flash system or a magnetic pulse system or to drive an acoustic sounder is totally reasonable. The world does not run on 3.3 volts DC!
Of course, a system to charge a car body to 10 KV to deter carjackers with guns would not be supported here, but that is very much different.
Not everybody has the good sense to take precautions.
 

Thread Starter

Mark34

Joined Sep 23, 2016
24
I worked with 400V capacitors for hundred hours on my first project, now I want to do the charging capacitor circuit myself and not buy it, but I guess this "Joule Thief" circuit with a 4 pin transformer can not get to 250V.
 
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