Lyker

You are just chopping off to many digits on the current. Your current is 4.432mA not just 4.4mA So.... 4.432mA * R(2k2) = 9.75V 4.4mA * R(2k2) = 9.68V

An echo or a parrot? ???

I fully appreciate that the idea of the circuit is to dump the energy from the capacitor into the coil, not from R1 directly. My point is this; the current sourced from R1 and the 1kV supply used to recharge the capacitor is enough to keep the SCR latched. For example the holding current for a BT152 may be as low as 16mA. If we take the values in Riccardo

Alex Tsekenis Depends on how much current is available from the 1kV source, granted it

I would check the holding current of the SCR you use, it needs to be greater than 1A in your circuit. Also, limit the gate pulse current with a resistor. That resistor will also have an affect on the holding current.

I have just read a data sheet for a solar battery charger which claims to be a PWM type, however the switching frequency was quoted as being only 100Hz. Would I be incorrect if I assumed that this is simply pulse width modulating a series transistor (between the panel and the battery) to keep the battery voltage constant, but that the current consists of pulses from zero to whatever the panel and battery combination turns out to be. I find it hard to except that true switch-mode PSU (buck converter for example) with an output current of 10A can switch at such a low frequency. Many thanks.

Plumber Maybe you could try this current limiting circuit. You will have 30V until the current increases to 5mA when the TL431 will shunt the gate voltage of the FET. The output voltage will then drop to a value determined by the load. There will be a small voltage drop across the sense resistor as the current increases. Hope this is of some help.

Are you just in need of an upper current limit of 4mA? It