Here is my first test of modified bench supply providing 600Vdc from existing 250V transformer via a voltage multiplier circuit, gyrator filter and passive MOSFET regulator. This circuit was built with components I had around and supply provides 0-600V with less than 5mV ripple thanks to the 53dB attenuation. Maximum current is 100mA continuous but passive regulator has a 200mA limiter built in.
Above is a classic voltage-doubler configuration. I had a 250V secondary, so had to add one of this to get HT to 600V at least. Resistor equalisers have been added to leverage whatever electrolytic I had around and could use here. The raw supply should provide a low ripple of about 1.3Vpp at full load (100mA).
A classic gyrator to simulate an inductor in an LC stage. Attenuation of this stage and the passive regulator which is configured as a capacitor multiplier can provide at least 53dB @ 100Hz. This will bring down the ripple to less than 5mV!
Finally the passive regulator. It has a current limiter set to 200mA. M2 will dissipate large amounts of heat. Just do the maths: dropping circa 600V to whatever voltage is set as the output by the 1M pot. This will be bolted to the chassis C shaped aluminium frame. Probably needs a bigger heatsink as could melt down when delivering large currents at low output voltage. This is a situation we want to avoid. Output will have a slow fuse of around 100mA, but the circuit has a 200mA current protection to avoid killing the MOSFET whilst charging a capacitor,etc.
Hi,
I’m very interested by your gyrator, but I don’t know how to modify the specifications.
Can you help me (or explain?), to have a 7H-150ohms gyrator.
Thank you very much !
Théophile Poisson
PS : Sorry for my bad english (I’m french)…..
Hi Theophile,
I recommend you to implement the power supply gyrator described in this later post:
It does have the additional protection in case of short-circuit. You can build it in SPICE and simulate to get see the equivalent LC response. The gyrator behaves like an L at low frequency with L = C6xR3xR4 = 560uF x 150k x 10 ohms = 840H. Equivalent series resistance is about R3*(1+R5/R6) = 10 ohms * 2 = 20 ohms. You will need to add external series resistance to damp the LC response. R3 is there to protect the maximum MOSFET current.
You can see that if you want a gyrator to simulate response of an 10H inductor then you can change R5=R6=10K and C6=100uF with R3=10ohms.
Remember the gyrator is not an inductor, it doesn’t store any energy!
cheers
Ale
Thank you very much Ale !
I gonna try….
Théophile