You can calculate inductance of coil using eq. L=U*dt/di. Here is schematic for control board. I have built this schematic and adjusted frequency fo be around 10Hz. On time - Ron*Ct, off time Roff*Ct.
Jak měřit indukčnost za podmínek blízkých provozu v pulzních zdrojích?
Thanks for the equation for calculating the inductance. If I see the need I may have to whip up a Visual Basic program for calculating some of this stuff. You will have to explain the pic or schematic for the control board you linked. I clicked on the second link too but the web page is all in Czechoslovakia language. Maybe I can find a converter on Google and cut and paste.
Found one to translate:
Inductors and properties of nuclei I
How to measure inductance
Most published methods for measuring inductance are based on the use of a sinusoidal signal. In pulse sources, however, we encounter a PWM signal, which is a rectangular waveform. Therefore, it would be very appropriate to measure the inductance under conditions as similar as possible to the operating conditions. I tested a very interesting method that we can use both to measure inductance and to measure the properties of unknown cores originating from various scrap, all under conditions corresponding to operation in pulse sources.
Description
The presented method is based on measuring the change of the magnetizing current Im in time. It is based on a well-known relationship
Im = (Ub * t) / L [1]
after adjustment
L = (Ub * t) / Im [2]
It is clear from the graphical representation that after the supply voltage Ub is applied for time t, the magnetizing current Im begins to flow through the choke. While the voltage Ub and the time t are constant, the magnetizing current gradually increases with the length of the time pulse. Thus, in order to obtain the inductance L according to [2], we will measure the change in the magnetizing current Im flowing through the choke at time t. With this method, we will also later look for the usability parameters of the unknown core.
Connection
The picture shows an asymmetric PWM generator with a variable opening time from 2us to 90us.
The circuit consists of a half-bridge driver IR2151, where only the lower half is used. The time constant for the closed transistor is set to Ct + Roff, the opening time is defined by Ct + Ron + Pt. Pt is a multi-turn potentiometer with which we change the opening time of the transistor Q. The choke in the drain of the transistor Q is charged while the transistor is switched on. During the switch-off, it is discharged via the fast Doff diode. Both magnetizing and demagnetizing current pass through the sensing resistor 0.11R. Every 100mV on this resistor indicates 1A of magnetizing current. We connect an oscilloscope to the OSC terminals on the sensing resistor. Oscilloscope ground on - and probe on +.
Buildlist
Doff - UF4004
L - measured choke
Q - SUP70N06 Ron - 10R
Pt - 10k (multiturn)
Rof - 100k Ct - 10nF
I will describe the exact measurement procedure in the next part.