PV educator

Now using the datasheet of the above mentioned mofet Ig= (23nC x 100kHz)  = 0.0023
Therefore R_g = 18/0.0023 = 7826 ohm
According to the application note of this ic , following condition must be true .

R_G calculated from input side < R_g calculated from output side  

If this is not true then you must find some other optocoupler which can drive a larger current.

Fine tuning R_G 

Calculation of P_D= 16mA x 1.8 x 0.5 = 14.4mW

Calculation of Po(circuit)= Ic x (VCC-VEE) =
where I_c is the current supplied to the photo detector and typically it is 2mA and maximum 3 mA as provided in the application note.

Calculation of Po(switching) = Esw (RG,QG)xFsw
where E_sw (R_G,Q_G) is the per cycle power consumption when charging the mosfet and f_sw is the switching frequency (60 Hz in my case). The E_sw (R_G,Q_G) can be calculated based on the graph presented in application note. Based on 5.8 ohm R_G calculated above the E_sw is found to be 0.5uJ.

Calculation of P_O = I_c x (V_CC-V_EE) + E_sw (R_G,Q_G)xF_sw = 3mA x(18-0) + 0.5uJ x 60 = 54 mW

This P_O is less than the maximum power rating of this ic i.e 178 mW.

Switching loss per cycle ( click to zoom)

Therefore, based on the switching loss graph presented in the application note, the R_G should be between 6 ohm - 40 ohm.

During my Ph.D. work, it was a requirement to sense the dc current on the PV side and ac current on the grid side. To sense the current I used a hall effect current sensor LTS25NP. This hall effect sensor is a bit costly however, it is excellent in working and easy to setup. Figure 1 shows this sensor. This sensor has three pins on each side and three in the front side. The three pins of left and right side should be shorted together. The output is from the front side. It should be noted that there are three pins on the front side and an arrow symbol. Arrow symbol shows the flow of current, this means that the positive terminal of the wire should be wired in harmony with the arrow direction.

IR2111 is a half bridge driver that is extensively used in power electronics.  It is an eight pin ic that works only with half bridge configuration. It can not be used individually for low side or high side driver.  Here is the schematic that i designed during my term project.

4N26 and 4N37 are cheap optocoupler that are good for most of the power electronics applications. They are six pin ic with optical isolation. The output is inverted because the output transistor works as a switch. The frequency limit of this ic is explained in this post. The following is the working circuit of optocoupler 4N26 and 4N37.

The gate driver is essential in power electronics because of two basic reasons. First, at high frequency switching applications the switching time is less which means that in order to charge/discharge the mosfet capacitance fast, more current is required. The output current of most optocouplers is not enough to drive the mosfet properly. Secondly, most of the optocoupler output is limited to under 10 V which means that they can operate a mosfet near its threshold voltage, This results in high R_ds resulting in heating the mosfet.