PFA for the design using FAN-7392 to drive dual supply power with the dual load(battery) connected in series (+.........-+..........- ).
The microcontroller is PIC16F877A with separate Two PWM driving positive side and negative side MOSFET independently.
MCUs ground is -17 volt, not 0 of dual supply, to measure -ve volt as positive.
The issue is Q1 is not conducting now, what may be the reasons?
Q2 is working now.
2. MCUs can't measure -ve voltages how this is taken care of in the situation it needs.
Yes, I did not recognize the allowed voltage offset before.
But it's limited to abs. Max of 25V wrt low side supply.
Low side supply now is 15V, thus the lowest voltage is -10V.
--> with -17V is still can't work.
The recommended offset is +/-5V only, I guess just to compensate for ground bouncing in high power applications.
1. Low side supply needs common ground with Q2 emitter. This is required for correct Q2 gate voltage and operation of the bootstrap supply.
2. Supply voltage level is decided according to IGBT gate drive requirements.
3. Depending on the offset between Vcc and controller ground, you possibly need a level shifter for the input signal and a respective separate Vdd supply.
1. COM has to be connected to Q2 emitter.
If COM is -17volt (consider VSS=+17 and COM is -17 volt)or we can consider this as equivalent to single-ended supply 34 --0 volts?.
2.The IC allows only a limited voltage shift between Vss and COM.
Yes , VSS= 34 and COM =0 but as (+17 to -17).
The datasheet specifies a "VSS Logic supply offset voltage", minimal VCC - 25, maximal VCC + 0.3.
There are 3 voltages here
VDD ---VSS (5-0 volts) logic voltage from MCU
VCC --- COM(15-0volts) supply for MOSFET driver
(+17)----(-17) Driven voltage
1. Low side supply needs common ground with Q2 emitter. This is required for the correct Q2 gate voltage and operation of the bootstrap supply.
2. Supply voltage level is decided according to IGBT gate drive requirements.
3. Depending on the offset between Vcc and controller ground, you possibly need a level shifter for the input signal and a respective separate Vdd supply.
1. Low side supply needs common ground with Q2 emitter. This is required for the correct Q2 gate voltage and operation of the bootstrap supply.
Yes, common ground is there here its -17 volt (-volt we cannot consider here as we do not reference this volt to real GND ).
2. Supply voltage level is decided according to IGBT gate drive requirements.
yes, the VGS threshold is a minimum of 8 volts for proper conduction.
3. Depending on the offset between Vcc and controller ground, you possibly need a level shifter for the input signal and a respective separate Vdd supply.
This issue is not there now.
For reference, I have attached a simplified "Design1.jpg " image, this only I am trying to achieve.
I will post a detailed circuit in the upcoming days. Please help.