Synchronous MOSFET Driver not functioning when voltage already present

[techn0]

I have designed a circuit (module) based around this example. I have it working quite well for one exception.

I am trying to use this to charge and discharge a super capacitor bank. On Vout I have a 30 amp current monitoring IC that reads current in both directions so I can monitor and adjust the pwm input signal to maintain desired current flow. External to this module I have a PLC that monitors bank voltage and enables or disables the module based on bank voltage. My problem is that if the Capacitor bank has a previous voltage of about 1.5v or higher the NCP3420 continues to act disabled. I have tried playing around with the pwm and enable timings in code to no avail.

This module has a pic MCU that monitors current and voltage to control the pwm duty based on charge or discharge mode.

I have a feeling that inserting something to remove pin 7 from the circuit until it starts might be the key but I wanted to get some feed back before getting too creative. I think the gate driver prevents start up if voltage is present on the SW pin. Not sure. Datasheet is unclear to me.

 

[Baluncore]

I think the gate driver prevents start up if voltage is present on the SW pin. Not sure.

That IC is designed to supply a power output starting at zero volts.
Your first output when enabling the driver should be short pulses of output low. That must fully charge the flying capacitor between pins 1 and 7. Only then can output high be asserted.

I suspect you will need to hold pin 2, PWM low, while providing a series of short positive pulses to pin 3, _OD.

 

[techn0]

I played around with what you suggested with no luck.

I then did some testing with bringing the module voltage up from zero while not connected to the cap bank. I would get the module voltage similar to the cap bank and then connect them successfully. So now I have modified the circuit to monitor cap bank voltage and allow the module to precharge to the cap bank voltage and then connecting with a relay with they are within a quarter volt of each other so normal charging or discharging is possible from any previous bank voltage now.

All the logic is programmed into the MCU controlling everything.

I was hoping to avoid any relays in this design but I will socket them so they can be serviced.

Ordering new PCBs again.