AD8452 Demo Board Discharge mode is not working?

1. Change the part of Aux power supply from AD8452 demo Board schematic.

2.[???] Set the demo software ,config  the half-bridge as boost mode(Discharge mode);

the gate of mosfet cannot detect PWM wave(Charge mode,wave can be detected & AD8452 MODE pin can change level (0v,5v)by Mode Switch).

 

3.[???]the demo board cannot control discharge output voltage(Boost mode,output voltage is open loop) ,how to improve circuit to achieve it.