LED Emergency Lighting driver

HM9928

Operation

1、AC main line detection

     

HM9928  is  an ASIC for LED emergency lighting. The output PIN EN switch is turned on if the resistance

  

between  VL  and  VN  is  less  than  the  threshold  resistance,  while  there  is  no  AC  power  signal.   If  the  AC 

power  is  detected  or  the  resistance  between  VL  and  VN  is  larger than  the threshold,  the  EN  PIN  is  high 

impedance state.    

AC input

EN

NOTE

AC power

High impedance

AC open

High impedance

AC short

High level(battery voltage)

Resistance is less than threshold

2、Battery Management

HM9928  integrates battery protection including to protect lithium ion/polymer battery from damage or

degrading the lifetime due to overcharge, over discharge, battery reverse protection and overcurrent for 

one‐cell lithium‐ion/polymer battery.  

 

Output current

In order to set the LED current, a ballast resister could be added between EN PIN and LED load. The internal 

MOSFET resistance is 200mohm. 

.