CONTROLLER BOARD (Pro901/Pro902/903)

2. MAIN CONTROL PCB ASSEMBLIES (CNTL)
These assemblies are the control center of UPS. It is composed of three major circuits as following.
(1) Regulation & control
(2) Protection
(3) Signaling

 2-1 REGULATION & CONTROL SUB-SYSTEM :
This portion can be seen as brain of the UPS. It provides the control pulses to the switching elements which deliver power to the output.

- The sub-system also regulates the output to ensure that the UPS is delivering constant   
   AC voltage to the loads.

- The inverter signal is sensed directly by resistor division. It is compared with a  
   reference  signal from sine wave generator. The difference of these two signals (error 
   signal) alter the pulse widths of PWM signals which control the duty cycles of switching 
   elements to regulate the output voltage within  specification.

- In order to avoid unwanted surge current at the transfer of bypass relay, the bypass 
  signal  activates the tracking circuit. It matches the inverter voltage with the line 
  voltage by having the amplitude of the reference signal following the variation of line 
  voltage.
 
- When the main is applied and the switch is turned on, a 10-second timer is triggered. 
  The bypass relay stays at bypass position in this time period. At the end of this period, 
  the bypass signal is removed and the relay transfers to inverter output.

2-2 PROTECTION SUB-SYSTEM :
The UPS provides the following protection circuits:
1. Overload protection
The load detector senses the load current. i.e. the inverter current, and sends the signal by two paths. The UPS will go to failure mode if overload condition happened. The panel will indicate the fault condition.

There are two kinds of protection in our UPS:
a. Overload Protection : The UPS collects the continuous overload signals through CPU 
    switch the output relay.
     * In Line Mode : 
     (a.1) If the output load is higher than 103% and lower than 110% of rated load (VA, or  
      Wattage) the UPS will warning, after 5 minutes go to fault mode. 
     (a.2) If the output load is between 110% and 130% of rated load (VA, or Wattage) the 
      UPS will warning, after 10seconds go to fault mode. 
     (a.3) If the output load is higher than 130% of rated load, the UPS will go to fault  
      mode after 1second.
 
      * In Battery Mode : 
     (a.3) If the output load is higher than 110% and lower than 120% of rated load (VA, or 
     Wattage) the UPS will warning, after 0.5minutes go to fault mode. 
     (a.4) If the output load is between 120% and 130% of rated load (VA, or Wattage) the 
     UPS will warning, after 10seconds go to fault mode.
     (a.5) If the output load is higher than 130% of rated load, the UPS will go to fault 
     mode after 1second.

b. Cycle by Cycle Current Limit : 

    When output loads sink a high surge current for a short time,a high inverter current is   

    detected and the inverter switches, i.e. the MOSFET's, are turned off pulse by pulse 

    to protect themselves from thermal runaway. The output relay stays at inverter output 

    position unless a continuous overload is detected or an abnormal inverter operation  

    occurs.

2. Battery over or under shut down :
    Upon the battery voltage declines to battery-under/over level, the UPS will warn and 
    the LCD willdisplay the fault code, and then shut down. In case of the battery voltage 
    is high voltage, the UPS will warn and the LCD will display the fault code.

3. Inverter output abnormal protection :
    The inverter failure signal shuts down the inverter immediately, makes the buzzer a 
    continuous alarm, and the LCD displays the fault code.

 4. Over temperature protection
     The thermal switch detects the temperature of PSDR heat sink. The thermal switch is  
     electrically connected to the CPU. An opened thermal switch is thought as 
     temperature failure by the UPS. The LCD will display the fault code.
 
5. Bus over/under protection
    To protect any BUS over/under condition. The LCD will display the fault code.

2-3 Signaling Sub-System :
     When the AC line is unable to supply, the batteries release energy inside to supply the 
     inverter immediately. At the same time, the buzzer beeps every 4 seconds. 
     Upon the batteries are discharged to battery-low level, the battery-low signal is 
     activated and the buzzer beeps every 1 second. Remote shutdown signal is enabled 
     only when the line fails.