While the controller operates in the inverter-mode it repeatedly monitors the voltage at its pin4 (BATT SENSE), pin7 (OVER
LOAD sense) and pin2 (AC MAIN sense).
the voltage at pin4 rise above 2.6V the controller would take no notice
of it and may be seen escaping to supplementary
sensing-mode, but as soon as the voltage here drops to around 2.5V the
controller stage would prohibit its functioning at this point, switching
OFF the inverter-mode such that the low battery LED turns ON and
prompting the buzzer to
Over load protection is a mandatory
functionality implemented in most inverter systems. Up here, in order to cut-of the
inverter in the event the load goes beyond the safe load
specifications, the battery current is first detected across the negative line (i.e the
voltage drop across the fuse and negative path of the low side
MOSFET bank) and this greatly reduced voltage (in mV) is proportionately
intensified by the comparator U5 (composing of pins12,13 1nd 14) (make
reference to circuit diagram).
This amplified voltage output from pin14
of comparator (U5) is rigged as inverting amplifier and applied to pin7
of the microcontroller.
The software compares the
voltage with the reference, which is for
this particular pin is 2V. Quite as talked over previously the
controller senses the voltages in this pin besides operating the system
in the inverter-mode, every time the load current augments the voltage
this pin builds up, whenever the voltage on pin7 of the controller IC is
the process shuts off the inverter and switches to overload mode,
shutting off the inverter, turning ON the overload LED and causing the
buzzer to beep,
which after 9-beeps prompts the inverter to switched-ON again,
voltage at pin7 for a second time, suppose in case the controller
pin7 voltage to be below 2V, it then operates the inverter on normal
mode, other wise
it disconnects the inverter yet again, and this process is known as the
Like in this
article we articulated beforehand that when in inverter-mode, the controller reads the
voltage at its pin4 (for Low-batt), pin7 (for overload) and pin2 for
AC main voltage status. We comprehend that the system may be functioning in twin
mode (a) UPS mode,(b) inverter mode.
So before inspecting the pin2
voltage of PIC the routine before anything else confirms at what mode
the unit may be working by sensing the high/lo logic at pin16 of the PIC.
Inverter to mains changeover (INV-MODE):
particular mode as soon as the AC main voltage is detected to be in the
vicinity of 140V AC,
the changeover action can be seen implemented, this voltage threshold is
pre-settable by the user, implies that in cases where the pin2 voltage
is above 0.9V, the
controller IC may shut off the inverter and switch to mains-on mode,
where the system examines the pin2 voltage to test the AC mains failure
and maintain the charging process, which in this article we will be
explaining later on.
Inverter to Battery changeover (UPS-MODE):
this setting each time the AC main voltage is in the vicinity of 190V AC the changeover
may be seen enforcing to battery mode, this voltage threshold is also software pre-setteble, meaning when ever the
pin2 volage is above 1.22V the controller may be expected to switch ON the inverter and
switched to battery routine wherein the system inspects the pin2 voltage
to verifies the AC mains absence and operates the charging schedule
which we would be discussing further down in the article.