Figure 4 shows the schematic for the CV/CI module; it
does not include the display board.
I have shown the 7.5V input as a separate input. There
will be more on this later. The schematic consists of two
separate sections: the upper section, which is a switching
regulator utilizing an XL4005; and the lower section, which
is a current monitor and set point for the current limiting.
This module uses a conventional switching regulator IC
with a voltage adjust feedback resistor R2 to set the output
voltage point. There are two FETs inside the XL4005 that
switch at up to a 300 kHz rate, and drive L1 and C4 to
establish the output voltage.
The lower section uses R3 to convert the output
current to a voltage. The digital ammeter in the display
shows the output current which is proportional to the
voltage across R3. The LM358 compares the voltage drop
across R3 to a set point established by variable resistor R6.
R6 derives a precision reference voltage from zeners D2
and D3. When the voltage drop across R3 exceeds the set
point voltage established by R6, the output of the LM358 at
28 May 2014
; FIGURE 4. CV/CI
; FIGURE 5.