Kikusui PFX2500 Series, Operation Manual

Page: 126 / 144

126
PFX2512
C
Characteristics of Digital CC/CV Control
The constant current (CC)/constant voltage (CV) control on the PFX2512 is performed digitally.
This section describes the characteristics and operation principle of digital CC/CV control so that
you can efficiently conduct evaluation tests.
● Digital CC/CV control is not susceptible to the performance of the connected DC power
supplies or electronic loads and constantly enables high-accuracy CC/CV control.
●
System adjustments based on the combination of DC power supplies and electronic loads
are not necessary.
●
Difference in performance in the measurement of charge capacity and discharge capacity
is less likely to occur, and accurate charge/discharge efficiency measurement is possible.
Explanation of operation
As an example, the operation principle will be briefly explained using digital CC control during
charging.
In constant current charging, when a digital CC value is sent to the PID control section, and the
operation starts, the PID control section changes the level of current control on the DC power
supplies. The charge current is measured using an high-accuracy shunt, and a digital current
measurement is obtained through a 24-bit A/D converter. The PID control section compares the
digital CC value to the digital current measurement and calculates the current control level to make
them equal. This sequence of operations is performed a 1 000 times per second.
If a DUT other than a battery is connected, the CC/CV control may not work properly.
If there is no load (not connected) or if a battery with an abnormally high internal impedance is
connected, CV mode may not work properly.
Even in CV or CP mode, the connected DC power supplies and electronic loads run in CC mode. This
is because external devices are always running as current sources, so this is the correct behavior.
indicate functions internal to the PFX2512
High accuracy
Current
measurement
CC setting
Calculates the control level
every ms so that the ammeter
reading is equal to the CC
setting. (PID control section)
AD conversion
(24 bitADC)
DUT
(Battery)
DC power supply (PWR800L)
Current control level
(CC reference)
Digital
Current measurement
Digital
CC setting
Analog value
High accuracy
shunt
Electronic load (PLZ1004W)
Load switch
(Power MOSFET)
Charge current
Discharge current
Digital CC control explanatory diagram