Good Will Instrument PSS-2005 User Manual - page 16
PSS-3203/2005 PROGRAMMABLE POWER SUPPLY
USER MANUAL
22
The operation in C.C. Mode is similar to that in C.V. Mode. The
MPU will send 2100 counts, 2.1A output current, to DAC, output
through analog switch and Sample Hold circuit, the voltage now is at
around -3.276V (-1.56mVx2100=-3.276V). Then, compare this voltage
with the real output voltage which is retrieved by the current sense
circuit. As the entire circuit is a close loop, therefore, the retrieved
voltage value will be followed with the reference voltage of Sample Hold.
Besides, the Comparator output terminal will output a relative voltage
value to control the whole output circuit through a driver circuit
? and
generate the required output voltage. The current sense circuit for
detecting the voltage value from current sense resistor is mainly
composed by differential amplifier TL071. The multiple of the
differential amplifier is A=-R355/R356= -22.0K/1.91K=-11.518, the
voltage on the both sides of current sense resistor is
-3.276/-11.518=0.285V, so the output current is basis on
Iout=(0.285/R374)*2=(0.285/0.3)*2=1.9A, and 2.1A making multiple
operand to get a real output current by using the software.
The Displayed Value of Voltage and Current
The voltage/current sense circuit retrieves a voltage value which will
be sent to Comparator through Analog Switch, and joined with the output
voltage of DAC in dichotomy approaching method to get the same
voltage as the real output value of the instrument.
PSS-3203/2005 PROGRAMMABLE POWER SUPPLY
USER MANUAL
23