ST8433 (Pb-Free)
STANSON TECHNOLOGY
Constant Voltage and Constant Current Controller
APPLICATION CIRCUIT
APPLICATION NOTE
In the above application, ST8433 is used to provide an accurate control of voltage and
current. The voltage loop is controlled through an internal error amplifier, the resistor
bridge R1, R2 and the photo-coupler. The relation between Vout, R1, R2 and Vref is shown
in:
Vout = Vref x (1+R1/R2)
The current loop is controlled through an internal transistor, the sense resistor and the
photo-coupler. The control equation is:
Rsense x I-limit = 0.7V (typical)
Where I-limit is the desired current limit. The selection of Rsense should consider the
power loss through Rsense. It is calculated as:
P-limit = 0.7 x I-limit
Whether AC input is at High Line or Low Line, ST8433 can provide the same current
protection. It has the fuse function at the output.
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ST8433 2009 V1
STANSON [ STANSON TECHNOLOGY ]
