STANSON TECHNOLOGY

ST8433 (Pb-Free)

Constant Voltage and Constant Current Controller

120 Bentley Square, Mountain View, Ca 94040 USA

WWW.STANSONTECH.COM

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.

ST8433 2009 V1

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