SP433 Datasheet, PDF (5/10 Pages) SYNC POWER Crop. – Constant Voltage and Constant Current Controller

SP433
Constant Voltage and Constant Current Controller
APPLICATION NOTE
In the above application, SP433 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:
Risense X I-limit = 0.7V (typical)
Where I-limit is the desired current limit. The selection of Risense should consider the power loss through Risense. It
is calculated as:
P-limit = 0.7 X I-limit
Whether AC input is at High Line or Low Line, SP433 can provide the same current protection. It has the fuse
function at the output.
2009/03/16 Ver.1
Page 5