In order to avoid the power of the peak of the peak current damage switch tube, KA7552 built a soft start circuit. Just boot, pce2 pressure drop for the ov. PICl internal 10 mu a constant current source to charge the PGE2, PICl the pin voltage for charging and slow rise, so PICl fifth pin output PWM drive pulse becomes wider, to prevent the switch to start an instant damage. PTl, PR7, PL7, PD2, PC7 and other components of the main winding of the main winding are composed of PR6, which is composed of the network to prevent the damage caused by the spike voltage. The source current PFETl is feedback resistor PR8 converted into voltage and feedback to 3 PICl feet. When the PFETl due to the temperature rise caused by the source current is increased, when the feedback voltage exceeds pic1 protection threshold voltage +0.24V, PICl the output pulse shut off rapidly, the field effect tube not to overheat damage.

Online measurement of the power board components were not significantly damaged, but the purchase is less than KA7552. In the maintenance of a Japanese 56T5 NANAO type used in the power supply, the power supply circuit used in power IC FA5311. In reading, it is found that the parameters and application of FA531l and KA7552 are almost identical. The power supply board then from a normal OKI 5330 printer remove a FA5311 loaded with 6N60 substitution, K793. The DVD machine power supply panel no-load energized, power output voltage is normal, then the power supply board into the machine, electric machine back to normal.