Datasheet SCM1212A (Mornsun) - 7

Figure 14 Flow Diagram of Start-up Mode Operation Mode If the output of converter has no short circuit,the voltage of output capacitor,in start-up mode,wil gradual y increase during the continuously circular charging.When the breakover voltage of MOS transistor is less than or equal to the set value,the converter wil turn into operation mode.The flow diagram is shown in Figure 15,that is,determine that the breakover voltage of MOS transistor is less than or equal to the set value→ drive the selected MOS transistor with ful drive→ check the switch-on voltage of MOS transistors→ judge whether the voltages (VVD1,VVD2) are more than the set value. If the breakover voltage of MOS transistor is more than the set value,then the system goes into time-counting cycle of start-up mode,otherwise,the system turns back to the step “drive the selected MOS transistor with ful drive”,and the above processes are repeated,which is the normal operation of the converter after the product is started.In the operation,MOS transistor is ful y driven,that is the MOS transistor is operating in switching status and the on resistance is low,resulting in low energy consumption and high efficiency. Figure 15 Flow Diagram of Operation Mode Short Mode If the output of the converter has short circuit,it wil detect in start-up mode that the breakover voltage of MOS transistor is more than the set value,then the accumulated over-voltage time wil definitely exceed TD_OSP (100ms,typ.).At this time,SCM1212A wil stop to drive the MOS transistor and begin to count the time of stopping driving MOS transistor.When the time is counted to TSLEEP (800ms,typ.),the product resumes operation and turns into start-up mode. The flow diagram of short mode is shown as Figure 16: determine the duration of over-voltage exceeding TD_OSP → stop driving and begin to count time (sleep mode) → finish counting time → turn back to start-up mode.We can see that if the converter is always in output short circuit status,it wil operate in the short mode and start-up mode alternately. Figure 16 Flow Diagram of Short Mode 2019.12.13-A/3 Page 7 of 11 MORNSUN Guangzhou Science & Technology Co.,Ltd.reserves the copyright and right of final interpretation Document Outline Mornsun Guangzhou Science & Technology Co.,Ltd.