Datasheet SCM1212A (Mornsun) - 5

Parameter Measurement Information Figure 7 Schematic Diagram of Test Circuit for Function Curve Figure 8 Circuit Sequence Diagram Figure 9 Schematic Diagram of Test Circuit for Switch Characteristics Features Description (1) Push-pul Converter As shown in Figure 10 and Figure 11,the push-pul converter is a transformer with center tap,which can achieve the transmission of energy from the primary winding to secondary winding. Figure 10 Switching Period 1 of Push-pul Converter Figure 11 Switching Period 2 of Push-pul Converter The drive waveform of drains VD1 and VD2 of two MOSFETs Q1 and Q2 are shown in Figure 8.Two MOS transistors are on alternatively and the times of the breakover periods of two transistors are equal,and there is a short period tBBM between the two breakover periods that the two power transistors are not on.That is to say,the drive levels of two MOS transistors are quasi complementary in time sequence,that is the other transistor is off when one transistor is on,but there is a short period of dead time during the switch to prevent the backward current flow when two the transistors are not on simultaneously.As shown in red highlighted parts in Figure 10,when Q1 is on,input voltage VIN drives a current which arrives at the reference ground through the lower half of primary winding of transformer and Q1,and at the same time,the induced electromotive force of side winding charges output capacitor through diode D1.Similarly,as shown in Figure 11,when Q2 is on,the induced electromotive force charges output capacitor through diode D2.As continuously repeating the above process,the secondary winding of power converter obtain the needed power supply. (2) Magnetization of Magnetic Core Figure 12 is the ideal magnetization curve of push-pul converter,and the vertical axis represents magnetic flux density B and the horizontal axis represents magnetic field intensity H.When Q1 is on,the magnetic flow is pushed to point A’ from point A.Similarly,when Q2 is on,the magnetic flow is then pul ed back to point A from point A’.The magnetic flux density B is proportional to the product of voltage of primary winding VLP and breakover time of MOS transistors tON,which can be described in the fol owing formula: B≈VLp×tON 2019.12.13-A/3 Page 5 of 11 MORNSUN Guangzhou Science & Technology Co.,Ltd.reserves the copyright and right of final interpretation Document Outline Mornsun Guangzhou Science & Technology Co.,Ltd.