AN3095 datasheet(10/55 Pages) STMICROELECTRONICS

Part #	AN3095

Description	The STEVAL-ISV002V2 demonstration board is the same

PDF	55 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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10 / 55 page

DC-DC converter

AN3095

10/55

Doc ID 16555 Rev 3

Figure 6.

Current flow in mode 1

This mode ends when leakage inductor current reaches zero at t=t1.

●

Mode 2, interval (t1-t2):

When the leakage inductor current reaches zero, D1 and D2 turn-off with soft switching, as

the current naturally reaches zero. After t=t1 M6 is still on, primary current changes polarity

and flows through M1 and M4. On the secondary side the transformer is shorted through M6

and D2, as shown in Figure 7. Inductor current may be written as:

Equation 3

Figure 7.

Current flow in mode 2

●

Mode 3, interval (t2-t3):

At t=t2 M6 is turned off and M5 is turned on under ZVS. A positive voltage equal to +Vbus is

applied on transformer secondary winding. Leakage inductor current is given by:

Equation 4

The current path in the circuit is drawn in Figure 8.

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(

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(

−

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AN3095 Datasheet(PDF) 10 Page - STMicroelectronics