AN3392 datasheet(10/57 Pages) STMICROELECTRONICS

Part #	AN3392

Description	The SPV1020 is a monolithic DC-DC boost converter designed

PDF	57 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

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10 / 57 page

Application information

AN3392

10/57

Doc ID 018749 Rev 1

Equation 1

where “D” is the duty cycle [Ton/(Ton+Toff)] of the rectangular waveform driving the switching

element.

Boost converters can work in two main modes:

●

Continuous mode (CM);

●

Discontinuous mode (DCM);

depending on whether the current on the inductor becomes zero (DCM), or not (CM), within

the switching period.

Figure 7.

Step-up converter in discontinuous mode

Even though a boost converter may work both in CM and DCM modes, efficiency is normally

higher when it works in CM, if the switching frequency is constant.

Inductance and switching frequency (Fsw) determine the working mode. In order to have the

system working in CM, the following rule should be used:

Equation 2

Worst case for L in the above formula is D = 50%.

out

-----------

–

-------------

Fs w

))

(

Vo ut

−

∗

AN3392 Datasheet(PDF) 10 Page - STMicroelectronics