AN2983 datasheet(7/32 Pages) STMICROELECTRONICS

7 / 32 page

AN2983

Circuit description

Doc ID 15679 Rev 1

7/32

Other than the power and ground connections being exchanged, there are no differences

between the two configurations; the behavior and dimensioning of the inverse buck are the

same as that of the standard buck. Refer to application note AN2928(a) for a detailed

description and design rules. The following are a reminder of the fundamental applicable

equations.

Inductor current variation (charging period)

Equation 1

Inductor current variation (discharging period)

Equation 2

The circuit works in continuous conduction mode, then in steady-state the current variations

during ton and toff are the same (in module) and equivalent to the ripple current I_rip.

Ripple current

Equation 3

Duty cycle

Equation 4

Additionally, the average current of the LED can be expressed as:

Figure 4.

Standard buck converter

Figure 5.

Inverse buck converter

See Chapter 5: References on page 30.

ton

VLed

Vin

ton

∗

⎥⎦

⎤

⎢⎣

⎡

−

toff

VLed

toff

∗

⎥⎦

⎤

⎢⎣

⎡

toff

ton

rip

⎥⎦

⎤

⎢⎣

⎡

⎥⎦

⎤

⎢⎣

⎡

Vin

VLed

ton

AN2983 Arkusz danych(PDF) 7 Page - STMicroelectronics

AN2983 Arkusz danych(HTML) 7 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

Arkusz danych Pobierz

Link URL