t (s)

t (s)

L

i

'

D*Ts

Ts

D*Ts

Ts

L

V

IN

L

V

V

OUT

IN

L

V

V

OUT

IN

(a)

(b)

LM2622

SNVS068E – MAY 2000 – REVISED MARCH 2013

www.ti.com

INTRODUCTION TO COMPENSATION

(a) Inductor current

(b) Diode current

Figure 18.

The LM2622 is a current mode PWM boost converter. The signal flow of this control scheme has two feedback

loops, one that senses switch current and one that senses output voltage.

To keep a current programmed control converter stable above duty cycles of 50%, the inductor must meet

certain criteria. The inductor, along with input and output voltage, will determine the slope of the current through

the inductor (see Figure 18 (a)). If the slope of the inductor current is too great, the circuit will be unstable above

duty cycles of 50%. A 10µH inductor is recommended for most 600 kHz applications, while a 4.7µH inductor may

be used for most 1.25 MHz applications. If the duty cycle is approaching the maximum of 85%, it may be

necessary to increase the inductance by as much as 2X. See INDUCTOR AND DIODE SELECTION for more

detailed inductor sizing.

introduces a pole-zero pair according to the following equations:

10

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