AL1677

Document number: DS37526 Rev. 1 - 2

9 of 13

www.diodes.com

November 2015

© Diodes Incorporated

AL1677

5

_

R

V

I

REF

CS

Where,

R5 is the current sense resistor.

In no PF buck topology, the system operates at boundary conduct mode. The output current is:

peak

mean

o

I

I





2

1

_

Therefore, the current sense resistor R5 is determined:

mean

o

REF

CS

I

V

R

_

_

2

1

5





Inductance Selection (L1)

The AL1677 controls the system operating at boundary conduction mode, and the systems

’ operating frequency does not keep constant because

be calculated by:

min

_

_

_

2

5

)

2

(

1

f

V

V

V

R

V

V

L

rms

in

ref

cs

o

o

rms

in













Where,

According to the Faraday

’s Law of Induction, the winding number of the inductance can be calculated by:

5

1

1

_

1

R

B

A

V

L

B

A

I

L

N

m

e

REF

CS

m

e

peak

L















Where,

important.

Consider these parameters, two examples of the typical application inductance is recommended as below:

System Spec.

Inductance Value

System Frequency

60V/150mA

2.3mH

11.5µS

2.5mH

12.1µS