6kW

7kW

8kW

9kW

10kW

11kW

-23V

-22V

-21V

-20V

-19V

-18V

-17V

-16V

-15V

-14V

-13V

-12V

-11V

-10V

-10ºC

0ºC

10ºC

20ºC

30ºC

40ºC

50ºC

-23V

-22V

-21V

-20V

-19V

-18V

-17V

-16V

-15V

-14V

-13V

-12V

-11V

-10V

-10ºC

0ºC

10ºC

20ºC

30ºC

40ºC

50ºC

10kW

12kW

15kW

20kW

25kW

30kW

3.5kW

4kW

4.5kW

5kW

5.2kW

5.5kW

-23V

-22V

-21V

-20V

-19V

-18V

-17V

-16V

-15V

-14V

-13V

-12V

-11V

-10V

-10ºC

0ºC

10ºC

20ºC

30ºC

40ºC

50ºC

2.5kW

2.7kW

2.8kW

2.9kW

3kW

3.1kW

-23V

-22V

-21V

-20V

-19V

-18V

-17V

-16V

-15V

-14V

-13V

-12V

-11V

-10V

-10ºC

0ºC

10ºC

20ºC

30ºC

40ºC

50ºC

R18=open

R18=51kW

R18=20kW

R18=10kW

Buck-Boost Converter Design Procedure

out

in

out

in

out

swpeak

out

in

swpeak

V

1. Converter Duty Cycle:

D =

V

V

V

D

2. Maximum output current: I

=

I

-

(1 D)

2fs×L

I

V

D

3. Peak switch current:

I

=

+

1 D

2fs

L

-

´ h -

´

æ

ö

´

-

ç

÷

è

ø

-

-

´

(32)

TPS65166

Figure 30. Temperature Compensation Examples for R18 = open, 51 k

Ω, 20 kΩ, 10 kΩ

The first step in the design procedure is to verify whether the maximum possible output current of the buck-boost

converter supports the specific application requirements. To simplify the calculation, the fastest approach is to

estimate converter efficiency by taking the efficiency numbers from the provided efficiency curves or to use a

worst case assumption for the expected efficiency, e.g., 80%. The calculation must be performed for the

minimum assumed input voltage where the peak switch current is the highest. The inductor and external

Schottky diode have to be able to handle this current.

With,

fs = Converter switching frequency (typical 750 kHz)

L = Selected inductor value

η = Estimated converter efficiency (use the number from the efficiency curves or 0.8 as an assumption)

28

Submit Documentation Feedback

Copyright © 2009, Texas Instruments Incorporated

Product Folder Link(s): TPS65166