Flyback converter and controlling method thereof

Patent metadata

Field	Value
Publication number	US-10050538-B2
Application number	US-201715707067-A
Country	US
Kind code	B2
Filing date	Sep 18, 2017
Priority date	Sep 19, 2016
Publication date	Aug 14, 2018
Grant date	Aug 14, 2018

Abstract

A flyback converter includes a primary side circuit, a secondary side circuit and a controller. The primary side circuit includes a primary winding and a main switch electrically connected to the primary winding. The secondary side circuit includes a secondary winding and an output diode electrically connected to the secondary winding and having a parasitic electrical parameter. The controller generates a correcting parameter for counteracting an effect on an output voltage of the flyback converter from the parasitic electrical parameter, wherein the parasitic electrical parameter is an equivalent series-connection resistance R d of the output diode and the secondary side circuit, and the correcting parameter is calculated based on the formula
n p n s ⁢ I ini ⁢ R d ,
wherein n p denotes a turns number of the primary winding, n s denotes a turns number of the secondary winding, and I ini denotes an initial current value which is detected when the main switch is conducted.

First claim

What is claimed is:

1. A flyback converter having an output current and an output voltage, comprising:
a transformer including a primary winding, a secondary winding and an auxiliary winding;
a main switch electrically connected to the primary winding;
an output diode electrically connected to the secondary winding; and
a controller, including:
a current-adjusting parameter generating module receiving an initial current value at a time when the main switch is turned on, a peak current value at a time when the main switch is turned off, a conducting duration of the output diode and a first turns number ratio of the secondary winding to the primary winding to generate a current-adjusting parameter;
a voltage-adjusting parameter generating module receiving the initial current value, the first turns number ratio, a second turns number ratio of the auxiliary winding to the secondary winding, an output voltage value of the flyback converter, a conducted voltage drop value of the output diode and an equivalent resistance of the output diode to generate a voltage-adjusting parameter;
a current adjuster adjusting the output current of the flyback converter according to the current-adjusting parameter; and
a voltage adjuster adjusting the output voltage of the flyback converter according to the voltage-adjusting parameter.

2. The flyback converter as claimed in claim 1 , wherein the output current I o is determined according to the following formula:

I
o

=

1

T
s

⁢

∫
0

T
s

⁢

i
d

⁢
dt

=

T
dis

T
s

⁢

(

I
ini

+

I
PK

2

)

⁢

n
p

n
s

,

where T s denotes an operating cycle of the main switch, i d denotes a current value flowing through the output diode, T dis denotes the conducting duration of the output diode, I ini denotes the initial current value being detected when the main switch starts conducting, I PK denotes the peak current value being detected when the main switch ends conducting, n p denotes a turns number of the primary winding, and n s denotes a turns number of the secondary winding.

3. The flyback converter as claimed in claim 1 , wherein the auxiliary winding has a mapping voltage V aux determined by the following formula:

v
aux

⁡

(

t
s

)

=

n
aux

n
s

⁢

(

V
o

+

nI
ini

⁢

R
d

+

V
F

)

,

where V O denotes the output voltage value of the flyback converter, n denotes the first turns number ratio of the secondary winding to the primary winding, n aux denotes a third turns number of the auxiliary winding, R d denotes an equivalent series-connection resistance of the output diode and a secondary side circuit, and V F denotes the conducted voltage drop value of the output diode.

4. The flyback converter as claimed in claim 1 , wherein the current-adjusting parameter generating module is a feedback current-trimming module, and the voltage-adjusting parameter generating module is a feedback voltage-trimming module.

5. The flyback converter as claimed in claim 2 , wherein:
the initial current value I ini is detected at a first moment after the main switch is turned on for a first predetermined duration to avoid a surge.

6. The flyback converter as claimed in claim 5 , wherein:
the peak current value I PK is detected at a second moment before the main switch is turned off for a second predetermined duration to compensate an offset value resulting from a delay detection of the first predetermined duration on the initial current I ini .

7. A flyback converter comprising:
a primary side circuit including a primary winding and a main switch electrically connected to the primary winding;
a secondary side circuit including a secondary winding and an output diode electrically connected to the secondary winding and having a parasitic electrical parameter; and
a controller generating a correcting parameter for counteracting an effect on an output voltage of the flyback converter from the parasitic electrical parameter, wherein the parasitic electrical parameter is an equivalent series-connection resistance R d of the output diode and the secondary side circuit, and the correcting parameter is calculated based on the formula

n
p

n
s

Assignees

• Univ Nat Cheng Kung

Inventors

• Liang Tsorng-Juu
• Chen kai-hui
• Chen Jiann-Fuh

Classifications

• H02M3/33523

  with galvanic isolation between input and output of both the power stage and the feedback loop · CPC title

• H02M1/44

  Circuits or arrangements for compensating for electromagnetic interference in converters or inverters · CPC title

• H02M3/3385

  with automatic control of output voltage or current (H02M3/33561 takes precedence) · CPC title

• H02M3/33507 Primary

  with automatic control of the output voltage or current, e.g. flyback converters (H02M3/33561, H02M3/33569 take precedence) · CPC title

• H02M3/33515

  with digital control · CPC title