參數(shù)資料
型號(hào)： MAX5003
廠商： Maxim Integrated Products, Inc.
英文描述： High-Voltage PWM Power-Supply Controller
中文描述： 高壓PWM電源控制器
文件頁數(shù)： 12/16頁
文件大?。?/td> 170K
代理商： MAX5003
M
3) The main factors influencing the choice of the turns
ratio are the switch breakdown voltage and the duty
cycle. With a smaller turns ratio, the secondary
reflected voltage and the maximum voltage seen by
the switch during flyback are reduced, which is
favorable. On the other hand, a smaller turns ratio
will shorten the duty cycle and increase the primary
RMS current, which can impact efficiency. A good
starting figure is the ratio of the input voltage to the
output voltage, rounding to the nearest integer. To
keep the flyback voltage under control, choose an 8-
to-1 ratio for the 48V to 5V system. The maximum
duty cycle allowed without putting the device in con-
tinuous-conduction mode can be found using the fol-
lowing formula:
where:
N = N
P
/N
S
= Turns ratio
V
SEC
= Secondary voltage
DC
MAX
= Maximum duty cycle
V
MIN
= Minimum power-line voltage
For a 48V to 5V system with an 8-to-1 turns ratio, the
maximum duty cycle before putting the device in
discontinuous mode is 55%. Assume that V
IN
min is
36V (minimum input voltage, neglecting drops in the
power switch and in the resistance of the primary
coil) and V
SEC
is 5.4V (5V plus a Schottky diode
drop). The MAX5003 maximum duty cycle is internal-
ly limited to 75%. Generally this parameter must fall
between 45% to 65% to obtain a balance between
efficiency and flyback voltage while staying out of
continuous conduction. If the value exceeds these
bounds, adjust the turns ratio.
4) Assuming 80% efficiency, a 6.25W input is needed
to produce a 5W output. Set an operating duty cycle
around 12% below the maximum duty cycle to allow
for component variation: 55% - 12% = 43%. Use the
following formula to calculate the primary inductance:
L
DC V
PWR
V
W
kHz
H
PRI
MIN
IN
SW
=
(
)
=
(
)
μ
2
2
2
0.
2 6 25
.
300
65
DC
V
V
N
MAX
MIN
SEC
=
+
1
1
High-Voltage PWM
Power-Supply Controller
12
______________________________________________________________________________________
10
μ
F
0.1
μ
F
C
F
390pF
0.1
μ
F
0.1
μ
F
0V
470nF
R
F
200k
R
CS
0.1
51k
62k
V+
INDIV
ES
FREQ
SS
REF
CON
COMP
8
7
6
5
4
3
2
1
9
10
11
12
13
14
15
16
V
DD
V
CC
NDRV
PGND
CS
AGND
CMSD4448
XFACOILTRCTX03
MBRS130L
8
2
5
7
11, 12
9, 10
IRFD620S
MAXTON
FB
39k
1M
33
μ
F
0.1
μ
F
100
+5V
1A
+48V
(36V TO 72V)
V
IN
R
A
41.2k
R
17.4k
22
μ
F
4.7
μ
F
L
P
65
μ
H
22
μ
F
MAX5003
Figure 2. Application Example 1: Nonisolated +48V to +5V Converter
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MAX5003-50WEVKIT 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:Evaluation Kit for the MAX5003-50W
MAX5003C/D 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:High-Voltage PWM Power-Supply Controller
MAX5003CEE 功能描述:電壓模式 PWM 控制器 PWM Power-Supply Controller RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel
MAX5003CEE+ 功能描述:電壓模式 PWM 控制器 PWM Power-Supply Controller RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel
MAX5003CEE+T 功能描述:電壓模式 PWM 控制器 PWM Power-Supply Controller RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel
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