參數(shù)資料
型號(hào)： LT1508C
廠商： Linear Technology Corporation
元件分類： 基準(zhǔn)電壓源/電流源
英文描述： Power Factor and PWM Controller(Voltage Mode)
中文描述： 功率因數(shù)和PWM控制器（電壓模式）
文件頁(yè)數(shù)： 7/16頁(yè)
文件大小： 337K
代理商： LT1508C
7
LT1508
R
SET
(Pin 15):
A resistor from R
SET
to GND sets the
oscillator charging current and the maximum multiplier
output current which is used to limit the maximum line
current.
I
M(MAX)
= 3.75V/R
SET
SS1 (Pin 16):
Soft Start. SS1 is reset to zero for low V
CC
.
When V
CC
rises above the lockout threshold, SS1 is
released to ramp up at a rate set by the internal 12
μ
A
current source and an external capacitor. During this ramp
up, PFC reference voltage is equal to SS1 voltage. After
SS1 rises past 7.5V, reference voltage remains at 7.5V.
V
CC
(Pin 17):
This is the supply for the chip. The LT1508
has two fast gate drivers required to fast charge high
power MOSFET gate capacitances. Good supply bypass-
ing is required consisting of a 0.1
μ
F ceramic capacitor in
parallel with a low ESR electrolytic capacitor (56
μ
F or
higher) in close proximity to IC GND.
PWM SECTION
SS2 (Pin 13):
PWM Soft Start. The comparator PWMOK
monitors the OVP pin and releases the SS2 after the PFC
output gets close to the final voltage.
V
C
(Pin 18):
PWM voltage mode control voltage. Normally
connects to the optocoupler amplifier output. A pull-up
current of 50
μ
A flows out of the pin.
I
LIM
(Pin 19):
PWM current sense input with limit set to
1.1V.
GTDR2 (Pin 20):
The PWM MOSFET gate driver is a 1.5A
fast totem pole output. It is clamped at 15V. Capacitive
loads like the MOSFET gates may cause overshoot. A gate
series resistor of at least 5
will prevent the overshoot.
APPLICATIO
S I
FOR
ATIO
U
Voltage Error Amplifier (PFC Section)
The voltage error amplifier has a 100dB DC gain and 3MHz
unity-gain frequency. The output is internally clamped at
13.3V with V
CC
= 18V. Maximum error amp output voltage
decreases to V
CC
– 1.5V for V
CC
less than 12V. The
noninverting input is tied to the 7.5V
REF
through a diode
and can be pulled down with the SS1 pin. Referring to
Figure 1, V
OUT
= V
REF
[(R1 + R2)/R2]. With R1 = 1M and
R2 = 20k, V
OUT
= 382V. R1 through R4, C1 and C2 form the
compensation for the voltage loop. Gain of the voltage
error amp with the values shown is given by:
W
U
U
VA
OUT
V
OUT
= –
1 + j
(j)(f)(6.6)
f
1
f
11
1 + j
)
)
The small-signal gain for the remaining portion of the
voltage loop for frequencies below the current loop band-
width is (see Figure 2):
V
OUT
VA
OUT
V
IN
(5
π)(
j)(f)(C
OUT
)(V
OUT
)
(R
REF
)(P
IN
)
R
S
(R
IAC
+ 25k)
=
C1
0.47
μ
F
7.5V
REF
1.05V
REF
OVERVOLTAGE
COMPARATOR
LT1508
R3
20k
R4
330k
C2
0.047
μ
F
REGULATOR OUTPUT
V
OUT
= 382V
1508 F01
V
SENSE
OVP
VA
OUT
ERROR AMP
R1
1M
R2
20k
–
+
–
+
Figure 1
(For application help with the PFC portion of this chip, see the LT1248 data sheet)
PI
FU
CTIO
N
S
U
U
With V
IN
= 120VAC, P
IN
= 150W, R
S
= 0.15
, R
REF
= 4k,
R
IAC
= 1M, V
OUT
= 382V and C
OUT
= 470
μ
F, V
OUT
/VA
OUT
=
85/(j)(f). At very low frequencies, the loop has a –40dB/
decade slope. Additional zero-pole compensation is added
at 1Hz and 11Hz. The resulting loop gain and phase margin
is shown in Figure 3. The unity-gain bandwidth is low
compared to 120Hz, which results in low distortion and a
high power factor.
相關(guān)PDF資料
PDF描述
LT1508CN Octal D-Type Edge-Triggered Flip-Flops With 3-State Outputs 24-PDIP 0 to 70
LT1508CSW Octal D-Type Transparent Latches With 3-State Outputs 20-SOIC 0 to 70
LT1508I Power Factor and PWM Controller(Voltage Mode)
LT1508IN Power Factor and PWM Controller(Voltage Mode)
LT1508ISW Power Factor and PWM Controller(Voltage Mode)
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LT1508CN 制造商:LINER 制造商全稱:Linear Technology 功能描述:Power Factor and PWM Controller(Voltage Mode)
LT1508CSW 功能描述:IC PWM/POWER FACTOR CNTRLR20SOIC RoHS:否 類別:集成電路 (IC) >> PMIC - PFC（功率因數(shù)修正） 系列:- 產(chǎn)品培訓(xùn)模塊:GreenChip Synchronous Rectification Control Family of ICs 標(biāo)準(zhǔn)包裝:1 系列:- 模式:間歇導(dǎo)電（DCM） 頻率 - 開關(guān):- 電流 - 啟動(dòng):- 電源電壓:8.6 V ~ 38 V 工作溫度:-20°C ~ 150°C 安裝類型:表面貼裝 封裝/外殼:14-SOIC（0.154"，3.90mm 寬） 供應(yīng)商設(shè)備封裝:14-SO 包裝:Digi-Reel® 其它名稱:568-5348-6
LT1508I 制造商:LINER 制造商全稱:Linear Technology 功能描述:Power Factor and PWM Controller(Voltage Mode)
LT1508IN 制造商:LINER 制造商全稱:Linear Technology 功能描述:Power Factor and PWM Controller(Voltage Mode)
LT1508ISW 功能描述:IC PWM/POWER FACTOR CNTRLR20SOIC RoHS:否 類別:集成電路 (IC) >> PMIC - PFC（功率因數(shù)修正） 系列:- 產(chǎn)品培訓(xùn)模塊:GreenChip Synchronous Rectification Control Family of ICs 標(biāo)準(zhǔn)包裝:1 系列:- 模式:間歇導(dǎo)電（DCM） 頻率 - 開關(guān):- 電流 - 啟動(dòng):- 電源電壓:8.6 V ~ 38 V 工作溫度:-20°C ~ 150°C 安裝類型:表面貼裝 封裝/外殼:14-SOIC（0.154"，3.90mm 寬） 供應(yīng)商設(shè)備封裝:14-SO 包裝:Digi-Reel® 其它名稱:568-5348-6
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