參數(shù)資料
型號: L6566B
廠商: 意法半導(dǎo)體
英文描述: Multi-mode controller for SMPS
中文描述: 多模式開關(guān)電源控制器
文件頁數(shù): 27/51頁
文件大?。?/td> 401K
代理商: L6566B
L6566B
Application information
27/51
Figure 15. Externally controlled burst-mode operation by driving pin COMP: timing
diagram
5.6
PWM comparator, PWM latch and voltage feedforward blocks
The PWM comparator senses the voltage across the current sense resistor Rs and, by
comparing it to the programming signal delivered by the feedforward block, determines the
exact time when the external MOSFET is to be switched off. Its output resets the PWM
latch, previously set by the oscillator or the ZCD triggering block, which will assert the gate
driver output low. The use of PWM latch avoids spurious switching of the MOSFET that
might result from the noise generated (“double-pulse suppression”).
Cycle-by-cycle current limitation is realized with a second comparator (OCP comparator)
that senses the voltage across the current sense resistor Rs as well and compares this
voltage to a reference value V
csx
. Its output is or-ed with that of the PWM comparator (see
the circuit schematic in
Figure 17 on page 29
). In this way, if the programming signal
delivered by the feedforward block and sent to the PWM comparator exceeds V
csx
, it will be
the OCP comparator to reset first the PWM latch instead of the PWM comparator. The value
of V
csx
, thereby, determines the overcurrent setpoint along with the sense resistor Rs.
The power that QR flyback converters with a fixed overcurrent setpoint (like fixed-frequency
systems) are able to deliver changes with the input voltage considerably. With wide-range
mains, at maximum line it can be more than twice the value at minimum line, as shown by
the upper curve in the diagram of
Figure 16 on page 28
. The device has the Line
Feedforward function available to solve this issue.
It acts on the overcurrent setpoint V
csx
, so that it is a function of the converter’s input voltage
Vin sensed through a dedicated pin (15, VFF): the higher the input voltage, the lower the
Vcc
(pin 5)
Vcc
ON
GD
(pin 4)
Vcc_OK
Vcc
OFF
Vcc
restart
I
charge
0.85 mA
Standby is commanded here
t
t
t
t
t
COMP
(pin 9)
t
Vout
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L6566BH 功能描述:電流型 PWM 控制器 Multimode Controller SMPS 800V <3mA RoHS:否 制造商:Texas Instruments 開關(guān)頻率:27 KHz 上升時(shí)間: 下降時(shí)間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:TSSOP-14
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