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參數(shù)資料
| 型號： | L6599D |
| 廠商： | 意法半導體 |
| 英文描述： | High-voltage resonant controller |
| 中文描述： | 高壓諧振控制器 |
| 文件頁數(shù)： | 19/36頁 |
| 文件大?。?/td> | 591K |
| 代理商： | L6599D |
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L6599
Application information
19/36
Essentially, RF
max
will define the switching frequency f
max
above which the L6599 will enter
burst-mode operation. Once fixed f
max
, RF
max
will be found from the relationship:
Note that, unlike the f
max
considered in the previous section ("
Chapter 7.1: Oscillator
"), here
f
max
is associated to some load Pout
B
greater than the minimum one. Pout
B
will be such that
the transformer's peak currents are low enough not to cause audible noise.
Resonant converter's switching frequency, however, depends also on the input voltage;
hence, in case there is quite a large input voltage range with the circuit of
Figure 23
the
value of Pout
B
would change considerably. In this case it is recommended to use the
arrangement shown in
Figure 24
where the information on the converter's input voltage is
added to the voltage applied to the STBY pin. Due to the strongly non-linear relationship
between switching frequency and input voltage, it is more practical to find empirically the
right amount of correction R
A
/ (R
A
+ R
B
) needed to minimize the change of Pout
B
. Just be
careful in choosing the total value R
A
+ R
B
much greater than R
C
to minimize the effect on
the LINE pin voltage (see
Chapter 7.6: Line sensing function
).
Whichever circuit is in use, its operation can be described as follows. As the load falls below
the value Pout
B
the frequency will try to exceed the maximum programmed value f
max
and
the voltage on the STBY pin (V
STBY
) will go below 1.25V. The IC will then stop with both
gate-drive outputs low, so that both MOSFETs of the half-bridge leg are in OFF-state. The
voltage V
STBY
will now increase as a result of the feedback reaction to the energy delivery
stop and, as it exceeds 1.3V, the IC will restart switching. After a while, V
STBY
will go down
again in response to the energy burst and stop the IC. In this way the converter will work in a
burst-mode fashion with a nearly constant switching frequency. A further load decrease will
then cause a frequency reduction, which can go down even to few hundred hertz. The timing
diagram of
Figure 25
illustrates this kind of operation, showing the most significant signals.
A small capacitor (typically in the hundred pF) from the STBY pin to ground, placed as close
to the IC as possible to reduce switching noise pick-up, will help get clean operation.
To help the designer meet energy saving requirements even in power-factor-corrected
systems, where a PFC pre-regulator precedes the DC-DC converter, the device allows that
the PFC pre-regulator can be turned off during burst-mode operation, hence eliminating the
no-load consumption of this stage (0.5
÷
1W). There is no compliance issue in that because
EMC regulations on low-frequency harmonic emissions refer to nominal load, no limit is
envisaged when the converter operates with light or no load.
To do so, the device provides pin 9 (PFC_STOP): it is an open collector output, normally
open, that is asserted low when the IC is idle during burst-mode operation. This signal will
be externally used for switching off the PFC controller and the pre-regulator as shown in
Figure 26
When the L6599 is in UVLO the pin is kept open, to let the PFC controller start
first.
RF
max
3
8
--
RF
f
min
----------
1
–
--------------------
=
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相關代理商/技術參數(shù) |
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| L6599DTR | 功能描述:軟開關 PWM 控制器 Hi Vltg resonant Controller RoHS:否 制造商:Fairchild Semiconductor 輸出端數(shù)量: 輸出電流: 開關頻率: 工作電源電壓:30 V 電源電流: 最大工作溫度:+ 105 C 最小工作溫度:- 40 C 安裝風格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Reel |
| L6599N | 功能描述:軟開關 PWM 控制器 Hi Vltg resonant Controller RoHS:否 制造商:Fairchild Semiconductor 輸出端數(shù)量: 輸出電流: 開關頻率: 工作電源電壓:30 V 電源電流: 最大工作溫度:+ 105 C 最小工作溫度:- 40 C 安裝風格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Reel |
| L6599NR | 功能描述:電壓模式 PWM 控制器 HV resonant CNTRL RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓撲結構:Buck 輸出電壓:34 V 輸出電流: 開關頻率: 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 |
| L6599TR | 制造商:STMICROELECTRONICS 制造商全稱:STMicroelectronics 功能描述:High-voltage resonant controller |
| L65B | 制造商:Electro-Mech 功能描述: |
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