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参数资料
| 型号： | L6564DTR |
| 厂商： | STMICROELECTRONICS |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING CONTROLLER, PDSO10 |
| 封装： | ROHS COMPLIANT, SSOP-10 |
| 文件页数： | 14/34页 |
| 文件大小： | 809K |
| 代理商： | L6564DTR |
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L6564
Application information
Doc ID 16202 Rev 1
21/34
6.2
Feedback failure protection (FFP)
The OVP function above described handles “normal” over voltage conditions, i.e. those
resulting from an abrupt load/line change or occurring at start-up. In case the overvoltage is
generated by a feedback disconnection, for instance when the upper resistor of the output
divider (R1) fails open, an additional circuitry behind the pin PFC_OK detects the voltage
gap with respect to pin INV. If the voltage gap is greater than 40 mV and the OVP is active,
the FFP is triggered, the gate drive activity is immediately stopped, the device is shut down,
its quiescent consumption is reduced below 180 A and the condition is latched as long as
the supply voltage of the IC is above the UVLO threshold. To restart the system it is
necessary to recycle the input power, so that the Vcc voltage of the L6564 goes below 6 V.
The pin PFC_OK doubles its function as a not-latched IC disable: a voltage below 0.23 V will
shut down the IC, reducing its consumption below 2 mA. To restart the IC simply let the
voltage at the pin go above 0.27 V.
Note that these functions offer complete protection against not only feedback loop failures or
erroneous settings, but also against a failure of the protection itself. Either resistor of the
PFC_OK divider failing short or open or a PFC_OK pin floating will result in shutting down
the IC and stopping the pre-regulator.
6.3
Voltage feedforward
The power stage gain of PFC pre-regulators varies with the square of the RMS input
voltage. So does the crossover frequency fc of the overall open-loop gain because the gain
has a single pole characteristic. This leads to large trade-offs in the design.
For example, setting the gain of the error amplifier to get fc = 20 Hz @ 264 Vac means
having fc 4 Hz @ 88 Vac, resulting in a sluggish control dynamics. Additionally, the slow
control loop causes large transient current flow during rapid line or load changes that are
limited by the dynamics of the multiplier output. This limit is considered when selecting the
sense resistor to let the full load power pass under minimum line voltage conditions, with
some margin. But a fixed current limit allows excessive power input at high line, whereas a
fixed power limit requires the current limit to vary inversely with the line voltage.
Voltage feedforward can compensate for the gain variation with the line voltage and allow
minimizing all of the above-mentioned issues. It consists of deriving a voltage proportional to
the input RMS voltage, feeding this voltage into a squarer/divider circuit (1/V2 corrector) and
providing the resulting signal to the multiplier that generates the current reference for the
inner current control loop (see Figure 35).
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相关代理商/技术参数 |
参数描述 |
|---|---|
| L6564H | 功能描述:功率因数校正 IC High Voltage Startup Trans-Mode PFC 700V RoHS:否 制造商:Fairchild Semiconductor 开关频率:300 KHz 最大功率耗散: 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8 封装:Reel |
| L6564HTR | 功能描述:功率因数校正 IC High Volt Start Up 700V PFC 100uA 6mA RoHS:否 制造商:Fairchild Semiconductor 开关频率:300 KHz 最大功率耗散: 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8 封装:Reel |
| L6564T | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:10-pin transition-mode PFC controller |
| L6564TD | 功能描述:功率因数校正 IC 10-Pin Trans Mode PFC Bi 6mA 0.75W RoHS:否 制造商:Fairchild Semiconductor 开关频率:300 KHz 最大功率耗散: 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8 封装:Reel |
| L6564TDTR | 功能描述:功率因数校正 IC 2.5A Single H-Side 9.5V - 35V SP Switch RoHS:否 制造商:Fairchild Semiconductor 开关频率:300 KHz 最大功率耗散: 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:SOIC-8 封装:Reel |
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