- 您现在的位置：买卖IC网 > PDF目录20516 > 750105 (Wurth Electronics Inc)BOARD EVAL FOR LT3574 PDF资料下载
参数资料
| 型号： | 750105 |
| 厂商： | Wurth Electronics Inc |
| 文件页数： | 7/24页 |
| 文件大小： | 0K |
| 描述： | BOARD EVAL FOR LT3574 |
| 标准包装： | 1 |
| 主要目的： | DC/DC，步降 |
| 输出及类型： | 1，隔离 |
| 功率 - 输出： | 2.5W |
| 输出电压： | 5V |
| 电流 - 输出： | 500mA（最小值） |
| 输入电压： | 10 ~ 30 V |
| 稳压器拓扑结构： | 回扫 |
| 板类型： | 完全填充 |
| 已供物品： | 板 |
| 已用 IC / 零件： | LT3574 |
| 其它名称： | 732-3309 |
LT3574
OPERATION
The LT3574 is a current mode switching regulator IC
designed specifically for the isolated flyback topology.
The special problem normally encountered in such cir-
cuits is that information relating to the output voltage on
the isolated secondary side of the transformer must be
communicated to the primary side in order to maintain
regulation. Historically, this has been done with opto-isola-
tors or extra transformer windings. Opto-isolator circuits
waste output power and the extra components increase
the cost and physical size of the power supply. Opto-
isolators can also exhibit trouble due to limited dynamic
response, nonlinearity, unit-to-unit variation and aging
over life. Circuits employing extra transformer windings
also exhibit deficiencies. Using an extra winding adds to
the transformer’s physical size and cost, and dynamic
response is often mediocre.
The LT3574 derives its information about the isolated
output voltage by examining the primary side flyback
pulse waveform. In this manner, no opto-isolator nor extra
transformer winding is required for regulation. The output
voltage is easily programmed with two resistors. Since this
IC operates in boundary control mode, the output voltage
is calculated from the switch pin when the secondary cur-
rent is almost zero. This method improves load regulation
without external resistors and capacitors.
The Block Diagram shows an overall view of the system.
Many of the blocks are similar to those found in traditional
switching regulators including: internal bias regulator,
oscillator, logic, current amplifier and comparator, driver,
and output switch. The novel sections include a special
flyback error amplifier and a temperature compensation
circuit. In addition, the logic system contains additional
logic for boundary mode operation, and the sampling
error amplifier.
The LT3574 features a boundary mode control method,
where the part operates at the boundary between continu-
ous conduction mode and discontinuous conduction mode.
The VC pin controls the current level just as it does in normal
current mode operation, but instead of turning the switch
on at the start of the oscillator period, the part detects
when the secondary-side winding current is zero.
Boundary Mode Operation
Boundary mode is a variable frequency, current mode
switching scheme. The switch turns on and the inductor
current increases until a VC pin controlled current limit. The
voltage on the SW pin rises to the output voltage divided
by the secondary-to-primary transformer turns ratio plus
the input voltage. When the secondary current through
the diode falls to zero, the SW pin voltage falls below V IN .
A discontinuous conduction mode (DCM) comparator
detects this event and turns the switch back on.
Boundary mode returns the secondary current to zero
every cycle, so the parasitic resistive voltage drops do not
cause load regulation errors. Boundary mode also allows
the use of a smaller transformer compared to continuous
conduction mode and no subharmonic oscillation.
At low output currents the LT3574 delays turning on the
switch, and thus operates in discontinuous mode. Unlike
a traditional flyback converter, the switch has to turn on
to update the output voltage information. Below 0.6V on
the VC pin, the current comparator level decreases to
its minimum value, and the internal oscillator frequency
decreases in frequency. With the decrease of the internal
oscillator, the part starts to operate in DCM. The output
current is able to decrease while still allowing a minimum
switch off-time for the error amp sampling circuitry. The
typical minimum internal oscillator frequency with VC
equal to 0V is 40kHz.
3574f
相关PDF资料 |
PDF描述 |
|---|---|
| 396-062-540-804 | CARD EDGE 62POS DL .125X.250 BLK |
| BAV99WT1 | DIODE SWITCH SS DUAL 70V SOT323 |
| 396-062-540-802 | CARD EDGE 62POS DL .125X.250 BLK |
| BAV99RWT1 | DIODE SWITCH SS DUAL 70V SOT323 |
| 396-062-540-204 | CARD EDGE 62POS DL .125X.250 BLK |
相关代理商/技术参数 |
参数描述 |
|---|---|
| 75010531 | 制造商:PHILIPS 功能描述:STARTER FLUORESCENT TUBE 70-125W 制造商:Philco/Philips 功能描述:STARTER, FLUORESCENT TUBE, 70-125W 制造商:NXP Semiconductors 功能描述:STARTER, FLUORESCENT TUBE, 70-125W; Accessory Type:Starter; For Use With:Fluorescent; SVHC:No SVHC (18-Jun-2012); Power Rating:125W; Supply Voltage:240V ;RoHS Compliant: Yes |
| 750-105-R220/270 | 制造商:CTS Corporation 功能描述: |
| 750-105-R220/330 | 制造商: 功能描述: 制造商:undefined 功能描述: 制造商:CTS Corporation 功能描述:S10-R220/330 |
| 750106 | 功能描述:BOARD EVAL FOR LT3575 RoHS:是 类别:编程器，开发系统 >> 评估板 - DC/DC 与 AC/DC（离线）SMPS 系列:- 标准包装:1 系列:- 主要目的:DC/DC，步降 输出及类型:1，非隔离 功率 - 输出:- 输出电压:3.3V 电流 - 输出:3A 输入电压:4.5 V ~ 28 V 稳压器拓扑结构:降压 频率 - 开关:250kHz 板类型:完全填充 已供物品:板 已用 IC / 零件:L7981 其它名称:497-12113STEVAL-ISA094V1-ND |
| 750-106 | 制造商:GLENAIR 制造商全称:Glenair, Inc. 功能描述:Pre-Terminated Assemblies |
发布紧急采购，3分钟左右您将得到回复。