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TNY274P 参数 Datasheet PDF下载

TNY274P图片预览
型号: TNY274P
PDF下载: 下载PDF文件 查看货源
内容描述: 高能效,离线式开关具有更大的灵活性和扩展功率范围 [Energy Efficient, Off-Line Switcher with Enhanced Flexibility and Extended Power Range]
分类和应用: 开关
文件页数/大小: 24 页 / 1604 K
品牌: POWERINT [ Power Integrations ]
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TNY274-280  
For lower no-load input power consumption, the bias winding  
may also be used to supply the TinySwitch-III device. Resistor  
R8 feeds current into the BP/M pin, inhibiting the internal high  
voltage current source that normally maintains the BP/M pin  
capacitor voltage (C7) during the internal MOSFET off time.  
This reduces the no-load consumption of this design from  
140 mW to 40 mW at 265 VAC.  
Key Application Considerations  
TinySwitch-lll Design Considerations  
Output Power Table  
The data sheet output power table (Table 1) represents the  
minimum practical continuous output power level that can be  
obtained under the following assumed conditions:  
Under-voltage lockout is configured by R5 connected between  
the DC bus and EN/UV pin of U1. When present, switching  
is inhibited until the current in the EN/UV pin exceeds 25 µA.  
This allows the startup voltage to be programmed within the  
normal operating input voltage range, preventing glitching of  
the output under abnormal low voltage conditions and also on  
removal of the AC input.  
1. The minimum DC input voltage is 100 V or higher for  
85 VAC input, or 220 V or higher for 230 VAC input or  
115 VAC with a voltage doubler. The value of the input  
capacitance should be sized to meet these criteria for AC  
input designs.  
2. Efficiency of 75%.  
3. Minimum data sheet value of I2f.  
4. Transformer primary inductance tolerance of ±10%.  
5. Reflected output voltage (VOR) of 135 V.  
6. Voltage only output of 12 V with a fast PN rectifier diode.  
7. Continuous conduction mode operation with transient KP*  
value of 0.25.  
8. Increased current limit is selected for peak and open frame  
power columns and standard current limit for adapter  
columns.  
9. The part is board mounted with SOURCE pins soldered to  
a sufficient area of copper and/or a heatsink is used to keep  
the SOURCE pin temperature at or below 110 °C.  
10. Ambient temperature of 50 °C for open frame designs and  
40 °C for sealed adapters.  
In addition to the simple input pi filter (C1, L1, C2) for  
differential mode EMI, this design makes use of E-Shield™  
shielding techniques in the transformer to reduce common  
mode EMI displacement currents, and R2 and C4 as a damping  
network to reduce high frequency transformer ringing. These  
techniques, combined with the frequency jitter of TNY278,  
give excellent conducted and radiated EMI performance with  
this design achieving >12 dBµV of margin to EN55022 Class  
B conducted EMI limits.  
For design flexibility the value of C7 can be selected to pick one  
of the 3 current limits options in U1. This allows the designer  
to select the current limit appropriate for the application.  
*Below a value of 1, KP is the ratio of ripple to peak primary  
current. To prevent reduced power capability due to premature  
termination of switching cycles a transient KP limit of ≥0.25  
Standardcurrentlimit(ILIMIT)isselectedwitha0.1µFBP/M  
pin capacitor and is the normal choice for typical enclosed  
adapter applications.  
When a 1 µF BP/M pin capacitor is used, the current  
limit is reduced (ILIMITred or ILIMIT-1) offering reduced RMS  
device currents and therefore improved efficiency, but at  
the expense of maximum power capability. This is ideal  
for thermally challenging designs where dissipation must  
be minimized.  
When a 10 µF BP/M pin capacitor is used, the current  
limit is increased (ILIMITinc or ILIMIT+1), extending the power  
capability for applications requiring higher peak power or  
continuous power where the thermal conditions allow.  
is recommended. This prevents the initial current limit (IINIT  
from being exceeded at MOSFET turn on.  
)
For reference, Table 2 provides the minimum practical power  
deliveredfromeachfamilymemberatthethreeselectablecurrent  
limitvalues. Thisassumesopenframeoperation(notthermally  
limited) and otherwise the same conditions as listed above.  
These numbers are useful to identify the correct current limit  
to select for a given device and output power requirement.  
Overvoltage Protection  
The output overvoltage protection provided by TinySwitch-III  
uses an internal latch that is triggered by a threshold current  
of approximately 5.5 mA into the BP/M pin. In addition to an  
internal filter, the BP/M pin capacitor forms an external filter  
providing noise immunity from inadvertent triggering. For the  
bypass capacitor to be effective as a high frequency filter, the  
capacitorshouldbelocatedascloseaspossibletotheSOURCE  
and BP/M pins of the device.  
Furtherexibilitycomesfromthecurrentlimitsbetweenadjacent  
TinySwitch-IIIfamilymembersbeingcompatible. Thereduced  
current limit of a given device is equal to the standard current  
limitofthenextsmallerdeviceandtheincreasedcurrentlimitis  
equal to the standard current limit of the next larger device.  
E
2/06  
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