Datasheet

+
V
O
_
T1
C
IN
C
PRI
VIN
N N
PRI SEC
C
O
+
V
PRI
_
D1
S
LS
S
HS
TPS55010
www.ti.com SLVSAV0A –APRIL 2011–REVISED JUNE 2011
HOW TO SPECIFY A Fly-Buck TRANSFORMER
If a catalog or standard off the shelf transformer is not available, use this section to determine the transformer
specifications to supply a vendor. Selecting the magnetizing inductance is similar to the conventional flyback
converter operating in continuous conduction mode. One distinction is the voltage across the transformer during
the on time is different. The voltage is the difference in the input voltage and voltage across the primary
capacitor. For a conventional flyback, only the input voltage is across the primary. Another distinction is the peak
current in the primary is the negative current peak.
Table 3. Transformer Design Form
Input Voltage Range (V)
Output Voltage (V)
Output Current (A)
Operating Mode Continuous Conduction Mode
Primary Voltage (V) Use Equation 11 and Equation 12
Duty Cycle Range (%) Use Equation 11
Turns Ratio (N
PRI
:N
SEC
) Use Equation 12
Switching Frequency (Hz) Use Equation 14 to Equation 17
Primary Inductance (H) Use Equation 14 to Equation 17
Peak Current Positive (A) Use Equation 14 to Equation 17
Peak Current Negative (A) Use Equation 14 to Equation 17
Insulation Requirements Functional, Basic, Reinforced
Regulatory Agencies/Specification UL, IEC
Dielectric Withstand Voltage AC DC
Working Voltage AC DC
Figure 25. Topology
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