lm5015mhx National Semiconductor Corporation, lm5015mhx Datasheet - Page 13

• Manufacturer Part Number: lm5015mhx
• Description: High Voltage Monolithic Two-switch Forward Dc-dc Regulator
• Manufacturer: National Semiconductor Corporation

Figure 5 shows the two operating modes of the Two-Switch
Forward converter. During operation, the two MOSFETS are
turned ON and OFF simultaneously. The output voltage is
regulated by modulating the duty cycle of the MOSFETs. The
relationship between the input voltage V
V
former turns ratio k is defined by the following equation.
When the MOSFETS are turned ON, as shown in Figure 5(a),
the input voltage is applied to the power transformer primary.
OUT
, duty cycle D, rectifier diode forward drop V
FIGURE 5. Operating Modes of Two-Switch Forward Converter
IN
, output voltage
F
, and trans-
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The power transformer is magnetized by the application of the
input voltage, and power flows to the secondary side circuit
via transformer coupling. When the MOSFETS are turned
OFF, as shown in Figure 5(b), the power flow to the primary
is cut off. The residual magnetizing inductance of the power
transformer reverses the voltage across the primary winding
and forces the two clamp diodes D
effectively clamps the MOSFETs voltage to the input voltage,
and applies the input voltage in reversed polarity to the power
transformer primary winding to demagnetize and reset the
transformer.
H
and D
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L
to conduct. This
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