lm2588sx-adj National Semiconductor Corporation, lm2588sx-adj Datasheet - Page 20

• Manufacturer Part Number: lm2588sx-adj
• Description: Simple Switcher 5a Flyback Regulator With
• Manufacturer: National Semiconductor Corporation

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Typical Flyback Regulator Applications
Step-Up (Boost) Regulator
Operation
Figure 33 shows the LM2588 used as a step-up (boost)
regulator. This is a switching regulator that produces an
output voltage greater than the input supply voltage.
A brief explanation of how the LM2588 Boost Regulator
works is as follows (refer to Figure 33). When the NPN
switch turns on, the inductor current ramps up at the rate of
By adding a small number of external components (as
shown in Figure 33), the LM2588 can be used to produce a
regulated output voltage that is greater than the applied input
FIGURE 33. 12V Boost Regulator
FIGURE 32. Schott 67140930
Top View
T4
20
V
off, the lower end of the inductor flies above V
its current through diode (D) into the output capacitor (C
at a rate of (V
inductor during the switch on time is transferred to the output
during the switch off time. The output voltage is controlled by
adjusting the peak switch current, as described in the flyback
regulator section.
voltage. The switching waveforms observed during the op-
eration of this circuit are shown in Figure 34. Typical perfor-
mance of this regulator is shown in Figure 35.
(Continued)
IN
/L, storing energy in the inductor. When the switch turns
OUT
01242048
− V
IN
)/L. Thus, energy stored in the
01242049
IN
, discharging
OUT
)