LM2586S-12 National Semiconductor, LM2586S-12 Datasheet - Page 18

• Manufacturer Part Number: LM2586S-12
• Description: SIMPLE SWITCHER 3A Flyback Regulator with Shutdown
• Manufacturer: National Semiconductor

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Typical Flyback Regulator Applications
Step-Up (Boost) Regulator Operation
Figure 30 shows the LM2586 used as a step-up (boost)
regulator. This is a switching regulator that produces an out-
put voltage greater than the input supply voltage.
A brief explanation of how the LM2586 Boost Regulator
works is as follows (refer to Figure 30 ). When the NPN
switch turns on, the inductor current ramps up at the rate of
V
By adding a small number of external components (as shown in Figure 30 ), the LM2586 can be used to produce a regulated out-
put voltage that is greater than the applied input voltage. The switching waveforms observed during the operation of this circuit
are shown in Figure 31 . Typical performance of this regulator is shown in Figure 32 .
IN
/L, storing energy in the inductor. When the switch turns
FIGURE 28. Schott 67140900
Top View
T6
DS012516-49
FIGURE 30. 12V Boost Regulator
FIGURE 27. Schott 26606
Top View
T7
18
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
tor during the switch on time is transferred to the output dur-
ing the switch off time. The output voltage is controlled by
adjusting the peak switch current, as described in the flyback
regulator section.
(Continued)
OUT
FIGURE 29. Schott 67140890
DS012516-47
− V
IN
)/L. Thus, energy stored in the induc-
Top View
T5
DS012516-51
IN
DS012516-50
, discharging
OUT
)