MAX15000BEUB 查看數據表（PDF） - Maxim Integrated

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MAX15000BEUB

Current-Mode PWM Controllers with Programmable Switching Frequency

Maxim Integrated 

Current-Mode PWM Controllers with

Programmable Switching Frequency

Choose a higher value for R1 than the one calculated in

the previous equation if a longer startup time can be

tolerated to minimize power loss on this resistor.

The above startup method is applicable to a circuit simi-

lar to the one shown in Figure 1. In this circuit, the ter-

tiary winding has the same phase as the output

windings. Thus, the voltage on the tertiary winding at any

given time is proportional to the output voltage and goes

through the same soft-start period as the output voltage.

The minimum discharge time of C1 from 21.6V to 9.74V

must be greater than the soft-start time of 5.6ms.

Another method for bootstrapping the power supply is

to use a bias winding that is in phase with the MOSFET

on-time (see Figure 5). In this case, the amount of

capacitance required at IN (C1) is much smaller.

However, the input voltage cannot have a range

greater than approximately 2:1 (primary winding volt-

age to bias winding voltage ratio).

For hiccup-mode fault protection, make the bias wind-

ing in phase with the output, then the power-supply hic-

cups and soft-starts under output short-circuit

conditions. The power supply does not hiccup if the

bias winding is in phase with the MOSFET on-time.

VIN

R1

U2

OPTO

TRANS.

C1

R5

R6

D1

UFLG

R2

IN

U1 NDRV

VCC MAX15000A CS

R7

COMP

GND

FB RT

UVLO/EN

C6

C2

R12

R3

R15

T1

D2

VOUT

C4

R8

R9

Q1

U2

OPTO LED

C3

U3

TL431

R4

R10

Figure 5. Secondary-Side Regulated, Isolated Power Supply

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