DAP011 데이터 시트보기 (PDF) - ON Semiconductor

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DAP011

PWM Current−Mode Controller for High−Power Universal Off−Line Supplies

ON Semiconductor 

DAP011/DAP011C

The recurrence in hiccup mode can easily be adjusted by

either reducing the timer or increasing the VCC capacitor.

Figure 26 details the various time portion a hiccup is made

of:

VCC

UVLOhigh

t3

UVLOlow

t1 t2

t’1

Latch−off phase level

t’2

Logic reset level

Drv

100 ms

100 ms

Figure 26. The Burst Period is Ensured by the VCC Capacitor Charge/Discharge Cycle

If by design we have selected a 22 mF VCC capacitor, it

becomes easy to evaluate the burst period and its duty−cycle.

This can be done by properly identifying all time events on

Figure 26 and applying the classical formula:

t

+

DV @

i

C

(eq. 1)

• t1: I = ICC3 = 600 mA, DV = 9 – 6.5 = 2.5 V ³ t1 =

91 ms

• t2: I = 3 mA, DV = 12.8 – 6.5 = 6.3 ³ t1 = 46 ms

• t3: I = 600 mA, DV= 12.8 – 6.5 = 6.3 V ³ t1 = 231ms

• t’1 = t1 = 91 ms

• t’2 = t2 = 46 ms

The total period duration is thus the sum of all these events

which leads to Tfault = 505 ms. If Tpulse = 100 ms, then our

burst duty−cycle equals 100/(505+100) ≈ 16.5%, which is

good. Should the user like to further decrease or, to the

contrary, increase this duty−cycle, changing the VCC

capacitor is an easy job.

Latch−off and Overvoltage Protection

Speedking features a fast comparator that permanently

monitors Pin 2 level. Figure 27 details how it is internally

arranged:

Rupper

VCC aux

+

aux

C1

10 nF

2

Rlower

+

−

+

Vlatch

20 ms time constant

S

Q

Q

latched

fault

R

5 V reset

Figure 27. A Comparator Monitors Pin 2 and Latches

Off the Part in Case the Threshold is Reached

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