TEA2164S 查看數據表（PDF） - STMicroelectronics

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TEA2164S

SWITCH MODE POWER SUPPLY PRIMARY CIRCUIT

STMicroelectronics 

TEA2164S

II - GENERAL DESCRIPTION (continued)

Figure 7 : Power Supply Start-up

TEA2164S

VCC

Voltage

0

VCC(START)

VCC(STOP)

Collector

Current

Envelop

0

tBURST

B

B

b

b

Tch

T1

Regulated

Standby

Tch 1s (typ.) TSTART-UP = Tch + T1

T1 0.3s (typ.) T1 : necessary time for voltage setting-up

t

t

b

b

II.4 - Abnormal conditions : safety functions

Overvoltage Protection

When VCC exceeds VCC max, an internal flip-flop

stops output conduction signals. The circuit will

start again after the capacitor C1 discharge ; it

means : after loss of synchronization or after VCC

stop crossing (Figure 8).

In flyback converters, this function protects the

power supply against output voltage runaway.

Under Voltage Lock-out

The TEA2164S control circuit stops operating

when VCC goes under VCC stop.

Power Limitation, Current Protection, Long

Duration Overload Protection

- Output power limitation : by a pulse by pulse

collector current limitation the TEA2164S limits

the maximum output power. VCM1 is the corre-

sponding voltage threshold, its detection is

memorized up to the next period.

- Current protection (transistor protection)

Under particular conditions a hard overload or

short circuit may induce a flux runaway in spite of

the current limitation (VCM1).

The TEA2164S control circuit features a second

current protection, VCM2. When this threshold is

reached an internal flip-flop memorizes it and

output conduction signals are inhibited. The cir-

cuit will send base drives again after capacitor C1

discharge (Figure 8).

- Long duration overload protection : (Figure 9)

An overload is detected when the sense-voltage

on Pin 11 reaches VCM3 before a negative pulse

has been applied to Pin 6. In this case the capaci-

tor C2 (connected to Pin 3) is charged with I3 ch

up to the end of the period and discharged with

I3 disch until a next VCM3 detector. By this way in

case of long duration overload, the capacitor

keeps charging at each period and its voltage

encreases gradually. When the voltage on Pin 3

exceeds VC2, the TEA2164S control circuit stops

sending base drives and memorizes this event.

No restart is allowed as long as Vpin 3 is higher

than VC2 and VCC higher than 4.8V.

* Remark :

- The harder is the overload the faster is the pro-

tection

- The capacitor keeps charging between two burst

after VCM2 detection.

8/16

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