TEA2164S Просмотр технического описания (PDF) - STMicroelectronics

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TEA2164S

SWITCH MODE POWER SUPPLY PRIMARY CIRCUIT

STMicroelectronics 

TEA2164S

II - GENERAL DESCRIPTION (continued)

Figure 11 : Repetitive Over-current Protection

ICM2

Collector

Current

Envelop

t

0

Tburst

Capacitor

C2 Voltage

VC2

t

0

III - SWITCHING OSCILLATOR AND SYNCHRONIZATION

III.1. Switching oscillator

When the TEA2164S control circuit operates in

burst mode, the switching frequency is fixed by the

free frequency oscillator. The period is determined

by two external components CO and RO.

III.2. Synchronization

In order to avoid any erratic conduction of the

power transistor, the first synchronizationpulse will

arrive simultanously with the sawtooth return of the

TEA2164S oscillator.

To get synchronization the free frequency must be

higher than the synchronization frequency.

When the master-circuit starts to send pulses both

oscillators are not synchonuous.

TO < Tsync. < 1.50 TO

Figure 12 : Free Frequency Running

CURRENT

MIRROR

IO

IO

3.2V

RR

1kΩ

78

TR

RO

CO

Q

TR

5V

15kΩ

7.5kΩ

9.1kΩ

13.4kΩ

V8

0

Tcharge

TR

TO

TO ~ Tcharge + TR

TO ~ 0.4 ROCO + 0.47 CORR

RR ~ 1000Ω

CO in Farad, RO in Ohms

Q conductingin burst mode

2.74V

1.66V

10/16

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