TEA1703TS

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Product data sheet

Rev. 1 — 7 June 2012

8 of 15

NXP Semiconductors

TEA1703TS

GreenChip SMPS standby control IC

7.8 Optocoupler drive

If a series resistor is used to limit the optocoupler diode current and the output voltage of

the application is 19 V, about 95 % of the driving energy is lost in the series resistor. The

efficiency to drive the optocoupler is therefore not more than about 5 %.

In the intended application, the optocoupler is active in Standby mode. Therefore, the

energy to drive the optocoupler must be as low as possible.

To improve the efficiency of the optocoupler drive, the optocoupler diode can be driven

with a series inductor. The optocoupler diode is then driven like a switched-mode power

of 10 compared to driving it with a series resistor.

(1) Pulse driven.

(2) DC driven.

Fig 6.

Typical optocoupler CTR

001aan124

(average) diode current (

μA)

10

10

100

1000

CTR

(%)

1

(1)

(2)

2.

NXP Semiconductors patented.

Fig 7.

Switched-mode optocoupler driver

001aan125

1

2

3

opto on/off