HV9912NG 查看數據表（PDF） - Supertex Inc

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HV9912NG

Switch-mode LED Driver IC With High Current Accuracy and Hiccup Mode Protection

Supertex Inc 

HV9912

Linear Dimming

Linear dimming can be accomplished by varying the voltage

at the IREF pin, as the output current is proportional to the

voltage at the IREF pin. This can be done either by using a

potentiometer from the REF pin or by applying an external

voltage source at the IREF pin.

In the HV9911, due to the offset voltage of the short circuit

comparator as well as the non-linearity of the X2 gain stage,

pulling the IREF pin very close to GND will cause the internal

short circuit comparator to trigger and shut down the IC.

To overcome this in the HV9912, the minimum output of the

gain stage is limited to 125 ~ 250mV, allowing the IREF pin

to be pulled all the way to 0V without triggering the short cir-

cuit comparator. Note: Since this control IC is a peak current

mode controller, pulling the IREF pin to zero will not cause

the LED current to become zero. The converter will still be

operating at its minimum on-time causing a very small cur-

rent to flow through the LEDs. To get zero LED current, the

PWMD input has to be pulled to GND.

Output Cap

Voltage 100V

90V

80V

OVP ON

LED string reconnects

LED string disconnects

OVP OFF

LED string voltage

FLT

Output Current

tRC

tHICCUP1

tHICCUP2

COMP

5V

1V

Fig. 4 Open Circuit Protection

● 1235 Bordeaux Drive, Sunnyvale, CA 94089 ● Tel: 408-222-8888 ● www.supertex.com

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