HV9912DB1 Supertex, HV9912DB1 Datasheet - Page 3

• Manufacturer Part Number: HV9912DB1
• Description: LED Lighting Development Kits HI BRIGHTNESS BOOST LED DRIVER DEMOBOARD
• Manufacturer: Supertex

Specifications of HV9912DB1

• Lead Free Status / Rohs Status: Supplier Unconfirmed

3. Input Under Voltage Protection: Input under voltage
protection is provided by limiting the input current at low in-
put voltages. Fig. 5 shows the output and input currents at
voltages less than the minimum rated voltage. The LED cur-
rent will decrease as the input voltage falls and the input
current limits to about 1.4A. Note that the input current limit
is not a hard limit as the slope compensation added to the
peak current sense signal will allow a small change in the
input current with a decrease in the input voltage.
4. Open LED Protection: Figs 6 and 7 show the hiccup-
mode over voltage protection. Fig. 6 shows the open LED
condition occurs when the LED current goes to zero. At
that point, the inductor current charges the output capacitor
and the COMP voltage rails to V
age reaches the over voltage threshold, the converter shuts
down and the output voltage slowly decays because the out-
put capacitor is discharged by the over-voltage sensing re-
sistor network. Once the output voltage falls to 90% of its trip
point, the converter tries to restart. Since the fault conditions
still persists, the converter shuts down almost immediately.
Thus, the HV9912 maintains the output voltage in a band
until the LED reconnects.
0.4
0.3
0.2
0.1
Fig. 5 Input Under-Voltage Behavior
25
Fig. 6 Open LED Condition
Input Voltage (V), Sweep
Input Current
COMP Voltage
Output Voltage
20
LED Current
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DD
. Once the output volt-
1235 Bordeaux Drive, Sunnyvale, CA 94089
15
Output Current
10
1.6
1.4
1.2
1
3
Fig. 7 shows the recovery of the HV9912DB1 from an over
voltage condition. In this case, the LED has reconnected
at some point when the converter is turned off. When the
converter attempts to restart, if finds the fault condition has
disappeared and it starts up normally. There is no overshoot
in the LED current .
Short Circuit Protection: Figs 8 and 9 show the operation
of the short circuit protection in the HV9912DB1. In Fig. 8,
the onset of the output short circuit is indicated by the first
spike in the LED current. At this point, the HV9912DB1 shuts
down and the hiccup mode protection takes over. A constant
current source charges the COMP pin to 5.0V and then an-
other current source discharges it to 1.0V. This charge/dis-
charge cycle determines the hiccup time. When the COMP
pin reaches 1.0V, the converter attempts to restart and find-
ing the fault condition still present, shuts down again.
Fig. 7 Recovery from an Open LED Condition
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Fig. 8 Short Circuit Condition
COMP Voltage
LED Current
Output Voltage
COMP Voltage
LED Current
Output Voltage
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HV9912DB1