Microchip HV9912DB1 Handleiding

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Supertex inc.

www.supertex.com

HV9912DB1

Doc.# DSDB-HV9912DB1

A032913

The HV9912DB1 is an LED driver demoboard capable of driving up

to 20 one-watt LEDs in series from an input of 21 - 27VDC. It uses

the Supertex HV9912 in a boost topology. The converter has very

good initial regulation (+/-5%) and excellent line and load regulation

over the entire input and output voltage range (<+/- 1%). The full

load efciency of the converter is typically greater than 90%.

The HV9912DB1 is protected against open LED and output short

circuit conditions. It is also protected under input under-voltage

conditions by limiting the input current. It has an excellent PWM

dimming response, with typical rise and fall times less than 1.0μs,

which allows high PWM dimming ratios. The switching frequency of

the HV9912DB1 can be synchronized to other HV9912 boards or

to an external 200kHz clock by connecting the clock to the SYNC

pin of the HV9912DB1.

The HV9912DB1 features hiccup mode short circuit and open LED

protection. Upon detection of either fault condition, the IC shuts

down the driver and periodically attemps to restart until the fault

condition ends. The HV9912DB1 also features a built-in 500ns

blanking to prevent false tripping of the over-current comparator

due to parasitic capacitance spikes during PWM dimming.

Board Layout and Connection Diagram

High Brightness Boost LED Driver Demoboard

with 1:3000 Dimming Ratio and Hiccup Mode Protection

Parameter Value

Input voltage (steady state): 21 - 27VDC

Output LED string voltage: 35V min - 80V max

Output current: 350mA +/-5%

Output current ripple: 10% typical

Switching frequency: 200kHz

Full load efciency: 93% (at 24V input)

Open LED protection: Shuts down at 92V

Output short circuit

protection: Included

Input under voltage

protection: Included

PWM dimming: 1:3000 dimming ratio

at 200Hz

Connections

Input - The input is connected between the terminals of

connector J1 as shown in the Connection Diagram.

Output - The output is connected between the terminals of

connector J2 as shown.

Enable/PWM Dimming - To just enable the board, short pins

PWMD and VDD of connector J3 as shown by the dashed

lines. To PWM dim the board, connect the external push-

pull waveform source between terminals PWMD and GND

of connector J3 as shown by the solid lines.

SYNC - To synchronize two or more boards, connect the

SYNC pins of all the boards together. To synchronize the

HV9912DB1 to an external 200kHz clock, connect the clock

between the SYNC and GND pins of terminal J3.

Note:

During PWM dimming, pin 2 of connector J3 should be left

open. Also, the PWM signal must have the proper polarity

with the positive connected to pin 3 of J3. Note that pin 4

of J3 is internally connected to the return path of the input

voltage.

Actual size: 64.0mm x 34.5mm

General Description Specications

HV9912DB1

Supertex inc.

www.supertex.com

Doc.# DSDB-HV9912DB1

A032913

Testing The Demoboard

Normal Operation: Connect the input source and the output

LEDs as shown in the Connection Diagram and enable the

board. The LEDs will glow with a steady intensity. Connecting

an ammeter in series with the LEDs will allow measurement

of the LED current. The current will be 350mA +/- 5%.

Current Regulation: With the input power to the converter

disconnected, change the LED string voltage within

the specications mentioned. The current output of the

HV9912DB1 will remain very steady over the entire load

range. Vary the input voltage while the circuit is operational.

The current will be regulated over the entire line range.

Open LED test: Connect a voltmeter across the output

terminals of the HV9912DB1. Start the demoboard normally,

and once the LED current reaches steady state, unplug

one end of the LED string from the demoboard. The output

voltage will rise to about 92V and the HV9912DB1 will shut

down. Once the LED string is reconnected, the driver will

start regulating current.

Short Circuit Test: When the HV9912DB1 is operating in

steady state, connect a jumper across the terminals of the

LED string. Notice that the output current will immediately

go to zero and the converter will shut down. Removing the

jumper will cause the HV9912DB1 to restart and continue to

regulate the LED current.

PWM Dimming: With the input voltage to the board

disconnected, apply a TTL compatible, push-pull square wave

signal between PWMD and GND terminals of connector J3

as shown in the Connection Diagram. Turn the input voltage

back on and adjust the duty cycle and/or frequency of the

PWM dimming signal. The output current will track the PWM

dimming signal. Note that although the converter operates

perfectly well at 1.0kHz PWM dimming frequency, the widest

PWM dimming ratio can be obtained at lower frequencies

like 100 or 200Hz.

Typical Results

1. Efciency: The efciency of the converter at various LED

string voltages are shown in Fig.1 (measured at the nominal

input voltage of 24V). Fig.2 shows the full load efciency

of the converter at varying input voltages. The minimum ef-

ciency of 93% for the converter occurs at 21V input and full

load output.

2. Current Regulation: Figs. 3 and 4 show the output cur-

rent regulation vs. output voltage and input voltage respec-

tively. The total current regulation (line and load combined)

is found to be less than 1%.

35 40 45 50 55 60 65 70 75 80

Output ltage (V)Vo

Efficiency (%)

Fig. 1 Efficiency evs. Output Voltag

20 22 24 26 28

Input ltage (V)Vo

Efficiency (%)

Fig. 2 Efficiency evs. Input Voltag

0.346

0.348

0.350

0.352

0.354

35 40 45 50 55 60 65 70 75 80

Output ltage (V)Vo

Output Current (A)

Fig. 3 Output Current tput Voltagvs. Ou e

Fig. 4 Output Current put Voltagevs. In

0.346

0.348

0.350

0.352

0.354

20 22 24 26 28

Input ltage (V)Vo

Output Current (A)

HV9912DB1

Supertex inc.

www.supertex.com

Doc.# DSDB-HV9912DB1

A032913

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 VDD. Once the output volt-

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.

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 nds 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 rst

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 nd-

ing the fault condition still present, shuts down again.

1.0

1.2

1.4

1.6

10152025

Input Voltage (V), Sweep

Input Current (A)

0.1

0.2

0.3

0.4

Output Current (A)

Input Current Output Current

Fig. 5 Input Under-Voltage Behavior

Output ltageVo

COM VoltageP

LED Current

Fig. 6 Open LED Condition

Output ltageVo

Fig. 7 Recovery from an Open LED Condition

COMP Voltage

LED Current

Output ltageVo

Fig. 8 Short Circuit Condition

COMP ltageVo

LED Current

Product specificaties

Merk:	Microchip
Categorie:	Niet gecategoriseerd
Model:	HV9912DB1

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