Microchip HV9911DB1 Handleiding

Microchip Niet gecategoriseerd HV9911DB1

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Supertex inc.

www.supertex.com

HV9911DB3

Doc.# DSDB-HV9911DB3

A032713

General Description

The HV9911DB3 is an LED driver capable of driving up to 25

one-watt LEDs in series from an input of 130 - 200VDC. The

demoboard uses Supertex’s HV9911 in a buck topology with the

HV7800 used for high side current sensing. The converter has

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

regulation over the entire input and output voltage range (<+/-

2%). The full load efciency of the converter is typically greater

than 85%.

The HV9911DB3 is protected against open LED and output short

circuit conditions. It is also protected from input under voltage

conditions. It has a very good PWM dimming response, with

typical rise and fall times of less than 5.0μs, which will allow high

PWM dimming ratios.

The switching frequency of the HV9911DB3 can be synchronized

to other HV9911 boards or to an external 150kHz clock by

connecting the clock to the SYNC pin of the HV9911DB3.

Board Layout and Connection Diagram

High Brightness Step-Down LED Driver Demoboard

with Excellent Current Regulation

Specications

Parameter Value

Input voltage (steady state): 130 - 200VDC

Output LED string voltage: 20V min - 100V max

Average output current: 350mA +/-5%

Output current ripple: 5% typical

Switching frequency: 150kHz

Full load efciency: 90% (at 150V input)

Output short circuit protection: Included

Input under voltage protection: Included

PWM dimming performance: 5.0μs (rise time)

5.0μs (fall time)

Dimensions: 53.7mm x 38.1mm

Connections:

Input - The input is connected between the VIN+ and GND

terminals as shown.

Output - The output is connected between the VO+ and VO-

terminals as shown, with the ANODE of the LED string to

VO+ and the CATHODE to connector VO-.

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

PWMD and VDD of connector J1 as shown. To use the PWM

dimming feature of the board, connect an external push-pull

square wave source between terminals PWMD and GND of

connector J1 as shown by the dotted lines.

SYNC - To synchronize two or more boards, connect the

SYNC pins of all the boards. To synchronize the HV9911DB3

to an external 150kHz clock, connect the clock between the

SYNC pin and the GND pin of connector J1.

Note:

During PWM dimming, the PWMD pin of connector J1

should be left open. Also, the PWM signal must have the

proper polarity, with the positive connected to the VDD

pin of connector J1. Note that the GND pin of connector

J1 is internally connected to the return path of the input

voltage.

Actual Size: 53.7mm X 38.1mm

J2 J4

GND

PWMD

VDD

SYNC

HV9911DB3

Supertex inc.

www.supertex.com

Doc.# DSDB-HV9911DB3

A032713

Demoboard Testing:

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: While the converter is operating,

change the input voltage within its speciied input voltage

range. The current output of the HV9911DB3 will remain very

steady over the entire line range. With the supply turned off,

change the number of LEDs in the string within the specied

limits and turn the power supply back on. The current will still

be regulated at 350mA.

Open LED Test: The buck converter is inherently protected

against open LED conditions since the maximum output

voltage is limited to the input voltage. If the LED string is

disconnected during operation, the output voltage of the

converter will rise and stay at the input voltage level.

Short Circuit Test: When the HV9911DB3 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. To restart the

HV9911DB3, recycle the input power to the demoboard.

PWM Dimming: With the input voltage to the board

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

wave signal between the PWMD and GND terminals of

connector J1 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 a 1kHz PWM dimming

frequency, a wider PWM dimming ratio can be obtained at

lower frequencies, like 100Hz or 200Hz.

Effect of the High Side Disconnect Switch

The high side disconnect switch included in the HV9911DB3

disconnects and reconnects the load during PWM dimming.

This prevents the output capacitor from having to charge/

discharge every cycle, leading to shorter PWM dimming rise

and fall times. It also limits the surge current through the

output sense resistor during output short circuit conditions.

However, the level translator needed to drive the disconnect

FET consumes power during normal operation and reduces

the overall efciency of the converter by about 3% at full

load. The decision to include or exclude the high side driver

should depend on which factor is more important, high PWM

dimming or converter efciency. The following typical results

section will show the results for both cases.

Typical Results

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

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

input voltage of 150V). 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: Fig.3 and Fig.4 show the output

current regulation vs. output voltage and load voltage,

respectively. The total current regulation (line and load

combined) is found to be less than 1%.

20 30 40 50 60 70 80 90 100

Output Voltage (V)

Effi (%ciency )

With T Disconnect FE Without onne Disc ct FET

130 140 150 160 17 18 19 200 0 0 0

Input Voltage (V)

Effi (%ciency )

With T Disconnect FE Wit hout Disconnect FET

Fig. 2 Efficiency vs Input Voltage

Fig. 1 Efficiency vs Output Voltage

335

336

337

338

339

340

130 140 150 160 170 180 19

0 2

In ltput Vo age (V)

Output Cu A)rrent (m

337.0

337.2

337.4

337.6

337.8

338.0

20 30 40 50 60 70 80 90 100

Output Voltage (V)

Output Current (mA)

Fig. 4 Output Current vs Output Voltage

Fig. 3 Output Current vs Input Voltage

HV9911DB3

Supertex inc.

www.supertex.com

Doc.# DSDB-HV9911DB3

A032713

3. Normal Operation: Figs.5a, 5b, and 5c show the drain

voltage and output current waveforms during normal

operation.

4. Open LED Protection: Open LED protection is inherent

for the buck converter, as the maximum output voltage is

limited to the input voltage. Fig.6 shows the output voltage,

LED current, and the drain voltage of the switching FET when

the load is disconnected during normal operation. The FET

is always turned on during this time and the output voltage is

equal to the input voltage. If the output voltage sags due to

current leakage, the FET resumes switching until the input

and output voltages become equal.

5. Output Short Circuit Protection: Fig.7 shows the

waveforms for an output short circuit condition. Although the

FAULT pin goes to zero in about 300ns and the switching is

terminated, the time taken for the disconnect FET to turn off

(and the current to go to zero) will depend on the RC time

constant of the resistor R17 (refer to schematic diagram) and

the CGS of the disconnect FET. In this case, the disconnect

FET is turned off in about 3μs. The rise in the output current

will depend on the saturation current of the disconnect FET.

Drain voltage

LED Current

Fig.5a Waveforms at VIN = 150V and VO = 100V

Fig.5a Waveforms at VIN = 200V and VO = 20V

Fig.5a Waveforms at VIN = 130V and VO = 100V

Output Voltage

FET n Drai Voltage

Output Current

Fig.6 Open LED Protection

Output Current

Drain Voltage of Q1

Output ltage Vo

Fig.7 Output Short Circuit Protection

Product specificaties

Merk:	Microchip
Categorie:	Niet gecategoriseerd
Model:	HV9911DB1

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