Microchip HV9982DB1 Bedienungsanleitung


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Supertex inc.
Supertex inc.
www.supertex.com
HV9982DB1
Doc.# DSDB-HV9982DB1
A032913
General Description
The HV9982DB1 is a three channel boost LED driver
demoboard using Supertex’s HV9982 LED Driver IC. The
LED driver can be used to drive RGB or multi channel
white LEDs from a 24V input. The LED string current can
be adjusted up to a maximum of 100mA. The demoboard
has good current matching between strings and an excellent
PWM dimming response, making it ideal for LED backlight
applications.
The HV9982DB1 uses the HV9982 LED driver IC to drive
three discontinuous conduction mode boost converters
at a 500kHz switching frequency. The clocks of the three
channels are phase shifted to provide ripple cancellation at
the input and thus reducing the input capacitor requirements.
The output current level can be adjusted using an external
voltage source at the REF terminal.
The HV9982DB1 includes hiccup mode protection for both
short circuit and open circuit conditions to ensure that it
recovers from a momentary fault condition. It also enables
the board to survive prolonged fault conditions without any
damage to both the driver as well as the LEDs.
The HV9982DB1 also includes an on-board PWM generator
for analog control for PWM dimming (for backward
compatibility with CCFL controllers). This feature enables
the user to PWM dim the driver with a 0 - 2.0V analog signal
input and helps to achieve zero LED current with an analog
dimming input
Connection Diagram
Three Channel
LED Driver Demoboard
Speciîš¿cations
Parameter Value
Input voltage 24V ± 10%
LED string voltage (all channels) 35V – 80V
LED current (all channels) 100mA (max)
Switching frequency of the
converter at FCLK = 6.0MHz 500kHz
External frequency at CLK pin 6MHz
Current matching between
channels ≤ ± 3%
Typical full load efîš¿ciency 90%
PWM dimming
rise and fall times ≤1μs
PWM dimming frequency
(for analog control of PWM
dimming)
480Hz (typ)
Shutdown mode current ≤ 600μA
Typical IDD current
(for all three channels) 12mA (VDD = 8V)
Open LED drotection Included; hiccup-mode
Output short circuit protection Included; hiccup-mode
Hiccup time 1ms (typ)
24V DC source
0 - 0.5V
DC source
6MHz clock
(TTL compatible)
- +
+
-
2
HV9982DB1
Supertex inc.
www.supertex.com
Doc.# DSDB-HV9982DB1
A032913
Connections
Pin Connection
VIN This terminal is the positive input of the 24V supply for the boost converters. It is also the input for the
internal regulator of the IC.
GND, GND1 These terminals are the return paths for all the input voltages and signals for the demoboard. All voltages
and signals (other than the output terminals) should be referenced to these two terminals.
VDD
This terminal is connected to the VDD pins of the IC. When left unconnected, the voltage at this terminal
will be regulated to 7.75V by the internal regulator of the HV9982. To supply the IC with an external VDD
supply, connect an 8-10V source to this terminal.
EN This terminal can be used to shut down the IC. Connecting this terminal to GND will cause the IC to go
into a standby mode and draw less than 500μA.
CLK
This terminal is the clock input to the IC. A TTL compatible 6MHz clock should be connected to this ter-
minal. In case an on-board clock is preferred, a 6MHz îš¿xed frequency oscillator can be soldered in at U2
(please refer to BOM for the part number).
5V
A 5.0V, 50mA source needs to be connected to this point, if an on-board clock is used. This provides
the power required for the îš¿xed frequency oscillator at U2. This terminal can be left open if an external
6.0MHz clock is used.
REF This terminal is the control input for adjusting the LED current level. A 0 – 500mV voltage source should
be connected to this terminal.
S1, S2
These two switches on the demoboard control the PWM dimming function. They can be used to enable
either direct PWM dimming of the channels using an external TTL signal or analog control of PWM dim-
ming using a 0-2.0V analog signal. The control logic for these switches is given in Table 1.
PWMD1-3 These terminals are the PWM dimming inputs. The inputs can be either TTL compatible square wave
signals or 0-2.0V analog signals depending on the conîš¿guration of switches S1 and S2.
VO+1-3 The anodes of the LED strings should be connected to these terminals as shown in the connection dia-
gram.
VO- 1-3 The cathodes of the LED strings should be connected to these terminals as shown in the connection
diagram.
SKIP This terminal is connected to the hiccup timing capacitor and can be used to measure the hiccup time.
SYNC
This terminal can be used to synchronize the internal PWM ramp to an external clock. A TTL compatible,
350 – 400Hz external clock with a pulse width less than 2% can be applied at this terminal to synchronize
the internal ramp to the external clock.
Table 1 : Truth Table for S1 and S2
S1 S2 PWMD Output
LO LO The output will follow PWMD input signal
LO HI
HI LO Input DC zero volt corresponds to 100% duty cycle output
HI HI Input DC two volt corresponds to 100% duty cycle output
3
HV9982DB1
Supertex inc.
www.supertex.com
Doc.# DSDB-HV9982DB1
A032913
Normal Operation – Connect the board as shown in the
connection diagram. Ensure that switches S1 and S2 are
LO. Turn on the clock, 24V supply and the reference volt-
age. Connect any of the PWMD pins to VDD. The LEDs of
the corresponding channel will light up. Measure the LED
current using an ammeter and the reference voltage using a
voltmeter. The current will be:
ILED = VREF ± 3.0%
4.99
(1)
Current matching – Without changing the reference volt-
age, enable each channel individually and measure the cur-
rent (or, if possible, enable all channels and the three output
currents simultaneously). The error will be ≤ ± 3%.
Linear Dimming – Vary the reference voltage between 0
– 500mV and measure the LED current.
The current will vary as per Eqn.1. This variation is fairly lin-
ear until the REF voltage gets very low. As the voltage goes
below 50mV, the current will not match the reference voltage
as linearly.
PWM Dimming – With the reference voltage xed at 0.5V,
apply a TTL compatible square wave signal (≤1kHz). The
LED current will dim based on the duty cycle of the PWM
input.
Analog Control of PWM Dimming – Change S1 and S2 as
required using Table 1. Connect the analog 0-2V source at
the PWMD terminal and turn on the demoboard. The LEDs
will dim and the LED current can be adjusted by varying the
analog voltage.
Open LED protection – Connect a voltage probe between
the VO+ terminal of any channel and GND and disconnect
the LED string. The output voltage will rise up to 92V and
trip the over voltage protection. At this point, all three chan-
nels will shut down and the output voltage of the channel
with the open LED condition will be maintained hysteretically
between 92V and 82V until the output voltage of the fauly
channel falls below 82V or till the LED string is reconnected.
Once the LED string is reconnected, all three channels will
turn back on.
Short Circuit Protection – Short the output terminals of any
one channel using a jumper. All three channels shut down
and the IC tries restarting every 1.0ms. Once the short circuit
is removed, all three channels come back into regulation.
Testing the Demoboard


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Modell: HV9982DB1

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