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HV9910 Universal High Brightness LED Driver
Features
>90% Efficiency 8V to 450V input range Constant-current LED driver Applications from a few mA to more than 1A Output LED string from one to hundreds of diodes PWM Low-Frequency Dimming via Enable pin Input Voltage Surge ratings up to 450V
General Description
The HV9910 is a PWM high-efficiency LED driver control IC. It allows efficient operation of High Brightness (HB) LEDs from voltage sources ranging from 8VDC up to 450VDC. The HV9910 controls an external MOSFET at fixed switching frequency up to 300kHz. The frequency can be programmed using a single resistor. The LED string is driven at constant current rather than constant voltage, thus providing constant light output and enhanced reliability. The output current can be programmed between a few milliamps and up to more than 1.0A. The HV9910 uses a rugged high voltage junction isolated process that can withstand an input voltage surge of up to 450V. Output current to an LED string can be programmed to any value between zero and its maximum value by applying an external control voltage at the linear dimming control input of the HV9910. The HV9910 provides a low-frequency PWM dimming input that can accept an external control signal with a duty ratio of 0-100% and a frequency of up to a few kilohertz.
Applications
DC/DC or AC/DC LED Driver applications RGB Backlighting LED Driver Back Lighting of Flat Panel Displays General purpose constant current source Signage and Decorative LED Lighting Automotive Chargers
Typical Application
VIN VDD
HV9910
LD PWMD RT GATE CS GND
HV9910
Ordering Information
Device HV9910 Package Options SOIC-16 HV9910NG-G SOIC-8 HV9910LG-G
-G indicates package is RoHS compliant (`Green')
Absolute Maximum Ratings
Parameter
VIN to GND CS LD, PWM_D to GND GATE to GND VDDMAX Continuous Power Dissipation (TA = +25C) (Note 1) 16-Pin SO (derate 7.5mW/C above +25C) 8-Pin SO (derate 6.3mW/C above +25C) Operating temperature range Junction temperature Storage temperature range 750mW 630mW -40C to +85C +125C -65C to +150C
Pin Configurations
Value
-0.5V to +470V -0.3V to (VDD + 0.3V) -0.3V to (VDD - 0.3V) -0.3V to (VDD + 0.3V) 13.5V
VIN NC NC CS GND NC NC GATE NC NC ROSC LD VDD NC NC PWM_D GATE VIN CS GND ROSC LD VDD PWM_D
16-Lead SOIC
8-Lead SOIC
Absolute Maximum Ratings are those values beyond which damage to the device may occur. Functional operation under these conditions is not implied. Continuous operation of the device at the absolute rating level may affect device reliability. All voltages are referenced to device ground.
Electrical Characteristics
(Over recommended operating conditions unless otherwise specified - TA = 25C)
Symbol VINDC IINsd VDD VDDmax IDD(ext) UVLO UVLO VEN(lo) VEN(hi) REN VCS(hi) VGATE(hi) VGATE(lo) fOSC DMAXhf VLD TBLANK
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Parameter Input DC supply voltage range Shut-down mode supply current Internally regulated voltage Maximal pin VDD voltage VDD current available for external circuitry 1 VDD undervoltage lockout threshold VDD undervoltage lockout hysteresis Pin PWM_D input low voltage Pin PWM_D input high voltage Pin PWM_D pull-down resistance Current sense pull-in threshold voltage GATE high output voltage GATE low output voltage Oscillator frequency Maximum PWM duty cycle Linear dimming pin voltage range Current sense blanking interval
Min 8.0 7.0 6.45 2.4 50 225 VDD-0.3 0 20 80 0 150
Typ 0.5 7.5 6.7 500 100 250 25 100 215
Max 450 1 8.0 13.5 1.0 6.95 1.0 150 275 VDD 0.3 30 120 100 250 280
Units V mA V V mA V mV V V k mV V V kHz kHz % mV ns
Conditions DC input voltage Pin PWM_D to GND, VIN = 8V VIN = 8 - 450V, IDD(ext) = 0, pin GATE open When an external voltage applied to pin VDD VIN = 8 - 100V VIN rising VIN falling VIN = 8 - 450V VIN = 8 - 450V VEN = 5V @TA = -40C to +85C IOUT = 10mA IOUT = -10mA RT = 1.00M RT = 226k FPWMhf = 25kHz, at GATE, CS to GND. @TA = <85C, VIN = 12V VCS = 0.55VLD, VLD = VDD
Also limited by package power dissipation limit, whichever is lower.
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HV9910
Symbol
tDELAY tRISE tFALL
Parameter
Delay from CS trip to GATE lo GATE output rise time GATE output fall time
Min
-
Typ
30 30
Max
300 50 50
Units
ns ns ns
Conditions
VIN = 12V, VLD = 0.15, VCS = 0 to 0.22V after TBLANK CGATE = 500pF CGATE = 500pF
Pinout
Pin VIN CS GND GATE PWM_D SOIC-16 1 4 5 8 9 SOIC-8 1 2 3 4 5 Description Input voltage 8V to 450V DC Senses LED string current Device ground Drives the gate of the external MOSFET Low Frequency PWM Dimming pin, also Enable input. Internal 100k pull-down to GND Internally regulated supply voltage (7.5V nominal). Can supply up to 1mA for external circuitry. A sufficient storage capacitor is used to provide storage when the rectified AC input is near the zero crossings. Linear dimming by changing the current limit threshold at current sense comparator Oscillator control. A resistor connected between this pin and ground sets the PWM frequency.
VDD
12
6
LD RT
13 14
7 8
No Connects (NC) are not internally connected and may be used for pass-thru PCB traces.
Block Diagram & Typical Applications
VIN
VIN VDD
REG
7.5V
RT
OSC
VDD
250mV LD
CM
SQ R
CM
GATE
CS
PWM_D 100k
HV9910
GND
3
HV9910
Application Information
AC/DC Off-Line Applications
The HV9910 is a low-cost off-line buck or boost converter control IC specifically designed for driving multi-LED stings or arrays. It can be operated from either universal AC line or any DC voltage between 8-450V. Optionally, a passive power factor correction circuit can be used in order to pass the AC harmonic limits set by EN 61000-3-2 Class C for lighting equipment having input power less than 25W. The HV9910 can drive up to hundreds of High-Brightness (HB) LEDs or multiple strings of HB LEDs. The LED arrays can be configured as a series or series/parallel connection. The HV9910 regulates constant current that ensures controlled brightness and spectrum of the LEDs, and extends their lifetime. The HV9910 features an enable pin (PWM_D) that allows PWM control of brightness. The HV9910 can also control brightness of LEDs by programming continuous output current of the LED driver (so-called linear dimming) when a control voltage is applied to the LD pin. The HV9910 is offered in a standard 8-pin SOIC package. It is also available in a high voltage rated SO-16 package for applications that require VIN greater than 250V. The HV9910 includes an internal high-voltage linear regulator that powers all internal circuits and can also serve as a bias supply for low voltage external circuitry. voltage to the LD pin. When soft start is required, a capacitor can be connected to the LD pin to allow this voltage to ramp at a desired rate, therefore, assuring that output current of the LED ramps gradually. Optionally, a simple passive power factor correction circuit, consisting of 3 diodes and 2 capacitors, can be added as shown in the typical application circuit diagram of Figure 1.
Supply Current
A current of 1mA is needed to start the HV9910. As shown in the block diagram on page 3, this current is internally generated in the HV9910 without using bulky startup resistors typically required in the offline applications. Moreover, in many applications the HV9910 can be continuously powered using its internal linear regulator that provides a regulated voltage of 7.5V for all internal circuits.
Setting Light Output
When the buck converter topology of Figure 2 is selected, the peak CS voltage is a good representation of the average current in the LED. However, there is a certain error associated with this current sensing method that needs to be accounted for. This error is introduced by the difference between the peak and the average current in the inductor. For example if the peak-to-peak ripple current in the inductor is 150mA, to get a 500mA LED current, the sense resistor should be 250mV/(500mA+ 0.5*150mA) = 0.43.
LED Driver Operation
The HV9910 can control all basic types of converters, isolated or non-isolated, operating in continuous or discontinuous conduction mode. When the gate signal enhances the external power MOSFET, the LED driver stores the input energy in an inductor or in the primary inductance of a transformer and, depending on the converter type, may partially deliver the energy directly to LEDs The energy stored in the magnetic component is further delivered to the output during the offcycle of the power MOSFET producing current through the string of LEDs (Flyback mode of operation). When the voltage at the VDD pin exceeds the UVLO threshold the gate drive is enabled. The output current is controlled by means of limiting peak current in the external power MOSFET. A current sense resistor is connected in series with the source terminal of the MOSFET. The voltage from the sense resistor is applied to the CS pin of the HV9910. When the voltage at CS pin exceeds a peak current sense voltage threshold, the gate drive signal terminates, and the power MOSFET turns off. The threshold is internally set to 250mV, or it can be programmed externally by applying
Dimming
Dimming can be accomplished in two ways, separately or combined, depending on the application. Light output of the LED can be controlled either by linear change of its current, or by switching the current on and off while maintaining it constant. The second dimming method (so-called PWM dimming) controls the LED brightness by varying the duty ratio of the output current. The linear dimming can be implemented by applying a control voltage from 0 to 250mV to the LD pin. This control voltage overrides the internally set 250mV threshold level of the CS pin and programs the output current accordingly. For example, a potentiometer connected between VDD and ground can program the control voltage at the CS pin. Applying a control voltage higher than 250mV will not change the output current setting. When higher current is desired, select a smaller sense resistor. The PWM dimming scheme can be implemented by applying an external PWM signal to the PWM_D pin. The PWM signal
4
HV9910
can be generated by a microcontroller or a pulse generator with a duty cycle proportional to the amount of desired light output. This signal enables and disables the converter modulating the LED current in the PWM fashion. In this mode, LED current can be in one of the two states: zero or the nominal current set by the current sense resistor. It is not possible to use this method to achieve average brightness levels higher than the one set by the current sense threshold level of the HV9910. By using the PWM control method of the HV9910, the light output can be adjusted between zero and 100%. The accuracy of the PWM dimming method is limited only by the minimum gate pulse width, which is a fraction of a percent of the low frequency duty cycle. Some of the typical waveforms illustrating the PWM dimming method used with the application circuit on page 7 are given below. CH1 shows the MOSFET Drain voltage, CH2 is the PWM signal to pin PWM_D and CH4 is the current in the LED string.
0.4% PWM Ratio at 500Hz Dimming
Programming Operating Frequency
The operating frequency of the oscillator is programmed between 25 and 300kHz using an external resistor connected to the RT pin: FOSC = 25000/(RT [k] + 22) [kHz]
Power Factor Correction
When the input power to the LED driver does not exceed 25W, a simple passive power factor correction circuit can be added to the HV9910 typical application circuit on page 7 in order to pass the AC line harmonic limits of the EN610003-2 standard for Class C equipment. The typical application circuit diagram shows how this can be done without affecting the rest of the circuit significantly. A simple circuit consisting of 3 diodes and 2 capacitors is added across the rectified AC line input to improve the line current harmonic distortion and to achieve a power factor greater than 0.85.
33% PWM Ratio at 500Hz Dimming
Inductor Design
Referring to the typical application circuit on page 7 the value can be calculated from the desired peak-to-peak LED ripple current in the inductor. Typically, such ripple current is selected to be 30% of the nominal LED current. In the example given here, the nominal current ILED is 350mA. The next step is determining the total voltage drop across the LED string. For example, when the string consists of 10 High-Brightness LEDs and each diode has a forward voltage drop of 3.0V at its nominal current; the total LED voltage VLEDS is 30V.
95% PWM Ratio at 500Hz Dimming
5
HV9910
Knowing the nominal rectified input voltage VIN = 120V*1.41 = 169V, the switching duty ratio can be determined, as: D = VLEDs /VIN = 30/169 = 0.177 Then, given the switching frequency, in this example fOSC = 50KHz, the required on-time of the MOSFET transistor can be calculated: TON = D/fOSC = 3.5 microsecond The required value of the inductor is given by: L = (VIN - VLEDs) * TON /(0.3 * ILED) = 4.6mH
Enable
The HV9910 can be turned off by pulling the PWM_D pin to ground. When disabled, the HV9910 draws quiescent current of less than 1mA.
Output Open Circuit Protection
When the buck topology is used, and the LED is connected in series with the inductor, there is no need for any protection against an open circuit condition in the LED string. Open LED connection means no switching and can be continuous.
Input Bulk Capacitor
An input filter capacitor should be designed to hold the rectified AC voltage above twice the LED string voltage throughout the AC line cycle. Assuming 15% relative voltage ripple across the capacitor, a simplified formula for the minimum value of the bulk input capacitor is given by: CMIN = ILED*VLEDs*0.06/VIN^2 CMIN = 22 F, a value 22F/250V can be used. A passive PFC circuit at the input requires using two series connected capacitors at the place of calculated CMIN. Each of these identical capacitors should be rated for 1/2 of the input voltage and have twice as much capacitance.
DC/DC Low Voltage Applications
Buck Converter Operation
The buck power conversion topology can be used when the LED string voltage is needed to be lower than the input supply voltage. The design procedure for a buck LED driver outlined in the previous chapters can be applied to the low voltage LED drivers as well. However, the designer must keep in mind that the input voltage must be maintained higher than 2 times the forward voltage drop across the LEDs. This limitation is related to the output current instability that may develop when the HV9910 buck converter operates at a duty cycle greater than 0.5. This instability reveals itself as an oscillation of the output current at a sub-harmonic of the switching frequency.
6
HV9910
Figure 1: Typical Application Circuit
2A 250V AC Input 85 - 135VAC 0.1F 250V 2R NTC 1.0nF 250V 0.1F 250V Coilcraft BUSH-2820R5b 1N4004 1N4004 68F 160V
1N4004
BYV26B
LEDs 750H
0.1F 250V
VIN
1N4004
RT
280 k
1.0F 10V
VDD
HV9910
GATE LD CS
VN2224 220nF 400V
1N4004 1N4004
1N4004
68F 160V
Optional for PFC 0.2
LED(s) - a string of HB LEDs, 16 diodes
PWM_D
GND
Figure 2: HV9910 Buck driver for a simple 900mA HB LED (VIN = 8 - 30V)
VIN +1
VIN = 8-30V
C7 10F, 35V
C6 10F, 35V
D2 B140-13 L2 220H Q2 4 2 R10 0.27 VN3205
HB LED 900mA at 4.5V
2
VIN -1 U2 6
VDD
1 R11 8 267K
VIN
1
RT
7 C5 2.2F, 10V 5
HV9910
LD Gate
GND
PWMD
CS
3 PWMD1
7
HV9910
16-Lead SOIC (NG) Package Outline
9.9 0.10 16 Notes: Note 2 3.90 0.10 6.0 0.20 1. All dimensions in millimeters; angles in degrees 2. Pin 1 identifier must be located within the indicated area 3. Corner shape may differ from drawing
1
Top View
5O - 15O (4 PLCS)
0.25 - 0.50 Note 3
0O-8
O
0.17 - 0.25 1.75 MAX 1.25MIN 1.27BSC 0.31 - 0.51 0.10 - 0.25 0.40 -1.27
45
Side View
End View
8-Lead SOIC (LG) Package Outline
4.90 0.10 8 6.00 0.20 3.90 0.10 Note 2 Notes: 1. All dimensions in millimeters. Angles in degrees. 2. If the corner is not chamfered, then a Pin 1 identifier must be located within the area indicated.
1
Top View
0.17 - 0.25 1.75 MAX 1.25 MIN
5 - 15 (4 PLCS) 45
0.25 - 0.50 Note 2
0 - 8 0.10 - 0.25 1.27BSC 0.40 - 1.27
0.31 - 0.51
Side View
End View
(The package drawings in this data sheet may not reflect the most current specifications. For the latest package outline information go to http://www.supertex.com/packaging.html.)
Doc.# DSFP-HV9910 D021607
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