HV9910DB4 Low Voltage, Buck Boost, High Brightness LED Driver Introduction Specifications The Supertex HV9910DB4 demo board is a complete high current, high brightness (HB) LED power driver to supply a string of LEDs using the HV9910 IC from a low DC voltage. The demo board can be used to test the performance of the HV9910 as a constant current driver to power LEDs. HV9910DB4 can drive LED strings whose voltage is less or more than the input voltage. Input 8VDC - 24VDC (replacing C1 and C2 with 35V capacitors will increase the maximum input voltage rating to 30V) Load Current LED String Voltage HV9910DB3 can supply a maximum output current of 350mA to drive LED strings having a maximum string voltage of 22V. HV9910DB4 is ideally suited to drive a string of 5 or 6 high brightness LEDs at high efficiencies (typically greater than 85%). Switching Frequency Efficiency 350mA maximum (see instructions) 22V maximum 80kHz >85% (typ.) The power conversion stage of HV9910DB4 consists of a current-controlled buck-boost converter operating at a switching frequency of 80kHz. The nominal output current of the demo board can be adjusted to any value less than 350mA using the onboard trimming potentiometer. PWM dimming can be achieved by applying a pulse-width-modulated square wave signal between the PWMD and GND pins. Board Layout and Connections Enable Connection 8 - 30V DC PWM Dimming (optional) A052804 B042204 Supertex, Inc. 4 A052804 * 1235 Bordeaux Drive, Sunnyvale, CA 94089 * Tel: (408) 222-8888 * FAX: (408) 222-4895 * www.supertex.com HV9910DB4 Instructions the same output current over a large input voltage range. VIN+: Connect the positive terminal of the DC input source to this pin. The output current can be set using the following equation: VIN-: Connect the negative terminal of the DC input source to this pin. L x f x s Io = 200 x R 2 sense LED+: Connect the Anode of the LED string to this pin. V 2 x LD Vo where LED-: Connect the Cathode of the LED string to this pin. VDD: This pin is connected to the VDD pin of the HV9910. The typical voltage on the pin is 7.6V. This voltage can be used to drive any additional circuitry required. Please see the datasheet regarding the output current capability at the VDD pin. GND: This pin is connected to the Ground connection of the buck converter. Io : output current (350mA) L: inductor value (15H) fs : switching frequency (80kHz) : estimated efficiency % (85%) Rsense : sense resistor value (0.05) PWMD: This terminal can be used to either enable/disable the converter or to apply a PWM dimming signal. VLD : voltage at the dimming pin Vo : output voltage (22V) To just enable the converter, connect the PWMD pin to the VDD pin. Disconnecting the PWMD pin will cause the circuit to stop. The values in brackets indicate the values for the HV9910DB4. PWM dimming of the LED light can be achieved by turning on and off the converter with low frequency 50Hz to 1000Hz TTL logic level signal. Changing the Duty Ratio of the signal changes the effective average current via the LEDs, changing the light emission. For this particular demo board, the equation for the output current is V 2 I o = 204 x LD (in Amperes) Vo Note: In the case of PWM dimming, the PWMD pin should not be connected to the VDD pin! Testing HV9910DB4 Connect the LED string to the output terminals. Check the polarity of the LED connection, anode end of the string should be connected to the positive output, cathode should be connected to the negative output. Connect the DC input to the input terminals (check the polarity). Short the PWMD pin to VDD. Apply a DC voltage at the input terminals and the LED string should start to glow. Setting the Output Current The output current of the HV9910DB4 depends on the LED string voltage. The power conversion circuit of the HV9910DB4 behaves as a constant power converter. Thus, given a fixed output voltage (as in the case of LEDs, it translates to a fixed output current. The small variation in the LED voltages among different batches of LEDs will cause a small, but usually not significant, change in the LED current. However, changing the number of LEDs or changing the type of LED will alter the preset output current and the potentiometer has to be used to adjust the LED current. However, this circuit will reject any input voltage changes and will maintain An ammeter can be connected in series with the LED(s) to measure the output current. The current level can then be changed by adjusting the trimming potentiometer. 2 A052804 HV9910DB4 Open LED Condition: This power stage cannot be run under open LED condition. A no-load at the output will cause excessive voltages at the output and will damage the demo board. Make sure that the LEDs are connected at the output before powering up the circuit. Linear Dimming Test: Gradual change of current via LED(s) is possible by using the trimming potentiometer placed on the demo board. The HV9910 has a preset voltage reference level of 250mV when the voltage at the LD pin of the IC is above 250mV. The external resistor divider consisting of R2, R3 and potentiometer R5 can change that level by pulling down the pin LD below 250mV, reducing the LED string current in linear fashion. The maximum recommended output current of the HV9910DB4 is 350mA. PWM Dimming Test: During normal demo board operation, by applying a PWM TTL level signal to pin PWMD, the output current through the LEDs can be changed in PWM fashion in a 0 to 100% range. In this dimming mode, the output current has normally two levels - zero and nominal current, except at very low duty ratios where inductor current cannot ramp up to the nominal value within the short time. 3 A052804 HV9910DB4 Schematic Diagram VIN+ LEDC1 C2 10uF, 25V 10uF, 25V VIN- C3 2 L1 15uH VDD 1 LED+ Vin Vdd R2 7 147K C6 0.1uF, 25V HV9910 LD Gate PWMD CS 8 B260A-13 Q1 267K 4 IRFL014 2 GND 3 R3 5 R1 Rosc Gnd 6 C5 2.2uF, 16V D1 1 U1 10uF, 25V R5 0.05 PWMD 5K HV9910DB4 - Bill of Materials Quantity RefDes 3 C1,C2,C3 1 C5 1 C6 1 D1 1 VIN-,VIN+,VDD,PWMD,LED-, LED+,GND 1 L1 1 Q1 1 R1 1 R2 1 R3 1 R5 1 U1 Description 10uF, 25V SMD 1206 Multilayer Ceramic Chip capacitors 2.2uF, 25V SMD 0805 Ceramic Capacitor 0.1uF, 25V SMD 0805 Ceramic Capacitor B260A-13 7 Position Breakaway Header Manufacturer Panasonic Panasonic Panasonic Manufacturer's Part Number ECJ-3YB1E106M ECJ-3YB1E106M ECJ-2VF1E104Z Molex/ Waldom 22-28-4070 15uH, 4.5A inductor 55V, 1.9A SOT-223 N-channel Mosfet 267K, 1/10W, 1% SMD 0805 chip resistor 147K, 1/10W, 1% SMD 0805 chip resistor 5K vertical mount trim pot 0.05 ohm, 1/4W, 1% SMD 1210 chip resistor Universal LED Driver Coilcraft IR Panasonic Panasonic BC components Panasonic Supertex MSS1278-153MXB IRFL014N ERJ-6ENF2673V ERJ-6ENF1473V CT-94W-502 ERJ-L14KF50MU HV9910LG 4 A052804 HV9910DB4 HV9910DB4 - Top layer HV9910DB4 - Bottom Layer Supertex Inc. does not recommend the use of its products in life support applications and will not knowingly sell its products for use in such applications unless it receives an adequate "products liability indemnification insurance agreement." Supertex does not assume responsibility for use of devices described and limits its liability to the replacement of devices determined to be defective due to workmanship. No responsibility is assumed for possible omissions or inaccuracies. Circuitry and specifications are subject to change without notice. For the latest product specifications, refer to the Supertex website: http://www.supertex.com. For complete liability information on all Supertex products, refer to the most current databook or to the Legal/Disclaimer page on the Supertex website. 2004 Supertex Inc. All rights reserved. Unauthorized use or reproduction prohibited. A052804 5 1235 Bordeaux Drive, Sunnyvale, CA 94089 TEL: (408) 222-8888 / FAX: (408) 222-4895 A052804 www.supertex.com