HV9910DB4 v.2 Low Voltage, Buck Boost, High Brightness LED Driver Demo Board Introduction The Supertex HV9910DB4v.2 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. HV9910DB4v.2 can drive LED strings whose voltage is less or more than the input voltage. Specifications Input 9VDC - 30VDC Load Current 780mA maximum LED String Voltage 10V minimum 22V maximum Switching Frequency HV9910DB4v.2 can supply a maximum output current of 620mA (adjustable using the on-board potentiometer) to drive LED strings having a maximum string voltage of 22V. HV9910DB4v.2 is ideally suited to drive a string of 5 or 6 high brightness LEDs at high efficiencies (typically greater than 85%). This demo board is an improved version of the HV9910DB4 v.2 with over-voltage protection and output voltage feedback to maintain a constant LED current (see Application note AN-H49 for details). The power conversion stage of HV9910DB4v.2 consists of a current-controlled buck-boost converter operating at a variable switching frequency. The nominal output current of the demo board can be adjusted to any value less than 780mA 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. Variable, depends on output voltage Overall Set Point 26V Efficiency >85% (typ.) Actual Size: 53.5mm x 26.75mm Board Layout and Connections PWM Dimming (optional) 8 - 30V DC Enable Connection A082804 HV9910DB4 v.2 Instructions Testing HV9910DB4v.2 VIN+: Connect the positive terminal of the DC input source to this pin. 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. VIN-: Connect the negative terminal of the DC input source to this pin. LED+: Connect the Anode of the LED string to this pin. LED-: Connect the Cathode of the LED string to this pin. 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. 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. Open LED Condition: GND: This pin is connected to the Ground connection of the buck converter. PWMD: This terminal can be used to either enable/disable the converter or to apply a PWM dimming signal. This power stage can be run under open LED condition. When there are no LEDs connected at the output, the converter will switch at a frequency of about 2.5kHz and draw about 0.2 to 0.3W of power from the input. To just enable the converter, connect the PWMD pin to the VDD pin. Disconnecting the PWMD pin will cause the circuit to stop. 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 R12 and potentiometer R11 can change that level by pulling down the pin LD below 250mV, reducing the LED string current in linear fashion. PWM dimming of the LED light can be achieved by turning on and off the converter with a 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. Note: In the case of PWM dimming, the PWMD pin should not be connected to the VDD pin! The maximum recommended output current of the HV9910DB4 v.2 is 780mA. Setting the Output Current The output current of a peak-current-controlled buckboost converter is given by: PWM Dimming Test: By applying a PWM TTL level signal between pins PWMD and GND, 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 the LED current cannot ramp up to the nominal value within the short time. 2 I o 12.5 x VLD where: Io : output current VLD: voltage at the dimming pin 2 A0826804 HV9910DB4 v.2 Schematic Diagram VIN+ R6 100K C1 C2 10uF, 35V 10uF,35V LEDD3 BZX84C24-7 VIN- C3 2 L1 15uH Q2 MMBT2907A C9 10uF, 25V Q3 10uF, 25V C8 R7 100k 10uF, 25V VDD 10Meg Vin C5 2.2uF, 16V 7 5 R12 R8 1k Rosc HV9910 LD Gate PWMD CS Q1 4 NDT3055 U2 Open Circuit Protection 2 GND PWMD R5 0.05, 1/4W R11 Output Voltage Feedback 5k HV9910DB4 v.2 - Bill of Materials Quantity 2 3 1 1 1 7 1 1 2 1 2 1 1 1 1 1 1 1 RefDes C1, C2 C3,C8,C9 C5 D1 D3 VIN-,VIN+,VDD,PWMD, LED-,LED+,GND L1 Q1 Q2,Q3 R5 R6,R7 R8 R9 R10 R11 R12 U2 U3 LED+ B360A-13 8 3 178k Vdd Gnd 6 R9 340K 1 U3 D1 1 R10 Description 10uF, 35V SMD 1812 Multilayer Ceramic Chip capacitors 10uF, 25V SMD 1206 Multilayer Ceramic Chip capacitor 2.2uF, 25V SMD 0805 Ceramic Capacitor 60V, 3A SMA schottky diode 24V, 350mW SOT-23 zener diode 7 Position Breakaway Header Manufacturer Panasonic Panasonic Panasonic Diodes, Inc. Diodes, Inc. Molex/ Waldom Manufacturer's Part Number ECJ-5YF1V106Z ECJ-3YB1E106M ECJ-3YB1E106M B360A-13 BZX84C24-7 22-28-4070 15uH, 4.5A inductor 60V, 4A SOT-223 N-channel Mosfet -60V, 0.6A SOT-23 PNP transistor 0.05, 1/4W, 1% SMD1210chip resistor 100k, 1/10W, 1% SMD0805 chip resistor 1k, 1/8W, 5% SMD0805 chip resistor 340K, 1/10W, SMD0805 1% chip resistor 10Meg, 1/8W, SMD0805 5% chip resistor 5K surface mount trim pot 178k, 1/10W, 1% SMD0805 chip resistor 40V, 600mA dual NPN transistor Universal LED Driver Coilcraft Fairchild Diodes, Inc. Panasonic Panasonic Panasonic Panasonic Panasonic Murata Panasonic Diodes, Inc. Supertex MSS1278-153MXB NDT3055 MMBT2907A ERJ-L14KF50MU ERJ-6ENF1003V ERJ-6GEYJ102V ERJ-6ENF3403V ERJ-6GEYJ106V PVG3A502A01R00 ERJ-6ENF1783V MMDT4401-7 HV9910LG 3 A082804 HV9910DB4 v.2 HV9910DB4 v.2 - Top Layer HV9910DB4 v.2 - Bottom Layer HV9910DB4 v.2 - Top Silk Screen 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 data book or to the Legal/Disclaimer page on the Supertex website. A082804 4 A082804