Supertex inc. HV9911DB3 High Brightness Step-Down LED Driver Demoboard with Excellent Current Regulation 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 efficiency 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. Specifications Parameter Value Input voltage (steady state): Output LED string voltage: 130 - 200VDC 20V min - 100V max Average output current: 350mA +/-5% Output current ripple: 5% typical Switching frequency: 150kHz Full load efficiency: 90% (at 150V input) Output short circuit protection: Included Input under voltage protection: Included PWM dimming performance: Dimensions: 5.0μs (rise time) 5.0μs (fall time) 53.7mm x 38.1mm Board Layout and Connection Diagram J5 VIN J3 J4 J2 VDD SYNC GND PWMD J1 Actual Size: 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 VOterminals 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. Doc.# DSDB-HV9911DB3 A032713 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. Supertex inc. www.supertex.com HV9911DB3 Demoboard Testing: Typical Results 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%. 1. Efficiency: The efficiency 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 efficiency of the converter at varying input voltages. The minimum efficiency of 93% for the converter occurs at 21V input and full load output. Fig. 1 Efficiency vs Output Voltage 95 Efficiency (%) Current Regulation: While the converter is operating, change the input voltage within its specifiied 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 specified limits and turn the power supply back on. The current will still be regulated at 350mA. 90 85 80 75 70 65 60 20 30 40 50 60 70 80 90 100 Output Voltage (V) 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. With Disconnect FET Efficiency (%) 96 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. Fig. 2 Efficiency vs Input Voltage 94 92 90 88 86 130 140 150 160 170 180 190 200 Input Voltage (V) With Disconnect FET 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. Without Disconnect FET Output Current (mA) 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%. 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 efficiency 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 efficiency. The following typical results section will show the results for both cases. Doc.# DSDB-HV9911DB3 A032713 Without Disconnect FET 340 Fig. 3 Output Current vs Input Voltage 339 338 337 336 335 130 140 150 160 170 180 190 200 Output Current (mA) Input Voltage (V) 338.0 Fig. 4 Output Current vs Output Voltage 337.8 337.6 337.4 337.2 337.0 20 30 40 50 60 70 80 90 100 Output Voltage (V) 2 Supertex inc. www.supertex.com HV9911DB3 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. LED Current Output Voltage Drain voltage FET Drain Voltage Fig.5a Waveforms at VIN = 150V and VO = 100V Output Current LED Current Drain voltage Fig.6 Open LED Protection 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. Fig.5a Waveforms at VIN = 200V and VO = 20V LED Current Output Voltage Drain Voltage of Q1 Drain voltage Output Current Fig.5a Waveforms at VIN = 130V and VO = 100V Fig.7 Output Short Circuit Protection Doc.# DSDB-HV9911DB3 A032713 3 Supertex inc. www.supertex.com HV9911DB3 6. PWM Dimming: Typical PWM dimming response is shown in Fig.8. Fig.9 shows the rise and Fig.10 shows the fall of the LED current on an expanded time scale. For comparison, the waveforms are shown with and without the disconnect FET. Fig.9 Rise Time for PWM Dimming Response PWM Dimming Signal Fig. 8 Typical PWM Dimming Response PWM Dimming Signal LED Current (9a) 5µs - with disconnect FET LED Current PWM Dimming Signal (8a) with disconnect FET PWM Dimming Signal LED Current (9b) 300µs - without disconnect FET Fig.10 Fall Time for PWM Dimming Response LED Current PWM Dimming Signal (8b) without disconnect FET LED Current (10a) 5µs - with disconnect FET P WM Dimming Signal LED Current (10b) 300µs - without disconnect FET Doc.# DSDB-HV9911DB3 A032713 4 Supertex inc. www.supertex.com Doc.# DSDB-HV9911DB3 A032713 5 REF F F REF F J1A J1D (GND) J2 (VIN) J5 F R9 F 17.4k R8 J1B C3 0.1μF 16V F J1C C5 0.33μF 250V Io_SNS REF 6.81k 16.2k R12 F C7 47nF 50V 8.66k R13 open R14 C4 0.33μF 250V PWM CLIM VIN U1 VDD SC R3 29.4k F CS GATE RT GND F OVP FAULT HV9911 COMP FDBK IREF REF SYNC C2 1μF 16V R4 FAULT 499Ω 604k R2 F D1 MURS140T3 F R1 0.56Ω 1/4W Q1 IRFR224 2.2mH L1 C1 0.33μF 250V GND VIN F VOUT LOAD Io_SNS U2 VSS 1.24Ω 1/4W R5 1 D2 9.1V FAULT 2 3 R17 3.65k J3 (VO-) J4 (VO+) F Q2 TN2124K1 R16 22k R18 22k Q3 IRFR9214 HV9911DB3 Circuit Schematic: Supertex inc. www.supertex.com HV9911DB3 Silk Screen Doc.# DSDB-HV9911DB3 A032713 6 Supertex inc. www.supertex.com HV9911DB3 Bill of Materials Package Manufacturer Manufacturer’s Part Number Thru-Hole Panasonic ECQ-E2334KF SMD0805 TDK Corp. C2012X7R1C105K SMD0805 Murata GRM219R71C104KA01D SMD0805 Kemet C0805C473K5RACTU SMB ON Semi MURS140T3 SOT-23 Diodes Inc. BZX84C9V1-7 Thru-Hole JST Sales Amer. S4B-EH SMT Keystone Electric 5016 SMA Coilcraft RFB1010-222L 250V, 1.1A N-Channel MOSFET Thru-Hole IR IRFR224 Q2 240V, 15Ω N-Channel MOSFET SOT-23 Supertex TN2124K1-G 1 Q3 400V, 1.8A P-Channel MOSFET DPAK IR IRFR9214 13 1 R1 0.56Ω, 1%, 1/4W chip resistor SMD1206 Panasonic ERJ-8RQFR56V 14 1 R2 604kΩ, 1%, 1/8W chip resistor SMD0805 Yageo RC0805FR-07604KL 15 1 R3 29.4kΩ, 1%, 1/8W chip resistor SMD0805 Yageo RC0805FR-0729K4L 16 1 R4 499Ω, 1%, 1/8W chip resistor SMD0805 Yageo RC0805FR-07499RL 17 1 R5 1.24Ω, 1%, 1/4W chip resistor SMD1206 Yageo RC1206FR-071R24L 18 1 R8 17.4kΩ, 1%, 1/8W chip resistor SMD0805 Yageo RC0805FR-0717K4L 19 1 R9 6.81kΩ, 1%, 1/8W chip resistor SMD0805 Yageo RC0805FR-076K81L 20 1 R12 16.2kΩ, 1%, 1/8W chip resistor SMD0805 Yageo RC0805FR-0716K2L 21 1 R13 8.66kΩ, 1%, 1/8W chip resistor SMD0805 Yageo RC0805FR-078K66L 22 1 R14 open - - - 23 1 SMD2010 Panasonic ERJ-12ZYJ223U 24 1 R17 3.65kΩ, 1%, 1/8W chip resistor SMD0805 Yageo RC0805FR-073K65L 25 1 U1 Switchmode LED Driver with High Current Accuracy SO-16 Supertex HV9911NG-G 26 1 U2 High side current monitor SOT-23 Supertex HV7800K1-G # Qty Ref Des Description 1 2 2 2 C2 3 1 C3 4 1 C7 5 1 D1 400V, 1.0A ultrafast recovery diode 6 3 D2 9.1V, 350mW zener diode 7 1 J1 Side-entry 4-Pin male header 8 4 9 1 10 2 Q1 11 1 12 C1, C4, C5 0.33μF, 100V metal film capacitors 1μF, 16V X7R ceramic chip capacitor 0.1μF, 16V X7R ceramic chip capacitor 47nF, 50V X7R ceramic chip capacitor J2, J3, J4, Compact SMT test point J5 2.2mH, 0.41A sat, 0.5A rms L1 inductor R16, R18 22kΩ, 1%, 1/2W chip resistor Supertex inc. does not recommend the use of its products in life support applications, and will not knowingly sell them for use in such applications unless it receives an adequate “product liability indemnification insurance agreement.” Supertex inc. does not assume responsibility for use of devices described, and limits its liability to the replacement of the devices determined defective due to workmanship. No responsibility is assumed for possible omissions and inaccuracies. Circuitry and specifications are subject to change without notice. For the latest product specifications refer to the Supertex inc. (website: http//www.supertex.com) Supertex inc. ©2013 Supertex inc. All rights reserved. Unauthorized use or reproduction is prohibited. Doc.# DSDB-HV9911DB3 A032713 7 1235 Bordeaux Drive, Sunnyvale, CA 94089 Tel: 408-222-8888 www.supertex.com