rev. description features The VHB75W series of DC-DC converters are designed for high reliability applications, featuring over-temperature protection, over-current protection. The wide 4:1 input range (9-36V or 18-75V) is very useful to stabilize an input source like batteries in various discharging and charging conditions. Additionally, high efficiency, fast response, tight regulations, remote sense and remote On/Off control make these converters very useful in many applications. ·37.5-75W isolated output ·Efficiency to 85% ·300 kHz switching frequency ·regulated output ·continuous short circuit protection ·industry standard half-brick size ·remote on/off ·over-temperature protection ·over-current protection input voltage nominal range (V dc) (V dc) VHB75W-Q24-S3R3 VHB75W-Q24-S5 VHB75W-Q24-S12 VHB75W-Q24-S15 VHB75W-Q24-S24 VHB75W-Q24-S48 VHB75W-Q48-S3R3 VHB75W-Q48-S5 VHB75W-Q48-S12 VHB75W-Q48-S15 VHB75W-Q48-S24 VHB75W-Q48-S48 notes: 1 of 10 date date 04/2011 DESCRIPTION: half-brick dc-dc converter PART NUMBER: VHB75W MODEL page page 24 24 24 24 24 24 48 48 48 48 48 48 output voltage (V dc) 9.0~36.0 9.0~36.0 9.0~36.0 9.0~36.0 9.0~36.0 9.0~36.0 18.0~75.0 18.0~75.0 18.0~75.0 18.0~75.0 18.0~75.0 18.0~75.0 3.3 5 12 15 24 48 3.3 5 12 15 24 48 output current 1 (A) 15 15 6.25 5 3.12 1.56 15 15 6.25 5 3.12 1.56 input current no load 2 full load 2 (mA) (mA) 50 50 50 50 50 50 50 50 50 50 50 50 2611 3811 3765 3720 3720 3811 1320 1905 1860 1860 1860 1860 efficiency typ. 3 (%) 79 82 83 84 84 82 80 83 84 85 85 84 1. see output derating (page 4) 2. input currents are measured at nominal input voltage 3. efficiency is measured at nominal line, full load INPUT parameter input voltage range conditions/description under voltage lockout remote on/off control 4 24 Vin power up 24 Vin power down 48 Vin power up 48 Vin power down section 15 in the application notes input filter PI type notes: min 9 18 nom 24 48 8.8 8 17 16 max 36 75 units V dc V dc V dc V dc V dc V dc 4. add suffix “N” to the model number for negative logic on/off control *V-Infinity reserves the right to make changes to its products or to discontinue any product or service without notice, and to advise customers to verify the most up-todate product information before placing orders. V-Infinity assumes no liability or responsibility for customer’s applications using V-Infinity products other than repair or replacing (at V-I’s option) V-Infinity products not meeting V-I’s published specifications. Nothing will be covered outside of standard product warranty. 20050 SW 112th Ave. Tualatin, Oregon 97062 phone 503.612.2300 fax 503.612.2383 www.v-infinity.com page 2 of 10 date 04/2011 DESCRIPTION: half-brick dc-dc converter PART NUMBER: VHB75W OUTPUT parameter voltage accuracy transient response external trim adj. range ripple & noise (20MHz BW) conditions/description min nom 25% step load change 3.3V, 5V 12V& 15V 24V 48V temperature coefficient short circuit protection continuous line regulation 5 load regulation 6 over voltage protection trip range, % Vo nom. over current protection % nominal output current max ±1 <500 ±10 40 100 60 150 100 240 200 480 units % μ sec % mV RMS mV p-p mV RMS mV p-p mV RMS mV p-p mV RMS mV p-p %/°C ±0.2 ±0.2 140 160 % % % % max units KHz °C °C °C ±0.03 115 110 GENERAL SPECIFICATIONS parameter switching frequency operating ambient temp. 7 storage temperature thermal shutdown case temp. case material conditions/description min nom 300 -40 -55 100 105 100 aluminum ISOLATION SPECIFICATIONS parameter isolation voltage conditions/description input/output input/case min 1500 1500 output/case 1500 100 isolation resistance notes: 5. 6. 7. nom max units V dc V dc V dc MΩ measured from high line to low line at full load measured from full load to zero load at nominal input see output derating curve (page 4) *V-Infinity reserves the right to make changes to its products or to discontinue any product or service without notice, and to advise customers to verify the most up-todate product information before placing orders. V-Infinity assumes no liability or responsibility for customer’s applications using V-Infinity products other than repair or replacing (at V-I’s option) V-Infinity products not meeting V-I’s published specifications. Nothing will be covered outside of standard product warranty. 20050 SW 112th Ave. Tualatin, Oregon 97062 phone 503.612.2300 fax 503.612.2383 www.v-infinity.com PART NUMBER: VHB75W page 3 of 10 date 04/2011 DESCRIPTION: half-brick dc-dc converter MECHANICAL DRAWING 20050 SW 112th Ave. Tualatin, Oregon 97062 phone 503.612.2300 fax 503.612.2383 www.v-infinity.com PART NUMBER: VHB75W page 4 of 10 date 04/2011 DESCRIPTION: half-brick dc-dc converter APPLICATION NOTES 1. OUTPUT DE-RATING The operating case temperature range for VHB75W is -40 ~ +100°C. When operating the VHB75W series, proper derating or cooling is needed. The maximum case temperature under any operating condition should not exceed 100°C. Power Dissipated vs Ambient Temperature and Air Flo w Power Disspated ,Pd(Watts) Natural Convection 20 ft./min. (0.1 m/s) 100 ft./min. (0.5 m/s) 200 ft./min. (1.0 m/s) 300 ft./min. (1.5 m/s) 400 ft./min. (2.0 m/s) 500 ft./min. (2.5 m/s) 600 ft./min. (3.0 m/s) 700 ft./min. (3.5 m/s) 800 ft./min. (4.0 m/s) Ambient Temperature ,Ta(Deg. C) FIGURE 1. OUTPUT DERATING (FORCED CONVECTION WITH NO HEAT SINK) Example: What is the minimum airflow necessary for a VHB75W-Q48-S12 operating at nominal line, an output current of 6.25 A, and a maximum ambient temperature of 40°C? Solution: Given: Vin=48 V dc, Vo=12 V dc, Io=6.25 A Determine Power dissipation (Pd): Pd=Pi-Po=Po(1-η)/η Pd=12×6.25×(1-0.84)/0.84=14.29 W Determine airflow: Given: Pd=14.29 W and Ta=40°C Check above Power de-rating curve: minimum airflow= 400 ft./min. Verifying: AIR FLOW RATE Natural Convection 20ft./min. (0.1m/s) TYPICAL Rca 7.12 /W 100 ft./min. (0.5m/s) 6.21 /W 200 ft./min. (1.0m/s) 5.17 /W 300 ft./min. (1.5m/s) 4.29 /W 400 ft./min. (2.0m/s) 3.64 /W 500 ft./min. (2.5m/s) 2.96 /W 600 ft./min. (3.0m/s) 2.53 /W 700 ft./min. (3.5m/s) 2.37 /W 800 ft./min. (4.0m/s) 2.19 /W Chart of Thermal Resistance vs Air Flow The maximum temp. rise ΔT = Pd × Rca=14.29×3.64=52.02°C. The maximum case temperature Tc=Ta+ΔT=92.02°C<100°C Where: The Rca is thermal resistance from case to ambience.The Ta is ambient temperature and the Tc is case temperature. 20050 SW 112th Ave. Tualatin, Oregon 97062 phone 503.612.2300 fax 503.612.2383 www.v-infinity.com page 5 of 10 date 04/2011 DESCRIPTION: half-brick dc-dc converter PART NUMBER: VHB75W 2. INPUT VOLTAGE RANGE It is important to ensure the input voltage measured at the converter input pins is within the range for that converter. Make sure wire losses and voltage ripples are accounted for. One possible problem is driving the converter with a linear unregulated power supply. For example, if the average voltage measured by a DMM is 9V, with a voltage ripple of 3Vpp, the actual input can swing from 7.5V to 10.5V. This will be outside the specified input range of 9-36V and the converter may not function properly. On the other end, make sure the actual input voltage does not exceed the highest voltage of 36V or 75V. 3. LEAD WIRES Make sure the input and output wires are of adequate AWG size to minimize voltage drop, and ensure the voltage across the input terminals is above the converter's rated minimum voltage at all times. It is recommended to have the wire pairs twisted, respectively for the input pair and the output pair, so as to minimize noise pickup. 4. INPUT CURRENT The input voltage source must be able to provide enough current to the converter, otherwise it may not start up or operate properly. A typical symptom is not starting or unusually low output voltage. In general, it is recommended to be able to provide at least: η *Vmin) where Pout is the maximum output power, Vmin is the minimum input voltage and η is the converter's Ipeak = 150%*Pout/(η efficiency. As an example, for VHB75W-Q24-S5 to operate with 9~36 V input, 75 W output and an efficiency of 82%, the minimum source current is recommended to be: Ipeak = 150% * 75 / (82% * 9) = 15.24 A. 5. INPUT FUSE To limit the input current and to facilitate input reversal protection and input OVP protection, a fast-acting input fuse is recommended for the input line. The fuse rating will depend on the input range and should allow for the maximum current at the lowest input voltη *Vmin). age, as shown in this equation: Ipeak = 150%*Pout/(η In the previous example of VHB75W-Q24-S5, the peak input current at 9V was calculated to be 15.24 A. A 20 A fuse may be suitable for this application. Make sure the fuse voltage rating is higher than the maximum input voltage. 6. REMOTE SENSE The converter provides regulated outputs at the output terminals. When there is a large current and/or the output cable is of some length, the voltage at the end of the output cable may be noticeably lower than at the terminals. The converter can compensate up to 0.5V of voltage drop through remote sense terminals. To ensure accurate regulation, run two separate wires (twisted) from the desired regulation points to the remote sense terminals, as shown below. Even if the load current is low, still connect +Vo to +S and -Vo to -S. +Vo +S (+) Load Trim (-) -S -Vo FIGURE 2. REMOTE SENSE 20050 SW 112th Ave. Tualatin, Oregon 97062 phone 503.612.2300 fax 503.612.2383 www.v-infinity.com page 6 of 10 date 04/2011 DESCRIPTION: half-brick dc-dc converter PART NUMBER: VHB75W 7. OUTPUT TRIMMING (OPTIONAL) The output voltages are preset to nominal values as indicated by the models table at the factory. If desired, the output voltage may optionally be trimmed to a different value (+/- 10%) with external resistors and/or potentiometer as shown below. +Vo +Vin +S FIGURE 3. TRIMMING WITH 10KΩ Trimpot Trim EXTERNAL POTENTIOMETER R load -S -Vin -Vo To trim the output voltage with fixed resistors, the output voltage can be calculated as follows. Trim-Up +Vin Trim-Down +Vo +Vin +Vo R trim-down Trim Trim R load R load R trim-up -Vin -Vo -Vin -Vo FIGURE 4: TRIM-UP VOLTAGE SETUP FIGURE 5: TRIM-DOWN VOLTAGE SETUP The value of R trim-up is defined as: The value of R trim-down is defined as: Rtrim-up = R1 - R2 x (Vo - Vo, nom) (KΩ) Vo - Vo, nom Rtrim-down = R1 - R2 x (Vo, nom - Vo) (KΩ) Vo, nom - Vo Where: R trim-up is the external resistor in K Ω . V o,nom is the Where: R trim-down is the external resistor in K Ω . V o,nom is the nominal output voltage. V o is the desired output voltage. R 1 , nominal output voltage. V o is the desired output voltage. R 1 , R 2 , R 3 , V r , and V f are internal to the unit and are defined in R 2 , and V r are internal to the unit and are defined in Table 1. For example, to trim-up the output voltage of 5.0V Table 1. For example, to trim-up the output voltage of 5.0V module (VHB75W-Q48-S5) by 8% to 5.4V, R trim-up is calculated module (VHB75W-Q48-S5) by 8% to 4.6V, R trim-down is calculated as follows: Vo - Vo, nom = 5.4 - 5.0 = 0.4 V as follows: Vo, nom - Vo = 5.0 - 4.6 = 0.4 V R1 = 5.8 KΩ R1 = 5.8 KΩ R2 = 8.2 KΩ R2 = 10.52 KΩ Rtrim-up = Table 1 3.3V 5V 12V 15V 24V 48V 5.8 - 8.2 x 0.4 = 6.3 (KΩ) 0.4 Ω 3.168 5.8 19.656 25.474 42.33 74.514 Ω 7.2 8.2 13.304 14.76 16.67 13.0476 Rtrim-down = Table 2 3.3V 5V 12V 15V 24V 48V 5.8 - 10.52 x 0.4 = 3.98 (KΩ) 0.4 Ω 6.18 5.8 86.45 150 430 1569.6 20050 SW 112th Ave. Tualatin, Oregon 97062 phone 503.612.2300 fax 503.612.2383 Ω 15 10.52 60.1 94 120 295.527 www.v-infinity.com page 7 of 10 date 04/2011 DESCRIPTION: half-brick dc-dc converter PART NUMBER: VHB75W 8. OUTPUT OCP AND SHORT-CIRCUIT PROTECTION Output overload and short circuit conditional will cause the output voltage to decline or shutdown altogether. If the case temperature is not over 100°C, the output recovers automatically when the short or OCP conditions are removed. In the case of slight overloading, the output voltage may not shut down, but the converter may build up heat over time, causing over-temperature shutdown. 9. OVER-TEMPERATURE PROTECTION When the case temperature reaches about 100°C, the converter's built-in protection circuit will shut down the output. When the temperature is reduced enough to a safe operating level, the converter will recover to normal operations automatically. 10. OUTPUT OVP In case the output voltage exceeds the OVP threshold, the converter shuts down. 11. OUTPUT PARALLEL CONNECTIONS The converter is not designed for load share on the output. One may be inclined to use this circuit to force current sharing by trimming the output voltages for each converter. However, this circuit may not reliably or accurately divide the load current, as the device characteristics of the converters or the diodes may not be balanced over a range of operating conditions. We generally do not recommend this circuit to increase power output over a single converter. Instead, we recommend this setup for redundancy only, having one converter as a backup in case of a failure. Make sure the OR-ing diodes can handle the voltage and full load current. +Vin -Vin FIGURE 6. OUTPUT +Vo -Vo PARALLEL CONNECTIONS +Vin -Vin +Vo -Vo 20050 SW 112th Ave. Tualatin, Oregon 97062 phone 503.612.2300 fax 503.612.2383 www.v-infinity.com page 8 of 10 date 04/2011 DESCRIPTION: half-brick dc-dc converter PART NUMBER: VHB75W 12. OUTPUT SERIES CONNECTIONS Two or more converters can be connected in series to obtain a higher output voltage. To prevent output reverse biasing each other in case of a short, add a Schottky diode on each output in reverse polarity, as shown in the diagram. In the event of a short, the converters will forward-bias the diodes and the output reversal will be limited to one diode drop (about 0.5V) only, so as not to damage the converters. The forward current will cause each converter to go into short-circuit protection. For proper diode selection, make sure that: 1) the diodes voltage rating is higher than each converter output; 2) the rated diode current can carry the short-circuit current; 3) the diodes do not overheat before the short is removed. +Vin -Vin FIGURE 7. OUTPUT +Vo -Vo SERIES CONNECTIONS +Vin -Vin +Vo -Vo 13. REMOTE OUTPUT ON/OFF CONTROL The converter output can be enabled or disabled through the On/Off pin. The control logic is shown in this table. A common control circuit is shown below. The standard version defaults to positive logic. For negative logic, indicate the selection when ordering. REM REM (pin 2) +Vo SW SW High signal here disable output -Vin -Vin (pin 4) -Vo FIGURE 8. REMOTE ON/OFF CONTROL FIGURE 9. REMOTE ON/OFF CONTROL WITH TRANSISTOR SWITCH Logic Table Negative logic SW Closed (V REM <0.8 V) Output on SW Open (V REM >2.4 V) Output off Positive logic Output off Output on 14. ISOLATION The input and output of the converter are electrically isolated. If needed, an output terminal can be connected to an input terminal, resulting in the converter non-isolated. 20050 SW 112th Ave. Tualatin, Oregon 97062 phone 503.612.2300 fax 503.612.2383 www.v-infinity.com page 9 of 10 date 04/2011 DESCRIPTION: half-brick dc-dc converter PART NUMBER: VHB75W 15. INPUT FILTERING AND EMI INTERFERENCE The VHB75W converters have input capacitors that control input current ripple and the associated EMI interference. However, it has not been tested to a formal standard for conducted emissions. Additional filtering may be needed to ensure compliance to an EMI standard. Refer to FIGURE 10 for a reference circuit. V-Infinity offers a line of dc input filter modules designed to help reduce common and differential mode noise. The table below provides a list of dc-dc converter models within the series and the mating dc input filter. Series Mating Filter Module VHB75W-Q24-SXX VFM-10A VHB75W-Q48-SXX VFM-10A Notes FIGURE 10. EMI FILTER FOR VHB75W L2 C2 +Vin +Vo -Vin CASE -Vo C3 C4 VHB75W Series C2 47µF/50V EMI to meet class A ESR<0.60 220µF/50V EMI to meet class B ESR<0.120 C3 47µF/50V ESR<0.60 220µF/50V ESR<0.120 C4 2200pF/2KV L2 2.5µH 2200pF/2KV 1.5µH note: The recommended components are a starting point but not guaranteed for meeting these EMI requirements. More or less filtering may be required for a specific application or to meet other EMI standards, e.g.MIL-STD-461 20050 SW 112th Ave. Tualatin, Oregon 97062 phone 503.612.2300 fax 503.612.2383 www.v-infinity.com page 10 of 10 date 04/2011 DESCRIPTION: half-brick dc-dc converter PART NUMBER: VHB75W 16. OUTPUT FILTERING The converter has built-in capacitors at the output to control ripple and noise. If desired, additional output capacitance can be introduced at the input to the powered equipment. Recommended starting point: one 10μF tantalum and one 1μF ceramic capacitor in parallel at the output. 17. OUTPUT NOISE MEASUREMENT SCHEMATIC For proper output ripple and noise measurement, connect a 10μF tantalum and a 1μF ceramic capacitor across the output. Set the scope bandwidth to 20MHz. Probe directly off of one of the capacitors, using a small ground clip to minimize measurement error. +Vin +Vo Ceramic 1.0µF +S Trim + Resistor Load -S -Vin -Vo Solid Tantalum 10µF To Scope FIGURE 11. OUTPUT NOISE MEASUREMENT CIRCUIT 20050 SW 112th Ave. Tualatin, Oregon 97062 phone 503.612.2300 fax 503.612.2383 www.v-infinity.com