2. input currents are measured at nominal input voltage
3. efficiency is measured at nominal line, full load
INPUT
parameter
input voltage range
under voltage lockout
24 Vin power up
24 Vin power down
48 Vin power up
48 Vin power down
remote on/off control
4
input filter
notes:
conditions/description
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
section 15 in the application notes
PI type
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-to-
date 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
112
th
Ave. Tualatin, Oregon
97062
phone
503.612.2300
fax
503.612.2382
page
date
2 of 10
10/2008
PART NUMBER:
VHB50W
DESCRIPTION:
half-brick dc-dc converter
OUTPUT
parameter
voltage accuracy
transient response
external trim adj. range
ripple & noise (20MHz BW)
conditions/description
25% step load change
3.3V, 5V
12V& 15V
24V
temperature coefficient
short circuit protection
continuous
5
line regulation
load regulation
6
over voltage protection trip range, % Vo nom.
over current protection
% nominal output current
±0.03
±0.2
±0.2
140
160
min
nom
max
±1
<500
±10
40
100
60
150
100
240
units
%
µ sec
%
mV RMS
mV pk-pk
mV RMS
mV pk-pk
mV RMS
mV pk-pk
%/°C
%
%
%
%
115
110
GENERAL SPECIFICATIONS
parameter
switching frequency
operating ambient temp.
7
storage temperature
thermal shutdown case temp.
case material
conditions/description
min
-40
-55
100
aluminum
nom
300
max
100
105
units
KHz
°C
°C
°C
ISOLATION SPECIFICATIONS
parameter
isolation voltage
conditions/description
input/output
input/case
output/case
isolation resistance
notes:
5.
6.
7.
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)
min
1500
1500
1500
100
nom
max
units
V dc
V dc
V dc
MΩ
*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-to-
date 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
112
th
Ave. Tualatin, Oregon
97062
phone
503.612.2300
fax
503.612.2382
page
date
3 of 10
10/2008
PART NUMBER:
VHB50W
DESCRIPTION:
half-brick dc-dc converter
MECHANICAL DRAWING
20050
SW
112
th
Ave. Tualatin, Oregon
97062
phone
503.612.2300
fax
503.612.2382
page
date
4 of 10
10/2008
PART NUMBER:
VHB50W
DESCRIPTION:
half-brick dc-dc converter
APPLICATION NOTES
1. OUTPUT DE-RATING
The operating case temperature range for VHB50W is -40 ~ +100°C. When operating the VHB50W 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
Natural Convection
20 ft./min. (0.1 m/s)
100 ft./min. (0.5 m/s)
Power Disspated ,Pd(Watts)
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 VHB50W-Q48-S12
operating at nominal line, an output current of 4.16 A, and a
maximum ambient temperature of 60°C?
Solution:
Given: Vin=48 V dc, Vo=12 V dc, Io=4.16 A
Determine Power dissipation (Pd):
Pd=Pi-Po=Po(1-η)/η
Pd=12×4.16×(1-0.84)/0.84=9.51 W
Determine airflow:
Given: Pd=9.51 W and Ta=60°C
Check above Power de-rating curve:
minimum airflow= 400 ft./min.
Verifying:
AIR FLOW RATE
Natural Convection
20ft./min. (0.1m/s)
100 ft./min. (0.5m/s)
200 ft./min. (1.0m/s)
300 ft./min. (1.5m/s)
400 ft./min. (2.0m/s)
500 ft./min. (2.5m/s)
600 ft./min. (3.0m/s)
700 ft./min. (3.5m/s)
800 ft./min. (4.0m/s)
TYPICAL Rca
7.12
6.21
5.17
4.29
3.64
2.96
2.53
2.37
2.19
/W
/W
/W
/W
/W
/W
/W
/W
/W
Chart of Thermal Resistance vs Air Flow
The maximum temp. rise
∆T
= Pd × Rca=9.51×3.64=34.6°C. The maximum case temperature Tc=Ta+∆T=94.6°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
112
th
Ave. Tualatin, Oregon
97062
phone
503.612.2300
fax
503.612.2382
page
date
5 of 10
10/2008
PART NUMBER:
VHB50W
DESCRIPTION:
half-brick dc-dc converter
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
Ipeak = 150%*Pout/(η *Vmin)
where Pout is the maximum output power, Vmin is the minimum input voltage and
η
is the converter's
efficiency. As an example, for VHB50W-Q24-S5 to operate with 9~36 V input, 50 W output and an efficiency of 81%, the minimum
source current is recommended to be:
Ipeak = 150% * 50 / (81% * 9) = 10.29 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 volt-
η
age, as shown in this equation:
Ipeak = 150%*Pout/(η *Vmin).
In the previous example of VHB50W-Q24-S5, the peak input current at 9V was calculated to be 10.29 A. A 15 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.
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