psb245-7ir Power-One, psb245-7ir Datasheet - Page 5

• Manufacturer Part Number: psb245-7ir
• Description: Psb Series Extended Positive Switching Regulator Industrial
• Manufacturer: Power-One

I
Thermal Considerations
When a switching regulator is located in free, quasi-station-
ary air (convection cooling) at a temperature T
is operated at its nominal output current I
temperature T
phase, measured at the Measuring point of case tempera-
ture T
Under practical operating conditions, the ambient tem-
perature T
ures (heat sink, fan, etc.) are taken to ensure that the case
temperature T
95 °C.
Example: Sufficient forced cooling allows T
simple check of the case temperature T
load ensures correct operation of the system.
Fig. 4
Output current derating versus temperature
Output Protection
A voltage suppressor diode which in worst case conditions
fails into a short circuit, (or a thyristor crowbar, option C)
protects the output against an internally generated over-
voltage. Such an overvoltage could occur due to a failure of
either the control circuit or the switching transistor. The out-
put protection is not designed to withstand externally ap-
plied overvoltages. The user should ensure that systems
with Power-One power supplies, in the event of a failure, do
not result in an unsafe condition (fail-safe).
REV. OCT 17, 2003
V
o
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
1
0
o
/ I
0
I
o nom
o
T
/ I
A min
o nom
C
(see: Mechanical Data ).
V od
A
may exceed 71°C, provided additional meas-
50
Convection cooling
C
C
does not exceed its maximum value of
will be about 95°C after the warm-up
10 µs
t
d
60
70
Forced cooling
D V
o I
V od
80
C
90
( T
10 µs
o nom
A max
C
t
d
A
95°C) at full
100
= 71°C and
, the case
T
= 85°C. A
C max
T
A
D V
[˚C]
Page 5 of 13
05010
o I
t
t
Positive Switching Regulator (Industrial)
Fig. 3
Dynamic load regulation.
Parallel and Series Connection
Outputs of equal nominal voltages can be parallel-con-
nected. However, the use of a single unit with higher output
power, because of its power dissipation, is always a better
solution.
In parallel-connected operation, one or several outputs may
operate continuously at their current limit knee-point which
will cause an increase of the heat generation. Conse-
quently, the max. ambient temperature value should be re-
duced by 10 K.
Outputs can be series-connected with any other module. In
series-connection the maximum output current is limited by
the lowest current limitation. Electrically separated source
voltages are needed for each module!
Short Circuit Behaviour
A constant current limitation circuit holds the output current
almost constant whenever an overload or a short circuit is
applied to the regulator's output. It acts self-protecting and
recovers – in contrary to the fold back method – automati-
cally after removal of the overload or short circuit condition.
Fig. 5
Overload, short-circuit behaviour V
1.2
1.0
0.8
0.6
0.4
0.2
V
o
0
/ V
o nom
PSB Series Extended Data Sheet
0.2
0.4
0.6
0.8
1.0
o
versus I
I
o L
1.2
o
05043
1.4
I
o
/ I
o nom