Datasheet

Application Note
Created by Traco Electronic AG Arp. www.tracopower.com Date: June 9
th
, 2010 / Rev.: 1.2 / Page 54 / 63
100W Single Output
Remote Sense
To minimum the effects of distribution losses by regulating the voltage at the Remote Sense pin. The voltage between the
Sense pin and V
out
pin must not exceed 10% of V
out
. i.e. [+V
out
to –V
out
] – [+Sense to –Sense] < 10% V
out
The voltage between +V
out
and –V
out
terminals must not exceed the minimum output over voltage protection threshold. This limit
includes any increase in voltage due to remote-sense compensation and trim function.
If not using the remote-sense feature to regulate the output at the point of load, then connect +Sense to +V
out
and –Sense
to –V
out
.
Remote Sense circuit configuration
Input Source Impedance
The power module should be connected to a low impedance input source. Highly inductive source impedance can affect the
stability of the power module. Input external π filter is recommended to minimize input reflected ripple current. The inductor is
simulated source impedance of 12µH and capacitor is Nippon Chemi-con KY series 100µF/100V. The capacitor must as close
as possible to the input terminals of the power module for lower impedance.
Output Over Current Protection
When excessive output currents occur in the system, circuit protection is required on all power supplies. Normally, overload
current is maintained at approximately 110~140 percent of rated current for TEP 100 Series.
Hiccup-mode is a method of operation in a power supply whose purpose is to protect the power supply from being damaged
during an over-current fault condition. It also enables the power supply to restart when the fault is removed. There are other
ways of protecting the power supply when it is over-loaded, such as the maximum current limiting or current foldback methods.
One of the problems resulting from over current is that excessive heat may be generated in power devices; especially MOSFET
and Shottky diodes and the temperature of those devices may exceed their specified limits. A protection mechanism has to be
used to prevent those power devices from being damaged.
The operation of hiccup is as follows. When the current sense circuit sees an over-current event, the controller shuts off the
power supply for a given time and then tries to start up the power supply again. If the over-load condition has been removed, the
power supply will start up and operate normally; otherwise, the controller will see another over-current event and shut off the
power supply again, repeating the previous cycle. Hiccup operation has none of the drawbacks of the other two protection
methods, although its circuit is more complicated because it requires a timing circuit. The excess heat due to overload lasts for
only a short duration in the hiccup cycle, hence the junction temperature of the power devices is much lower.
The hiccup operation can be done in various ways. For example, one can start hiccup operation any time an over-current event
is detected; or prohibit hiccup during a designated start-up is usually larger than during normal operation and it is easier for an
over-current event is detected; or prohibit hiccup during a designated start-up interval (usually a few milliseconds). The reason
for the latter operation is that during start-up, the power supply needs to provide extra current to charge up the output capacitor.
Thus the current demand during start-up is usually larger than during normal operation and it is easier for an over-current event
to occur. If the power supply starts to hiccup once there is an over-current, it might never start up successfully. Hiccup mode
protection will give the best protection for a power supply against over current situations, since it will limit the average current to
the load at a low level, so reducing power dissipation and case temperature in the power devices.