Parallel And Serial Mode; Multi-Quadrant Operation; Fig. 6.8: Example For Serial Mode; Fig. 6.9: Example For Parallel Mode - R&S HMC804x Benutzerhandbuch

Advanced Operating Functions
6 .6

Parallel and Serial Mode

It is assumed that only qualified and trained personnel service the
power supplies and the connected consumers.
To increase output voltage and currents, it is possible
to operate the channels in serial or parallel mode. These
operating modes require that power supplies are suitable
for the parallel and/or serial mode. In general, the output
voltages to be combined are independent. The outputs for
one or multiple power supplies can be interconnected for
this purpose.
A serial connection may cause dangerous voltages.
6 .6 . 1 Serial Mode
This type of interconnection adds the individual output
voltages. The same current flows through all outputs. The
current limits for the outputs wired in series should be set
to the identical value. If one of the outputs exceeds the
current limit, the total voltage will naturally collapse. It is
advisable to set both voltages to a similar value to distri-
bute the loads evenly (not absolutely necessary). If a (low
resistance) load is connected, it is essential to activate
more than one channel. This could damage the instrument
(especially protective diodes). Therefore, it is necessary to
always have both channels or no channel at all switched
on.
If the instrument switches to constant current operating mode
(CC) during a serial connection, the voltage display becomes inac-
curate.
32 V
1 A
CH1

Fig. 6.8: Example for serial mode

6 .6 .2 Parallel Mode
If it is necessary to increase the total current, the power
supply outputs must be wired in parallel. The output volt-
ages for the individual outputs should be set to the same
voltage value as precisely as possible. For slight voltage
differences, it is common in this operating mode to first
charge a voltage output up to the current limit; the other
voltage output provides the remaining current. The maxi-
mum total current is the sum of the individual currents of
all sources connected in parallel. For power supplies that
are connected in parallel, It is possible that compensating
currents flow within the power supplies. The use of power
supplies by other manufacturers, which are potentially not
54
32 V
1 A
CH2 CH3
64 V
1 A
overload proof, can cause destruction of these units as
currents may be distributed unevenly.
16 V
2 A
CH1
16 V
4 A

Fig. 6.9: Example for parallel mode

Generally, a higher current will first be supplied from the
channel with the higher output voltage. Once this channel
reaches its power limit, the remaining current will be made
available by the channel that is connected in parallel. In
this scenario, it is unpredictable which channel will supply
the higher current because it is also possible for channels
with identical voltage values to display a low voltage
difference. If you distribute the load to multiple channels, it
is recommended to set the current limit of the channel that
is to supply the main current to a fraction of the current.
This approach handles the semiconductor with care and
improves the heat dissipation, as the power loss is distri-
buted more evenly.
By increasing the voltage slightly, the load distribution can be
manipulated. If the voltage for a channel is to be increased by
50mV, for instance (by a set of identical cables), the current will
initially be provided by this channel.
6 .7

Multi-Quadrant Operation

Fig. 6.10: Power supply quadrants diagram

In general, operating in multi-quadrant mode requires a
multi-quadrant power supply. The R&S®HMC804x is only a
1-quadrant power supply which is able to provide positive
voltage or positive current (quadrant I). However, a nega-
tive voltage can be generated by means of a special con-
nection of two channels (common GND). Fig. 6.8 shows a
connection example for a R&S®HMC8043, the connection
for the R&S®HMC8042 is identical.
16 V
2 A
CH2 CH3