SLUA110 Datasheet, PDF (18/19 Pages) Texas Instruments – PRACTICAL CONSIDERATIONS IN CURRENT MODE POWER SUPPLIES

APPLICATION NOTE
Other factors contributing to mismatch of output power are
the individual power supply diode voltage drops. The out-
put choke inductance reflects back to the primary current
sense, and any tolerances associated with it will alter the
primary current slope, hence current. In the control sec-
tion, the peak-to-peak voltage swing at the timing capacitor
Ct effects the amount of slope compensation introduced,
along with the tolerance of the summing resistor These
must all be accounted for to calculate the actual worst case
current sharing capability of the circuit.
U-111
Cables should be of equal length, originating at the
master and routed away from any noise sources, like the
high voltage switching section. All input and output power
leads should be exactly the same length and wire gauge,
connected together at ONE single point. Leads should be
treated as resistors in series with the load, and deviations
in length will result in different currents delivered from each
module.
Top Trace:
VE: Error Voltage
with Noise
Lower Trace:
VR: Primary
Current
PARALLEL
OPERATION
EQUAL LEAD
LENGTHS FROM
MASTER AND
SLAVE(S) TO ALL
CONNECTIONS
Figure 48.
Figure 47. Noise Modulating VE
Proper layout of all interconnecting wires is required to
insure optimum performance. Shielded coax cable is
recommended for distributing the error voltage among the
modules. Any noise on this line will demonstrate its impact
at the PWM comparator, resulting in poor load sharing, or
jitter.
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