The total load-share loop unity-gain
crossover frequency, fCO, must be set at least one decade below the
lowest measured crossover frequency of the paralleled modules previously measured,
fCO(module) (see Figure 7-5). Compensation of the transconductance error amplifier is accomplished by
connecting a compensation resistor, REAO, in series with a capacitor,
CEAO, between EAO and GND. Use Equation 8 and Equation 13 to calculate the values of these components. CEAO is calculated
first.
Equation 8.
where
- gM is the
transconductance of the Error Amplifier, typically 14mS.
- fCO is the targeted
crossover frequency of the load-share loop, minimally fCO(module)/10,
preferably even lower
- ACSA is the DC gain of
the Current-Sense Amplifier. (R15, R16 refer to Figure 7-1.)
- AV is the maximum
voltage gain.
- AADJ is the gain
associated with the Adjust amplifier.
- |APWR(fCO)|
is the measured gain of the power module at the targeted load-share crossover
frequency, fCO, converted from dB to V/V.
Equation 9.
Equation 10.
Equation 11.
Equation 12.
where
- GMODULE(fCO) is the measured value of the gain (in dB)
from Figure 7-5, at the targeted load-share crossover frequency.
After the value of the CEAO
capacitor is determined, the REAO value is calculated to achieve the
desired current-sharing loop response using Equation 13.
Equation 13.