  We have used pulsed magnetic fields up to 60Tesla to suppress the
contribution of superconducting fluctuations(SCF)to the conductivity above Tc
in a series of YBa2Cu3O6+x from the deep pseudogapped state to slight
overdoping. Accurate determinations of the SCF conductivity versus temperature
and magnetic field have been achieved. Their joint quantitative analyses with
respect to Nernst data allow us to establish that thermal fluctuations
following the Ginzburg-Landau(GL) scheme are dominant for nearly optimally
doped samples. The deduced coherence length xi(T) is in perfect agreement with
a gaussian (Aslamazov-Larkin) contribution for 1.01Tc<T<1.2Tc. A phase
fluctuation contribution might be invoked for the most underdoped samples in a
T range which increases when controlled disorder is introduced by electron
irradiation. For all dopings we evidence that the fluctuations are highly
damped when increasing T or H. The data permits us to define a field Hc^prime
and a temperature Tc^prime above which the SCF are fully suppressed. The
analysis of the fluctuation magnetoconductance in the GL approach allows us to
determine the critical field Hc2(0). The actual values of Hc^prime(0) and
Hc2(0) are found quite similar and both increase with hole doping. These
depairing fields, which are directly connected to the magnitude of the SC gap,
do therefore follow the Tc variation which is at odds with the sharp decrease
of the pseudogap T* with increasing hole doping. This is on line with our
previous evidence that T* is not the onset of pairing. We finally propose a
three dimensional phase diagram including a disorder axis, which allows to
explain most peculiar observations done so far on the diverse cuprate families.
