  The vortex-lattice melting line in three-dimensional type-II superconductors
with pinning is derived by equating the free energies of the vortex system in
the solid and liquid phases. We account for the elastic and pinning energies
and the entropy change that originates from the disappearance of the phonon
shear modes in the liquid. The pinning is assumed to be caused by point defects
and to be not too strong so that the melting line lies inside the so-called
bundle-pinning region. We show that the derived equation for the melting line
is equivalent to some Lindemann criterion, which however differs from that used
previously. Estimating the effect of pinning on the entropy jump at melting, we
find the upper critical point of the melting line from the condition that this
jump vanishes. We also consider the H-T phase diagrams of type-II
superconductors for different strengths and types of pinning and analyze the
two recently discussed scenarios how the melting line and the order--disorder
line merge.
