You will certainly has too expose the affected part to sun for adequate benefit, if you are using any treatment for 
vitiligo.  Many people use Taning bed for the for 
vitiligo treatment. But here  under there are some advice for you about tanning beds and 
vitiligo.
The ration of the radiation of  UVA to UVB in Tanning beds have a different than sunlight have. 
Another thing about the intensity that  the radiation levels are more intense, requiring individuals to limit their exposure to very brief periods.
One unanswered question is: what is the effect on the human body when it is forced to absorb such a large amount of UVA radiation in such a short amount of time? 
For example, one study found that the amount of UVA radiation, which penetrates deeper into the skin, was anywhere from about 3-8 times greater in the tanning beds than in the light from the sun.