Well, this is a yoga in your birth-chart which depends on the locations of the planets involved. I have researched various articles and few books available on the internet here. There are articles which has a very long list of the combinations of the planets for the occurrence of this Yoga. I will put here some specific which makes real sense.
First of all, Neecha-Bhanga Yoga means the cancellation of the debilitation of a debilitated planet. We know Sun is debilitated in Libra, Mars in Cancer, Mercury in Pisces, Venus in Virgo, Jupiter in Capricorn and Saturn in Aries. When a planet is debilitated, it gives us bad results by harming the house in which it is situated. Along with that this planet will not be able to handle the affairs of the houses of its own rulership.
Now there are some specific combinations of the planetary positions in your birth chart when the debilitation gets cancelled. In case of the cancellation of the debilitation or Neecha-Bhanga a Raj Yoga is formed, which gives its native power, name and fame.
So, what are those combinations of the planetary positions in your birth-chart?.. well here is the list:
- There are 4 Kendra houses in your birth-chart i.e. 1st, 4th, 7th and 10th house. When the lord of the sign of debilitation of a planet is placed in the Kendra house. Let me give you an example, Venus is debilitated in Virgo and Mercury being the lord of Virgo is placed either in the 1st, 4th, 7th or 10th house in your birth-chart.
- The exaltation lord of the debilitated planet is located in Kendra from Lagna or the Moon.
- The debilitated planet exchanges the houses with its debilitation lord. For example, Sun is placed in Libra and Venus in Leo.
- The debilitated planet is associated with or aspected by the debilitation lord.
- Two debilitated planets aspects each other.
"Elements of Vedic Astrology" by K.S.Charak and various other articles available on internet, I can't be specific, they all helped.