The Neech Bhang Rajyoga means the cancellation of debilitated state of a planet. Usually, planets are considered weak, if they occupy their debilitated zodiac sign.
I stand to be corrected; but, I could not find any mention of Neech Bhanga Raj Yoga in Brihad Parashara Hora Shashtra. The Phala Deepika and Sarawali, however, do contain information about the planetary placement, wherein the strength is obtained by planets in their debilitation sign. There are many different and even controversial thoughts of eminent astrologers about the Neech Bhanga Raj Yoga. As per Phaladeepkia, some of the potent planetary placements, generating the Neech Bhang Raj Yoga are mentioned below: