Google has thoughtfully provided electronic pages of a book called, Our Great Qing: The Mongols, Buddhism, and the State in Late Imperial China, written by scholar Johan Elverskog, and published by the University of Hawai'i in 2006. You will find it useful to understand the connection.
In the first chapter, Elverskog opens by describing a scene in 1626, on the banks of the Hun river in modern Liaodong Province. An alliance was being sealed over the blood of a sacrificed white horse and a black ox, as Ooba Khung Taiji swore allegiance in front of God to Nurhaci, the Jurchen ruler. Ooba Khung Taiji took that step so as to gain Nurhaci's support and protection in disputes with other tribal groups of Mongolian origin.
But, I need to step back for a moment (yes, I know its complex, but that's the way it was). In the last five hundred years BCE, the central states of China slowly coalesced into the Qin Empire (the first Empire) as essentially an agricultural society that could grow enough surplus food to support a centralised bureacracy and military. Much the same as happened in the Persian (Iranian) Empire and the Roman Empire.
The Qin were opposed and spent much of their military effort in defending against the Steppe people who lived across the wild steppes of southern Siberia, from the East to the west. We find these steppe people impinging on the bureaucratic states right across the Eurasian land mass, but let's keep the eastern side in minds for now. *The Steppe people were loose collections of tribal groups. The large successful Chinese Empires were often able to keep them under control, but whenever these powerful states weakened the steppe people would attack. ( and on the west side, they eventually took control of the Western Roman Empire (as the Huns).
The history of East Asian could be seen, particularly the area to the North of china (from heaven-smile) as a swirling mass of people out of which form national groups. For example, Japan and Korea from from these peoples who often took control of the local native peoples. And, in the case of China, they would, when the Central State was weak, carve off bits and form their own imitative Empire.
Sometimes a really exceptional leader would emerge, as, for example, Chiingis Khan of the first Mongol confederation. His raiders conquered China (defeating the Song Dynasty) and Tibet, and formed the Yuan Empire. After 100 years (approx.) they were expelled by Chinese armies under the Ming leadership. The Ming Empire had (at least) nominal suzerainty over Tibet. But the price of Chinese freedom (if you want to call it that) was living in a highly militarised state. Out among the Mongol Steppe people, ambition to conquer never waned. And, that's where we meet the Nurhaci referred to above. Burning ambition to conquer China drove him on, always scheming and plotting to unite the bickering Mongolian tribes. One of the groups Nurhaci sought to incorporate in his alliance were the Tibetans, who had also earlier become allies of the Mongols. It is claimed that it was in that earlier alliance that a Tibetan nobleman had been given permission to call himself 'Dalai Llama,' a claim that seems to be challenged by the current Dalai Llama. Whatever the truth of tht particular issue, there seems no doubt that a close relationship existed between the Qing Empire and the Tibetan nobility. The palace in Chengde can be seen as evidence of that closeness.
* I think the list on About.com is useful: ancienthistory.about.com/od/europe/tp/040609SteppeTribes.htm