Flat panel display device and stereoscopic display device

1. A flat panel display device, wherein the flat panel display device comprises a backlight system and a display panel, wherein the backlight system comprises:

an LED (Light Emitting Diode) light source, which comprises an LED lamp and an LED substrate carrying the LED lamp;

a back frame, which is disposed below the LED substrate and comprises at least a first primary assembling piece and a second primary assembling piece, which are joined to form a main frame structure of the back frame, the first primary assembling piece having an end connectable to an end of the second primary assembling piece, the end of the first primary assembling piece forming at least two joint sections, each of the joint sections having a structure mating the end of the second primary assembling piece, the end of the second primary assembling piece being switchably jointed to and occupying a first one and a second one of the at least two joint sections of the first primary assembling piece, while the other one of the at least two joint sections being idle and free of occupation, so that the second primary assembling piece is connected to the first primary assembling piece in a position-adjustable manner to respectively define a first size and a second size of the back frame, the second size being different from the first size; and

a printed circuit board (PCB), which is disposed below the back frame and fixed to the LED substrate.

2. The flat panel display device as claimed in claim 1 , wherein:

the PCB is one of a power circuit board, a control circuit board, and an LED driving circuit board.

3. The flat panel display device as claimed in claim 1 , wherein:

the backlight system further comprises a support pillar that is located in a hollow area of the main frame structure and is arranged between the PCB and the LED substrate, the support pillar having two ends respectively and securely fixed to the PCB and the LED substrate to fix the PCB to the LED substrate.

4. The flat panel display device as claimed in claim 3 , wherein:

the two ends of the support pillar are respectively connected to the PCB and LED substrate through screwing.

5. The flat panel display device as claimed in claim 1 wherein:

the at least two joint sections are arranged to space from each other in a lengthwise direction of the first primary assembling piece.

6. The flat panel display device as claimed in claim 5 , wherein:

the joint sections comprise recesses formed in a surface of the first primary assembling piece and having a shape corresponding to the end of the second primary assembling piece for receiving the end of the second primary assembling piece.

7. The flat panel display device as claimed in claim 6 , wherein:

the joint sections comprise recesses formed in a surface of the first primary assembling piece, the second primary assembling piece having a surface forming protrusions at corresponding positions, the protrusions being receivable in the recesses to join the first primary assembling piece and the second primary assembling piece to each other, the second primary assembling piece having an end forming at least two protrusions that are arranged to space from each other in a lengthwise direction of the second primary assembling piece.

8. The flat panel display device as claimed in claim 7 , wherein:

the back frame further comprises a secondary assembling piece and a bracing piece, the secondary assembling piece being arranged in the main frame structure and joined to the main frame structure; the bracing piece being fixed to the primary assembling pieces or the secondary assembling piece, the bracing piece forming a bump.

9. A stereoscopic display device, wherein:

the stereoscopic display device comprises a liquid crystal lens grating, a backlight system, and a display panel, the liquid crystal lens grating being arranged on a light exit surface of the display panel, the backlight system comprising:

an LED (light emitting diode) light source, which comprises an LED lamp and an LED substrate carrying the LED lamp;

a back frame, which is disposed below the LED substrate and comprises at least a first primary assembling piece and a second primary assembling piece, which are joined to form a main frame structure of the back frame, the first primary assembling piece having an end connectable to an end of the second primary assembling piece, the end of the first primary assembling piece forming at least two joint sections, each of the joint sections having a structure mating the end of the second primary assembling piece, the end of the second primary assembling piece being switchably jointed to and occupying a first one and a second one of the at least two joint sections of the first primary assembling piece, while the other one of the at least two joint sections being idle and free of occupation, so that the second primary assembling piece is connected to the first primary assembling piece in a position-adjustable manner to respectively define a first size and a second size of the back frame, the second size being different from the first size; and

a printed circuit board (PCB), which is disposed below the back frame and fixed to the LED substrate.