System for displaying image

1. Field of the Invention

The invention relates to a digital data sampling circuit. In particular, the invention relates to a shift register structure of the low-power digital data sampling circuit in a display panel.

2. Description of the Related Art

FIG. 1 shows digital data DATA transmitting and sampling in a conventional liquid crystal display. Digital data DATA through interface circuit 12 and delay buffers 14 is transmitted to each sample latch circuit 16 serially. Shift register 18 provides control signals (SP 1 , SP 2 , SP 3 . . . SP(n−1), SPn) serially to trigger each sample latch circuit 16 serially. Thus each sample latch circuit 16 serially samples digital data DATA. In a conventional digital data sampling circuit, digital data DATA arrives at sample latch circuit 16 earlier than control signals (SP 1 , SP 2 , SP 3 . . . SP(n−1), SPn). Therefore, a plurality of delay buffers 14 are used to delay digital data DATA for synchronizing control signals (SP 1 , SP 2 , SP 3 . . . SP(n−1), SPn) and digital data DATA received by sample latch circuit 16 .

FIG. 2 is timing diagram illustrate digital data DATA and control signals (SP 1 , SP 2 , SP 3 . . . SP(−1), SPn) of the conventional liquid crystal displays. Because of delay buffers 14 , control signals (SP 1 , SP 2 , SP 3 . . . SP(n−1), SPn) and digital data DATA will arrive at sample latch circuit 16 in the same time. In FIG. 2 , when start pulse horizontal signal STH is at high voltage level and clock horizontal signal CKH is triggered to high voltage level, first output signal OUT 1 is triggered to high voltage level. When clock horizontal signal CKH switches to low voltage level, second output signal OUT 2 is triggered to high voltage level. In addition, first control signal SP 1 is the logical AND result of first output signal OUT 1 and second output signal OUT 2 . Thus, when first output signal OUT 1 and second output signal OUT 2 both are at high voltage level, first control signal SP 1 is at high voltage level. When start pulse horizontal signal STH is at low voltage level and clock horizontal signal CKH is also triggered to high voltage level, first output signal OUT 1 switches to low voltage level. At the same time, first control signal SP 1 also switches to low voltage level. Second control signal SP 2 immediately switches to high voltage level after first control signal SP 1 switches to low voltage level. Third control signal SP 3 is also triggered to high voltage level immediately after second control signal SP 2 switches to low voltage level. Each control signal (SP 1 , SP 2 , SP 3 . . . SP(n−1), SPn) serially transmits to each sample latch circuit 16 .

The conventional technology uses a plurality of delay buffers 14 to synchronize control signals (SP 1 , SP 2 , SP 3 . . . SP(n−1), SPn) and digital data DATA received by sample latch circuit 16 . However, delay buffers 14 would consume considerable power and increase costs or layout area. As transmission speed of digital data DATA increases, the power consumption for data transmission is also increased.

Systems for displaying images are provided. In this regard, an embodiment of such as system provides a digital data sampling circuit with N stage data inputs, comprising a first stage flip-flop outputting a first output signal, a second stage flip-flop outputting a second output signal, a first stage sample latch circuit receiving digital data according to a first control signal and a first stage logic circuit comprising a first inverter inverting the second output signal to generate a first inverse logic signal, and generating the first control signal according to the first output signal and the first inverse logic signal.

In addition, an embodiment of a system provides a digital data sampling circuit with N stage data inputs, comprising a first stage flip-flop outputting a first output signal, a second stage flip-flop outputting a second output signal, a first stage sample latch circuit receiving digital data according to a first control signal and a first stage logic circuit comprising a first inverter inverting the second output signal to generate a first inverse logic signal, and generating the first control signal according to the first output signal and the first inverse logic signal.

The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:

FIG. 1 shows digital data transmission and sampling in a conventional liquid crystal display;

FIG. 2 is timing diagram illustrating digital data DATA and control signals (SP 1 , SP 2 , SP 3 . . . SP(n−1), SPn) of the conventional liquid crystal displays;

FIG. 3 shows a digital data sampling circuit according to a first embodiment of the invention;

FIG. 4 shows D-type flip-flop schematic circuit according to an embodiment of the invention;

FIG. 5 shows synchronization of the digital data and control signal according to an embodiment of the invention;

FIG. 6 shows a digital data sampling circuit according to a second embodiment of the invention;

FIG. 7 shows a digital data sampling circuit according to a third embodiment of the invention;

FIG. 8 shows a digital data sampling circuit according to a fourth embodiment of the invention;

FIG. 9 shows three kinds of logic circuits in the first stage logic circuit; and

FIG. 10 shows three kinds of logic circuits in the Nth stage logic circuit.

FIG. 11 schematically shows another embodiment of a system for displaying images.

FIG. 3 shows a digital data sampling circuit 30 according to a first embodiment of the invention. Digital data sampling circuit 30 comprises (N−1) stages flip-flop 32 (1st˜(N−1)th), logic circuits ( 36 A, 36 B and 36 C) and sample latch circuits 34 (1st˜Nth). Each stage flip-flop 32 (1st˜(N−1)th) respectively receives start pulse horizontal signal STH and clock horizontal signal CKH, and transmits and receives output signal (OUT 1 , OUT 2 . . . OUT(N−1)). Each stage sample latch circuit 34 (1st˜Nth) serially receives digital data DATA according to each control signal (SP 1 ˜SPn).

First stage logic circuit 36 A comprises an inverter 38 A and an AND logic gate 39 A. Inverter 38 A inverts second stage output signal OUT 2 from second stage flip-flop 32 (2nd) and generates an inverting logic signal. AND logic gate 39 A is coupled between inverter 38 A and first stage sample latch circuit 34 (1st). AND gate 39 A receives the inverting logic signal from inverter 38 A and first stage output signal OUT 1 from first stage flip-flop 32 (1st) producing first control signal SP 1 .

Nth stage logic circuit 36 B comprises an inverter 38 B and an AND logic gate 39 B. Inverter 38 B inverts (N−2)th stage output signal OUT(N−2) from (N−2)th stage flip-flop 32 ((N−2)th) and generates an inverting logic signal. AND logic gate 39 B is coupled between inverter 38 B and Nth stage sample latch circuit 34 (Nth). AND gate 39 B receives the inverting logic signal from inverter 38 B and (N−1)th stage output signal OUT(N−1) from (N−1)th stage flip-flop 32 ((N−1)th) for producing Nth control signal SPn.

According to the embodiment of the invention, each stage logic circuit 36 C may be an AND logic gate. Using a second stage logic circuit as an example, the second stage AND logic gate 36 C is coupled between second stage sample latch circuit 34 (2nd) and second stage flip-flop 32 (2nd), and receives first stage output signal OUT 1 from first stage flip-flop 32 (1st) and second stage output signal OUT 2 from second stage flip-flop 32 (2nd) for producing second control signal SP 2 .

FIG. 4 shows first stage flip-flop 32 (1st) and second stage flip-flop 32 (2nd) according to the embodiment of the invention. The embodiment uses the D-type flip-flop as each stage flip-flop 32 (1st˜(N−1)th) and the circuit structure of each two stage D-type flip-flops is similar. First stage flip-flop 32 (1st) receives clock horizontal signal CKH and start pulse horizontal signal STH respectively and transmits first stage output signal OUT 1 . First stage flip-flop 32 (1st) comprises inverters 43 ˜ 45 . The output of inverter 44 is coupled to the input of inverter 45 . The output of inverter 45 is coupled to the input of inverter 44 . Inverter 43 receives and inverts start pulse horizontal signal STH and outputs to the input of inverter 44 .

Second stage flip-flop 32 (2nd) receives clock horizontal signal CKH and first stage output signal OUT 1 respectively and transmits second stage output signal OUT 2 . Second stage flip-flop 32 (2nd) comprises inverters 46 ˜ 48 . The output of inverter 47 is coupled to the input of inverter 48 . Inverter 46 receives and inverts first stage output signal OUT 1 and output to the input of inverter 47 .

When clock horizontal signal CKH is at high voltage level, first stage D-type flip-flop 32 (1st) transfers the voltage level of start pulse horizontal signal STH to first stage output signal OUT 1 . When clock horizontal signal CKH is at low voltage level, second stage D-type flip-flop 32 (2nd) transfers the voltage level of first stage output signal OUT 1 to second stage output signal OUT 2 . The other stage flip-flop is similar to the above D-type flip-flop.

FIG. 5 shows that digital data DATA and control signals (SP 1 , SP 2 , SP 3 . . . SP(n−1), SPn) are synchronous according to the embodiment of the invention. Using the digital data sampling circuit of the first embodiment of the invention illustrates the relationship of each signal in time domain. When one of control signals (SP 1 , SP 2 , SP 3 . . . SP(n−1), SPn) is triggered to high voltage level, the corresponding sample latch circuit 34 (1st˜Nth) receives digital data DATA. Therefore, if it can trigger each control signal (SP 1 , SP 2 , SP 3 . . . SP(n−1), SPn) in serial, it can serially transmit digital data DATA to an LCD display.

In the first embodiment of the invention, clock horizontal signal CKH transmits to each stage flip-flop 32 (1st˜(N−1)th) and triggers each stage flip-flop to receive output signal (OUT 1 , OUT 2 . . . OUT(N−1)) from each prior stage flip-flop. For example, when clock horizontal signal CKH is at high voltage level, first stage flip-flop 32 (1st) receives start pulse horizontal signal STH and transmits first stage output signal OUT 1 to second stage flip-flop 32 (2nd). When clock horizontal signal CKH is at low voltage level, second stage flip-flop 32 (2nd) receives first stage output signal OUT 1 and transmits second stage output signal OUT 2 to third stage flip-flop 32 (3rd).

When first stage output signal OUT 1 is triggered to high voltage level and second stage output signal OUT 2 is at low voltage level, first inverter 38 A inverts second stage output signal OUT 2 to high voltage level. The inverting second stage output signal OUT 2 (high voltage level) and the first stage output signal OUT 1 (high voltage level) both input to AND logic gate 39 A. Thus, first stage control signal SP 1 is also triggered to high voltage level. When second stage output signal OUT 2 is triggered to high voltage level and first stage output signal OUT 1 is at high voltage level, simultaneously second stage control signal SP 2 is triggered to high voltage level and first control signal SP 1 switches to low voltage level.

When N−2 stage output signal OUT (N−2) is at high voltage level and N−1 stage output signal OUT(N−1) is also triggered to high voltage level, N−1 stage control signal SP(n−1) is triggered to high voltage level simultaneously. When N−2 stage output signal OUT(N−2) switches to low voltage level, inverter 38 B inverts N−2 stage output signal OUT(N−2) to high voltage level. Inverting N−2 stage output signal OUT(N−2) (high voltage level) and N−1 stage output signal OUT(N−1) (high voltage level) both input to AND logic gate 39 B. Thus, N stage control signal SPn is triggered to high voltage level and N−1 stage control signal SP(n−1) switches to low voltage level. Therefore, each control signal (SP 1 , SP 2 , SP 3 . . . SP(n−1), SPn) is triggered to high voltage level serially.

FIG. 6 shows a digital data sampling circuit 60 according to a second embodiment of the invention. The difference between the first embodiment and the second embodiment is the circuit structure of the N stage logic circuit 66 .

According to the second embodiment of the invention, an N stage logic circuit 66 comprises an inverter 68 and a NOR logic gate 69 . Inverter 68 inverts N−1 stage output signal OUT(N−1) from N−1 stage flip-flop 32 ((N−1)th) and generates an inverting logic signal. NOR logic gate 69 is coupled between inverter 68 and N stage sample latch circuit 34 (Nth). NOR logic gate 69 bases on the receiving inverting signal from inverter 68 and N−2 stage output signal OUT(N−2) from N−2 stage flip-flop 32 ((N−2)th) to generate N stage control signal SPn.

FIG. 7 shows a digital data sampling circuit 70 according to a third embodiment of the invention. The difference between the second embodiment and the third embodiment is the circuit structure of the first stage logic circuit 36 A.

According to the third embodiment of the invention, a first stage logic circuit 76 comprises an inverter 78 and a NOR logic gate 79 . Inverter 78 inverts first stage output signal OUT 1 from first stage flip-flop 32 (1st) and generates an inverting logic signal. NOR logic gate 79 is coupled between inverter 78 and first stage sample latch circuit 34 (1st). NOR logic gate 79 bases on the receiving inverting signal from inverter 78 and second stage output signal OUT 2 from second stage flip-flop 32 (2nd) to generate first stage control signal SP 1 .

FIG. 8 shows a digital data sampling circuit 80 according to a fourth embodiment of the invention. The difference between the first embodiment and the fourth embodiment is the circuit structure of the first stage logic circuit 36 A.

According to the fourth embodiment of the invention, a first stage logic circuit 76 comprises an inverter 78 and an NOR logic gate 79 . Inverter 78 inverts first stage output signal OUT 1 from first stage flip-flop 32 (1st) and generates an inverting logic signal. NOR logic gate 79 is coupled between inverter 78 and first stage sample latch circuit 34 (1st). NOR logic gate 79 bases on the receiving inverting signal from inverter 78 and second stage output signal OUT 2 from the second stage flip-flop 32 (2nd) to generate first stage control signal SP 1 .

FIG. 9 shows three kinds of logic circuits. A logic circuit 91 comprises an AND logic gate 95 and an inverter 94 . A logic circuit 92 comprises an NOR logic gate 97 and an inverter 96 . A logic circuit 93 comprises two MOS (metal oxide semiconductor) transistors 99 and an inverter 98 . Because the Boolean result of three kinds of logic circuits in FIG. 9 are the same, logic circuits 91 , 92 and 93 in FIG. 9 have the same function and can substitute for logic circuit 36 A. For example, logic circuit 91 is logic circuit 36 A in FIG. 3 and logic circuit 92 is logic circuit 76 in FIG. 7 .

FIG. 10 shows three kinds of logic circuits. A logic circuit 101 comprises an AND logic gate 105 and an inverter 104 . A logic circuit 102 comprises an NOR logic gate 107 and an inverter 106 . A logic circuit 103 comprises two MOS (metal-oxide-semiconductor) transistors 109 and an inverter 108 . Because the Boolean result of three kinds of logic circuits in FIG. 10 are the same, logic circuits 101 , 102 and 103 in FIG. 10 have the same function and can substitute for logic circuit 36 B. For example, logic circuit 101 is logic circuit 36 B in FIG. 3 and logic circuit 102 is logic circuit 66 in FIG. 6 .

Therefore, the digital data sampling circuit 60 in FIG. 6 , the digital data sampling circuit 70 in FIG. 7 and the digital data sampling circuit 80 in FIG. 8 all have the same function which the digital data sampling circuit 30 in FIG. 3 has.

FIG. 11 schematically shows another embodiment of a system for displaying images which, in this case, is implemented as a display panel 400 or an electronic device 600 . As shown in FIG. 11 , the display panel 400 comprises a digital data sampling circuit 200 . The display panel 400 can form a portion of a variety of electronic devices (in this case, electronic device 600 ). Generally, the electronic device 600 can comprise the display panel 400 and a power supply 500 . Further, the power supply 500 is operatively coupled to the display panel 400 and provides power to the display panel 400 . The electronic device 600 can be a mobile phone, digital camera, PDA (personal data assistant), notebook computer, desktop computer, television, or portable DVD player, for example.

According to the embodiment of the invention, digital data sampling circuit ( 30 , 60 , 70 and 80 ) can in advance generate control signals (SP 1 , SP 2 , SP 3 . . . SP(n−1), SPn). For example, according to the embodiment of the invention, control signals (SP 1 , SP 2 , SP 3 . . . SP(n−1), SPn) of digital data sampling circuit 30 in FIG. 5 are half clock period earlier than control signals (SP 1 , SP 2 , SP 3 . . . SP(n−1), SPn) in FIG. 2 . Therefore, it can use less delay buffers to achieve the same goal that digital data DATA and control signals (SP 1 , SP 2 , SP 3 . . . SP(n−1), SPn) synchronize and consume less power, less layout area and cost less in circuit design.

While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.