JPH04180454A - Signal scanning circuit for close contact image sensor - Google Patents

Abstract

PURPOSE:To improve power efficient by adopting push-pull driver configuration for a signal scanning circuit and providing a ratio type inverter interrupting the conduction at a prescribed point of time to a master section so as to reduce power loss for an inactive output period. CONSTITUTION:When a shift clock phi1 is at a level of a power supply VDD, an input DIn is sent to a gate of a TR3. When the clock phi1 reaches a level G, a signal level is latched by a master section M by a capacitor C1. Simultaneously, when a clock phi2 reaches a level of the VDD, a ratio type inverter comprising TRs 5, 6 is acted and the output level stored in the C1 is sent to a slave section S. When the transfer is finished, the clock phi2 reaches the level G, the signal level is stored in a capacitor C2 and the conduction of a TR 2 of the section M is stopped and when the clock phi1 reaches the level of the VDD, the input is started. Then TRs 7, 8 form a push-pull driver interrupting DC conduction to ground and drives and outputs a scanning pulse. Thus, the DC power consumption in a register of the section M is not caused at pulse output and the power is consumed for a limited time only in registers of other stage.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a signal scanning circuit for a contact type image sensor.
In particular, the present invention relates to a shift register scanning type signal scanning circuit in which the signal scanning circuit is formed using MO3 thin film transistors.

[Prior Art] Conventionally, the signal scanning circuit of a contact type image sensor formed using this type of MO5 thin film transistor has been constructed by connecting a ratio type EE inverter (EE) through a bidirectional transmission gate (G), as shown in Fig. 4. It consisted of an N-stage two-phase (φ1φ2) dynamic shift register in which one-stage registers were connected in cascade to form a master section (M) and a slave section (S). In addition.

In the figure, DIP is the output of the register, Qo is the output of the register, DR is the driver section connected to the slave section S, and φIG is the output scanning pulse IVDD of the driver is the power supply. Further, FIG. 5 is a diagram showing the configuration of a ratio type inverter EE.

[Problems to be Solved by the Invention] The signal scanning circuit of the contact type image sensor formed using the conventional MO5 thin film transistor described above has a master section that connects an EE type inverter (EE) through a bidirectional transmission gate (G). The structure is an N-stage 2-phase (φ1, φ2) dynamic shift register in which a single-stage register (M) and a slave section (S) are connected in cascade, so that the DC current conduction between the power supply and ground is reduced to In the shift register, not only the slave circuit at one stage outputting the scan active pulse, but also the master circuit at the stage (N-1) where the scan pulse is not actively output, There is a problem in that the power loss during the active output period is extremely large and the power efficiency is poor.

The present invention provides a signal scanning circuit for a contact type image sensor that solves the problems of the conventional circuit and has good current efficiency.

[Means for Solving the Problems] A signal scanning circuit of a contact type image sensor formed with an MO5 thin film transistor of the present invention is a signal scanning circuit of a contact type image sensor formed with an MO5 thin film transistor of the present invention. The scanning circuit includes a master section including a bidirectional transmission gate that receives a first shift pulse and a ratio dynamic inverter whose DC conduction time is 1/2 from the power supply to ground, and a bidirectional transmission gate that receives a second shift pulse. A single-stage register is connected in cascade, and includes a slave section including a transmission gate and a ratio type EE inverter, and a driver section that receives an anti-phase clock from the inverter of the slave section and has a push-pull configuration that does not cause direct current conduction. It is composed of an N-stage two-phase dynamic shift register connected to each other.

[Example] Next, one embodiment of the present invention will be explained with reference to the drawings.

FIG. 1 is a configuration diagram showing one element of a signal scanning circuit of a contact type image sensor according to an embodiment of the present invention, and FIG. 2 is an image of a contact type image sensor obtained by cascading the signal scanning circuits shown in FIG. 1. A conceptual diagram of the overall configuration of the sensor, Figure 3 is similar to Figures 1 and 2.
It is an example of the timing of the clock signal in the circuit operation in the figure.

In this example, a photoelectric conversion element (P,) (1<n<N) is transferred to 1 by a transfer gate (TG□) and a scanning pulse (φTG,).
The present invention relates to a signal scanning circuit for an image sensor of a type that reads out a photoelectric conversion signal by sequentially connecting lines L and R2 at each location.

MO8 thin film transistor (hereinafter referred to as
This is a shift register scanning type signal scanning circuit formed using MOSTFT.

Figure 1 shows the photoelectric conversion element (
P, ) and a sensor element (R6) containing M
The transfer gate (TG, ) which is OSTFT and the scan pulse (
The register element (R
), and furthermore.

The configuration of circuit elements within the register element (R6) is also shown.

The first stage register (R,) is a master section (M) whose main elements are TRI, TR2, and TR3, which are made up of MOS T F T.
and MOSTFT, TR4, TR5゜Slave section (S) whose main elements are TR6 and MOSTFT TR7
, TR8.

The register elements (R,) (1<n<N) are commonly supplied with a power supply VDD, a ground voltage (G), and two-phase shift clocks φ and φ2 from the outside.

Next, the sensor element (Ee) (1< n
Fig. 2 shows the overall configuration and scanning concept of a contact type image sensor obtained by cascading images of <N), and Fig. 1 and Fig. 2
The operation will be explained based on FIG. 3 showing the timing of the clock signal in the operation shown in the figure.

For convenience, the operation will be explained assuming that the circuit is formed of NMOS TFTs. When a circuit is formed using PMO5TPT, the potential of VDD with respect to the earth (G) is read as negative VDD.

The start pulse SP is the first scanning pulse (φTGI
) is an external clock that activates the register scan (R1) input (DI+) to level G. When the shift clock φ1 is at level V■, the bidirectional transmission gate (TRI) is in a conductive state, and the level of the input (Dl,) is transmitted to the gate of TR3. When the clock φ becomes level G after the transmission is completed, the signal level at the gate of TR3 is held at jic1 in the master section.

At the same time, clock φ2 becomes level VDD and TR2
becomes conductive, the ratio type inverter in the master section begins to function, and the master section output level is determined according to the level held in the capacitor C1, and is transmitted to the inside of the slave through the transmission gate TR4, which is in a conductive state.

The input signal at the level G of the start pulse SP is inverted in the master section of the register R1 (VDD VT
) becomes the output and is transmitted to the slave.

Here, the potential V7 is the threshold voltage of the TFT.

TR5 and TR6 are ratio type EEs that load TR5 with MO5.
It is an inverter, and furthermore, the input and output of this inverter are connected to a TR whose one terminal of the driver section (DR) is VDD.
7 and TR8, one terminal of which is grounded (G), are connected to the respective gates of TR8, and a pushinable driver configured to cut off DC conduction from the power supply to the ground is configured to drive and output scanning pulses. At the same time, the output Q of the register R, which has been inverted again in the slave part (S), is output and transmitted to the input D I of the register Rll+l in the first stage, the master part (M). After the signal transfer from the TR6 to the slave section (S) is completed, the clock φ2 becomes level G, and the signal level at the gate of TR6 is held by the capacitor C2. At the same time as holding in the slave section (S).

The conduction of TR2 of the ratio type symverter of the master section (M) is stopped. At the same time, in the master section (M), the clock φ1 becomes level VDD and a new input starts.

Based on the above operation of one element of the signal scanning circuit shown in FIG. 1, in the signal scanning circuit connected in cascade as in the embodiment shown in FIG. The scanning pulse φTGI that has received the scan activation is shifted by the shift clocks φ1 and φ2 from φTGI → φTG2 → φTG3...→φTGN every cycle of the shift clock, and the photoelectric conversion signals are sequentially read out. it is obvious.

Furthermore, the following is clear regarding power consumption from one or more operations. That is, the scanning pulse (φTG, ) (1<n
<N) in a signal scanning circuit of an image sensor that sequentially activates one location at a time and reads out a charging conversion signal.

■In the one stage register that outputs scanning active pulses, the master section outputs level (VDD Vt) and consumes no DC power, and the slave section outputs level G.
With direct current conduction for output.

■On the other hand, in the other (N-1) stage registers, although the master section outputs level G, the conduction of TR2 is limited to 1/2 the operating time due to the interruption of the level G period of clock φ2. There must be.

In the slave section, level CVoD with no DC power consumption
VT) output.

I understand that.

[Effects of the Invention] As explained above, the present invention can be formed using MO8 thin film transistors and has a V! The shift register type signal scanning circuit of the EM image sensor has a push-pull driver configuration in which DC current does not occur in the driver section, which almost always outputs the scan inactive level G, and also has a push-pull driver configuration that does not cause DC current conduction to the driver section, which outputs the scanning inactive level G at all times. By providing a ratio-type dynamic inverter that cuts off conduction at clock φ2 in the master section that holds G as an output, it is possible to improve power consumption to 1/4 of the conventional ratio.

[Brief explanation of the drawing]

FIG. 1 shows an element (1/N stage) of the signal scanning circuit in an embodiment of the signal scanning circuit of the contact type image sensor of the present invention
Effi) and the register circuit (R,), Figure 2 is a conceptual diagram of an example of the entire contact type image sensor obtained by cascading the signal scanning circuits in Figure 1, and Figure 3 is the signal scanning circuit. A diagram of an example of clock signal timing in circuit operation in a circuit, FIG. 4 is a register circuit element diagram of a signal scanning circuit in a conventional example, and FIG. 5 shows a configuration of an EE type inverter in FIG. 4. It is a diagram. Explanation of symbols: R,...Register element, E,...Sensor element 1M...Master section, S...Slave section, DR
...Driver section. 1M1 Figure En Sessa # element

Claims (2)

[Claims] (1) In a contact image sensor in which the signal scanning circuit is formed of a thin film, the signal scanning circuit formed of a MOS thin film transistor is connected to a bidirectional transmission gate that receives the first shift pulse and DC conduction from the power supply to the ground. a master section including a ratio type dynamic inverter with a 1/2 operation time, a bidirectional transmission gate receiving a second shift pulse, and a ratio type EE.
An N-stage 2-phase structure formed by cascading one stage of registers each including a slave part including an inverter and a driver part having a push-pull configuration that receives an anti-phase clock from the inverter of the slave part and has a push-pull configuration in which no direct current conduction occurs. A signal scanning circuit for a contact image sensor characterized by being configured with a dynamic shift register. (2) The signal scanning circuit for a contact image sensor according to claim (1), wherein the first and second shift clock pulses are opposite pulses.