CN103475801A

CN103475801A - Signal clamping device

Info

Publication number: CN103475801A
Application number: CN2012101847872A
Authority: CN
Inventors: 王飞; 傅璟军; 胡文阁
Original assignee: BYD Co Ltd
Current assignee: BYD Co Ltd
Priority date: 2012-06-06
Filing date: 2012-06-06
Publication date: 2013-12-25

Abstract

The invention provides a signal clamping device which comprises a coupling capacitor, a signal reset module, a comparison module and a switch module. One end of the coupling capacitor receives an input signal, and the other end of the coupling capacitor couples the input signal to a signal to be clamped. The signal reset module is connected with the other end of the coupling capacitor and is used for resetting the signal to be clamped to low level under the control of the reset signal. The comparison module is connected with the other end of the coupling capacitor and is used for comparing a voltage of the reset signal to be clamped with a voltage of a reference signal so as to generate a switch control signal. The switch module is respectively connected with the comparison module and the other end of the coupling capacitor and is used for breakover or cut-off under the control of the switch control signal so as to selectively use output voltage of the comparison module to charge the coupling capacitor. According to the invention, circuit area can be reduced, power consumption and cost are minimized, the structure is simpler, and it is more beneficial to chip integration.

Description

A kind of signal clamping apparatus

Technical field

The present invention relates to the electronic circuit technology field, a kind of signal clamping apparatus of special design.

Background technology

A lot of systems all need vision signal is processed, as TV, video monitoring, video acquisition, video amplifier etc.When transmission video signal, owing between the earth potential of distinct device, may having pressure reduction.Protected for the interface circuit to transmission equipment, generally take the mode of AC coupled to export or incoming video signal.After coupling, can cause the DC component of vision signal to lose, usually need the DC component of the vision signal after clamp circuit is inputted coupling to be recovered.

Fig. 1 is traditional clamp circuit.As shown in Figure 1, clamp circuit comprises coupling capacitance C1, two current source IDC1 and IDC2, enhancement mode NMOS pipe MN1 and comparator C OMP.Initial reset: after powering on, RST has a high level time in short-term and becomes afterwards low again.As RST while being high, the MN1 conducting, COMP output is simultaneously resetted by RST, is output as low level, and electric current I DC1 is disconnected, thus current source IDC1 is disconnected, and IDC2 and MN1 discharge, and VINC just is reset to low level.RST becomes lowly afterwards, starts the following course of work.If do not add MN1, although only also the VINC node can be drawn into low level by IDC2, because the IDC1 electric current is large, and the time disconnected is short, and the IDC2 electric current is very little, and electric capacity is very large again, can not at short notice VINC be discharged to low level.By will be coupled vision signal VINC and the reference voltage VREF of input of comparator, compare, when VINC is less than VREF, comparator is output as high level, opens current source IDC1 to capacitor C 1 charging, makes the DC level rising of VINC.When the minimum level of VINC is greater than VREF, comparator is output as low level, and turn-off current source IDC1 makes the DC level of VINC keep, thereby the minimum level of VINC is clamped to the VREF value of setting.

Traditional signal clamping circuit need to use the first extra current source IDC1 coupling capacitance C1 is charged, and the area of chip, power consumption and cost are all higher.

Summary of the invention

The present invention one of is intended to solve the problems of the technologies described above at least to a certain extent or at least provides a kind of useful business to select.For this reason, the object of the invention is to propose the fireballing signal clamping apparatus of a kind of clamp.

For achieving the above object, embodiments of the invention provide a kind of signal clamping apparatus, comprising: coupling capacitance, and a termination of described coupling capacitance is received input signal, and at the other end of described coupling capacitance, described input signal is coupled as and treats clamp signal; The signal reseting module, described signal reseting module is connected with the other end of described coupling capacitance, under the control of reset signal, by described, treating that clamp signal is reset to low level; Comparison module, described comparison module is connected with the other end of described coupling capacitance, for described after resetting treated to the voltage of clamp signal and the voltage of reference signal compare to generate switch controlling signal; Switch module, described switch module is connected with the other end of described comparison module and described coupling capacitance respectively, for conducting under the control of described switch controlling signal or cut-off, with the output voltage that optionally utilizes described comparison module, to described coupling capacitance, charge, wherein, when the described DC level until clamp signal of the other end of described coupling capacitance output is equal to or higher than the voltage of described reference signal, described switch module ends to treat that by described the DC level of clamp signal remains on the voltage of described reference signal.

According to the signal clamping apparatus of the embodiment of the present invention, under the prerequisite that does not increase circuit complexity, reach and reduce circuit area, reduce the purpose of power consumption and cost, structure is simpler, is more conducive to integrated chip.And utilize the signal reseting module to treat clamp signal and carry out initial reset, improved the speed of clamp.

Additional aspect of the present invention and advantage part in the following description provide, and part will become obviously from the following description, or recognize by practice of the present invention.

The accompanying drawing explanation

Above-mentioned and/or additional aspect of the present invention and advantage are from obviously and easily understanding becoming the description of embodiment in conjunction with following accompanying drawing, wherein:

The circuit diagram that Fig. 1 is traditional signal clamping apparatus;

Fig. 2 is the circuit diagram according to the signal clamping apparatus of the embodiment of the present invention;

Fig. 3 is the circuit diagram of signal clamping apparatus according to an embodiment of the invention;

Fig. 4 is the circuit diagram of signal clamping apparatus in accordance with another embodiment of the present invention;

The circuit diagram that Fig. 5 is the signal clamping apparatus of another embodiment according to the present invention;

The circuit diagram that Fig. 6 is the signal clamping apparatus of another embodiment according to the present invention.

Embodiment

Below describe embodiments of the invention in detail, the example of described embodiment is shown in the drawings, and wherein same or similar label means same or similar element or the element with identical or similar functions from start to finish.Be exemplary below by the embodiment be described with reference to the drawings, be intended to for explaining the present invention, and can not be interpreted as limitation of the present invention.

In the present invention, unless otherwise clearly defined and limited, broad understanding should be done in the terms such as term " installation ", " being connected ", " connection ", " fixing ", for example, can be to be fixedly connected with, and can be also to removably connect, or connect integratedly; Can be mechanical connection, can be also to be electrically connected to; Can be directly to be connected, also can indirectly be connected by intermediary, can be the connection of two element internals.For the ordinary skill in the art, can understand as the case may be above-mentioned term concrete meaning in the present invention.

In the present invention, unless otherwise clearly defined and limited, First Characteristic Second Characteristic it " on " or D score can comprise that the first and second features directly contact, also can comprise that the first and second features are not directly contacts but by the other feature contact between them.And, First Characteristic Second Characteristic " on ", " top " and " above " comprise First Characteristic directly over Second Characteristic and oblique upper, or only mean that the First Characteristic level height is higher than Second Characteristic.First Characteristic Second Characteristic " under ", " below " and " below " comprise First Characteristic directly over Second Characteristic and oblique upper, or only mean that the First Characteristic level height is less than Second Characteristic.

Below with reference to Fig. 2 to Fig. 6, the signal clamping apparatus according to the embodiment of the present invention is described.

As shown in Figure 2, the signal clamping apparatus of the embodiment of the present invention comprises: coupling capacitance 100, signal reseting module 200, comparison module 300 and switch module 400.

One termination of coupling capacitance 100 is received input signal VIN, and this input signal VIN is coupled as and treats clamp signal VINC, in the other end output of coupling capacitance 100, treats clamp signal VINC.Wherein, input signal VIN can be AC signal, for example vision signal.Be understandable that, the signal clamping apparatus that the embodiment of the present invention provides includes but not limited to vision signal is carried out to the clamp processing, can also carry out the clamp processing to the ac input signal of other types, does not repeat them here.

Signal reseting module 200 is connected with the other end (VINC output) of coupling capacitance 100, will treat that under the control of reset signal RST clamp signal VINC is reset to low level.For example, will treat that clamp signal VINC is reset to zero potential.

In one embodiment of the invention, signal reseting module 200 comprises current source and switch element.Wherein, an end of current source is connected with the other end of coupling capacitance 100, other end ground connection.Switch element is in parallel with current source, and conducting under the control of reset signal RST.Originally, RST is high level, and now switch element, in conducting state, can be discharged to the other end of coupling capacitance 100, thereby realizes treating level drop-down of clamp signal VINC.To the electric discharge gradually of another degree of coupling capacitance 100, treat that clamp signal VINC is reset to low level along with current source and switch element.When reset signal RST upset is low level, the switch element cut-off.

In example of the present invention, switch element can be enhancement mode NMOS (N-Mental-Oxide-Semiconductor, the N-type Metal-oxide-semicondutor) pipe, enhancement mode PMOS(P-Mental-Oxide-Semiconductor, P type Metal-oxide-semicondutor) pipe or transmission gate (complementary MOS pipe).Be understandable that, above-mentioned only for exemplary purposes, rather than in order to limit the present invention.Switch element also can adopt other to have the analogue device of switch control functions.

Reset signal RST can have reset signal generation device to provide.Wherein, reset signal can be for becoming low level again after a high level in short-term.That is, the original levels of reset signal RST is high level, and is low level in upset after the scheduled time.

Comparison module 300 is connected with the other end (VINC output) of coupling capacitance 100, will serve the DC level for the treatment of clamp signal VINC after reseting module 200 resets and the voltage of reference signal VREF compares to generate switch controlling signal by signal.It should be noted that, input signal VIC is AC signal, and its clamp signal VINC that treats after coupling capacitance 100 couplings is also AC signal, and the DC level of AC signal is the minimum voltage of AC signal.Therefore, the DC level clamp for the treatment of clamp signal VINC also can be understood as the clamp to the minimum voltage of AC signal, is about to treat that the minimum voltage of clamp signal VINC and the voltage of reference signal VREF compare to generate switch controlling signal.In one embodiment of the invention, comparison module 300 can be comparator.Particularly, the positive input terminal of comparator receives reference signal VREF, and negative input end is connected and treats clamp signal with reception with the other end of coupling capacitance 100, and reset terminal is connected to receive reset signal RST with reset signal generation device.Higher by the gain by comparator and speed designs, can be so that clamp be more accurate.

It should be noted that, the original levels of reset signal is high level, and comparator is resetted, and makes comparator be output as low level.In this period, the switch element of signal reseting module 200 is conducting state, thereby will treat that clamp signal VINC is reset to low level.When the reset signal upset is low level, the switch element cut-off, and comparator starts normal operation.

Switch module 400 is connected with the other end of coupling capacitance 100 with comparison module 300 respectively, conducting or cut-off under the control of the switch controlling signal of exporting at comparison module 300, thereby optionally further export the voltage of comparison module 300 outputs to coupling capacitance 100, to charge to coupling capacitance 100.Particularly, under the control of switch module 400 at switch controlling signal during conducting, by comparison module to coupling capacitance 100 output voltages to realize the charging to coupling capacitance 100.While ending under the control of switch module 400 in switching signal, stop to the charging of coupling capacitance 100.

In one embodiment of the invention, the switch controlling signal of comparison module 300 outputs can be Continuity signal or pick-off signal.Wherein, switch module 400 is under the control of Continuity signal, in conducting state; Switch module 400 is under the control of pick-off signal, in cut-off state.

In one embodiment of the invention, switch module 400 can be diode, enhancement mode NMOS pipe or enhancement mode PMOS pipe.

Particularly, comparison module 300 is resetted under the control of reset signal RST, and exports pick-off signal, i.e. low level signal when reset signal is high level.

And comparison module 300 will treat that the DC level of clamp signal VINC and the voltage of reference signal VREF compare.When VINC is less than VREF, the output of comparison module 300 is exported Continuity signal with 400 conductings of control switch module, and then coupling capacitance 100 is charged, and now the magnitude of voltage of VINC is in ascent stage.When VINC is equal to or greater than VREF, the output of comparison module 300 output pick-off signal is with 400 cut-offs of control switch module.Hence one can see that, and when the VINC DC level is equal to or greater than VREF, switch module 400 cut-off remains on the voltage of reference signal VREF with the DC level that will treat clamp signal VINC, i.e. VINC=VREF, thus realize the clamp to VINC.

In one embodiment of the invention, the current source of signal reseting module 200 is weak current sources, can the DC level of VINC signal is slowly drop-down, thereby work as the DC level of VINC higher than VREF, and, when switch module 400 ends again, realize the slow electric discharge to the other end of coupling capacitance 100, thereby the DC level of VINC signal is slowly drop-down, the minimum level of avoiding VINC is during always higher than VREF, and the DC level of VINC can't be set to VREF.It should be noted that, in charging process, when the DC level of VINC during higher than VREF, need to carry out the DC level of VINC signal drop-downly, now switch module 400 should be cut-off state, only by current source, to the DC level of VINC signal, carries out drop-down.This be drop-down action due to the DC level of 400 pairs of VINC signals of switch module for drop-down by force, can the DC level of VINC is drop-down too much, thus also can't make the DC level of VINC signal be set in the VREF value.

If start the VINC node not to be resetted, if its initial potential, far above VREF, so because coupling capacitance C1 is very large and current source IDC is very weak, needs through for a long time could be by the current potential of VINC, its DC level is pulled down to VREF.Therefore, the signal reseting module 200 of the embodiment of the present invention can improve the clamp speed to VINC.

It should be noted that, it is multiple that switch element and switch module 400 can adopt the type of device to be, and wherein, in the signal clamping apparatus provided in the embodiment of the present invention, the type of switch element and switch module 400 employing devices can combination in any.

Below with reference to Fig. 3 to Fig. 6, respectively the signal clamping apparatus of multiple combination mode is described.

(1) switch element is that enhancement mode NMOS pipe (MN1), switch module 400 are diode

As shown in Figure 3, the termination of coupling capacitance C1 enters vision signal VIN, after other end output coupling, treats clamp signal VINC.The termination of current source IDC enters to treat clamp signal VINC, other end ground connection.The grid of enhancement mode NMOS pipe MN1 meets reset signal RST, and drain electrode meets VINC, source electrode and substrate ground connection.The positive pole of diode D1 connects the output of comparator C OMP, and negative pole connects treats clamp signal VINC.The positive input termination reference signal VREF of comparator C OMP, negative input end reception clamp signal VINC, the termination that resets RST.

During beginning, initial reset signal RST is high level, and reset signal is resetted to comparator COMP, makes comparator be output as low level.Now, diode D1 is in cut-off state.Conducting when MN1 is high level in reset signal, discharged to current source IDC VINC node, thereby be zero level by the VINC node reset.Thus, the scheme that mutually right VINC is resetted, can reduce the required time of clamp to a great extent.After the RST signal resets, NMOS pipe MN1 disconnects, and comparator starts normal operation.

Comparator C OMP compares signal VINC and VREF.When the DC level of VINC is less than VREF, comparator C OMP is output as high level, makes diode D1 conducting, thereby provides electric current with to coupling capacitance C1 charging to coupling capacitance C1, makes the DC level of VINC raise.When the VINC DC level is equal to or greater than VREF, comparator is output as low level, and diode D1 cut-off, make the DC level of VINC remain on VREF, reaches the purpose of clamp.

(2) switch element is that enhancement mode PMOS pipe (MP1), switch module 400 are diode

As shown in Figure 4, when described switch element is enhancement mode PMOS pipe, switch element also comprises inverter INV. wherein, the end of inverter INV is connected to receive reset signal RST with the reset signal output device, the other end is connected with the grid of enhancement mode PMOS pipe MP1, thereby can keep enhancement mode PMOS pipe MP1 to manage the consistent of reset level with NMOS.When RST is effective (high level), RST is low level after inverter, makes the MP1 conducting, thereby the VINC node is carried out to discharge reduction.

As from the foregoing, by increasing inverter, can realize switch element no matter be PMOS pipe or NMOS pipe, when RST is high level, VINC be resetted.

The operation principle of other devices is the same, does not repeat them here.

(3) switch element is that enhancement mode NMOS pipe (MN1), switch module 400 are NMOS pipe (MN2)

As shown in Figure 5, the termination of coupling capacitance C1 enters vision signal VIN, after other end output coupling, treats clamp signal VINC.The termination of current source IDC enters to treat clamp signal VINC, other end ground connection.The grid of enhancement mode NMOS pipe MN1 meets reset signal RST, and drain electrode meets VINC, source electrode and substrate ground connection.The drain and gate of enhancement mode NMOS pipe MN2 is connected with the output of comparator C OMP, and source electrode meets VINC, substrate ground connection.The positive input termination reference signal VREF of comparator C OMP, negative input end reception clamp signal VINC, the termination that resets RST, output connects the drain and gate of NMOS pipe MN2.

During beginning, initial reset signal RST is high level, and reset signal is resetted to comparator COMP, makes comparator be output as low level.Now, MN2 is in cut-off state.Conducting when MN1 is high level in reset signal, discharged to current source IDC VINC node, thereby be zero level by the VINC node reset.Thus, with respect to the scheme VINC not resetted, can reduce to a great extent the required time of clamp.After the RST signal resets, NMOS pipe MN1 disconnects, and comparator starts normal operation.

Comparator C OMP compares signal VINC and VREF.When VINC is less than VREF, comparator C OMP is output as high level, makes the MN2 conducting, thereby provides electric current with to coupling capacitance C1 charging to coupling capacitance C1, makes the DC level of VINC raise.When the DC level of VINC is equal to or greater than VREF, comparator is output as low level, and the MN2 cut-off, make the DC level of VINC remain on VREF, reaches the purpose of clamp.

(4) switch element is that enhancement mode NMOS pipe (MN1), switch module 400 are enhancement mode PMOS pipe (MP1)

As shown in Figure 6, switch module 400 adopts enhancement mode PMOS pipe MP1, and wherein, the grid of enhancement mode PMOS pipe MP1 is connected with the other end (VINC output) of coupling capacitance with substrate, and drain electrode and source electrode connect the output of comparator.The operation principle of other devices is the same, does not repeat them here.

According to the signal clamping apparatus of the embodiment of the present invention, under the prerequisite that does not increase circuit complexity, utilize the output of comparator not only as control signal but also as current source, reduce circuit area thereby reach, reduce the purpose of power consumption and cost, structure is simpler, is more conducive to integrated chip.And the metal-oxide-semiconductor that utilizes initial condition to reset, improved the speed of clamp.

In the description of this specification, the description of reference term " embodiment ", " some embodiment ", " example ", " concrete example " or " some examples " etc. means to be contained at least one embodiment of the present invention or example in conjunction with specific features, structure, material or the characteristics of this embodiment or example description.In this manual, the schematic statement of above-mentioned term not necessarily referred to identical embodiment or example.And the specific features of description, structure, material or characteristics can be with suitable mode combinations in any one or more embodiment or example.

Although the above has illustrated and has described embodiments of the invention, be understandable that, above-described embodiment is exemplary, can not be interpreted as limitation of the present invention, those of ordinary skill in the art is not in the situation that break away from principle of the present invention and aim can be changed above-described embodiment within the scope of the invention, modification, replacement and modification.

Claims

1. a signal clamping apparatus, is characterized in that, comprising:

Coupling capacitance, a termination of described coupling capacitance is received input signal, and at the other end of described coupling capacitance, described input signal is coupled as and treats clamp signal;

The signal reseting module, described signal reseting module is connected with the other end of described coupling capacitance, under the control of reset signal, by described, treating that clamp signal is reset to low level;

Comparison module, described comparison module is connected with the other end of described coupling capacitance, for described after resetting treated to the voltage of clamp signal and the voltage of reference signal compare to generate switch controlling signal;

Switch module, described switch module is connected with the other end of described comparison module and described coupling capacitance respectively, for conducting under the control of described switch controlling signal or cut-off, with the output voltage that optionally utilizes described comparison module, to described coupling capacitance, charge, wherein, when the described DC level until clamp signal of the other end of described coupling capacitance output is equal to or higher than the voltage of described reference signal, described switch module ends to treat that by described the DC level of clamp signal remains on the voltage of described reference signal.

2. signal clamping apparatus as claimed in claim 1, is characterized in that, described signal reseting module comprises:

Current source, an end of described current source is connected with the other end of described coupling capacitance, the other end ground connection of described current source;

Switch element, described switch element is in parallel with described current source, for conducting under the control of described reset signal, the other end of described coupling capacitance is discharged to by described, treat that clamp signal is reset to low level, and described switch element ends after described reset signal level upset.

3. signal clamping apparatus as claimed in claim 1 or 2, is characterized in that, the original levels of described reset signal is high level, and be low level in upset after the scheduled time.

4. signal clamping apparatus as claimed in claim 2, is characterized in that, described switch element is enhancement mode NMOS pipe, enhancement mode PMOS pipe or transmission gate.

5. signal clamping apparatus as claimed in claim 4, it is characterized in that, when described switch element is enhancement mode PMOS pipe, described switch element also comprises inverter, wherein, one end of described inverter is connected to receive described reset signal with described reset signal output device, and the other end of described inverter is connected with the grid of described enhancement mode PMOS pipe.

6. signal clamping apparatus as claimed in claim 1, it is characterized in that, described comparison module is comparator, wherein, the positive input terminal of described comparator receives described reference signal, negative input end is connected to receive the described clamp signal for the treatment of with the other end of described coupling capacitance, and reset terminal is connected to receive described reset signal with described reset signal output device.

7. signal clamping apparatus as claimed in claim 6, is characterized in that, described switch controlling signal is Continuity signal or pick-off signal.

8. signal clamping apparatus as claimed in claim 7, is characterized in that, described comparison module is resetted under the control of described reset signal, and export pick-off signal when described reset signal is high level.

9. signal clamping apparatus as claimed in claim 7, it is characterized in that, when the described DC level until clamp signal is less than the voltage of described reference signal, the output output Continuity signal of described comparison module is to control described switch module conducting, otherwise the output of described comparison module output pick-off signal is to control described switch module cut-off.

10. signal clamping apparatus as claimed in any one of claims 1-9 wherein, is characterized in that, described switch module is diode, enhancement mode NMOS pipe or enhancement mode PMOS pipe.