CN101436851A - Compensating circuit and method, filter applying the compensating circuit - Google Patents
Compensating circuit and method, filter applying the compensating circuit Download PDFInfo
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Abstract
The invention provides a compensating circuit and a method and a filter adopting the compensating circuit. The compensating circuit comprises a current generating unit, a voltage comparison unit and a control unit, wherein the current generating unit comprises an adjusting capacitance, and the current generating unit can generate the reference current directly proportional to the adjusting capacitance; the voltage comparison unit is connected with the current generating unit, and can generate the reference voltage directly proportional to the product of the reference resistance and the reference current, and the reference voltage is compared with the standard voltage; and the control unit is connected with the voltage comparison unit, when the reference voltage is higher than the standard voltage, the control unit outputs capacitance selection signal of reducing the adjusting capacitance; and when the reference voltage is lower than the standard voltage, the control unit outputs capacitance selection signal of increasing the adjusting capacitance. The capacitance selection signal generated by the compensating circuit can be used to compensate bandwidth offset of the filter due to the offset of a CMOS process corner.
Description
Technical field
The present invention relates to filter, particularly relate to a kind of compensating circuit and method, use the filter of this compensating circuit.
Background technology
At wireless communication field, adopt low pass filter to carry out channel usually and select, wherein, active low-pass filter is applied in the wireless receiver because of it has high linearity.The primary element of active filter comprises operational amplifier (Operation Amplifier), resistance (Resistor) and electric capacity (Capacitor).
A kind of RC active filter is as described in 02134022.6 the Chinese invention patent application as application number, please refer to Fig. 1, resistance R p1 is connected between the positive input terminal of input signal VinP1 and differential operational amplifier opAMP1, and capacitor C p1 is connected between the positive input terminal and negative output terminal VoutN1 of differential operational amplifier opAMP1; Resistance R n1 is connected between the negative input end of input signal VinN1 and differential operational amplifier opAMP1, and capacitor C n1 is connected between the negative input end and positive output end VoutP1 of differential operational amplifier opAMP1.
Yet, realize in the integrated circuit of active filter in existing complementary metal oxide semiconductors (CMOS) (CMOS) technology of utilizing, because CMOS process corner (process corner, promptly embody the model environment of CMOS technique change, as TT, FF, SS, SF, FS) change, can make the resistance value of resistance and the capacitance generation deviation of electric capacity, and then cause the bandwidth generation deviation of filter.For instance, the CMOS integrated circuit can be introduced random error because of technique change in manufacture process, it is the deviation that the actual parameter of each device and the standard value of designing requirement (typical value) have a little, usually the deviation of the resistance value of resistance may standard value ± 15% scope in, the deviation of the capacitance of electric capacity also may standard value ± 15% scope in, like this bandwidth of practical filter can be near the standard value of designing requirement random offset, its deviation range is about-27.75% to+32.25% of standard value.
Summary of the invention
The problem that the present invention solves is, a kind of compensating circuit and compensation method is provided, uses the filter of this compensating circuit, and with the deviation of compensating resistance and electric capacity, and then the skew of compensating filter bandwidth.
For addressing the above problem, the invention provides a kind of compensating circuit, comprising:
Current generating unit comprises tunable capacitor, and described current generating unit produces and the directly proportional reference current of described tunable capacitor;
Voltage comparison unit is connected to described current generating unit, and the directly proportional reference voltage of the product of generation and reference resistance and described reference current compares described reference voltage and normal voltage;
Control unit, be connected to described voltage comparison unit, output reduces the capacitance selection signal of the tunable capacitor of described current generating unit when described reference voltage is higher than normal voltage, and output increases the capacitance selection signal of the tunable capacitor of described current generating unit when described reference voltage is lower than normal voltage.
Optionally, described current generating unit also comprise with described tunable capacitor form switched-capacitor circuit switch element, be connected the amplifier and the transistor that is connected described amplifier of described switched-capacitor circuit, described switched-capacitor circuit input offset voltage, described switch element is controlled by clock signal, described transistor output reference current, described reference current value is the product of the capacitance of frequency, bias voltage value and the tunable capacitor of the clock signal of the described switch element of control.
Optionally, the bias voltage of described current generating unit is provided by described voltage comparison unit.Described bias voltage is obtained by electric resistance partial pressure.
Optionally, described normal voltage comprises first normal voltage and is lower than second normal voltage of described first normal voltage that described voltage comparison unit compares reference voltage respectively with first normal voltage, second normal voltage; Described control unit is exported the tunable capacitor that reduces described current generating unit when described reference voltage is higher than normal voltage capacitance selection signal is meant the capacitance selection signal of exporting the tunable capacitor that reduces described current generating unit when described reference voltage is higher than first normal voltage, and the capacitance selection signal of the tunable capacitor of the described current generating unit of output increase is meant the capacitance selection signal of the tunable capacitor of the described current generating unit of output increase when described reference voltage is lower than second normal voltage when described reference voltage is lower than normal voltage.
Optionally, described tunable capacitor comprises the power condenser network, and the number of the electric capacity of described power condenser network is determined by the figure place of described capacitance selection signal.
Optionally, the magnitude of voltage of described first normal voltage, second normal voltage is that the standard value of the reference voltage that obtains during for standard value according to tunable capacitor, reference resistance and the figure place of capacitance selection signal are set, wherein, the standard value of reference voltage is between first normal voltage, second normal voltage, and the voltage difference between first normal voltage, second normal voltage is determined by the figure place of capacitance selection signal.
Optionally, described first normal voltage, second normal voltage are obtained by electric resistance partial pressure.
Optionally, the state value of the capacitance selection signal of described control unit output increases when described reference voltage is higher than first normal voltage, reduces when described reference voltage is lower than second normal voltage.
Optionally, the initial condition value of the highest order of described capacitance selection signal is 1, and the initial condition value of all the other is 0.The state value of high one state value prior to low one of the capacitance selection signal of described control unit output changes.
Optionally, described compensating circuit also comprises the voltage source that is connected on described voltage comparison unit and the switch element between the resistance, control described current generating unit of opening and closing and voltage comparison unit.
For addressing the above problem, the present invention also provides a kind of filter of using above-mentioned compensating circuit, comprises filter circuit and compensating circuit.Described compensating circuit comprises tunable capacitor and reference resistance, described compensating circuit produces and the directly proportional reference current of described tunable capacitor, form the directly proportional reference voltage of product with described reference resistance and reference current, output reduces the capacitance selection signal of described tunable capacitor when described reference voltage is higher than normal voltage, output increases the capacitance selection signal of described tunable capacitor when described reference voltage is lower than normal voltage, and described capacitance selection signal is used to regulate the electric capacity of described filter circuit.
For addressing the above problem, the present invention also provides a kind of compensation method, comprises the steps:
Produce and the directly proportional reference current of tunable capacitor;
The directly proportional reference voltage of the product of generation and reference resistance and described reference current;
When described reference voltage was higher than normal voltage, output reduced the capacitance selection signal of tunable capacitor;
When described reference voltage was lower than normal voltage, output increased the capacitance selection signal of tunable capacitor.
Optionally, described normal voltage comprises first reference voltage and is lower than second reference voltage of first reference voltage, when described reference voltage is higher than normal voltage, the capacitance selection signal that output reduces tunable capacitor is meant that when described reference voltage is higher than first normal voltage output reduces the capacitance selection signal of tunable capacitor; When described reference voltage was lower than normal voltage, the capacitance selection signal that output increases tunable capacitor was meant that when described reference voltage is lower than second normal voltage output increases the capacitance selection signal of tunable capacitor.
Optionally, the described output capacitance selection signal that reduces tunable capacitor is meant state value and the output that reduces capacitance selection signal.The capacitance selection signal that described output increases tunable capacitor is meant state value and the output that increases capacitance selection signal.
Optionally, described compensation method also comprises the electric capacity of regulating filter with the capacitance selection signal of output.
Compared with prior art, technique scheme is by changing the skew that electric capacity comes the compensating filter bandwidth, promptly at voltage because of resistance, when capacitance variations is offset, by changing the capacitance that capacitance selection signal changes electric capacity, skew with this bucking voltage, because the skew of the voltage that capacitance selection signal is can compensation relevant with resistance, electric capacity, the bandwidth of filter is equally also relevant with resistance, electric capacity, therefore, described capacitance selection signal is removed the electric capacity of control break filter, skew that equally also can the compensating filter bandwidth.
Description of drawings
Fig. 1 is the circuit diagram of a kind of active filter in the prior art;
Fig. 2 is the structural representation of the compensating circuit of the embodiment of the invention;
Fig. 3 is the circuit diagram of current generating unit shown in Figure 2;
Fig. 4 is the circuit diagram of tunable capacitor shown in Figure 3;
Fig. 5 is the timing diagram of calibrating signal, clock signal and the comparison signal of control unit shown in Figure 2;
Fig. 6 is the state diagram of the capacitance selection signal of control unit shown in Figure 2;
Fig. 7 is the Filter Structures schematic diagram of the application of embodiment of the invention compensating circuit shown in Figure 2;
Fig. 8 is the circuit diagram of filter circuit shown in Figure 7;
Fig. 9 is the flow chart of the compensation method of the embodiment of the invention.
Embodiment
The bandwidth of filter mainly is to be determined by the capacitance (C) of resistance value of resistance (R) and electric capacity, for example, the cut-off frequency of active low-pass filter (cut-off frequency) can be expressed as the proportional function of product (R*C) with the capacitance of the resistance value of resistance and electric capacity.
The embodiment of the invention is because of resistance, when capacitance variations is offset, by changing the capacitance that capacitance selection signal changes electric capacity, with the skew of this bucking voltage at voltage.Because the skew of the voltage that capacitance selection signal is can compensation relevant with resistance, electric capacity, therefore, the skew of the bandwidth that described capacitance selection signal is also can compensation relevant with resistance, electric capacity, the i.e. skew of compensating filter bandwidth.
Promptly in conjunction with the accompanying drawings and embodiments the specific embodiment of the present invention is described in detail below.
Please refer to Fig. 2, it shows the basic structure of the compensating circuit 1 of the embodiment of the invention, and described compensating circuit 1 comprises current generating unit 10, voltage comparison unit 11 and control unit 12.
Tunable capacitor Cv and switch element S1, S2, S3, S4 are connected to form switched-capacitor circuit, and the end of switch element S1 is connected with tunable capacitor Cv, and the other end is connected with bias voltage Vbias; The end of switch element S2 is connected with tunable capacitor Cv, and the other end is connected with the negative terminal input of operational amplifier A MP; The end of switch element S3 is connected with tunable capacitor Cv, other end ground connection; The end of switch element S4 is connected with tunable capacitor Cv, and the other end is connected with bias voltage Vbias.Switch element S1, S2 are by clock signal clk 1 control, and clock signal clk 1 is 1 o'clock, switch element S1, S2 closure; Clock signal clk 1 is 0 o'clock, and switch element S1, S2 open.Switch element S3, S4 that is to say that by the inversion signal CLKb1 control of clock signal clk 1 clock signal clk 1 is at 1 o'clock, and switch element S3, S4 open; Clock signal clk 1 is 0 o'clock, switch element S3, S4 closure.The frequency f CLK1 of clock signal clk 1 can be tens MHz to tens MHz.
Tunable capacitor Cv is by capacitance selection signal Capsel[4:0] regulate capacitance selection signal Capsel[4:0] state value be binary numeral.The circuit of tunable capacitor Cv as shown in Figure 4, tunable capacitor Cv is composed in parallel by capacitor C 0, Cv0, Cv1, Cv2, Cv3, Cv4, capacitor C v0, Cv1, Cv2, Cv3, Cv4 connect with switch element SW0, SW1, SW2, SW3, SW4 respectively accordingly, and switch element SW0, SW1, SW2, SW3, SW4 are respectively accordingly by capacitance selection signal Capsel0, Capsel1, Capsel2, Capsel3, Capsel4 control.Change capacitance selection signal Capsel[4:0] state value can change the capacitance of tunable capacitor Cv, capacitance selection signal Capsel[4:0] state value big more, the capacitance of tunable capacitor Cv is big more.In the present embodiment, the circuit that the capacitor C v0 of tunable capacitor Cv, Cv1, Cv2, Cv3, Cv4 form is the power condenser network, be capacitor C v3, Cv2, Cv1, the capacitance of Cv0 be respectively Cv4 capacitance 1/2,1/4,1/8,1/16, and the capacitance of Cv4 is by the size decision of the resistance and the capacitance deviation of process corner generation.
The anode input of operational amplifier A MP is connected with bias voltage Vbias, and capacitor C 1 is connected between the negative terminal input and output of operational amplifier A MP.The grid of transistor MN1 is connected with the output of operational amplifier A MP, source ground, and drain electrode is connected with drain electrode with the source electrode of transistor MN2, the grid of transistor MN3.The grid of transistor MN2 is connected with the grid of transistor MN4.The source ground of transistor MN3, drain electrode is connected with the source electrode of transistor MN4.The drain electrode of transistor MN4 is connected with the grid of transistor MN5, the source electrode of transistor MN6.The source ground of transistor MN5, drain electrode is connected with the source electrode of transistor MN7.The grid of transistor MN6 is connected with the grid of transistor MN7, MN8, and drain electrode is connected with the grid of transistor MN9.The drain electrode of transistor MN7 is connected with the negative terminal input of operational amplifier A MP.The source electrode of transistor MN8 is connected with the drain electrode of transistor MN9.The source ground of transistor MN9.
The drain current of transistor MN8 is the reference current Iref that current generating unit 10 produces.The reference current Iref that is produced by above-mentioned current generating unit 10 can be by following formulate:
Iref＝fCLK1*Vbias*Cv
Under the situation of the frequency f CLK1 of clock signal clk 1, the bias voltage Vbias value of being maintained fixed, reference current Iref is only relevant with tunable capacitor Cv, promptly is directly proportional with tunable capacitor Cv.
Please refer to Fig. 2, the reference current Iref that current generating unit 10 produces flows through reference resistance Rref, the end ground connection of reference resistance Rref, and the voltage of the other end is reference voltage Vref, and therefore, reference voltage Vref can be by following formulate:
Vref＝Iref*Rref＝fCLK1*Vbias*Cv*Rref
Under the situation of the frequency f CLK1 of clock signal clk 1, the bias voltage Vbias value of being maintained fixed, reference voltage Vref is only relevant with tunable capacitor Cv, reference resistance Rref, promptly be directly proportional with the product of reference resistance Rref with tunable capacitor Cv, when tunable capacitor Cv, reference resistance Rref because of process corner changes skew took place, reference voltage Vref also can be offset thereupon.
Reference voltage Vref connects the anode input of comparator C OMP1, and the first normal voltage Vhth connects the negative terminal input of comparator C OMP1, and comparator C OMP1 is output as comparative result HO.If reference voltage Vref is higher than the first normal voltage Vhth, then export comparative result HO=1, if reference voltage Vref is less than or equal to the first normal voltage Vhth, then export comparative result HO=0.
The second normal voltage Vlth connects the anode input of comparator C OMP2, and reference voltage Vref connects the negative terminal input of comparator C OMP2, and comparator C OMP2 is output as comparative result LO.If reference voltage Vref is lower than the second normal voltage Vlth, then export comparative result LO=1, if reference voltage Vref is greater than or equal to the second normal voltage Vlth, then export comparative result LO=0.
The first normal voltage Vhth, the second normal voltage Vlth are obtained through dividing potential drop by resistance R 1, R2, R3, R4.Divider resistance R1, R2, R3, R4 are connected between stable the voltage source V DD and ground, and the first normal voltage Vhth is the voltage between divider resistance R1, the R2, and the second normal voltage Vlth is the voltage between divider resistance R2, the R3.
The magnitude of voltage of the first normal voltage Vhth, the second normal voltage Vlth is that the figure place of the capacitance selection signal of the standard value of the reference voltage Vref that obtains when being standard value (not being offset) according to tunable capacitor Cv, reference resistance Rref and tunable capacitor Cv is set.Specifically, at tunable capacitor Cv, when reference resistance Rref is not offset, reference voltage Vref should be between the first normal voltage Vhth, the second normal voltage Vlth, if increase capacitance selection signal and tunable capacitor Cv is increased this moment, reference voltage Vref can be higher than the first normal voltage Vhth, tunable capacitor Cv is reduced, reference signal Vref can be lower than the second normal voltage Vlth, can determine voltage difference between the first normal voltage Vhth, the second normal voltage Vlth by the figure place of capacitance selection signal.Give one example, if at tunable capacitor Cv, when reference resistance Rref is not offset, the standard value of reference voltage Vref is 1V, in the present embodiment, and capacitance selection signal Capsel[4:0] be 5, promptly can represent 32 state values (2
5), adjacent state value can represent to be offset 1/32, be about 3%, promptly the voltage difference between the first normal voltage Vhth, the second normal voltage Vlth be about reference voltage Vref standard value 3%, therefore can set the first normal voltage Vhth is 1.015V, and the second normal voltage Vlth is 0.985V.After having set the first normal voltage Vhth, the second normal voltage Vlth, the resistance value of divider resistance R1, R2, R3, R4 just can have been determined, determine the technology that the resistance value of divider resistance is well known to those skilled in the art according to voltage, promptly no longer launch explanation at this.
Fig. 5 is the timing diagram of calibrating signal Calibration, clock signal clk 2 and the comparison signal Compare of control unit 12.As shown in Figure 5, when compensating circuit 1 is started working (for example, phase-locked loop circuit pins back output signal PLL lock detect in phase place), calibrating signal Calibration becomes 1 by 0, stand-by period Tw through 2 clock signal clks 2, comparison signal Compare becomes 1 by 0, start-up control unit 12, the frequency of clock signal clk 2 (tens KHz) wants slow than the frequency of clock signal clk 1, therefore when control unit 12 started, voltage comparison unit 11 can obtain stable reference voltage Vref.
Please in conjunction with reference to figure 5 and Fig. 6, Fig. 6 is the capacitance selection signal Capsel[4:0 of control unit 12] state diagram that changes with the value of comparative result HO, the LO of voltage comparison unit 11 outputs.As shown in the figure, capacitance selection signal Capsel[4:0] the initial condition value of highest order Capsel4 be 1, the initial condition value of all the other is 0, promptly the initial condition value of capacitance selection signal is made as 1/2 of its state value quantity that can represent; And capacitance selection signal Capsel[4:0] state value when changing, the state value of the state value of Gao Yiwei prior to low one changes, for example, become 1 at comparison signal Compare by 0, during the 1st clock signal clk 2, capacitance selection signal Capsel[4:0] can represent 32 state values, its initial condition value is made as 16, be 10000 with the binary number value representation, if comparative result HO, LO is 00 (being that reference voltage Vref is between the first normal voltage Vhth and the second normal voltage Vlth), capacitance selection signal Capsel[4:0] state value remain unchanged; If comparative result HO, LO be 10 (being that reference voltage Vref is higher than the first normal voltage Vhth), capacitance selection signal Capsel[4:0] state value reduce, become 01000; If comparative result HO, LO be 01 (being that reference voltage Vref is lower than the second normal voltage Vlth), capacitance selection signal Capsel[4:0] state value increase, become 11000.Capacitance selection signal Capsel[4:0] state value change, the tunable capacitor Cv of current generating unit 10 is changed, the reference voltage Vref of voltage comparison unit 11 also changes thereupon, when following 1 clock signal clk 2, control unit 12 can be according to the reference voltage Vref after changing and comparative result HO, LO and the capacitance selection signal Capsel[4:0 of the first normal voltage Vhth, the second normal voltage Vlth] current state value, redefine capacitance selection signal Capsel[4:0] state value.
Can see by Fig. 6, in the present embodiment, capacitance selection signal Capsel[4:0] the initial condition value be set at 10000.Therefore, maximum times through 5 clock signal clks 2 just can obtain finally can compensating the capacitance selection signal Capsel[4:0 of tunable capacitor Cv and reference resistance Rref skew].Certainly, capacitance selection signal Capsel[4:0] the initial condition value also can be set at other value, and be to reduce capacitance selection signal Capsel[4:0 at 10 o'clock] at comparative result HO, LO, at comparative result HO, LO is to increase capacitance selection signal Capsel[4:0 at 01 o'clock] state value, but the time that all can need to surpass 5 clock signal clks 2 just obtain compensating the capacitance selection signal Capsel[4:0 of tunable capacitor Cv and reference resistance Rref skew].That is to say, with capacitance selection signal Capsel[4:0] the initial condition value to be set at 10000 be for convenience can find dbjective state quickly at first in calibration, promptly can in the shortest time, obtain finally can compensating the capacitance selection signal Capsel[4:0 of tunable capacitor Cv and reference resistance Rref skew].
Behind 5 clock signal clks 2, calibrating signal Calibration, comparison signal Compare become 0 by 1, closing control unit 12 and pin capacitance selection signal Capsel[4:0] state value.
Need to prove, in the present embodiment, two normal voltages have been set, i.e. first normal voltage, second normal voltage, and determine capacitance selection signal Capsel[4:0 with the result that first normal voltage, second normal voltage compare respectively according to reference voltage Vref] state value, with this reference voltage Vref is adjusted in the scope of first normal voltage and second normal voltage.In fact, also can only set a normal voltage (being the standard value of the reference voltage Vref that tunable capacitor Cv, reference resistance Rref obtain when skew does not take place), and relatively determine capacitance selection signal Capsel[4:0 according to reference voltage Vref and normal voltage] state value, with this reference voltage Vref is adjusted to and approaches or equal normal voltage.Therefore, need to adopt a comparator 11 of voltage comparison units, comparator output 1 when reference voltage Vref is higher than normal voltage is lower than comparator output 0 when equaling normal voltage in reference voltage Vref; Control unit 12 is exported the capacitance selection signal Capsel[4:0 that reduces tunable capacitor Cv when reference voltage Vref is higher than normal voltage], be lower than the capacitance selection signal Capsel[4:0 that equal normal voltage time output increases tunable capacitor Cv in reference voltage Vref].
In addition, after calibrating signal Calibration becomes 0 by 1, can close compensating circuit 1, to reach purpose of power saving.For example, the switch element of can between voltage source V DD and divider resistance R1, connecting, by calibrating signal Calibration control, when calibrating signal Calibration is 1, the switch element closure, compensating circuit 1 enters operating state; When calibrating signal Calibration is 0, switch element is opened, path between voltage source V DD and divider resistance is cut off, so promptly do not have electric current and flow through divider resistance R1, R2, R3, R4, and bias voltage Vbias is 0, therefore, the comparator of current generating unit, voltage comparison unit can be closed.
Please continue with reference to figure 7, it shows the basic structure of a kind of filter of using compensating circuit shown in Figure 2.Described filter is active low pass RC filter, comprises compensating circuit 1 and filter circuit 2.
Compensating circuit 1, produce and the directly proportional reference current of described tunable capacitor, the directly proportional reference voltage of the product of formation and reference resistance and described reference current, output reduces the capacitance selection signal Capsel[4:0 of described tunable capacitor when described reference voltage is higher than first normal voltage], output strengthens the capacitance selection signal Capsel[4:0 of described tunable capacitor when described reference voltage is lower than second normal voltage].Capacitance selection signal Capsel[4:0] be used to regulate the electric capacity of filter circuit 2.Wherein, compensating circuit 1 and has been done detailed explanation in the above as described in Figure 2.
Compensating circuit 1 and filter circuit 2 are integrated on the same chip, that is to say, tunable capacitor Cpv2, the Cnv2 of the tunable capacitor Cv of compensating circuit 1, reference resistance Rref, filter circuit 2, resistance R p2, Rn2 can change the identical skew of generation with process corner.Because capacitance selection signal Capsel[4:0] can the skew of reference voltage Vref relevant with reference resistance Rref with tunable capacitor Cv in the compensating circuit 1 be compensated, therefore, capacitance selection signal Capsel[4:0] also can the skew of cut-off frequency relevant with resistance R p2, Rn2 with tunable capacitor Cpv2, Cnv2 in the filter circuit 2 be compensated.
The structure of filter circuit is not to exceed with the circuit shown in scheming, so long as the directly proportional circuit of the product of bandwidth and resistance value and capacitance (R*C) can be used the skew that compensating circuit 1 comes compensating resistance, electric capacity.For example filter circuit also can be a circuit structure shown in Figure 1, resistance R p1 shown in Figure 1, Rn1 and the reference resistance Rref of compensating circuit 1 have identical process corner to be changed, and will capacitor C p1 shown in Figure 1, Rn1 replaces with the tunable capacitor that tunable capacitor Cv with compensating circuit has variation of same process angle and circuit structure and get final product.
Corresponding to above-mentioned compensating circuit, use the filter of this compensating circuit, the present invention also provides a kind of compensation method, comprises the steps:
Produce and the directly proportional reference current of tunable capacitor;
The directly proportional reference voltage of the product of generation and reference resistance and described reference current;
When described reference voltage was higher than normal voltage, output reduced the capacitance selection signal of tunable capacitor;
When described reference voltage was lower than normal voltage, output strengthened the capacitance selection signal of tunable capacitor.
Please continue with reference to figure 9, Fig. 9 is the particular flow sheet corresponding to the compensation method of compensating circuit shown in Figure 2.
Step S11 produces and the directly proportional reference current of tunable capacitor.Wherein, described tunable capacitor is regulated by capacitance selection signal.
Step S12, the directly proportional reference voltage of the product of generation and reference resistance and reference current.
Step S13 compares described reference voltage and first normal voltage, second normal voltage, judges whether reference voltage is higher than first normal voltage, if then carry out step S14, then carries out step S15 if not.
Step S14, described reference voltage is higher than first normal voltage, and output reduces the capacitance selection signal of tunable capacitor, and regulates tunable capacitor, returns step S11.Wherein, when described reference voltage is higher than first normal voltage, reduce the state value and the output of capacitance selection signal.
Step S15, described reference voltage is less than or equal to first normal voltage, judges whether reference voltage is lower than second normal voltage, if then carry out step S16, then carries out step S17 if not.
Step S16, described reference voltage is lower than second normal voltage, and output strengthens the capacitance selection signal of tunable capacitor, and regulates tunable capacitor, returns step S11.Wherein, when described reference voltage is lower than second normal voltage, increase the state value and the output of capacitance selection signal.
Step S17, described reference voltage are greater than or equal to second normal voltage and are less than or equal to first normal voltage (reference voltage is between first normal voltage and second normal voltage), keep and output capacitance selection signal.
The capacitance selection signal of output can be used to regulate the electric capacity of filter, the skew that produces because of resistance, capacitance variations with the bandwidth of compensating filter.
In sum, the voltage that technique scheme generation and resistance, electric capacity are relevant is also judged its whether scope of offset criteria, at voltage because of resistance, when capacitance variations is offset, by changing the capacitance that capacitance selection signal changes electric capacity, with the skew of this bucking voltage.Because the skew of the voltage that capacitance selection signal is can compensation relevant with resistance, electric capacity, the bandwidth of filter is equally also relevant with resistance, electric capacity, therefore, described capacitance selection signal is removed the electric capacity of control break filter, skew that promptly can the compensating filter bandwidth.
In control unit, with the initial condition value of the highest order of capacitance selection signal is 1, the initial condition value of all the other is 0, and the state value of capacitance selection signal is when changing, the state value of the state value of Gao Yiwei prior to low one changes, and can obtain finally the capacitance selection signal that can compensating frequency be offset like this in the shortest time.Therefore, the compensating circuit of technique scheme also has short advantage of make-up time.
Compensating circuit also includes the switch element that is connected between voltage source and the resistance, output finally can compensating frequency the capacitance selection signal of skew, close the current generating unit and the voltage comparison unit of compensating circuit, therefore, technique scheme also has advantage of low power consumption.
Though the present invention with preferred embodiment openly as above; but it is not to be used for limiting the present invention; any those skilled in the art without departing from the spirit and scope of the present invention; can make possible change and modification, so protection scope of the present invention should be as the criterion with the scope that claim of the present invention was defined.
Claims (30)
1. a compensating circuit is characterized in that, comprising:
Current generating unit comprises tunable capacitor, and described current generating unit produces and the directly proportional reference current of described tunable capacitor;
Voltage comparison unit is connected to described current generating unit, and the directly proportional reference voltage of the product of generation and reference resistance and described reference current compares described reference voltage and normal voltage;
Control unit, be connected to described voltage comparison unit, output reduces the capacitance selection signal of the tunable capacitor of described current generating unit when described reference voltage is higher than normal voltage, and output increases the capacitance selection signal of the tunable capacitor of described current generating unit when described reference voltage is lower than normal voltage.
2. compensating circuit according to claim 1, it is characterized in that, described current generating unit also comprise with described tunable capacitor form switched-capacitor circuit switch element, be connected the amplifier and the transistor that is connected described amplifier of described switched-capacitor circuit, described switched-capacitor circuit input offset voltage, described switch element is controlled by clock signal, described transistor output reference current, described reference current value is the product of the capacitance of frequency, bias voltage value and the tunable capacitor of the clock signal of the described switch element of control.
3. compensating circuit according to claim 2 is characterized in that the bias voltage of described current generating unit is provided by described voltage comparison unit.
4. compensating circuit according to claim 3 is characterized in that described bias voltage is obtained by electric resistance partial pressure.
5. compensating circuit according to claim 1 is characterized in that, described normal voltage comprises first normal voltage and second normal voltage that is lower than described first normal voltage,
Described voltage comparison unit compares reference voltage respectively with first normal voltage, second normal voltage;
Described control unit is exported the tunable capacitor that reduces described current generating unit when described reference voltage is higher than normal voltage capacitance selection signal is meant the capacitance selection signal of exporting the tunable capacitor that reduces described current generating unit when described reference voltage is higher than first normal voltage, and the capacitance selection signal of the tunable capacitor of the described current generating unit of output increase is meant the capacitance selection signal of the tunable capacitor of the described current generating unit of output increase when described reference voltage is lower than second normal voltage when described reference voltage is lower than normal voltage.
6. compensating circuit according to claim 5 is characterized in that described tunable capacitor comprises the power condenser network, and the number of the electric capacity of described power condenser network is determined by the figure place of described capacitance selection signal.
7. compensating circuit according to claim 6, it is characterized in that, the magnitude of voltage of described first normal voltage, second normal voltage is that the standard value of the reference voltage that obtains during for standard value according to tunable capacitor, reference resistance and the figure place of capacitance selection signal are set, wherein, the standard value of reference voltage is between first normal voltage, second normal voltage, and the voltage difference between first normal voltage, second normal voltage is determined by the figure place of capacitance selection signal.
8. compensating circuit according to claim 7 is characterized in that, described first normal voltage, second normal voltage are obtained by electric resistance partial pressure.
9. compensating circuit according to claim 5 is characterized in that, the state value of the capacitance selection signal of described control unit output increases when described reference voltage is higher than first normal voltage, reduces when described reference voltage is lower than second normal voltage.
10. compensating circuit according to claim 1 is characterized in that, the initial condition value of the highest order of described capacitance selection signal is 1, and the initial condition value of all the other is 0.
11. compensating circuit according to claim 10 is characterized in that, the state value of high one state value prior to low one of the capacitance selection signal of described control unit output changes.
12. compensating circuit according to claim 1 is characterized in that, also comprises the voltage source that is connected on described voltage comparison unit and the switch element between the resistance, control described current generating unit of opening and closing and voltage comparison unit.
13. filter, comprise filter circuit, it is characterized in that, described filter also comprises compensating circuit, comprise tunable capacitor and reference resistance, described compensating circuit produces and the directly proportional reference current of described tunable capacitor, form the directly proportional reference voltage of product with described reference resistance and reference current, output reduces the capacitance selection signal of described tunable capacitor when described reference voltage is higher than normal voltage, output increases the capacitance selection signal of described tunable capacitor when described reference voltage is lower than normal voltage, and described capacitance selection signal is used to regulate the electric capacity of described filter circuit.
14. filter according to claim 13 is characterized in that, described compensating circuit comprises:
Current generating unit comprises tunable capacitor, and described current generating unit produces and the directly proportional reference current of described tunable capacitor;
Voltage comparison unit is connected to described current generating unit, and the directly proportional reference voltage of the product of generation and reference resistance and described reference current compares described reference voltage and normal voltage;
Control unit, be connected to described voltage comparison unit, output reduces the capacitance selection signal of the tunable capacitor of described current generating unit when described reference voltage is higher than normal voltage, and output increases the capacitance selection signal of the tunable capacitor of described current generating unit when described reference voltage is lower than normal voltage.
15. filter according to claim 14, it is characterized in that, described current generating unit also comprise with described tunable capacitor form switched-capacitor circuit switch element, be connected the amplifier and the transistor that is connected described amplifier of described switched-capacitor circuit, described switched-capacitor circuit input offset voltage, described switch element is controlled by clock signal, described transistor output reference current, described reference current value is the product of the capacitance of frequency, bias voltage value and the tunable capacitor of the clock signal of the described switch element of control.
16. filter according to claim 15 is characterized in that, the bias voltage of described current generating unit is provided by described voltage comparison unit.
17. filter according to claim 16 is characterized in that, described bias voltage is obtained by electric resistance partial pressure.
18. filter according to claim 14 is characterized in that, described normal voltage comprises first normal voltage and second normal voltage that is lower than described first normal voltage,
Described voltage comparison unit compares reference voltage respectively with first normal voltage, second normal voltage;
Described control unit is exported the tunable capacitor that reduces described current generating unit when described reference voltage is higher than normal voltage capacitance selection signal is meant the capacitance selection signal of exporting the tunable capacitor that reduces described current generating unit when described reference voltage is higher than first normal voltage, and the capacitance selection signal of the tunable capacitor of the described current generating unit of output increase is meant the capacitance selection signal of the tunable capacitor of the described current generating unit of output increase when described reference voltage is lower than second normal voltage when described reference voltage is lower than normal voltage.
19. filter according to claim 18 is characterized in that, described tunable capacitor comprises the power condenser network, and the number of the electric capacity of described power condenser network is determined by the figure place of described capacitance selection signal.
20. filter according to claim 19, it is characterized in that, the magnitude of voltage of described first normal voltage, second normal voltage is that the standard value of the reference voltage that obtains during for standard value according to tunable capacitor, reference resistance and the figure place of capacitance selection signal are set, wherein, the standard value of reference voltage is between first normal voltage, second normal voltage, and the voltage difference between first normal voltage, second normal voltage is determined by the figure place of capacitance selection signal.
21. filter according to claim 20 is characterized in that, described first normal voltage, second normal voltage are obtained by electric resistance partial pressure.
22. filter according to claim 18 is characterized in that, the state value of the capacitance selection signal of described control unit output increases when described reference voltage is higher than first normal voltage, reduces when described reference voltage is lower than second normal voltage.
23. filter according to claim 14 is characterized in that, the initial condition value of the highest order of described capacitance selection signal is 1, and the initial condition value of all the other is 0.
24. filter according to claim 23 is characterized in that, the state value of high one state value prior to low one of the capacitance selection signal of described control unit output changes.
25. filter according to claim 14 is characterized in that, described compensating circuit also comprises the voltage source that is connected on described voltage comparison unit and the switch element between the resistance, control described current generating unit of opening and closing and voltage comparison unit.
26. a compensation method is characterized in that, comprises the steps:
Produce and the directly proportional reference current of tunable capacitor;
The directly proportional reference voltage of the product of generation and reference resistance and described reference current;
When described reference voltage was higher than normal voltage, output reduced the capacitance selection signal of tunable capacitor;
When described reference voltage was lower than normal voltage, output increased the capacitance selection signal of tunable capacitor.
27. compensation method according to claim 26 is characterized in that, described normal voltage comprises first reference voltage and second reference voltage that is lower than first reference voltage,
When described reference voltage was higher than normal voltage, the capacitance selection signal that output reduces tunable capacitor was meant that when described reference voltage is higher than first normal voltage output reduces the capacitance selection signal of tunable capacitor;
When described reference voltage was lower than normal voltage, the capacitance selection signal that output increases tunable capacitor was meant that when described reference voltage is lower than second normal voltage output increases the capacitance selection signal of tunable capacitor.
28. compensation method according to claim 26 is characterized in that, the capacitance selection signal that described output reduces tunable capacitor is meant state value and the output that reduces capacitance selection signal.
29. compensation method according to claim 26 is characterized in that, the capacitance selection signal that described output increases tunable capacitor is meant state value and the output that increases capacitance selection signal.
30. compensation method according to claim 26 is characterized in that, also comprises the electric capacity of regulating filter with the capacitance selection signal of output.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CNA2007101705226A CN101436851A (en) | 2007-11-16 | 2007-11-16 | Compensating circuit and method, filter applying the compensating circuit |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNA2007101705226A CN101436851A (en) | 2007-11-16 | 2007-11-16 | Compensating circuit and method, filter applying the compensating circuit |
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| CN101436851A true CN101436851A (en) | 2009-05-20 |
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| CNA2007101705226A Pending CN101436851A (en) | 2007-11-16 | 2007-11-16 | Compensating circuit and method, filter applying the compensating circuit |
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| CN105322914A (en) * | 2014-07-29 | 2016-02-10 | 英飞凌科技奥地利有限公司 | Circuit with an RC filter |
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| WO2018090650A1 (en) * | 2016-11-18 | 2018-05-24 | 珠海格力电器股份有限公司 | Clock compensation circuit, clock circuit, and microcontroller |
| CN109213262A (en) * | 2018-07-25 | 2019-01-15 | 上海兆芯集成电路有限公司 | Offset compensation circuit |
| WO2019020056A1 (en) * | 2017-07-25 | 2019-01-31 | 深圳市中兴微电子技术有限公司 | Method and apparatus for correcting bandwidth of filter |
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| CN105322914A (en) * | 2014-07-29 | 2016-02-10 | 英飞凌科技奥地利有限公司 | Circuit with an RC filter |
| CN105322914B (en) * | 2014-07-29 | 2018-05-08 | 英飞凌科技奥地利有限公司 | Circuit with RC wave filters |
| US10644684B2 (en) | 2016-11-18 | 2020-05-05 | Gree Electric Appliances, Inc. Of Zhuhai | Clock compensation circuit, clock circuit, and microcontroller |
| WO2018090650A1 (en) * | 2016-11-18 | 2018-05-24 | 珠海格力电器股份有限公司 | Clock compensation circuit, clock circuit, and microcontroller |
| CN109302164A (en) * | 2017-07-25 | 2019-02-01 | 深圳市中兴微电子技术有限公司 | A kind of filter bandwidht calibration method and device |
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| CN109302164B (en) * | 2017-07-25 | 2022-03-01 | 深圳市中兴微电子技术有限公司 | Filter bandwidth calibration method and device |
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| CN109213262A (en) * | 2018-07-25 | 2019-01-15 | 上海兆芯集成电路有限公司 | Offset compensation circuit |
| CN109945899A (en) * | 2019-03-22 | 2019-06-28 | 重庆邮电大学 | A kind of detection coding circuit applied to output buffer technique angle compensation |
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| CN112350690A (en) * | 2020-12-01 | 2021-02-09 | 上海交通大学 | High-order N-path band-pass filter based on switched capacitor and active capacitance-resistance up-conversion |
| CN114944830A (en) * | 2022-07-22 | 2022-08-26 | 三微电子科技(苏州)有限公司 | Filter circuit |
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