CN102033562B - Linear compensated RC charging structure - Google Patents

Abstract

The invention discloses a linear compensated resistance-capacitance (RC) charging structure. The structure comprises a basic RC charging structure formed by connecting a voltage source, a resistor and a capacitor in series, a capacitor voltage detection circuit which detects voltage on the capacitor in real time, and a voltage-current conversion circuit, wherein the capacitor voltage detection circuit and the voltage-current conversion circuit are connected with the common terminals of the capacitor and the resistor. The charging current on the capacitor can be maintained to be constant by detecting the voltage on the capacitor in the basic RC charging circuit in real time and superposing current which is converted from the voltage onto the capacitor, namely the voltage on the capacitor linearly rises. In the RC structure, a certain compensation network is added on the basis of the traditional RC charging structure, so the non-linear RC charging circuit can be linearized. The circuit is easy to realize, has higher reliability and practicality, and can be widely applied to various products requiring ramp voltage signals or constant current source charging.

Description

A kind of RC charging structure of linear compensation

Technical field

The present invention relates to electronic system design, SIC (semiconductor integrated circuit), the product that is specifically related to various slope compensations, the generation of voltage ramp signal and large power, electrically source controller is used.

Background technology

In traditional design, the voltage signal on the capacitor C that the RC series connection is realized is the signal of slope variation, for the linear ramp voltage signal that rises of needs, generally need use constant current source, has improved circuit complexity, has increased cost.And ramp voltage signal is relevant with voltage on the resistance R if desired, and then the current source complexity of this moment can improve again.Such as, in the DC-DC of self-adaptation ON time controller, need to produce a current signal that is directly proportional with supply voltage, confirm the power tube ON time under the different input voltages.If adopt constant current source mode to realize that then this current source is not only constant, and need be consistent, cause this current source need carry out accurate design with supply voltage.The present invention uses the RC charging that proposes common to this type just and compensates the realization constant current source charging.The DC-DC controller of self-adaptation ON time is one of them simple application, and this paper proposed invention not merely is applicable to this field, and other occasion that need use ramp voltage signal or constant current source charging all can adopt this scheme.

Summary of the invention

To of the specific (special) requirements of current various electronic systems, the present invention proposes a kind of RC charging structure of linear compensation to ramp voltage signal or constant current source charging.

For reaching above purpose, the present invention takes following technical scheme to be achieved:

Shown in accompanying drawing 1, a kind of RC charging structure of linear compensation, an end 70 of resistance R connects supply voltage or reference voltage signal, an end ground connection of capacitor C, an other end of resistance R and capacitor C is connected together as common port.After adding constant voltage signal on resistance R of connecting and the capacitor C, the voltage on the capacitor C begins to rise, and the electric current that initial time is charged to capacitor C is the ratio of voltage signal and resistance R.Along with the voltage on the capacitor C begins to rise, the electric current that is charged on the capacitor C begins to descend, and causes the voltage rate of rise on the capacitor C to diminish.Through analyzing; Can find that the electric current that reduces than initial time on the capacitor C here is relevant with the voltage signal that capacitor C rises just; So can the voltage detecting that capacitor C rises be come out, convert electric current then to and be added on the capacitor C, make the charging current on the capacitor C remain unanimity; Then the voltage rate of rise on the capacitor C also remains unchanged, and realizes linear the rising.Through this technology, when simplifying circuit design and improving integrated level, more effectively Linear Control the RC charging structure, can be widely used in the various products that need linear ramp.

In the such scheme, the effect of said capacitance voltage testing circuit mainly is that the voltage that is used for detecting on the capacitor C rises.Initial time, when promptly the voltage at capacitor C two ends was zero, the current value that is about to charging was the ratio of voltage signal and resistance R.It mainly is because when the voltage on the capacitor C begins to rise that charging current on the said capacitor C begins to descend; The voltage at resistance R two ends begins to diminish; Make the electric current that flows through resistance begin to reduce thereupon; The electric current that promptly is charged on the capacitor C begins to reduce, and the value that the reduces voltage on the capacitor C and the ratio of resistance R just, and the voltage detecting circuit here also is used for detecting the voltage on the capacitor C just.

Said current/charge-voltage convertor is that the current compensation that reduces on the capacitor C is returned, because along with the voltage on the capacitor C rises, the electric current that is charged on the capacitor C is also reducing.After detecting the voltage on the capacitor C through above-mentioned voltage detecting circuit, be electric current with this voltage transitions more here, be added on the capacitor C, make its electric current that reduces compensate again, realized Linear Control.

The present invention is through detecting in real time the last up voltage on the capacitor C, is converted into current signal then and is added on the electric capacity, makes the electric current that reduces on the capacitor C accurately compensate again; Realized the linear-charging structure of resistance capacitance; And circuit is realized simple, and degree of accuracy guarantees that easily reliability is higher.

Description of drawings

Fig. 1 is the RC charging structure of the linear compensation of this paper invention.

Fig. 2 is a kind of concrete realization instance of this paper invention.

Fig. 3 changes synoptic diagram in time for the voltage on the electric capacity.

Fig. 4 changes synoptic diagram in time for the electric current on the electric capacity.

Embodiment

Below in conjunction with accompanying drawing and specific embodiment the present invention is done further detailed description.

Fig. 1 is the RC charging structure of linear compensation of the present invention, and Fig. 2 is a kind of concrete realization instance.

As shown in Figure 2, resistance 10 is connected with electric capacity 20 and is formed RC charge circuit, a termination input voltage signal VIN of resistance, an end ground connection of electric capacity.PMOS pipe 30 and 40 and NMOS pipe 60 and 70 formation voltage detecting circuits; Resistance 80 is used for realizing the voltage-to-current conversion, and the value of resistance 80 equates with the value of resistance 10.

The source electrode and the grid of PMOS pipe 30 and 40 are connected together respectively, and source electrode is all received on the supply voltage the same drain electrode of receiving PMOS pipe 30 of grid.The drain electrode of PMOS pipe 30 is received in the drain electrode of NMOS pipe 70, and source electrode is received the common port 90 of resistance 10 and electric capacity 20, and grid is received with the grid of NMOS pipe 60.The drain electrode of NMOS pipe 60 and grid are with the drain electrode of receiving PMOS pipe 40, and the source electrode of NMOS pipe 60 is received an end of resistance 80.The other end of resistance 80 is received on the ground.

Micro-current source 50 is received the grid of NMOS pipe 60 and 70, is used to start the capacitance voltage testing circuit, and afterwards in order to ensure accuracy, micro-current source 50 is turned off.

As input voltage V _INAfter powering on, charge through 10 pairs of electric capacity 20 of resistance, initial time through the charging current of signal wire 100 is:

$i_{100}=\frac{V_{\mathrm{IN}}-V_{20}\left(t\right)}{R_{10}}---\left(1\right)$

R wherein ₁₀Be the resistance of resistance 10, V ₂₀(t) be the t moment voltage at electric capacity 20 two ends.Because the voltage of electric capacity 20 initial times is 0, so the charging current of initial time is voltage V _INWith resistance R ₁₀Ratio.Charge Once you begin the voltage V at electric capacity 20 two ends ₂₀(t) begin to rise, suppose does not have offset current, then passes through signal wire 100 and equates with 110 charging current; Lengthening along with the duration of charging; Voltage on the signal wire 50 constantly rises, and causes the electric current that flows through resistance 10 constantly to reduce, and promptly the charging current on the electric capacity constantly reduces.Can find out that the charging current in a certain moment is compared with the charging current of initial time on the electric capacity, its decrease is capacitance voltage and resistance R just ₁₀Ratio.So this a part of electric current that will reduce through certain compensation compensates through alternate manner again, can realize that charging current is constant, the rising voltage linear.As shown in Figure 2, PMOS pipe 30,40, NMOS pipe 60,70, resistance 80 and micro-current source 50 have been formed the voltage detecting circuit and the voltage transitions current circuit of electric capacity 20.

At first, micro-current source 50 is for the trigger voltage testing circuit, promptly is switched off the realization low-power consumption after the startup.The degeneration factor that is made up of PMOS pipe 30,40 and NMOS pipe 60,70 makes NMOS manage 60 to equate with 70 source voltage, so just the voltage sample on the electric capacity 20 is managed on 60 source electrodes to NMOS, i.e. the voltage at resistance 80 two ends.Pass through the conversion of resistance 80 then, making the electric current on the resistance 80 is the ratio of capacitance voltage and resistance 80.Last once more through the mirror image of NMOS pipe 60 and 70, the feasible electric current that flows through resistance 80 is added on the electric capacity 20 through signal wire 90 again.Because resistance 80 equates with the value of resistance 10, so the electric current that reduces on the electric capacity 20 is accurately compensated the feasible permanent voltage V of being of electric current that is charged on the electric capacity 20 again _INWith the ratio of resistance 10, realized that the linearity of the constant and voltage of electric capacity charging current rises.Be illustrated in figure 3 as the charging current contrast of compensation front and back, the charging current before dotted line is represented to compensate, along with the increase in duration of charging, charging current is more and more littler, and finally the voltage on capacitor C is charged to voltage V _INThe time, charging current is reduced to 0.And adopt the electric current after the compensation to be evident as straight line, remain constant.Shown in Figure 4 for the capacitance voltage before and after the compensation contrasts, the voltage before dotted line is represented to compensate, along with the increase in duration of charging, the slope that voltage rises is more and more littler, and slope more arbitrarily is all relevant with the capacitance voltage in the corresponding moment.Obviously can find out, after over-compensation, realize that charging current is constant, the ramp voltage linearization.

Above content is to combine concrete preferred implementation to further explain that the present invention did; Can not assert that embodiment of the present invention only limits to this; Those of ordinary skill for technical field under the present invention; Under the prerequisite that does not break away from the present invention's design, can also make some simple deduction or replace, all should be regarded as belonging to the present invention and confirm scope of patent protection by claims of being submitted to.

Claims (3)

1. the RC charging structure of a linear compensation is characterized in that, comprises resistance R, capacitor C, capacitance voltage testing circuit and current/charge-voltage convertor; Wherein, resistance R is connected with capacitor C, and the common port that resistance R is connected with capacitor C (50) links to each other with capacitance voltage testing circuit and current/charge-voltage convertor, and the capacitance voltage testing circuit is connected through signal wire (60) with current/charge-voltage convertor;

Said capacitance voltage testing circuit detects the change in voltage on the capacitor C in real time;

Said current/charge-voltage convertor is the subsequent treatment unit of capacitance voltage testing circuit, and its effect is to convert the detected voltage signal of voltage detecting circuit into electric current;

The output current of said current/charge-voltage convertor is received on the capacitor C, realizes the compensation to charging current on the capacitor C, and charging current is constant on the realization capacitor C.

2. a kind of RC charging structure of linear compensation according to claim 1 is characterized in that, said resistance R is connected with capacitor C and realized that the voltage linear on the capacitor C rises, and promptly the electric current on the capacitor C keeps constant.

3. a kind of RC charging structure of linear compensation according to claim 1; It is characterized in that; It is constant that charging current on the said capacitor C keeps, current value be the magnitude of voltage of resistance upper end signal wire (70) divided by resistance R, and the end ground connection do not connected of capacitor C with resistance R.

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