CN102023669B - Efficient and controllable constant current source circuit - Google Patents

Abstract

The invention relates to an efficient and controllable constant current source circuit. The circuit comprises n triodes, n-1 resistors and n-3 paths of loads, wherein n is a natural number which is more than 3; and the two triodes are packaged in a geminate transistor and have the same working environment. Because an emitter junction of one triode provides a bias voltage for the other triode to compensate the temperature influence, a constant current source has favorable temperature stability performance; because the current of a control end of the constant current source is very low and a majority of current passes by the loads, the working efficiency of the constant current source is higher; because the triode at the control end works in the two states of the triode and the diode, the constant current source is flexibly controlled by utilizing a digital mode; and because parameters of the four triodes are not strictly required, the constant current source can be realized by utilizing a parse element.

Description

A kind of efficient controllable constant current source circuit

Technical field

The present invention relates to a kind of constant-current source circuit, particularly a kind ofly have high work efficiency, can adopt numerically controlled efficient controllable constant current source circuit.

Background technology

Constant current source is a kind of stabilized power source, and electric current and its external action of its output are irrelevant.Constant current source is widely used in various circuit, all occupies an important position in the fields such as instrument and meter, electronic equipment and high-and-new science and technology.Constant current source can adopt as shown in Figure 1 mirror current source to realize.If triode T1, the parameter of T2 is identical, then flows through two pipe collector electric current I C1, and IC2 is identical.Reference current is as shown in Figure 1

$I_{\mathrm{REF}}=I_{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="HSA00000280566600021.png"\; state="\{\{state\}\}">C</figure-callout>}1}+2I_B=I_{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="HSA00000280566600021.png"\; state="\{\{state\}\}">C</figure-callout>}1}+2\frac{{\mathrm{<figure-callout\; id="1"\; label="I\; C"\; filenames="HSA00000280566600021.png"\; state="\{\{state\}\}">I</figure-callout>}}_C}{\mathrm{\&beta;}}$

So

$I_{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="HSA00000280566600021.png"\; state="\{\{state\}\}">C</figure-callout>}1}=I_{C2}=\frac{I_{\mathrm{<figure-callout\; id="1"\; label="REF"\; filenames="HSA00000280566600021.png"\; state="\{\{state\}\}">REF</figure-callout>}}}{1+\frac{2}{\mathrm{\&beta;}}}$

When β＞＞2, two pipe collector electric currents are approximately equal to reference current.Namely

$I_{C2}\&ap;I_{\mathrm{REF}}=\frac{V1-V_{\mathrm{BE}}}{R}\&ap;\frac{V1}{R}$

Because the T1 pipe has temperature compensation function to the T2 pipe, I _C2Temperature stability also better.But this mirror current source has following deficiency: one, and the working current of two triodes of composition mirror current source is equal, but only has a triode doing effective work, so that the efficient of mirror current source is not high, and descends along with the increase of drive current; Two, the open and close of mirror current source are determined by reference voltage V 1, so control is inconvenient, can't adopt digital form control; Three, when adopting the apportion element to realize, because the parameter differences of two triodes is so that the constant current effect is undesirable.

Summary of the invention

The object of the invention is to the defective for the prior art existence, provide a kind of efficient controlled constant-current source circuit, this circuit temperature good stability; High efficiency, and work efficiency can not descend along with the increase of drive current; Can adopt digital form to control flexibly; Can adopt the apportion element to realize.

In order to achieve the above object, design of the present invention is: the present invention proposes a kind of efficient, controllable constant current source circuit, and this circuit is comprised of n triode, a n-1 resistance and the load of n-3 road, and n is the natural number greater than 3, and four triodes are encapsulated in two in the pipe.Each to pipe in, a transistor base and collector short circuit are arranged, utilize emission to become another triode bias voltage be provided, with the impact of compensation temperature.Two namely the emitter of a triode connects the base stage of another one triode to two other triode composition Darlington transistor in the pipe, and current collection is control end very.The transmitter of another one triode connects constant current resistance, and collector connects load.The electric current of constant current source is determined by the dividing potential drop of two resistance and the ratio of another one constant current resistance.Because the enlargement factor of Darlington transistor is very high, its base current is very little, and its access can exert an influence to the voltage of divider resistance hardly.The enlargement factor of selected triode makes the electric current of control end much smaller than load end greater than 150.In this circuit, to the right parameter of the triode that uses fully and do not require identical.So the constant current source of design has temperature stability good, efficient is high, can be digital control, and the characteristics that the apportion element of can sampling is realized.

The basic circuit structure of the realization such scheme that the present invention proposes as shown in Figure 2, R2, the emitter junction of T1 and T2 provide bias voltage for the T3 base stage jointly.T1 and T3, T2 and T4 are encapsulated in respectively two in the pipe, and the T1 pipe is managed T3, and the T2 pipe has been managed temperature compensation function to T4, make the temperature stability of constant current source relatively good.The base stage that the emitter of T3 is connected to T4 forms Darlington transistor.The collector of T4 connects load, and emitter meets constant current resistance R3.The electric current of constant current source is determined by the dividing potential drop of two resistance R 1 and R2 and the ratio of constant current resistance R3.Because the enlargement factor of Darlington transistor is very high, its base current is very little, and its access can exert an influence to the voltage of divider resistance hardly.The enlargement factor of selected triode makes the electric current of control end much smaller than load end greater than 150.The electric current overwhelming majority of constant current source all flows through from load, so the efficient of constant current source is very high.When load did not have electric current to flow through, the power consumption of constant current source was very low.T3 works in triode and diode two states, and its current collection is control end very, when it is high level, and T3 emitter junction forward bias, the collector junction reverse bias, T3 works in magnifying state, for T4 provides base current; When it is low level, the collector junction forward bias, at this moment, the collector junction of T3 is equivalent to a diode, and the base voltage of T3 is moved to about 0.7V, and T4 is turn-offed.Like this, make constant current source have at an easy rate numerically controlled feature.In circuit, parameter to four triodes does not have specific (special) requirements, can find out from top analysis, larger enlargement factor is helpful to the work efficiency that improves constant current source, in application, select the higher triode of enlargement factor as far as possible, but and do not require that four transistor parameters are identical, so this circuit can adopt the apportion element to realize at an easy rate.

According to the foregoing invention design, the present invention adopts following technical proposals:

A kind of efficient controllable constant current source circuit comprises n triode T1, T2, and T3, T4 ..., Tn, a n-1 resistance R 1, R2, R3 ..., Rn-1 and n-3 road load R _L1, R _L2, R _L3..., R _Ln-3, n is the natural number greater than 3, it is characterized in that T1 and T3, T2 and T4 are encapsulated in respectively two in the pipe, and the base stage of T1 and T2 and collector short circuit, the emitter of T1 connects the collector of T2, the grounded emitter of T2; Connect reference voltage V 2 behind the collector series connection R2 of T1 and the R1, R2, the emitter junction of T1 and T2 provide bias voltage for the T3 base stage jointly; The collector of T3 meets control signal S, and the base stage that emitter meets T4 forms Darlington transistor; Meet load R between the collector of T4 and the power supply V1 _L1, ground connection behind the emitter series connection constant current resistance R3; T5, T6 ..., the base stage of Tn connects the emitter of T3, meets respectively each load R between each collector and the power supply V1 _L2, R _L3..., R _Ln-3, each emitter each constant current resistance R3 that connects, R4 ..., ground connection behind the Rn-1; The current collection of described T3 is control end very, when it is high level, and T3 emitter junction forward bias, the collector junction reverse bias, T3 works in magnifying state as triode, for T4 provides base current; When it is low level, the collector junction forward bias, at this moment, the collector of T3 is equivalent to a diode, and the base voltage of T3 is moved to about 0.7V, and T4 is turn-offed; Like this, it is digital control constant current source have been realized.

The present invention compared with prior art has following apparent substantive distinguishing features and remarkable advantage:

1, uses having managed temperature compensation function, make the temperature stability of constant current source relatively good.

2, the control end electric current of constant current source is very little, and most electric currents make the efficient of constant current source very high from the load flow mistake.

3, the control end triode works in triode and diode two states, makes constant current source can adopt digital form to control flexibly;

4, four transistor parameters are not strict with, make constant current source can adopt at an easy rate the apportion element to realize.

Below in conjunction with drawings and Examples, be described in detail of the present invention.

Description of drawings

Fig. 1 is the mirror current source schematic diagram;

Fig. 2 is efficient controlled constant current source schematic diagram;

Fig. 3 is that efficient controlled constant current source is applied in the LED driving;

Fig. 4 is efficient controlled constant current source multichannel Extended Principle Diagram;

Specific implementation method

Embodiment one:

Details are as follows by reference to the accompanying drawings for the preferred embodiments of the present invention: referring to Fig. 2, this efficient controllable constant current source circuit comprises four triode T1, T2, T3, T4, three resistance R 1, R2, R3 and one tunnel load R _LT1 and T3, T2 and T4 are encapsulated in respectively two in the pipe, and the T1 pipe is managed T3, and the T2 pipe has been managed temperature compensation function to T4.C1, C2 and C3 mainly are in order to prevent overshoot, and it is worth about 1nF, according to the frequency adjustment of control signal S.Can find out that from the circuit of the efficient controlled constant current source of Fig. 2 the base voltage of triode T3 is:

$V_{\mathrm{<figure-callout\; id="3"\; label="b"\; filenames="HSA00000280566600021.png"\; state="\{\{state\}\}">b</figure-callout>}3}=V_{\mathrm{<figure-callout\; id="1"\; label="be"\; filenames="HSA00000280566600021.png"\; state="\{\{state\}\}">be</figure-callout>}1}+V_{\mathrm{be}2}+\frac{V+\mathrm{\&Delta;V}}{R_1+R_2}{R}_2$

In the formula, V _Be1, V _Be2Be respectively triode T1, the emitter voltage drop of T2, V is that reference power supply V2 deducts V _Be1, V _Be2Value, Δ V is the error of V.So flow through the electric current of each LED passage be:

$I=\frac{V_{R3}}{R_3}=\frac{V_{b3}-V_{\mathrm{be}3}-V_{\mathrm{be}4}}{R_3}=\frac{V_{\mathrm{be}1}+V_{\mathrm{be}2}-V_{\mathrm{be}3}-V_{\mathrm{be}4}}{R_3}+\frac{V+\mathrm{\&Delta;V}}{(R_1+R_2)R_3}{R}_2$

Equally, V _Be3, V _Be4Be respectively T3, the emitter voltage drop of T4.In with pair of pipes, V _Be1And V _Be3, V _Be2Very little with difference, can be similar to and think equal.So following formula becomes:

$I=\frac{V+\mathrm{\&Delta;V}}{(R_1+R_2)R_3}{R}_2=\frac{{\mathrm{VR}}_2}{(R_1+R_2){\mathrm{<figure-callout\; id="3"\; label="R"\; filenames="HSA00000280566600021.png"\; state="\{\{state\}\}">R</figure-callout>}}_3}+\frac{\mathrm{\&Delta;V}{R}_2}{({\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="HSA00000280566600021.png"\; state="\{\{state\}\}">R</figure-callout>}}_1+R_2){\mathrm{<figure-callout\; id="3"\; label="R"\; filenames="HSA00000280566600021.png"\; state="\{\{state\}\}">R</figure-callout>}}_3}$

As can be seen from the above equation, the electric current of constant current source is comprised of reference current and error two parts, and wherein, reference current is determined by the dividing potential drop of two resistance R 1 and R2 and the ratio of constant current resistance R3.The error of constant current source is determined by the error of reference voltage, and multiply by a scale factor in the error of reference voltage.In actual applications, this scale factor is about about 0.1.So the efficient controlled constant current source of the present invention's design also has preferably jamproof ability.

Embodiment two:

In LED-backlit and illumination were used, LED must adopt constant current source to drive the about 20mA of its electric current.Adopt the efficient controlled constant current source of present embodiment two to drive as shown in Figure 3, if reference voltage V 2 is 12V, R1 is 18.2K ohm, and R2 is 3K ohm, and R3 is 75 ohm.So the constant current source electric current is that the LED drive current is

$I=20.000\mathrm{mA}+\frac{{\mathrm{\&Delta;VR}}_2}{(R_1+R_2){\mathrm{<figure-callout\; id="3"\; label="R"\; filenames="HSA00000280566600021.png"\; state="\{\{state\}\}">R</figure-callout>}}_3}$

$=20.000\mathrm{mA}+1.89\mathrm{\&Delta;VmA}$

If the error of reference voltage is less than 0.2V, then the error of constant current source is less than 2%.V1 adjusts according to the LED quantity of series connection.The reference voltage terminal electric current is 0.5mA, because the enlargement factor of T4 surpasses 150, the electric current of control end is less than 0.13mA, and the electric current overwhelming majority of constant current source flows through from load LED, and the electric current that other parts flow through is very little.By accessing the square wave control signal at control end S, LED can obtain the burst mode light dimming feature.Can find out that from this example constant current source has efficient controlled feature.

Embodiment three:

If need the controlled constant current source of Multi-channel high-efficient in using, and the electric current of each branch road is identical, present embodiment three method expansion as shown in Figure 4 to save components and parts, reduces cost.T4, T5 ..., Tn adopts the triode of same model, and the power that their consume is basic identical, and the T2 pipe is to T4, T5 ..., the Tn pipe has temperature compensation function equally, and the temperature stability of constant current source is protected.So after the expansion, every advantage of efficient controlled constant current source still has.

Although the present invention is described with reference to some embodiments, those of ordinary skill in the art will be understood that and can make many distortion and change and not depart from the spirit or scope of the present invention that appended claim and equivalence thereof limit the present invention.

Claims (1)

1. an efficient controllable constant current source circuit comprises nIndividual triode T1, T2, T3, T4 ..., Tn, N-1Individual resistance R 1, R2, R3 ..., Rn-1 and N-3Road load R _L1, R _L2, R _L3..., R _Ln-3, nFor greater than 3 natural number, it is characterized in that T1 and T3, T2 and T4 are encapsulated in respectively two in the pipe, the base stage of the base stage of T1 and collector short circuit and T2 and collector short circuit, the emitter of T1 connects the collector of T2, the grounded emitter of T2; Connect reference voltage V 2 behind the collector series connection R2 of T1 and the R1, R2, the emitter junction of T1 and T2 provide bias voltage for the T3 base stage jointly; The collector of T3 meets control signal S, and the base stage that emitter meets T4 forms Darlington transistor; Meet load R between the collector of T4 and the power supply V1 _L1, ground connection behind the emitter series connection constant current resistance R3; T5, T6 ..., the base stage of Tn connects the emitter of T3, meets respectively each load R between each collector and the power supply V1 _L2, R _L3..., R _Ln-3, each emitter each constant current resistance R4 that connects, R5 ..., ground connection behind the Rn-1; The current collection of described T3 is control end very, when it is high level, and T3 emitter junction forward bias, the collector junction reverse bias, T3 works in magnifying state as triode, for T4 provides base current; When it is low level, the collector junction forward bias, at this moment, the collector of T3 is equivalent to a diode, and the base voltage of T3 is moved to about 0.7V, and T4 is turn-offed; Like this, it is digital control constant current source have been realized.

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