CN103425167A - Constant voltage and constant current control circuit and constant voltage and constant current switching compensation method - Google Patents

Abstract

The invention discloses a constant voltage and constant current control circuit and a constant voltage and constant current switching compensation method. The method includes utilizing a constant current error amplifier (CCEA) to generate a constant current signal, utilizing a constant voltage error amplifier (CVEA) to generate a constant voltage signal, receiving the constant current signal and the constant voltage signal to control a controlled system, compensating current extracted by the CCEA from the CVEA in a period that the controlled system works in a constant voltage status and output current is approximate to a constant current value, and compensating current provided by the CVEA to the CCEA in a period that the controlled system works in a constant current status and output voltage is approximate to a constant voltage value. The constant voltage and constant current control circuit has the advantages that starting from basic reasons for interference in a switching period from the CCEA to the CVEA, output of the CCEA and the CVEA in a constant voltage and constant current switching period is compensated, so that a current range of non-constant voltage and non-constant current in the constant voltage and constant current switching period is eliminated, and the circuit can realize lossless switching between constant voltage and constant current.

Description

Constant pressure and flow control circuit and constant pressure and flow switching compensation method

Technical field

The present invention relates to a kind of constant pressure and flow circuit, relate in particular to constant pressure and flow control circuit and constant pressure and flow switching compensation method.

Background technology

In control system, it is to realize by the control to dutycycle that constant pressure and flow is controlled.Figure 1 shows that existing a kind of concrete structure, this kind of concrete mode of only take describes as example, as shown in Figure 1, the main modular of circuit comprises: constant-current amplifier 101 (constant current error amplifier, abbreviation CCEA), constant-voltage amplifier 102 (constant voltage error amplifier is called for short CVEA) and state controller 103 etc.Wherein, CVEA102 works when controlled system is operated in pressure constant state, is used for controlling the constant of output voltage, and CCEA101 works when controlled system is operated in constant current state, is used for controlling the constant of output and input current.

As shown in Figure 1, wherein, two voltage input ends of CVEA102 are respectively reference voltage input terminal Vref_CV1 and feedback voltage input end VFB1; Two input ends of CCEA101 are respectively reference voltage input terminal Vref_CC1 and feedback voltage input end VCS1.The tail current size of CVEA102 and CCEA101 is 1: 1, and size is designated as i.

In the ideal case, the mutual conductance infinity of CVEA102 and CCEA101.When controlled system is operated in pressure constant state, when output (entering) electric current is less than constant current value, the VCS voltage ratio Vref_CC1 voltage of CCEA101 is low, because the mutual conductance infinity of CCEA101, the tail current of CCEA101 all flows away by metal-oxide-semiconductor N6 and metal-oxide-semiconductor N8, metal-oxide-semiconductor N7, metal-oxide-semiconductor N9 and metal-oxide-semiconductor N10 are all in off state, and CCEA101 breaks from controlled system like this, now by CVEA102, by loop, control controlled system in pressure constant state; When controlled system is operated in constant current state, the feedback voltage input end VFB1 input terminal voltage of CVEA102 is lower than the voltage of its reference voltage input terminal Vref_CV1, because the mutual conductance infinity of CVEA102, therefore, metal-oxide-semiconductor N1, metal-oxide-semiconductor N3 and metal-oxide-semiconductor N4 are all in off state, and the tail current of CVEA102 all flows into the VC1 node from metal-oxide-semiconductor N2, serve as the current source load of CCEA101 output stage, now, CCEA101 controls controlled system by loop and is operated in constant current state.

But, under actual conditions, the mutual conductance of CVEA102 and CVEA101 is all limited.The effect curve figure that Fig. 2 is existing constant pressure and flow control circuit.

1) be operated in pressure constant state when controlled system, i.e. V _FB1=V _{Ref_CV1}, V _CS1>V _{Ref_CC1}The time:

A) when output current much smaller than constant current value, correspondence

The time (g _N6For the mutual conductance of CVEA101 input to pipe metal-oxide-semiconductor N6 and metal-oxide-semiconductor N7), i _N6=i _N8=i, i _N7=i _N9=i _N10=0, now metal-oxide-semiconductor N10 is in off state, and CVEA101 does not affect CVEA102.The interval of horizontal ordinate i from 0 to ia in this state corresponding diagram 2;

B) when output current close to constant current value, correspondence

The time, i _N10=i _N9=i _N7=g _N6(V _{Ref_CC1}-V _CS1), this electric current is provided by metal-oxide-semiconductor N2, so i _N10=i _N2-i _N1=g _N1* (V _{Ref_CC1}-V _FB1)=g _N6(V _{Ref_CC1}-V _CS1), (g wherein _N1For the mutual conductance of CVEA1 input to pipe metal-oxide-semiconductor N1 and metal-oxide-semiconductor N2),

$V_{\mathrm{ref}\_\mathrm{CC}1}-V_{\mathrm{FB}1}=\frac{g_{n6}(V_{\mathrm{ref}\_\mathrm{CC}1}-V_{\mathrm{CS}1})}{g_{n1}},$ The variable quantity of corresponding output voltage is

$K*(V_{\mathrm{ref}\_\mathrm{CC}1}-V_{\mathrm{FB}1})=K*\frac{g_{n6}(V_{\mathrm{ref}\_\mathrm{CC}1}-V_{\mathrm{CS}1})}{g_{n1}},$ Wherein K is the feedback factor of output voltage to the feedback voltage end VFB1 voltage of CVEA102.Therefore the constant voltage effect of controlled system is subject to the impact of CVEA101.In this state corresponding diagram 2, horizontal ordinate i is from ia to ilmt, the interval of ordinate V from Va to Vc.

2) be operated in (output voltage equals the constant voltage value, and output current equals constant current value) while being constant voltage and constant current state when controlled system, must corresponding V _FB1=V _{Ref_CV1}, V _CS1=V _{Ref_CC1}If: V _CS1=V _{Ref_CC1},

And the electric current of metal-oxide-semiconductor N10 is provided by metal-oxide-semiconductor N2, like this,

So V _FB1≠ V _{Ref_CC1}, it is that the situation of constant voltage and constant current state does not exist that controlled system is operated in;

3) be operated in constant current state when controlled system, i.e. V _FB1<V _{Ref_CV1}, V _CS1=V _{Ref_CC1}The time:

A) when output voltage close to constant voltage value, correspondence $\left(V_{\mathrm{ref}\_\mathrm{CV}1}\right)>V_{\mathrm{FB}1}>(V_{\mathrm{ref}\_\mathrm{CV}1}-\frac{1}{g_{n1}})$ The time,

i _N10＝i _N2-i _N4＝g _n1*(V _{ref_CV1}-V _FB1)，

$V_{\mathrm{ref}\_\mathrm{CC}1}-V_{\mathrm{CS}1}=\frac{\frac{1}{2}*i-i_{N7}}{g_{n6}}=\frac{\frac{1}{2}*i-g_{n1}*(V_{\mathrm{ref}\_\mathrm{CV}1}-V_{\mathrm{FB}1})}{g_{n6}}\&NotEqual;0,$ Therefore the constant current effect of controlled system is subject to the impact of CVEA102.In this state corresponding diagram 2, horizontal ordinate i is from ia to ilmt, the interval of ordinate V from Vc to Va;

B) when output voltage far below constant voltage value, correspondence i _N2=i _N4=i _N5=i _N11=0, metal-oxide-semiconductor N11 is in off state, and CVEA102 breaks from controlled system, so be the impact that the constant current effect of controlled system is not subject to CVEA102.In this state corresponding diagram 2, horizontal ordinate equals ilmt, the interval of ordinate V from 0 to Va.

Analysis above comprehensive obtains constant pressure and flow effect curve as shown in Figure 2, and when output (entering) electric current approaches constant current value, output voltage starts to reduce, and when output voltage approaches the constant voltage value, output (entering) electric current also starts to reduce.In constant voltage and constant current handoff procedure, it is the also non-constant current of non-constant voltage that one section interval is arranged, and is not needed constant voltage or constant current.

Summary of the invention

The object of the present invention is to provide a kind of constant pressure and flow control circuit and constant pressure and flow switching compensation method, in order to solve the constant pressure and flow control circuit of prior art, in constant voltage and constant current handoff procedure, between one section Current Zone in, the non-constant voltage of electric current is the problem of non-constant current also.

To achieve these goals, the invention provides a kind of constant pressure and flow control circuit, it comprises: the first variable module, and described the first variable module is exported the first constant signal, and described the first constant signal can increase or reduce within the first stage; The second variable module, described the second variable module is exported the second constant signal, and described the second constant signal can increase or reduce in subordinate phase; Compensating module, with described the first variable module, with described the second variable module, be connected respectively, described compensating module is within the described first stage, and described the first constant signal is increased or the value that reduces compensates, and makes described the first constant signal constant within the described first stage; Described compensating module is in described subordinate phase, and described the second constant signal is increased or the value that reduces compensates, and makes described the second constant signal constant in described subordinate phase.

The present invention also provides a kind of constant pressure and flow switching compensation method, comprises,

Utilize constant-current amplifier to produce constant current signal;

Utilize constant-voltage amplifier to produce the constant voltage signal;

Receive described constant current signal and described constant voltage signal, to control controlled system;

Be operated in pressure constant state and the output current stage close to constant current value in described controlled system, the electric current that described constant-current amplifier is extracted from described constant-voltage amplifier compensates;

Be operated in constant current state and the output voltage stage close to the constant voltage value in described controlled system, the electric current that described constant-voltage amplifier is offered to described constant-current amplifier compensates.

The constant pressure and flow control circuit, from the basic reason of constant-voltage amplifier and constant-current amplifier switch step generation interference, set about, by the CCEA to circuit and CVEA, in the output of constant pressure and flow switch step, compensate, eliminate non-constant voltage in constant voltage and constant current handoff procedure also between one section Current Zone of non-constant current, made circuit can realize harmless switching in constant voltage and constant current.

The accompanying drawing explanation

Fig. 1 is existing constant pressure and flow control circuit figure;

The effect curve figure that Fig. 2 is existing constant pressure and flow control circuit;

The module map that Fig. 3 is constant pressure and flow control circuit of the present invention;

The circuit diagram of the embodiment that Fig. 4 is constant pressure and flow control circuit of the present invention;

The effect curve figure that Fig. 5 is constant pressure and flow control circuit of the present invention.

Embodiment

The module map that Fig. 3 is constant pressure and flow control circuit of the present invention, as shown in Figure 3, to achieve these goals, the invention provides a kind of constant pressure and flow control circuit, wherein, comprises, and constant-voltage amplifier 305, constant-voltage amplifier 305 can be exported a constant voltage signal; Constant-current amplifier 306, constant-current amplifier 306 can be exported a constant current signal; Current compensation module 307, with constant-voltage amplifier 305, with constant-current amplifier 306, be connected respectively, and the controlled system of controlling at the constant pressure and flow control circuit (the following controlled system that all is called for short) is operated in the pressure constant state process, and the output current of controlled system approaches the stage of constant current value, the electric current that constant-current amplifier 306 is extracted from constant-voltage amplifier 305 compensates, in controlled system, be operated in the constant current state process, the output voltage of controlled system approaches the stage of constant voltage, and the electric current that constant-voltage amplifier 305 is offered to constant-current amplifier 306 compensates; Constant-voltage amplifier 305 and constant-current amplifier 306, the two,, by current compensation module 307, is connected to a common signal output node 308.Wherein, this constant pressure and flow control circuit can also be by state controller 309 output signal according to constant-voltage amplifier 305 and constant-current amplifier 306, control output voltage or the output current of controlled system.

The circuit diagram of the embodiment that Fig. 4 is constant pressure and flow control circuit of the present invention, as shown in Figure 4, in a wherein embodiment of constant pressure and flow control circuit of the present invention, constant-voltage amplifier 305 specifically comprises the first current source i1, and its source electrode with a PMOS pipe M1 and the 2nd PMOS pipe M2 is connected; The grid of a described PMOS pipe M1 connects the first feedback voltage V FB, and drain electrode connects grid and the drain electrode of a NMOS pipe M3; The grid of described the 2nd PMOS pipe M2 connects the first reference voltage Vref _ CV, and drain electrode connects grid and the drain electrode of the 2nd NMOS pipe M4; A described NMOS pipe M3 source electrode is connected with the source electrode of described the 2nd NMOS pipe M4, and equal ground connection.

Compensating module 307 comprises tail current source i3, and the size of current of its input is 1/2nd of the first current source i1 input current size; The 3rd NMOS pipe M5, its grid is connected with the grid of described the 2nd NMOS pipe M2, and the source electrode of the 3rd NMOS pipe M5 is connected with the source electrode of the 3rd NMOS pipe M6 simultaneously; The 4th NMOS pipe M11, its source electrode is connected with the source electrode of the 3rd NMOS pipe M5, the grid of the 4th NMOS pipe M11 connects the source electrode of the 3rd NMOS pipe M5, the drain electrode of the 4th NMOS pipe M11 connects the input node VC of tail current source i3 and state controller 309, and this input node is signal output node common in above-described embodiment 308.

Constant-current amplifier 306 specifically comprises: the second current source i2, its source electrode with the 3rd PMOS pipe M6 and the 4th PMOS pipe M7 is connected, the grid of described the 3rd PMOS pipe M6 connects the second feedback voltage V CS, the drain electrode of the 3rd PMOS pipe M6 connects grid and the drain electrode of the 5th NMOS pipe M8, the grid of described the 4th PMOS pipe M7 connects the second reference voltage Vref _ CC, the drain electrode of described the 4th PMOS pipe M7 connects grid and the drain electrode of the 6th NMOS pipe M9, the source electrode of described the 5th NMOS pipe M8 is connected with the source electrode of the 6th NMOS pipe M9, and equal ground connection, the drain electrode of described the 4th PMOS pipe M7 connects the drain electrode of the 3rd NMOS pipe M5, the 7th NMOS pipe M10, its grid connects the grid of the 6th NMOS pipe M9, the source electrode of described the 7th NMOS pipe M10 connects the source electrode of described the 5th NMOS pipe M8 and described the 6th NMOS pipe M9, and the drain electrode of described the 7th NMOS pipe M10 connects the input node VC of described state controller 309.

As shown in Figure 4, state controller 309 specifically comprises: PWM comparer 11, and one input end connects comparative voltage, and another input end connects described input node; Logic and driver module 10, its input end connects the output terminal of comparer; On-off element 12, its control end connects the output terminal of described logic and driver module 10, and described logic and driver module 10 can amplify the output signal of described PWM comparer 11, and drives the folding of described on-off element 12, in the present embodiment, on-off element 12 is chosen as MOS type on-off element; Voltage stabilizing diode 15, an end of an end of its negative electrode connecting valve element 12 and inductance 13 connects, the plus earth of voltage stabilizing diode 15; Electric capacity 14, it is connected with the other end of inductance 13 and the output terminal of state controller 309.

According to the circuit in above-mentioned specific embodiment, below be described in further detail the principle that realizes of constant pressure and flow control circuit of the present invention.

In conjunction with reference to shown in figure 1 and Fig. 4, in the present embodiment, change a NMOS pipe M3 of former control circuit and the 2nd NMOS pipe M4 into the diode connected mode by the current mirror connected mode.In Fig. 1, the grid of a NMOS pipe M3 is connected with the grid of the 2nd NMOS pipe M4, and the source electrode of a NMOS pipe M3 is connected with the source electrode of the 2nd NMOS pipe M4.In the present embodiment, increase the 3rd NMOS pipe M5 and the 4th NMOS pipe M11, the grid of the 2nd NMOS pipe M4 is connected to the grid of the 3rd NMOS pipe M5, carry out the electric current of mirror image the 2nd NMOS pipe M4 by the 4th NMOS pipe M5 and the 5th NMOS pipe M11, and the drain terminal of the 4th NMOS pipe M5 is connect to the drain terminal that the 4th PMOS manages M7, the drain terminal of the 5th NMOS pipe M11 connects the VC node.The 3rd NMOS pipe M5 is operated under pressure constant state the impact on constant-current amplifier 306 for compensating constant-voltage amplifier 305 in controlled system, and the 4th NMOS pipe M11 is operated under constant current state the impact on constant-voltage amplifier 305 for compensating constant-current amplifier 306 in controlled system; Increase a tail current i3 and be connected to the VC node, its size of current is

To realize constant-voltage amplifier 305 and constant-current amplifier 306, the compensation of the impact of the tail current when the output conversion.

The process that lower surface analysis controlled system is switched between constant voltage duty and constant current duty, the effect curve figure that Fig. 5 is constant pressure and flow control circuit of the present invention (the effect curve figure that wherein dotted line is existing constant pressure and flow control circuit), as shown in FIG. 4 and 5:

When controlled system is operated in pressure constant state, i.e. V _FB=V _{Ref_CV}, V _CS>V _{Ref_CC}The time:

When the output current of controlled system much smaller than constant current value, correspondence The time, i _M6=i _M8=i, i _M7=i _M9=i _M10=0, wherein, g _M1Be the mutual conductance of a PMOS pipe M1 and NMOS pipe pair of pipes, i _M6Be the electric current of the 3rd PMOS pipe M6, i _M8Be the electric current of the 5th NMOS pipe M8, i _M7Be the electric current of the 4th PMOS pipe M7, i _M9The electric current of the 6th NMOS pipe M9, i _M10It is the electric current of the 7th NMOS pipe M10; And now the 7th NMOS pipe M10 is in off state, and constant-current amplifier 306 does not affect constant-voltage amplifier 305, and the constant voltage effect of controlled system is unaffected.The interval of horizontal ordinate i from 0 to ia in this state corresponding diagram 5;

When the output current of controlled system close to constant current value, correspondence The time, $i_{M7}=\frac{1}{2}*(i-g_{m2}(V_{\mathrm{CS}}-V_{\mathrm{ref}\_\mathrm{CC}})).$ It is mirror that the 3rd NMOS pipe M5 manages M4 with the 2nd NMOS, according to the current mirror principle, M4 need to the electric current of M5 equivalent, Because V under the constant voltage duty _CS>V _{Ref_CC}So, The 6th NMOS pipe M9 and the 7th NMOS pipe M10 are in off state, and constant-current amplifier 306 does not affect constant-voltage amplifier 305, and the constant voltage effect of controlled system is unaffected.In this state corresponding diagram 5, horizontal ordinate i is from ia to ilmt, the solid line part in the interval of ordinate V from Va to Vc.

When controlled system is operated in (output voltage equals the constant voltage value, and output current equals constant current value) while being constant voltage and constant current state, corresponding V _FB=V _{Ref_CV}, V _CS=V _{Ref_CC}:

$i_{M1}=i_{M2}=i_{M4}=i_{M5}={\mathrm{<figure-callout\; id="11"\; label="i\; M"\; filenames="HSA00000528935300022.png"\; state="\{\{state\}\}">i</figure-callout>}}_M=i_{M6}=i_{M7}=\frac{1}{2}*i,$ Wherein, i _M1Be the electric current of a PMOS pipe M1, i _M2Be the electric current of the 2nd PMOS pipe M2, i _M4Be the electric current of the 2nd NMOS pipe M4, i _M5Be the electric current of the 3rd NMOS pipe M5, i _M11Be the electric current of the 4th NOMS pipe M11, according to Fig. 4 and above-mentioned current value, easily obtain i _M9=i _M10=0, now the 6th NMOS pipe M9 and the 7th NMOS pipe M10 are in critical conduction mode, and constant-current amplifier 306 does not affect constant-voltage amplifier 305, and the constant voltage effect of controlled system and constant current effect are all unaffected.In this state corresponding diagram 5, horizontal ordinate i is ilmt, the point that ordinate is Vc, i.e. point (ilmt, Vc) in Fig. 5;

When controlled system is operated in constant current state, i.e. V _FB<V _{Ref_CV}, V _CS=V _{Ref_CC}The time:

When output voltage close to constant voltage value, correspondence $\left(V_{\mathrm{ref}\_\mathrm{CV}}\right)>V_{\mathrm{FB}}>(V_{\mathrm{ref}\_\mathrm{CV}}-\frac{i}{g_{m1}})$ The time,

$i_{M2}=i_{M4}=i_{M5}=i_{\mathrm{<figure-callout\; id="11"\; label="M"\; filenames="HSA00000528935300022.png"\; state="\{\{state\}\}">M</figure-callout>}11}<\frac{1}{2}*i,$ $i_{M6}=i_{M7}=\frac{1}{2}*i,$

${\mathrm{<figure-callout\; id="10"\; label="i\; M"\; filenames="HSA00000528935300022.png"\; state="\{\{state\}\}">i</figure-callout>}}_M=i_{M9}=i_{M7}-i_{M4}=\frac{1}{2}*i-i_{M4}>0,$ The electric current that now flows out the VC node is

${\mathrm{<figure-callout\; id="11"\; label="i\; M"\; filenames="HSA00000528935300022.png"\; state="\{\{state\}\}">i</figure-callout>}}_M+{\mathrm{<figure-callout\; id="10"\; label="i\; M"\; filenames="HSA00000528935300022.png"\; state="\{\{state\}\}">i</figure-callout>}}_M=i_{M4}+(\frac{1}{2}*i-i_{M4})=\frac{1}{2}*i=i_{M7}=i_{M6},$ Therefore, the constant current effect of controlled system is not subject to the impact of constant-voltage amplifier 305.In this state respective figure figure tetra-, horizontal ordinate i is from ia to ilmt, the interval (solid line) of ordinate V from Va to Vc;

When output voltage far below constant voltage value, correspondence

The time, i _M2=i _M4=i _M5=i _M11=0, M11 is in off state, and constant-voltage amplifier 305 breaks from controlled system, and the constant current effect of controlled system is not subject to the impact of constant-voltage amplifier 305.In this state corresponding diagram 5, horizontal ordinate equals ilmt, the interval of ordinate V from 0 to Va.

Therefore, non-ideality during constant pressure and flow switching that the present invention can full remuneration causes due to constant-current amplifier 306 and the limited mutual conductance of constant-voltage amplifier 305, realize the perfection switching of constant pressure and flow.

Simultaneously, the present invention also provides a kind of constant pressure and flow switching compensation method, wherein, comprise,

Utilize a constant-current amplifier to produce constant current signal;

Utilize a constant-voltage amplifier to produce the constant voltage signal;

Utilize a state controller to receive described constant current signal and described constant voltage signal, control controlled system;

Be operated in pressure constant state and the output current stage close to constant current value in described controlled system, the electric current that described constant-current amplifier is extracted from described constant-voltage amplifier compensates;

Be operated in constant current state and the output voltage stage close to the constant voltage value in described controlled system, the electric current that described constant-voltage amplifier is offered to described constant-current amplifier compensates.

Wherein, above-mentioned constant pressure and flow switching compensation method, specifically can adopt circuit as shown in Figure 4 to realize.

In sum, constant pressure and flow control circuit of the present invention, from the basic reason of constant-voltage amplifier and constant-current amplifier switch step generation interference, set about, by CCEA and the CVEA mended circuit, in the output of constant pressure and flow switch step, compensate, eliminated in constant voltage and constant current handoff procedure, between one section Current Zone of the non-constant voltage of electric current also non-constant current, make circuit can realize harmless switching in constant voltage and constant current.

Will be appreciated that, the above embodiments are only as exemplifying and propose preferred embodiment of the present invention, and the present invention also not only is confined to this, and the various simple modifications that those skilled in the art can implement also should fall within the scope of protection of the present invention.

Claims (7)

1. a constant pressure and flow control circuit, is characterized in that,

The first variable module, described the first variable module is exported the first constant signal, and described the first constant signal can increase or reduce within the first stage;

The second variable module, described the second variable module is exported the second constant signal, and described the second constant signal can increase or reduce in subordinate phase;

Compensating module, with described the first variable module, with described the second variable module, be connected respectively, described compensating module is within the described first stage, and described the first constant signal is increased or the value that reduces compensates, and makes described the first constant signal constant within the described first stage; Described compensating module is in described subordinate phase, and described the second constant signal is increased or the value that reduces compensates, and makes described the second constant signal constant in described subordinate phase.

2. constant pressure and flow control circuit according to claim 1, it is characterized in that, described the first variable module is constant-voltage amplifier, described the second variable module is constant-current amplifier, described the first constant signal is the constant voltage signal, and the described first stage is that controlled system that described control circuit is controlled is operated in the pressure constant state process and the output current of described controlled system approaches stage of constant current value; Described the second constant signal is constant current signal, and described subordinate phase is that described controlled system is operated in the constant current state process and the output voltage of described controlled system approaches stage of constant voltage; Extract electric current at described constant-current amplifier of described first stage from described constant-voltage amplifier, in described subordinate phase, described constant-voltage amplifier offers described constant-current amplifier electric current.

3. constant pressure and flow control circuit according to claim 2, is characterized in that, termination first reference voltage in two input ends of described constant-voltage amplifier, the first feedback voltage of another termination output current; Described constant-current amplifier two input ends in termination second reference voltage, the second feedback voltage of the described output current of another termination.

4. constant pressure and flow control circuit according to claim 3, is characterized in that, also comprises state controller, for the output signal according to described constant-voltage amplifier or constant-current amplifier, controls described controlled system output voltage or output current.

5. according to the described circuit of claim 3 or 4, it is characterized in that,

Described constant-voltage amplifier comprises: the first current source is connected with the source electrode of a PMOS pipe and the 2nd PMOS pipe; The grid of a described PMOS pipe connects described the first feedback voltage, and drain electrode connects grid and the drain electrode of a NMOS pipe; The grid of described the 2nd PMOS pipe connects described the first reference voltage, and drain electrode connects grid and the drain electrode of the 2nd NMOS pipe; A described NMOS pipe source electrode is connected with the source electrode of described the 2nd NMOS pipe, and equal ground connection;

Described compensating module comprises: tail current source, and its input current is 1/2nd of described the first current source input current; The 3rd NMOS pipe, its grid is connected with the grid of described the 2nd NMOS pipe, and the source electrode of described the 3rd NMOS pipe is connected with the source electrode of described the 2nd NMOS pipe; The 4th NMOS pipe, its source electrode is connected with the source electrode of described the 3rd NMOS pipe, and the grid of described the 4th NMOS pipe connects the grid of described the 3rd NMOS pipe, and the drain electrode of described the 4th NMOS pipe connects the input node of described tail current source and described state controller;

Described constant-current amplifier comprises: the second current source is connected with the source electrode of the 3rd PMOS pipe and the 4th PMOS pipe; The grid of described the 3rd PMOS pipe connects described the second feedback voltage, and the drain electrode of described the 3rd PMOS pipe connects grid and the drain electrode of the 5th NMOS pipe; The grid of described the 4th PMOS pipe connects described the second reference voltage, and the drain electrode of described the 4th PMOS pipe connects grid and the drain electrode of the 6th NMOS pipe; The source electrode of described the 5th NMOS pipe is connected with the source electrode of described the 6th NMOS pipe, and equal ground connection; The drain electrode of described the 4th PMOS pipe connects the drain electrode of described the 6th NMOS pipe; The 7th NMOS pipe, its grid connects the grid of the 6th NMOS pipe, and the source electrode of described the 7th NMOS pipe connects the source electrode of described the 5th NMOS pipe and described the 6th NMOS pipe, and the drain electrode of described the 7th NMOS pipe connects the input node of described state controller.

6. circuit according to claim 4, is characterized in that, described state controller comprises: the PWM comparer, and one input end connects comparative voltage, and another input end connects described input node; Logic and driver module, its input end connects the output terminal of comparer; On-off element, its control end connects the output terminal of described logic and driver module, and described logic and driver module can amplify the output signal of described PWM comparer, and drive the folding of described on-off element; Voltage stabilizing diode, the end that its negative electrode connects described on-off element and inductance connects, the plus earth of voltage stabilizing diode; Electric capacity, be connected with the other end of described inductance and the output terminal of described state controller.

7. a constant pressure and flow switching compensation method, is characterized in that, comprise,

Utilize constant-current amplifier to produce constant current signal;

Utilize constant-voltage amplifier to produce the constant voltage signal;

Receive described constant current signal and described constant voltage signal, to control controlled system;

Be operated in pressure constant state and the output current stage close to constant current value in described controlled system, the electric current that described constant-current amplifier is extracted from described constant-voltage amplifier compensates;

Be operated in constant current state and the output voltage stage close to the constant voltage value in described controlled system, the electric current that described constant-voltage amplifier is offered to described constant-current amplifier compensates.

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