CN203039589U - Switch power supply and controller for controlling constant output current thereof - Google Patents

Abstract

The utility model provides a switch power supply and a controller for controlling constant output current thereof. The controller comprises a zero-cross detection circuit, a charge-discharge balancing circuit, a first comparator, a second comparator and a logic control circuit, wherein the charge-discharge balancing circuit comprises a capacitor and a charge-discharge unit. A first end of the capacitor is connected with a first input terminal of the first comparator and a second end is grounded. The charge-discharge unit provides continuous equivalent current for the capacitor in a whole switching period of the switch power supply so as to charge or discharge the capacitor. The switch power supply and the controller for controlling the constant output current thereof can improve circuit consistency.

Description

Switching Power Supply and control the controller of its constant output electric current

Technical field

The utility model relates to a kind of controller of control switch constant electrical power output current and the Switching Power Supply that comprises this controller.

Background technology

Fig. 1 is a kind of traditional inverse-excitation type constant current Drive Structure, wherein transfers to the former limit winding of isolating transformer T after ac input signal AC process rectification circuit 101 and input capacitance Cin rectification and the filtering.Switching Power Supply constant-current controller 100 is used for receiving the feedback signal FB from the auxilliary group of winding L 3 of isolating transformer T, and the primary current of sampling resistor Rs sampling isolating transformer T, and driving switch pipe 106 pass to output to the input energy by isolating transformer T.The secondary winding of isolating transformer T is connected with sustained diode 1 and output capacitance Cbulk, load can with output capacitance Cbulk parallel connection.The constant-current controller 100 that is used for the control power switch comprises: discharge and recharge balancing circuitry 200, zero cross detection circuit 129, driver 128, rest-set flip-flop 122, rest-set flip-flop 126, comparator 121, comparator 124, inverter 123, lead-edge-blanking circuit (LEB) 125.

Fig. 2 is the signal timing diagram of circuit shown in Figure 1 under the constant current operating state.

When stablizing, being in the constant current loop circuit state at circuit, Vc level (being the voltage at capacitor C 1 two ends) is triangular wave, fluctuation up and down at reference voltage V refa, sustained diode 1 ON time (being the degaussing time of isolating transformer T), switch S 2 conductings, to the ground discharge, discharging current is provided by current source I2 capacitor C 1, discharges into Vc minimum point voltage through switch S 2.At other times, switch S 1 conducting, through switch S 1 charging, charging current is provided by current source I1 power supply to capacitor C 1.

After switching tube 106 conductings, it is big that the electric current of the former limit winding L 1 of isolating transformer T becomes, and auxiliary winding L 3 induced voltages (being feedback voltage FB) are negative voltage, and the electric current on the former limit winding L 1 obtains sampled voltage Vcs by the sampling resistor sampling.Through one section ON time, when sampled voltage Vcs reached reference voltage V refb, comparator 124 upsets were through rest-set flip-flop 126, driver 128 on-off switching tubes 106.Before switching tube 106 turn-offed, I1 was always to capacitor C 1 charging.

The length of the service time of switching tube 106, the inductance peak current of being determined by reference voltage V refb determines, it is very little or be transfused to voltage compensation to suppose to open delay, then the inductance peak current is Vrefb/Rs, wherein Vrefb is the magnitude of voltage of reference voltage V refb, and Rs is the resistance value of sampling resistor Rs.

Switching tube 106 closes has no progeny, and isolating transformer T instead swashs, sustained diode 1 conducting, and auxiliary winding L 3 induced voltages (being feedback signal FB) are positive voltage, the output energy is to output.The electric current that flows through sustained diode 1 constantly reduces, and up to vanishing, corresponds to feedback signal FB that auxiliary winding L 3 senses this moment and serves as reasons and just become negatively, and next parasitic oscillation takes place.Therefore, can detect the time of afterflow of sustained diode 1 by auxiliary winding L 3, this function is finished by zero cross detection circuit 129.

Switching tube 106 closes has no progeny, and until the time of afterflow end of sustained diode 1, switch S 1 is turn-offed, switch S 2 conductings, and to the ground discharge, discharging current is I2 to capacitor C 1 through switch S 2.

After the time of afterflow of sustained diode 1 finishes, switch S 1 conducting, switch S 2 is turn-offed, current source I1 begins again node Vc(namely to capacitor C 1) charging.As Vc during greater than Vrefa, produce the corresponding signal that drives through the logical operation of comparator 121, rest-set flip-flop 122, inverter 123, rest-set flip-flop 126 and driver 128, this driving signal is opened switching tube 106.

After power tube 106 was opened, primary current became greatly gradually, turn-offs after reaching peak current.Work and so forth, reach the purpose of control constant current.

Capacitor C 1 discharge and recharge balance, following relation is arranged:

I ₁·（T-T _demag）=I ₂·T _demag

Wherein T is switch periods, T _DemagBe the degaussing time (being the time of afterflow of fly-wheel diode) of transformer secondary winding, I ₁And I ₂Be respectively the output current of current source I1 and I2 among Fig. 1.

That is constant current duty ratio:

$\frac{T_{\mathrm{demag}}}{T}=\frac{I_2}{{\mathrm{<figure-callout\; id="1"\; label="I"\; filenames="HDA00002574010300011.png,HDA00002574010300042.png"\; state="\{\{state\}\}">I</figure-callout>}}_1+I_2}$

And to reverse excitation circuit:

$I_{\mathrm{out}}=\frac{1}{2}\&CenterDot;n\&CenterDot;I_{\mathrm{pk}}\&CenterDot;\frac{T_{\mathrm{demag}}}{T}=\frac{1}{2}\&CenterDot;n\&CenterDot;I_{\mathrm{pk}}\&CenterDot;\frac{I_2}{{\mathrm{<figure-callout\; id="1"\; label="I"\; filenames="HDA00002574010300011.png,HDA00002574010300042.png"\; state="\{\{state\}\}">I</figure-callout>}}_1+I_2}$

Wherein: n is the turn ratio of the former secondary of transformer, I _PkBe former limit peak current, Iout is output current.

As from the foregoing, as long as guarantee to discharge and recharge balance, guarantee that simultaneously peak current is constant, just can guarantee the constant-current characteristics of circuit.

Can be known that by top analysis output current is relevant with the ratio of peak value comparison point, charging and discharging currents.When peak current has the ratio of change or charging and discharging currents slightly change is arranged slightly, will cause the change of output current, thereby cause being difficult to guarantee that switching power circuit has good consistency.

The utility model content

The technical problems to be solved in the utility model provides a kind of Switching Power Supply and controls the controller of its constant output electric current, can improve the consistency of circuit.

For solving the problems of the technologies described above, the utility model provides a kind of controller of control switch constant electrical power output current, comprising:

Zero cross detection circuit, the ON time of the fly-wheel diode of sense switch power supply produces the ON time signal;

Discharge and recharge balancing circuitry, under the control of described ON time signal, produce charging signals;

First comparator, its first input end receives described charging signals, and its second input receives preset first reference voltage, and its output produces first comparative result;

Second comparator, its first input end receives the crest voltage of outside input, and its second input receives the second default reference voltage, and its output produces second comparative result;

Logic control circuit produces the driving signal according to described ON time signal, first comparative result and second comparative result, to control the turn-on and turn-off of the switching tube in the described Switching Power Supply;

Wherein, the described balancing circuitry that discharges and recharges comprises:

Electric capacity, its first end connects the first input end of described first comparator, its second end ground connection;

Charge/discharge unit provides lasting equivalent current described electric capacity is charged or discharge to described electric capacity in the whole switch periods of described Switching Power Supply.

According to an embodiment of the present utility model, described charge/discharge unit comprises:

First voltage current transducer, the 3rd reference voltage that its voltage input end is received is converted to the charging current that described electric capacity is charged;

Second voltage current transducer, the input voltage that its voltage input end is received is converted to the discharging current to described capacitor discharge;

Switching circuit, be serially connected between the output of the output of described first voltage current transducer and described second voltage current transducer, regulate charging and the discharge of described electric capacity under described ON time signal controlling, making has lasting equivalent current that described electric capacity is charged in the whole switch periods of described Switching Power Supply or discharges.

According to an embodiment of the present utility model, described controller also comprises:

Test port links to each other with the voltage input end of described second voltage current transducer;

First switch, its first end links to each other with described test port, and second termination is received the 4th reference voltage;

Second switch, its first end links to each other with described test port, and second end links to each other with first end of described electric capacity via level shift and follow circuit.

According to an embodiment of the present utility model, described controller enters test and repaiies the mode transfer formula, described switching circuit is connected the output of described first voltage current transducer and the output of described second voltage current transducer, described first switch turn-offs, described second switch conducting, described test port is applied with test voltage.

According to an embodiment of the present utility model, described the 4th reference voltage is identical with described second reference voltage, and perhaps described the 4th reference voltage is that the outside crest voltage of importing obtains through peak sampling hold circuit.

According to an embodiment of the present utility model, described switching circuit comprises: the 3rd switch, its first end links to each other with the output of described first voltage current transducer and first end of electric capacity, its second end links to each other with the output of described second voltage current transducer, and its control end receives described ON time signal.

According to an embodiment of the present utility model, described switching circuit comprises: the 4th switch, its first end links to each other with the output of described first voltage current transducer, its second end links to each other with the output of described second voltage current transducer and first end of described electric capacity, and its control end receives described ON time signal.

According to an embodiment of the present utility model, described switching circuit comprises:

The 5th switch, its first end links to each other with the output of described first voltage current transducer, and its second end links to each other with first end of described electric capacity;

The 6th switch, its first end links to each other with the output of described second voltage current transducer, and its second end links to each other with first end of described electric capacity, and the control end of described the 5th switch and the 6th switch receives described ON time signal and inversion signal thereof respectively;

Described controller also comprises: the tertiary voltage power pack that described electric capacity is charged, its output connects first end of described the 6th switch, and the voltage input end of described tertiary voltage power pack links to each other with the voltage input end of described first voltage current transducer.

According to an embodiment of the present utility model, described switching circuit comprises:

The 5th switch, its first end links to each other with the output of described first voltage current transducer, and its second end links to each other with first end of described electric capacity;

The 6th switch, its first end links to each other with the output of described second voltage current transducer, and its second end links to each other with first end of described electric capacity, and the control end of described the 5th switch and the 6th switch receives described ON time signal and inversion signal thereof respectively;

The input voltage that the voltage input end of described second voltage current transducer receives is the poor of the 5th reference voltage and described the 3rd reference voltage.

According to an embodiment of the present utility model, described logic control circuit comprises:

First rest-set flip-flop, its set termination is received described ON time signal, and its reset terminal receives described first comparative result;

Inverter, its input links to each other with the output of described first rest-set flip-flop;

Second rest-set flip-flop, its set end links to each other with the output of described inverter, and its reset terminal receives described second comparative result;

Driver, its input links to each other with the output of described second rest-set flip-flop, and its output produces described driving signal.

According to an embodiment of the present utility model, the first input end of described second comparator receives the crest voltage of described outside input via the lead-edge-blanking circuit.

Described equivalent current satisfies following condition: I _RefT=I _PkT _Demag, I wherein _RefThe current value of representing described equivalent current, T are represented the switch periods of described Switching Power Supply, I _PkThe peak current of representing the former limit winding of described Switching Power Supply, T _DemagThe degaussing time of representing the secondary winding of described Switching Power Supply.

The utility model also provides a kind of Switching Power Supply, comprises above-mentioned each controller, also comprises:

Transformer, the termination of the same name of its former limit winding is received input signal, and the different name end of its auxiliary winding connects the input of described zero cross detection circuit, the end ground connection of the same name of described auxiliary winding;

Switching tube, its drain electrode connects the different name end of the former limit of described transformer winding, and its grid receives the driving signal that described controller produces, and its source electrode is via sampling resistor ground connection;

Fly-wheel diode, its anodal different name end that connects the secondary winding of described transformer, its negative pole connects end of the same name and the ground connection of described secondary winding via output capacitance.

According to an embodiment of the present utility model, described Switching Power Supply also comprises: rectifier bridge and input capacitance, the AC signal of outside input transfer to the end of the same name of the elementary winding of described transformer after via described rectifier bridge rectification and input capacitance filtering.

Compared with prior art, the utlity model has following advantage:

The controller of the control switch constant electrical power output current of the utility model embodiment can be interrelated with the ratio of peak value comparison point, charging and discharging currents, repair timing at circuit, test voltage is eliminated because both consistency problems that do not match and cause separately by applying at test port.

Description of drawings

Fig. 1 is the circuit diagram of a kind of Switching Power Supply in the prior art;

Fig. 2 is the signal waveforms of circuit shown in Figure 1;

Fig. 3 is the circuit diagram of the Switching Power Supply among the utility model first embodiment;

Fig. 4 is the circuit diagram of the Switching Power Supply among the utility model second embodiment;

Fig. 5 is the circuit diagram that discharges and recharges balancing circuitry among the utility model embodiment;

Fig. 6 is that the balancing circuitry that discharges and recharges among the utility model embodiment is repaiied circuit structure under the mode transfer formula in test;

Fig. 7 is a kind of circuit diagram of replacing form that discharges and recharges balancing circuitry among the utility model embodiment;

Fig. 8 is that the another kind that discharges and recharges balancing circuitry among the utility model embodiment is replaced the circuit diagram of form;

Fig. 9 is the circuit diagram of another the replacement form that discharges and recharges balancing circuitry among the utility model embodiment;

Figure 10 is the circuit diagram of the peak sampling hold circuit among the utility model embodiment;

Figure 11 is the signal waveforms of circuit shown in Figure 10.

Embodiment

The utility model is described in further detail below in conjunction with specific embodiments and the drawings, but should not limit protection range of the present utility model with this.

According to aforementioned analysis, the bad basic reason of switching power circuit consistency mainly is: the ratio of peak value comparison point, charging and discharging currents normally divide come control.And the circuit structure of present embodiment can be linked to each other the ratio of peak value comparison point, charging and discharging currents control, does at circuit and repaiies timing, applies test voltage by test port, can eliminate owing to both consistency problems that does not match and cause separately.

Further, by the derivation in the background technology as can be known, output current is:

$I_{\mathrm{out}}=\frac{1}{2}\&CenterDot;n\&CenterDot;I_{\mathrm{pk}}\&CenterDot;\frac{T_{\mathrm{demag}}}{T}$

If the control output current is constant, then only need control:

$I_{\mathrm{ref}}=I_{\mathrm{pk}}\&CenterDot;\frac{T_{\mathrm{demag}}}{T}$

Be I _RefT=I _PkT _Demag, I wherein _RefBe reference current, I _PkBe the peak current of former limit winding, T _DemagBe the degaussing time of secondary winding.Under the same periphery circuit conditions, can improve discharging and recharging balancing circuitry, the size of charging current and discharging current is controlled by the reference voltage of correspondence respectively, thereby obtained the circuit structure of Fig. 3 and Fig. 4.

With reference to figure 3, this Switching Power Supply mainly comprises: transformer T(comprises former limit winding L 1, secondary winding L 2 and auxiliary winding L 3), switching tube 306, sustained diode 1, sampling resistor Rs, output capacitance Cbulk, rectifier bridge 301, input capacitance Cin and controller 30, comprise the auxiliary element that some are outside in addition, in order to simplify, not do one by one and describe in detail.Need to prove that the circuit shown in Fig. 3 is operated under the normal mode, but not the mode transfer formula is repaiied in test.

Wherein, the AC signal AC of outside input produces the input signal of former limit winding L 1 end of the same name that transfers to transformer T via after rectifier bridge 301 rectifications and the input capacitance Cin filtering, and the different name end of former limit winding L 1 connects the drain electrode of switching tube 306.The grid of switching tube 306 receives the driving signal GD that controller 30 produces, and source electrode is via sampling resistor Rs ground connection.The positive pole of sustained diode 1 connects the different name end of the secondary winding L 2 of transformer T, and the negative pole of sustained diode 1 connects the end of output capacitance Cbulk, and the other end of output capacitance Cbulk connects end of the same name and the ground connection of secondary winding L 2.The two ends of output capacitance Cbulk can shunt load, for example load LED etc.

The end ground connection of the same name of auxiliary winding L 3, different name end output feedback signal FB is to controller 30.Controller 30 produces driving signal GD according to the sampled voltage Vcs at feedback signal FB and sampling resistor Rs two ends, in order to the turn-on and turn-off of control switch pipe 306.

Furthermore, controller 30 comprises: zero cross detection circuit 329, discharge and recharge balancing circuitry 300, first comparator 321, second comparator 324, lead-edge-blanking circuit (LEB) 325, logic control circuit.

Wherein, zero cross detection circuit 329 receives the feedback signal FB of auxiliary winding L 3 outputs, and the ON time for detection of the sustained diode 1 of Switching Power Supply produces ON time signal Tdemag.Discharge and recharge balancing circuitry 300 and under the control of ON time signal Tdemag, produce charging signals.The first input end of first comparator 321 receives the charging signals that discharges and recharges balancing circuitry 300 outputs, and second termination is received preset first reference voltage Vrefa, and output produces first comparative result.The first input end of second comparator 324 is via the crest voltage Vcs at lead-edge-blanking circuit 325 reception sampling resistor Rs two ends, and second input receives the second default reference voltage V refb, and output produces second comparative result.Logic control circuit produces according to ON time signal Tdemag, first comparative result and second comparative result and drives signal GD, drives the turn-on and turn-off that signal GD is used for the switching tube 306 of control switch power supply.

Those skilled in the art are to be understood that, though the first input end of second comparator 324 receives crest voltage Vcs via lead-edge-blanking circuit 325 in the present embodiment, but in other specific embodiments, the first input end of second comparator 324 also can directly receive this crest voltage Vcs.

More specifically, discharging and recharging balancing circuitry 300 comprises: capacitor C 1, charge/discharge unit.Wherein, the first end Vc of capacitor C 1 connects the first input end of first comparator 321, the second end ground connection of capacitor C 1.Charge/discharge unit provides lasting equivalent current capacitor C 1 is charged or discharge to capacitor C 1 in the whole switch periods of Switching Power Supply, also namely in whole switch periods, has a constant equivalent current that capacitor C 1 is carried out charge or discharge.

As a nonrestrictive example, charge/discharge unit comprises the first voltage current transducer I3, second voltage current transducer I4 and the switching circuit in the present embodiment.Wherein, the first voltage current transducer I3 is converted to the charging current that capacitor C 1 is charged with the 3rd reference voltage V ref1 that its voltage input end receives.The input voltage that second voltage current transducer receives its voltage input end is converted to the discharging current that capacitor C 1 is discharged.Switching circuit is serially connected between the output of the output of the first voltage current transducer I3 and the second voltage current transducer I4, charging and discharge to capacitor C 1 under the control of ON time signal Tdemag are regulated, and making has lasting equivalent current that capacitor C 1 is charged in the whole switch periods of Switching Power Supply or discharge (output current that is specially the first voltage current transducer I3 among the embodiment shown in Figure 3 continues capacitor C 1 is charged).More specifically, equivalent current satisfies following condition: I _RefT=I _PkT _Demag, I wherein _RefThe current value of expression equivalent current, T represents the switch periods of Switching Power Supply, I _PkThe peak current of the former limit winding of expression Switching Power Supply, T _DemagThe degaussing time of the secondary winding of expression Switching Power Supply.

After when the charging current of capacitor C 1 and discharging current reach balance, the expression discharging current is identical to the integration of whole switch periods with charging current to the integration of output current duration, thereby the average current that output reaches is directly proportional with reference current.

In Fig. 3 and example shown in Figure 5, switching circuit comprises that specifically the 3rd switch S 4, its first end link to each other with the output of the first voltage current transducer I3 and the first end Vc of capacitor C 1, its second end links to each other with the output of the second voltage current transducer I4, and its control end receives above-mentioned ON time signal Tdemag.

Fig. 4 and switching circuit shown in Figure 3 all are the structures under normal mode of operation, the circuit structure of the two is basic identical, difference only is that the input voltage that the voltage input end of the second voltage current transducer I4 among Fig. 3 receives is the second reference voltage V refb, and the input voltage that the voltage input end of the second voltage current transducer I4 receives in Fig. 4 to be crest voltage Vcs obtain through peak sampling hold circuit 327.

The concrete structure of peak sampling hold circuit and operation principle see also Figure 10 and Figure 11, and particularly, this peak sampling hold circuit comprises switch S 10 and capacitor C s.Wherein, first termination of switch S 10 is received crest voltage Vcs, and second end connects the end of capacitor C s, and control end receives signal GD1; And the other end ground connection of capacitor C s.Wherein, signal GD1 can obtain according to the driving signal GD shown in Fig. 3, Fig. 4, is specially driving signal GD to deduct lead-edge-blanking (LEB) time and get final product.Be logic when high at signal GD1, crest voltage Vcs is sampled; Keep during for logic low at signal GD1, thereby obtain representing the sampled voltage Vsa of former limit peak current.

Still with reference to figure 5, discharge and recharge in the balancing circuitry at this, suppose:

I ₃=K _aV _ref1/R ₁；

I ₄=K _bV _ref2/R ₂；

Wherein, K _a, K _bBe the deviation factor that causes in the circuit fabrication process, generally close to 1.Equivalent resistance when R1, R2 are the voltage transitions electric current, V _Ref1And V _Ref2Be respectively the magnitude of voltage of the 3rd reference voltage V ref1 and the 4th reference voltage V ref2, I ₃And I ₄It is respectively the output current of the first voltage current transducer I3 and the second voltage current transducer I4.

With previous analysis classes seemingly, the constant current duty ratio:

$\frac{T_{\mathrm{demag}}}{T}=\frac{K_a\&CenterDot;{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HDA00002574010300011.png"\; state="\{\{state\}\}">R</figure-callout>}}_2\&CenterDot;V_{\mathrm{ref}1}}{K_b\&CenterDot;{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="HDA00002574010300011.png,HDA00002574010300042.png"\; state="\{\{state\}\}">R</figure-callout>}}_1\&CenterDot;{\mathrm{<figure-callout\; id="2"\; label="V\; ref"\; filenames="HDA00002574010300011.png"\; state="\{\{state\}\}">V</figure-callout>}}_{\mathrm{ref}}}$

Therefore, the constant current duty ratio is a parameter relevant with process deviation in the Chang Gui circuit.Only do above-mentioned improvement, limited to the conforming improvement of circuit.

With reference to figure 6, as a preferred embodiment, the controller of present embodiment also comprises: test port 401, first switch S 5 and second switch S6.Wherein test port 401 links to each other with the voltage input end of the second voltage current transducer I4; First end of first switch S 5 links to each other with test port 401, and second termination is received the 4th reference voltage V ref2; First end of second switch S6 links to each other with test port 401, and second end links to each other with the first end Vc of capacitor C 1 via level shift and follow circuit 402.

Circuit shown in Fig. 6 is to repair structure under the mode transfer formula in test, the output of the output of the first voltage current transducer I3 and the second voltage current transducer I4 is connected (being specially 4 conductings of the 3rd switch S in Fig. 6), first switch S 5 is turn-offed, second switch S6 conducting, be applied with test voltage at described test port 401, thereby test voltage be applied on the voltage input end of the second voltage current transducer I4.

In other words, the input voltage of the voltage input end of the second voltage current transducer I4 can switch, and repaiies under the mode transfer formula in test, and its voltage input end is forced to be applied for test voltage by test port 401; Under normal mode, its voltage input end switches to and receives the 4th reference voltage V ref2.

Need to prove that the 4th reference voltage V ref2 can be default arbitrarily magnitude of voltage.For example preferably, in example shown in Figure 3, the 4th reference voltage V ref2 is identical with the second reference voltage V refb, and in example shown in Figure 4, the 4th reference voltage V ref2 is that the crest voltage Vcs of outside input obtains through peak sampling hold circuit 327.

Circuit structure shown in Figure 6 has added test and has repaiied the mode transfer formula, repaiies timing carrying out parameter, can be put into deviations such as current delivery in the test of benchmark.Particularly, as shown in Figure 6, repair in the mode transfer formula in test, circuit constitutes stable closed loop, finally reaches balance owing to discharge and recharge, and therefore has:

$V_{\mathrm{test}}=\frac{K_a\&times;{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HDA00002574010300011.png"\; state="\{\{state\}\}">R</figure-callout>}}_2\&times;V_{\mathrm{ref}1}}{K_b\&times;{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="HDA00002574010300011.png,HDA00002574010300042.png"\; state="\{\{state\}\}">R</figure-callout>}}_1}$

Wherein, V _TestExpression test voltage V _TestMagnitude of voltage.Repair under the mode transfer formula test voltage V that applies with test port 401 in test _TestRepair and transfer the 3rd reference voltage V ref1, make test voltage V _TestData be accurately, have:

${\mathrm{<figure-callout\; id="1"\; label="V\; ref"\; filenames="HDA00002574010300011.png,HDA00002574010300042.png"\; state="\{\{state\}\}">V</figure-callout>}}_{\mathrm{ref}}=\frac{K_b}{K_a}\&times;\frac{R_1}{{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HDA00002574010300011.png"\; state="\{\{state\}\}">R</figure-callout>}}_2}\&times;V_{\mathrm{test}}$

In normal mode (being constant current mode), first switch S 5 is turn-offed, second switch S6 conducting, and the 3rd switch S 4 is by ON time signal Tdemag control, after loop stability:

$K_b\&CenterDot;\frac{V_{\mathrm{ref}2}}{{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HDA00002574010300011.png"\; state="\{\{state\}\}">R</figure-callout>}}_2}\&CenterDot;T_{\mathrm{demag}}=K_a\&CenterDot;\frac{V_{\mathrm{ref}1}}{{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="HDA00002574010300011.png,HDA00002574010300042.png"\; state="\{\{state\}\}">R</figure-callout>}}_1}\&CenterDot;T$

$\frac{{\mathrm{<figure-callout\; id="2"\; label="V\; ref"\; filenames="HDA00002574010300011.png"\; state="\{\{state\}\}">V</figure-callout>}}_{\mathrm{ref}}\&CenterDot;T_{\mathrm{demag}}}{T}=\frac{K_a\&CenterDot;{\mathrm{<figure-callout\; id="1"\; label="V\; ref"\; filenames="HDA00002574010300011.png,HDA00002574010300042.png"\; state="\{\{state\}\}">V</figure-callout>}}_{\mathrm{ref}}\&CenterDot;R_2}{K_b\&CenterDot;{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="HDA00002574010300011.png,HDA00002574010300042.png"\; state="\{\{state\}\}">R</figure-callout>}}_1}=V_{\mathrm{test}}$

Preferably, the 4th reference voltage V ref2 is proportional to the i.e. voltage comparison point of second comparator of the second reference voltage V refb(), perhaps be proportional to the voltage that crest voltage Vcs obtains through sampling hold circuit, as a nonrestrictive example, be set to equate, that is: herein

$I_{\mathrm{pk}}=\frac{V_{\mathrm{ref}2}}{R_s}$

Therefore, output current is fully by test voltage V _TestDetermine, irrelevant with the transmission error of voltage current transducer, irrelevant with the magnitude of voltage value size of the 4th reference voltage V ref2:

$I_{\mathrm{out}}=\frac{1}{2}\&CenterDot;n\&CenterDot;I_{\mathrm{pk}}\&CenterDot;\frac{T_{\mathrm{demag}}}{T}=\frac{1}{2}\&CenterDot;n\&CenterDot;\frac{V_{\mathrm{test}}}{R_s}$

Therefore, adopt test voltage V in the mode transfer formula by repairing in the test of circuit _TestRepair accent, make output current fully by test voltage V _TestDetermine, greatly improved the consistency of circuit.

And for the traditional circuit shown in Fig. 1, even adopt technique scheme, also can't improve the circuit consistency, specific as follows:

Repair the mode transfer formula with switch S 1 and S2 conducting in test, current source replaced with the current source of voltage transitions electric current, suppose that the output current of two current sources is:

I ₁=K _cV _ref3/R ₃

I ₂=K _dV _ref4/R ₄

Wherein, Kc and Kd are the deviation factors that causes in the circuit fabrication process, generally close to 1.R ₃, R ₄Equivalent resistance during for the voltage transitions electric current, V _Ref3And V _Ref4Expression inputs to the voltage of two current sources respectively.

Repair under the mode transfer formula in test,

K _cV _ref3/R ₃=K _dV _test/R ₄

Under normal mode of operation:

$I_{\mathrm{out}}=\frac{1}{2}\&CenterDot;n\&CenterDot;I_{\mathrm{pk}}\&CenterDot;\frac{I_1}{I_1+I_2}=\frac{1}{2}\&CenterDot;n\&CenterDot;\frac{V_{\mathrm{ref}4}}{R_s}\&CenterDot;\frac{\frac{V_{\mathrm{ref}3}}{R_3}\&CenterDot;K_c}{\frac{V_{\mathrm{ref}3}}{R_3}\&CenterDot;K_c+\frac{V_{\mathrm{ref}4}}{{\mathrm{<figure-callout\; id="4"\; label="R"\; filenames="HDA00002574010300022.png"\; state="\{\{state\}\}">R</figure-callout>}}_4}\&CenterDot;K_d}$

Further obtain:

$I_{\mathrm{out}}=\frac{1}{2}\&CenterDot;n\&CenterDot;\frac{V_{\mathrm{ref}4}}{R_s}\&CenterDot;\frac{\frac{{\mathrm{<figure-callout\; id="4"\; label="V\; test\; R"\; filenames="HDA00002574010300022.png"\; state="\{\{state\}\}">V</figure-callout>}}_{\mathrm{test}}}{R_{}}\&CenterDot;K_d}{\frac{{\mathrm{<figure-callout\; id="4"\; label="V\; test\; R"\; filenames="HDA00002574010300022.png"\; state="\{\{state\}\}">V</figure-callout>}}_{\mathrm{test}}}{R_{}}\&CenterDot;K_d+\frac{V_{\mathrm{ref}4}}{{\mathrm{<figure-callout\; id="4"\; label="R"\; filenames="HDA00002574010300022.png"\; state="\{\{state\}\}">R</figure-callout>}}_4}\&CenterDot;K_d}$

$=\frac{1}{2}\&CenterDot;n\&CenterDot;\frac{V_{\mathrm{ref}4}}{R_s}\&CenterDot;\frac{V_{\mathrm{test}}}{V_{\mathrm{test}}+{\mathrm{<figure-callout\; id="4"\; label="V\; ref"\; filenames="HDA00002574010300022.png"\; state="\{\{state\}\}">V</figure-callout>}}_{\mathrm{ref}}}$

As from the foregoing, output current and test voltage V _TestAnd V _Ref4Relation is arranged, can not be fully by test voltage V _TestDetermine, still can influence the consistency of circuit.Only at test voltage V _TestWith V _Ref4When having fixed relationship, just can obtain consistency preferably, namely need to repair accent test voltage V _TestWith voltage V _Ref4, can increase like this and repair the pressure regulation point, make circuit more complicated, and also variation of consistency.

With reference to figure 7, Fig. 7 shows the structure that another kind discharges and recharges balancing circuitry, compares with the balancing circuitry that discharges and recharges shown in Figure 5, and variation has taken place in the position of the switch wherein.This circuit specifically comprises: the first voltage current transducer I3 is converted to charging current with the 3rd reference voltage V ref5 that receives; The second voltage current transducer I6 is converted to discharging current with the 4th reference voltage V ref6 that receives, and similarly, the 4th benchmark Vref6 can repair in test and switch to above-mentioned test voltage under the mode transfer formula; The 4th switch S 5, the first ends link to each other with the output of the first voltage current transducer I5, and second end links to each other with the output of the second voltage current transducer I6 and first end of electric capacity, and control end receives ON time signal Tdemag.

With reference to figure 8, Fig. 8 shows another structure that discharges and recharges balancing circuitry, compares with the balancing circuitry that discharges and recharges shown in Figure 5, and the tertiary voltage power pack has taken place to change and introduced switching circuit wherein.This circuit specifically comprises: the first voltage current transducer I7 is converted to charging current with the 3rd reference voltage V ref7 that receives; The 4th reference voltage V ref8 that the second voltage current transducer I9 will receive is converted to discharging current similarly, repaiies in test that the 4th reference voltage V ref8 also can switch to above-mentioned test voltage under the mode transfer formula; Tertiary voltage power pack I8, its voltage input end links to each other with the voltage input end of the first voltage current transducer I7, and that therefore receive also is the 3rd reference voltage V ref7; The 5th switch S 6, the first ends link to each other with the output of the second voltage current transducer I9 and tertiary voltage power pack I8, and second end links to each other with first end of electric capacity, and control end receives ON time signal Tdemag; The 6th switch S 7, the first ends link to each other with the output of the first voltage current transducer I7, and second end links to each other with first end of electric capacity, and control end receives the inversion signal of ON time signal Tdemag.Under this circuit structure, still have:

$\frac{T_{\mathrm{demag}}}{T}=\frac{I_7}{I_7+I_9-I_8}$

Make I ₇=I ₈, then the result is identical with previous description, still has an equivalent electric current I 7 in whole switch periods electric capacity to be charged.

With reference to figure 9, Fig. 9 shows another structure that discharges and recharges balancing circuitry, compare with the balancing circuitry that discharges and recharges shown in Figure 5, variation has taken place in switching circuit wherein, and variation has also taken place the input voltage that the voltage input end of other second voltage current transducer receives.This circuit specifically comprises: the first voltage current transducer I10 is converted to charging current with the 3rd reference voltage V ref9 that receives; The 4th reference voltage that the second voltage current transducer I11, its voltage input end receive is the poor of the 5th reference voltage V ref10 and the 3rd reference voltage V ref9, similarly, repaiies under the mode transfer formula in test, also the 4th reference voltage can be switched to test voltage; The 5th switch S 8, the first ends link to each other with the output of the second voltage current transducer I11, and second end links to each other with first end of electric capacity, and control end receives ON time signal Tdemag; The 6th switch S 9, the first ends link to each other with the output of the first voltage current transducer I10, and second end links to each other with first end of electric capacity, and the control end of the 6th switch S 9 receives the inversion signal of ON time signal Tdemag.Under circuit structure shown in Figure 9, in whole switch periods, still have an equivalent electric current (i.e. the electric current that the 3rd reference voltage V ref9 conversion produces) constantly electric capacity to be charged.

Though the utility model with preferred embodiment openly as above; but it is not to limit the utility model; any those skilled in the art are not in breaking away from spirit and scope of the present utility model; can make possible change and modification, therefore protection range of the present utility model should be as the criterion with the scope that the utility model claim is defined.

Claims (13)

1. the controller of a control switch constant electrical power output current comprises:

Zero cross detection circuit, the ON time of the fly-wheel diode of sense switch power supply produces the ON time signal;

Discharge and recharge balancing circuitry, under the control of described ON time signal, produce charging signals;

First comparator, its first input end receives described charging signals, and its second input receives preset first reference voltage, and its output produces first comparative result;

Second comparator, its first input end receives the crest voltage of outside input, and its second input receives the second default reference voltage, and its output produces second comparative result;

Logic control circuit produces the driving signal according to described ON time signal, first comparative result and second comparative result, to control the turn-on and turn-off of the switching tube in the described Switching Power Supply;

It is characterized in that the described balancing circuitry that discharges and recharges comprises:

Electric capacity, its first end connects the first input end of described first comparator, its second end ground connection;

Charge/discharge unit provides lasting equivalent current described electric capacity is charged or discharge to described electric capacity in the whole switch periods of described Switching Power Supply.

2. controller according to claim 1 is characterized in that, described charge/discharge unit comprises:

First voltage current transducer, the 3rd reference voltage that its voltage input end is received is converted to the charging current that described electric capacity is charged;

Second voltage current transducer, the input voltage that its voltage input end is received is converted to the discharging current to described capacitor discharge;

Switching circuit, be serially connected between the output of the output of described first voltage current transducer and described second voltage current transducer, regulate charging and the discharge of described electric capacity under described ON time signal controlling, making has lasting equivalent current that described electric capacity is charged in the whole switch periods of described Switching Power Supply or discharges.

3. controller according to claim 2 is characterized in that, also comprises:

Test port links to each other with the voltage input end of described second voltage current transducer;

First switch, its first end links to each other with described test port, and second termination is received the 4th reference voltage;

Second switch, its first end links to each other with described test port, and second end links to each other with first end of described electric capacity via level shift and follow circuit.

4. controller according to claim 3, it is characterized in that, described controller enters test and repaiies the mode transfer formula, described switching circuit is connected the output of described first voltage current transducer and the output of described second voltage current transducer, described first switch turn-offs, described second switch conducting, described test port is applied with test voltage.

5. controller according to claim 3 is characterized in that, described the 4th reference voltage is identical with described second reference voltage, and perhaps described the 4th reference voltage is that the outside crest voltage of importing obtains through peak sampling hold circuit.

6. controller according to claim 2, it is characterized in that, described switching circuit comprises: the 3rd switch, its first end links to each other with the output of described first voltage current transducer and first end of electric capacity, its second end links to each other with the output of described second voltage current transducer, and its control end receives described ON time signal.

7. controller according to claim 2, it is characterized in that, described switching circuit comprises: the 4th switch, its first end links to each other with the output of described first voltage current transducer, its second end links to each other with the output of described second voltage current transducer and first end of described electric capacity, and its control end receives described ON time signal.

8. controller according to claim 2 is characterized in that, described switching circuit comprises:

The 5th switch, its first end links to each other with the output of described first voltage current transducer, and its second end links to each other with first end of described electric capacity;

The 6th switch, its first end links to each other with the output of described second voltage current transducer, and its second end links to each other with first end of described electric capacity, and the control end of described the 5th switch and the 6th switch receives described ON time signal and inversion signal thereof respectively;

Described controller also comprises: the tertiary voltage power pack that described electric capacity is charged, its output connects first end of described the 6th switch, and the voltage input end of described tertiary voltage power pack links to each other with the voltage input end of described first voltage current transducer.

9. controller according to claim 2 is characterized in that, described switching circuit comprises:

The 5th switch, its first end links to each other with the output of described first voltage current transducer, and its second end links to each other with first end of described electric capacity;

The 6th switch, its first end links to each other with the output of described second voltage current transducer, and its second end links to each other with first end of described electric capacity, and the control end of described the 5th switch and the 6th switch receives described ON time signal and inversion signal thereof respectively;

The input voltage that the voltage input end of described second voltage current transducer receives is the poor of the 5th reference voltage and described the 3rd reference voltage.

10. controller according to claim 1 is characterized in that, described logic control circuit comprises:

First rest-set flip-flop, its set termination is received described ON time signal, and its reset terminal receives described first comparative result;

Inverter, its input links to each other with the output of described first rest-set flip-flop;

Second rest-set flip-flop, its set end links to each other with the output of described inverter, and its reset terminal receives described second comparative result;

Driver, its input links to each other with the output of described second rest-set flip-flop, and its output produces described driving signal.

11. controller according to claim 1 is characterized in that, the first input end of described second comparator receives the crest voltage of described outside input via the lead-edge-blanking circuit.

12. a Switching Power Supply is characterized in that, comprises each described controller in the claim 1 to 11, also comprises:

Transformer, the termination of the same name of its former limit winding is received input signal, and the different name end of its auxiliary winding connects the input of described zero cross detection circuit, the end ground connection of the same name of described auxiliary winding;

Switching tube, its drain electrode connects the different name end of the former limit of described transformer winding, and its grid receives the driving signal that described controller produces, and its source electrode is via sampling resistor ground connection;

Fly-wheel diode, its anodal different name end that connects the secondary winding of described transformer, its negative pole connects end of the same name and the ground connection of described secondary winding via output capacitance.

13. Switching Power Supply according to claim 12 is characterized in that, also comprises: rectifier bridge and input capacitance, the AC signal of outside input transfer to the end of the same name of the elementary winding of described transformer after via described rectifier bridge rectification and input capacitance filtering.

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