CN104702095A - Switching power supply controller and switching power supply comprising switching power supply controller - Google Patents

Abstract

The invention provides a switching power supply controller and a switching power supply comprising the switching power supply controller. The controller comprises a zero crossing detection circuit for performing zero crossing detection on an input feedback signal and generating a zero crossing detection, an on time detection circuit for detecting the on time of a switching tube in the switching power supply to obtain an on time timing voltage, a switching cycle time detection circuit for detecting the switching cycle time of the switching tube to obtain a switching cycle time timing voltage, an on time length control circuit for generating an off signal according to the on time timing voltage, the switching cycle time timing voltage and a compensating voltage so that the on time of the switching tube is correlated to the on time timing voltage and the switching cycle time timing voltage, and a driving signal generation circuit for generating a driving signal according to the zero-crossing signal and the off signal. The switching power supply controller is capable of optimizing the power factor of the switching power supply controlled by a critical on mode and reducing total harmonic distortion.

Description

Switch power controller and comprise the Switching Power Supply of this switch power controller

Technical field

The present invention relates to switch power technology, particularly relate to a kind of switch power controller with power factor adjustment function, critical conduction mode control, and comprise the Switching Power Supply of this switch power controller.

Background technology

Traditional Alternating Current Power Supply, band power factor adjustment (PFC) function, critical conduction mode isolation constant current driver circuit for LED as shown in Figure 1, mainly comprise: AC input rectification circuit 101, interchange input source 102, input capacitance Cin, resistance 104, electric capacity 105, diode 106, isolating transformer T1, power switch 112, sampling resistor Rs, resistance 113, output rectifier diode D1, output capacitance Cbulk, constant-current switch power source controller 100.Wherein, controller 100 is for receiving the feedback signal FB of the auxiliary group of winding L 3 from isolating transformer T1, the primary current of the former limit winding L 1 of sampling resistor Rs sampling isolating transformer T1, and driving power switch 112, extremely exported input energy transferring by isolating transformer T1.

Constant-current switch power source controller 100 comprises: zero cross detection circuit 125, for detect drive singal GD terminate after feedback signal FB zero passage, what provide power switch 112 when feedback signal FB zero passage opens signal, conducting power switch 112, zero cross detection circuit 125 also obtains the degaussing time Tdemag of transformer T1, and transmits it to constant-current control circuit 120; Constant current counting circuit 120, former limit peak current is obtained by carrying out sampling to the voltage on sampling resistor Rs, the degaussing time Tdemag of transformer T1 is obtained by zero cross detection circuit 125, this degaussing time Tdemag is exactly the current lead-through time exporting rectifier diode D1, is calculated the size of output current by former limit peak current, transformer degaussing time Tdemag; Error amplifier 121, the output current that constant current counting circuit 120 calculates and reference current do error and amplify, and output error voltage COMP, error voltage COMP connect building-out capacitor 114, and after making loop stability, error voltage COMP is substantially fixing; ON time length control circuit 122, control the ON time length of power switch 112, timing is started when power switch 112 starts conducting, when reaching the ON time of setting, exporting cut-off signals to trigger 123, removing switch-off power switch 112, after loop stability, when error voltage COMP fixes, the ON time consistent length of power switch 112, realizes power factor adjustment thus; Trigger 123, receives the zero cross signal ZCD of zero cross detection circuit 125 output and the cut-off signals of ON time length control circuit 122 output; Drive circuit 124, connects the drive end of trigger 123 and power switch 112, realizes turning on and off driving to power switch 112.

For realizing good power factor Adjustment effect, require that the AC input current of each switch periods well can follow the change of input voltage.Under critical conduction mode, ignore pressure drop when exporting rectifier diode pressure drop, input rectifying tube voltage drop, power switch conducting, the average current input of each switch periods is:

$I_{\mathrm{in}}=\frac{1}{2}\·\frac{n\·V_{\mathrm{out}}}{V_{\mathrm{in}}+n\·V_{\mathrm{out}}}\·\frac{T_{\mathrm{on}}\·V_{\mathrm{in}}}{L}---\left(1\right)$

Wherein, n is the former limit winding L 1 of transformer T1 and the turn ratio of vice-side winding L2, V _outfor output voltage, V _infor input voltage, I _infor input current, T _onfor ON time, L is the inductance of former limit winding L 1.Fixing ON time is adopted (to be also T _onconstant), critical conduction mode control time, input current I _ininput voltage V can not be followed completely _inchange, power factor is deteriorated, and total harmonic distortion strengthens, and input voltage V _inhigher, deviation is larger, so the power factor of circuit traditional is at present not good especially, total harmonic distortion is also larger.

Summary of the invention

The technical problem to be solved in the present invention is to provide a kind of switch power controller and comprises the Switching Power Supply of this switch power controller, can optimize the power factor of the Switching Power Supply that critical conduction mode controls, and reduces total harmonic distortion.

For solving the problems of the technologies described above, the invention provides a kind of switch power controller, comprising:

Zero cross detection circuit, carries out zero passage detection to the feedback signal of input and produces zero cross signal;

ON time testing circuit, detects the ON time of the switching tube in Switching Power Supply, to obtain ON time timing voltage;

Switch periods time detection circuit, detected the switch periods time of described switching tube, to obtain switch periods time timing voltage;

ON time length control circuit, be connected with the output of described ON time testing circuit, the output of switch periods time detection circuit, and receive bucking voltage, produce cut-off signals according to described ON time timing voltage, switch periods time timing voltage and bucking voltage, be associated with described ON time timing voltage, switch periods time timing voltage to make the ON time of described switching tube;

Drive signal generation circuit, produce drive singal according to described zero cross signal and cut-off signals, described drive singal transfers to the drive end of described switching tube, and in response to described zero cross signal, described drive singal controls described switching tube conducting; In response to described cut-off signals, described drive singal controls described switching tube and turns off.

According to one embodiment of present invention, the magnitude of voltage of described ON time timing voltage is proportional to the ON time of described switching tube, described switch periods time timing voltage is proportional to the switch periods time of described switching tube, the cut-off signals that described ON time length control module produces makes described ON time reduce with the increase of described ON time timing voltage, and increases with the increase of described switch periods time timing voltage.

According to one embodiment of present invention, the cut-off signals that described ON time length control module produces makes the ON time Ton of described switching tube meet following relation: V _ton× Ton/V _tkeep fixing, wherein, V _tonfor described ON time timing voltage, V _tfor described switch periods time timing voltage.

According to one embodiment of present invention, the ON time timing voltage that described ON time testing circuit obtains represents the ON time of described switching tube in previous switch periods, or represents the mean value of the ON time of described switching tube in front multiple switch periods.

According to one embodiment of present invention, the switch periods time timing voltage that described switch periods time detection circuit obtains represents the switch periods time of described switching tube in previous switch periods, or represents the mean value of the switch periods time of described switching tube in front multiple switch periods.

According to one embodiment of present invention, the input of described ON time testing circuit is directly connected with the drive end of described switching tube, to detect the ON time of described switching tube.

According to one embodiment of present invention, the input of described switch periods time detection circuit is directly connected with the drive end of described switching tube, to detect the switch periods time of described switching tube.

According to one embodiment of present invention, described switch power controller also comprises:

Constant current counting circuit, samples to the primary current of the switching tube flowing through described Switching Power Supply, obtains former limit peak current, and the transformer degaussing Time Calculation output current exported by described former limit peak current and described zero cross detection circuit;

Error amplifier, carry out error amplification, output error voltage to the output current that described constant current counting circuit exports with the reference current preset, described error voltage is applied on loop compensation electric capacity to obtain described bucking voltage.

According to one embodiment of present invention, described switch power controller also comprises:

Voltage sampling circuit, samples to the voltage of the output of described Switching Power Supply, obtains exporting sampled voltage;

Error amplifier, carry out error amplification, output error voltage to the sampled voltage that described voltage sampling circuit exports with the reference voltage preset, described error voltage is applied on loop compensation electric capacity to obtain described bucking voltage.

According to one embodiment of present invention, described drive signal generation circuit comprises: rest-set flip-flop, and its set input receives described zero cross signal, and its RESET input receives described cut-off signals, and its output produces described drive singal.

According to one embodiment of present invention, described drive signal generation circuit also comprises: driver, and described drive singal transfers to the drive end of described switching tube via described driver.

According to one embodiment of present invention, described ON time testing circuit comprises:

First current source;

First switch, its first end connects the output of described first current source;

Second switch, its first end connects the second end of described first switch, its second end ground connection;

First electric capacity, its first end connects the second end of described first switch and the first end of described second switch, its second end ground connection;

Voltage follower, its input connects the first end of described first electric capacity;

3rd switch, its first end connects the output of described voltage follower;

Second electric capacity, its first end connects the second end of described 3rd switch, and its second end ground connection, the second end of described second electric capacity exports described ON time timing voltage.

According to one embodiment of present invention, in response to described switching tube conducting, described first switch conduction, described second switch and the 3rd switch OFF, described first current source, to described first capacitor charging, makes the voltage at described first electric capacity two ends be directly proportional to the ON time of described switching tube; Turn off in response to described switching tube, described first switch and second switch turn off, described 3rd switch conduction, and the voltage at described first electric capacity two ends is maintained and is passed to described second electric capacity via described voltage follower and the 3rd switch; After turning off Preset Time in response to described switching tube, described first switch and the 3rd switch OFF, described second switch conducting, the voltage at described first electric capacity two ends resets, and the voltage on described second electric capacity remains unchanged.

According to one embodiment of present invention, described ON time length control circuit comprises:

Second current source;

3rd electric capacity, its first end connects the output of described second current source, its second end ground connection;

4th switch, its first end connects the first end of described 3rd electric capacity, and its second end connects the second end of described 3rd electric capacity;

Comparator, its first input end connects the first end of described 3rd electric capacity, and its second input receives the reference voltage preset, and its output is for exporting described cut-off signals.

In order to solve the problem, present invention also offers a kind of Switching Power Supply, comprise switch power controller and coupled peripheral circuit, wherein, described switch power controller comprises:

Zero cross detection circuit, carries out zero passage detection to the feedback signal of input and produces zero cross signal;

ON time testing circuit, detects the ON time of the switching tube in Switching Power Supply, to obtain ON time timing voltage;

Switch periods time detection circuit, detected the switch periods time of described switching tube, to obtain switch periods time timing voltage;

ON time length control circuit, be connected with the output of described ON time testing circuit, the output of switch periods time detection circuit, and receive bucking voltage, cut-off signals is produced according to described ON time timing voltage, switch periods time timing voltage and bucking voltage, be associated with described ON time timing voltage, switch periods time timing voltage to make the ON time of described switching tube

Drive signal generation circuit, produce drive singal according to described zero cross signal and cut-off signals, described drive singal transfers to the drive end of described switching tube, and in response to described zero cross signal, described drive singal controls described switching tube conducting; In response to described cut-off signals, described drive singal controls described switching tube and turns off.

According to one embodiment of present invention, the magnitude of voltage of described ON time timing voltage is proportional to the ON time of described switching tube, described switch periods time timing voltage is proportional to the switch periods time of described switching tube, increase in response to described ON time timing voltage, the cut-off signals that described ON time length control module produces makes described ON time reduce, increase in response to described switch periods time timing voltage, the cut-off signals that described ON time length control module produces makes described ON time increase.

According to one embodiment of present invention, the cut-off signals that described ON time length control module produces makes the ON time Ton of described switching tube meet following relation: V _ton× Ton/V _tkeep fixing, wherein, V _tonfor described ON time timing voltage, V _tfor described switch periods time timing voltage.

According to one embodiment of present invention, the ON time timing voltage that described ON time testing circuit obtains represents the ON time of described switching tube in previous switch periods, or represents the mean value of the ON time of described switching tube in front multiple switch periods.

According to one embodiment of present invention, the switch periods time timing voltage that described switch periods time detection circuit obtains represents the switch periods time of described switching tube in previous switch periods, or represents the mean value of the switch periods time of described switching tube in front multiple switch periods.

The switch periods time timing voltage that described switch periods time detection circuit obtains represents the switch periods time of described switching tube in previous switch periods, or represents the mean value of the switch periods time of described switching tube in front multiple switch periods.

According to one embodiment of present invention, the input of described ON time testing circuit is directly connected with the drive end of described switching tube, to detect the ON time of described switching tube.

According to one embodiment of present invention, the input of described switch periods time detection circuit is directly connected with the drive end of described switching tube, to detect the switch periods time of described switching tube.

According to one embodiment of present invention, described switch power controller also comprises:

Constant current counting circuit, samples to the primary current of the switching tube flowing through described Switching Power Supply, obtains former limit peak current, and the transformer degaussing Time Calculation output current exported by described former limit peak current and described zero cross detection circuit;

Error amplifier, carry out error amplification, output error voltage to the output current that described constant current counting circuit exports with the reference current preset, described error voltage is applied on loop compensation electric capacity to obtain described bucking voltage.

According to one embodiment of present invention, described switch power controller also comprises:

Voltage sampling circuit, samples to the voltage of the output of described Switching Power Supply, obtains exporting sampled voltage;

Error amplifier, carry out error amplification, output error voltage to the sampled voltage that described voltage sampling circuit exports with the reference voltage preset, described error voltage is applied on loop compensation electric capacity to obtain described bucking voltage.

According to one embodiment of present invention, described drive signal generation circuit comprises: rest-set flip-flop, and its set input receives described zero cross signal, and its RESET input receives described cut-off signals, and its output produces described drive singal.

According to one embodiment of present invention, described drive signal generation circuit also comprises: driver, and described drive singal transfers to the drive end of described switching tube via described driver.

According to one embodiment of present invention, described ON time testing circuit comprises:

First current source;

First switch, its first end connects the output of described first current source;

Second switch, its first end connects the second end of described first switch, its second end ground connection;

First electric capacity, its first end connects the second end of described first switch and the first end of described second switch, its second end ground connection;

Voltage follower, its input connects the first end of described first electric capacity;

3rd switch, its first end connects the output of described voltage follower;

Second electric capacity, its first end connects the second end of described 3rd switch, and its second end ground connection, the second end of described second electric capacity exports described ON time timing voltage.

According to one embodiment of present invention, in response to described switching tube conducting, described first switch conduction, described second switch and the 3rd switch OFF, described first current source, to described first capacitor charging, makes the voltage at described first electric capacity two ends be directly proportional to the ON time of described switching tube; Turn off in response to described switching tube, described first switch and second switch turn off, described 3rd switch conduction, and the voltage at described first electric capacity two ends is maintained and is passed to described second electric capacity via described voltage follower and the 3rd switch; After turning off Preset Time in response to described switching tube, described first switch and the 3rd switch OFF, described second switch conducting, the voltage at described first electric capacity two ends resets, and the voltage on described second electric capacity remains unchanged.

According to one embodiment of present invention, described ON time length control circuit comprises:

Second current source;

3rd electric capacity, its first end connects the output of described second current source, its second end ground connection;

4th switch, its first end connects the first end of described 3rd electric capacity, and its second end connects the second end of described 3rd electric capacity;

Comparator, its first input end connects the first end of described 3rd electric capacity, and its second input receives the reference voltage preset, and its output is for exporting described cut-off signals.

According to one embodiment of present invention, described peripheral circuit is reverse exciting topological or buck topology.

Compared with prior art, the present invention has the following advantages:

The ON time of switch power controller to the switching tube in Switching Power Supply of the embodiment of the present invention controls, make the ON time of previous or front multiple switch periods of itself and switching tube, switch periods time correlation connection, thus improve the power factor of circuit, reduce the total harmonic distortion of Switching Power Supply.

Furthermore, the switch power controller of the embodiment of the present invention makes the ON time of switching tube meet keep fixing, make input current follow input voltage change completely, realize good power factor performance.Wherein, Ton is the ON time of switching tube, and T is the switch periods time of Switching Power Supply.

Accompanying drawing explanation

Fig. 1 is a kind of electrical block diagram having power factor adjustment function, adopt the LED constant-current driver that fixing ON time controls, critical conduction mode controls of the prior art;

Fig. 2 is the electrical block diagram of Switching Power Supply according to a first embodiment of the present invention;

Fig. 3 is the structural representation of a kind of realizing circuit of ON time testing circuit in Fig. 2;

Fig. 4 is the structural representation of a kind of realizing circuit of ON time length control circuit in Fig. 2;

Fig. 5 is the electrical block diagram of Switching Power Supply according to a second embodiment of the present invention.

Embodiment

Known according to the formula (1) in background technology, can not follow input voltage completely due to input current changes because ON time is controlled as fixing causing, therefore, in order to optimizing power factor, optimize total harmonic distortion, ON time length can be revised, ON time length is revised as on-fixed amount.

Further, formula (1) is converted into following formula:

$I_{\mathrm{in}}=\frac{1}{2}\·\frac{T_{\mathrm{on}}\·T_{\mathrm{on}}}{L\·T}\·V_{\mathrm{in}}---\left(2\right)$

Wherein T is the switch periods time.

In order to good power factor can be realized, need input current to follow input voltage change completely, therefore need to ensure fixing, thus improve power factor, namely switching tube ON time square keep fixing with the ratio of switch periods.

Usually, in several switch periods that Switching Power Supply is adjacent, the ON time of switching tube is substantially the same with the switch periods time, therefore, the ON time of previous switch periods and switch periods time can be used to control the ON time of next switch periods, thus make the ON time of switching tube square with switch periods ratio keeps fix.

Below in conjunction with specific embodiments and the drawings, the invention will be further described, but should not limit the scope of the invention with this.

First embodiment

Show the circuit structure of the Switching Power Supply of the first embodiment with reference to figure 2, Fig. 2, this Switching Power Supply is reverse exciting topological, and this reverse exciting topological Switching Power Supply can be used as LED driver.As described in Figure 2, this Switching Power Supply can comprise: alternating message source 102, rectifier bridge 101, input capacitance Cin, supplying resistance 104, power supply electric capacity 105, diode 106, transformer T1 (comprises former limit winding L 1, vice-side winding L2, auxiliary winding L 3), switching tube 112, sampling resistor Rs, feedback resistance 113, loop compensation electric capacity 114, output diode D1, output capacitance Cbulk and switch power controller 200, the integrated connection mode of above-mentioned all parts is identical with conventional inverse-excitation type switch power-supply, such as identical with the Integral connection structure of Fig. 1 in background technology.

Wherein, switch power controller 200 can comprise: zero cross detection circuit 125, ON time testing circuit 126, switch periods time detection circuit 127, constant current counting circuit 120, error amplifier 121, ON time length control circuit 132, rest-set flip-flop 123, driver 124.

Wherein, the feedback signal FB of zero cross detection circuit 125 to input carries out zero passage detection and produces zero cross signal ZCD, and this feedback signal FB comes from the different name end of the auxiliary winding L 3 of transformer T1, inputs to zero cross detection circuit 125 via feedback resistance 113.Zero cross detection circuit 125 also detects the degaussing time Tdemag of transformer T1, and transmits it to constant current counting circuit 120.

The ON time of ON time testing circuit 126 sense switch pipe 112, and the ON time detected is converted to ON time timing voltage.ON time timing voltage is kept, to control the ON time of next switch periods.

The switch periods time of switch periods testing circuit 127 sense switch pipe 112, and put up with and like that you convert switch periods time timing voltage at switch periods time of measuring.This switch periods time timing voltage is kept, to control the ON time of next switch periods.

As a preferred embodiment, the input of ON time testing circuit 126 directly can be connected with the drive end of switching tube 112, with the drive singal of direct-detection switching tube 112.By the detection to drive singal, to ON time timing, ON time timing voltage V can be obtained _ton, this ON time timing voltage V _tonheight represent the length of ON time.As a nonrestrictive example, ON time timing voltage V _tonmagnitude of voltage be directly proportional to ON time.

Wherein, ON time timing voltage V _tonthe ON time of switching tube 112 in previous switch periods can be represented, or also can represent the mean value of the ON time of switching tube 112 in front multiple switch periods.

Show a kind of realizing circuit of ON time testing circuit with reference to figure 3, Fig. 3, comprising: the first current source 301; First switch S 1, its first end connects the output of the first current source 301; Second switch S2, its first end connects the second end of the first switch S 1, its second end ground connection; First electric capacity 305, its first end connects the second end of the first switch S 1 and the first end of second switch S2, its second end ground connection; Voltage follower 307, its input connects the first end of the first electric capacity 305; 3rd switch S 3, its first end connects the output of voltage follower 307; Second electric capacity 306, its first end connects the second end of the 3rd switch S 3, and its second end ground connection, the second end of the second electric capacity 306 is for exporting ON time timing voltage V _ton.

Furthermore, during switching tube 112 conducting, first switch S 1 is controlled as conducting, second switch S2 is controlled as shutoff, 3rd interrupteur SW 3 is controlled as shutoff, the output current I1 of the first current source 301 charges to the first electric capacity 305, and the voltage at the first electric capacity 305 two ends is directly proportional to the ON time of switching tube 112, directly can react ON time; When switching tube 112 turns off, first switch S 1 is controlled as shutoff, second switch S2 is controlled as shutoff, 3rd switch S 3 is controlled as conducting, the voltage at the first electric capacity 305 two ends is maintained, the voltage at the first electric capacity 305 two ends is delivered on the second electric capacity 306 through voltage follower 307, the 3rd switch S 3, thus obtains the ON time timing voltage V representing ON time at the two ends of the second electric capacity 306 _ton; After Preset Time, the first switch S 1 turns off, second switch S2 conducting, and the 3rd switch S 3 turns off, and the voltage at the first electric capacity 305 two ends resets, and the voltage at the second electric capacity 306 two ends remains unchanged.Next, wait for next switch periods, again detect ON time.

Still with reference to figure 2, in a nonrestrictive example, the drive end of the direct connecting valve pipe 112 of switch periods testing circuit 127 is to detect drive singal, and switch periods testing circuit 127 to whole switch periods timing, can obtain switch periods time timing voltage V _t, this switch periods time timing voltage V _theight illustrate the length of switch periods.Such as, ON time timing voltage V _tonmagnitude of voltage be directly proportional to ON time.

In another nonrestrictive example, the drive end of the direct connecting valve pipe 112 of switch periods time detection circuit 127 is with the drive singal of sense switch pipe 112, switch periods time detection circuit 127 to the turn-off time timing in switch periods, can obtain turn-off time timing voltage V _toff, this turn-off time timing voltage V _toffheight illustrate the length of turn-off time.Such as, turn-off time timing voltage V _toffcan be directly proportional with the turn-off time.Then, switch periods time detection circuit 127 can by ON time timing voltage V _tonwith turn-off time timing voltage V _toffbe added, thus also can obtain switch periods time timing voltage V _t.

Switch periods time timing voltage V _tthe switch periods time of switching tube 112 in previous switch periods can be represented, or also can represent the mean value of the switch periods time of switching tube 112 in front multiple switch periods.

The realizing circuit of switch periods time detection circuit 127 can be identical with ON time testing circuit 126.Such as, also the circuit structure shown in Fig. 3 can be adopted.

ON time length control circuit 132 is connected with the output of ON time testing circuit 126, the output of switch periods time detection circuit 127, and receives the bucking voltage V at loop compensation electric capacity 114 two ends _cOMP, according to ON time timing voltage V _ton, switch periods time timing voltage V _tand bucking voltage produces cut-off signals, to make ON time and the ON time timing voltage V of switching tube 112 _ton, switch periods time timing voltage V _tbe associated.Such as, ON time length control circuit 132, by the control to the generation moment of cut-off signals, makes the ON time of switching tube 112 along with ON time timing voltage V _tonincrease and reduce, the ON time of switching tube 112 is along with switch periods timing voltage V _tincrease and increase.

Further, start conducting in response to switching tube 112, ON time length control circuit 132 starts timing, and the ON time reaching setting then produces cut-off signals.

As a preferred embodiment, the cut-off signals that ON time length control circuit 132 produces makes the ON time of switching tube 112 meet following relation: keep fixing, wherein V _tonfor the ON time timing voltage that ON time testing circuit 126 exports, V _tfor the switch periods time timing voltage that switch periods time detection circuit 127 exports, T _onfor the ON time of switching tube 112 within the single switch cycle.

ON time timing voltage V _tonbe directly proportional to the mean value of the ON time of previous switch periods or the ON time of front multiple switch periods, switch periods time timing voltage V _tbe directly proportional to the mean value of the switch periods time of the switch periods time in previous switch periods or front multiple switch periods.In practice, the several switch periods in front and back is normally substantially the same, when achieving keep fixing, be also just equivalent to achieve keep fixing, namely achieve the requirement of aforementioned formula (2), namely switching tube 112 ON time square keep fixing with the ratio of switch periods, thus can power factor be improved.

Constant current counting circuit 120 is sampled to the primary current flowing through switching tube 112, obtains former limit peak current, and the transformer degaussing time T exported by this former limit peak current and zero cross detection circuit 125 _demagcalculate output current; The output current that error amplifier 121 pairs of constant current counting circuits 120 export carries out error amplification, output error voltage with the reference current preset, and this error voltage is applied on loop compensation electric capacity 114.When loop stability, this error voltage is the bucking voltage V on loop compensation electric capacity 114 _cOMP.

The set input of rest-set flip-flop 123 receives zero cross signal ZCD, and the RESET input receives the cut-off signals exported from ON time length control circuit 132, and its output produces drive singal GD with the turn-on and turn-off of control switch pipe 112.As a nonrestrictive example, this drive singal GD is via the drive end transferring to switching tube 112 after driver 124.

ON time length control circuit 132 can realize timing by electric current to the discharge and recharge of electric capacity usually.Show a kind of realizing circuit of logical time span control circuit with reference to figure 4, Fig. 4, comprising: the second current source 401; 3rd electric capacity C1, its first end connects the output of the second current source 401, its second end ground connection; 4th switch S 4, its first end connects the first end of the 3rd electric capacity C1, and its second end connects second end of the 3rd electric capacity C1; Comparator 402, its first input end connects the first end of the 3rd electric capacity C1, and its second input receives the reference voltage Vref 1 preset, and its output is for exporting cut-off signals.

Suppose that the charging current that the second current source 401 exports is I ₁, the capacitance of the 3rd electric capacity C1 is C ₁, the magnitude of voltage of reference voltage Vref 1 is V _ref1, then

$T_{\mathrm{on}}=\frac{V_{\mathrm{ref}1}\·C_1}{I_1}---\left(3\right)$

Wherein T _onfor ON time.For T _onfixing circuit, setting compensation voltage V _cOMPfor V _ref1, charging current I ₁for constant, then due to bucking voltage V _cOMPbe a definite value determined after loop stability, therefore can realize the effect that ON time is fixing.

As previously mentioned, in order to realize constant in improve power factor, need constant, and detecting V _ton, V _twhen, constant be easily realize.

If setting compensation voltage V _cOMPconstant is V _ref1, charging current I ₁can be expressed as wherein I ₀for constant, then have

$T_{\mathrm{on}}=\frac{V_{\mathrm{comp}}\·C_1}{I_1}=\frac{V_{\mathrm{comp}}\·C_1}{I_0\·\frac{V_{\mathrm{Ton}}}{V_T}}$

Namely $T_{\mathrm{on}}\·\frac{V_{\mathrm{Ton}}}{V_T}=\frac{V_{\mathrm{comp}}\·C_1}{I_0}$ For constant, also namely ensure that constant.

For the fixing ON time control circuit such as described in background technology, as long as ensure fixing, just can realize input current well and follow input voltage, thus effectively improve the power factor of circuit, reduce total harmonic distortion.It will be appreciated by those skilled in the art that except the scheme that above embodiment provides, other suitable schemes can also be adopted to ensure fixing, make ON time with ON time timing voltage V _tonincrease and reduce, with switch periods time timing voltage V _tincrease and increase.

Second embodiment

With reference to figure 5, in the second embodiment shown in Fig. 5, the switch power controller 200 in Fig. 2 is applied in the Switching Power Supply of buck topology.The peripheral circuit of this buck Switching Power Supply can be any suitable circuit structure.As a nonrestrictive example, the peripheral circuit of the buck Switching Power Supply shown in Fig. 5 comprises: exchange input source 102, rectifier bridge 101, input capacitance Cin, supplying resistance 104, power supply electric capacity 105, diode 106, transformer T2 (comprising former limit winding L 4 and auxiliary winding L 5), switching tube 112, sampling resistor Rs, feedback resistance 113, loop compensation electric capacity 114, output diode D1, output capacitance Cbulk.Except the topological structure difference of peripheral circuit, the second embodiment shown in Fig. 5 is all identical with Fig. 2.

It will be appreciated by those skilled in the art that what adopt in the embodiment shown in Fig. 2 and Fig. 5 is current constant control loop, the output current of what it controlled is output, wherein loop compensation electric capacity 114 is for loop compensation.If adopt Isobarically Control loop, controlled quentity controlled variable is changed to output voltage Vout, then loop compensation electric capacity 114 is for the stability of bucking voltage loop, bucking voltage V _cOMPthen that error amplifies voltage.Specifically, the constant current counting circuit 120 in Fig. 2, Fig. 5 is replaced by voltage sampling circuit, the output end vo ut voltage of Switching Power Supply is sampled, obtains sampled voltage; And the sampled voltage that error amplifier 121 changes into voltage sampling circuit exports carries out error amplification, output error voltage with default reference voltage, this error voltage is applied on loop compensation electric capacity 114; Other circuit structures are constant, can realize power factor adjustment, realize output voltage constant simultaneously.

The invention discloses and there is power factor adjustment function, the switch power controller that critical conduction mode controls, and describe the specific embodiment of the present invention and effect with reference to the accompanying drawings.It is to be understood that above-described embodiment is just to explanation of the present invention; instead of limitation of the present invention; any innovation and creation do not exceeded in spirit of the present invention; comprise zero cross detection circuit, ON time length control circuit, flip-flop circuit etc.; the replacement of the change to the local structure of circuit, the type to components and parts or model; and the replacement of other unsubstantialities or amendment, all fall within scope.

Claims (29)

1. a switch power controller, is characterized in that, comprising:

Zero cross detection circuit, carries out zero passage detection to the feedback signal of input and produces zero cross signal;

ON time testing circuit, detects the ON time of the switching tube in Switching Power Supply, to obtain ON time timing voltage;

Switch periods time detection circuit, detected the switch periods time of described switching tube, to obtain switch periods time timing voltage;

ON time length control circuit, be connected with the output of described ON time testing circuit, the output of switch periods time detection circuit, and receive bucking voltage, produce cut-off signals according to described ON time timing voltage, switch periods time timing voltage and bucking voltage, be associated with described ON time timing voltage, switch periods time timing voltage to make the ON time of described switching tube;

Drive signal generation circuit, produce drive singal according to described zero cross signal and cut-off signals, described drive singal transfers to the drive end of described switching tube, and in response to described zero cross signal, described drive singal controls described switching tube conducting; In response to described cut-off signals, described drive singal controls described switching tube and turns off.

2. switch power controller according to claim 1, it is characterized in that, the magnitude of voltage of described ON time timing voltage is proportional to the ON time of described switching tube, described switch periods time timing voltage is proportional to the switch periods time of described switching tube, the cut-off signals that described ON time length control module produces makes described ON time reduce with the increase of described ON time timing voltage, and increases with the increase of described switch periods time timing voltage.

3. switch power controller according to claim 1, is characterized in that, the cut-off signals that described ON time length control module produces makes the ON time Ton of described switching tube meet following relation: V _ton× Ton/V _tkeep fixing, wherein, V _tonfor described ON time timing voltage, V _tfor described switch periods time timing voltage.

4. switch power controller according to claim 1, it is characterized in that, the ON time timing voltage that described ON time testing circuit obtains represents the ON time of described switching tube in previous switch periods, or represents the mean value of the ON time of described switching tube in front multiple switch periods.

5. switch power controller according to claim 1, it is characterized in that, the switch periods time timing voltage that described switch periods time detection circuit obtains represents the switch periods time of described switching tube in previous switch periods, or represents the mean value of the switch periods time of described switching tube in front multiple switch periods.

6. switch power controller according to claim 1, is characterized in that, the input of described ON time testing circuit is directly connected with the drive end of described switching tube, to detect the ON time of described switching tube.

7. switch power controller according to claim 1, is characterized in that, the input of described switch periods time detection circuit is directly connected with the drive end of described switching tube, to detect the switch periods time of described switching tube.

8. switch power controller according to any one of claim 1 to 7, is characterized in that, also comprises:

Constant current counting circuit, samples to the primary current of the switching tube flowing through described Switching Power Supply, obtains former limit peak current, and the transformer degaussing Time Calculation output current exported by described former limit peak current and described zero cross detection circuit;

Error amplifier, carry out error amplification, output error voltage to the output current that described constant current counting circuit exports with the reference current preset, described error voltage is applied on loop compensation electric capacity to obtain described bucking voltage.

9. switch power controller according to any one of claim 1 to 7, is characterized in that, also comprises:

Voltage sampling circuit, samples to the voltage of the output of described Switching Power Supply, obtains exporting sampled voltage;

Error amplifier, carry out error amplification, output error voltage to the sampled voltage that described voltage sampling circuit exports with the reference voltage preset, described error voltage is applied on loop compensation electric capacity to obtain described bucking voltage.

10. switch power controller according to any one of claim 1 to 7, it is characterized in that, described drive signal generation circuit comprises: rest-set flip-flop, and its set input receives described zero cross signal, its the RESET input receives described cut-off signals, and its output produces described drive singal.

11. switch power controllers according to claim 10, it is characterized in that, described drive signal generation circuit also comprises: driver, described drive singal transfers to the drive end of described switching tube via described driver.

12. switch power controllers according to any one of claim 1 to 7, is characterized in that, described ON time testing circuit comprises:

First current source;

First switch, its first end connects the output of described first current source;

Second switch, its first end connects the second end of described first switch, its second end ground connection;

First electric capacity, its first end connects the second end of described first switch and the first end of described second switch, its second end ground connection;

Voltage follower, its input connects the first end of described first electric capacity;

3rd switch, its first end connects the output of described voltage follower;

Second electric capacity, its first end connects the second end of described 3rd switch, and its second end ground connection, the second end of described second electric capacity exports described ON time timing voltage.

13. switch power controllers according to claim 12, it is characterized in that, in response to described switching tube conducting, described first switch conduction, described second switch and the 3rd switch OFF, described first current source, to described first capacitor charging, makes the voltage at described first electric capacity two ends be directly proportional to the ON time of described switching tube; Turn off in response to described switching tube, described first switch and second switch turn off, described 3rd switch conduction, and the voltage at described first electric capacity two ends is maintained and is passed to described second electric capacity via described voltage follower and the 3rd switch; After turning off Preset Time in response to described switching tube, described first switch and the 3rd switch OFF, described second switch conducting, the voltage at described first electric capacity two ends resets, and the voltage on described second electric capacity remains unchanged.

14. switch power controllers according to any one of claim 1 to 7, is characterized in that, described ON time length control circuit comprises:

Second current source;

3rd electric capacity, its first end connects the output of described second current source, its second end ground connection;

4th switch, its first end connects the first end of described 3rd electric capacity, and its second end connects the second end of described 3rd electric capacity;

Comparator, its first input end connects the first end of described 3rd electric capacity, and its second input receives the reference voltage preset, and its output is for exporting described cut-off signals.

15. 1 kinds of Switching Power Supplies, is characterized in that, comprise switch power controller and coupled peripheral circuit, and wherein, described switch power controller comprises:

Zero cross detection circuit, carries out zero passage detection to the feedback signal of input and produces zero cross signal;

ON time testing circuit, detects the ON time of the switching tube in Switching Power Supply, to obtain ON time timing voltage;

Switch periods time detection circuit, detected the switch periods time of described switching tube, to obtain switch periods time timing voltage;

ON time length control circuit, be connected with the output of described ON time testing circuit, the output of switch periods time detection circuit, and receive bucking voltage, cut-off signals is produced according to described ON time timing voltage, switch periods time timing voltage and bucking voltage, be associated with described ON time timing voltage, switch periods time timing voltage to make the ON time of described switching tube

Drive signal generation circuit, produce drive singal according to described zero cross signal and cut-off signals, described drive singal transfers to the drive end of described switching tube, and in response to described zero cross signal, described drive singal controls described switching tube conducting; In response to described cut-off signals, described drive singal controls described switching tube and turns off.

16. Switching Power Supplies according to claim 15, it is characterized in that, the magnitude of voltage of described ON time timing voltage is proportional to the ON time of described switching tube, described switch periods time timing voltage is proportional to the switch periods time of described switching tube, increase in response to described ON time timing voltage, the cut-off signals that described ON time length control module produces makes described ON time reduce, increase in response to described switch periods time timing voltage, the cut-off signals that described ON time length control module produces makes described ON time increase.

17. Switching Power Supplies according to claim 15, is characterized in that, the cut-off signals that described ON time length control module produces makes the ON time Ton of described switching tube meet following relation: V _ton× Ton/V _tkeep fixing, wherein, V _tonfor described ON time timing voltage, V _tfor described switch periods time timing voltage.

18. Switching Power Supplies according to claim 15, it is characterized in that, the ON time timing voltage that described ON time testing circuit obtains represents the ON time of described switching tube in previous switch periods, or represents the mean value of the ON time of described switching tube in front multiple switch periods.

19. Switching Power Supplies according to claim 15, it is characterized in that, the switch periods time timing voltage that described switch periods time detection circuit obtains represents the switch periods time of described switching tube in previous switch periods, or represents the mean value of the switch periods time of described switching tube in front multiple switch periods.

20. Switching Power Supplies according to claim 15, is characterized in that, the input of described ON time testing circuit is directly connected with the drive end of described switching tube, to detect the ON time of described switching tube.

21. Switching Power Supplies according to claim 15, is characterized in that, the input of described switch periods time detection circuit is directly connected with the drive end of described switching tube, to detect the switch periods time of described switching tube.

22., according to claim 15 to the Switching Power Supply according to any one of 21, is characterized in that, described switch power controller also comprises:

Constant current counting circuit, samples to the primary current of the switching tube flowing through described Switching Power Supply, obtains former limit peak current, and the transformer degaussing Time Calculation output current exported by described former limit peak current and described zero cross detection circuit;

Error amplifier, carry out error amplification, output error voltage to the output current that described constant current counting circuit exports with the reference current preset, described error voltage is applied on loop compensation electric capacity to obtain described bucking voltage.

23., according to claim 15 to the Switching Power Supply according to any one of 21, is characterized in that, described switch power controller also comprises:

Voltage sampling circuit, samples to the voltage of the output of described Switching Power Supply, obtains exporting sampled voltage;

Error amplifier, carry out error amplification, output error voltage to the sampled voltage that described voltage sampling circuit exports with the reference voltage preset, described error voltage is applied on loop compensation electric capacity to obtain described bucking voltage.

24. according to claim 15 to the Switching Power Supply according to any one of 21, it is characterized in that, described drive signal generation circuit comprises: rest-set flip-flop, and its set input receives described zero cross signal, its the RESET input receives described cut-off signals, and its output produces described drive singal.

25. Switching Power Supplies according to claim 24, it is characterized in that, described drive signal generation circuit also comprises: driver, described drive singal transfers to the drive end of described switching tube via described driver.

26., according to claim 15 to the Switching Power Supply according to any one of 21, is characterized in that, described ON time testing circuit comprises:

First current source;

First switch, its first end connects the output of described first current source;

Second switch, its first end connects the second end of described first switch, its second end ground connection;

First electric capacity, its first end connects the second end of described first switch and the first end of described second switch, its second end ground connection;

Voltage follower, its input connects the first end of described first electric capacity;

3rd switch, its first end connects the output of described voltage follower;

Second electric capacity, its first end connects the second end of described 3rd switch, and its second end ground connection, the second end of described second electric capacity exports described ON time timing voltage.

27. Switching Power Supplies according to claim 26, it is characterized in that, in response to described switching tube conducting, described first switch conduction, described second switch and the 3rd switch OFF, described first current source, to described first capacitor charging, makes the voltage at described first electric capacity two ends be directly proportional to the ON time of described switching tube; Turn off in response to described switching tube, described first switch and second switch turn off, described 3rd switch conduction, and the voltage at described first electric capacity two ends is maintained and is passed to described second electric capacity via described voltage follower and the 3rd switch; After turning off Preset Time in response to described switching tube, described first switch and the 3rd switch OFF, described second switch conducting, the voltage at described first electric capacity two ends resets, and the voltage on described second electric capacity remains unchanged.

28., according to claim 15 to the Switching Power Supply according to any one of 21, is characterized in that, described ON time length control circuit comprises:

Second current source;

3rd electric capacity, its first end connects the output of described second current source, its second end ground connection;

4th switch, its first end connects the first end of described 3rd electric capacity, and its second end connects the second end of described 3rd electric capacity;

Comparator, its first input end connects the first end of described 3rd electric capacity, and its second input receives the reference voltage preset, and its output is for exporting described cut-off signals.

29. Switching Power Supplies according to claim 15, is characterized in that, described peripheral circuit is reverse exciting topological or buck topology.