CN103001463A - Switching power supply controller and switching power supply containing same - Google Patents

Abstract

The invention provides a switching power supply controller and a switching power supply containing the same. The switching power supply controller comprises a zero-cross detection circuit for performing zero-cross detection on input feedback signals and generating zero-cross signals, an input voltage detection circuit for detecting input voltage, an output voltage detection circuit for detecting input voltage, a connection time length control module and a radio station (RS) trigger. The connection time length control module generates turn-off signals according to the input voltage, the output voltage and offset voltage so as to enable connection time of a switching tube to be relevant to the input voltage and the output voltage, and the connection time is prolonged when the input voltage rises and shortened when the output voltage rises. The setting input end of the RS trigger receives the zero-cross signals, the resetting input end of the RS trigger receives the turn-off signals, and the output end of the RS trigger generates driving signals to control connection and disconnection of the switching tube of the switching power supply. The switching power supply controller and the switching power supply containing the switching power supply controller can optimize power factors of the switching power supply controlled by a critical connection mode and reduce 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, relate in particular to a kind of switch power controller with power factor adjustment function, critical conduction mode control, and the Switching Power Supply that comprises this switch power controller.

Background technology

Isolation LED constant-current drive circuit traditional Alternating Current Power Supply, that be with power factor adjustment (PFC) function, critical conduction mode 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 used for receiving the feedback signal FB from the auxiliary group of winding L 3 of 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 are passed to output to the input energy by isolating transformer T1.

Constant-current switch power source controller 100 comprises: zero cross detection circuit 125, for detection of the feedback signal FB zero passage that drives after signal GD finishes, when feedback signal FB zero passage, provide the signal of opening of power switch 112, conducting power switch 112, zero cross detection circuit 125 also obtains the degaussing time T demag of transformer T1, and transmits it to constant-current control circuit 120; Constant current counting circuit 120, by being sampled, the voltage on the sampling resistor Rs obtains former limit peak current, obtained the degaussing time T demag of transformer T1 by zero cross detection circuit 125, this degaussing time T demag is exactly the current lead-through time of output rectifier diode D1, is calculated the size of output current by former limit peak current, transformer degaussing time T demag; Error amplifier 121, the output current that constant current counting circuit 120 calculates and reference current are done error and are amplified, output error voltage COMP, and error voltage COMP connects building-out capacitor 114, so that after the loop stability, error voltage COMP is substantially fixing; ON time length control circuit 122, the ON time length of power ratio control switch 112, when power switch 112 beginning conducting, begin regularly, when reaching the ON time of setting, the output cut-off signals removes switch-off power switch 112 to trigger 123, after loop stability, error voltage COMP is fixedly the time, and the ON time consistent length of power switch 112 realizes the power factor adjustment thus; Trigger 123 receives the zero cross signal ZCD of zero cross detection circuit 125 outputs and the cut-off signals of ON time length control circuit 122 outputs; Drive circuit 124, the drive end of connection trigger 123 and power switch 112 is realized the driving that turns on and off to power switch 112.

For realizing that preferably power factor adjusts effect, require the AC input current of each switch periods can both well follow the variation of input voltage.Under critical conduction mode, the pressure drop when ignoring the pressure drop of output rectifier diode, 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 secondary winding L 2, V _OutBe output voltage, V _InBe input voltage, I _InBe input current, T _OnBe ON time, L is the inductance of former limit winding L 1.Adopt fixedly ON time (T _OnConstant), critical conduction mode when control, input current I _InCan not follow input voltage V fully _InChange, the power factor variation, total harmonic distortion strengthens, and input voltage V _InHigher, deviation is larger, so the power factor of at present traditional circuit is not good especially, total harmonic distortion is also larger.

Summary of the invention

The technical problem to be solved in the present invention provides a kind of switch power controller and comprises the Switching Power Supply of this switch power controller, optimizes the power factor of the Switching Power Supply of critical conduction mode control, reduces total harmonic distortion.

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

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

Input voltage detection circuit detects the input voltage of Switching Power Supply;

Output voltage detecting circuit detects the output voltage of described Switching Power Supply;

ON time length control module, link to each other with the output of described input voltage detection circuit, the output of output voltage detecting circuit, and the bucking voltage on the reception loop compensation electric capacity, input voltage, output voltage and bucking voltage according to described Switching Power Supply produce cut-off signals, so that the ON time of the switching tube of described Switching Power Supply is associated with input voltage, the output voltage of described Switching Power Supply, described ON time increases when described input voltage raises and reduces when described output voltage raises;

Rest-set flip-flop, its set input receives described zero cross signal, and its RESET input receives described cut-off signals, and its output produces and drives signal with the turn-on and turn-off of the switching tube of controlling described Switching Power Supply.

According to one embodiment of present invention, the cut-off signals of described ON time length control module generation makes the ON time of the switching tube of described Switching Power Supply satisfy following relation:

Keep fixing, wherein, n is the former limit winding of transformer of described Switching Power Supply and the turn ratio of secondary winding, V _OutBe the output voltage of described Switching Power Supply, V _InBe the input voltage of described Switching Power Supply, T _OnON time for the switching tube of described Switching Power Supply.

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

ON time length control circuit, connect the output of described input voltage detection circuit, the output of output voltage detecting circuit, and receive bucking voltage on the described loop compensation electric capacity, switching tube by described Switching Power Supply begins conducting triggering beginning regularly, the ON time that reaches setting then produces described cut-off signals, the ON time of described setting is associated with described bucking voltage, input voltage and output voltage, increases when described input voltage raises and reduces when described output voltage raises.

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

Multiplier, connect the output of described input voltage detection circuit, the output of output voltage detecting circuit, and receiving bucking voltage on the described loop compensation electric capacity, the output signal of described multiplier is the quadratic function of described input voltage and reduces with the rising of described output voltage;

The peak current comparator, the first end that connects the sampling resistor of the output of described multiplier and described Switching Power Supply, the first end of described sampling resistor connects the output of described switching tube, the second end ground connection of described sampling resistor, after the described switching tube conducting, the voltage at described sampling resistor two ends raises, and the voltage at described sampling resistor two ends produces described cut-off signals when surpassing the output signal of described multiplier.

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

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

Error amplifier carries out the error amplification to the output current of described constant current counting circuit output and default reference current, and output error voltage, described error voltage are applied on the described loop compensation electric capacity.

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

Voltage sampling circuit is sampled to the voltage of the switching tube output of described Switching Power Supply, obtains peak value sampling voltage;

Error amplifier carries out the error amplification to the peak value sampling voltage of described voltage sampling circuit output and default reference voltage, and output error voltage, described error voltage are applied on the described loop compensation electric capacity.

According to one embodiment of present invention, the input of described input voltage detection circuit links to each other with the pin of described input voltage, directly described input voltage is sampled.

According to one embodiment of present invention, the input of described input voltage detection circuit links to each other with described auxiliary winding, the negative pressure during for detection of the switching tube conducting of described Switching Power Supply on the described auxiliary winding, and this negative pressure is relevant with described input voltage.

According to one embodiment of present invention, the input of described output voltage detecting circuit links to each other with described auxiliary winding, for detection of the positive voltage on the described auxiliary winding after the switching tube shutoff Preset Time section of described Switching Power Supply, this positive voltage is relevant with described output voltage.

The present invention also provides a kind of reverse exciting topological Switching Power Supply, comprises above each described switch power controller.

The present invention also provides a kind of buck Switching Power Supply, comprises above each described switch power controller.

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

The switch power controller of the embodiment of the invention is by revising the switch conduction time of switching tube, and input voltage, the output voltage of itself and Switching Power Supply are associated, thereby improved the power factor of circuit, reduced the total harmonic distortion of Switching Power Supply.

Furthermore, the ON time of switching tube satisfies

Keep fixing, change so that input current is followed input voltage fully, realize good power factor performance.

Description of drawings

Fig. 1 is a kind of electrical block diagram that power factor is adjusted function, adopted the LED constant-flow driver that fixedly ON time is controlled, critical conduction mode is controlled that has of the prior art;

Fig. 2 is the electrical block diagram that power factor is adjusted function, adopted the reverse exciting topological LED constant-flow driver that ON time is controlled, critical conduction mode is controlled that has of the embodiment of the invention;

Fig. 3 is that the power factor that has of the embodiment of the invention is adjusted function, optimizes multiplier and adopted the electrical block diagram of the reverse exciting topological LED constant-current controller of peak current control, critical conduction mode control;

Fig. 4 is that the power factor that has of the embodiment of the invention is adjusted function, optimizes multiplier and adopted the electrical block diagram of the buck topology LED constant-current controller of peak current control, critical conduction mode control.

Embodiment

According to the formula in the background technology (1) as can be known, fixedly ON time is controlled and is caused because input current can not follow fully that input voltage change to be, so for the optimizing power factor, optimize total harmonic distortion, can revise ON time length, fixing ON time length is revised as and input voltage, ON time length that output voltage is relevant.

Further, according to formula (1), in order to realize preferably power factor, need input current to follow input voltage fully and change, therefore need to guarantee

Fixing, thus power factor improved, and namely the ON time of switching tube and input voltage, output voltage are relevant.

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

With reference to figure 2, Fig. 2 shows the electrical block diagram of the reverse exciting topological Switching Power Supply of the first embodiment, and this reverse exciting topological Switching Power Supply can be used as led driver.As described in Figure 2, this Switching Power Supply comprises: AC signal source 102, rectifier bridge 101, input capacitance Cin, resistance 104, electric capacity 105, diode 106, transformer T1(comprise former limit winding L 1, secondary winding L 2, auxiliary winding L 3), switching tube 112, sampling resistor Rs, 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, for example identical with the Integral connection structure of Fig. 1 in the background technology with conventional inverse-excitation type switch power-supply.

In the present embodiment, switch power controller 200 comprises: be specially ON time length control circuit 132 in zero cross detection circuit 125, input voltage detection circuit 126, output voltage detecting circuit 127, constant current counting circuit 120, error amplifier 121, the ON time length control module 132(present embodiment), rest-set flip-flop 123, driver 124.

Wherein, the feedback signal FB of 125 pairs of inputs of zero cross detection circuit 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 resistance 113.Zero cross detection circuit 125 also detects the degaussing time T demag of transformer T1, and transmits it to constant current counting circuit 120.

The input voltage vin of 126 pairs of Switching Power Supplies of input voltage detection circuit detects, and testing result is transferred to ON time length control circuit 132.

In an instantiation, the input of input voltage detection circuit 126 can link to each other with the pin of input voltage vin, directly input voltage vin is sampled to obtain testing result.

In another instantiation, the input of input voltage detection circuit 126 also can link to each other with auxiliary winding L 3, and the negative pressure during by 112 conducting of sense switch pipe on the auxiliary winding L 3 obtains testing result, and this negative pressure is relevant with input voltage vin.

The output voltage V out of 127 pairs of Switching Power Supplies of output voltage detecting circuit detects, and testing result is transferred to ON time length control circuit 132.

In one example, the input of output voltage detecting circuit 127 can link to each other with auxiliary winding L 3, after switching tube 112 turn-offs the Preset Time section, obtains testing result by the positive voltage that detects on the auxiliary winding L 3, and this positive voltage is relevant with output voltage V out.

ON time length control module 132 links to each other with the output of input voltage detection circuit 126, the output of output voltage detecting circuit 127, and the bucking voltage COMP on the reception loop compensation electric capacity 114, input voltage vin, output voltage V out and bucking voltage COMP according to Switching Power Supply produce cut-off signals, so that the ON time of switching tube 112 increases when input voltage vin raises and reduces when output voltage V out raises.

More specifically, in the embodiment shown in Figure 2, ON time length control module 132 is specially ON time length control circuit 132, it connects the output of input voltage detection circuit 126, the output of output voltage detecting circuit 127, and the bucking voltage COMP on the reception loop compensation electric capacity 114, triggered and the beginning timing by switching tube 112 beginning conductings, the ON time that reaches setting then produces cut-off signals, the ON time of this setting and bucking voltage COMP, input voltage vin and output voltage V out are associated, and increase when input voltage vin raises and reduce when output voltage V out raises.

As a preferred embodiment, the cut-off signals that ON time length control circuit 132 produces is so that the ON time of switching tube 112 satisfies following relation:

Keep fixing, wherein, n is the former limit winding L 1 of transformer T1 of Switching Power Supply and the turn ratio of secondary winding L 2, V _OutBe the output voltage of Switching Power Supply, V _InBe the input voltage of Switching Power Supply, T _OnON time for switching tube 112.

The flow through primary current of switching tube 112 of 120 pairs of constant current counting circuits is sampled, and obtains former limit peak current, and calculates output current by the transformer degaussing time T demag of this former limit peak current and zero cross detection circuit 125 outputs; The output current of 121 pairs of constant current counting circuits of error amplifier, 120 outputs carries out error with default reference current and amplifies, output error voltage, this error voltage is applied on the described loop compensation electric capacity, when loop stability, this error voltage is the bucking voltage COMP on the loop compensation electric capacity 114.

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

Furthermore, for ON time length control circuit 132, ON time length control circuit 132 is realized regularly discharging and recharging of electric capacity by electric current usually, supposes that charging current regularly is I ₁, electric capacity is C ₁, comparison point voltage is V _Ref1, then

$T_{\mathrm{on}}=\frac{V_{\mathrm{ref}1}\·C_1}{I_1}---\left(2\right)$

T wherein _OnBe ON time.For fixing T _OnCircuit, setting compensation voltage COMP is V _Ref1, charging current I regularly ₁Be constant, because bucking voltage COMP is a definite value, therefore can realize the effect that ON time is fixing after loop stability.

As previously mentioned, in order to realize

Constant in to improve power factor, need

Constant, detecting input voltage V _In, the turn ratio is taken advantage of output voltage nV _OutAfter, realize easily $\frac{n\·V_{\mathrm{out}}}{V_{\mathrm{in}}+n\·V_{\mathrm{out}}}\·\frac{V_{\mathrm{ref}1}\·C_1}{I_1}$ Constant.

If setting compensation voltage COMP is V _Ref1, then control charging current I regularly ₁Can be expressed as

I wherein ₀Be constant, then have

$\frac{n\·V_{\mathrm{out}}}{V_{\mathrm{in}}+n\·V_{\mathrm{out}}}\·T_{\mathrm{on}}=\frac{V_{\mathrm{ref}1}\·C_1}{I_0}---\left(3\right)$

Be constant.

As input voltage V _InWhen very low, charging current I regularly ₁Be I ₀, as input voltage V _InWhen very high, charging current I regularly ₁Reduce.Work as output voltage V _OutWhen low, charging current I regularly ₁Less, output voltage V _OutDuring rising, charging current I regularly ₁Raise.

If setting compensation voltage COMP becomes I in the formula (2) through voltage current transducer ₁, can know, after the loop stability, I ₁Be a stable quantity, then need to control V _Ref1With input voltage V _In, output voltage V _OutRelevant, namely arrange V wherein _Ref0It is the constant that inside circuit is set.By on can know by inference and have:

$\frac{n\&CenterDot;V_{\mathrm{out}}}{V_{\mathrm{in}}+n\&CenterDot;V_{\mathrm{out}}}\&CenterDot;T_{\mathrm{on}}=\frac{{\mathrm{<figure-callout\; id="0"\; label="V\; ref"\; filenames="HDA00002651054500012.png,HDA00002651054500022.png"\; state="\{\{state\}\}">V</figure-callout>}}_{\mathrm{ref}}\&CenterDot;C_1}{I_1}---\left(4\right)$

Be constant.

When input voltage is very low, comparison point voltage V _Ref1Be V _Ref0, as input voltage V _InDuring rising, comparison point voltage V _Ref1Raise; Work as output voltage V _OutWhen low, comparison point voltage V _Ref1Larger; Output voltage V _OutDuring rising, comparison point voltage V _Ref1Reduce.

More than the final purpose of implementation method of two kinds of ON time length control circuits identical, realize that namely ON time length increases when input voltage raises, ON time length reduces when output voltage raises.

Guarantee

Fixing, can realize well that input current follows input voltage.When adopting approximate method, realize the function that ON time length increases when input voltage raises, the function that ON time length reduces when output voltage raises is with respect to fixing ON time control circuit, power factor that can both the Effective Raise circuit reduces total harmonic distortion.

Fig. 3 shows the circuit structure of the reverse exciting topological Switching Power Supply of another embodiment of the present invention, and its overall structure is identical with embodiment shown in Figure 2, and difference is that switch power controller 300 and switch power controller 200 shown in Figure 2 have difference.

Particularly, in the embodiment shown in fig. 3, switch power controller 300 comprises: zero cross detection circuit 125, input voltage detection circuit 126, output voltage detecting circuit 127, constant current counting circuit 120, error amplifier 121, ON time length control module, rest-set flip-flop 123, driver 124.

Different from last embodiment is, what ON time length control module adopted in the present embodiment is to optimize multiplier in conjunction with the mode of peak current control, wherein the input of multiplier not only contains input voltage signal, also contains output voltage signal, and the output variable of multiplier also is different.

Particularly, ON time length control module comprises multiplier 148 and peak current comparator 149.Wherein, multiplier 148 connects the output of input voltage detection circuit 126, the output of output voltage detecting circuit 127, and receive bucking voltage COMP on the loop compensation electric capacity 114, the output signal of multiplier 148 be Switching Power Supply input voltage vin quadratic function and reduce with the rising of output voltage V out.The first end of the output of peak current comparator 149 connection multipliers 148 and the sampling resistor Rs of Switching Power Supply, the output of the first end connecting valve pipe 112 of sampling resistor Rs, the second end ground connection of sampling resistor Rs.The output signal of 149 pairs of multipliers 148 of peak current comparator and the voltage on the sampling resistor Rs compare, after switching tube 112 conductings, the voltage at sampling resistor Rs two ends raises, and the voltage at sampling resistor Rs two ends produces cut-off signals when surpassing the output signal of multiplier 148.

At this moment, the expression formula of input current changes into:

$I_{\mathrm{in}}=\frac{1}{2}\&CenterDot;\frac{n\&CenterDot;V_{\mathrm{out}}}{V_{\mathrm{in}}+n\&CenterDot;V_{\mathrm{out}}}\&CenterDot;I_{\mathrm{pk}}---\left(5\right)$

I wherein _PkBe former limit peak current, the implication of other parameters is consistent with aforementioned content.Accomplish that input current and input voltage follow fully, namely require:

$\frac{n\&CenterDot;V_{\mathrm{out}}}{V_{\mathrm{in}}+n{\&CenterDot;V}_{\mathrm{out}}}\&CenterDot;I_{\mathrm{pk}}=K_1\&CenterDot;V_{\mathrm{in}};$

Wherein K1 is constant.

Obtain after the arrangement: $I_{\mathrm{pk}}=K_1\&CenterDot;V_{\mathrm{in}}\&CenterDot;\frac{V_{\mathrm{in}}+n\&CenterDot;V_{\mathrm{out}}}{n\&CenterDot;V_{\mathrm{out}}}=\frac{K_1\&CenterDot;V_{\mathrm{in}}^2}{n\&CenterDot;V_{\mathrm{out}}}+K_1\&CenterDot;V_{\mathrm{in}}.$

The output that is multiplier 148 forms by two parts are cumulative, and a part is directly proportional with input voltage vin, square being directly proportional of another part and input voltage vin, and out is inversely proportional to output voltage V.Perhaps in other words, the output of multiplier 148 is quadratic functions of input voltage vin.The output of multiplier 148 is also relevant with output voltage V out, and with the rising of output voltage V out, the output of multiplier 148 reduces.And in the prior art in the traditional multiplier architecture, only comprised the part that is directly proportional with input voltage value.

With reference to figure 4, Fig. 4 shows the circuit structure of the Switching Power Supply among the another embodiment.In the embodiment shown in fig. 4, the switch power controller 300 among Fig. 3 is applied in the Switching Power Supply of buck structure, the peripheral circuit structure of this buck Switching Power Supply can be any suitable circuit structure.As a nonrestrictive example, the peripheral circuit of buck Switching Power Supply shown in Figure 4 comprises: exchange input source 102, rectifier bridge 101, input capacitance Cin, resistance 104, electric capacity 105, diode 106, transformer T2(and comprise former limit winding L 4 and auxiliary winding L 5), switching tube 112, sampling resistor Rs, resistance 113, loop compensation electric capacity 114, output diode D1, output capacitance Cbulk.

Preferably, for so that input current is followed input voltage vin fully, should make

Keep fixing (also being turn ratio n=1).

Need to prove that switch power controller 200 shown in Figure 2 also goes for buck Switching Power Supply shown in Figure 4.

It will be appreciated by those skilled in the art that what adopt among Fig. 2, Fig. 3 and the embodiment shown in Figure 4 is the constant current control loop, its control be the LED output current, wherein loop compensation electric capacity 114 is used for loop compensation.If adopt the constant voltage control loop, controlled quentity controlled variable is changed to output voltage V out, then loop compensation electric capacity 114 is used for the stability of bucking voltage loop, and bucking voltage COMP is that error is amplified voltage.Particularly, the constant current counting circuit 120 among Fig. 2, Fig. 3, Fig. 4 is replaced by voltage sampling circuit, the voltage of switching tube 112 outputs is sampled, obtain peak value sampling voltage; And the peak value sampling voltage that error amplifier 121 changes into voltage sampling circuit output carries out the error amplification with the reference voltage of presetting, and output error voltage, this error voltage are applied on the loop compensation electric capacity 114; Other circuit structures are constant, can realize the power factor adjustment, realize that simultaneously output voltage is constant.

In addition, for Fig. 3 and embodiment shown in Figure 4, the input of input voltage detection circuit 126 can link to each other with the pin of input voltage vin, directly input voltage vin is sampled to obtain testing result.Perhaps, the input of input voltage detection circuit 126 also can link to each other with auxiliary winding L 3, and the negative pressure during by 112 conducting of sense switch pipe on the auxiliary winding L 3 obtains testing result, and this negative pressure is relevant with input voltage vin.And the input of output voltage detecting circuit 127 can link to each other with auxiliary winding L 3, after switching tube 112 turn-offs the Preset Time section, obtains testing result by the positive voltage that detects on the auxiliary winding L 3, and this positive voltage is relevant with output voltage V out.

The invention discloses and have power factor and adjust function, the switch power controller of critical conduction mode control, and describe the specific embodiment of the present invention and effect with reference to the accompanying drawings.What should be understood that is that above-described embodiment is just to explanation of the present invention; rather than limitation of the present invention; any innovation and creation that do not exceed in the connotation scope of the present invention; comprise zero cross detection circuit, ON time length control circuit, flip-flop circuit, multiplier; to the change of the local structure of circuit, to the replacement of type or the model of components and parts; and the replacement of other unsubstantialities or modification, all fall within the protection range of the present invention.

Claims (11)

1. the switch power controller of a critical conduction mode control is characterized in that, comprising:

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

Input voltage detection circuit detects the input voltage of Switching Power Supply;

Output voltage detecting circuit detects the output voltage of described Switching Power Supply;

ON time length control module, link to each other with the output of described input voltage detection circuit, the output of output voltage detecting circuit, and the bucking voltage on the reception loop compensation electric capacity, input voltage, output voltage and bucking voltage according to described Switching Power Supply produce cut-off signals, so that the ON time of the switching tube of described Switching Power Supply is associated with input voltage, the output voltage of described Switching Power Supply, described ON time increases when described input voltage raises and reduces when described output voltage raises;

Rest-set flip-flop, its set input receives described zero cross signal, and its RESET input receives described cut-off signals, and its output produces and drives signal with the turn-on and turn-off of the switching tube of controlling described Switching Power Supply.

2. 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 of the switching tube of described Switching Power Supply satisfy following relation: Keep fixing, wherein, n is the former limit winding of transformer of described Switching Power Supply and the turn ratio of secondary winding, V _OutBe the output voltage of described Switching Power Supply, V _InBe the input voltage of described Switching Power Supply, T _OnON time for the switching tube of described Switching Power Supply.

3. switch power controller according to claim 1 is characterized in that, described ON time length control module comprises:

ON time length control circuit, connect the output of described input voltage detection circuit, the output of output voltage detecting circuit, and receive bucking voltage on the described loop compensation electric capacity, switching tube by described Switching Power Supply begins conducting triggering beginning regularly, the ON time that reaches setting then produces described cut-off signals, the ON time of described setting is associated with described bucking voltage, input voltage and output voltage, increases when described input voltage raises and reduces when described output voltage raises.

4. switch power controller according to claim 1 is characterized in that, described ON time length control module comprises:

Multiplier, connect the output of described input voltage detection circuit, the output of output voltage detecting circuit, and receiving bucking voltage on the described loop compensation electric capacity, the output signal of described multiplier is the quadratic function of described input voltage and reduces with the rising of described output voltage;

The peak current comparator, the first end that connects the sampling resistor of the output of described multiplier and described Switching Power Supply, the first end of described sampling resistor connects the output of described switching tube, the second end ground connection of described sampling resistor, after the described switching tube conducting, the voltage at described sampling resistor two ends raises, and the voltage at described sampling resistor two ends produces described cut-off signals when surpassing the output signal of described multiplier.

5. each described switch power controller in 4 according to claim 1 is characterized in that, also comprises:

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

Error amplifier carries out the error amplification to the output current of described constant current counting circuit output and default reference current, and output error voltage, described error voltage are applied on the described loop compensation electric capacity.

6. each described switch power controller in 4 according to claim 1 is characterized in that, also comprises:

Voltage sampling circuit is sampled to the voltage of the switching tube output of described Switching Power Supply, obtains peak value sampling voltage;

Error amplifier carries out the error amplification to the peak value sampling voltage of described voltage sampling circuit output and default reference voltage, and output error voltage, described error voltage are applied on the described loop compensation electric capacity.

7. switch power controller according to claim 1 is characterized in that, the input of described input voltage detection circuit links to each other with the pin of described input voltage, directly described input voltage is sampled.

8. switch power controller according to claim 1, it is characterized in that, the input of described input voltage detection circuit links to each other with described auxiliary winding, the negative pressure during for detection of the switching tube conducting of described Switching Power Supply on the described auxiliary winding, and this negative pressure is relevant with described input voltage.

9. switch power controller according to claim 1, it is characterized in that, the input of described output voltage detecting circuit links to each other with described auxiliary winding, for detection of the positive voltage on the described auxiliary winding after the switching tube shutoff Preset Time section of described Switching Power Supply, this positive voltage is relevant with described output voltage.

10. a reverse exciting topological Switching Power Supply is characterized in that, comprises each described switch power controller in the claim 1 to 9.

11. a buck Switching Power Supply is characterized in that, comprises each described switch power controller in the claim 1 to 9.

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