CN100409136C - Switching controller of primary power supplier with side control - Google Patents

Abstract

The present invention relates to a switching control device of a primary-side control power supplier. The present invention comprises a feedback systemization unit, a waveform generation unit, a power limitation unit, an oscillator and a switching signal generation unit, wherein the feedback systemization unit receives supply voltage of the primary side of a power supplier and outputs a feedback signal; the waveform generation unit receives the supply voltage and a sawtooth wave signal generated by the oscillator and outputs a power limitation value; the power limitation unit receives the power limitation value and a sensing signal of the power suppplier and outputs a power limitation signal. Besides, the switching signal generation unit receives the power limitation signal, the sensing signal, the feedback signal and an oscillation signal generated by the oscillator, outputs a switching signal and controls output voltage, output current and output power of the power supplier.

Description

The switching control device of primary power supplier with side

Technical field:

The invention relates to a kind of switching control device, particularly about a kind of switching control device of primary side control switched power supply, it is output voltage, output power and the output current of primary power supplier with side.

Background technology:

Press, advantage such as switched power supply has high-level efficiency, volume is little and in light weight is so be widely used in many electronic equipments and computer.Typical switched power supply includes a switching control device, a power switch, a transformer and a feedback control circuit usually, feedback control circuit is output voltage and the output current that is used for detecting the secondary side of power supply unit, this feedback control circuit is that the isolated component that sees through as photo-coupler is connected to switching control device, to constitute feedback loop.

Please refer to Fig. 1, be the circuit diagram of known power supply unit; As input power supply V _INWhen beginning to power, see through a starting resistance R of series connection _STBegin to start capacitor C to one _STCharge, up to a supply voltage V _CCReach the trigger voltage of a switching control device 5, and then, one of switching control device 5 switches signal generation unit 54 and begins to export a switching signal V _PWMDrive a power switch Q ₁To switch a transformer T ₁Through behind the start-up routine, supply voltage V _CCBe by transformer T ₁Auxiliary winding N _ASee through a rectifier D _AInstitute provides.

Multiple with reference to figure 1, known power supply unit is by at transformer T ₁Secondary side one photo-coupler O is set ₁, in order to reach transformer T ₁First and second side isolate photo-coupler O ₁Input end be subjected to a resistance R _KWith a Zener diode Z ₁Check and receive driven, make output terminal produce one and feedback signal V _FB, switch signal generation unit 54 and transfer to, to form feedback control circuit.Back coupling signal V _FBSignal V is switched in decision _PWMON time t _ON, promptly determine the output power of power supply unit.In addition, an electric crystal Q ₂In conjunction with a current sensing resistor R ₀, in order to the maximum output current I of decision power supply unit ₀As output current I ₀Increase, and across current sensing resistor R ₀The voltage at two ends surpasses this electric crystal Q ₂The face that connects voltage such as 0.7V, electric crystal Q ₂With conducting, to reduce back coupling signal V _FB, so can reduce and switch signal V _PWMON time t _ON, thereby make the output current I of power supply unit ₀Be restricted to certain value.

Though previous circuit can be used for stablizing the output voltage V of adjusting power supply unit ₀With output current I ₀, but do not removing photo-coupler O ₁Under the situation of secondary side feedback control circuit, it is very difficult reaching the volume that dwindles power-supply controller of electric.Moreover, be used for deciding the current sensing resistor R that electric current is exported ₀Can cause the power attenuation that increases power supply unit.

Multiple with reference to figure 1, in power supply unit, the output power restriction is to be used for overload and short-circuit protection, and power supply unit detects resistance R by one _SWith power switch Q ₁Series connection is with the decision peak power output.The method that realizes is that this is detected resistance R _SA sensing signal V _CSBe transferred to the negative terminal of a Power Limitation comparer 53 of switching control device 5, as this sensing signal V _CSGreater than the accurate position of Power Limitation V _MThe time, this switching signal generation unit 54 will periodically be adjusted and switch signal V _PWMON time t _ON, and also will limit the peak power output of power supply unit.

Switch signal generation unit 54 and include a comparer 542, one and lock 544 and a flip-flop 546, comparer 542 comparison operations back coupling signal V _FBWith sensing signal V _CS, to export a modulation signal V _PO, modulation signal V _POBe sent to and lock 544 a Power Limitation signal V of its logical operation Power Limitation comparer 53 outputs _OCWith modulation signal V _PO, export a replacement signal V _RSTTo flip-flop 546, flip-flop 546 receives replacement signal V _RSTAnd an oscillation signal CLK of an oscillator 56, and signal V is switched in output _PWMTo power switch Q ₁, output voltage, output current and the output power of control power supply unit.

Be stored in transformer T ₁Magnetizing inductance on energy ε can be expressed from the next:

$\mathrm{\ϵ}=\frac{1}{2}\×L_P\×I_P^2=\mathrm{Po}\×T---\left(1\right)$

Wherein, I _PWith L _PBe respectively transformer T ₁Primary side current and magnetizing inductance value; P ₀Output power for power supply unit; T is transformer T ₁Switching cycle.Above-mentioned transformer T ₁Primary side current I _PCan be expressed as:

$I_P=\frac{V_{\mathrm{IN}}}{L_P}\×t_{\mathrm{ON}}---\left(2\right)$

Wherein, V _INBe the input power supply; t _ONFor this switches signal V _PWMON time.

By above-mentioned (1) and (2) formula output power P of power supply unit as can be known ₀Can be expressed as:

$\mathrm{Po}=\frac{L_p}{2\×T}\×I_p^2=\frac{V_{\mathrm{IN}}^2\×t_{\mathrm{ON}}^2}{2\×L_P\×T}---\left(3\right)$

Can learn the output power P of power supply unit by equation (3) formula ₀Can be along with input power supply V _INChange and change.When considering safety (safety), the input power supply V of power supply unit _INVoltage range be by alternating current 90 volts (90Vac) to 264 volts (264Vac), higher input voltage (264Vac), the restriction of its output power is usually above the output power restriction of lower input voltage (90Vac), and the input power supply V of high low-voltage _INBetween the difference of several times is often arranged.In the application of practice, different input power supply V _INIdentical output power restriction should be arranged.Though seeing through feedback control circuit, the power supply unit of commonly using automatically to adjust switching signal V _PWMON time t _ON, and make the output power value of being maintained fixed, promptly as sensing signal V _CSBe higher than the accurate position of max power constraint V _MThe time, switch signal V this moment _PWMMaximum ON time t _ONTo be restricted.But be subjected to switching the propagation delay time t of signal generation unit 54 _dInfluence, higher input power supply V _INWith lower input power supply V _INPeak power output will have certain difference, so as the input power supply V of power supply unit _INWhen higher, power supply unit will be exported bigger power, and can make the electronic component of power supply unit must bear higher power, will be easy to generate the situation of damage, and then reduce the serviceable life of power supply unit.

Please refer to Fig. 2, import the oscillogram of the accurate position of Power Limitation of power supply for known switching signal with respect to height; As input power supply V _INDuring for high voltage, the steeper sensing signal V of slope will be produced _{CS, HV}So, the sensing signal V that slope is steeper _{CS, HV}With the accurate position of max power constraint V _MAfter comparing, the switching signal V that this switching signal generation unit 54 is produced _PWMON time t _ON1Shorter.As input power supply V _INDuring for low-voltage, the slow sensing signal V of slope will be produced _{CS, LV}So, the sensing signal V that slope is slow _{CS, LV}With the accurate position of max power constraint V _MAfter comparing, switch the switching signal V that signal generation unit 54 is produced _PWMON time t _ON2Longer.

As sensing signal V _CSBe higher than the accurate position of max power constraint V _MMoment, this switches the switching signal V of signal generation unit 54 _PWMCan be subjected to the influence of transmission delay, can't end immediately, and need through one section propagation delay time t _dAfter just can end, at this propagation delay time t _dWithin, power switch Q ₁Continue conducting, promptly power supply unit will continue output power.Therefore, Shi Ji switching signal V _PWMON time t _OnEqual t _On+ t _dBy as can be known shown in Figure 2, at identical propagation delay time t _dDown, as input power supply V _INDuring for high voltage, the accurate position of actual Power Limitation V _{M, HV}Higher, and input power supply V _INDuring for low voltage, the accurate position of actual Power Limitation V _{M, LV}Be lower than V _{M, HV}

Actual output power is shown below:

$\mathrm{Po}=\frac{V_{\mathrm{IN}}^2\×{(t_{\mathrm{ON}}+t_d)}^2}{2\×L_P\×T}---\left(4\right)$

Compare equation (3) and (4) formula as can be known, owing to be subjected to propagation delay time t _dInfluence, make exciting curent many (V than theoretical value _IN/ L _P) * t _dTherefore, at the input power supply V that imports high voltage _INThe time, will have the accurate position of bigger Power Limitation, and export higher power.Though should propagation delay time t _dVery short, still less usually between the scope of 250ns because of this switching cycle T of higher operating frequency to 300ns, so should propagation delay time t _dMore shape aggravation of the influence that is caused.

Therefore, the present invention is promptly at the switching control device that proposes a kind of primary power supplier with side at the problems referred to above, it can use photo-coupler, secondary side feedback control circuit and current sensing resistor, be the output voltage and the output current of may command power supply unit, so can reduce the component number of power supply unit, and then reduce the volume and the cost of manufacture of power supply unit.In addition, the present invention more can reach under the broad input voltage range identical output power restriction.

Summary of the invention:

Fundamental purpose of the present invention, be to provide a kind of switching control device of primary power supplier with side, it is by primary power supplier with side, and the output voltage of controllable power supply and output current, to reduce component number, reduced volume and the saving manufacturing cost of power supply unit.

Another object of the present invention is to provide a kind of switching control device of primary power supplier with side, and it is by wave generating unit, reaches the purpose of identical output power restriction under the input voltage range of broadness.

The switching control device of primary power supplier with side of the present invention, it includes a back coupling synthesis unit, one wave generating unit, one Power Limitation unit, one oscillator and one switches the signal generation unit, the back coupling synthesis unit receives a supply voltage of the primary side of power supply unit, output one back coupling signal, wave generating unit then receives a sawtooth wave signal of supply voltage and oscillator generation, output and the accurate position of a Power Limitation, the output voltage of supply voltage and power supply unit is proportional, one sensing signal of the accurate position of Power Limitation unit received power restriction and power supply unit, export a Power Limitation signal to switching the signal generation unit, switch the signal generation unit and also receive the sensing signal, the oscillation signal that back coupling signal and oscillator produce, signal is switched in output one, controls the output voltage of this power supply unit, output power and output current.

The invention has the beneficial effects as follows: the switching control device that a kind of primary power supplier with side is provided, it is to pass through primary power supplier with side, and the output voltage of controllable power supply and output current can reduce component number, reduced volume and the saving manufacturing cost of power supply unit.And can pass through wave generating unit, under the input voltage range of broadness, reach the purpose of identical output power restriction.

Description of drawings:

Fig. 1 is the circuit diagram of known power supply unit;

Fig. 2 imports the oscillogram of the accurate position of Power Limitation of power supply with respect to height for known switching signal;

Fig. 3 is the circuit diagram of the embodiment of the invention;

Fig. 4 is the adjustment unit of the embodiment of the invention and the circuit diagram of back coupling synthesis unit;

Fig. 5 is the circuit diagram of the wave generating unit of the embodiment of the invention;

Fig. 6 is the circuit diagram of the Power Limitation waveform unit of the embodiment of the invention;

Fig. 7 is the curve map of the accurate position of Power Limitation of the present invention with respect to supply voltage;

The accurate position of Fig. 8 Power Limitation of the present invention is with respect to the oscillogram of switching signal.

The figure number explanation:

5 switching control devices, 53 Power Limitation comparers

54 switch signal generation unit 542 comparer 544 and locks

546 flip-flops, 56 oscillators, 6 switching control devices

61 adjustment units, 611 electric crystals, 612 electric crystals

613 electric crystals, 614 electric crystals, 615 electric crystals

62 award synthesis unit 621 electric crystals 622 electric crystals

623 electric crystals, 624 electric crystals, 625 first operational amplifiers

626 first electric crystals, 627 electric crystals, 628 electric crystals

629 electric crystals, 63 Power Limitation unit 64 switch the signal generation unit

642 comparers 644 and lock 646 anti-devices

65 wave generating unit 651 the 3rd operational amplifier 652 the 3rd electric crystal with

653 right electric crystal 654 left electric crystal 66 oscillators

670 electric crystals, 671 electric crystals, 672 second electric crystals

675 second operational amplifiers, 676 Zener diodes, 68 Power Limitation waveform unit

681 electric crystals, 682 electric crystals, 683 converting units

685 electric crystals, 686 electric crystal C _STStart electric capacity

CLK oscillation signal D _ARectifier I ₁First electric current

I ₂Second electric current I ₃The 3rd electric current I ₄The 4th electric current

I ₅The 5th electric current I ₆The 6th electric current I ₈The 8th electric current

I _BProportional current I _CSource current I _FDrain current

I _FBFeedback current I ₀Output current I _LAdjust electric current

I _LMTThe Power Limitation electric current I _RReference current I _SAWSawtooth current

I _TRestriction current source I _THSawtooth wave restriction electric current I _VCCSupply of current

I _XThe first current source N _AAuxiliary winding N _SSecondary side winding

O ₁Photo-coupler Q ₁Power switch Q ₂Electric crystal

R ₁First resistance R ₂Second resistance R ₃The 3rd resistance

R ₄The 4th resistance R ₅The 5th resistance R ₆The 6th resistance

R ₇The 7th resistance R ₈The 8th resistance R _SDetect resistance

R _STStarting resistance R _KResistance R ₀Current sensing resistor

T ₁Transformer t _dTime delay t _ON1ON time

t _ON2ON time V _AAuxiliary winding voltage V _CCSupply voltage

V _CSSensing signal V _{CS, HV}Sensing signal V _{CS, LV}The sensing signal

V _FBBack coupling signal V _INInput power supply V _LMTThe accurate position of Power Limitation

V _MThe accurate position of Power Limitation V _{M, HV}The accurate position of Power Limitation V _{M, LV}The accurate position of Power Limitation

V ₀Output voltage V _OCPower Limitation signal V _POThe modulation signal

V _PWMSwitch signal V _RReference voltage V _RSTThe replacement signal

V _SAWSawtooth wave signal Z ₁Zener diode

Embodiment:

Further understand and understanding for your auditor is had architectural feature of the present invention and the effect reached, sincerely help with preferred embodiment and cooperate detailed explanation, illustrate as after:

Please refer to Fig. 3, be the circuit diagram of the embodiment of the invention; The present invention need not use photo-coupler and secondary side feedback control circuit, the V in the diagram _AWith V _SBe respectively transformer T ₁The promptly auxiliary winding N of once survey winding _AWith secondary side winding N _SVoltage, auxiliary winding N _ASee through rectifier D _ASupply voltage V is provided _CC, secondary side winding voltage V _SWith auxiliary winding voltage V _ACan be expressed as:

$V_S=N_S\frac{\mathrm{d\φ}}{\mathrm{dt}}---\left(5\right)$

$V_A=N_A\frac{\mathrm{d\φ}}{\mathrm{dt}}---\left(6\right)$

N wherein _SBe transformer T ₁The number of turn of secondary side winding; φ is transformer T ₁Magnetic flux; N _ABe transformer T ₁The number of turn of auxiliary winding.

By above-mentioned equation (5) and (6) Shi Kede:

$V_A=\frac{N_A}{N_S}\×V_S---\left(7\right)$

Can learn auxiliary winding voltage V by aforesaid equation (7) formula _AWith transformer T ₁Secondary side winding voltage V _SBe directly proportional, because auxiliary winding voltage V _ACan be along with secondary side winding voltage V _SSo change and changing is by detecting transformer T ₁The promptly auxiliary winding voltage V of primary side voltage _A, promptly can learn the output voltage of power supply unit.

Multiple with reference to figure 3, switching control device 6 of the present invention includes an adjustment unit 61, a back coupling synthesis unit 62, a Power Limitation unit 63, a switching signal generation unit 64, a wave generating unit 65 and an oscillator 66.Adjustment unit 61, back coupling synthesis unit 62 receive supply voltage V with wave generating unit 65 _CC, adjustment unit 61 is connected with back coupling synthesis unit 62, and the output terminal of back coupling synthesis unit 62 is connected to and switches signal generation unit 64, and back coupling synthesis unit 62 is according to supply voltage V _CCChange and produce a directly proportional feedback current I _FB(as shown in Figure 4), this feedback current I _FBRelatively produce back coupling signal V _FB, switch signal V with control _PWMON time t _ON

As output current I ₀Increase transformer T ₁Secondary side winding voltage V _SWith auxiliary winding voltage V _AReduce supply voltage V _CCAlso reduce feedback current I relatively _FBWill be along with minimizing, and feedback signal V _FBWill increase this back coupling signal V _FBIncrease will make switches signal V _PWMON time t _ONIncrease, to improve the supply voltage V of power supply unit _CCWith output voltage V ₀On the contrary, as output current I ₀Reduce transformer T ₁Secondary side winding voltage V _SWith auxiliary winding voltage V _AWill increase, and supply voltage V _CCCan be along with increase, make feedback current I _FBIncrease, and back coupling signal V _FBCan reduce this back coupling signal V _FBReduction will make switches signal V _PWMON time t _ONReduce, to reduce the supply voltage V of power supply supply _CCWith output voltage V ₀

When load change, transformer T flows through ₁Auxiliary winding N _AElectric current can be along with change, the variable quantity of this electric current can be at rectifier D _AWith auxiliary winding N _AThe different voltage drop of last generation so will influence the detecting output voltage V ₀Degree of accuracy, the present invention addresses the above problem by adjustment unit 61, allows auxiliary winding N _AWith rectifier D _AOn voltage drop remain certain value.Adjustment unit 61 produces one and adjusts electric current I _L(as shown in Figure 4), be in order to compensation feedback current I _FBVariable quantity, adjust electric current I _LWith feedback current I _FBBe inversely proportional, so can keep the rectifier D that flows through _AWith auxiliary winding N _ASupply of current I _VCCBe a fixing current value, the supply of current I of this definite value _VCCCan make when being carried on change rectifier D _AWith auxiliary winding N _AOn voltage drop remain certain value, so can improve and see through auxiliary winding N _AThe detecting output voltage V ₀Degree of accuracy.

Multiple with reference to figure 3, switch signal generation unit 64 and be connected to back coupling synthesis unit 62, Power Limitation unit 63, oscillator 66 and power switch Q ₁, switching signal generation unit 64 is to receive sensing signal V _CS, feedback signal V _FB, Power Limitation signal V _OCWith oscillation signal CLK, switch signal V with output _PWMTo power switch Q ₁ Power Limitation unit 63 is a comparer, its computing sensing signal V _CSWith the accurate position of Power Limitation V _LMT, output power restriction signal V _OC

Switch signal generation unit 64 and include a comparer 642, one and lock 644 and a flip-flop 646, comparer 642 is connected to feedbacks synthesis unit 62, the Power Limitation unit 63 sense terminal SENSE with switching control device 6, in order to receive back coupling signal V _FBWith sensing signal V _CS, the back coupling of comparison operation simultaneously signal V _FBWith sensing signal V _CS, in order to produce modulation signal V _POAnd be sent to and lock 644, should reach lock 644 and more be connected to Power Limitation unit 63, in order to received power restriction signal V _OC, and lock 644 logical operation Power Limitation signal V _OCWith modulation signal V _PO, output replacement signal V _RSTTo a replacement end (R) of flip-flop 646, an input end (D) of flip-flop 646 receives more respectively with a clock pulse end (CK) supply voltage V _CCOscillation signal CLK with oscillator 66 sends switches signal V in order to produce _PWM, and transfer to power switch Q by an output terminal (Q) ₁Control end.

In the above-mentioned explanation, flip-flop 646 is a D type flip-flop, and when the output terminal generation excessive power of power supply unit, and lock 644 logical operations export the replacement signal V of the replacement end (R) of D type flip-flop to _RST, will order about the switching signal V that D type flip-flop is adjusted output terminal (Q) output _PWM, reach periodically by switching signal V _PWM, this D type flip-flop can be substituted by SR type flip-flop or JK type flip-flop.

Please refer to Fig. 4, be the adjustment unit of the embodiment of the invention and the circuit diagram of back coupling synthesis unit; Back coupling synthesis unit 62 of the present invention includes a reference current generating circuit, power plural current mirror, feedback current generation circuit and one the 4th resistance R ₄This reference current generating circuit includes one first operational amplifier 625, one first electric crystal 626 and one first resistance R ₁, in order to change a reference voltage V _RReference current I for definite value _RThe power plural current mirror includes one first current mirror, and it includes electric crystal 623,624; One the 3rd current mirror, it includes electric crystal 628,629; One the 4th current mirror, it includes electric crystal 621,622; One the 5th current mirror, it includes electric crystal 670,71; Feedback current produces circuit and includes a Zener diode 676, one second resistance R ₂, one the 3rd resistance R ₃, one second operational amplifier 675 and one second electric crystal 672, in order to produce a feedback current I _FB

The anode of first operational amplifier 625 receives reference voltage V _R, and the output terminal of first operational amplifier 625 is connected to the grid of first electric crystal 626, the source electrode of first electric crystal 626 is connected to the negative terminal of first operational amplifier 625; First resistance R ₁Be connected between the source electrode and earth terminal of first electric crystal 626, the drain electrode of first electric crystal 626 produces the reference current I of definite value _RDrain electrode with first electric crystal 626 is connected the grid of electric crystal 623,624 with electric crystal 623, and the source electrode of electric crystal 623,624 all is connected to supply voltage V _CCThe grid of electric crystal 628,629 is connected with the drain electrode of electric crystal 624,628, and the source electrode of electric crystal 628,629 all is connected to earth terminal; The grid of electric crystal 621,622 is connected with the drain electrode of electric crystal 621,629,670, and the source electrode of electric crystal 621,622 all is connected to supply voltage V _CC

Multiple with reference to figure 4, the source electrode of electric crystal 670,671 is connected to supply voltage V _CC, the grid of electric crystal 670,671 is connected to the drain electrode of second electric crystal 672 with the drain electrode of electric crystal 671; The drain current of second electric crystal 672 is feedback current I _FB, the grid of second electric crystal 672 is connected to the output terminal of second operational amplifier 675, and the source electrode of second electric crystal 672 is connected to the negative terminal of second operational amplifier 675, second resistance R ₂Be connected between the source electrode and earth terminal of second electric crystal 672 the 3rd resistance R ₃Be connected between the anode and earth terminal of second operational amplifier 675, the anode of Zener diode 676 is connected to the anode of second operational amplifier 675, and the negative electrode of Zener diode 676 is connected to supply voltage V _CCThe 4th resistance R ₄Be connected between the drain electrode and earth terminal of electric crystal 622, in order to the drain current I of conversion electric crystal 622 _FFor feedbacking signal V _FB

The reference current I of definite value _RBe reference voltage V by first operational amplifier 625 _RProduce the reference current I of this definite value _RCan be expressed as I _R=V _R/ R ₁First current mirror is the reference current I by definite value _RMap out one first electric current I ₁, the 3rd current mirror is by first electric current I ₁Map out one the 3rd electric current I ₃Work as output voltage V ₀When changing along with load change, transformer T ₁Auxiliary winding N _ACorresponding supply voltage V will be produced _CC, feedback current I _FBCan be expressed as:

$I_{\mathrm{FB}}=\frac{\mathrm{Vcc}-V_z}{R_2}---\left(8\right)$

V wherein _ZVoltage for Zener diode 676.

By following formula as can be known, feedback current I _FBBe along with supply voltage V _CCThe directly proportional change of change, as supply voltage V _CCWhen reducing along with the load increase, feedback current I _FBTo shown in equation (8) formula, reduce; The 5th current mirror is by feedback current I _FBMap out one the 5th electric current I ₅, because the 3rd electric current I ₃Be definite value, so feedback current I _FBDecline is with respect to the 5th electric current I ₅During decline, according to I ₄=I ₃-I ₅Make the 4th electric current I ₄Increase; The 4th current mirror is by the 4th electric current I ₄Map out drain current I _F, the 4th resistance R ₄Change this drain current I _FFor feedbacking signal V _FBTherefore, because the 4th electric current I ₄Increase, so drain current I _FAlso improve, and back coupling signal V _FBTo increase thereupon.Back coupling signal V _FBIncrease the feasible signal V that switches _PWMON time t _ONAlso increase, promptly improve output voltage V ₀Opposite, because load reduces and makes output voltage V ₀During increase, feedback current I _FBWill increase back coupling signal V _FBWill reduce the feasible signal V that switches _PWMON time t _ONAlso reduce, to reduce output voltage V ₀

Multiple with reference to figure 3, transformer T ₁Auxiliary winding N _AThe voltage V that is produced _AWill be through rectifier D _ARectification provides supply voltage V to switching control device 6 _CC, auxiliary winding voltage V _ABe to change according to the change of load, just different loads will make assists winding N _ALast different voltage, the auxiliary winding voltage V of producing _AThe voltage of the change that is produced will cause feedback current I _FBWith supply of current I _VCCChange the supply of current I of change thereupon _VCCWill be at rectifier D _AWith auxiliary winding N _AThe different voltage drop of last generation is so for the auxiliary winding voltage V of detecting _AAccuracy, will have great influence.For fear of at rectifier D _AWith auxiliary winding N _AUpward produce different voltage drops, must make supply of current I _VCCBe definite value.

Multiple with reference to figure 4, the present invention produces by adjustment unit 61 to adjust electric current I _L, in order to compensation feedback current I _FBVariable quantity, that is to say, as feedback current I _FBAlong with supply voltage V _CCChange and during proportional change, this adjustment unit 61 is to make the adjustment electric current I _LWith feedback current I _FBChange and inversely proportional modulation makes supply of current I _VCCRemain definite value, adjustment unit 61 includes the power plural current mirror, and it includes one second current mirror, includes electric crystal 623,627; One the 6th current mirror, it includes electric crystal 671,613; One the 7th current mirror, it includes electric crystal 611,612; One the 8th current mirror, it includes electric crystal 614,615.

The grid of electric crystal 627 is connected to the grid of electric crystal 623, and the source electrode of electric crystal 613,627 is connected to supply voltage V _CC, the drain electrode of electric crystal 611,615,627 is to be connected with the grid of electric crystal 611,612; The grid of electric crystal 614,615 is to be connected with the drain electrode of electric crystal 613,614, and the source electrode of electric crystal 611,612,614,615 all is connected to earth terminal, and the drain electrode of electric crystal 612 is connected to supply voltage V _CCThe grid of electric crystal 613 is connected to the grid of electric crystal 671.

The 6th current mirror is by feedback current I _FBMap out one the 6th electric current I ₆, second current mirror is by definite value reference current I _RMap out second electric current I ₂, the 8th current mirror is by the 6th electric current I ₆Map out the 8th electric current I ₈, the 7th current mirror is by second electric current I ₂With the 8th electric current I ₈The current value that subtracts each other maps out the adjustment electric current I _L, this adjusts electric current I _LCan be expressed as:

I _L＝N ₇(I ₂-N ₈×I ₆) (9)

Wherein, N ₇With N ₈The ratio of not representing the 7th current mirror and the 8th current mirror is because the 6th current mirror is by feedback current I _FBMap out six electric current I ₆So equation (9) formula can be expressed as:

I _L＝N ₇(I ₂-N ₈×N ₆×I _FB) (10)

Wherein, N ₆It is the ratio of the 6th current mirror.

Can learn supply of current I by Fig. 4 _VCCCan be expressed as I _VCC=I _FB+ I _L, and learn according to equation (10) formula, as feedback current I _FBDuring increase, adjust electric current I _LTo decrease, otherwise as feedback current I _FBDuring decline, adjust electric current I _LTo increase thereupon.Therefore the adjustment electric current I is set _LCan make supply of current I _VCCRemain definite value, to avoid rectifier D _AWith auxiliary winding N _AThe different voltage drop of last generation, and have influence on the auxiliary winding voltage V of detecting _AAccuracy.

Please refer to Fig. 5, be the circuit diagram of the wave generating unit of the embodiment of the invention; This wave generating unit 65 includes a source current and produces circuit, one the 8th resistance R ₈, one first current source I _X, a Power Limitation waveform unit 68 and the 9th current mirror, it includes a right electric crystal 653 and a left electric crystal 654; Right electric crystal 653 is connected with the source electrode of left electric crystal 654, and the grid of right electric crystal 653, left electric crystal 654 is connected with the drain electrode of left electric crystal 654, the 3rd electric crystal 652; The 8th resistance R ₈Be connected between the drain electrode and earth terminal of right electric crystal 653; The first current source I _XBe connected to supply voltage V _CCAnd between the source electrode of right electric crystal 653, left electric crystal 654; Power Limitation waveform unit 68 is connected to supply voltage V _CCAnd between the drain electrode of right electric crystal 653, Power Limitation waveform unit 68 also is connected a sawtooth wave signal V of reception oscillator 66 with oscillator 66 _SAW, in order to export a Power Limitation electric current I _LMT

Wherein, this source current generation circuit comprises one the 5th resistance R ₅, one the 6th resistance R ₆, one the 3rd operational amplifier 651, one the 3rd electric crystal 652 and one the 7th resistance R ₇The 5th resistance R ₅Be connected to supply voltage V _CCAnd between the anode of the 3rd operational amplifier 651, the 6th resistance R ₆Be connected between the anode and earth terminal of the 3rd operational amplifier 651, the output terminal of the 3rd operational amplifier 651 is connected to the grid of the 3rd electric crystal 652, and the negative terminal of the 3rd operational amplifier 651 is connected to the source electrode of the 3rd electric crystal 652, the 7th resistance R ₇Be connected between the source electrode and earth terminal of the 3rd electric crystal 652, the drain current that the drain electrode of the 3rd electric crystal 652 produces is a source current I _C

Multiple with reference to figure 5, supply voltage V _CCThrough the 5th resistance R ₅With the 6th resistance R ₆The voltage after partial signal sees through source current and produces circuit and this voltage signal is converted to be proportional to supply voltage V _CCSource current I _C, it can be expressed as:

$I_C=\frac{\mathrm{Vcc}}{R_7}\&times;\left(\frac{R_6}{{\mathrm{<figure-callout\; id="5"\; label="R"\; filenames="C20051008521200271.png"\; state="\{\{state\}\}">R</figure-callout>}}_5+R_6}\right)---\left(11\right)$

The 9th current mirror is by source current I _CDrain electrode at right electric crystal 653 maps out a proportional current I _B, and the first current source I _XCan be expressed as:

I _X＝I _B+I _C (12)

Multiple with reference to figure 5, this Power Limitation waveform unit 68 is connected in supply voltage V _CCAnd between the 9th current mirror, and be connected in this oscillator 66, receive this sawtooth wave signal V _SAWWith this supply voltage V _CC, produce a Power Limitation electric current I _LMT, this Power Limitation electric current I _LMTWith proportional current I _BAfter the addition, see through the 8th resistance R again ₈Drain electrode at right electric crystal 653 produces the accurate position of Power Limitation V _LMT, it is to be expressed as:

V _LMIT＝I _B×R ₈+I _LMT×R ₈ (13)

Suppose I _B=I _C, replace I by aforesaid equation (11) formula _B, Power Limitation signal V _LMTCan be expressed as:

$V_{\mathrm{LMIT}}=(\frac{R_8}{R_7}\&times;\frac{R_6}{{\mathrm{<figure-callout\; id="5"\; label="R"\; filenames="C20051008521200271.png"\; state="\{\{state\}\}">R</figure-callout>}}_5+{\mathrm{<figure-callout\; id="6"\; label="R"\; filenames="C20051008521200291.png"\; state="\{\{state\}\}">R</figure-callout>}}_6}\&times;V_{\mathrm{CC}})+I_{\mathrm{LMT}}\&times;R_8---\left(14\right)$

The output power of known power source supply is the product of output voltage and output current, therefore, if the output power of modulation power supply unit that can be suitable then can be reached the requirement of deciding electric current.If power supply unit is P in the output power of full load _O1=V ₀* I ₀, when the output current of power supply unit during greater than setting value, power supply unit will enter constant current mode, and the output current strangulation in setting value, is reduced to half of former setting voltage up to output voltage, and promptly output voltage is at V ₀With 0.5V ₀Scope in the time, in setting value, therefore, when output current is considered as definite value, output voltage is reduced to original half with the strangulation output current, can obtain output power is P _O2=0.5 * V ₀* I ₀

By the relation of energy conversion, the output power P of power supply unit _OCan be expressed as:

P _O＝(1/2)×L _P×I _P ²×f (15)

L wherein _PBe transformer T ₁Primary side magnetizing inductance value; I _PBe transformer T ₁Primary side current; F is a switching frequency.If P _O1With P _O2The primary side peak point current be respectively I _P1With I _P2, I then _P1With I _P2Show under must satisfying:

$\frac{P_{O1}}{P_{O2}}=\frac{V_O{I}_O}{0.5V_O{I}_O}=\frac{\frac{1}{2}{L}_P\&CenterDot;I_{\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="C20051008521200271.png,C20051008521200291.png"\; state="\{\{state\}\}">P</figure-callout>}1}^2\&CenterDot;\mathrm{<figure-callout\; id="1"\; label="f"\; filenames="C20051008521200271.png,C20051008521200291.png"\; state="\{\{state\}\}">f</figure-callout>}}{\frac{1}{2}{L}_P\&CenterDot;I_{P2}^2\&CenterDot;f}---\left(16\right)$

By equation (16) Shi Kede:

I _P2＝0.707×I _P1 (17)

I wherein _P1Primary side current for maximum output current.

With reference to as can be known above-mentioned, when output voltage reduce to original half, be 0.707 times of primary side current of maximum output current situation by the restriction primary side current, promptly can reach and decide electric current output.From the above, if want that at output voltage be V ₀With 0.5V ₀Scope in the output current strangulation in setting value, then need the accurate position of Power Limitation of modulation switching controller inside.

Please refer to Fig. 6, be the circuit diagram of the Power Limitation waveform unit of the embodiment of the invention; This Power Limitation waveform unit 68 includes a converting unit 683,1 the tenth current mirror, 1 the 11 current mirror, a restriction current source I _TWith first electric current I ₁, converting unit 683 connects this oscillator 66, receives sawtooth wave signal V _SAW, and with sawtooth wave signal V _SAWThe magnitude of voltage equal proportion convert a sawtooth current I to _SAW, I _SAW=V _SAW/ R _A, R _AResistance value for converting unit 683.The tenth current mirror connects converting unit 683, receives this sawtooth current I _SAW, the tenth current mirror includes electric crystal 681 and electric crystal 682, and electric crystal 681 is connected and is connected with converting unit 683 with the drain electrode of electric crystal 681 with the grid system of electric crystal 682.Converting unit 683 output sawtooth current I _SAWFlow into the drain electrode of electric crystal 681, and produce sawtooth wave restriction electric current I in the drain electrode mapping of electric crystal 682 _TH, I _TH=N ₁₀* I _SAW, N ₁₀It is the ratio of the tenth current mirror.Electric crystal 681 is connected with the source electrode of electric crystal 682, and is connected to restriction current source I again _TTherefore, the sawtooth wave restriction electric current I of the tenth current mirror output _THLowest high-current value be by restriction current source I _TLimit N ₁₀* I _SAW≤ I _T

The 11 current mirror includes electric crystal 685 and electric crystal 686.Electric crystal 685 is connected to supply voltage V with the source electrode of electric crystal 686 _CC Electric crystal 685 is connected with the grid of electric crystal 686 and with the drain electrode of electric crystal 685,682 with feedback first electric current I of first current mirror of synthesis unit 62 ₁Be connected (as shown in Figure 4) this first electric current I ₁Be by this reference current I _RShine upon generation.Sawtooth wave restriction electric current I _THWith first electric current I ₁Flow into the drain electrode of electric crystal 685, and produce the Power Limitation electric current I in the drain electrode mapping of electric crystal 686 _LMTThis Power Limitation electric current I _LMT=N ₁₁* (I _TH+ I ₁), N ₁₁It is the ratio of the 11 current mirror.

Please refer to Fig. 7, be the curve map of the accurate position of Power Limitation of the present invention with respect to supply voltage; When it exports the output current of definite value for power supply unit, the accurate position of Power Limitation V _LMTWith respect to supply voltage V _CCCurve map.According to equation (15) formula and (16) formula, can determine the curve on Fig. 7, when output voltage is V ₀, and output current is the definite value electric current I ₀The time, the accurate position of Power Limitation V _LMTBe V _X, supply voltage this moment is V _CCWhen output voltage is 0.5V ₀, and output current is the definite value electric current I ₀The time, the accurate position of Power Limitation V _LMTBe 0.707V _X, supply voltage this moment is 0.5V _CC

Multiple with reference to figure 5, suppose $K_X=\frac{R_8}{R_7}\&times;\frac{R_6}{{\mathrm{<figure-callout\; id="5"\; label="R"\; filenames="C20051008521200271.png"\; state="\{\{state\}\}">R</figure-callout>}}_5+{\mathrm{<figure-callout\; id="6"\; label="R"\; filenames="C20051008521200291.png"\; state="\{\{state\}\}">R</figure-callout>}}_6},$ And K _Y=I _LMT* R ₈, Power Limitation signal V from the above _LMT=V _XWith V _LMT=0.707V _XCorrespond respectively to supply voltage V _CCWith 0.5V _CC, can learn from equation (14) formula:

V _CC×K _x+K _y＝V _X (18)

0.5V _CC×K _x+K _y＝0.707V _X (19)

Multiple with reference to figure 5, the present invention can produce the accurate position of Power Limitation V by wave generating unit 65 _LMT, according to equation (18) formula and (19) formula, the accurate position of Power Limitation V _LMTCan be according to suitably selecting K _XWith K _Y, promptly appropriately select the 5th resistance R ₅, the 6th resistance R ₆, the 7th resistance R ₇With the 8th resistance R ₈Resistance value and Power Limitation electric current I _LMT, promptly can produce the accurate position of Power Limitation V _LMTWhen supply voltage is V _CCThe time, the accurate position of Power Limitation V _LMTBe clamped at voltage V _X, peak power output is restricted.

Wave generating unit 65 proposed by the invention is not needing to detect input voltage, promptly can be applicable to the output power restriction.Sensing signal V when power supply unit _CSBe higher than the accurate position of this Power Limitation V _LMTThe time, this switching control device will be periodically by switching signal V _PWMAs shown in Figure 8, the accurate position of the Power Limitation that produced of wave generating unit 65 of the present invention V _LMTHave slope, non-is fixing value as commonly using.

When the input power supply of power supply unit is high input voltage, power supply unit will produce the steeper sensing signal V of slope _{CS, HV}, it can be subjected to a lower Power Limitation signal V _LMTRestrict.And when the input power supply of power supply unit is low input, power supply unit will produce the slow sensing signal V of slope _{CS, LV}, it can be subjected to a higher Power Limitation signal V _LMTRestrict.In case sensing signal V _{CS, HV}Or V _{CS, LV}Be higher than the accurate position of this Power Limitation V _LMTThe time, this switches signal V _PWMBe about to end.

The accurate position of the Power Limitation that wave generating unit 65 of the present invention is produced V _LMT, mainly when input voltage was higher, Power Limitation will be lower, and when input voltage was low, Power Limitation will be higher, so adds propagation delay time t _dAfter, for lower input voltage and higher input voltage, can reach an identical output power restriction.In addition, when the input voltage of power supply unit is crossed (brownout condition) when low, for prevent output current excessive with the restriction output power, with the protection power supply unit, the accurate position of the Power Limitation V that this wave generating unit 65 produces _LMT, also can limit low input, the sensing signal V that is produced _{CS, BO}, with the output power of restriction power supply unit.

In sum, the present invention proposes the switching control device 6 of primary power supplier with side, and include adjustment unit 61 and feedback synthesis unit 62, and in conjunction with transformer T ₁Auxiliary winding N _A, be certain value with the stable output voltage of adjusting power supply unit, moreover the switching control device 6 that the present invention proposes more include wave generating unit 65, reaching the output power restriction, and to make output current be certain value.The switching control device 6 that the present invention proposes sees through primary side control circuit, can stablize and adjust output voltage and the output current that certain value is provided, so can not need at transformer T ₁Secondary side feedback control circuit is set, thereby reach number of parts, volume and the cost that reduces power supply unit.

The above, it only is preferred embodiment of the present invention, be not to be used for limiting scope of the invention process, all according to the described shape of the present patent application claim, structure, feature and principle etc. change and modify, all should be contained in the claim of the present invention.

Claims (12)

1. the switching control device of a primary power supplier with side is characterized in that, includes:

One oscillator produces an oscillation signal and a sawtooth wave signal;

One feedbacks synthesis unit, receives a supply voltage of the primary side of this power supply unit, and signal is feedback in output one, and output voltage of this supply voltage and this power supply unit is proportional;

One wave generating unit receives this supply voltage and this sawtooth wave signal, exports the accurate position of a Power Limitation;

One Power Limitation unit receives a sensing signal of the accurate position of this Power Limitation and this power supply unit, exports a Power Limitation signal;

One switches the signal generation unit, receives this oscillation signal, this Power Limitation signal, this sensing signal and this back coupling signal, and signal is switched in output one, controls output voltage, output current and the output power of this power supply unit.

2. the switching control device of primary power supplier with side as claimed in claim 1 is characterized in that, this back coupling synthesis unit includes:

One reference current generating circuit, a reference voltage of reception definite value, a reference current of output definite value;

One first current mirror shines upon this reference current, produces one first electric current;

One the 3rd current mirror shines upon this first electric current, produces one the 3rd electric current;

One feedback current produces circuit, receives this supply voltage, produces a feedback current;

One the 5th current mirror shines upon this feedback current, produces one the 5th electric current;

One the 4th current mirror shines upon one the 4th electric current, produces a drain current, and the 4th electric current is the difference of the 5th electric current and the 3rd electric current;

One the 4th resistance is changed this drain current, produces this back coupling signal.

3. the switching control device of primary power supplier with side as claimed in claim 2 is characterized in that, this reference current generating circuit includes:

One first resistance, an end is connected in an earth terminal;

One first operational amplifier, it includes an anode, a negative terminal and an output terminal, and this anode receives this reference voltage;

One first electric crystal, it includes one source pole, a grid and a drain electrode, this source electrode is connected in this negative terminal of this first operational amplifier and the other end of this first resistance, and this grid is connected in this output terminal of this first operational amplifier, this reference current of this drain electrode output definite value.

4. the switching control device of primary power supplier with side as claimed in claim 2 is characterized in that, this feedback current produces circuit and includes:

One base is received diode, and it includes an anode and a negative electrode, and this negative electrode receives this supply voltage;

One second operational amplifier, it includes an anode, a negative terminal and an output terminal, and this anode is connected in this base and receives this anode of diode;

One second resistance, an end is connected in an earth terminal;

One the 3rd resistance, an end is connected in this earth terminal, and the other end is connected in this anode of this second operational amplifier;

One second electric crystal, it includes one source pole, a grid and a drain electrode, this source electrode is connected in this negative terminal of this second operational amplifier and the other end of this second resistance, and this grid is connected in this output terminal of this second operational amplifier, this this feedback current of drain electrode output.

5. the switching control device of primary power supplier with side as claimed in claim 1 is characterized in that, this wave generating unit includes:

One source current produces circuit, receives this supply voltage, exports a source current;

One the 9th current mirror shines upon this source current, produces a proportional current;

One Power Limitation waveform unit is connected between this supply voltage and the 9th current mirror, and is connected in this oscillator, receives this sawtooth wave signal and this supply voltage, produces a Power Limitation electric current;

One first current source is connected between this supply voltage and the 9th current mirror;

One the 8th resistance is connected between the 9th current mirror and the earth terminal, changes this Power Limitation electric current and this proportional current, produces the accurate position of this Power Limitation.

6. the switching control device of primary power supplier with side as claimed in claim 5 is characterized in that, this source current produces circuit and includes:

One the 5th resistance, an end are connected in this supply voltage;

One the 3rd operational amplifier, it includes an anode, a negative terminal and an output terminal, and this anode is connected in the other end of the 5th resistance;

One the 6th resistance, an end is connected in an earth terminal, and the other end is connected in this anode of the 3rd operational amplifier;

One the 7th resistance, an end is connected in this earth terminal;

One the 3rd electric crystal, it includes one source pole, a grid and a drain electrode, this source electrode is connected in this negative terminal of the 3rd operational amplifier and the other end of the 7th resistance, and this grid is connected in this output terminal of the 3rd operational amplifier, this this source current of drain electrode output.

7. the switching control device of primary power supplier with side as claimed in claim 5 is characterized in that, this Power Limitation waveform unit includes:

One converting unit is connected in this oscillator, receives this sawtooth wave signal, and the magnitude of voltage that ratio is changed this sawtooth wave signal is a sawtooth current;

The tenth current mirror is connected to this converting unit, receives this sawtooth current and this sawtooth current mapping is produced sawtooth wave restriction electric current;

One restriction current source is connected to the tenth current mirror, limits the tenth current mirror and produces this sawtooth wave restriction electric current, and this sawtooth wave restriction current maxima is this restriction current source;

The 11 current mirror, be connected to this supply voltage, the tenth current mirror and this back coupling synthesis unit, receive one first electric current of this sawtooth wave restriction electric current and this back coupling synthesis unit, and shine upon the summation of this sawtooth wave restriction electric current and this first electric current, produce this Power Limitation electric current.

8. the switching control device of primary power supplier with side as claimed in claim 5, it is characterized in that, the 9th current mirror includes a right electric crystal and a left electric crystal, the one source pole of this right side electric crystal is connected with the one source pole of this left side electric crystal, and be connected with this first current source, one drain electrode of this left side electric crystal is connected with a grid of this left side electric crystal and a grid of this right side electric crystal, and produce circuit with this source current and be connected, receive this source current, this proportional current of drain electrode output of this right side electric crystal, and be connected in this Power Limitation waveform unit and the 8th resistance.

9. the switching control device of primary power supplier with side as claimed in claim 1 is characterized in that, this Power Limitation unit is a comparer.

10. the switching control device of primary power supplier with side as claimed in claim 1 is characterized in that, this switching signal generation unit includes:

One comparer receives this back coupling signal of this back coupling synthesis unit output and this sensing signal of this power supply unit, exports a modulation signal;

One and lock, receive this Power Limitation signal of this modulation signal and this Power Limitation unit output, export a replacement signal;

One flip-flop receives this supply voltage, this oscillation signal and this replacement signal, exports this switching signal.

11. the switching control device of primary power supplier with side as claimed in claim 1, it is characterized in that, this back coupling synthesis unit more is connected with an adjustment unit, this adjustment unit receives a feedback current of this supply voltage and this back coupling synthesis unit and a reference current of definite value, produce one and adjust electric current, this feedback current changes along with this supply variation in voltage, and this adjusts this feedback current of current compensation, and a supply of current that makes this supply voltage is a fixed value.

12. the switching control device of primary power supplier with side as claimed in claim 11 is characterized in that, this adjustment unit includes:

One second current mirror, this reference current of mapping definite value, one second electric current of generation definite value;

One the 6th current mirror shines upon this feedback current, produces one the 6th electric current;

One the 8th current mirror shines upon the 6th electric current, produces one the 8th electric current;

One the 7th current mirror, the electric current difference of shining upon this second electric current and the 8th electric current produces this adjustment electric current.

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