CN1818818A - Switching control device with output power limitation and low voltage protection - Google Patents

Abstract

The invention provides a switching control device with output power limitation and low voltage protection, which is used in a power supply and comprises: the driving circuit comprises a hysteresis comparison circuit, a clamping voltage generating unit, a power limit comparator and a driving signal generating unit, wherein the clamping voltage generating unit extracts and clamps the changed input power supply voltage to output a dynamic maximum power limit voltage as the critical reference of power limit. In addition, the input power supply voltage can be compared with the hysteresis critical voltage range value under the condition of too low voltage, namely the drive signal generating unit is controlled to stop outputting the drive signal, and the low input power supply voltage is used for protection.

Description

Switching control device with output power restriction and under-voltage protection

Technical field

The present invention relates to a kind of switching control device, but refer to a kind of power-limiting output and the switching control device that hangs down the input supply voltage protection especially with output power restriction and under-voltage protection.

Background technology

In power supply unit, the PWM handoff technique is a known technology, and it can be used for controlling and the stable output power of adjusting.Build in the power supply unit in various defencive functions such as the over-voltage and over-current protection, be used for protecting this power supply unit and peripheral circuit, to avoid causing nonvolatil injury.The function of the output power restriction of power supply unit is generally used for overload and short-circuit protection.

With reference to figure 1, be known power supply unit circuit diagram.Switching controller U wherein ₁Form by Power Limitation comparer 53, oscillator 56 and drive signal generation unit 54, source as power supply unit 5 drive signals, for example the PWM control integrated circuit 3842, and this PWM control integrated circuit 3842 has been used the occasion at power supply unit widely on commercial applications.In power supply unit 5, input power supply V _INCan be by the starting resistance R of a series connection _STBegin to keep capacitor C to one _STCharge, keep capacitor C by the time _STOn voltage V _CCWhen arriving a trigger voltage, switching controller U ₁Begin action, be used for driving whole power supply unit 5.

After power supply unit 5 starts, switching controller U ₁Needed supply voltage V works _CC, by transformer T ₁Auxiliary winding N _ABy a rectifier D _ATo keeping capacitor C _STCharging provides.At this moment, one detect resistance R _SBe connected in series in power switch Q ₁, detect and flow through power switch Q ₁Transformer T ₁Primary side current I _P, as the peak power output of decision power supply unit 5.The method that realizes is to detect resistance R _SOn a voltage (i.e. current sensing signal V _CS) be sent to the negative terminal of Power Limitation comparer 53.If current sensing signal V _CSGreater than the max power constraint current potential V that sets _M, the voltage potential of 1V for example, this drive signal generation unit 54 drive signal V that will periodically stop using _PWMOutput, and also will limit the peak power output of power supply unit 5.Be stored in transformer T ₁Energy ε on the inductance is:

$\mathrm{\ϵ}=\frac{1}{2}\×L\×I^2=P\×T---\left(1\right)$

Peak power output P can be expressed as follows:

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

$P=\frac{L_P}{2\×T}{{\×I}_P}^2=\frac{{V_{\mathrm{IN}}}^2\×{t_{\mathrm{ON}}}^2}{2{\×L}_P\×T}---\left(3\right)$

I wherein _PWith L _PBe expressed as transformer T respectively ₁Primary side current and primary side inductance value; t _ONBe power switch Q ₁During conducting, drive signal V _PWMON time; T is power switch Q ₁Switching cycle.

Can find that by equation (3) output power P will be along with input voltage V _INChange and change.When considering safety (safety), the input supply voltage scope of power supply unit by 90Vac to 264Vac.The restriction of output power when higher input supply voltage (264Vac) is usually above the restriction when lower input supply voltage (90Vac), and the difference of several times is often arranged between the high-low pressure.Though the feedback control loop by power supply unit can automatically be adjusted ON time t _ON, and make the output power value of being maintained fixed.That is to say, as current sensing signal V _CSBe higher than max power constraint current potential V _MThe time, V for example _CS〉=1V (I _P* R _S〉=1V), this moment maximum ON time t _ONTo be restricted, and reach the primary side current that limits this power supply unit.

Moreover peak power output also is activated the propagation delay time t of signal generation unit 54 _dInfluence.

Cooperate Fig. 1, please refer to Fig. 2, for the propagation delay time causes the output power under the high-low pressure input power supply to limit the potential difference synoptic diagram.Power supply unit 5 is at fixing max power constraint current potential V _MWhen high pressure input power work, can produce the steeper current sensing signal V of slope down, _{CS, HV}With lasting ON time t _On1Short drive signal V _{PWM, HV}Moreover, when low pressure input power work, can produce the slow current sensing signal V of slope _{CS, LV}With lasting ON time t _On2Long drive signal V _{PWM, LV}

In fact, as current sensing signal V _CSBe higher than max power constraint current potential V _MMoment (I _P* R _S〉=1V), the drive signal V of this drive signal generation unit 54 _PWMCan be through one section propagation delay time t _dAfter just can end.At this propagation delay time t _dWithin, power switch Q ₁Can continue conducting, and continue transmitted power.Therefore, Shi Ji drive signal V _PWMON time t _ONEqual t _ON+ t _dThat is to say, when input supply voltage is higher, power switch Q ₁Actual ON time t _{On1, d}Also increase thereupon, thereby actual Power Limitation current potential V _{M, HV}Higher, and then it is a lot of to cause power supply unit 5 output powers to increase.What need to specify is, no matter is under higher Yu lower input supply voltage, in identical power supply unit, and its propagation delay time t _dSize be identical.

When input supply voltage is low, the ON time ton2 of power switch Q1 reality, d also can increase thereupon, actual Power Limitation current potential V _{M, LV}Power Limitation current potential V when meeting is more higher than input supply voltage _{M, HV}Low.Thereby cause power supply unit 5 under very large-scale input voltage, can produce the output power of several times difference.And actual output power P is as follows:

$P=\frac{{V^2}_{\mathrm{IN}}\×{(t_{\mathrm{ON}}+t_D)}^2}{2{\×L}_P\×T}---\left(4\right)$

The formula of more above-mentioned explanation (3) and (4) are because the propagation delay time t of IC inside _dWill make exciting curent many (V than theoretical value _IN/ L _P) * t _d, therefore, when high pressure input power supply, will have bigger Power Limitation current potential.Though should propagation delay time t _dVery short, usually between the scope of 250ns to 300ns, and under the higher operating frequency, this propagation delay time t _dThe influence that is caused aggravates more.So input supply voltage V _INShould suitably compensate, make this input supply voltage V _INOutput power can not have the greatest impact.

Summary of the invention

In view of this, the present invention has the switching control device of output power restriction and under-voltage protection, and its fundamental purpose is can carry out the restriction of output power dynamically when the input supply voltage change of power supply unit.Moreover, if input supply voltage is low excessively, then can stop the output of power supply unit, so can reach the protection of low input supply voltage.

In order to reach above-mentioned purpose, the invention provides a kind of switching control device with output power restriction and under-voltage protection, be used in the power supply unit, it follows the variation of an input supply voltage, and then a drive signal of control and adjustment one power switch, include: a magnetic hysteresis comparator circuit, this input supply voltage and a magnetic hysteresis threshold voltage ranges value of reception equal proportion, after comparison operation, export a low-voltage magnetic hysteresis signal; One strangulation voltage generation unit uses the input supply voltage of a deboost source and this variation to carry out computing, in order to export a max power constraint voltage; One Power Limitation comparer, be connected in a sense terminals of this strangulation voltage generation unit and this power supply unit, receive this a max power constraint voltage and a current sensing signal, and this max power constraint voltage and this current sensing signal compared computing, in order to export a power limit signal; An and drive signal generation unit, be connected in a feedback end of this Power Limitation comparer, this magnetic hysteresis comparator circuit, this power supply unit, this sense terminals and this power switch of this power supply unit, receive this power limit signal, this low-voltage magnetic hysteresis signal, a voltage feedback signal and this current sensing signal, in order to export this drive signal to this power switch.

Wherein, this strangulation voltage generation unit connects this deboost source by a totalizer and is formed, and after additive operation is carried out in this input supply voltage that this totalizer will change and this deboost source, exports this max power constraint voltage.This drive signal generation unit includes: a PWM comparer, be connected to this feedback end and this sense terminals of this power supply unit, receive this voltage feedback signal and this current sensing signal, according to this voltage feedback signal of comparison operation and this current sensing signal, in order to export a modulation output signal; One logical circuit is connected in this Power Limitation comparer and this PWM comparer, receives this power limit signal and this modulation output signal in order to export a reset signal; An and trigger, one input end is connected in this magnetic hysteresis comparator circuit, and resets that end is connected in this logical circuit, a frequency end is connected in an oscillator and an output terminal is connected in this power switch, receive this low-voltage magnetic hysteresis signal, this reset signal and an oscillator signal, in order to export this drive signal to this power switch.This trigger can be selected from one of group's combination of D flip-flop, SR D-flip flop or JK D-flip flop.

The present invention also provides a kind of switching control device with output power restriction, be used in the power supply unit, it follows the variation of an input supply voltage, an and then drive signal of control and adjustment one power switch, include: a strangulation voltage generation unit, use the input supply voltage of a deboost source and this variation to carry out computing, in order to export a max power constraint voltage; One Power Limitation comparer, be connected in a sense terminals of this strangulation voltage generation unit and this power supply unit, receive this a max power constraint voltage and a current sensing signal, and this max power constraint voltage and this current sensing signal compared computing, in order to export a power limit signal; One drive signal generation unit, be connected in a feedback end of this Power Limitation comparer, this power supply unit, this sense terminals and this power switch of this power supply unit, receive this power limit signal, a voltage feedback signal and this current sensing signal, in order to export this drive signal to this power switch; When this input supply voltage change, this max power constraint voltage can change thereupon, and then adjust this power limit signal of this Power Limitation comparer output, and the work period of this drive signal of control and this drive signal generation unit output of adjustment, to limit the primary side current of this power supply unit.This device also includes a magnetic hysteresis comparator circuit, receives this input supply voltage and a magnetic hysteresis threshold voltage ranges value of equal proportion, after comparison operation, and output or end a low-voltage magnetic hysteresis signal.This strangulation voltage generation unit connects a deboost source by a totalizer and is formed, and after additive operation is carried out in this input supply voltage that this totalizer will change and this deboost source, exports this max power constraint voltage.This drive signal generation unit includes: a PWM comparer, be connected to the feedback end and the sense terminals of this power supply unit, receive this voltage feedback signal and this current sensing signal, according to this voltage feedback signal of comparison operation and this current sensing signal, in order to export a modulation output signal; One logical circuit is connected in this Power Limitation comparer and this PWM comparer, receives this power limit signal and this modulation output signal in order to export a reset signal; An and trigger, one input end is connected in this magnetic hysteresis comparator circuit, and resets that end is connected in this logical circuit, a frequency end is connected in an oscillator and an output terminal is connected in this power switch, receive this low-voltage magnetic hysteresis signal, this reset signal and an oscillator signal, in order to export this drive signal to this power switch.This trigger can be selected from one of group's combination of D flip-flop, SR D-flip flop or JK D-flip flop.

The present invention uses a magnetic hysteresis comparator circuit to receive the input supply voltage of equal proportion by input resistance; the magnetic hysteresis comparator circuit will be low excessively input supply voltage and magnetic hysteresis threshold voltage ranges value compare computing; in order to export a low-voltage magnetic hysteresis signal; low-voltage magnetic hysteresis signal controlling and driving signal generation unit stops the output of drive signal, as the low excessively protection of power supply unit input supply voltage.

Simultaneously, the present invention uses the input supply voltage of a strangulation voltage generation unit by input resistance reception equal proportion, in order to export a max power constraint voltage.One Power Limitation comparer receives this a max power constraint voltage and a current sensing signal, and carries out comparison operation, in order to export a power limit signal, as the Power Limitation of power supply unit output.

Moreover the present invention uses a drive signal generation unit that is connected in this Power Limitation comparer and power switch to receive this power limit signal, and exportable drive signal is to power switch.By this, when input supply voltage changed, this max power constraint voltage can change thereupon, and then impelled this drive signal generation unit to adjust the work period of drive signal, with the primary side current of restriction power supply unit, and reached the restriction of output power.

Under the low excessively situation of input supply voltage; hysteresis comparator circuit can compare computing with low excessively input supply voltage and magnetic hysteresis threshold voltage ranges value; promptly produce the sluggish signal of low-voltage; stop drive signal output in order to controlling and driving signal generation unit, as low input supply voltage protection.

For feature of the present invention and technology contents are further understood, see also following about detailed description of the present invention and accompanying drawing, yet accompanying drawing only provide with reference to and the explanation usefulness, be not to be used for the present invention is limited.

Description of drawings

Fig. 1 is known power supply unit circuit diagram;

Fig. 2 causes the output power under the high-low pressure input power supply to limit the potential difference synoptic diagram for the propagation delay time;

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

Fig. 4 causes the output power under the high-low pressure input power supply to limit the potential difference synoptic diagram for the propagation delay time of the present invention; And

Fig. 5 is a magnetic hysteresis comparator circuit waveform synoptic diagram of the present invention.

Wherein, description of reference numerals is as follows:

Known:

U ₁Switching controller R _STStarting resistance

C _STKeep electric capacity Q ₁Power switch

D _ARectifier T ₁Transformer

5 power supply units, 53 Power Limitation comparers

54 drive signal generation unit, 56 oscillators

The present invention:

6 power supply units, 60 magnetic hysteresis comparator circuits

62 strangulation voltage generation units, 620 totalizers

63 Power Limitation comparers, 64 drive signal generation unit

642PWM comparer 644 logical circuits

646 triggers, 648 oscillators

Q ₁Power switch R _STStarting resistance

C _STKeep electric capacity Q ₁Power switch

D _ARectifier T ₁Transformer

V _OFFSETBucking voltage V _RThe deboost source

V _LMTMax power constraint voltage Voc power limit signal

V _RSTReset signal V _POThe modulation output signal

V _CSCurrent sensing signal DS low-voltage magnetic hysteresis signal

V _PWMDrive signal CLK oscillator signal

Embodiment

Please refer to Fig. 3, be the circuit diagram of preferred embodiment of the present invention, the present invention is used in the power supply unit 6, is to follow an input supply voltage V _INVariation, and then control a power switch Q ₁Change action, include: magnetic hysteresis comparator circuit 60, strangulation voltage generation unit 62, Power Limitation comparer 63 and drive signal generation unit 64.Magnetic hysteresis comparator circuit 60 is by input resistance R ₁With R ₂Dividing potential drop to obtain the input supply voltage V of equal proportion _IN, and with the input supply voltage V of this equal proportion _INWith a magnetic hysteresis threshold voltage ranges value (lower voltage limit critical value V _L～upper voltage limit critical value V _H) compare computing.Simultaneously, as the input supply voltage V of equal proportion _INBe lower than lower voltage limit critical value V _LThe time, the low-voltage magnetic hysteresis signal DS of magnetic hysteresis comparator circuit 60 outputs one electronegative potential, and be higher than upper voltage limit critical value V _HThe low-voltage magnetic hysteresis signal DS of time output noble potential is to form the signal hysteresis.In the above-mentioned explanation, this magnetic hysteresis threshold voltage ranges value is the upper voltage limit critical value V with respect to input supply voltage 90Vac _HTo a lower voltage limit critical value V with respect to input supply voltage 70Vac _L

Refer again to Fig. 3, this strangulation voltage generation unit 62 connects a deboost source V by a totalizer 620 _RForm, by input resistance R ₁With R ₂Obtain from input supply voltage V _INBucking voltage V after the dividing potential drop _OFFSET, this bucking voltage V _OFFSETWith this deboost source V _RAfter carrying out additive operation by totalizer 620, export a max power constraint voltage V _LMTBecause input supply voltage V _INBe a change value, as the variation between the extremely low input supply voltage 90Vac of high input supply voltage 264Vac.So max power constraint voltage V _LMTAlso be can the change value.By the voltage clamping function of this strangulation voltage generation unit 62, under high input supply voltage, can obtain max power constraint voltage V _{LMT, HV}, under low input supply voltage, can obtain max power constraint voltage V _{LMT, LV}, V wherein _{LMT, LV}Greater than V _{LMT, HV}Voltage potential.

This Power Limitation comparer 63 is connected in this strangulation voltage generation unit 62, receives this max power constraint voltage V of change _LMT, and this max power constraint voltage V that will change _LMTWith a current sensing signal V _CSCompare computing, in order to export the power limit signal V of a change _OC

Refer again to Fig. 3, drive signal generation unit 64 is connected in this magnetic hysteresis comparator circuit 60, this Power Limitation comparer 63, this power switch Q ₁And the feedback end of this power supply unit, receive this low-voltage magnetic hysteresis signal DS and this power limit signal V _OC, to export a drive signal V _PWMTo this power switch Q ₁Wherein drive signal generation unit 64 includes: a PWM comparer 642, a logical circuit 644, a trigger 646 and an oscillator 648.

This PWM comparer 642 is connected to the feedback end of this Power Limitation comparer 63 and this power supply unit, in order to receive a voltage feedback signal V _FBWith this current sensing signal V _CS, this voltage feedback signal of comparison operation simultaneously V _FBWith this current sensing signal V _CS, in order to export a modulation output signal V _POThis modulation output signal V _POBe sent to the logical circuit 644 that is connected in Power Limitation comparer 63 output terminals, this logical circuit 644 is obtained this power limit signal V _OCWith this modulation output signal V _PO, and the logical operation of execution and door (AND), to export a reset signal V _RST

This trigger 646 is connected in this magnetic hysteresis comparator circuit 60, this logical circuit 644, this oscillator 648 and this power switch Q ₁, receive this low-voltage magnetic hysteresis signal DS, this reset signal V _RSTAnd an oscillator signal CLK, in order to export this drive signal V _PWMTo this power switch Q ₁

In the above-mentioned explanation, this trigger 646 is a D flip-flop, and one is reset and held (R) to be connected to the output terminal of this logical circuit 644 in order to receive this reset signal V _RST, one frequency end (CK) is connected to this oscillator 648 in order to receive this oscillator signal CLK, and one input end (D) is connected to the output terminal of magnetic hysteresis comparator circuit 60 in order to receive this low-voltage magnetic hysteresis signal DS, and one output terminal (Q) is connected to this power switch Q ₁Control end in order to export this drive signal V _PWM

This oscillator signal CLK control D flip-flop is obtained this low-voltage magnetic hysteresis signal DS in input end (D), and is presented in this output terminal (Q), simultaneously, and the reset signal V of these logical circuit 644 outputs _RSTBe sent to the replacement end (R) of this D flip-flop, can when overpower takes place, adjust the drive signal V of this D flip-flop output terminal (Q) _PWMThe logical operation of this D flip-flop can be substituted by SR D-flip flop or JK D-flip flop and carry out.

Because max power constraint voltage V _LMTChange can influence the power limit signal V of Power Limitation comparer 63 output _OC, and then via logical circuit 644, trigger 646 in order to adjust drive signal V _PWMOutput, to reach the restriction of output power.Moreover, low-voltage magnetic hysteresis signal DS may command trigger 646 output or output drive signal V not _PWM

Cooperate Fig. 3, please refer to the propagation delay time of the present invention shown in Figure 4 to cause high-low pressure input power supply output power down to limit the potential difference synoptic diagram.Strangulation voltage generation unit 62 is at high input supply voltage and the following max power constraint voltage V that produces of low input supply voltage _LMTBe respectively V _{LMT, HV}With V _{LMT, LV}, and detect resistance R _SThe current sensing signal V that obtains _CSThen be respectively V _{CS, HV}With V _{CS, LV}Current sensing signal V wherein _{CS, HV}, V _{CS, LV}Can be respectively by Power Limitation comparer 63 and max power constraint voltage V _{LMT, HV}, V _{LMT, LV}Compare computing, be respectively t and obtain ON time _On3With t _On4Drive signal V _{PWM, HV}, V _{PWM, LV}In above-mentioned explanation, if consider switching controller U simultaneously ₂In delay that each assembly produced, high input supply voltage and the actual ON time of low input supply voltage are respectively t _On3+ t _dWith t _On4+ t _d

From the above, by the voltage clamping function of this strangulation voltage generation unit 62, allow power supply unit 6 under high pressure or low pressure input power supply, change max power constraint voltage V dynamically _LMT, as the compensation of power supply unit 6 output powers, the max power constraint voltage V that it is actual _LMTFor identical, and can obtain stable and identical output power P.

In conjunction with Fig. 3, please refer to Fig. 5 again, be magnetic hysteresis comparator circuit waveform synoptic diagram of the present invention.At time t ₁To t ₃The time, input supply voltage V _INLess than upper voltage limit critical value V _H, at this moment, input supply voltage V _INPromptly begin to carry out the magnetic hysteresis comparison operation by this magnetic hysteresis comparator circuit 60.In time t ₂The time, input supply voltage V _INBe lower than this lower voltage limit critical value V _L, this moment, this magnetic hysteresis comparator circuit 60 was promptly exported this low-voltage magnetic hysteresis signal DS of electronegative potential, stopped drive signal V in order to control this trigger 646 _PWMOutput; In addition in time t ₃The time, input supply voltage V _INBe higher than this upper voltage limit critical value V _H, this moment, this magnetic hysteresis comparator circuit 60 was promptly exported this low-voltage magnetic hysteresis signal DS of noble potential, recovered drive signal V in order to control this trigger 646 _PWMOutput.

The present invention has the switching control device of output power restriction and under-voltage protection; when the input supply voltage change of power supply unit; carry out the restriction of output power dynamically; if input supply voltage is low excessively; then can stop the output of power supply unit, so can reach the protection of low input supply voltage.

Yet, the above only is the detailed description and the accompanying drawing of the specific embodiment of one of the best of the present invention, feature of the present invention is not limited thereto, be not in order to restriction the present invention, all scopes of the present invention should be as the criterion with following claims, all closing in the embodiment of the spirit variation similar of claims of the present invention with it, all should be contained in the category of the present invention, those skilled in the art in the field of the invention, can think easily and variation or modify all can be encompassed in the claim of the present invention.

Claims (9)

1. the switching control device with output power restriction and under-voltage protection is used in the power supply unit, and it follows the variation of an input supply voltage, and then a drive signal of control and adjustment one power switch, it is characterized in that including:

One magnetic hysteresis comparator circuit, this input supply voltage and a magnetic hysteresis threshold voltage ranges value of reception equal proportion after comparison operation, are exported a low-voltage magnetic hysteresis signal;

One strangulation voltage generation unit uses the input supply voltage of a deboost source and this variation to carry out computing, in order to export a max power constraint voltage;

One Power Limitation comparer, be connected in a sense terminals of this strangulation voltage generation unit and this power supply unit, receive this a max power constraint voltage and a current sensing signal, and this max power constraint voltage and this current sensing signal compared computing, in order to export a power limit signal; And

One drive signal generation unit, be connected in a feedback end of this Power Limitation comparer, this magnetic hysteresis comparator circuit, this power supply unit, this sense terminals and this power switch of this power supply unit, receive this power limit signal, this low-voltage magnetic hysteresis signal, a voltage feedback signal and this current sensing signal, in order to export this drive signal to this power switch.

2. the switching control device with output power restriction and under-voltage protection as claimed in claim 1; wherein; this strangulation voltage generation unit connects this deboost source by a totalizer and is formed; after additive operation is carried out in this input supply voltage that this totalizer will change and this deboost source, export this max power constraint voltage.

3. the switching control device with output power restriction and under-voltage protection as claimed in claim 1, wherein, this drive signal generation unit includes:

One PWM comparer is connected to this feedback end and this sense terminals of this power supply unit, receives this voltage feedback signal and this current sensing signal, according to this voltage feedback signal of comparison operation and this current sensing signal, in order to export a modulation output signal;

One logical circuit is connected in this Power Limitation comparer and this PWM comparer, receives this power limit signal and this modulation output signal in order to export a reset signal; And

One trigger, one input end is connected in this magnetic hysteresis comparator circuit, and resets that end is connected in this logical circuit, a frequency end is connected in an oscillator and an output terminal is connected in this power switch, receive this low-voltage magnetic hysteresis signal, this reset signal and an oscillator signal, in order to export this drive signal to this power switch.

4. the switching control device with output power restriction and under-voltage protection as claimed in claim 3, wherein, this trigger can be selected from one of group's combination of D flip-flop, SR D-flip flop or JK D-flip flop.

5. the switching control device with output power restriction is used in the power supply unit, and it follows the variation of an input supply voltage, and then a drive signal of control and adjustment one power switch, it is characterized in that including:

One strangulation voltage generation unit uses the input supply voltage of a deboost source and this variation to carry out computing, in order to export a max power constraint voltage;

One Power Limitation comparer, be connected in a sense terminals of this strangulation voltage generation unit and this power supply unit, receive this a max power constraint voltage and a current sensing signal, and this max power constraint voltage and this current sensing signal compared computing, in order to export a power limit signal;

One drive signal generation unit, be connected in a feedback end of this Power Limitation comparer, this power supply unit, this sense terminals and this power switch of this power supply unit, receive this power limit signal, a voltage feedback signal and this current sensing signal, in order to export this drive signal to this power switch;

When this input supply voltage change, this max power constraint voltage can change thereupon, and then adjust this power limit signal of this Power Limitation comparer output, and the work period of this drive signal of control and this drive signal generation unit output of adjustment, to limit the primary side current of this power supply unit.

6. the switching control device with output power restriction as claimed in claim 5, also include a magnetic hysteresis comparator circuit, receive this input supply voltage and a magnetic hysteresis threshold voltage ranges value of equal proportion, after comparison operation, output or end a low-voltage magnetic hysteresis signal.

7. the switching control device with output power restriction as claimed in claim 5, wherein, this strangulation voltage generation unit connects a deboost source by a totalizer and is formed, after additive operation is carried out in this input supply voltage that this totalizer will change and this deboost source, export this max power constraint voltage.

8. the switching control device with output power restriction as claimed in claim 5, wherein, this drive signal generation unit includes:

One PWM comparer is connected to the feedback end and the sense terminals of this power supply unit, receives this voltage feedback signal and this current sensing signal, according to this voltage feedback signal of comparison operation and this current sensing signal, in order to export a modulation output signal;

One logical circuit is connected in this Power Limitation comparer and this PWM comparer, receives this power limit signal and this modulation output signal in order to export a reset signal; And

One trigger, one input end is connected in this magnetic hysteresis comparator circuit, and resets that end is connected in this logical circuit, a frequency end is connected in an oscillator and an output terminal is connected in this power switch, receive this low-voltage magnetic hysteresis signal, this reset signal and an oscillator signal, in order to export this drive signal to this power switch.

9. the switching control device with output power restriction as claimed in claim 8, wherein, this trigger can be selected from one of group's combination of D flip-flop, SR D-flip flop or JK D-flip flop.

Images