CN102263501A - Control method and controller - Google Patents

Abstract

The controller and the control method are suitable for a power supply. The power supply includes a switch and an inductive element connected in series. The switch is turned on to increase the inductor current of the inductor element. The inductive current flowing through the inductive element is detected to generate a current detection signal. The current detection signal and an adjustment signal are summed to generate a summed signal. The summed signal is compared to a peak limit. The switch is closed when the summed signal approximately exceeds the peak limit. An on-time or duty cycle of the switch is detected, and the adjustment signal is updated accordingly.

Description

Control method and controller

Technical field

The invention relates to a kind of switch type power supplying device (Switched-mode power supply, overcurrent protection SMPS) (over current protection, OCP) method and relevant device.

Background technology

Power supply unit is a kind of electric power controller, is used for conversion electric power, to provide power supply to electronic installation or element.For instance, Fig. 1 is a known power supply unit 60, has flyback framework (flyback topology).Bridge rectifier 62 rectifications AC power V _AC, input power supply V is provided _INTo transformer 64.During switch 72 short circuits (close), the first side winding L of transformer 64 _PEnergy storage; During open circuit (open), the secondary side winding L of transformer 64 _SBy rectifier 66 release can to load capacitance (loadcapacitor) 69 to set up out-put supply V _OUTError amplifier (error amplifier) EA is out-put supply V relatively _OUTVoltage and target voltage V _Target, and produce compensating signal V _COMController 74 is according to compensating signal V _COMAnd current detection signal V _CS, with control signal V _GATEControl switch 72.Current detection signal V _CSReaction stream is through first side winding L _PInductive current.

The controller 74 of Fig. 2 illustration Fig. 1.Clock generator 76 periodically makes logical block 79 open switch 72.Comparator 77 and 78 is current limit detection signal V roughly _CSPeak value roughly be no more than a peak value limit value V _CS-LIMITWith compensating signal V _COMVoltage in smaller value.Overcurrent protection is reached by comparator 78 and logical block 79, wishes to make current detection signal V _CSPeak value can not surpass peak value limit value V _CS-LIMIT

But comparator 78 is found current detection signal V _CSUp to peak value limit value V _CS-LIMIT, arranged segment signal time of delay to real off switch 72.This segment signal is in time of delay, current detection signal V _CSCan raise constantly.Therefore, current detection signal V _CSTend to be higher than peak value limit value V _CS-LIMIT, and the voltage Δ V that exceeds can be along with input power supply V _INVoltage different and different results arranged.Such difference for instance, can make power supply unit 60 at difference input power supply V _INDuring voltage, have different out-put supply V _OUTPeak power output.This is beyond affordability for system designer.

Summary of the invention

The embodiment of the invention provides a kind of control method, is applicable to a power supply unit.This power supply unit includes a switch and an inductance element of polyphone.This switch is unlocked, and increases the inductive current of this inductance element.The inductive current of this inductance element of flowing through is detected, to produce a current detection signal.Add up this current detection signal and and adjust signal, produce one and add resultant signal.Relatively this adds a resultant signal and a peak value limit value.When this adds resultant signal approximately above this peak value limit value, close this switch.Detect an opening time or the responsibility cycle of this switch, and upgrade this adjustment signal according to this.

The embodiment of the invention provides a kind of controller, is applicable to a power supply unit.This power supply unit includes a switch and an inductance element of polyphone.This controller includes a logic processing device, a comparator and a current generator.This logic processing device is in order to open this switch.When the voltage of a test side exceeded a peak value limit value, this comparator was closed this switch.According to the opening time or the responsibility cycle of this switch, this current generator produces one and adjusts electric current, flow to an end of this switch by this test side.When this opening time or responsibility cycle increase, this is adjusted electric current and reduces.This adjusts electric current when this opening time or responsibility cycle, is approximately certain value.

Description of drawings

Fig. 1 is a known power supply unit.

Fig. 2 is the controller among Fig. 1.

Fig. 3 is according to a power supply unit of the invention process.

Fig. 4 is the controller among Fig. 3.

Fig. 5 has shown limits value I _CS-LIMITWith opening time T _ONRelation, and two different input power supply V _INUnder inductive current I _P

Fig. 6 illustration the current generator among Fig. 4.

[main element label declaration]

60、90	Power supply unit
		62	Bridge rectifier
64	Transformer
		66	Rectifier
69	Load capacitance
		72	Switch
74、80	Controller
		76	Clock generator
77、78	Comparator
		79	Logical block
82	Current generator
		84	Current mirror
86、88	Constant current source
		89	Electric capacity
C ：LIMIT	Curve
		CS	Detect resistance
EA	Error amplifier
		FCS	Adjust resistance
GM	The transduction comparator
		I CS-LIMIT	Limits value
I CS-OUT	Adjust electric current
		I CTL	Electric current
I SET、I EXP	Decide electric current
		I P	Inductive current
L P	First side winding
		L S	Secondary side winding
S 1、S 2	Lines
		SS	The test side
T ON	Opening time
		V AC	AC power
V COM	Compensating signal
		V CS	Current detection signal
V CS-LIMIT	The peak value limit value
		V CTL	Control voltage
V FCS	Adjust signal
		V GATE	Control signal
V IN	The input power supply
		V OUT	Out-put supply
V REF	Default value
		V Target	Target voltage

Embodiment

Fig. 3 is according to a power supply unit 90 of the invention process, the controller 80 among Fig. 4 illustration Fig. 3.Among Fig. 3 and Fig. 4, represent same or analogous element, device or signal, be known technology, do not add tired stating at this with label identical among Fig. 1,2 of known technology.Fig. 3 and 4 only is an embodiment, implements the present invention and must use same or analogous element, device or signal in Fig. 1 and 2.Interest field of the present invention should be read as restriction with claim.

Different with Fig. 1, among Fig. 3, be connected with between the test side SS of controller 80 and the detection resistance CS and adjust resistance FCS.Different with Fig. 2, among Fig. 4, controller 80 has current generator 82, and the adjustment electric current I is provided _CS-OUT,, flow through and adjust resistance FCS and detect resistance CS by the test side.The controller 80 of Fig. 4 can be implemented with an integrated circuit, and it is connected with adjustment resistance FCS's, can pass through an IC bond (pin).

By control signal V _GATE, the opening time of current generator 82 sense switches 72 (ON time) T _ONOr responsibility cycle (Duty cycle) D, adjust electric current I to upgrade _CS-OUT, wherein responsibility cycle D is opening time T _ONDivided by whole switch periods.Adjust electric current I _CS-OUTValue, when switch 72 was opened, big appointment maintained a constant definite value.Can provide a feedback mechanism in the current generator 82, electric current I is once adjusted in a switch periods change _CS-OUT, make opening time T _ONOr responsibility cycle D and adjustment electric current I _CS-OUTRoughly be inverse ratio.For instance, 72 opening time of the switch in switch periods T _ONOr responsibility cycle D just reduces the adjustment electric current I of next switch periods when becoming big _CS-OUT

Upgrade and adjust electric current I _CS-OUTUpgraded the first side winding L that flows through in the equivalence _PInductive current I _PLimits value I _CS-LIMIT, it is for triggering the inductive current value of OCP.Please consult Fig. 3 and Fig. 4 together.The condition that comparator 78 is triggered is that the voltage of test side approximates peak value limit value V greatly _CS-LIMIT, shown in following formula (1):

V _CS-LIMIT＝V _FCS+V _CS ....(1)

Wherein, V _FCSWith V _CSBeing respectively and adjusting resistance FCS and the cross-pressure that detects resistance CS, also is respectively an adjustment signal and a current detection signal.The voltage of test side approximately is exactly to adjust signal V _FCSAnd current detection signal V _CSVoltage add up.Suppose the resistance value R that adjusts resistance FCS _FCSMuch larger than the resistance value R that detects resistance CS _CS, then formula (1) can approximately be put in order and be:

V _CS-LIMIT＝I _CS-OUT*R _FCS+I _CS-LIMIT*R _CS

I _CS-LIMIT＝(V _CS-LIMIT-I _CS-OUT*R _FCS)/R _CS ...(2)

Suppose the adjustment electric current I _CS-OUTWith opening time T _ONInverse relation be

I _CS-OUT*T _ON＝K ...(3)

Wherein K is a constant.Then formula (2) can become

I _CS-LIMIT＝(V _CS-LIMIT/R _CS)-K*R _FCS/(R _CS*T _ON)...(4)

In the formula (4), K*R _FCS/ (R _CS* T _ON) can be considered as the amount of deleting, in order to reduce peak value limit value V _CS-LIMITCorresponding primary current limit value (V _CS-LIMIT/ R _CS), begin to limit inductive current I ahead of time _PCurve C among Fig. 5 _{: LIMIT}Illustration limits value I in the formula (4) _CS-LIMITWith opening time T _ONRelation.Lines S among Fig. 5 ₁With S ₂Two different input power supply V have also been shown _INUnder inductive current I _P, lines S wherein ₁Pairing input power supply V _INThan higher, so opening time T _ONShorter, limits value I _CS-LIMITBe smaller I _P1As shown in Figure 5, as long as suitably choose R _FCS, might be able to allow inductive current I _PPeak value, not along with input power supply V _INChange, be fixed on about primary current limit value V _CS-LIMIT/ R _CS, solved the problem that caused signal delay time, in addition, more than in the formula of being derived and the explanation, all can replace opening time T by responsibility cycle D _ON

Fig. 6 illustration the current generator 82 among Fig. 4.Constant current source 86 provides decides electric current I _SETTo electric capacity 89 chargings; Constant current source 88 provides decides electric current I _EXP, only at control signal V _GATEBe " 1 " in logic, when just switch 72 is opened, to electric capacity 89 discharges.When switch 72 is opened, control voltage V _CTL, it has determined electric current I _CTLWith decide electric current I _EXP, be maintained a definite value haply.84 of current mirrors (currentmirror) make the adjustment electric current I _CS-OUTApproximately with electric current I _CTLEqual proportion.By circuit analysis as can be known, Fig. 6 has realized following formula (5).

I _SET*T _CYCLE＝I _EXP*T _ON?...(5)

Wherein, T _CYCLESwitch periods for switch 72.For instance, after a switch periods, if voltage V greater than the right side, is controlled in the left side of formula (5) _CTLJust can rise, and then increase electric current I _CTLAnd decide electric current I _EXPControl voltage V _CTLTo deciding electric current I _EXPSuch feedback path can allow the left and right sides of formula (5) be tending towards about equally.Formula (5) can be derived the adjustment electric current I _CS-OUTWith opening time T _ONRelation, shown in following formula (6):

I _CS-OUT＝K ₁*I _CTL＝K ₂*I _EXP＝K ₃*I _SET*T _CYCLE/T _ON ...(6)

If represent that with responsibility cycle D formula (6) can be rewritten as:

I _CS-OUT＝K ₃*I _SET/D ...(7)

Wherein, decide electric current I _SETWith T _CYCLEWhen being definite value, significantly, adjust electric current I _CS-OUTJust with opening time T _ONOr responsibility cycle D approximately is inversely proportional to.

Adjust electric current I _CS-OUTShould be to take place, when just power supply unit is in heavy duty, just need to produce at OCP.So transduction comparator GM can be used as a control unit, by detecting compensating signal V _COM, whether decision produces the adjustment electric current I _CS-OUTIn Fig. 6, as compensating signal V _CIMBe lower than default value V _REFThe time, can be considered as underloading or no-load, adjust electric current I _CS-OUTWill stop, becoming 0, so limits value I _CS-LIMITJust can not be subjected to opening time T _ONOr the variation of responsibility cycle D and influencing.

Among the embodiment of Fig. 4, by triggering restriction inductive current I ahead of time _P, attempt solving signal delay time the problem that may cause.System manufacturer can determine the effect that it may reach by selecting a suitable external adjustment resistance FCS.

Though the present invention is an example with the SMPS of a flyback framework, the present invention also goes for similarly SMPS such as step-down power converter, booster power transducer.

The above only is preferred embodiment of the present invention, and all equalizations of being done according to claim scope of the present invention change and modify, and all should belong to covering scope of the present invention.

Claims (10)

1. A control method, applicable to a power supply, comprising a switch and an inductance element connected in series, the method comprising: Turn on the switch to increase the inductive current of the inductive element; detecting the inductive current flowing through the inductive element to generate a current detection signal; summing the current detection signal and an adjustment signal to generate a sum signal; comparing the summed signal with a peak limit value, and closing the switch when the summed signal approximately exceeds the peak limit value; and An on-time or duty cycle of the switch is detected, and the adjustment signal is updated accordingly. 2. The control method according to claim 1, wherein the power supply further comprises a detection resistor connected between the switch and a power line, and an adjustment resistor having a first end connected to the switch and the Sense resistor, the control method includes: providing an adjustment current to flow through the adjustment resistor, and the adjustment current approximately remains constant when the switch is turned on; closing the switch when the voltage at a second terminal of the adjusting resistor is higher than the peak limit value; and The adjustment current is changed according to the turn-on time or duty cycle. 3. The control method according to claim 2, further comprising: As the on-time or duty cycle increases, the regulation current is decreased. 4. The control method according to claim 1, further comprising: charging a capacitor with a first constant current; discharging the capacitor with a second constant current during the turn-on time or duty cycle; and The second constant current and the adjustment current are adjusted according to the voltage of the capacitor. 5. The control method according to claim 1, further comprising: providing a compensation signal reflecting an output voltage of the power supply; and When the compensation signal is lower than a default value, the adjustment signal is stopped. 6. A controller, suitable for a power supply, comprising a switch and an inductance element connected in series, comprising: a logic processing device for opening the switch; A comparator, when the voltage of a detection terminal is higher than a peak limit value, the switch is turned off; and A current generator generates a regulation current according to a turn-on time or duty cycle of the switch, flows through the detection terminal to one end of the switch, and when the turn-on time or duty cycle increases, the regulation current decreases; Wherein, the adjustment current is about a certain value during the turn-on time or duty cycle. 7. The controller according to claim 6, the power supply further comprising: a sense resistor connected between the switch and a power line; and An adjustment resistor is connected between the detection resistor and the detection terminal. 8. The controller of claim 6, wherein the current generator provides a feedback mechanism such that the regulated current is approximately inversely proportional to the on-time or duty cycle. 9. The controller according to claim 6, wherein the current generator comprises: A control unit, when a compensation signal is lower than a default value, stop the adjustment current; Wherein, the compensation signal reflects an output voltage of the power supply. 10. The controller according to claim 6, wherein the current generator comprises: A first constant current source charges a capacitor; a second constant current source to discharge the capacitor during the turn-on; and a feedback path, changing the current of the second constant current source according to the voltage of the capacitor; Wherein, the adjusted current is proportional to the current of the second constant current source.

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