CN203014675U - Buck-boost switching power supply and controller thereof - Google Patents

Abstract

The utility model provides a buck-boost switching power supply and a controller thereof. The controller comprises: a transconductance error amplifier, wherein an input end of the transconductance error amplifier receives a sampling voltage inputted from the outside and performs transconductance type error amplification for the sampling voltage and a preset reference voltage, an output end of the transconductance error amplifier is connected with a compensation port, and the compensation port is configured to be externally connected with a compensation capacitor; a switch-on time control circuit used for determining the length of switch-on time of a power switch according to a voltage of the compensation port; a peak current detection circuit used for obtaining a value of the current flowing through the power switch within the previous power switch period according to the sampling voltage; a switch-on time limiting circuit used for determining the maximum switch-on time limit value of the power switch within the subsequent one or more power switch periods according to an output signal of the peak current detection circuit; and a logic circuit used for generating a driving signal according to the length of the switch-on time and the maximum switch-on time limit value, so as to control switch-on and switch-off of the power switch. The buck-boost switching power supply and the controller thereof provided by the utility model simplify a circuit structure, so that a smaller packaging can be adopted, thereby facilitating cost reduction.

Description

Buck Switching Power Supply and controller thereof

Technical field

The utility model relates to switch power technology, relates in particular to a kind of buck Switching Power Supply and controller thereof.

Background technology

With reference to figure 1, in the LED drive circuit of traditional buck structure, during power switch 101 conducting, input current flow through power switch 101, the second sampling resistor R _sa, inductance 103, electric current on inductance 103 increases, inductance 103 stored energys, the second sampling resistor R _saThe electric current of sample streams overpower switch 101 obtains the second sampled voltage.When power switch 101 turn-offs, electric current flow through inductance 103, the first sampling resistor R _sb, sustained diode 1 and output load capacitance Cbulk, LED lamp string, the electric current on inductance 103 reduces, inductance 103 release energy output load capacitance Cbulk, LED lamp string.The first sampling resistor R _sbThe electric current of sample streams output obtains the first sampled voltage.

After circuit was stable, the average current on output load capacitance Cbulk was zero, so flow through the first sampling resistor R _sbOn average current identical with average current on outputing to LED, sample streams is crossed the first sampling resistor R _sbOn electric current can embody the average current that outputs on LED fully.The first sampling resistor Rsb average current is flow through in control, just can accurately control output current.

Furthermore, controller 100 comprises: mutual conductance error amplifier circuit 113 connects the first sampling resistor R _sbAn end (being port CSB), the first sampled voltage and reference voltage are done the error of transconductance type and are amplified, output is connected to compensation pins COMP; Compensation pins COMP, external building-out capacitor is used for loop compensation; ON time control circuit 112 just determines the ON time length of power switch 101 according to the level of compensation pins COMP; Peak limiter circuit 114 connects the second sampling resistor R _saAn end, with the second sampled voltage and the first reference voltage relatively, during higher than the first reference voltage, produce the signal of switch-off power switch 101 when the second sampled voltage, the electric current of power switch 101 is flow through in restriction; Logical circuit 111 and drive circuit 110 connect ON time control circuit 112 and peak limiter circuit 114, the turn-on and turn-off time span of power ratio control switch 101.

The turn-off time length of power switch 101 can be determined by the system works pattern.Such as when adopting critical conduction mode, decide turn-off time length according to zero cross signal; When adopting fixed work pattern frequently, after ON time length was determined, turn-off time length was determined thereupon.

In circuit shown in Figure 1, use respectively the first sampling resistor R _sbWith the second sampling resistor R _saSampling output current and the electric current that flows through power switch 101, although it is comparatively simple that circuit is realized, but need to use two sampling resistors, need two pin CSA, CSB to be connected to peripheral circuit with Time Controller 100, be unfavorable for further reducing the pin of controller 100.

The utility model content

The technical problems to be solved in the utility model is to provide a kind of buck Switching Power Supply and controller thereof, can adopt less encapsulation thereby simplified circuit structure, is conducive to reduce costs.

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

Mutual conductance error amplifier, its input receive the sampled voltage of outside input and itself and default reference voltage are done the transconductance type error amplify, and its output connects the compensation port, and this compensation port arrangement is external building-out capacitor;

The ON time control circuit is determined the ON time length of the power switch of Switching Power Supply according to the voltage of described compensation port;

The peak current detection circuit, its input receives the sampled voltage of described outside input, obtains flow through in the cycle current value of this power switch of a upper power switch according to this sampled voltage;

The ON time limiting circuit, its input connects the output of described peak current detection circuit, determines the maximum ON time limits value of follow-up one or more power switch this power switch in the cycle according to the output signal of described peak current detection circuit;

Logical circuit connects described ON time control circuit and ON time limiting circuit, produces the driving signal according to described ON time length and maximum ON time limits value, to control the turn-on and turn-off of described power switch.

According to an embodiment of the present utility model, described mutual conductance error amplifier comprises:

The first triode, its base stage receives described sampled voltage, and its emitter connects reference current source via the first resistance;

The second triode, its base stage receives described default reference voltage, and its emitter connects described reference current source via the second resistance;

The first mirror current source, its input connects the collector electrode of described the first triode;

The second mirror current source, its input connects the collector electrode of described the second triode;

The 3rd mirror current source, its input connects the output of described the first mirror current source, and its output connects the output of described the second mirror current source.

According to an embodiment of the present utility model, described switch power controller also comprises: drive circuit, the driving signal of described logical circuit output transfers to described power switch via described drive circuit.

The utility model also provides a kind of buck Switching Power Supply, comprising:

The described switch power controller of above any one;

Power switch, its first end receives input voltage, and its control end receives the driving signal of described switch power controller output;

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

Sampling resistor, its first end connects the second end of described power switch, and its second end is connected with the mutual conductance error amplifier of described switch power controller and the input of peak current detection circuit;

Fly-wheel diode, its negative pole connects the second end of described sampling resistor;

Output capacitance, its first end connects the positive pole of described fly-wheel diode, its second end ground connection.

According to an embodiment of the present utility model, described output capacitance is configured in parallel with load.

Compared with prior art, the utlity model has following advantage:

in the buck Switching Power Supply and controller thereof of the utility model embodiment, judge the size of the electric current of the power switch of flowing through by the flow through electric current of fly-wheel diode of detection, and limit the maximum ON time limits value of the power switch of follow-up one or more switch periods according to the size of this electric current, can effectively limit the peak current of the power switch of flowing through, and saved a sampling resistor that is used for the sampled power switching current, make controller reduce by an external port (in other words, the circuit pin), thereby simplified circuit structure, be conducive to reduce costs.

Description of drawings

Fig. 1 is the circuit diagram of a kind of buck LED drive circuit in prior art;

Fig. 2 is the circuit diagram of the buck Switching Power Supply of the utility model embodiment;

Fig. 3 is the circuit structure diagram of the mutual conductance error amplifier of the utility model embodiment;

Fig. 4 is the electric current sequential chart of the buck Switching Power Supply of the utility model embodiment when working under critical conduction mode;

Fig. 5 is the electric current sequential chart of buck Switching Power Supply when startup and instantaneous short circuit of the utility model embodiment.

Embodiment

The utility model is described in further detail below in conjunction with specific embodiments and the drawings, but should not limit protection range of the present utility model with this.

With reference to figure 2, the buck Switching Power Supply of the present embodiment comprises: switch power controller 200, power switch 101, inductance L, sampling resistor R _sb, sustained diode 1, output capacitance Cbulk.

Wherein, the first end of power switch 101 receives input voltage vin, the driving signal of control end receiving key power-supply controller of electric 200 outputs of power switch 101, this drives signal via port GD output, and the second end of power switch connects first end and the sampling resistor R of inductance L _sbFirst end.The port Vs while that the second end of power switch 101 connects is as the floating ground of switch power controller 200.Power switch 101 is turn-on and turn-off under the driving signal controlling of switch power controller 200 outputs, and when power switch 101 conducting, input voltage vin is passed to the second end of power switch 101.

The first end of inductance L connects the second end of power switch 101, the second end ground connection of inductance L (being also the earth terminal of input voltage vin).When power switch 101 conducting, the inductance L stored energy; When power switch 101 turn-offed, inductance L was to the output transferring energy.

Sampling resistor R _sbFirst end connect the second end of power switch 101, sampling resistor R _sbThe second end be connected with the port CSB of switch power controller 200.Sustained diode 1 and sampling resistor R _sbSeries connection, its negative pole connects sampling resistor R _sbThe second end, its anodal first end that connects output capacitance Cbulk, the second end ground connection of output capacitance Cbulk.Output capacitance Cbulk is in parallel with load, and load can be for example LED lamp string.

Wherein, sampling resistor R _sbSample streams is through the electric current of sustained diode 1, sampling resistor R _sbThe sampled voltage at two ends transfers to switch power controller 200 via port CSB.

Switch power controller 200 comprises: mutual conductance error amplifier 113, ON time control circuit 112, peak current detection circuit 211, ON time limiting circuit 210, logical circuit 111, drive circuit 110.

Wherein, the input of mutual conductance error amplifier 113 connects sampling resistor R _sbThe second end, sampled voltage and default reference voltage are done the transconductance type error amplify, the output of mutual conductance error amplifier 113 is connected to compensation port COMP.Compensation port COMP is configured to external building-out capacitor (not shown), is used for loop compensation.

ON time control circuit 112 is just determined the ON time length of power switch 101 according to the voltage of compensation port COMP.

The input of peak current detection circuit 211 connects sampling resistor R _sbThe second end, according to sampling resistor R _sbOn sampled voltage obtain flow through in the cycle current value of power switch 101 of a power switch.

ON time limiting circuit 210, its input connects the output of peak value current detection circuit 211, determine the maximum ON time limits value of follow-up one or more power switch cycle internal power switches 101 according to the output signal of peak current detection circuit 211, excessive with the electric current of avoiding power switch 101.

Logical circuit 111 connects ON time control circuit 112 and ON time limiting circuit 210, produces the driving signal according to ON time length and maximum ON time limits value, the driving signal of output power ratio control switch 101.

Drive circuit 110 is according to the output of logical circuit 111, the time span of the turn-on and turn-off of power ratio control switch 101.

The turn-off time length of power switch 101 can be determined by the system works pattern, such as when adopting critical conduction mode, decide turn-off time length according to zero cross signal; When adopting fixed work pattern frequently, after ON time length was determined, turn-off time length was determined thereupon.

Just maximum ON time limits value is set to strengthen gradually in order to prevent from first switch periods generation overcurrent when the circuit initial start, can be arranged on circuit start beginning.

Fig. 3 shows a kind of physical circuit of mutual conductance error amplifier, input signal Va and reference voltage V ref1 is compared the output error electric current.This transconductance type amplifier comprises: the first triode Q ₁, its base stage receives input signal Va(when being applied to Switching Power Supply shown in Figure 2, and this input signal Va is namely sampled voltage), its emitter is via the first resistance R ₁Connect reference current source I ₀The second triode Q ₂, its base stage receives default reference voltage V ref1, and its emitter is via the second resistance R ₂Connect reference current source I ₀The first mirror current source 31, its input connects the first triode Q ₁Collector electrode; The second mirror current source 32, its input connects the second triode Q ₂Collector electrode; The 3rd mirror current source Q ₃, its input connects the output of the first mirror current source 31, and its output connects the output of the second mirror current source 32.

Furthermore, the first mirror current source 31 comprises MOS transistor M1 and M3, and the second mirror current source 32 comprises MOS transistor M2 and M4, and the 3rd mirror current source 33 comprises MOS transistor M5 and M6.

The image current ratio of supposing the second mirror current source 32 is K2, and the first mirror current source 31 and the 3rd the mirror current source 33 both image ratio of equivalence are K1, and the electric current I 4 of MOS transistor M4 is: I ₄=K ₂I ₂, the electric current I 6 of MOS transistor M6 is I ₆=K ₁I ₁Error current I _CompFor:

I _comp=I ₄-I ₆=K ₂·I ₂-K ₁·I ₁

Usually require K1=K2=K, R1=R2=R, I ₀Enough large, guarantee I1, I2 greater than zero, has following relation:

$I_{\mathrm{comp}}=-K\frac{V_a-V_{\mathrm{refl}}}{R}$

Be that mutual conductance Gm is:

$\mathrm{Gm}=\frac{I_{\mathrm{comp}}}{V_a-V_{\mathrm{refl}}}=-\frac{K}{R}$

After circuit is stable, flow to the current average I of compensation port COMP _CompavgBe zero, namely

I _compavg＝0

The mean value of input signal Va is identical with the mean value of reference voltage V ref1, and the mean value of input signal Va is the mean value of sampled voltage, and the mean value of input signal Va is divided by sampling resistor R _sbResistance value be exactly the mean value of output current.Just can control the size of output current fully thus, immobilize as long as control reference voltage V ref1, just can realize that the mean value of output current is constant.

Fig. 4 is the buck Switching Power Supply shown in Figure 2 electric current sequential chart of each point electric current during normal operation under being in critical conduction mode, due to the peak current Ia that flows through power switch 101 with flow through sampling resistor R _sbThe peak value of current Ib be identical, thereby might use sampling resistor R _sbOn sampled voltage come indirectly control to flow through the maximum current of power switch 101.

Fig. 5 is the electric current sequential chart of buck Switching Power Supply when startup and instantaneous short circuit shown in Figure 2.When circuit start or instantaneous short circuit, because output voltage V out is zero substantially, inductive current I _LReduce seldom.If still adopt critical conduction mode, zero cross signal needs could arrive for a long time, and switching frequency is too low like this, produces different sound, so general circuit all can limit the longest power switch turn-off time to prevent that switching frequency is too low.At this moment, when startup and instantaneous short circuit, circuit will not be in critical conduction mode, and is in the longest turn-off time control model, at this moment inductive current I _LContinuous.

In conjunction with Fig. 2 and Fig. 5, peak current detection circuit 211 detects sampled voltages,, produces the over-current detection signal and also transfers to ON time limiting circuit 210 during higher than the magnitude of voltage set when sampled voltage.In other words, when current Ib exceeds over-current detection point, produce the over-current detection signal.This over-current detection signal controlling ON time limiting circuit 210, make after the over-current detection signal having been detected, the ON time of power switch 101 drops to very low at once, and progressively increase maximum ON time limits value in the cycle at follow-up power switch, thereby make the switch conduction time progressively strengthen, effectively limited the peak current Ia that flows through power switch 101.

The utility model discloses and use a sampling resistor to realize accurately controlling output current in buck Switching Power Supply structure, take into account simultaneously the technical scheme that the electric current of power switch is flow through in restriction.At circuit start with after flowing through the overcurrent of sampling resistor, at first at once reduce the ON time of power switch, then progressively add the ON time of high power switch, in case the electric current of fluid stopping overpower switch is excessive, and describe embodiment of the present utility model and effect with reference to the accompanying drawings.

It should be understood that above-described embodiment is just to explanation of the present utility model; rather than to restriction of the present utility model; any utility model that does not exceed in the utility model connotation scope is created; include but not limited to local structure change, to the replacement of type or the model of components and parts; and the replacement of other unsubstantialities or modification, within all falling into the utility model protection range.

Claims (5)

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

Mutual conductance error amplifier, its input receive the sampled voltage of outside input and itself and default reference voltage are done the transconductance type error amplify, and its output connects the compensation port, and this compensation port arrangement is external building-out capacitor;

The ON time control circuit is determined the ON time length of the power switch of Switching Power Supply according to the voltage of described compensation port;

The peak current detection circuit, its input receives the sampled voltage of described outside input, obtains flow through in the cycle current value of this power switch of a upper power switch according to this sampled voltage;

The ON time limiting circuit, its input connects the output of described peak current detection circuit, determines the maximum ON time limits value of follow-up one or more power switch this power switch in the cycle according to the output signal of described peak current detection circuit;

Logical circuit connects described ON time control circuit and ON time limiting circuit, produces the driving signal according to described ON time length and maximum ON time limits value, to control the turn-on and turn-off of described power switch.

2. switch power controller according to claim 1, is characterized in that, described mutual conductance error amplifier comprises:

The first triode, its base stage receives described sampled voltage, and its emitter connects reference current source via the first resistance;

The second triode, its base stage receives described default reference voltage, and its emitter connects described reference current source via the second resistance;

The first mirror current source, its input connects the collector electrode of described the first triode;

The second mirror current source, its input connects the collector electrode of described the second triode;

The 3rd mirror current source, its input connects the output of described the first mirror current source, and its output connects the output of described the second mirror current source.

3. switch power controller according to claim 1, is characterized in that, also comprises:

Drive circuit, the driving signal of described logical circuit output transfers to described power switch via described drive circuit.

4. a buck Switching Power Supply, is characterized in that, comprising:

The described switch power controller of any one in claims 1 to 3;

Power switch, its first end receives input voltage, and its control end receives the driving signal of described switch power controller output;

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

Sampling resistor, its first end connects the second end of described power switch, and its second end is connected with the mutual conductance error amplifier of described switch power controller and the input of peak current detection circuit;

Fly-wheel diode, its negative pole connects the second end of described sampling resistor;

Output capacitance, its first end connects the positive pole of described fly-wheel diode, its second end ground connection.

5. buck Switching Power Supply according to claim 4, is characterized in that, described output capacitance is configured in parallel with load.

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