Switching Power Supply and LED drive circuitTechnical field
The present invention relates to a kind of power electronics field, in particular to a kind of Switching Power Supply and LED drive circuit.
Background technique
In the prior art, inductive current and output voltage are usually sampled to load supplying using Switching Power Supply, and according to phaseThe sampled signal answered is fed back, to realize the adjusting to output electric current or output voltage.
For the LED drive circuit or constant voltage source of High Power Factor (power factor, PF), prior art is such asShown in Fig. 1, control circuit is integrated in chip, is connected to high-pressure side to chip, is convenient for sampled output current.Wherein, VCC is to supplyElectric pin, COMP are compensation pin, and FB is that output voltage samples pin, and DRAIN is the drain terminal of MOS, and ISP draws for current sampleFoot, GND are grounding pin, and C1 is power supply capacitor, and C2 is compensating electric capacity.In the prior art, the compensation to COMP pin is connected toCapacitor carries out closed-loop control.Since the ground of control circuit is to float, thus VCC capacitor (power supply capacitor C1) is needed to maintain to supplyElectricity, FB divider resistance sampling and outputting voltage when main power tube turns off, resistance value are easy to be influenced by wet environment, may leadOutput open circuit is caused to protect false triggering, so as to cause LED load flashing, and peripheral components are more in the prior art.To sum up, existing skillThe system cost of the current constant control scheme of art High Power Factor is higher, and reliability is lower.
Summary of the invention
In view of this, that the object of the present invention is to provide a kind of peripheral components is few, system cost is low, the switch of high reliablity electricitySource and LED drive circuit, to solve technical problem of the existing technology.
To achieve the above object, the present invention provides a kind of Switching Power Supply, including main power tube and control circuit, the controlsCircuit processed is connect with the control terminal of the main power tube, to control the switch state of the main power tube；
The control circuit includes power supply module and overvoltage protective module, and the power supply module and overvoltage protective module connectThe hot end of input voltage is connect, the power supply module includes compression limiter, one end connection input electricity of the compression limiterThe hot end of pressure, supply voltage of the voltage of the compression limiter other end as control circuit；
The hot end of the input terminal connection input voltage of the overvoltage protective module, the overvoltage protective module sampling are defeatedEnter voltage, proportion adjustment carried out to the obtained signal of sampling, and it is compared with corresponding pressure reference signal of crossing, according to thanRelatively result judges whether that over-voltage phenomenon occurs.
Optionally, the proportion adjustment refers to is adjusted according to the duty ratio of main power tube, so that through proportion adjustmentThe output voltage of Switching Power Supply described in characterization afterwards.
Optionally, the pressure reference signal of crossing is generated by reference signal generation circuit, the reference signal generation circuit packetOvervoltage protection resistance is included, the voltage of the overvoltage protection resistance was used as pressure reference signal, flows through the over-voltage by control and protectsThe electric current of resistance is protected to determine or adjust the pressure reference signal excessively.
Optionally, the pressure reference signal of crossing is generated by reference signal generation circuit, the reference signal generation circuit packetOvervoltage protection resistance is included, the electric current of the overvoltage protection resistance is flowed through by control to determine or adjust the overvoltage protection resistanceOn voltage export and described cross pressure reference signal according to the voltage range of the overvoltage protection resistance.
Optionally, the proportion adjustment is realized by proportion adjustment circuit, and the proportion adjustment circuit includes state switching mouldThe output end of block and filter module, the state switching module is connect with the input terminal of the filter module, and the state is cutMold changing block receives the sampled signal of the input voltage and the driving signal of control circuit output, when the driving signal tableWhen levying main power tube conducting, then the state switching module exports the sampled signal of the input voltage to the filtering mouldBlock, when driving signal characterization main power tube disconnects, then the common end of the state switching module and the filter moduleGround connection, the output end voltage of the filter module characterize the output voltage of the Switching Power Supply.
Optionally, the control circuit further includes turn-on time control module, and the turn-on time control module receives electricityThe first voltage signal of flow reference signal and characterization inductive current, and simulation difference letter is generated after carrying out Error processing to the twoNumber, the analog difference signal obtains digital difference signal through analog-to-digital conversion module, and the digital difference signal is through digital compensationModule obtains digital reference signal, and the digital reference signal obtains analog reference signal, the simulation benchmark through digital-to-analogue conversionSignal is compared with ramp signal, the conductivity control signal of output characterization main power tube turn-on time.
Optionally, the Switching Power Supply is integrated circuit, and the first end of the main power tube is provided with drain terminal pin, main functionThe second end of rate pipe is provided with current sample pin, and the connecting pin of the hot end of the power supply module and input voltage is provided withStart pin, the overvoltage protection resistance is placed in outside piece, and is connect with the overvoltage protection pin of integrated circuit, the reference signalGeneration circuit is connect with the overvoltage protection pin.
Optionally, the Switching Power Supply further includes continued flow tube, one end of the continued flow tube and the first of the main power tubeEnd connection, the other end of the continued flow tube and load connect；Sampling resistor, the sampling are connected in the second end of main power tubeThe other end of resistance is grounded.
The present invention also provides a kind of LED drive circuit, including any one of the above Switching Power Supply, the rectified bridges of input powerIt powers to the Switching Power Supply, power conversion is carried out through the Switching Power Supply, to power to LED load.
Compared with prior art, the technical solution of the present invention has the advantage that of the invention directly by input voltage pairControl circuit is powered, and can save the power supply capacitor outside piece, and utilize the pass of input voltage and duty ratio and output voltageSystem is not necessarily to high pressure divider resistance, enhances the reliability of system, and can carry out accordingly to obtain the signal of characterization output voltageThe judgement of overvoltage protection, crossing pressure reference signal can be set into discrete voltage to promote anti-interference ability, in addition, the present invention also adoptsWith digital compensation, to save the compensating electric capacity outside piece, being formed by integrated circuit based on the present invention can greatly reduce outsidePeripheral device, to reduce system cost.
Detailed description of the invention
Fig. 1 is the circuit theory schematic diagram of the Switching Power Supply of the prior art；
Fig. 2 is the circuit theory schematic diagram of Switching Power Supply of the present invention；
Fig. 3 is the electrical block diagram of Switching Power Supply of the present invention；
Fig. 4 is the electrical block diagram of overvoltage protective module；
Fig. 5 is the electrical block diagram of proportion adjustment circuit；
Fig. 6 is the connection schematic diagram that the present invention is applied to BUCK-BOOST topology.
Specific embodiment
The preferred embodiment of the present invention is described in detail below in conjunction with attached drawing, but the present invention is not restricted to theseEmbodiment.The present invention covers any substitution made in the spirit and scope of the present invention, modification, equivalent method and scheme.
In order to make the public have thorough understanding to the present invention, it is described in detail in the following preferred embodiment of the present invention specificDetails, and the present invention can also be understood completely in description without these details for a person skilled in the art.
The present invention is more specifically described by way of example referring to attached drawing in the following passage.It should be noted that attached drawing is adoptedWith more simplified form and using non-accurate ratio, only to facilitate, lucidly aid in illustrating the embodiment of the present inventionPurpose.
As shown in Fig. 2, illustrating the circuit theory of Switching Power Supply of the present invention, it is based on Buck topological structure, and in switch electricityOn the basis of source, rectifier bridge is set in its front end, using LED as load, as LED drive circuit.Described this reality of Switching Power SupplyThe form that integrated circuit is used in example is applied, the first end of the main power tube is provided with drain terminal pin DRAIN, and the of main power tubeTwo ends are provided with current sample pin ISP, and the connecting pin of the hot end of the power supply module and input voltage is provided with startingPin VIN, the overvoltage protection resistance Rovp is placed in outside piece, and is connect with the overvoltage protection pin OVP of integrated circuit, with reference to letterNumber generation circuit is connect with the overvoltage protection pin.
The Switching Power Supply further includes continued flow tube D1, and one end of the continued flow tube D1 and the first end of the main power tube connectIt connects, the other end of the continued flow tube D1 and load connect；Sampling resistor Rs, the sampling are connected in the second end of main power tubeThe other end of resistance Rs is grounded, and the sampling resistor Rs is used to sample the electric current of inductance L.
As shown in figure 3, illustrating the circuit structure of Switching Power Supply of the present invention, based on the integrated circuit in Fig. 1, this attached drawing showsIt has anticipated the circuit structure of IC interior.The Switching Power Supply includes main power tube M0 and control circuit, can be integrated in coreIn piece.The control circuit is connect with the control terminal of the main power tube M0, to control the switch state of the main power tube M0.
The control circuit includes power supply module and overvoltage protective module, and the power supply module and overvoltage protective module connectConnecing the hot end of input voltage VIN, the power supply module includes compression limiter and filter unit, and the one of the compression limiterThe hot end of end connection input voltage VIN, the other end connect with the filter unit, the voltage on the filter unit are madeFor the supply voltage of power supply module output.Wherein, the filter unit is selectable unit, it is not necessary to, it is filtered when existingIn the case where wave unit, is generally realized, can integrate in chip using small capacitances.In the present embodiment, the compression limiter is adoptedIt is realized with high pressure JFET, when control circuit supply voltage is lower than the pinch-off voltage of high pressure JFET, JFET conducting；Otherwise by,Control circuit (IC) only needs minimum filter capacitor, as the filter unit, saves external power supply capacitor.
The hot end of the input terminal connection input voltage VIN of the overvoltage protective module OVP, the overvoltage protective moduleSampled input voltage VIN carries out proportion adjustment to the signal Vs1 that sampling obtains, and it is crossed pressure reference signal with correspondingVOVP_REFIt is compared, is judged whether that over-voltage phenomenon occurs according to comparison result, complete to compare in comparator COMP1, it is describedThe output end of comparator COMP1 is connect with logic unit, to trigger overvoltage protection in over-voltage.The proportion adjustment use withThe proportionality coefficient of main power tube duty ratio direct proportionality, so that Switching Power Supply described in characterization after proportion adjustmentOutput voltage.The pressure reference signal of crossing is generated by reference signal generation circuit, and the reference signal generation circuit includes settingIn the overvoltage protection resistance Rovp outside piece.
The control circuit further includes turn-on time control module, and the turn-on time control module receives current reference letterNumber VREFWith the first voltage signal V of characterization inductive currentISP, and analog difference signal is generated after carrying out Error processing to the twoVA1, the analog difference signal VA1Digital difference signal V is obtained through analog-to-digital conversion moduleD1, the digital difference signal VD1Through numberWord compensating module obtains digital reference signal VD2, the digital reference signal VD2Through digital-to-analogue conversion, analog reference signal is obtainedVCOMP, the analog reference signal VCOMPWith ramp signal VSLOPEIt is compared, output characterization main power tube M0 turn-on timeConductivity control signal Ton, the logic unit receive the conductivity control signal Ton, the output end and driver of logic unitConnection, the driver are connect with the control terminal of main power tube M0.
As shown in figure 4, illustrating a kind of circuit structure of implementation of overvoltage protective module.The overvoltage protective moduleIncluding bleeder circuit, proportion adjustment circuit and reference signal generation circuit, the branch pressure voltage sampled input voltage VIN, andTo sampled signal Vs1, the sampled signal passes through proportion adjustment circuit, using duty ratio D as proportionality coefficient, to obtain tableLevy the signal of output voltage, and itself and pressure reference signal V excessivelyOVP_REFIt is compared.The reference signal generation circuit is attached at thisImplementation in figure are as follows: described to cross pressure reference signal VOVP_REFIt is generated by reference signal generation circuit, the reference signal producesRaw circuit includes overvoltage protection resistance Rovp, and the voltage of the overvoltage protection resistance Rovp was used as pressure reference signal VOVP_REF,The electric current of the overvoltage protection resistance is flowed through by control to determine or adjust the pressure reference signal V excessivelyOVP_REF, wherein streamElectric current through the overvoltage protection resistance is Iovp.In addition, VOVP_REFIt can also be arranged to discrete voltage, will be flowed through by controlThe electric current of the overvoltage protection resistance Rovp determines or adjusts the voltage on the overvoltage protection resistance Rovp, according to the mistakeThe voltage range of protective resistance is pressed, output is described to cross pressure reference signal VOVP_REF, in specific implementation, for example, detection overvoltage protectionThe voltage of resistance Rovp determines its range by comparator, to select corresponding pressure reference signal V excessivelyOVP_REF。
As shown in figure 5, illustrating a kind of circuit structure of implementation of proportion adjustment circuit.The proportion adjustment by thanExample adjusts circuit and realizes, the proportion adjustment circuit includes state switching module and filter module, the state switching moduleOutput end is connect with the input terminal of the filter module, and the state switching module receives the sampled signal of the input voltageThe driving signal VGS of Vs1 and control circuit output, it is when driving signal VGS characterization main power tube conducting, then describedState switching module exports the sampled signal of the input voltage to the filter module, when the driving signal characterizes main functionWhen rate pipe disconnects, then the common end grounding of the state switching module and the filter module, the output end of the filter moduleVoltage characterizes the output voltage of the Switching Power Supply.The state switching module is switched over using switch T1 and T2, by drivingSignal VGS control switch T1, by control switch T2 after the inverted device of driving signal VGS.
It should be noted that " input voltage " described in the invention is the input voltage of a chip, i.e. access pin VINVoltage, by taking above-described embodiment as an example, based on BUCK topology on the basis of, then the input voltage of chip be just also BUCK topologyInput voltage.But in other topologys, it is also possible to the output voltage of topology, such as BUCK-BOOST topology, it is specific to connectRelationship is with reference to shown in Fig. 6.
Although embodiment is separately illustrated and is illustrated above, it is related to the common technology in part, in ordinary skillPersonnel apparently, can be replaced and integrate between the embodiments, be related to one of embodiment and the content recorded is not known, thenIt can refer to another embodiment on the books.
Embodiments described above does not constitute the restriction to the technical solution protection scope.It is any in above-mentioned implementationMade modifications, equivalent substitutions and improvements etc., should be included in the protection model of the technical solution within the spirit and principle of modeWithin enclosing.