CN103152955B - A kind of LED current detection and control circuit and method thereof - Google Patents
A kind of LED current detection and control circuit and method thereof Download PDFInfo
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Abstract
The invention discloses a kind of LED current detection and control circuit and controller thereof, relate to the circuit field of LED current detection and control, aim to provide a kind of based on the non-isolated of step-down (Buck) topology, the LED drive circuit of equivalent closed-loop control and controller thereof.The technology of the present invention main points comprise: power supply, energy-storage travelling wave tube, switching tube, controller; Described power supply is used for powering to the load when switching tube conducting; Described energy-storage travelling wave tube is used for when switching tube conducting, and storage of electrical energy, when switching tube turns off, discharges powering load by electric energy; Described controller is used for according to the pipe conducting of feedback signal control switch or shutoff; And when switching tube conducting, feedback signal is the signal of reaction stream overload transient current size, when switching tube turns off, feedback signal is the signal etc. of reaction stream overload equivalent current size.
Description
Technical field
The present invention relates to the circuit field of LED current detection and control, particularly relate in LED illumination the circuit of the LED current detection and control of the output high-precision current adopting buck topology (Buck).
Background technology
There is the shortcomings such as luminous efficiency is low, power consumption is large, useful life is short in conventional lighting technology, LED illumination has the advantages such as life-span long, energy-conservation, safety, environmental protection, substitutes traditional lighting rapidly.LED directly can connect the electric main of 220V unlike ordinary incandescent lamp bubble, and it needs to provide constant output current by the circuit of current detecting and control.Current precision is one of most important index of circuit of LED current detection and control, and other index mainly contains insulating reliability, volume size, power factor (PF), conversion efficiency, power source life, electromagnetic compatibility etc.
Current precision, as an important indicator of the circuit of LED current detection and control, directly determines the performance of the circuit of LED current detection and control.On market, the method for the circuit controller constant output current precision of LED current detection and control mainly contains three kinds: opened loop control, equivalent closed-loop control and closed-loop control.
Opened loop control is exactly the threshold value of the circuit controller inner setting by LED current detection and control, the peak value of direct control inductive current or valley, coordinate constant to open or the turn-off time reaches and controls the method for LED current, as the controller based on step-down (Buck) topology on market, controlled the output current of the circuit of LED current detection and control by the peak value and turn-off time controlling inductive current.The current precision of this control method is large by the impact of system delay, peripheral components deviation and controller inner parameter process deviation, output current low precision.
Equivalence closed-loop control refers to that detecting can reflect the signal exporting LED current, as inductance peak current, service time and turn-off time etc., the equivalent signal converting LED current through controller to sends into the feedback loop be made up of error amplifier and PWM pulse width modulator, and stablize this equivalent LED current signal with negative feedback, as on market based on Flyback (flyback) topology PSR (control of former limit) controller, they are also converted to equivalent LED current signal and send into feedback loop by the current peak of detecting transformer primary side and transformer discharge time, and control to export LED current by negative feedback stabilizing LED current equivalent signal.Due to the introducing of feedback loop, the current precision of this control method is only by the deviation effects of sampling and controller change-over circuit, little by ambient parameters change, thus when producing in batches current precision higher than opened loop control.
Closed-loop control refers to directly detects LED current, and current signal is sent into the feedback loop be made up of error amplifier and PWM pulse width modulator, by feedback loop stabling current signal.Because feedback loop directly controls LED current, this control method precision is high, but detect LED current information, often need extra element or allow the high-voltage signal of controller process hundreds of volt, this can the cost of remarkable increase system, as traditional flyback controller coordinates the circuit of time TL431 on limit and the LED current detection and control of optocoupler.
For the consideration to reliability, cost and volume, there is the circuit of isolation and non-isolation type two class LED current detection and control in the market.Isolated form refers to that AC electric main or DC supply input and LED load are not electrically connected, and is opened by transformer isolation.It is that the constrained input corresponding with isolated form be not by the type of drive of transformer electrical isolation that non-isolation type drives.The circuit of the LED current detection and control of isolated form is isolated by electrical equipment owing to inputting high pressure, so do not have the danger of getting an electric shock; But the circuit of isolated form LED current detection and control needs transformer, can increase cost and the volume of the circuit of current detecting and control, many LED illumination products strict to the circuit volume requirement of current detecting and control cannot use isolated form type of drive.Non-isolation type power supply does not need transformer owing to only needing inductance, thus the current detecting of the type and the circuit of control to have volume little, the feature that cost is low; But due to LED lamp insulation and the requirement of reliability, non-isolation type driving can increase the physically-isolated cost of LED lamp.The type of drive of this two type respectively has pluses and minuses, and therefore isolation exists with the scheme of non-isolated always all simultaneously.
Power factor (PF) as another important index of circuit of LED current detection and control, more and more pay attention to by market.The circuit of high power factor LED current detection and control effectively can reduce the interference to electrical network, energy-conserving and environment-protective more, especially in powerful application scenario.The mode realizing the circuit of high power factor LED current detection and control at present mainly contains twin-stage and single stage power factor correction technology.Active PFC and control LED constant current are divided into two stages for the treatment of by dual stage power factor correction technology, and integrated circuit cost is high, is applied to large-power occasions at present more.Corrected power factor and control LED constant current once complete by single stage power factor correction technology, and owing to increasing cost hardly, this technology is used widely at the circuit of LED current detection and control; But because the system bandwidth of Active PFC is very low, time simultaneously to LED constant current, export the working frequency ripple wave that LED load electric current has input AC civil power.
Whether the circuit of LED current detection and control can be divided into (inductance) continuous current mode (CCM), (inductance) discontinuous current mode (DCM) and (inductance) critical current pattern (BCM) continuously according to inductive current.Continuous current mode refers to that inductive current does not drop to zero when switching tube turns off, and when next switching tube conducting, inductive current is not increase of starting from scratch; Discontinuous current mode is contrary with continuous current mode, and before switching tube conducting, inductive current reduces to zero; Critical current pattern, between continuous current mode and discontinuous current mode, to refer to when inductive current reduces to zero actuating switch pipe at once.Continuous current mode inductance peak current and output current ripple less, can the relatively low power device of use cost and small-sized output capacitance, but continuous current mode inductance (being transformer during isolation applications) value is higher thus can increase the volume of the circuit of current detecting and control; When applying for high power factor, controller needs extra multiplier, control method more complicated.Discontinuous current mode is compared relative to continuous current mode: the shortcoming such as have the large and output current ripple of inductance (being transformer during isolation) peak current large, but value is less for discontinuous current mode inductance value (being transformer during isolation), and the control method realizing high power factor is fairly simple.The feature of critical current pattern is between continuous current mode and discontinuous current mode.
Summary of the invention
Technical problem to be solved by this invention is: for opened loop control, equivalent closed-loop control and closed-loop control Problems existing in existing LED current Test and control, provides a kind of non-isolated based on step-down (Buck) topology, the LED drive circuit of equivalent closed-loop control, method and controller thereof.
LED current Detection & Controling circuit in the present invention comprises: power supply, energy-storage travelling wave tube, switching tube, controller; Described power supply is used for powering to the load when switching tube conducting; Described energy-storage travelling wave tube is used for when switching tube conducting, and storage of electrical energy, when switching tube turns off, discharges powering load by electric energy; Described controller is used for according to clock signal and feedback signal periodic control switch pipe turn-on and turn-off; And when switching tube conducting, feedback signal is the signal of reaction stream overload transient current size, when switching tube turns off, feedback signal is the signal of reaction stream overload equivalent current size.
Wherein, described controller also flows through the signal of load peak current size for detection reaction, compared by described detection signal with first threshold, the on-off switching tube when detection signal is greater than first threshold.
Further, LED current Detection & Controling circuit also comprises the first resistance, and described controller, in switching tube conduction period, directly detects the electric current flowing through load by the first resistance, samples simultaneously and keeps flow through the first ohmically peak-current signal; At switching tube blocking interval, the discharge time of described energy-storage travelling wave tube detected by controller, and according to described discharge time and described in flow through the first ohmically peak-current signal and calculate the equivalent current flowing through load.
The invention also discloses a kind of LED current detection and control method, comprise the following steps:
According to clock signal and feedback signal periodic control switch pipe turn-on and turn-off;
When switching tube conducting, described power supply powers to the load, energy-storage travelling wave tube storage of electrical energy;
When switching tube turns off, electric energy is discharged powering load by energy-storage travelling wave tube;
And when switching tube conducting, described feedback signal is the signal of reaction stream overload transient current size; When switching tube turns off, described feedback signal is the signal of reaction stream overload equivalent current size.
Preferably, when switching tube turns off, described feedback signal is the signal of the size of reaction (flowing through peak current × 1/2 of load).
The invention also discloses a kind of controller, comprising: logical circuit, oscillator, peak value sampling circuit, equivalent discharge voltage circuit, alternative circuit, reference voltage source, error amplifier, the 3rd electric capacity and the second comparator;
Described oscillator is used for providing clock information to logical circuit, and provides sawtooth signal or triangular signal to an input of the second comparator;
The first input end of the input connection control device of described peak value sampling circuit, the output of peak value sampling circuit is connected with the input of described equivalent discharge voltage circuit, and the output of equivalent discharge voltage circuit selects input to be connected with first of described alternative circuit;
Second of described alternative circuit selects input to be connected with the first input end of controller; The output of alternative circuit is connected with error amplifier input; The control end of alternative circuit is connected with the control signal output of controller;
Another input of error amplifier connects described reference voltage source, and the output of error amplifier is connected with another input of described second comparator; The output of the second comparator exports comparative result to logical circuit; The output of described error amplifier is also by described 3rd capacity earth;
The output of described logical circuit is the control signal output of controller, and described logical circuit is used for the comparative result conducting that exports according to clock signal and the second comparator or on-off switching tube.
Above-mentioned controller is used for the LED drive power of critical current pattern.
LED drive power to be used in discontinuous current mode also need increase testing circuit discharge time on the basis of above-mentioned controller, discharge time testing circuit the second input of input connection control device, discharge time, the output of testing circuit was connected with the control end of equivalent discharge voltage circuit.
In sum, owing to have employed technique scheme, the invention has the beneficial effects as follows:
1. when switching tube is opened, the electric current of actual flow overload LED is sent into error amplifier, effectively improve the accuracy detecting when opening and flow through LED load electric current.
2. when switching tube is closed, transformer main winding peak current when controller is opened according to switching tube, by specific algorithm, when will turn off, the average eguivalent electric current of transformer main winding (or inductance) sends into closed control loop, so the electric current exported on LED is very accurate, transformer main winding (or inductance) electric current time simultaneously owing to ending without sampling switch pipe, avoids controller and adopts floating ground structure, or integrated high voltage device.The present invention is applicable to the driving power of all LED.
3. the present invention adopts the feedback system of equivalent closed-loop control, avoid the shortcoming of conventional non-isolated buck topology sampling transformer (or inductance) electric current difficulty, components and parts number is little, reduces the cost of LED drive power, is conducive to the popularization of LED illumination.
4. present invention employs step-down (Buck) circuit topology, there is very high power factor value in the LED drive power realizing one pole power factor correction.
5. the present invention is applicable to the discontinuous mode of non-isolated or the LED drive power of critical conduction mode, has the LED drive power of input High Power Factor.
Accompanying drawing explanation
Examples of the present invention will be described by way of reference to the accompanying drawings, wherein:
Fig. 1 is the applications circuit of LED current detection and control of the present invention;
Fig. 2 is the internal module figure of middle controller of the present invention;
Fig. 3 is peak value sampling oscillogram of the present invention;
Fig. 4 is detection waveform figure discharge time of the present invention;
Fig. 5 is that point voltage oscillogram is put in equivalence of the present invention;
Fig. 6 is the concrete built-up circuit figure of one of peak value sampling circuit in example of the present invention;
Fig. 7 is the concrete built-up circuit figure of one of equivalent discharge circuit in example of the present invention;
Fig. 8 is the concrete built-up circuit figure of one of alternative circuit in example of the present invention.
Embodiment
All features disclosed in this specification, or the step in disclosed all methods or process, except mutually exclusive feature and/or step, all can combine by any way.
Arbitrary feature disclosed in this specification (comprising any accessory claim, summary and accompanying drawing), unless specifically stated otherwise, all can be replaced by other equivalences or the alternative features with similar object.That is, unless specifically stated otherwise, each feature is an example in a series of equivalence or similar characteristics.
As Fig. 1, an embodiment of the LED current detection and control circuit in the present invention is such: comprise controller 101, switching tube 102, transformer 103, sampling resistor 104, fly-wheel diode 105, input bridge rectifier 107, resistance 111 and 112, output filter capacitor 115.Load in the present embodiment is LED string 106.
The two ends that described rectifier diode 107 inputs connect AC civil power, the anode of a termination LED string 106 of output, the earth potential N02 of another termination controller 101 respectively; In another embodiment, can also comprise electric capacity 108, described electric capacity 108 and the output-parallel of bridge rectifier, meet N01 and N02 respectively.The effect of described bridge rectifier 107 and electric capacity 108 is that AC power is converted to DC power supply.
The negative electrode of described LED string 106 meets one end N05 of transformer 103, and output capacitance 115 is in parallel with LED string 106; The anode N01 of described fly-wheel diode 105 1 termination LED string, one end N09 of another termination transformer 103.Described electric capacity 115 is filter capacitors, and this electric capacity can reduce the current ripples above LED load.The effect of described fly-wheel diode 105 is, when switching tube 102 is opened, described diode by, power supply is stoped to flow directly into switching tube 102 from N01, when switching tube 102 is closed, described diode is opened, and transformer 103 is powered by diode 105 pairs of LED load.
The drain electrode of described switching tube 102 connects with one end N09 of transformer 103, and the source electrode of switching tube connects one end N04 of sampling resistor 104, and the grid of switching tube 102 meets the output N07 of controller; Described sampling resistor 104 1 termination N04, other end earthing potential N02.
One end N06 of described divider resistance 112 1 termination transformer 103, another termination N08, described divider resistance 111 1 termination N08, other end earthing potential N02.
The main winding two ends of described transformer 103 meet N05 and N09 respectively, and auxiliary winding meets N06 and earth potential N02 respectively, and wherein the N05 of main winding and the N06 of auxiliary winding is Same Name of Ends.
The voltage signal that described controller 101 produces on described sampling resistor 104 for detecting the electric current that flows through LED string 106, transformer 103 main winding and switching tube 102, and detect the waveform that the voltage N08 of winding current potential N06 after resistance 111 and 112 dividing potential drop assisted by transformer 103, by conducting or the cut-off of the Inner Control Loop control switch pipe 102 of controller 101 simultaneously; The effect of described divider resistance 111 and 112 is, by the auxiliary winding voltage signal N06 dividing potential drop of transformer 103, is converted to the voltage signal N08 that controller 101 can process.
The effect of described transformer 103 main winding is when switching tube 102 is opened, while powering to LED load 106, convert electric energy to Magnetic Energy Storage in transformer 103, convert the magnetic energy be stored in transformer main winding 103 to electric energy when switching tube is closed and power to LED load; Described transformer 103 assists winding to embody the voltage and current direction of the corresponding Same Name of Ends in former limit, when switching tube is opened, N06 accordingly current potential N02 is negative pressure, when switch OFF, when transformer 103 main winding is in discharge condition, N06 accordingly current potential N02 is positive voltage (this voltage proportional is in the forward conduction voltage of LED string), powers to controller chip, simultaneously when transformer 103 main winding current reduces to zero, N06 voltage starts to decline.And then controller just can learn the information of transformer 103 discharge time by the voltage waveform of detecting N08 point.
In an instantiation, described switching tube 102 is power NMOS tube, when drive singal N07 is high, is opened by switching tube 102; When drive singal N07 is low, switching tube 102 is closed.
The effect of described resistance 104 is, when switching tube 102 is opened, detect the electric current flowing through switching tube 102 and transformer 103, then the voltage signal that resistance 104 produces is sent in controller 101, when the moment that switching tube 102 is closed, the peak voltage signal flowing through the electric current of LED load is sent in controller 101.
During switching tube 102 conducting, the voltage signal that controller 101 flows through the transient current size of load according to reflection produces pulse-width signal (pwm signal) control switch pipe, when switching tube 102 turns off, the voltage signal that controller 101 flows through average current (i.e. equivalent current) size of load according to reflection produces pulse-width signal control switch pipe, thus the electric current of LED load is flow through in accurate adjustment.In an instantiation, the voltage signal that the average current size of load is flow through in reflection is the half that moment that switching tube 102 closes flows through the peak voltage signal of the electric current of LED load.
In another embodiment, controller is also by feedback loop stable LED load electric current, and the maximum current of switching tube 102 and transformer 103 is flow through in restriction.
In another instantiation, in circuit, be also provided with electric capacity 113.The output N10 of described electric capacity 113, one termination controller, other end earthing potential N02.Described electric capacity 113 is a loop compensation electric capacity, can be positioned at the outside of controller 101, also can be integrated in the inside of controller 101.When its effect is the LED drive power work ensureing to be made up of the circuit of described LED current detection and control, the stability of feedback control loop.
In another embodiment, resistance 110, electric capacity 109 and diode 114 can also be set up.The output N01 of described resistance 110 1 termination bridge rectifier 107, the power supply N03 of another termination controller 101; Described electric capacity 109 1 termination N03, other end earth point position N02; The auxiliary winding N06 of described diode 114 1 termination transformer 103, the power supply N03 of another termination controller 101.The effect of described resistance 110 is, before controller 101 control switch pipe 102 is opened and turned off, provides starting current to controller 101; The effect of described diode 114 is, the auxiliary winding of transformer 103, between switching tube 102 off period, charges to the first electric capacity 109, is the power supply of controller 101; When switching tube is opened, stop and maintain electric capacity 109 by transformer 103 auxiliary discharge; The effect of described electric capacity 109 is, when the auxiliary winding of transformer 103 powers to controller 101, for controller 101 provides maintenance electric current.
Described signal N01 represents the positive terminal of input power;
Described signal N02 represents the negative phase end of input power, both ground reference of controller 101;
Described signal N03 represents the power supply of controller 101;
Described signal N04 is a voltage signal, this voltage is using N02 as earth signal, when switching tube 102 is opened, this voltage represents the size of current flowing through switching tube 102 and transformer 103 main winding, when switching tube 102 is closed, the peak voltage signal flowing through the electric current of LED load is sent in controller 101.
Described signal N06, when switching tube is opened, N06 accordingly current potential N02 is negative pressure, when switch OFF N06 accordingly current potential N02 be positive voltage (this voltage proportional is in the forward conduction voltage of LED string), to chip power supply, simultaneously when transformer 103 main winding current reduces to zero, N06 voltage starts to decline, for controller 101 provides transformer to put the information of 103 electricity times.
Described signal N07 represents the gate drive signal of switching tube 102, the unlatching of this Signal-controlled switch pipe 102 and shutoff, and this signal is the output signal of controller 101.
Described voltage division signal N08 is that after the auxiliary winding voltage signal N06 dividing potential drop by transformer 103, be converted to the voltage signal that controller 101 can process, this signal is the input signal of controller 101.
As Fig. 2, a physical circuit of described controller 101, comprise peak value sampling circuit 201, discharge time testing circuit 202, reference voltage source 203, oscillator 204, equivalent discharge voltage circuit 205, alternative circuit 206, error amplifier 207, comparator 209 and logical circuit 210.
Described peak value sampling circuit 201 has an input, an output and a control end, one end N04 of input termination sampling resistor 104, export the input N53 of termination equivalence discharge voltage circuit 205, control end is that switching tube 102 opens the control signal N07 turned off; The effect of described peak value sampling circuit 201 is, at the end of switching tube 102 is opened, keeps the ceiling voltage signal on one end N04 of sampling resistor 104, as the input of equivalent discharge voltage circuit 205.
Equivalence discharge voltage circuit 205 has an input, an output and a control end, the output N53 of peak value sampling circuit 201 described in input termination, export an input N54 of alternative circuit 206 described in termination, the output N52 of described control termination testing circuit discharge time 202; The effect of described equivalent discharge voltage circuit 205 is, upon discharging, testing circuit 202 exports N52 when being logic height (transformer 103 main winding current is in discharge condition), the output of equivalence discharge voltage circuit 205 is the half of the output N53 magnitude of voltage of described peak value sampling circuit 201, when upon discharging, the output of testing circuit 202 is logic low (transformer 103 main winding current is in charged state or electric discharge done state), the output earth potential N02 of equivalent discharge voltage circuit 205.
Discharge time, testing circuit 202 had an input, an output, and input termination transformer 103 is assisted the voltage division signal N08 of winding, exported the control end N52 of termination equivalence discharge voltage circuit 205; Described discharge time, the effect of testing circuit 202 was, by the high level time of detectable voltage signals N08, obtain the discharge time signal N52 of the main winding of transformer 103, described N52 is a logical signal, removes the output N54 controlling equivalent discharge voltage circuit 205.
Described alternative circuit 206 has two and selects input, a control end and an output, input is selected to be connected respectively one end N04 of described sampling resistor and the output N54 of equivalent discharge voltage circuit 205 for two, described control end is connected with the grid N07 of switching tube 102, and described output is connected with an input N55 of error amplifier 207.When switching tube is opened, the signal that described alternative circuit 206 sends into error amplifier 207 is one end N04 of sampling resistor 104; When switching tube 102 is closed, the output N54 of described equivalent discharge voltage circuit 205 sends in error amplifier 207 by alternative circuit 206.
The voltage signal that described error amplifier 207 exports for the reference voltage source 203 that received and alternative circuit 206 is converted into current signal and exports; Building-out capacitor 113 described in Fig. 1 is connected with the output N10 of error amplifier, changes voltage signal into for the current signal exported by error amplifier 207; The effect of error amplifier 207 is, LED current information (one end N04 of sampling resistor 104) when switching tube 102 is opened or switching tube 102 turns off time LED current information (the output N54 of equivalent discharge voltage circuit 205) and reference signal N51 compare, and obtain error amplification signal N10, go unlatching and the shutoff of control switch pipe 102, thus stablize the output current of LED load 106.
An input of comparator 209 is connected with the output N10 of error amplifier 207, another input is connected with an output N58 of oscillator 204, and comparator 209 is for comparing the sawtooth signal N58 on another input of voltage signal and its that building-out capacitor 113 produces; The effect of comparator 209 is service times of determine switch pipe 102, both sawtooth signal N58 is compared with the output signal N10 of error amplifier, and the output signal of comparator 209 is sent to the service time of by-pass cock pipe 102 in logical circuit 210.
In another embodiment, controller 101 also comprises comparator 208.An input of described comparator 208 connects one end N04 of described sampling resistor 104, and another input receives the reference voltage N50 that reference voltage source 203 exports, and the control signal that comparator 208 exports sends into logical circuit 210; The effect of comparator 208 is maximum currents that switching tube 102 and transformer 103 main winding are flow through in restriction, when the current equivalence signal N04 flowing through switching tube 102 and transformer 103 main winding exceedes the output voltage N50 of reference voltage source 203, comparator 208 is by logical circuit 210 on-off switching tube 102, and the lowest high-current value of switching tube 102 and transformer 103 main winding is flow through in restriction.
The signal that described logical circuit 210 turns on and off for generation of control switch pipe 102.
The effect of described reference voltage source 203 is, produce accurate reference voltage N50 and N51, wherein N51 is using the input voltage signal as error amplifier 207, and N50 is as the input voltage signal of comparator 208.
The effect of described oscillator 204 is, clocking N57, sends into logical circuit 210 and controls the open-minded of described switching tube 102; Produce sawtooth signal or triangular signal N58 simultaneously, compare with the output signal N10 of error amplifier 207 and send into logical circuit 210, the service time of control switch pipe 102, in one embodiment, when sawtooth signal N58 is greater than the output signal N10 of error amplifier 207, the control signal N10 on-off switching tube that comparator 209 exports.
The effect of described logical circuit 210 is, receives output signal N56, the output signal N59 of comparator 209 of comparator 208, the turning on and off of the output signal N57 control switch pipe 102 of oscillator 204.
Inside described controller 101: N53 signal is an analog voltage signal, when switching tube 102 is opened, the voltage signal of one end N04 that this voltage is sampling resistor described in Fig. 1 104, when switching tube 102 is closed, this signal keeps the voltage peak of described voltage signal N04;
N52 signal is a logical signal, this signal 202 to be produced, as the control signal of equivalent discharge voltage circuit 205, when the main winding of transformer 103 is in discharge condition by testing circuit discharge time, N52 is logic high, and other times N52 is logic low;
N54 is an analog voltage signal, and when N52 is logic height electricity, when both described transformer 103 main winding is in discharge condition, N54 exports the half of analog voltage signal N53, and other times N54 exports earth potential N02;
N55 is an analog voltage signal, this signal is the output of alternative circuit 206, and send into the signal of error amplifier 207, when switching tube 102 is closed, the magnitude of voltage of described N55 is the output N54 of equivalent discharge voltage circuit, when switching tube is opened, the magnitude of voltage of described N55 is the magnitude of voltage of one end N04 of sampling resistor 104;
N51 signal is a reference voltage signal, and this signal is produced by voltage-reference 203, as an input signal of error amplifier 207, determines the current value of LED load 106;
N50 signal is a reference voltage signal, and this signal is produced by voltage-reference 203, as an input signal of comparator 208, determines the maximum current flowing through transformer 103 and switching tube 102;
N59 signal is a digital logic signal, and this signal is produced by comparator 209, is produced the service time of N07 Signal-controlled switch pipe 102 by logical circuit 210;
N56 signal is a digital logic signal, and this signal is produced by comparator 208, is produced the shutoff of N07 Signal-controlled switch pipe 102 by logical circuit 210;
N58 is a sawtooth signal, and this signal is produced by oscillator 204, delivers in comparator 209 and compares with the output signal N10 of error amplifier 207;
N57 signal is a digital logic signal, and this signal is produced by oscillator 204, is produced the start-up time of N07 Signal-controlled switch pipe 102 by logical circuit 210;
N10 is an analog voltage signal, the size of this voltage signal has been reacted the size of input voltage N01 and has flow through the size of LED load electric current, the electric current that this voltage signal is produced by error amplifier 207 carries out charging and discharging decision to electric capacity 113, this voltage is sent into comparator 209 and is compared with sawtooth signal N58, produces signal N59.
With reference to Fig. 3, it is peak value sampling circuit 201 operation principle schematic diagram.
First width figure indication transformer 103 main winding current, when switching tube is opened, electric current rises with fixed slope, and when switching tube is closed, electric current reduces with fixed slope.
Second width figure represents the voltage signal N04 on sampling resistor 104, and when switching tube is opened, N04 voltage is the electric current of transformer 103 main winding and the product of sampling resistor 104 resistance value, and when switching tube turns off, the magnitude of voltage of N04 is ground reference N02.
3rd width figure represents the output signal N53 of peak value sampling circuit 201, and when switching tube is opened, the voltage signal of N53 and N04 is the same, and when switching tube turns off, described N53 exports the peak voltage for N04.
With reference to Fig. 4, it is testing circuit 202 schematic diagram discharge time.
First width figure and the second width figure represents the voltage signal of indication transformer 103 main winding current and sampling resistor 104 respectively, consistent with described in Fig. 3.
3rd width figure represents that controller 101 inputs the signal of N08, described N08 is the voltage division signal that winding N06 assisted by transformer 103, when switching tube is opened, N08 accordingly current potential N02 is that negative pressure is (if controller has clamp circuit, N08 is the voltage of clamp circuit setting), when switch OFF, when transformer 103 main winding is in discharge condition, N08 accordingly current potential N02 is positive voltage (this voltage proportional is in the forward conduction voltage of LED load), simultaneously when transformer 103 main winding current reduces to zero, N08 voltage starts to decline, the information of the discharge time of transformer main winding 103 is provided for controller 101.
4th width figure represents the output signal N52 of testing circuit 202 discharge time, when described N08 is positive voltage, and N52 output logic high level, when described N08 is negative pressure, N52 output logic low level.
With reference to Fig. 5, it is the operation principle schematic diagram of equivalent discharge voltage circuit 205.
First width figure and the second width figure represents the voltage signal N04 of the resistance 104 and output signal N53 of peak value sampling circuit 201 respectively, consistent with described in Fig. 3.
3rd width figure represents the output signal N52 of testing circuit 202 discharge time, consistent with described in Fig. 4.
4th width figure represents the output voltage signal N54 of equivalent discharge voltage 205, when described N52 is logic high, both when the main winding of transformer 103 is in discharge condition, N54 is the half that peak value sampling circuit 201 outputs signal N53 magnitude of voltage, when described N52 is logic low, N54 is ground reference N02.
Fig. 6 is the concrete built-up circuit figure of one of peak value sampling circuit 201; Comprise resistance 301, electric capacity 302 and 306, inverter 303, two or door 304, NMOS tube 305, operational amplifier 308, diode 307.
Described resistance 301 and electric capacity 302 form a delay circuit, with inverter 303, two or door 304 together with, constitute an edge sense circuit, both when the grid control signal N07 of described switching tube 102 is from (switching tube 102 becomes opening from off state) during low uprising, two or the output one of door 304 determined by resistance 301 and electric capacity 302 to control the logical signal N61 of high level pulsewidth NMOS tube 305 and open.
The effect of described operational amplifier 308, diode 307 and electric capacity 306 is, when the voltage N04 of sampling resistor 104 rises, makes N53 follow N04 and rises together; When described voltage N04 will for after reference location be N02, due to the barrier effect of diode 307, electric capacity 306 keeps the crest voltage of N04.
The effect of described NMOS tube 305 is, when switching tube 102 becomes unlatching from shutoff, is discharged by electric capacity 306, makes described voltage signal N53 can the voltage N04 of following sampling resistance 104 again.
N61 signal is a logical signal, when switching tube 102 becomes unlatching from shutoff, produces one is determined high level pulsewidth pulsewidth logic by resistance 301 and electric capacity 302, controls NMOS tube and discharges to electric capacity 306.
Fig. 7 is the concrete built-up circuit figure of one of equivalent discharge circuit 205; Comprise operational amplifier 400, resistance 401 and 402, NMOS tube 403 and 405, inverter 404.
The effect of operational amplifier 400 is, makes voltage signal N63 equal the output voltage signal N53 of described peak value sampling circuit 201.
The effect of resistance 401 and 402 is, by voltage signal N63 dividing potential drop, makes voltage signal N62 equal the half of described voltage signal N63.
The effect of NMOS tube 403 is, when described discharge time testing circuit 202 output logic signal N52 be logic high time, both when transformer 103 main winding is in discharge condition, N62 signal is delivered to the output N54 of equivalent discharge circuit 205, when described N52 is logic low, both, when transformer 103 main winding is not in discharge condition, the output N54 of equivalent discharge circuit is delivered to reference to earth potential N02.
The effect of inverter 404 is, described control signal N52 is reverse, controls unlatching and the shutoff of nmos pass transistor 405.
N63 is an analog voltage signal, equals the magnitude of voltage of input signal N53; N62 is an analog voltage signal, and the magnitude of voltage of described N62 is the half of the output N63 of operational amplifier 400.
With reference to Fig. 8, a kind of execution mode of alternative circuit 206 is: comprise reverser 410 and 411, NMOS tube 412 and NMOS tube 413.
The input of described reverser 410 connects N07, and the output of described reverser 410 connects the input of reverser 411 and the grid of NMOS tube 412, and the output of described reverser 411 connects the grid of NMOS tube 413.
The drain electrode of described NMOS tube 412 connects input signal N54, and the substrate connection control device of described NMOS tube 412 is with reference to ground N02, and the source electrode of described NMOS tube 412 connects source electrode and the output signal N55 of NMOS tube 413.
The drain electrode of described NMOS tube 413 connects input signal N04, and the substrate connection control device of described NMOS tube 413 is with reference to ground N02, and the source electrode of described NMOS tube 413 connects source class and the output signal N55 of NMOS tube 412.
The present invention is not limited to aforesaid embodiment.The present invention expands to any new feature of disclosing in this manual or any combination newly, and the step of the arbitrary new method disclosed or process or any combination newly.
Claims (7)
1. a LED current detection and control circuit, is characterized in that, comprising: power supply, energy-storage travelling wave tube, switching tube, controller and the first resistance;
Described power supply is used for powering to the load when switching tube conducting;
Described energy-storage travelling wave tube is used for when switching tube conducting, and storage of electrical energy, when switching tube turns off, discharges powering load by electric energy;
Described controller is used for: when switching tube conducting according to the comparative result of the signal of sawtooth signal or triangular signal and reaction stream overload transient current size and the periodic conducting of clock signal control switch pipe and shutoff; When switching tube turns off according to the comparative result of the signal of sawtooth signal or triangular signal and reaction stream overload equivalent current size and the periodic conducting of clock signal control switch pipe and shutoff;
Described controller, in switching tube conduction period, directly detects the electric current flowing through load by the first resistance, sample simultaneously and keep flow through the first ohmically peak-current signal; At switching tube blocking interval, the discharge time of described energy-storage travelling wave tube detected by controller, and according to described discharge time and described in flow through the first ohmically peak-current signal and calculate the equivalent current flowing through load.
2. circuit according to claim 1, is characterized in that, also comprises diode, the 3rd resistance, the 4th resistance and the second electric capacity; Described energy-storage travelling wave tube is transformer;
The positive pole of described power supply is for connecting the anode of load, and the first end of transformer main winding is for connecting the negative electrode of load, and described second Capacitance parallel connection is at load two ends; The anode of the drain electrode of described switching tube, the second end of transformer main winding and diode links together; The negative electrode of diode is connected with the positive pole of power supply; The source electrode of switching tube is connected with the first end of the first resistance, and the grid of switching tube is connected with the control signal output of controller, the second end ground connection of the first resistance; The first end of the first resistance is connected with the first input end of controller;
The first end of the auxiliary winding of described transformer connects the first end of the 4th resistance, and the second end of the 4th resistance connects the first end of the 3rd resistance, the second end ground connection of the 3rd resistance; Second end ground connection of the auxiliary winding of described transformer; Second input of the public connecting end connection control device of the 3rd resistance and the 4th resistance.
3. circuit according to claim 2, it is characterized in that, the power input of described controller is connected with the positive pole of power supply by the second resistance, the power input of controller is connected with the first end of transformer auxiliary winding by the second diode, and the power input of controller is by the first capacity earth;
Wherein, the negative electrode of the second diode is connected with the power input of controller, and anode is connected with the first end of transformer auxiliary winding.
4. the circuit according to Claims 2 or 3, it is characterized in that, described controller comprises: logical circuit, oscillator, peak value sampling circuit, equivalent discharge voltage circuit, alternative circuit, reference voltage source, error amplifier, the 3rd electric capacity and the second comparator;
Described oscillator is used for providing clock signal to logical circuit, and provides sawtooth signal or triangular signal to an input of the second comparator;
The input of described peak value sampling circuit connects the first input end of described controller, the output of peak value sampling circuit is connected with the input of described equivalent discharge voltage circuit, and the output of equivalent discharge voltage circuit selects input to be connected with first of described alternative circuit;
Second of described alternative circuit selects input to be connected with the first input end of described controller; The output of alternative circuit is connected with error amplifier input; The control end of alternative circuit is connected with the control signal output of described controller;
Another input of error amplifier connects described reference voltage source, and the output of error amplifier is connected with another input of described second comparator; The output of the second comparator exports comparative result to logical circuit; The output of described error amplifier is also by described 3rd capacity earth;
The output of described logical circuit is the control signal output of described controller, and described logical circuit is used for the comparative result conducting that exports according to clock signal and the second comparator or on-off switching tube.
5. circuit according to claim 4, it is characterized in that, described controller also comprises testing circuit discharge time, and discharge time, the input of testing circuit connected the second input of described controller, and discharge time, the output of testing circuit was connected with the control end of equivalent discharge voltage circuit.
6. a LED current detection and control method, is characterized in that, comprises the following steps:
When switching tube conducting: power supply powers to the load, energy-storage travelling wave tube storage of electrical energy; And according to the comparative result of the signal of sawtooth signal or triangular signal and reaction stream overload transient current size and the periodic conducting of clock signal control switch pipe and shutoff;
When switching tube turns off: electric energy is discharged powering load by energy-storage travelling wave tube; And according to the comparative result of the signal of sawtooth signal or triangular signal and reaction stream overload equivalent current size and the periodic conducting of clock signal control switch pipe and shutoff;
Described controller, in switching tube conduction period, directly detects the electric current flowing through load by the first resistance, sample simultaneously and keep flow through the first ohmically peak-current signal; At switching tube blocking interval, the discharge time of described energy-storage travelling wave tube detected by controller, and according to described discharge time and described in flow through the first ohmically peak-current signal and calculate the equivalent current flowing through load.
7. method according to claim 6, is characterized in that, when switching tube turns off, the signal of described reaction stream overload equivalent current size is the signal of peak current 1/2nd size of reaction stream overload.
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| CN103324228A (en) * | 2013-07-08 | 2013-09-25 | 郑儒富 | Constant-voltage driver and control method thereof |
| CN103389767A (en) * | 2013-07-08 | 2013-11-13 | 郑儒富 | Constant current driver and control method thereof |
| CN107367700B (en) * | 2016-05-11 | 2020-06-05 | 美芯晟科技（北京）有限公司 | Detection circuit and detection method of LED switching power supply |
| CN108880302A (en) * | 2018-05-08 | 2018-11-23 | 电子科技大学 | A kind of ideal diode bridge rectifier and its control method |
| CN109526105B (en) * | 2018-12-18 | 2024-02-02 | 深圳茂硕电子科技有限公司 | LED driving power supply for isolating and switching off output voltage |
| CN111682762B (en) * | 2020-06-28 | 2021-07-20 | 阳光电源股份有限公司 | Sampling circuit, sampling control method and power supply equipment |
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| CN102523650A (en) * | 2011-12-02 | 2012-06-27 | 赵修平 | Light-emitting diode (LED) current detection and control circuit |
| CN102735906A (en) * | 2012-07-05 | 2012-10-17 | 矽力杰半导体技术(杭州)有限公司 | Inductive current detecting circuit and LED (light emitting diode) driving circuit using inductive current detecting circuit |
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| US20090058323A1 (en) * | 2007-08-30 | 2009-03-05 | Ta-Yung Yang | Flyback LED drive circuit with constant current regulation |
| JP2011035112A (en) * | 2009-07-31 | 2011-02-17 | Sanyo Electric Co Ltd | Light-emitting diode driver circuit and lighting apparatus |
| CN102076138B (en) * | 2009-11-25 | 2013-06-12 | 北京交通大学 | Electric supply input LED (Light Emitting Diode) constant current driver |
| US20130049621A1 (en) * | 2010-03-04 | 2013-02-28 | O2Micro Inc. | Circuits and methods for driving light sources |
| CN102223741B (en) * | 2010-04-14 | 2015-01-21 | 日隆电子股份有限公司 | Control circuit and control method applied in light-emitting diode (LED) driver |
| CN102469650B (en) * | 2010-11-08 | 2014-07-23 | 登丰微电子股份有限公司 | Conversion control circuit |
| EP2501028B1 (en) * | 2011-03-16 | 2018-09-26 | HiDeep Inc. | Power supply for controlling current |
| JP5576818B2 (en) * | 2011-03-22 | 2014-08-20 | パナソニック株式会社 | Lighting device and lighting fixture using the same |
| JP5576819B2 (en) * | 2011-03-23 | 2014-08-20 | パナソニック株式会社 | Lighting device and lighting apparatus |
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| CN102523650A (en) * | 2011-12-02 | 2012-06-27 | 赵修平 | Light-emitting diode (LED) current detection and control circuit |
| CN102735906A (en) * | 2012-07-05 | 2012-10-17 | 矽力杰半导体技术(杭州)有限公司 | Inductive current detecting circuit and LED (light emitting diode) driving circuit using inductive current detecting circuit |
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Effective date of registration: 20210220 Address after: 518101 Tangtou community, Shiyan street, Bao'an District, Shenzhen City, Guangdong Province Patentee after: SHENZHEN LINGQI SEMICONDUCTOR Co.,Ltd. Address before: 610041 no.21-1, Ximianqiao Hengjie, Wuhou District, Chengdu, Sichuan Province Patentee before: Jiang Xiaobo |
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