CN104270873A - LED driver, control method and control circuit - Google Patents
LED driver, control method and control circuit Download PDFInfo
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- CN104270873A CN104270873A CN201410584124.9A CN201410584124A CN104270873A CN 104270873 A CN104270873 A CN 104270873A CN 201410584124 A CN201410584124 A CN 201410584124A CN 104270873 A CN104270873 A CN 104270873A
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
- Y02B20/40—Control techniques providing energy savings, e.g. smart controller or presence detection
Abstract
The invention discloses an LED driver, a control method and a control circuit. When a dimming signal is indicated to be of a lowest value, the output voltage of the power level circuit of the LED driver is controlled to be smaller than a first threshold namely the lowest voltage which can power on LED load, and a dimming effect can be normally achieved; meanwhile, the output voltage is controlled to be greater than a second threshold, thereby ensuring that an auxiliary winding can provide sufficient voltage for supplying power to a dimmer normally. Therefore, when the dimmer directly or indirectly obtains power from the auxiliary winding, the problem that the dimmer cannot obtain power to work normally after a lowest dimming value of the dimmer is achieved is solved.
Description
Technical field
The present invention relates to power electronic technology, be specifically related to a kind of LED driver, control method and control circuit.
Background technology
Light-emitting diode (Light-Emitting Diode is called for short LED) illumination becomes the mainstream technology of lighting source just day by day.Dimmable LED device can change output current according to dim signal usually, thus realizes dimming function.If dim signal, by independently dimmer generation, needs for dimmer powered, the supply power voltage that dimmer needs is generally 3V-5V.
In the prior art, the supply power mode of dimmer mainly contains two kinds:
The first supply power mode is from voltage bus power taking, and this mode is from an independently high voltage source power taking, and need corresponding voltage conversion device or stable-pressure device to make supply power voltage meet the needs of dimmer, this can increase manufacturing cost.And because the voltage of voltage bus is higher, therefore in transfer process, loss is larger.
The second supply power mode is directly or indirectly for dimmer powered by auxiliary winding.Particularly, can directly from the high-pressure side power taking of auxiliary winding, also can from the supply node power taking of auxiliary winding power circuitry, auxiliary winding power circuitry can utilize the voltage of auxiliary winding indirectly for control circuit is powered.Although the second supply power mode has the advantage that loss is low and cost is low, the voltage that auxiliary winding provides is relevant to the output voltage of power stage circuit, when dim signal instruction minimum (usually corresponding zero or reach minimum to make LED load brightness close to the output current of zero) time, control circuit can quit work, make the power switch of power stage circuit keep turning off, cause output voltage to decline to a great extent thus.The decline of output voltage can cause auxiliary winding to be supplied to the undertension of dimmer, and when re-starting light modulation, dimmer cannot normally work.
Summary of the invention
In view of this, the invention provides LED driver, control method and control circuit, during to solve dimmer directly or indirectly from auxiliary winding power taking, dimmer in light modulation to the problem that cannot obtain power supply after minimum.
First aspect, provides a kind of LED driver, comprising:
Power stage circuit;
Auxiliary winding, is coupled with the energy-storage travelling wave tube of described power stage circuit;
Dimmer, is directly or indirectly powered by described auxiliary winding, exports dim signal;
Control circuit, in the flrst mode, controls described power stage circuit according to dim signal and exports the drive current corresponding with dim signal, under the second mode, controls the output of described power stage circuit and is less than first threshold and is greater than Second Threshold output voltage;
Wherein, described control circuit works in the second pattern when described dim signal instruction is minimum, otherwise, work in first mode; Described first threshold is the minimum output voltage value that LED load can be made to light; The output voltage values of described Second Threshold corresponding to the minimum supply power voltage of dimmer.
Preferably, described control circuit comprises:
Constant-current control circuit, generate switch controlling signal according to described dim signal, described switch controlling signal exports described drive current for controlling described power stage circuit;
Pressure limiting circuit, for working under the second mode, when power stage circuit output voltage is greater than protection threshold value, export pressure limiting enable signal, described protection threshold value is less than described first threshold;
Logical circuit, when receiving described pressure limiting enable signal, does not export described switch controlling signal, when not receiving described pressure limiting enable signal, exports described switch controlling signal.
Preferably, described control circuit comprises:
Constant-current control circuit, generates the first switch controlling signal according to described dim signal, and described first switch controlling signal exports described drive current for controlling described power stage circuit;
Constant-voltage control circuit, generates second switch control signal, and described second switch control signal is less than first threshold for controlling the output of described power stage circuit and is greater than the output voltage of Second Threshold;
Logical circuit, exports described first switch controlling signal to power stage circuit in the flrst mode, exports described second switch control signal under the second mode to power stage circuit.
Preferably, described control circuit comprises:
Constant-current control circuit, in the flrst mode, generates the first switch controlling signal according to dim signal, under the second mode, quits work, and described first switch controlling signal exports described drive current for controlling described power stage circuit;
Constant-voltage control circuit, does not work in the flrst mode, under the second mode, generates second switch control signal, and described second switch control signal is less than first threshold for controlling the output of described power stage circuit and is greater than the output voltage of Second Threshold;
Logical circuit, exports described first switch controlling signal when described first switch controlling signal being detected, otherwise exports described second switch control signal.
Second aspect, provides a kind of LED driver control method, and described LED driver comprises power stage circuit, auxiliary winding and dimmer; Wherein, auxiliary winding is coupled with the energy-storage travelling wave tube of described power stage circuit; Described dimmer is directly or indirectly powered by described auxiliary winding, exports dim signal;
Described method comprises:
First mode is worked in when described dim signal does not indicate minimum, otherwise, work in the second pattern;
In the flrst mode, control described power stage circuit according to described dim signal and export the drive current corresponding with dim signal;
Under the second mode, control the output of described power stage circuit be less than first threshold and be greater than the output voltage of Second Threshold;
Wherein, described first threshold is the minimum output voltage value that LED load is lighted; The output voltage values of described Second Threshold corresponding to the minimum supply power voltage of dimmer.
Preferably, under the second mode described, control described power stage circuit and export and be less than first threshold and the output voltage being greater than Second Threshold comprises:
Under the second mode, the not output switch control signal when power stage circuit output voltage is greater than the described first threshold of protection;
Wherein, described protection threshold value is less than described first threshold.
Preferably, under the second mode described, control described power stage circuit and export and be less than first threshold and the output voltage being greater than Second Threshold comprises:
Under the second mode, the switch controlling signal generated by constant-voltage control circuit controls described power stage circuit, makes described output voltage be less than first threshold and be greater than Second Threshold.
The third aspect, provides a kind of control circuit, and for controlling LED driver, described control circuit comprises:
Constant-current control circuit, generate switch controlling signal according to dim signal, described switch controlling signal exports described drive current for controlling described power stage circuit;
Pressure limiting circuit, for working under the second mode, when power stage circuit output voltage is greater than protection threshold value, export pressure limiting enable signal, described protection threshold value is less than described first threshold;
Logical circuit, when receiving described pressure limiting enable signal, does not export described switch controlling signal, when not receiving described pressure limiting enable signal, exports described switch controlling signal;
Wherein, described control circuit works in the second pattern when described dim signal instruction is minimum, otherwise, work in first mode; Described first threshold is the minimum voltage that LED load can be made to light; The output voltage values of described Second Threshold corresponding to the minimum supply power voltage of dimmer.
Fourth aspect, provides a kind of control circuit, and for controlling LED driver, described control circuit comprises:
Constant-current control circuit, generates the first switch controlling signal according to dim signal, and described first switch controlling signal exports the drive current corresponding with dim signal for controlling described power stage circuit;
Constant-voltage control circuit, generates second switch control signal, and described second switch control signal is less than first threshold for controlling the output of described power stage circuit and is greater than the output voltage of Second Threshold;
Logical circuit, exports described first switch controlling signal in the flrst mode, exports described second switch control signal under the second mode;
Wherein, described control circuit works in the second pattern when described dim signal instruction is minimum, otherwise, work in first mode; Described first threshold is the minimum voltage that LED load can be made to light; The output voltage values of described Second Threshold corresponding to the minimum supply power voltage of dimmer.
5th aspect, provides a kind of control circuit, and for controlling LED driver, described control circuit comprises:
Constant-current control circuit, in the flrst mode, generates the first switch controlling signal according to dim signal, quits work under the second mode, and described first switch controlling signal exports the drive current corresponding with dim signal for controlling described power stage circuit;
Constant-voltage control circuit, quits work in the flrst mode, under the second mode, generates second switch control signal, and described second switch control signal is less than first threshold for controlling the output of described power stage circuit and is greater than the output voltage of Second Threshold;
Logical circuit, exports described first switch controlling signal when described first switch controlling signal being detected, otherwise exports described second switch control signal;
Wherein, described control circuit works in the second pattern when described dim signal instruction is minimum, otherwise, work in first mode; Described first threshold is the minimum voltage that LED load can be made to light; The output voltage values of described Second Threshold corresponding to the minimum supply power voltage of dimmer.
By when described dim signal is designated as minimum, control to make the output voltage of the power stage circuit of LED driver be less than first threshold, also, the minimum voltage that LED load can be lighted, makes dimming effect normally to realize; Meanwhile, by controlling to make output voltage be greater than Second Threshold, can ensure that auxiliary winding provides enough voltage to be dimmer normal power supply.Thus, when can solve dimmer directly or indirectly from auxiliary winding power taking, dimmer cannot obtain the normal problem worked of power supply in light modulation after minimum.
Accompanying drawing explanation
By referring to the description of accompanying drawing to the embodiment of the present invention, above-mentioned and other objects, features and advantages of the present invention will be more clear, in the accompanying drawings:
Fig. 1 is the circuit diagram of the LED driver of the embodiment of the present invention;
Fig. 2 is the circuit block diagram of the control circuit of one embodiment of the invention;
Fig. 3 is the circuit block diagram of the control circuit of another embodiment of the present invention;
Fig. 4 is the circuit block diagram of the control circuit of another embodiment of the present invention;
Fig. 5 is the flow chart of the control method of the LED driver of the embodiment of the present invention.
Embodiment
Based on embodiment, present invention is described below, but the present invention is not restricted to these embodiments.In hereafter details of the present invention being described, detailedly describe some specific detail sections.Do not have the description of these detail sections can understand the present invention completely for a person skilled in the art yet.In order to avoid obscuring essence of the present invention, known method, process, flow process, element and circuit do not describe in detail.
In addition, it should be understood by one skilled in the art that the accompanying drawing provided at this is all for illustrative purposes, and accompanying drawing is not necessarily drawn in proportion.
Meanwhile, should be appreciated that in the following description, " circuit " refers to the galvanic circle connected and composed by electrical connection or electromagnetism by least one element or electronic circuit.When " being connected to " another element when claiming element or circuit or claiming element/circuit " to be connected to " between two nodes, it can be directly couple or be connected to another element or can there is intermediary element, the connection between element can be physically, in logic or its combine.On the contrary, " be directly coupled to " when claiming element or " being directly connected to " another element time, mean that both do not exist intermediary element.
Unless the context clearly requires otherwise, similar words such as " comprising ", " comprising " otherwise in whole specification and claims should be interpreted as the implication that comprises instead of exclusive or exhaustive implication; That is, be the implication of " including but not limited to ".
In describing the invention, it is to be appreciated that term " first ", " second " etc. are only for describing object, and instruction or hint relative importance can not be interpreted as.In addition, in describing the invention, except as otherwise noted, the implication of " multiple " is two or more.
Fig. 1 is the circuit diagram of the LED drive circuit of the embodiment of the present invention.As shown in Figure 1, the LED driver 10 of the present embodiment comprises power stage circuit 11, auxiliary winding 12, dimmer 13 and control circuit 14.
In FIG, power stage circuit 11 is sampled reverse exciting topological, and it comprises former limit winding NP, vice-side winding NS, power switch Q1, rectifier diode D1 and filter capacitor C
o.
Winding NP one end, former limit connects voltage bus and receives input supply voltage v
s, the other end is connected with power switch Q1.Voltage bus is to former limit winding NP input DC power voltage v
s.Former limit winding NP and vice-side winding NS forms the energy-storage travelling wave tube of power stage circuit 11.
In FIG, power switch Q1 adopts metal oxide semiconductor transistor (MOSFET), certainly, it will be understood by those skilled in the art that power switch Q1 also can adopt other controllable semiconductor switch.
Rectifier diode D1 is connected between one end of vice-side winding NS and the output o of power stage circuit 11, filter capacitor C
obe connected between the output o of power stage circuit 11 and the reference edge of secondary circuit.The other end of vice-side winding NS is also connected with the reference edge of secondary circuit.
Can control by the turn-on and turn-off controlling power switch Q1 the electric current flowing through former limit winding, it transfers energy to vice-side winding NS, makes power stage circuit export satisfactory voltage or electric current.
Easy understand, that the power stage circuit of the LED drive circuit of the present embodiment also can adopt other type, that auxiliary winding can be coupled DC-DC converter topology, such as, positive activation type topology.
In FIG, the driving port DRV of control circuit 14, to the grid output switch control signal of power switch Q1, controls the turn-on and turn-off of power switch Q1.Between driving port DRV and the grid of power switch Q1, can connect as required and drive resistance R5.
Meanwhile, between the source electrode that sampling resistor R6 is connected to power switch Q1 and earth terminal, its both end voltage is as current feedback signal v
ibe input to the current feedback port ISEN of control circuit 14.Easy understand, in order to the relevant information making control circuit 14 obtain output current, also can adopt other circuit element and circuit structure to realize the feedback of output current relevant information.
Energy-storage travelling wave tube (being also the transformer that former limit winding NP and the vice-side winding NS is formed) electromagnetic coupled of auxiliary winding 12 and power stage circuit 11.Thus, auxiliary winding 12 can produce induced current, exports the voltage relevant to output voltage.
Based on this characteristic, auxiliary winding 12 may be used for for control circuit provides feedback voltage v
fB.As shown in Figure 1, auxiliary winding 12 first end contact resistance bleeder circuit, the second end is connected to earth terminal.In resistor voltage divider circuit, between the first end that resistance R3 and resistance R4 is connected in series in auxiliary winding 12 and earth terminal, the voltage of both connected ends is as feedback voltage v
fBbe input to the Voltage Feedback port VSEN of control circuit.
Meanwhile, auxiliary winding 12 can also be control circuit or other circuit supply in conjunction with peripheral circuit.As shown in Figure 1, starting resistance R1 is connected between voltage bus and feeder ear s, and start-up capacitance C1 is connected between feeder ear s and earth terminal, between the first end that diode D2 and resistance R2 is connected in series in auxiliary winding 12 and feeder ear s.Feeder ear s is connected with the power supply port VIN of control circuit, is its power supply.
Starting resistance R1 charged to start-up capacitance C1 at the circuit initial stage of opening, and made start-up capacitance C1 both end voltage increase, for control circuit 14 is powered.After circuit start, the induced current flowing through auxiliary winding 12 forms pressure drop after diode D2 rectification on resistance R2, makes feeder ear s have a voltage and can be control circuit or other circuit supply.
The power supply port of dimmer 13 is connected or is connected with feeder ear s with the first end of auxiliary winding 12 (connection line is represented by dashed line in FIG).Thus, auxiliary winding 12 can directly or indirectly be powered for dimmer 13.Dimmer 13 exports dim signal v to the light modulation port PWM of control circuit 14
dim.In the present embodiment, dim signal v
dimcan be a pulse-width signal, it be input to the dim signal input port PWM of control circuit 14.Control circuit 14 is according to dim signal v
dimaverage voltage or duty ratio regulate drive current i
o, make drive circuit i
owith dim signal v
dimcorresponding.At dim signal v
dimaverage voltage larger time, control circuit 14 controls power stage circuit 11 and exports larger drive current, makes LED load brightness comparatively large, at dim signal v
dimaverage voltage less time, control circuit 14 controls power stage circuit 11 and exports less drive current, makes LED load brightness less, thus, realizes light modulation.
Certainly, one of ordinary skill in the art will readily recognize that dim signal v
dimalso other form can be adopted.
In the present embodiment, control circuit 14 can at two MODE of operation.At dim signal v
dimwhen indicating minimum (also, instruction zero or close to zero output current to make LED load brightness reach minimum time, now, dim signal v
dimaverage voltage can between 0-5V), control circuit 14 works in the second pattern, otherwise, work in first mode.In the flrst mode, control circuit 14 is according to dim signal v
dimcontrol power stage circuit 11 to export and dim signal v
dimcorresponding drive current i
o; Under the second mode, control circuit 14 controls power stage circuit 11 and makes output voltage v
obe less than first threshold and be greater than Second Threshold.
Wherein, described first threshold is the minimum voltage value that LED load is lighted, and described Second Threshold is make auxiliary winding to be normally the minimum voltage of dimmer powered, also, and the output voltage values corresponding to the minimum supply power voltage of dimmer.
By when described dim signal is designated as minimum, control to make the output voltage of the power stage circuit of LED driver be less than first threshold, also, the minimum voltage that LED load can be lighted, makes dimming effect normally to realize; Meanwhile, by controlling to make output voltage be greater than Second Threshold, can ensure that auxiliary winding provides enough voltage to be dimmer normal power supply.Thus, when can solve dimmer directly or indirectly from auxiliary winding power taking, dimmer cannot obtain the normal problem worked of power supply in light modulation after minimum.
Fig. 2 is the circuit block diagram of the control circuit of one embodiment of the invention.As shown in Figure 2, in this embodiment, control circuit 14 comprises constant-current control circuit 141, pressure limiting circuit 142 and logical circuit 143.Easy understand, in order to make control circuit normally work, control circuit 14 also can comprise other circuit unit (not shown)s such as the power supply circuits being connected to power supply port usually.
Constant-current control circuit 141 is connected with light modulation port PWM, Voltage Feedback port VSEN and current feedback port ISEN, input dim signal v
dim, voltage feedback signal v
fBwith current feedback signal v
i, it is according to dim signal v
dimand feedback voltage v
fBwith current feedback signal v
igenerate switch controlling signal.Switch controlling signal exports the drive current corresponding with dim signal for controlling described power stage circuit.Wherein, dim signal v
dimfor knowing the drive current of corresponding desired output for constant-current control circuit 141.Feedback voltage v
fBwith current feedback signal v
ifor obtaining the state of power stage circuit for constant-current control circuit 141, keep the stable of drive current.
Pressure limiting circuit 142 is connected with light modulation port PWM and Voltage Feedback port VSEN, input dim signal v
dimwith voltage feedback signal v
fB.Pressure limiting circuit 142 for working under the second mode, at power stage circuit 11 output voltage v
owhen being greater than protection threshold value, export pressure limiting enable signal, start pressure-limiting function.Pressure limiting circuit 142 is according to dim signal v
dimdetermine operating state.At dim signal v
dimwhen not indicating minimum, pressure limiting circuit 142 does not work.At dim signal v
dimwhen indicating minimum, pressure limiting circuit 142 starts and works.Wherein, protection threshold value be less than first threshold, also, under the second mode, output voltage do not rise to LED load can be made to light time, pressure limiting circuit 142 will export pressure limiting enable signal.
Logical circuit 143, when receiving described pressure limiting enable signal, does not export described switch controlling signal, when not receiving pressure limiting enable signal, exports described switch controlling signal.
Control circuit shown in Fig. 2 can be applicable in the LED driver shown in Fig. 1.At dim signal v
dimwhen instruction is not minimum, pressure limiting circuit 142 does not work.Now, the normal output switch control signal of logical circuit 143, controls power stage circuit 11 and exports and dim signal v
dimcorresponding drive current, makes LED load normal luminous.
At dim signal v
dimwhen indicating minimum, pressure limiting circuit 142 works in the second pattern, and its protection threshold value is less than Second Threshold.Now; output voltage is also greater than Second Threshold usually; also be; be greater than protection threshold value, therefore, pressure limiting circuit 142 exports pressure limiting enable signal; make logical circuit 143 not output switch control signal; power switch Q1 is turned off, and LED load stops luminous (also namely modulated light is extremely minimum), and control circuit 14 quits work simultaneously.Output voltage continuous decrease, after output voltage drops to and is less than protection threshold value, pressure limiting circuit 142 stops exporting pressure limiting enable signal.Meanwhile, voltage bus makes the voltage rise of feeder ear s to start-up capacitance C1 charging by starting resistance R1, forms and control circuit 14 can be resumed work after delay a period of time.After control circuit 14 is resumed work, logical circuit output switch control signal makes the output voltage of power stage circuit 11 rise.Be raised on the output voltage be greater than protection threshold value time, pressure limiting circuit 142 again output protection is enable, and control circuit 14 is quit work.
Thus, at dim signal v
dimremain instruction minimum period, the process that control circuit 14 repeats above-mentioned startup, stops, restarting, the output voltage of power stage circuit 11 is made to be less than first threshold, thus can ensure that LED load is not lit during this period, output voltage can keep again being greater than Second Threshold simultaneously, thus auxiliary winding 12 can provide voltage directly or indirectly to power for dimmer 13, avoid dimmer cisco unity malfunction.
Fig. 3 is the circuit block diagram of the control circuit of another embodiment of the present invention.As shown in Figure 3, control circuit 14 comprises constant-current control circuit 141 ', constant-voltage control circuit 142 ' and logical circuit 143 '.
Constant-current control circuit 141 ' is connected with light modulation port PWM, Voltage Feedback port VSEN and current feedback port ISEN, input dim signal v
dim, voltage feedback signal v
fBwith current feedback signal v
i, it is according to dim signal and feedback voltage v
fBwith current feedback signal v
igenerate the first switch controlling signal, the first switch controlling signal exports dim signal v for controlling power stage circuit 11
dimcorresponding drive current.Wherein, feedback voltage v
fBwith current feedback signal v
ifor obtaining the state of power stage circuit for constant-current control circuit 141 ', keep the stable of drive current.
Constant-voltage control circuit 142 ' is connected with Voltage Feedback port VSEN, input voltage feedback signal v
fB, generate second switch control signal, second switch control signal is less than first threshold for controlling power stage circuit 11 output and is greater than the output voltage of Second Threshold.
Logical circuit 143 ' is connected with light modulation port PWM, input dim signal v
dim, also input the first switch controlling signal and second switch control signal simultaneously.Logical circuit 143 ' can work in different patterns.At dim signal v
dimwhen not indicating minimum, logical circuit 143 ' works in first mode, exports described first switch controlling signal to power stage circuit 11; At dim signal v
dimwhen indicating minimum, under logical circuit 143 ' works in the second pattern, export described second switch control signal to power stage circuit 11.
Thus, at dim signal v
dimremain instruction minimum period, control circuit 14 does not quit work, but switches to Isobarically Control pattern, controls power stage circuit 11 output and is less than first threshold and is greater than the output voltage of Second Threshold.Ensure that LED load can not obtain on the one hand luminous higher than the voltage of first threshold, ensure that it is dimmer powered that auxiliary winding 12 can provide voltage directly or indirectly, avoids dimmer cisco unity malfunction on the other hand.
Fig. 4 is the circuit block diagram of the control circuit of another embodiment of the present invention.As shown in Figure 4, control circuit 14 comprises constant-current control circuit 141 ", constant-voltage control circuit 142 " and logical circuit 143 ".
Constant-current control circuit 141 " be connected with light modulation port PWM, Voltage Feedback port VSEN and current feedback port ISEN, input dim signal v
dim, voltage feedback signal v
fBwith current feedback signal v
i.At dim signal v
dimwhen not indicating minimum, constant-current control circuit 141 " according to dim signal and feedback voltage v
fBwith current feedback signal v
igenerate the first switch controlling signal, the first switch controlling signal exports drive current corresponding to dim signal for controlling described power stage circuit; At dim signal v
dimwhen indicating minimum, constant-current control circuit 141 " quit work, do not export the first switch controlling signal.
Constant-voltage control circuit 142 " be connected with light modulation port PWM and Voltage Feedback port VSEN, input dim signal v
dimwith voltage feedback signal v
fB.In the present embodiment, constant-voltage control circuit 142 " according to dim signal v
dimwork in different operating states.At dim signal v
dimwhen not indicating minimum, constant-voltage control circuit 142 " quit work; At dim signal v
dimwhen indicating minimum, constant-voltage control circuit 142 " generate second switch control signal, second switch control signal is less than first threshold for controlling power stage circuit 11 output and is greater than the output voltage of Second Threshold.
Logical circuit 143 " the first switch controlling signal is exported when the first switch controlling signal being detected, otherwise export second switch control signal.
Thus, at dim signal v
dimremain instruction minimum period, control circuit 14 does not quit work, but switches to Isobarically Control pattern, controls power stage circuit 11 output and is less than first threshold and is greater than the output voltage of Second Threshold.Ensure that LED load can not obtain on the one hand luminous higher than the voltage of first threshold, ensure that it is dimmer powered that auxiliary winding 12 can provide voltage directly or indirectly, avoids dimmer cisco unity malfunction on the other hand.
Easy understand, above-described embodiment only describes the electric circuit element relevant to solved technical problem, according to prior art, power supply circuits can also be comprised and be connected to logical circuit and drive the drive circuit between port, to provide necessary power supply and signal conditioning functions in control circuit 14.
Fig. 5 is the method flow diagram of the LED driver control method of the embodiment of the present invention, and it is for the LED driver shown in control chart 1.Described method comprises:
Step 510, work in first mode when described dim signal does not indicate minimum, otherwise, work in the second pattern.
Step 520, in the flrst mode, controls described power stage circuit according to dim signal and exports the drive current corresponding with dim signal.
Step 530, under the second mode, controls to make the output voltage of described power stage circuit be less than first threshold and be greater than Second Threshold.
Wherein, described first threshold is the minimum voltage that LED load is lighted.The output voltage values of described Second Threshold corresponding to the minimum supply power voltage of dimmer.
In a preferred embodiment, under the second mode, the not output switch control signal when power stage circuit output voltage is greater than protection threshold value;
Wherein, described protection threshold value is less than described Second Threshold.
In another optimal way, under the second mode, the switch controlling signal generated by constant-voltage control circuit controls described power stage circuit, makes described output voltage be less than first threshold and be greater than Second Threshold.
By when described dim signal is designated as minimum, control to make the output voltage of the power stage circuit of LED driver be less than first threshold, also, the minimum voltage that LED load can be lighted, makes dimming effect normally to realize; Meanwhile, by controlling to make output voltage be greater than Second Threshold, can ensure that auxiliary winding provides enough voltage to be dimmer normal power supply.Thus, when can solve dimmer directly or indirectly from auxiliary winding power taking, dimmer cannot obtain the normal problem worked of power supply in light modulation after minimum.
The foregoing is only the preferred embodiments of the present invention, be not limited to the present invention, to those skilled in the art, the present invention can have various change and change.All do within spirit of the present invention and principle any amendment, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (10)
1. a LED driver, comprising:
Power stage circuit;
Auxiliary winding, is coupled with the energy-storage travelling wave tube of described power stage circuit;
Dimmer, is directly or indirectly powered by described auxiliary winding, exports dim signal;
Control circuit, in the flrst mode, controls described power stage circuit according to dim signal and exports the drive current corresponding with dim signal, under the second mode, controls the output of described power stage circuit and is less than first threshold and is greater than Second Threshold output voltage;
Wherein, described control circuit works in the second pattern when described dim signal instruction is minimum, otherwise, work in first mode; Described first threshold is the minimum output voltage value that LED load can be made to light; The output voltage values of described Second Threshold corresponding to the minimum supply power voltage of dimmer.
2. LED driver according to claim 1, is characterized in that, described control circuit comprises:
Constant-current control circuit, generate switch controlling signal according to described dim signal, described switch controlling signal exports described drive current for controlling described power stage circuit;
Pressure limiting circuit, for working under the second mode, when power stage circuit output voltage is greater than first threshold described in protection threshold value, export pressure limiting enable signal, described protection threshold value is less than described first threshold;
Logical circuit, when receiving described pressure limiting enable signal, does not export described switch controlling signal, when not receiving described pressure limiting enable signal, exports described switch controlling signal.
3. LED driver according to claim 1, is characterized in that, described control circuit comprises:
Constant-current control circuit, generates the first switch controlling signal according to described dim signal, and described first switch controlling signal exports described drive current for controlling described power stage circuit;
Constant-voltage control circuit, generates second switch control signal, and described second switch control signal is less than first threshold for controlling the output of described power stage circuit and is greater than the output voltage of Second Threshold;
Logical circuit, exports described first switch controlling signal to power stage circuit in the flrst mode, exports described second switch control signal under the second mode to power stage circuit.
4. LED driver according to claim 1, is characterized in that, described control circuit comprises:
Constant-current control circuit, in the flrst mode, generates the first switch controlling signal according to dim signal, under the second mode, quits work, and described first switch controlling signal exports described drive current for controlling described power stage circuit;
Constant-voltage control circuit, does not work in the flrst mode, under the second mode, generates second switch control signal, and described second switch control signal is less than first threshold for controlling the output of described power stage circuit and is greater than the output voltage of Second Threshold;
Logical circuit, exports described first switch controlling signal when described first switch controlling signal being detected, otherwise exports described second switch control signal.
5. a control method for LED driver, described LED driver comprises power stage circuit, auxiliary winding and dimmer; Wherein, auxiliary winding is coupled with the energy-storage travelling wave tube of described power stage circuit; Described dimmer is directly or indirectly powered by described auxiliary winding, exports dim signal;
Described method comprises:
First mode is worked in when described dim signal does not indicate minimum, otherwise, work in the second pattern;
In the flrst mode, control described power stage circuit according to described dim signal and export the drive current corresponding with dim signal;
Under the second mode, control the output of described power stage circuit be less than first threshold and be greater than the output voltage of Second Threshold;
Wherein, described first threshold is the minimum output voltage value that LED load is lighted; The output voltage values of described Second Threshold corresponding to the minimum supply power voltage of dimmer.
6. LED driver control method according to claim 5, is characterized in that, under the second mode described, controls described power stage circuit and exports and be less than first threshold and the output voltage being greater than Second Threshold comprises:
Under the second mode, the not output switch control signal when power stage circuit output voltage is greater than protection threshold value;
Wherein, described protection threshold value is less than described first threshold.
7. LED driver control method according to claim 5, is characterized in that, under the second mode described, controls described power stage circuit and exports and be less than first threshold and the output voltage being greater than Second Threshold comprises:
Under the second mode, the switch controlling signal generated by constant-voltage control circuit controls described power stage circuit, makes described output voltage be less than first threshold and be greater than Second Threshold.
8. a control circuit, for controlling LED driver, described control circuit comprises:
Constant-current control circuit, generate switch controlling signal according to dim signal, described switch controlling signal exports described drive current for controlling described power stage circuit;
Pressure limiting circuit, for working under the second mode, when power stage circuit output voltage is greater than protection threshold value, export pressure limiting enable signal, described protection threshold value is less than described first threshold;
Logical circuit, when receiving described pressure limiting enable signal, does not export described switch controlling signal, when not receiving described pressure limiting enable signal, exports described switch controlling signal;
Wherein, described control circuit works in the second pattern when described dim signal instruction is minimum, otherwise, work in first mode; Described first threshold is the minimum voltage that LED load can be made to light; The output voltage values of described Second Threshold corresponding to the minimum supply power voltage of dimmer.
9. a control circuit, for controlling LED driver, described control circuit comprises:
Constant-current control circuit, generates the first switch controlling signal according to dim signal, and described first switch controlling signal exports the drive current corresponding with dim signal for controlling described power stage circuit;
Constant-voltage control circuit, generates second switch control signal, and described second switch control signal is less than first threshold for controlling the output of described power stage circuit and is greater than the output voltage of Second Threshold;
Logical circuit, exports described first switch controlling signal in the flrst mode, exports described second switch control signal under the second mode;
Wherein, described control circuit works in the second pattern when described dim signal instruction is minimum, otherwise, work in first mode; Described first threshold is the minimum voltage that LED load can be made to light; The output voltage values of described Second Threshold corresponding to the minimum supply power voltage of dimmer.
10. a control circuit, for controlling LED driver, described control circuit comprises:
Constant-current control circuit, in the flrst mode, generates the first switch controlling signal according to dim signal, quits work under the second mode, and described first switch controlling signal exports the drive current corresponding with dim signal for controlling described power stage circuit;
Constant-voltage control circuit, quits work in the flrst mode, under the second mode, generates second switch control signal, and described second switch control signal is less than first threshold for controlling the output of described power stage circuit and is greater than the output voltage of Second Threshold;
Logical circuit, exports described first switch controlling signal when described first switch controlling signal being detected, otherwise exports described second switch control signal;
Wherein, described control circuit works in the second pattern when described dim signal instruction is minimum, otherwise, work in first mode; Described first threshold is the minimum voltage that LED load can be made to light; The output voltage values of described Second Threshold corresponding to the minimum supply power voltage of dimmer.
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| CN201410584124.9A CN104270873B (en) | 2014-10-27 | 2014-10-27 | LED driver, control method and control circuit |
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| CN106162985A (en) * | 2016-06-30 | 2016-11-23 | 成都芯源系统有限公司 | LED driver and driving method |
| CN113423156A (en) * | 2021-06-19 | 2021-09-21 | 浙江榆阳电子有限公司 | Low-dimming-rate quick start circuit of LED dimming power supply and start method thereof |
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| Publication number | Publication date |
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| CN104270873B (en) | 2017-02-01 |
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