CN203759232U - Demagnetization detecting circuit and constant current driver applying the same - Google Patents
Demagnetization detecting circuit and constant current driver applying the same Download PDFInfo
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- CN203759232U CN203759232U CN201420016220.9U CN201420016220U CN203759232U CN 203759232 U CN203759232 U CN 203759232U CN 201420016220 U CN201420016220 U CN 201420016220U CN 203759232 U CN203759232 U CN 203759232U
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- 230000005347 demagnetization Effects 0.000 title claims abstract description 70
- 238000004146 energy storage Methods 0.000 claims abstract description 51
- 238000005070 sampling Methods 0.000 claims abstract description 22
- 230000000052 comparative effect Effects 0.000 claims description 14
- 239000004065 semiconductor Substances 0.000 claims description 14
- 101150101561 TOM70 gene Proteins 0.000 description 12
- 238000001514 detection method Methods 0.000 description 12
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- 101150090944 otomp gene Proteins 0.000 description 12
- 230000001939 inductive effect Effects 0.000 description 10
- 238000002955 isolation Methods 0.000 description 9
- 101100428373 Saccharomyces cerevisiae (strain ATCC 204508 / S288c) POR1 gene Proteins 0.000 description 8
- 101150087557 omcB gene Proteins 0.000 description 8
- 238000010586 diagram Methods 0.000 description 7
- 230000002459 sustained effect Effects 0.000 description 7
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- 238000004804 winding Methods 0.000 description 4
- 230000002159 abnormal effect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000003071 parasitic effect Effects 0.000 description 2
- 230000000630 rising effect Effects 0.000 description 2
- 239000003990 capacitor Substances 0.000 description 1
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Abstract
The utility model provides a demagnetization detecting circuit and a constant current driver applying the same. The demagnetization detecting circuit comprises a switch tube (M2), a bias unit (10) and a comparison unit (COMP1). A drain electrode end of the switch tube (M2) is connected with a to-be-detected energy storage element (L, T). The bias unit (10) is connected with a grid electrode end of the switch tube (M2) to sample a grid electrode end signal of the switch tube (M2) and send the sampling signal to the comparison unit (COMP1). Different input ends of the comparison unit (COMP1) respectively receive a signal and reference level (VREF_DM) from the bias unit (10) and compare the signal with the reference level. Through application of the circuit of the utility model, demagnetization ending of an energy storage element can be detected by direct utilizing the switch tube, so that the design cost and the size of the circuit are reduced and the application flexibility is improved.
Description
Technical field
The utility model relates to a kind of demagnetization testing circuit, in particular to a kind of demagnetization time detection circuit of perceptual energy-storage travelling wave tube, and applies the constant-flow driver of this circuit.
Background technology
Light emitting diode (light-emitting diode, LED), because of features such as its luminescence efficiency are high, the life-span is long, is used to lighting source at present more and more.Commercial or home light fixture is often driven by civil power (high pressure industrial-frequency alternating current), and this just need to be changed as LED steady current is provided by AC-DC.
AC-DC LED drive circuit (driver) is exactly in fact the constant-current power supply circuit of LED, it is luminous with driving LED that civil power is converted to specific output current by this circuit, and utilize device to modulate output current, keep constant to make exporting average current, and output current does not fluctuate with the fluctuation of input voltage.AC-DC LED drive circuit is divided into two kinds of non-isolation type and isolated forms.
LED Switching Power Supply is a kind of conventional LED constant-current supply.Its principle is, controls power electronic devices and is operated on off state, and be operated in high frequency instead of approach the low frequency of power frequency, output direct current.The detection that in current most of Switching Power Supply design, energy storage inductor demagnetization finishes is to adopt the mode of auxiliary winding to carry out.After energy storage inductor demagnetization finishes, by the auxiliary winding of energy storage inductor, produce voltage signal, offer switching power source control circuit.Although this detection scheme is simple, along with the change of energy storage inductor, thereby auxiliary winding also needs to change thereupon and causes design cost higher, and volume is larger, applies dumb.For LED driving switch power supply, inapplicable its cost is low, and volume is little, the requirement of applying flexible.
Utility model content
According to embodiment of the present utility model, a kind of demagnetization testing circuit is provided, apply this circuit and can directly utilize switching tube to carry out the detection that energy-storage travelling wave tube demagnetization finishes, so can reduce circuit design cost and volume, improve the dirigibility of application.
According to an aspect of the present utility model, a kind of demagnetization testing circuit is provided, comprising: switching tube, bias unit and comparing unit, wherein, the drain electrode end of switching tube is connected with tested energy-storage travelling wave tube; Bias unit is connected with the gate terminal of switching tube, samples, and this sampled signal is sent to comparing unit with the gate terminal signal to switching tube; The different input ends of comparing unit receive respectively signal and the datum from bias unit, and the two is compared.
According to the demagnetization testing circuit of the utility model embodiment, alternatively, bias unit comprises the combination of variable resistor or metal-oxide-semiconductor or metal-oxide-semiconductor and fixed resistance.
According to the demagnetization testing circuit of the utility model embodiment, alternatively, between the drain electrode of switching tube and grid, be connected with electric capacity.
According to the demagnetization testing circuit of the utility model embodiment, alternatively, this demagnetization testing circuit further comprises signal generating unit, for generating reference level.
According to the demagnetization testing circuit of the utility model embodiment, alternatively, datum is constant datum or unsteady datum.
According to the demagnetization testing circuit of the utility model embodiment, alternatively, comparing unit is voltage comparator or current comparator.
According to another aspect of the present utility model, a kind of constant-flow driver is provided, it comprises: fly-wheel diode, energy-storage travelling wave tube, the first switching tube, second switch pipe and sampling resistor, wherein, the positive pole of fly-wheel diode is connected with energy-storage travelling wave tube; Constant current or constant-voltage device as constant-flow driver load are connected with fly-wheel diode and energy-storage travelling wave tube; The first switching tube and second switch pipe are connected between energy-storage travelling wave tube and sampling resistor, and energy-storage travelling wave tube is connected with the drain electrode of second switch pipe, and the source electrode of second switch pipe is connected with the drain electrode of the first switching tube, and the source electrode of the first switching tube is connected to sampling resistor; One end of sampling resistor is connected with the source electrode of the first switching tube, other end ground connection, this switching power circuit further comprises: bias unit, logical block, the first comparing unit, driver element and the second comparing unit, wherein, bias unit is connected with the grid of second switch pipe, receives the signal from second switch tube grid; Bias unit output signal is to an input end of the first comparing unit; Another input end of the first comparing unit receives the first datum, and the first comparing unit compares signal and the first datum from bias unit, and comparative result is outputed to logical block; One end that sampling resistor is connected with the source electrode of the first switching tube is connected with an input end of the second comparing unit; Another input end of the second comparing unit receives the second datum, and the second comparing unit compares signal and the second datum from sampling resistor, and comparative result is outputed to logical block; The comparative result of logical block based on the first comparing unit and/or the comparative result of the second comparing unit generate control signal, and send to driver element; The output terminal of driver element is connected with the grid of the first switching tube, and according to drive this first switching tube from the control signal of logical block.
According to the constant-flow driver of the utility model embodiment, alternatively, make the first switching tube cut-off by its control signal in logical block in or after a period of time, the equivalent biasing resistor of bias unit is set to high-impedance state.
According to the constant-flow driver of the utility model embodiment, alternatively, in the demagnetization end time point of energy-storage travelling wave tube being detected or after a period of time, the equivalent biasing resistor of bias unit is set to low resistance state.
According to the constant-flow driver of the utility model embodiment, alternatively, in the demagnetization end time point of energy-storage travelling wave tube being detected or after a period of time, logical block makes the first switching tube conducting by its control signal.
According to the constant-flow driver of the utility model embodiment, alternatively, the first datum, the second datum and put in the timing control signal of bias unit at least one generate by being arranged at inner or outside signal generating unit or the logical block of constant-flow driver.
According to the constant-flow driver of the utility model embodiment, alternatively, energy-storage travelling wave tube is inductance or transformer.
According to the constant-flow driver of the utility model embodiment, alternatively, in the time that energy-storage travelling wave tube is transformer, different with the earth level of its second coil side at the earth level of primary side of this transformer.
According to the constant-flow driver of the utility model embodiment, alternatively, bias unit, logical block, the first comparing unit, the second comparing unit and driver element are integrated in a chip.
According to the constant-flow driver of the utility model embodiment, alternatively, constant current or constant-voltage device are light emitting diodes.
Brief description of the drawings
In order to be illustrated more clearly in the technical scheme of the utility model embodiment, below the accompanying drawing to embodiment is briefly described, apparently, the accompanying drawing in the following describes only relates to embodiment more of the present utility model, but not to restriction of the present utility model.
Fig. 1 shows according to the schematic diagram of the switching power circuit of an embodiment of the utility model;
Fig. 2 a～Fig. 2 c shows respectively the example of the circuit realization of the switching power circuit principle based on shown in Fig. 1;
Fig. 3 shows according to the switching power circuit of another embodiment of the utility model;
Fig. 4 shows the basic circuit diagram of having applied according to the non-isolation LED driver of the switching power circuit of the utility model embodiment;
Fig. 5 schematically shows the sequential logic of LED driver shown in Fig. 4;
Fig. 6 shows the basic circuit diagram of having applied according to the isolation LED driver of the switching power circuit of the utility model embodiment;
Fig. 7 schematically shows the sequential logic of LED driver shown in Fig. 6.
Embodiment
For making object, technical scheme and the advantage of the utility model embodiment clearer, below in conjunction with the accompanying drawing of the utility model embodiment, the technical scheme of the utility model embodiment is clearly and completely described.Obviously, described embodiment is a part of embodiment of the present utility model, instead of whole embodiment.Based on described embodiment of the present utility model, all other embodiment that those of ordinary skill in the art obtain under the prerequisite without creative work, belong to the scope that the utility model is protected.
Unless otherwise defined, technical term used herein or scientific terminology should be and in field, have the ordinary meaning that the personage of general technical ability understands under the utility model." first ", " second " and the similar word that in the utility model patent application specification and claims, use do not represent any order, quantity or importance, and are just used for distinguishing different ingredients.Equally, the similar words such as " " or " " do not represent restricted number yet, but represent to exist at least one.
Fig. 1 shows according to the schematic diagram of the switching power circuit of an embodiment of the utility model.As shown in Figure 1, switching power circuit comprises: sustained diode 1, inductance L, switching tube M1 and sampling resistor Rcs.Wherein, Vin is the busbar voltage that obtains after overcommutation of civil power or the input voltage obtaining by alternate manner.The negative pole of sustained diode 1 is connected to Vin; Inductance L is connected with the positive pole of sustained diode 1; Constant current or constant-voltage device are connected between busbar voltage and inductance L; Switching tube M1 and switching tube M2 are connected between inductance L and sampling resistor Rcs, one end that inductance L is connected with diode D1 positive pole is connected with the drain electrode of switching tube M2, the source electrode of switching tube M2 is connected with the drain electrode of switching tube M1, and the source electrode of switching tube M1 is connected to sampling resistor Rcs; One end of sampling resistor Rcs is connected with the source electrode of switching tube M1, other end ground connection.
As shown in Figure 1, switching power circuit further comprises: bias unit 10, logical block 20, comparator C OMP1, driving stage Driver and comparator C OMP2.Bias unit 10 is connected with the grid of switching tube M2, can receive the signal from switching tube M2 grid; Bias unit 10 output signals are to an input end of comparator C OMP1; Another input end of comparator C OMP1 receives datum VREF_DM, and comparator C OMP1 compares signal and the datum VREF_DM from bias unit 10, and comparative result is outputed to logical block 20; One end (ungrounded end) that sampling resistor Rcs is connected with the source electrode of M1 is connected with an input end of comparator C OMP2; Another input end of comparator C OMP2 receives datum VREF_CS, and comparator C OMP2 compares signal and the datum VREF_CS from sampling resistor Rcs, and comparative result is outputed to logical block 20; Logical block 20 is sent control signal to driving stage Driver; The output terminal of driving stage Driver is connected with the grid of switching tube M1, and according to carry out driving switch pipe M1 from the control signal of logical block 20.Wherein, datum VREF_DM and datum VREF_CS can be produced by this switching power circuit inside or outside same or different datum generation unit, and are input to each corresponding terminal.
The electric current of inductive current sampling resistor Rcs during to energy storage inductor L energy storage sampled, and sampled signal is input to comparator C OMP2; Comparator C OMP2 is by relatively sampled signal and datum VREF_CS determine that energy storage inductor L starts the time point of demagnetization; Comparator C OMP2 sends comparative result to logical block 20, and logical block 20 generates control signal PWM based on this comparative result, and this control signal is exported to driving stage Driver; Driving stage Driver is subject to the control of logical block 20 and turn-offs the first switching tube M1.Now inductance L and sustained diode 1 and constant current or constant-voltage device form loop, and energy storage inductor starts demagnetization.
According to the embodiment shown in Fig. 1, demagnetization testing circuit comprises switching tube M2, bias unit 10, comparator C OMP1, and this demagnetization testing circuit is for detection of the demagnetization end time point of energy storage inductor L.Adopt the demagnetization testing circuit according to the utility model embodiment, can directly utilize switching tube to carry out the detection that energy storage inductor demagnetization finishes, reduced to a great extent design cost and volume thereof, improved the dirigibility of application.In addition, due to according in the scheme of the utility model embodiment, the drain signal of switching tube M2 can reach several hectovolts, by the signal of detector switch pipe
Particularly, in the time that energy storage inductor L demagnetization finishes, the drain electrode of switching tube M2 can produce ringdown, and the stray capacitance Cgd(that this ringdown can be by switching tube M2 is as shown in dotted portion in Fig. 1, between the drain and gate of switching tube M2) be coupled to bias unit 10; Bias unit 10 is sampled to this ringdown, and the signal of sampling gained is outputed to the input end of comparator C OMP1; Comparator C OMP1 compares this signal and datum VREF_DM, judges according to comparative result whether inductance demagnetization finishes, thereby realizes the detection of the demagnetization end time point to energy storage inductor L.
Alternatively, described demagnetization testing circuit can comprise datum generating unit (not shown), generates datum VREF_DM; Or the circuit outside can this demagnetization testing circuit generates this datum VREF_DM.Alternatively, VREF_DM can be constant datum, can be also the inner unsteady datum producing as calculated.
When detecting that inductance demagnetization finishes, comparator C OMP1 output signal is to logical block 20.Logical block 20 generates control signal PWM based on this compare result signal, and this control signal is exported to driving stage Driver; Driving stage Driver drives the first switching tube M1 based on this control signal.
Fig. 2 a shows an example of the circuit realization of the switching power circuit principle based on shown in Fig. 1.As shown in Figure 2 a, bias unit 10 can be realized by variable resistor RBIAS.The resistance state of variable resistor RBIAS is set by offset signal VBIAS.For example, in the time of inductive energy storage, variable resistor RBIAS is set to low resistance state; And in the time that inductance demagnetizes, variable resistor RBIAS is set to high-impedance state, open detection time window, the demagnetization time of detection inductance.Control the current potential to second switch pipe M2 grid by the resistance state of bias-adjusted variable resistor RBIAS.The one end that variable resistor RBIAS can be connected with second switch pipe M2 grid is considered as the output terminal of bias unit 10.
Another example of realizing according to the circuit of the switching power circuit principle based on shown in Fig. 1, alternatively, bias unit 10 can be realized by metal-oxide-semiconductor M3, more specifically, conduction impedance by metal-oxide-semiconductor M3 is realized, metal-oxide-semiconductor device is applied to different gate source voltages, thereby the conduction impedance of metal-oxide-semiconductor is changed thereupon, as shown in Figure 2 b.Compare variable resistor, metal-oxide-semiconductor device is more easily realized by integrated circuit (IC) chip.
Another example of realizing according to the circuit of the switching power circuit principle based on shown in Fig. 1, alternatively, bias unit 10 can be realized by metal-oxide-semiconductor M3 is in parallel with fixed resistance, by the conduction impedance of MOS device and the in parallel next equivalent variable resistor that obtains of fixed resistance, as shown in Figure 2 c.By fixed resistance in parallel, can make the adjusting of equivalent resistance more accurate.
In the embodiment shown in Fig. 1 and Fig. 2 a～2c, comparator C OMP1 is voltage comparator.Alternatively, comparator C OMP1 can be also current comparator.For example, in the embodiment shown in fig. 3, comparator C OMP1 compares electric current and the reference current IREF_DM of the signal of one end output being connected with second switch pipe M2 grid from variable resistor RBIAS, and result is relatively outputed to logical block 20.This comparative result is the basis of the time point of determining energy storage inductor demagnetization end.
Fig. 4 shows the basic circuit diagram of having applied according to the non-isolation LED driver of the switching power circuit of the utility model embodiment.As shown in Figure 4, adopted in this embodiment the structure of bias unit 10 as shown in Figure 2 c.Alternatively, the embodiment of Fig. 4 also can adopt other bias unit scheme.
Comparison diagram 2c is known, and the non-isolation LED driver of Fig. 4 has comprised the switching power circuit of Fig. 2 c, and is provided with LED at the load end of this non-isolation LED driver, and this light emitting diode is as an example of aforesaid constant current or constant-voltage device.As previously mentioned, the non-isolation LED driver of Fig. 4 is actually a constant-flow driver.These one or more LEDs are connected between input voltage vin and energy storage inductor L, are driven by described switching power circuit.
After driver is started working, the first switching tube M1 conducting, electric current is from Vin, flow to ground through LED, L, M2, M1, Rcs, and electric current increases gradually, in the time that the peak value of electric current reaches the threshold value (VREF_CS) of setting, control and turn-off M1 by logical block 20 and driving stage Driver, now, inductance L is carried out afterflow by D1, LED, in the time that inductive current drops to zero, detects the demagnetization time of inductance L by aforesaid demagnetization testing circuit, and then control and make M1 conducting again by logical block 20 and driving stage Driver, start the new cycle.So circulation, thus make the average current of switching power circuit output keep constant.
Fig. 5 schematically shows the sequential logic of LED driver shown in Fig. 4.
As shown in Figure 5, when the control signal PWM of logical block 20 is while being high, driving stage Driver drives the first switching tube M1 conducting, and the drain terminal voltage Vdrain of second switch pipe M2 is low level, electric current from Vin through LED, inductance L, second switch pipe M2, the first switching tube M1 and resistance R cs to ground.Inductive current IL increases gradually, and correspondingly the voltage Vcs of resistance R cs also increases gradually.In this process, inductance L is carried out energy storage.
In the time that voltage Vcs reaches predetermined threshold value VREF_CS, logical block 20 drags down PWM, is low moment at PWM, switching tube M1 cut-off, and this time point is the starting point of demagnetization time.Afterwards, voltage Vcs falls back to zero level.At this, threshold value VREF_CS can be constant datum, can be also the datum producing afterwards as calculated.
When PWM is dragged down, the control voltage VBIAS_ctrl of variable bias resistance R BIAS can be set high, make biasing resistor RBIAS in high-impedance state, detect the demagnetization time of inductance.It is equivalent resistance that the biasing resistor RBIAS here can be understood as, and it can be the variable resistor in Fig. 2 a, can be also the conduction impedance of the metal-oxide-semiconductor in Fig. 2 b, and what can also be metal-oxide-semiconductor conduction impedance in Fig. 2 c with fixed resistance be in parallel.
After the first switching tube M1 cut-off, the drain voltage Vdrain of second switch pipe M2 raises, the corresponding rising of grid voltage Vgate of second switch pipe M2, and inductance L forms a loop by sustained diode 1, LED series connection, and inductive current IL reduces gradually.In this process, inductance L is demagnetized.
As previously mentioned, in the time that inductive current IL is reduced to zero, produce ringdown at the drain electrode end of M2, and due to the resonance effect of the stray capacitance Cgd of second switch pipe M2, this ringdown is coupled to the gate terminal (being reflected in grid voltage Vgate) of second switch pipe M2.The time point (as shown in dotted ellipse circle part in Fig. 5) that demagnetization finishes detected during lower than reference voltage VREF_DM at voltage Vgate.When detecting that inductive current is zero, the end time of demagnetizing, while putting, PWM was set to height immediately, started next cycle.Now VBIAS_ctrl is dragged down, RBIAS enters low resistive state, does not carry out the detection of inductance demagnetization.So circulation, thus make the average current of switching power circuit output keep constant.
Under the mode of operation shown in the sequential chart of Fig. 5, inductive current IL does not remain for a period of time of zero, but after being reduced to zero, the growth that will begin in a minute, is therefore to work in electric current critical conduction mode.But the LED driver of Fig. 4 also can work in discontinuous current pattern, that is to say, control inductive current and remain after zero a period of time, then to make pwm signal be high, start next cycle.
In addition, due to the impact of some parasitic parameters of switching tube, may there is the burr that some are abnormal in Vdrain, and correspondingly these burrs also may appear in Vgate, see the Vgate waveform in Fig. 5, and this waveform exists burr phenomena in demagnetization starts a period of time.Thus, alternatively, be the false triggering that prevents that demagnetization from detecting, demagnetization testing circuit is set to, and after PWM is low, starts to detect through one section of delay again, VBIAS_ctrl is set high through one section of delay again.This delay is the lead-edge-blanking time, as shown in the LEB part in the VBIAS_ctrl waveform of Fig. 5.The lead-edge-blanking time is set can avoiding switching switches the switch burr of moment, avoids erroneous judgement, strengthens the reliability of demagnetization time detecting.
Fig. 6 shows the basic circuit diagram of having applied according to the isolation LED driver of the switching power circuit of the utility model embodiment.The key distinction of the LED driver of the LED driver shown in Fig. 6 and Fig. 4 is, replaced energy storage inductor L with transformer T, and realized the isolation of drives side (former limit Lp side) and load-side (secondary Ls side) by this transformer T.Particularly, as shown in Figure 6, LED driver comprises sustained diode 2 in the secondary side of transformer T, alternatively, also comprises filter capacitor C1.In switching power circuit, identical with the scheme in Fig. 4 for the energy storage of transformer T and the control of demagnetization.
Alternatively, different with the earth level of its second coil side at the earth level of primary side of transformer T.Because primary coil is connected on civil power high-pressure side, secondary coil is connected on load LED side, if adopt both not schemes on ground altogether, safer secondary (being generally low-voltage) like this.
Alternatively, transformer T is N:1(Np:Ns) isolating transformer, wherein N is natural number.
Fig. 7 schematically shows the sequential logic of LED driver shown in Fig. 6.
As shown in Figure 7, when the control signal PWM of logical block 20 is while being high, driving stage Driver drives the first switching tube M1 conducting, the drain terminal voltage Vdrain of second switch pipe M2 is low level, electric current from Vin through former limit Lp, second switch pipe M2, the first switching tube M1 and the resistance R cs of transformer T to ground.Transformer current (primary current ILp) increases gradually, and correspondingly the voltage Vcs of resistance R cs also increases gradually.In this process, transformer T carries out energy storage.
In the time that voltage Vcs reaches predetermined threshold value VREF_CS, logical block 20 drags down PWM, is low moment at PWM, switching tube M1 cut-off, and this time point is the starting point of demagnetization time.Afterwards, voltage Vcs falls back to zero level.Due to the characteristic of transformer T, the time point (time point that namely demagnetization starts) finishing in energy storage, primary current ILp reduces to 0, and secondary current ILs moment is drawn high a high point value simultaneously, as shown in Figure 7.At this, threshold value VREF_CS can be constant datum, can be also the datum producing afterwards as calculated.
When PWM is dragged down, the control voltage VBIAS_ctrl of variable bias resistance R BIAS can be set high, make biasing resistor RBIAS in high-impedance state, detect the demagnetization time of perceptual energy-storage travelling wave tube.It is equivalent resistance that the biasing resistor RBIAS here can be understood as, and it can be the variable resistor in Fig. 2 a, can be also the conduction impedance of the metal-oxide-semiconductor in Fig. 2 b, and what can also be metal-oxide-semiconductor conduction impedance in Fig. 2 c with fixed resistance be in parallel.
After the first switching tube M1 cut-off, the drain voltage Vdrain of second switch pipe M2 raises, the corresponding rising of grid voltage Vgate of second switch pipe M2, the secondary Ls of transformer T forms a loop by connecting with sustained diode 2, LED simultaneously, and the electric current I Ls of secondary Ls reduces gradually.In this process, transformer T demagnetizes.As previously mentioned, in the time that the electric current I Ls of secondary Ls is reduced to zero, produce ringdown at the drain electrode end of M2, and due to the resonance effect of the stray capacitance Cgd of second switch pipe M2, this ringdown is coupled to the gate terminal (being reflected in grid voltage Vgate) of second switch pipe M2.The time point (as shown in dotted ellipse circle part in Fig. 7) that demagnetization finishes detected during lower than reference voltage VREF_DM at voltage Vgate.
As shown in Figure 7, between the adjacent energy storage cycle and demagnetization cycle, keeping for some time transformer current (ILp/ILs) is zero, that is to say, control transformer electric current remained after zero a period of time, then to make pwm signal be high, starts next cycle.Visible, the situation as shown in the sequential chart of Fig. 7, the LED driver of Fig. 6 works in discontinuous current pattern.Under discontinuous current pattern, can, detecting that demagnetization end time point is rear to pwm signal being set high between the time point of (energy storage starts), make RBIAS enter low resistive state by dragging down VBIAS_ctrl signal, the detection of the time of not demagnetizing.In Fig. 7, the time point that demagnetization finishes being detected and dragging down between the time point of VBIAS_ctrl signal to have a period of time interval, drag down the time point of VBIAS_ctrl signal and time point that pwm signal is set high between also there is a period of time interval.Consider Time Delay of Systems, this configuration is more accurate, the situation particularly for example, being generated by same signal generator (logical block 20) at timing control signal (pwm signal and VBIAS_ctrl signal).
Alternatively, the LED driver of Fig. 6 also can work in electric current critical conduction mode.Under electric current critical conduction mode, can in demagnetization end time point be detected, drag down VBIAS_ctrl signal and pwm signal is set high.
Equally, alternatively, due to the impact of some parasitic parameters of switching tube, may there is the burr that some are abnormal in Vdrain, also may there are these burrs in Vgate correspondingly, sees the Vgate waveform in Fig. 7, and this waveform exists burr phenomena in demagnetization starts a period of time.Thus, alternatively, be the false triggering that prevents that demagnetization from detecting, demagnetization testing circuit is set to, and after PWM is low, starts to detect through one section of delay again, VBIAS_ctrl is set high through one section of delay again.This delay is the lead-edge-blanking time, as shown in the LEB part in the VBIAS_ctrl waveform of Fig. 7.
Alternatively, at aforesaid switching power circuit and apply in the embodiment of constant-flow driver of this circuit, also can be in the drain electrode of a second switch pipe M2 external capacitive in parallel with grid, to strengthen coupling.
Alternatively, can comprise one or more signal generating unit according to the switching power circuit of the utility model embodiment and the constant-flow driver of applying this circuit, for generating reference signal such as VREF_CS, VREF_DM, IREF_DM, such as the timing control signal of VBIAS_ctrl and such as the offset signal of VBIAS.Alternatively, timing control signal VBIAS_ctrl can be generated by logical block 20.
Alternatively, these reference signals and/or offset signal also can be generated by external signal generating unit.Alternatively, according to the switching power circuit of the utility model embodiment and apply in the constant-flow driver of this circuit, bias unit 10, logical block 20, comparator C OMP1, comparator C OMP2, driving stage Driver form a control circuit, and can form this control circuit by integrated circuit (IC) chip.Alternatively, aforesaid signal generating unit can belong to this control circuit, also can be independent of this control circuit.In addition, alternatively, switching tube M2 and/or switching tube M1 also can be integrated in this control circuit chip.In addition, sampling resistor Rcs also can be integrated in described control circuit chip.Adopt the mode of integrated chip can reduce circuit volume, reduce costs, also can standardization device parameter.
Can detect the demagnetization detection time of energy-storage travelling wave tube according to the demagnetization testing circuit of the utility model embodiment.This energy-storage travelling wave tube comprises aforesaid inductance, transformer, can also comprise other perception (inductive) energy-storage travelling wave tube.
According to the demagnetization testing circuit of the utility model embodiment and applied the constant-current drive circuit (comprising LED drive circuit) of this demagnetization testing circuit, save the auxiliary winding that classic method that energy-storage travelling wave tube demagnetization detects is used, can reduce application cost and volume, make application more flexible.
The above is only exemplary embodiment of the present utility model, but not for limiting protection domain of the present utility model, protection domain of the present utility model is determined by appended claim.
Claims (15)
1. a demagnetization testing circuit, is characterized in that, comprising: switching tube (M2), bias unit (10) and comparing unit (COMP1), wherein,
The drain electrode end of switching tube (M2) and tested energy-storage travelling wave tube (L, T) connect;
Bias unit (10) is connected with the gate terminal of switching tube (M2), so that the gate terminal signal of switching tube (M2) is sampled, and this sampled signal is sent to described comparing unit (COMP1);
The different input ends of comparing unit (COMP1) receive respectively from the signal of bias unit (10) and datum (VREF_DM), and the two is compared.
2. demagnetization testing circuit according to claim 1, is characterized in that, described bias unit (10) comprises the combination of variable resistor (RBIAS) or metal-oxide-semiconductor (M3) or metal-oxide-semiconductor and fixed resistance.
3. demagnetization testing circuit according to claim 1, is characterized in that, between the drain electrode of described switching tube (M2) and grid, is connected with electric capacity.
4. demagnetization testing circuit according to claim 1, is characterized in that, further comprises signal generating unit, for generating described datum (VREF_DM).
5. demagnetization testing circuit according to claim 1, is characterized in that, described datum (VREF_DM) is constant datum or unsteady datum.
6. demagnetization testing circuit according to claim 1, is characterized in that, described comparing unit (COMP1) is voltage comparator or current comparator.
7. a constant-flow driver, is characterized in that, comprising:
Fly-wheel diode (D1), energy-storage travelling wave tube (L, T), the first switching tube (M1), second switch pipe (M2) and sampling resistor (Rcs), wherein,
Positive pole and the energy-storage travelling wave tube (L, T) of fly-wheel diode (D1) are connected;
Constant current or constant-voltage device as described constant-flow driver load connect with described fly-wheel diode (D1) and described energy-storage travelling wave tube (L, T);
The first switching tube (M1) and second switch pipe (M2) are connected to described energy-storage travelling wave tube (L, T) and between described sampling resistor (Rcs), described energy-storage travelling wave tube (L, T) be connected with the drain electrode of second switch pipe (M2), the source electrode of second switch pipe (M2) is connected with the drain electrode of the first switching tube (M1), and the source electrode of the first switching tube (M1) is connected to described sampling resistor (Rcs);
One end of described sampling resistor (Rcs) is connected with the source electrode of the first switching tube (M1), other end ground connection,
Described switching power circuit further comprises:
Bias unit (10), logical block (20), the first comparing unit (COMP1), driver element (Driver) and the second comparing unit (COMP2), wherein,
Bias unit (10) is connected with the grid of second switch pipe (M2), receives the signal from second switch pipe (M2) grid; Bias unit (10) output signal is to an input end of the first comparing unit (COMP1);
Another input end of the first comparing unit (COMP1) receives the first datum (VREF_DM), the first comparing unit (COMP1) compares signal and the first datum (VREF_DM) from bias unit (10), and comparative result is outputed to logical block (20);
One end that sampling resistor (Rcs) is connected with the source electrode of the first switching tube (M1) is connected with an input end of the second comparing unit (COMP2);
Another input end of the second comparing unit (COMP2) receives the second datum (VREF_CS), the second comparing unit (COMP2) compares signal and the second datum (VREF_CS) from sampling resistor (Rcs), and comparative result is outputed to logical block (20);
The comparative result of logical block (20) based on the first comparing unit (COMP1) and/or the comparative result of the second comparing unit (COMP2) generate control signal, and send to driver element (Driver);
The output terminal of driver element (Driver) is connected with the grid of the first switching tube (M1), and according to drive this first switching tube (M1) from the control signal of logical block (20).
8. constant-flow driver according to claim 7, it is characterized in that, make described the first switching tube (M1) cut-off by its control signal (PWM) in described logical block (20) in or a period of time (LEB) afterwards, the equivalent biasing resistor (RBIAS) of described bias unit (10) is set to high-impedance state.
9. constant-flow driver according to claim 7, it is characterized in that, after some time demagnetization end time or a period of time of described energy-storage travelling wave tube (L, T) being detected, the equivalent biasing resistor (RBIAS) of described bias unit (10) is set to low resistance state.
10. constant-flow driver according to claim 7, it is characterized in that, after some time demagnetization end time or a period of time of described energy-storage travelling wave tube (L, T) being detected, described logical block (20) makes described the first switching tube (M1) conducting by its control signal (PWM).
11. constant-flow drivers according to claim 7, it is characterized in that, described the first datum (VREF_DM), described the second datum (VREF_CS) and put in the timing control signal (VBIAS_ctrl) of described bias unit (10) at least one generate by being arranged at the inner or outside signal generating unit of described constant-flow driver or described logical block (20).
12. according to the constant-flow driver described in any one in claim 7-11, it is characterized in that, described energy-storage travelling wave tube (L, T) is inductance (L) or transformer (T).
13. constant-flow drivers according to claim 12, is characterized in that, in the time that described energy-storage travelling wave tube (L, T) is transformer (T), different with the earth level of its second coil side at the earth level of primary side of this transformer (T).
14. according to the constant-flow driver described in any one in claim 7-11, it is characterized in that, at least described bias unit (10), described logical block (20), described the first comparing unit (COMP1), described the second comparing unit (COMP2) and described driver element (Driver) are integrated in a chip.
15. according to the constant-flow driver described in any one in claim 7-11, it is characterized in that, described constant current or constant-voltage device are light emitting diode (LED).
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| Application Number | Priority Date | Filing Date | Title |
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| CN201420016220.9U CN203759232U (en) | 2014-01-10 | 2014-01-10 | Demagnetization detecting circuit and constant current driver applying the same |
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| CN201420016220.9U CN203759232U (en) | 2014-01-10 | 2014-01-10 | Demagnetization detecting circuit and constant current driver applying the same |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103728578A (en) * | 2014-01-10 | 2014-04-16 | 美芯晟科技（北京）有限公司 | Demagnetization detection method, demagnetization detection circuit and constant current driver applying demagnetization detection circuit |
| CN110554303A (en) * | 2019-09-27 | 2019-12-10 | 芯好半导体(成都)有限公司 | Demagnetization time detection circuit and method and power supply device |
-
2014
- 2014-01-10 CN CN201420016220.9U patent/CN203759232U/en not_active Expired - Lifetime
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103728578A (en) * | 2014-01-10 | 2014-04-16 | 美芯晟科技（北京）有限公司 | Demagnetization detection method, demagnetization detection circuit and constant current driver applying demagnetization detection circuit |
| CN110554303A (en) * | 2019-09-27 | 2019-12-10 | 芯好半导体(成都)有限公司 | Demagnetization time detection circuit and method and power supply device |
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Address after: Room 01, 10 / F, block a, Tiangong building, Keda, 30 Xueyuan Road, Haidian District, Beijing 100089 Patentee after: Meixinsheng Technology (Beijing) Co.,Ltd. Address before: 100086 office building 1006, Crowne Plaza Hotel, No. 106, Zhichun Road, Haidian District, Beijing Patentee before: MAXIC TECHNOLOGY (BEIJING) Co.,Ltd. |
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Granted publication date: 20140806 |