CN203279254U - LED drive circuit and its constant current control circuit - Google Patents
LED drive circuit and its constant current control circuit Download PDFInfo
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- CN203279254U CN203279254U CN2013201510229U CN201320151022U CN203279254U CN 203279254 U CN203279254 U CN 203279254U CN 2013201510229 U CN2013201510229 U CN 2013201510229U CN 201320151022 U CN201320151022 U CN 201320151022U CN 203279254 U CN203279254 U CN 203279254U
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Abstract
The utility model provides an LED driving circuit and a constant current control circuit thereof. The constant current control circuit comprises: an error amplifier, a conduction time control module, and a driving signal generation module. A first input terminal of the error amplifier receives a load current through a sampling port, and a second input terminal of the error amplifier receives a preset first reference voltage; an input terminal of the conduction time control module is connected with an output terminal of the error amplifier; the driving signal generation module according to an output signal of the conduction time control module generates a driving signal for cutting off a switch tube in the LED driving circuit, and the driving signal is outputted through a driving port; a ground port is configured to receive an off-ground voltage; and the off-ground voltage is different from a reference ground voltage of an input voltage of the LED driving circuit. The LED driving circuit and the constant current control circuit thereof can realize the accurate constant current control, high power coefficient, low input harmonic wave, high work security and high transition efficiency.
Description
Technical field
The utility model relates to the LED Driving technique, relates in particular to a kind of high constant current accuracy LED drive circuit and constant-current control circuit thereof.
Background technology
At present, in LED drive circuit, isolation mode and Non-isolation model be can be divided into according to the difference of peripheral circuit topological structure, decompression mode and voltage boosting-reducing pattern are divided into according to the height of input/output voltage.Because generally adopt stagnant ring to control, the shortcoming of present non-isolation LED drive circuit maximum is that constant-current characteristics is relatively poor, and output current is subjected to input voltage, output voltage and inductance value variable effect larger.
Fig. 1 is the schematic diagram of the LED drive circuit of working under traditional decompression mode, mainly comprises constant-current control circuit 10, sustained diode 1, inductance L, capacitor C 1, switching tube M1, sampling resistor Rcs.As shown in Figure 1, the negative pole of sustained diode 1 is connected to positive pole and the power supply VIN of load LED, and the positive pole of sustained diode 1 is connected to the first end of inductance L, and the second end of inductance L is connected to the negative pole of load LED; Switching tube M1 is connected between inductance L and sampling resistor Rcs, the controlled constant-current control circuit 10 that is formed on of this switching tube M1.Constant-current control circuit comprises timer 11, comparison module 12 and rest-set flip-flop 13.
During switching tube M1 conducting, the electric current of inductance L increases, and port CS place voltage increases, until port CS place voltage is when being elevated to reference voltage V 1, the output signal of comparison module 12 is overturn, the output zero clearing of rest-set flip-flop 13, switching tube M1 shutoff.Timer 11 beginning timing, inductance L is by sustained diode 1, load LED discharge, current reduction; When timer 11 timing finish, rest-set flip-flop 13 set, switching tube M1 reopens, and completes one-period.
LED drive circuit shown in Figure 1 is decompression mode, what port CS sampled in fact is the electric current of switching tube M1, when switching tube M1 conducting, the switching tube electric current is equal to inductive current (being load current), therefore, reach by port CS sampling switch tube current the purpose of controlling inductive current peak during this drive circuit.Furthermore, the electric current of the sampling resistor Rcs that flows through in Fig. 1 is in fact the switching tube electric current, and constant-current control circuit 10 has just been controlled the peak value of switching tube electric current in fact by after port CS sample rate current.Because the peak value of switching tube electric current is equal to the peak value of inductive current and load current, so can limiting inductive current peak, the selection by peripheral inductance value reaches the constant current effect.
In above-mentioned traditional drive circuit, have following shortcoming: this drive circuit comes constant output current by controlling peak current and ripple current, and peak current is determined by comparison module 12, reference voltage V 1 and sampling resistor Rcs.The slope that inductive current descends is directly proportional to output voltage VO UT, is inversely proportional to the inductance value L of inductance L, and ripple current IPP and output current IO UT are shown below respectively:
Wherein, TOFF is the turn-off time of switching tube M1, and IPK is the peak value of inductive current, and Rcs is the resistance value of sampling resistor Rcs.
Fig. 2 is work wave corresponding to drive circuit shown in Figure 1, and clearly, the output average current changes with output voltage and inductance value.Simultaneously, if after considering the delay TDELAY of comparison module 12, in fact output current also has direct relation with input voltage.In fact inductive current peak has relation with the delay TDELAY of input voltage and comparison module 12, and the inductive current rate of rise poor to input and output voltage (VIN-VOUT) is directly proportional, and inductance value L is inversely proportional to, and is shown below:
To sum up, the output current of the LED drive circuit of prior art is subject to the impact of inductance value, input voltage, output voltage, and stability is low, and constant current accuracy is poor, and has increased the complexity of system and the cost of inductance.And traditional LED Drive and Control Circuit power factor correction (PFC) control circuit of usually also needing to fill out in addition paddy circuit and so on reaches the requirement of high power factor.
The defective of above-mentioned prior art mainly comes from: fail load current is sampled fully, only the switching tube electric current just equals load current when the switching tube conducting, and when switching tube turn-offed, the switching tube electric current was 0, was not equal to load current, both had deviation.
In order to access load current, a kind of mode utilizes the switching tube electric current of 14 pairs of port CS samplings of sampling hold circuit to change as shown in Figure 3, comes the shape of fictitious load electric current with this, and then amplifies integration.Yet generally speaking, sampling hold circuit 14 can increase the circuit area, and still has certain distortion between the load current that obtains after the sampling maintenance and real load current.
In order to obtain load current, sampling resistor can also be connected on load one end and without switching tube, constant-current control circuit is by this sampling resistor load current of sampling.But, what adopt because peripheral circuit is common is on the spot, voltage on sampling resistor high pressure normally for the ground port of constant-current control circuit, make the sample port of constant-current control circuit become high pressure port, its inside need to be changed high pressure, be also that constant-current control circuit can not adopt common process, and will use high-pressure process, increased cost.Therefore, another kind of mode of the prior art as shown in Figure 4, sampling resistor Rs is connected on load one end and without switching tube M1, constant-current control circuit 10 has port CS1 and two sample port of CS2, be connected to respectively node CS1 and the CS2 at sampling resistor Rcs two ends, voltage by 15 pairs of level shift modules sampling resistor Rcs two ends is processed, and avoids conversion to high pressure with this.But, adopt drive circuit shown in Figure 4, can cause constant-current control circuit to increase a port, meaning for chip increases a pin, has reduced practicality.
The utility model content
The technical problems to be solved in the utility model is to provide a kind of LED drive circuit and constant-current control circuit thereof, need not high pressure port or increase port just to realize accurate constant current control, high power factor, low input harmonics, high workload fail safe and high conversion efficiency.
For solving the problems of the technologies described above, the utility model provides a kind of constant-current control circuit of LED drive circuit, has the port of driving, sample port and ground port, it is characterized in that, described constant-current control circuit comprises:
Error amplifier, its first input end directly receives load current via described sample port, and its second input receives the first default reference voltage;
The ON time control module, its input is connected with the output of described error amplifier, determines ON time according to the voltage that the output of described error amplifier is exported;
Drive the signal generation module, generate the driving signal of the switching tube that is used for the shutoff LED drive circuit according to the output signal of described ON time control module, described driving signal is exported via described driving port;
Wherein, described ground port arrangement is for receiving floating ground voltage, and described floating ground voltage is different from the reference ground voltage of the input voltage of described LED drive circuit.
According to an embodiment of the present utility model, described constant-current control circuit also comprises: the polarity modular converter, the first input end of described error amplifier receives described load current via this polarity modular converter from described sample port, described polarity modular converter is sampled to this load current and the voltage of sampling gained is carried out polarity conversion, and the first output of described polarity modular converter is connected with the first input end of described error amplifier.
According to an embodiment of the present utility model, described constant-current control circuit also has the zero passage detection port, described constant-current control circuit also comprises: inductive current zero passage detection module, inductive current to described zero passage detection port input carries out zero passage detection, and described driving signal generation module generates according to the output signal of described inductive current zero passage detection module the driving signal that is used for the described switching tube of conducting.
According to an embodiment of the present utility model, described constant-current control circuit also comprises: timer, described driving signal generation module generates according to the output signal of described timer the driving signal that is used for the described switching tube of conducting.
According to an embodiment of the present utility model, described constant-current control circuit also comprises: Current-Limiting Comparator, and its first input end receives the current limliting sampled voltage, and its second input receives the second default reference voltage.
According to an embodiment of the present utility model, described constant-current control circuit also has the current limliting port, and the first input end of described Current-Limiting Comparator receives described current limliting sampled voltage via described current limliting port.
according to an embodiment of the present utility model, described constant-current control circuit also comprises: the polarity modular converter, the first input end of described error amplifier receives described load current via this polarity modular converter from described sample port, described polarity modular converter carries out the polarity conversion to this load current, the first output of described polarity modular converter is connected with the first input end of described error amplifier, described polarity modular converter has the second output, the first input end of described Current-Limiting Comparator receives described current limliting sampled voltage from the second output of described polarity modular converter.
According to an embodiment of the present utility model, described constant-current control circuit also has the zero passage detection port, described constant-current control circuit also comprises: inductive current zero passage detection module, inductive current to described zero passage detection port input carries out zero passage detection, described driving signal generation module generates according to the output signal of described inductive current zero passage detection module the driving signal that is used for the described switching tube of conducting, and described driving signal generation module comprises:
Or door, its first input end connects the output of described ON time control module, and its second input connects the output of described Current-Limiting Comparator;
Rest-set flip-flop, its set input connects the output of described inductive current zero passage detection module, and its RESET input connects output described or door, and its output produces described driving signal.
According to an embodiment of the present utility model, described constant-current control circuit also comprises: timer, described driving signal generation module generates according to the output signal of described timer the driving signal that is used for the described switching tube of conducting, and described driving signal generation module comprises:
Or door, its first input end connects the output of described ON time control module, and its second input connects the output of described Current-Limiting Comparator;
Rest-set flip-flop, its set input connects the output of described timer, and its RESET input connects output described or door, and its output produces described driving signal.
According to an embodiment of the present utility model, described constant-current control circuit also comprises the compensation port, and the output of described error amplifier is connected and is configured to via integrating capacitor ground connection with this compensation port.
The utility model also provides a kind of LED drive circuit, comprise the described constant-current control circuit of above any one and with the peripheral circuit of its coupling.
According to an embodiment of the present utility model, described peripheral circuit is the voltage boosting-reducing mode circuit.
According to an embodiment of the present utility model, described peripheral circuit comprises:
Switching tube, its control end connects the driving port of described constant-current control circuit, and its first power termination is received input voltage;
The constant current sampling resistor, its first end connects the second power end of described switching tube;
Inductance, its first end connects the first end of described constant current sampling resistor, its second end ground connection;
Fly-wheel diode, its negative pole connects the second end of described constant current sampling resistor;
Output capacitance, its first end connects the positive pole of described fly-wheel diode, its second end ground connection;
Wherein, described ground port connects in the first end of described constant current sampling resistor and the second end, and described sample port connects the first end of described constant current sampling resistor and another in the second end.
According to an embodiment of the present utility model, described peripheral circuit comprises:
Switching tube, its control end connects the driving port of described constant-current control circuit, and its first power termination is received input voltage;
The constant current sampling resistor, its first end connects the second power end of described switching tube;
Inductance, its first end connects the second end of described current limliting sampling resistor, its second end ground connection;
Fly-wheel diode, its negative pole connects the first end of described constant current sampling resistor;
Output capacitance, its first end connects the positive pole of described fly-wheel diode, its second end ground connection;
Wherein, the ground port of described constant-current control circuit connects in the first end of described constant current sampling resistor and the second end, and the sample port of described constant-current control circuit connects the first end of described constant current sampling resistor and another in the second end.
According to an embodiment of the present utility model, described peripheral circuit also comprises: the current limliting sampling resistor, the first end of described constant current sampling resistor connects the second power end of described switching tube via this current limliting sampling resistor, the second power end of described switching tube also connects the current limliting port of described constant-current control circuit.
According to an embodiment of the present utility model, the first input end of the Current-Limiting Comparator in described constant-current control circuit receives described current limliting sampled voltage from the second output of described polarity modular converter.
According to an embodiment of the present utility model, described LED drive circuit also comprises: rectifier bridge, outside AC signal produce described input voltage after via described rectifier bridge rectification.
According to an embodiment of the present utility model, described output capacitance is configured in parallel with load LED.
Compared with prior art, the utlity model has following advantage:
The constant-current control circuit of the utility model embodiment adopts closed-loop control, the sample port Direct Sampling load current of constant-current control circuit, compare via the sample mode of load current of switching tube with traditional, the load current that makes output is with only relevant with the resistance value Rcs of the first reference voltage Vref 1 of inside and constant current sampling resistor, the load current of output no longer is subjected to the impact of inductance value, input voltage, output voltage, constant current accuracy is high, and stability is better.Particularly, the resistance value Rcs relation of output load current IOUT and the first reference voltage Vref 1 and constant current sampling resistor is as follows:
Compare with traditional mode of the switch tube current being changed to obtain load current with sampling hold circuit, avoided the problem of the circuit area change that sampling hold circuit brings.
In addition, the ground port arrangement of the constant-current control circuit of the utility model embodiment is floated ground voltage for receiving, thereby only needs a sample port and this ground port to coordinate the sampling that just can realize load current, need not unnecessary port.
In addition, the constant-current control circuit of the utility model embodiment can also be by the external integrating capacitor of compensation port, existence due to external integrating capacitor, the voltage of compensation port keeps constant in single ac cycle, coordinate the ON time control module, make the ON time in single ac cycle keep constant, thereby realize High Power Factor.Fill out the paddy circuit with the outside of traditional employing load and realize that High Power Factor compares, greatly saved cost and machine volume.
In addition, the constant-current control circuit of the utility model embodiment is particularly useful for the LED drive circuit of voltage boosting-reducing pattern, can also realize current-limiting protection by Current-Limiting Comparator in addition, promotes the fail safe of circuit.
Description of drawings
Fig. 1 is the structural representation of the LED drive circuit of working under a kind of non-isolated buck pattern in prior art;
Fig. 2 is the working waveform figure of LED drive circuit shown in Figure 1;
Fig. 3 is the structural representation of the LED drive circuit of working under another kind of non-isolated buck pattern in prior art;
Fig. 4 is the structural representation of the LED drive circuit of working under another non-isolated buck pattern in prior art;
Fig. 5 is the structural representation of the LED drive circuit of the utility model the first embodiment;
Fig. 6 is the working waveform figure of LED drive circuit shown in Figure 3;
Fig. 7 is the structural representation of the LED drive circuit of the utility model the second embodiment;
Fig. 8 is the structural representation of the LED drive circuit of the utility model the 3rd embodiment;
Fig. 9 is the working waveform figure of LED drive circuit shown in Figure 6;
Figure 10 is the structural representation of the LED drive circuit of the utility model the 4th embodiment;
Figure 11 is the structural representation of the LED drive circuit of the utility model the 5th embodiment.
Embodiment
The utility model is described in further detail below in conjunction with specific embodiments and the drawings, but should not limit protection range of the present utility model with this.
With reference to figure 5, in the first embodiment of the present utility model, LED drive circuit comprises: constant-current control circuit 30, switching tube M1, current limliting sampling resistor RILIM, constant current sampling resistor Rcs, inductance L, sustained diode 1, output capacitance C1, the first zero passage detection resistance R 1, the second zero passage detection resistance R 2, rectifier bridge 38.Wherein constant-current control circuit 30 have zero passage detection port ZCD, drive port DR, current limliting port ILIM, sample port CS, port GND, compensation port COMP, constant-current control circuit 30 comprises with lower module: inductive current zero passage detection module 31, error amplifier 33, ON time control module 34, Current-Limiting Comparator 35 and drive the signal generation module.
Wherein, the inductive current of 31 pairs of zero passage detection port ZCD inputs of inductive current zero passage detection module carries out zero passage detection.The first input end of error amplifier 33 connects sample port CS, its second input receives the first default reference voltage Vref 1, in the present embodiment, the first reference voltage Vref 1 is provided by reference voltage source, one end of this reference voltage source connects the second input of error amplifier 33, other end ground connection (more specifically, being connected with ground port GND).In addition, the output of error amplifier 33 is connected with compensation port COMP, and compensation port COMP is via integrating capacitor C2 ground connection.The input of ON time control module 34 is connected with the output of error amplifier 33, determines ON time according to the voltage (being also the voltage on integrating capacitor C2) of error amplifier 33 output outputs.The first input end of Current-Limiting Comparator 35 receives the current limliting sampled voltage via current limliting port ILIM, its second input receives the second default reference voltage Vref 2, as a nonrestrictive example, the second reference voltage Vref 2 is provided by reference voltage source, one end of this reference voltage source connects the second input of Current-Limiting Comparator 35, other end ground connection (more specifically, being connected with ground port GND).
Drive the signal generation module according to the output signal generation driving signal of inductive current zero passage detection module 31, ON time control module 34, Current-Limiting Comparator 35, this driving signal exports switching tube M1 to via driving port DR, is used for the turn-on and turn-off of driving switch pipe M1.As a nonrestrictive example, in Fig. 5, driving signal generation module comprises or door 36 and rest-set flip-flop 37, and wherein, or the first input end of door 36 connects the output of ON time control module 34, the output of its second input connection Current-Limiting Comparator 35; The output of the set input S connection inductive current zero passage detection module 31 of rest-set flip-flop, the output of its RESET input R connection or door 36, its output produce the control end that drives signal and export switching tube M1 via driving port DR to.
In addition, can also comprise polarity modular converter (not shown in Fig. 5) in constant-current control circuit 30, the first input end of error amplifier 33 is connected with sample port CS via this polarity modular converter, in other words, the polarity modular converter is sampled to the load current of sample port input and the voltage of sampling gained is carried out the polarity conversion, and the voltage after the polarity conversion transfers to the first input end of error amplifier 33 by the first output of polarity modular converter.
The ground port GND of constant-current control circuit 30 is configured to receive floating ground voltage, and this floating ground voltage is different from the reference ground voltage (namely on the spot) of the input voltage of LED drive circuit.More specifically, the floating ground voltage that ground port GND receives makes the voltage difference between sample port CS and ground port GND fall into suitable, a lower scope, make control circuit 30 inside need not special high pressure modular converter, in the present embodiment, ground port GND is preferably the first end of connection constant current sampling resistor Rcs and the first end of inductance L, and sample port CS connects the second end of constant current sampling resistor Rcs.
Constant-current control circuit 30 in the present embodiment goes for various suitable peripheral circuits, for example decompression mode circuit.But, the application scenarios of having relatively high expectations for input harmonics, the decompression mode circuit has inborn inferior position, input voltage and output voltage near the time, the angle of flow of drive circuit diminishes, the inevitable variation of input harmonics, at input voltage specific output voltage hour, drive circuit even can't be worked.Therefore, as individual preferred embodiment, the peripheral circuit voltage boosting-reducing mode circuit of preferably sampling, its input voltage and output voltage can freely define, and it is best that input harmonics and power coefficient can both reach.
The below is described in detail peripheral circuit.The AC signal of 38 pairs of inputs of rectifier bridge is carried out rectification and is produced input signal; The control end of switching tube M1 connects the driving port DR of constant-current control circuit 30, and its first power termination is received this input voltage, and its second power end connects the current limliting port ILIM of constant-current control circuit 30 and the first end of current limliting sampling resistor RILIM; The second end of current limliting sampling resistor RILIM connects ground port GND, the first end of constant current sampling resistor Rcs and the first end of inductance L of constant-current control circuit 30; The first end of constant current sampling resistor Rcs connects ground port GND, the second end of current limliting sampling resistor RILIM and the first end of inductance L, and the second end of constant current sampling resistor Rcs connects the negative pole of sample port CS and sustained diode 1; The first end of inductance L connects the second end of current limliting sampling resistor RILIM and the first end of constant current sampling resistor Rcs, the second end ground connection of inductance L (reference of above-mentioned input voltage ground on the spot, i.e.); The negative pole of sustained diode 1 connects the second end of sample port CS and constant current sampling resistor Rcs, its anodal first end that connects output capacitance C1; The first end of output capacitance C1 connects the positive pole of sustained diode 1, its second end ground connection (on the spot), and output capacitance C1 can be configured in parallel with load LED; The first end ground connection (on the spot) of the first zero passage detection resistance R 1, its second end connects the zero passage detection port ZCD of constant-current control circuit 30; The first end of the second zero passage detection resistance R 2 connects the second end of the first zero passage detection resistance R 1, and its second end connects the ground port (namely connecting floating ground) of constant-current control circuit 30.
Wherein, sample port CS Direct Sampling load current, current limliting port ILIM is the electric current of sampling switch pipe M1, and when realizing that high constant current is controlled, also effective limit switch pipe M1 peak inrush current, guarantee whole LED drive circuit trouble free service.Need to prove, in this article, sample port CS Direct Sampling load current refers to sample port CS and without switching tube M1, load current is sampled.Furthermore, ground port GND and sample port CS are connected to the two ends of the constant current sampling resistor Rcs that connects with load.This constant current sampling resistor Rcs and load are connected on the same side of switching tube M1, in other words, do not comprise switching tube M1 on the series via between constant current sampling resistor Rcs and load.
After LED drive circuit powers on, at first conducting of switching tube M1, inductive current rises, the ON time of the voltage determine switch pipe M1 of compensation port COMP; After switching tube M1 closed, inductive current descended, when inductive current drops to zero current, trailing edge appears in the input voltage of inductive current zero passage detection module 31, inductive current zero passage detection module 31 is output as low, and set rest-set flip-flop 37 makes switching tube M1 open-minded.When load short circuits or LED drive circuit startup, inductive current can not stop to rise, and this moment, Current-Limiting Comparator 35 meetings to set point, ensured whole LED drive circuit work safety with the current limit of switching tube M1.
Current-Limiting Comparator 35 compares voltage and second reference voltage Vref 2 at current limliting sampling resistor RILIM two ends; after in case the voltage at current limliting sampling resistor RILIM two ends surpasses the second reference voltage Vref 2; the output signal of Current-Limiting Comparator 35 via or door 36 reset terminal that enters rest-set flip-flop 37; output signal to rest-set flip-flop 37 resets; thereby on-off switching tube M1 realizes current-limiting protection.
Fig. 6 is the work wave of LED drive circuit shown in Figure 5, therefrom can find out, when inductive current is zero, the output signal of inductive current zero passage detection module 31 is logic high, set rest-set flip-flop 37, the output signal of rest-set flip-flop 37 is logic high, make switching tube M1 open-minded, and then the earth potential that the ground port GND that makes constant-current control circuit 30 receives equals input voltage, this moment, inductive current rose, voltage by compensation port COMP is determined ON time in ON time control module 34, voltage and the ON time of compensation port COMP are directly proportional, when the output signal of ON time control module 34 is logic high, the output signal zero clearing of rest-set flip-flop 37, switching tube M1 closes, and the earth potential of the ground port GND of constant-current control circuit 30 becomes the reference ground of input signal, and then inductive current descends, when inductive current dropped to zero, the output signal of inductive current zero passage detection module 31 was logic high again, and switching tube M1 is open-minded once again, and one-period finishes.
During normal operation, compensation port COMP can external integrating capacitor C2, guarantees that the output voltage V comp of error amplifier 33 in single ac cycle is substantially constant, thereby realizes that permanent ON time controls, thereby obtains high power factor and low input harmonics.
In addition, as long as guarantee that the gain of error amplifier 33 is enough large, the gain of whole feedback loop just guaranteed, preferred peripheral components syndeton in addition, and the sample port CS load current of being sampled is finally realized the high constant current accuracy of system.
The use of inductive current zero passage detection module 31 makes the LED drive circuit of the present embodiment can be operated in critical conduction mode, thereby is conducive to improve the job stability of LED drive circuit, reduces the conversion power consumption, realizes high conversion efficiency.
Fig. 7 shows the structural representation of the LED drive circuit in the second embodiment, its structure and LED drive circuit shown in Figure 5 are basic identical, difference is the inductive current zero passage detection module 31 in constant-current control circuit 30 in the first embodiment is replaced with timer 39 in the second embodiment, and the first zero passage detection resistance R 1 in peripheral circuit and the second zero passage detection resistance R 2 are removed.In a second embodiment, drive the signal generation module and come control switch pipe M1 conducting according to the output signal of timer 39.
Fig. 8 shows the structural representation of the LED drive circuit in the 3rd embodiment, comprising: constant-current control circuit 50, switching tube M1, constant current sampling resistor Rcs, inductance L, sustained diode 1, output capacitance C1, the first zero passage sampling resistor R1, the second zero passage sampling resistor R2, rectifier bridge 58.Wherein, constant-current control module 50 has zero passage detection port ZCD, drives port DR, sample port CS, port GND and compensation port COMP, it comprises with lower module: inductive current zero passage detection module 51, polarity modular converter 52, error amplifier 53, ON time control module 54, Current-Limiting Comparator 55 or door 56 and rest-set flip-flop 57.
Compare with embodiment shown in Figure 5, in embodiment shown in Figure 7, constant-current control circuit 50 has saved current limliting port ILIM, and peripheral circuit has saved current limliting sampling resistor RILIM, change the connected mode of constant current sampling resistor Rcs, comprised polarity modular converter 52 in constant-current control circuit 50 in addition.Polarity modular converter 52 is via sample port CS sampling load current, it has the first output and the second output, wherein the first output is exported the first output voltage signal Vsense1, second output the second output voltage signal Vsense2, the first output voltage signal Vsense1 is the component of inductive current in decline cycle, represent load current signal, the second output voltage signal Vsense2 directly represents inductive current.The first output voltage signal Vsense1 transfers to an input of error amplifier 53, compares with the first reference voltage Vref 1, is used for constant current and controls; The second output voltage signal Vsense2 transfers to an input of Current-Limiting Comparator 55, compares with the second reference voltage Vref 2, is used for current-limiting protection.
Adopt circuit structure shown in Figure 8, can omit current limliting port ILIM and corresponding current limliting sampling resistor by multiplexing sample port CS.
Fig. 9 is the work wave of LED drive circuit shown in Figure 8, by the sampling load current, polarity modular converter 52 generates the voltage relevant to load current signal, and utilizes error amplifier 53 that itself and the first reference voltage Vref 1 are carried out the error amplification, finally realizes constant current control.The circuit structure of other parts of LED drive circuit shown in Figure 8 and operation principle and LED drive circuit shown in Figure 5 are similar, and more particular contents please refer to the associated description of previous embodiment.
Figure 10 shows the structural representation of the LED drive circuit of the 4th embodiment, its structure and LED drive circuit shown in Figure 8 are basic identical, difference is the inductive current zero passage detection modules 51 in constant-current control circuit in the 3rd embodiment 50 are replaced with counter 59 in the 4th embodiment, and the first zero passage detection resistance R 1 in peripheral circuit and the second zero passage detection resistance R 2 are removed.In the 4th embodiment, drive the signal generation module and come control switch pipe M1 conducting according to the output signal of timer 59.
In above-mentioned the first embodiment to the four embodiment, peripheral circuit all adopts the voltage boosting-reducing pattern, but be to be understood that, it is only preferred version that the constant-current control circuit that provides in this case matches with the peripheral circuit of voltage boosting-reducing pattern, and this constant-current control circuit equally also goes for the peripheral circuit of decompression mode.
With reference to Figure 11, the structural representation of LED drive circuit that it shows the decompression mode of the 5th embodiment comprises: constant-current control circuit 60, switching tube M1, constant current sampling resistor Rcs, inductance L, sustained diode 1, output capacitance C1, the first zero passage detection resistance R 1, the second zero passage detection resistance R 2, rectifier bridge 68.Wherein constant-current control circuit 60 have zero passage detection port ZCD, drive port DR, sample port CS, port GND, compensation port COMP, constant-current control circuit 60 comprises with lower module: inductive current zero passage detection module 61, error amplifier 63, ON time control module 64, Current-Limiting Comparator 65 and drive the signal generation module.Similar with previous first to fourth embodiment, the driving signal generation module in the 5th embodiment also comprises or door 66 and rest-set flip-flop 67.
Wherein, the connected mode of constant-current control circuit 60 and operation principle and previous embodiment are similar.In the 5th embodiment, the connected mode of peripheral circuit is as follows: 68 pairs of input voltages of rectifier bridge carry out rectification and produce input signal; The control end of switching tube M1 connects the driving port DR of constant-current control circuit 60, and its first power end connects the output of rectifier bridge 68, and its second power end connects the first end of constant current sampling resistor Rcs and the ground port GND of constant-current control circuit 60; The second end of constant current sampling resistor Rcs connects the sample port CS of constant-current control circuit 60 and the first end of inductance L; The second end of inductance L connects the first end of output capacitance C1; The second end ground connection of output capacitance C1; The negative pole of sustained diode 1 connects the first end of constant current sampling resistor Rcs, plus earth.
Need to prove, above embodiment is only example, those skilled in the art are to be understood that, the connected mode of the parts such as switching tube M1, sustained diode 1, constant current sampling resistor Rcs, inductance L, current limliting sampling resistor RILIM, the type of switching tube M1, the timer type in the ON time control module etc. can be carried out suitably change, under the prerequisite of the application's spirit, can form different specific embodiments by various compound mode.
Although the utility model with preferred embodiment openly as above; but it is not to limit the utility model; any those skilled in the art are not within breaking away from spirit and scope of the present utility model; can make possible change and modification, therefore protection range of the present utility model should be as the criterion with the scope that the utility model claim is defined.
Claims (18)
1. the constant-current control circuit of a LED drive circuit, have the port of driving, sample port and ground port, it is characterized in that, described constant-current control circuit comprises:
Error amplifier, its first input end directly receives load current via described sample port, and its second input receives the first default reference voltage;
The ON time control module, its input is connected with the output of described error amplifier, determines ON time according to the voltage that the output of described error amplifier is exported;
Drive the signal generation module, generate the driving signal of the switching tube that is used for the shutoff LED drive circuit according to the output signal of described ON time control module, described driving signal is exported via described driving port;
Wherein, described ground port arrangement is for receiving floating ground voltage, and described floating ground voltage is different from the reference ground voltage of the input voltage of described LED drive circuit.
2. constant-current control circuit according to claim 1, it is characterized in that, also comprise: the polarity modular converter, the first input end of described error amplifier receives described load current via this polarity modular converter from described sample port, described polarity modular converter is sampled to this load current and the voltage of sampling gained is carried out polarity conversion, and the first output of described polarity modular converter is connected with the first input end of described error amplifier.
3. constant-current control circuit according to claim 1, it is characterized in that, described constant-current control circuit also has the zero passage detection port, described constant-current control circuit also comprises: inductive current zero passage detection module, inductive current to described zero passage detection port input carries out zero passage detection, and described driving signal generation module generates according to the output signal of described inductive current zero passage detection module the driving signal that is used for the described switching tube of conducting.
4. constant-current control circuit according to claim 1, is characterized in that, also comprises: timer, described driving signal generation module generates according to the output signal of described timer the driving signal that is used for the described switching tube of conducting.
5. constant-current control circuit according to claim 1, is characterized in that, also comprises: Current-Limiting Comparator, and its first input end receives the current limliting sampled voltage, and its second input receives the second default reference voltage.
6. constant-current control circuit according to claim 5, is characterized in that, described constant-current control circuit also has the current limliting port, and the first input end of described Current-Limiting Comparator receives described current limliting sampled voltage via described current limliting port.
7. constant-current control circuit according to claim 5, it is characterized in that, also comprise: the polarity modular converter, the first input end of described error amplifier receives described load current via this polarity modular converter from described sample port, described polarity modular converter carries out the polarity conversion to this load current, the first output of described polarity modular converter is connected with the first input end of described error amplifier, described polarity modular converter also has the second output, the first input end of described Current-Limiting Comparator receives described current limliting sampled voltage from the second output of described polarity modular converter.
8. constant-current control circuit according to claim 5, it is characterized in that, described constant-current control circuit also has the zero passage detection port, described constant-current control circuit also comprises: inductive current zero passage detection module, inductive current to described zero passage detection port input carries out zero passage detection, described driving signal generation module generates according to the output signal of described inductive current zero passage detection module the driving signal that is used for the described switching tube of conducting, and described driving signal generation module comprises:
Or door, its first input end connects the output of described ON time control module, and its second input connects the output of described Current-Limiting Comparator;
Rest-set flip-flop, its set input connects the output of described inductive current zero passage detection module, and its RESET input connects output described or door, and its output produces described driving signal.
9. constant-current control circuit according to claim 5, it is characterized in that, also comprise: timer, described driving signal generation module generates according to the output signal of described timer the driving signal that is used for the described switching tube of conducting, and described driving signal generation module comprises:
Or door, its first input end connects the output of described ON time control module, and its second input connects the output of described Current-Limiting Comparator;
Rest-set flip-flop, its set input connects the output of described timer, and its RESET input connects output described or door, and its output produces described driving signal.
10. constant-current control circuit according to claim 1, is characterized in that, described constant-current control circuit also comprises the compensation port, and the output of described error amplifier is connected and is configured to via integrating capacitor ground connection with this compensation port.
11. a LED drive circuit is characterized in that, comprise the described constant-current control circuit of any one in claim 1 to 10 and with the peripheral circuit of its coupling.
12. LED drive circuit according to claim 11 is characterized in that, described peripheral circuit is the voltage boosting-reducing mode circuit.
13. LED drive circuit according to claim 12 is characterized in that, described peripheral circuit comprises:
Switching tube, its control end connects the driving port of described constant-current control circuit, and its first power termination is received input voltage;
The constant current sampling resistor, its first end connects the second power end of described switching tube;
Inductance, its first end connects the first end of described constant current sampling resistor, its second end ground connection;
Fly-wheel diode, its negative pole connects the second end of described constant current sampling resistor;
Output capacitance, its first end connects the positive pole of described fly-wheel diode, its second end ground connection;
Wherein, the ground port of described constant-current control circuit connects in the first end of described constant current sampling resistor and the second end, and the sample port of described constant-current control circuit connects the first end of described constant current sampling resistor and another in the second end.
14. LED drive circuit according to claim 12 is characterized in that, described peripheral circuit comprises:
Switching tube, its control end connects the driving port of described constant-current control circuit, and its first power termination is received input voltage;
The constant current sampling resistor, its first end connects the second power end of described switching tube;
Inductance, its first end connects the second end of described constant current sampling resistor, its second end ground connection;
Fly-wheel diode, its negative pole connects the first end of described constant current sampling resistor;
Output capacitance, its first end connects the positive pole of described fly-wheel diode, its second end ground connection;
Wherein, the ground port of described constant-current control circuit connects in the first end of described constant current sampling resistor and the second end, and the sample port of described constant-current control circuit connects the first end of described constant current sampling resistor and another in the second end.
15. LED drive circuit according to claim 13, it is characterized in that, described peripheral circuit also comprises: the current limliting sampling resistor, the first end of described constant current sampling resistor connects the second power end of described switching tube via this current limliting sampling resistor, the second power end of described switching tube also connects the current limliting port of described constant-current control circuit.
16. LED drive circuit according to claim 14 is characterized in that, the first input end of the Current-Limiting Comparator in described constant-current control circuit receives described current limliting sampled voltage from the second output of described polarity modular converter.
17. according to claim 13 or 14 described LED drive circuits is characterized in that, also comprise:
Rectifier bridge, outside AC signal produce described input voltage after via described rectifier bridge rectification.
18. according to claim 13 or 14 described LED drive circuits is characterized in that described output capacitance is configured in parallel with load LED.
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| CN2013201510229U CN203279254U (en) | 2013-03-28 | 2013-03-28 | LED drive circuit and its constant current control circuit |
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| CN2013201510229U CN203279254U (en) | 2013-03-28 | 2013-03-28 | LED drive circuit and its constant current control circuit |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103152956A (en) * | 2013-03-28 | 2013-06-12 | 杭州士兰微电子股份有限公司 | LED (Light Emitting Diode) driving circuit and constant-current control circuit thereof |
| CN104270861A (en) * | 2014-09-30 | 2015-01-07 | 成都芯源系统有限公司 | LED driver, control circuit and LED driving method |
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| CN103152956A (en) * | 2013-03-28 | 2013-06-12 | 杭州士兰微电子股份有限公司 | LED (Light Emitting Diode) driving circuit and constant-current control circuit thereof |
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