CN110831284B - LED driving power supply and controller thereof - Google Patents
LED driving power supply and controller thereof Download PDFInfo
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- CN110831284B CN110831284B CN201911158265.3A CN201911158265A CN110831284B CN 110831284 B CN110831284 B CN 110831284B CN 201911158265 A CN201911158265 A CN 201911158265A CN 110831284 B CN110831284 B CN 110831284B
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Abstract
The invention discloses an LED driving power supply and a controller thereof, wherein the controller comprises: the demagnetization detection module is used for detecting the drain voltage of the power switch tube when the power switch tube is turned off and judging whether the demagnetization of the inductor is finished according to the drain voltage of the power switch tube; the current detection module is used for detecting whether the current of the inductor is larger than a first preset value or not; the switch control module is used for controlling the power switch tube to be switched on when the demagnetization is judged to be finished; and when the current of the inductor is judged to be larger than a first preset value, controlling the power switch tube to be switched off. By implementing the technical scheme of the invention, an auxiliary winding does not need to be arranged for the inductor, and a voltage division network circuit of the auxiliary winding does not need to be arranged, so that the cost of the LED driving power supply is reduced, and the reliability of the LED driving power supply is improved.
Description
Technical Field
The invention relates to the field of LED illumination, in particular to an LED driving power supply and a controller thereof.
Background
In the current LED driving power supply structure, the non-isolated step-down driving structure is most widely used, because compared with other circuit structures, the non-isolated step-down circuit structure is simpler, the required peripheral circuit is simpler, and the LED driving power supply realized by using the circuit structure is lower in cost and high in reliability.
The most widely used non-isolated step-down constant current driving circuit structure is shown in fig. 1, and the circuit adopts a critical operating mode (i.e., a power switching tube inside the transformer is turned on immediately after demagnetization of the transformer is finished, the transformer is charged again, and a new operating cycle is started). In order to accurately detect the end of demagnetization of the transformer 109, the circuit structure adopts the auxiliary winding 105 to detect the demagnetization time of the main winding 109 of the transformer, and combines the working sequence waveform shown in figure 2, when the driving signal GD of the power switch tube changes from high level to low level, the primary winding 109 of the transformer starts to demagnetize, when the demagnetization of the main winding 109 is over, the Drain terminal (Drain) of the power switch begins to enter the resonance phase, and a similar waveform is detected at the same terminal of the corresponding auxiliary winding 105, the waveform is divided by a voltage division network (composed of a resistor 106 and a resistor 107) and then input to a ZCD pin, the controller 103 judges that the demagnetization of the transformer is finished according to the sudden change of the slope of the waveform on the ZCD pin, and then the internal power switch tube driving signal GD is immediately changed from low level to high level, the power switch tube is conducted, and a new working period is started.
As can be seen from the circuit of the LED driving power supply shown in fig. 1, the circuit structure is complex, the transformer needs two windings, which increases the complexity of the manufacturing process of the transformer, and a voltage dividing network circuit for an auxiliary winding is also needed, which eventually increases the cost of the power supply and reduces the reliability of the circuit.
Disclosure of Invention
The present invention provides an LED driving power supply and a controller thereof, aiming at the above-mentioned defects of high cost and low reliability in the prior art.
The technical scheme adopted by the invention for solving the technical problems is as follows: a controller of an LED driving power supply is constructed and used for controlling a power switch tube, a drain electrode of the power switch tube is respectively connected with an anode of a fly-wheel diode and a first end of an inductor, a second end of the inductor is connected with a negative end of an LED lamp bead, a cathode of the fly-wheel diode is connected with a positive end of the LED lamp bead, and the controller comprises:
the demagnetization detection module is used for detecting the drain voltage of the power switch tube when the power switch tube is turned off and judging whether the demagnetization of the inductor is finished according to the drain voltage of the power switch tube;
the current detection module is used for detecting whether the current of the inductor is larger than a first preset value or not;
the switch control module is used for judging the end of demagnetization when the detected drain electrode voltage is less than a second reference voltage generated according to the drain electrode voltage, and controlling the power switch tube to be switched on; and when the current of the inductor is judged to be larger than a first preset value, controlling the power switch tube to be switched off.
Preferably, the switch control module includes RS trigger and buffer, wherein, the set end of RS trigger is connected the output of demagnetization detection module, the RS trigger resets the end and connects the output of current detection module, the positive output of RS trigger is connected the input of buffer, the output of buffer is connected the grid of power switch pipe.
Preferably, the demagnetization detecting module includes:
the sampling unit is used for sampling the drain voltage of the power switch tube;
the comparison unit is used for comparing the sampling voltage with a second reference voltage after the power switch tube is switched off and judging whether the sampling voltage is smaller than the second reference voltage or not;
and the first pulse generating unit is used for generating a first pulse signal when the sampling voltage is smaller than the second reference voltage.
Preferably, the sampling unit includes a first resistor and a second resistor, wherein a first end of the first resistor is connected to the drain of the power switch tube, and a second end of the first resistor is grounded through the second resistor.
Preferably, the comparing unit includes a first comparator and a MOS transistor, wherein an inverting input terminal of the first comparator is connected to the output terminal of the sampling unit, a non-inverting input terminal of the first comparator inputs the second reference voltage, a gate of the MOS transistor is connected to a positive output terminal of the RS flip-flop, a drain of the MOS transistor is connected to the non-inverting input terminal of the first comparator, and a source of the MOS transistor is grounded.
Preferably, the comparing unit further includes a capacitor and a negative voltage compensator, wherein a first end of the capacitor is connected to the output end of the sampling unit and the input end of the negative voltage compensator, respectively, a second end of the capacitor is grounded, and an output end of the negative voltage compensator is connected to the non-inverting input end of the first comparator.
Preferably, the comparing unit is configured to delay for a preset time after the power switching tube is turned off, compare the sampled voltage with a second reference voltage, and determine whether the sampled voltage is smaller than the second reference voltage.
Preferably, the comparing unit further includes a delay circuit, a second pulse generator and a sampling switch, wherein an input end of the delay circuit is connected to the inverted output end of the RS flip-flop, an output end of the delay circuit is connected to an input end of the second pulse generator, an output end of the second pulse generator is connected to a control end of the sampling switch, a first end of the sampling switch is connected to an output end of the sampling unit, and a second end of the sampling switch is connected to a first end of the capacitor.
The invention also constructs an LED driving power supply which is connected with the LED lamp beads and comprises: the LED lamp comprises a freewheeling diode, an inductor, a current detection resistor, a power switch tube and the controller, wherein the cathode of the freewheeling diode and the positive end of the LED lamp bead are respectively connected with the positive end of input voltage, the drain electrode of the power switch tube is connected with the anode of the freewheeling diode and the first end of the inductor, the second end of the inductor is connected with the negative end of the LED lamp bead, and the current detection end of the controller is grounded through the current detection resistor.
Preferably, the LED lamp also comprises a rectifier bridge, and the positive output end of the rectifier bridge is respectively connected with the cathode of the freewheeling diode and the positive end of the LED lamp bead.
According to the technical scheme, the demagnetization time of the inductor is judged by directly detecting the voltage of the drain electrode of the power switch tube, specifically, according to the working principle of the voltage reduction type circuit, when the demagnetization of the inductor is finished, the voltage of the drain electrode of the power switch tube is suddenly reduced, so that whether the demagnetization of the inductor is finished or not is judged by detecting the voltage of the drain electrode of the power switch tube, and whether the power switch tube is switched on or not is further determined. The control mode does not need to arrange an auxiliary winding for the inductor and a voltage division network circuit of the auxiliary winding, reduces the cost of the LED driving power supply, and improves the reliability of the LED driving power supply.
Drawings
The invention will be further described with reference to the accompanying drawings and examples, in which:
fig. 1 is a circuit configuration diagram of a conventional LED driving power supply;
FIG. 2 is a timing diagram illustrating operation of a conventional LED driving power supply;
FIG. 3 is a circuit diagram of a first embodiment of the LED driving power supply of the present invention;
FIG. 4 is a circuit diagram of a second embodiment of the LED driving power supply of the present invention;
fig. 5 is a timing diagram illustrating the operation of the LED driving power supply according to the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Fig. 3 is a circuit structure diagram of an LED driving power supply according to a first embodiment of the present invention, where the LED driving power supply is connected to an LED lamp bead 308, and the LED driving power supply specifically includes: the rectifier bridge 301, the freewheeling diode 304, the inductor 306, the current detection resistor 305, and the controller 303 has a power switch tube built therein, but in other embodiments, the power switch tube may be disposed on the periphery of the controller 303. Two input ends of the rectifier bridge 301 are connected to two ends of the ac power supply 300, a positive output end of the rectifier bridge 301 is connected to a cathode of the freewheeling diode 304, a positive end of the LED lamp bead 308, and a power supply end (HV) of the controller 303, respectively, and a negative output end of the rectifier bridge 301 is grounded. The Drain terminal (Drain) of the controller 303, that is, the Drain of the power switch tube, is connected to the anode of the freewheeling diode 304 and the first terminal of the inductor 306, the second terminal of the inductor 306 is connected to the negative terminal of the LED lamp bead 308, and the current detection terminal (CS) of the controller 303 is grounded through the current detection resistor 305. In addition, the first electrolytic capacitor 302 is connected between two output ends of the rectifier bridge 301, the second electrolytic capacitor is connected between two ends of the LED lamp bead 308, and the resistor 307 is connected between two ends of the LED lamp bead 308. It should be noted that, in other embodiments, the LED driving power source may be directly connected to the dc power source, and in this case, the rectifier bridge 301 is not required, which is also within the protection scope of the present invention.
In this embodiment, when the controller 303 controls the power switch tube to be turned on, the output current of the rectifier bridge 301 forms a loop through the LED lamp bead 308, the inductor 306, the power switch tube, and the current detection resistor 305; when the controller 303 controls the power switch tube to be turned off, the inductor 306 forms a follow current loop through the follow current diode 304 and the LED lamp bead 308.
In addition, the controller 303 includes: the switch comprises a demagnetization detection module, a current detection module and a switch control module, wherein the demagnetization detection module is used for detecting the drain voltage of the power switch tube when the power switch tube is switched off and judging whether the demagnetization of the inductor is finished or not according to the drain voltage of the power switch tube; the current detection module is used for detecting whether the current of the inductor is larger than a first preset value or not; the switch control module is used for controlling the power switch tube to be switched on when the demagnetization is judged to be finished; and when the current of the inductor is judged to be larger than the first preset value, the power switch tube is controlled to be turned off.
In the technical scheme of the embodiment, the demagnetization time of the inductor is judged by directly detecting the voltage of the drain electrode of the power switching tube, specifically, according to the working principle of the step-down circuit, when the demagnetization of the inductor is finished, the voltage of the drain electrode of the power switching tube is suddenly reduced, and a resonance waveform appears, so that whether the demagnetization of the inductor is finished or not can be judged by detecting the voltage of the drain electrode of the power switching tube, and whether the power switching tube is switched on or not can be further determined. The control mode does not need to arrange an auxiliary winding for the inductor and a voltage division network circuit of the auxiliary winding, reduces the cost of the LED driving power supply, and improves the reliability of the LED driving power supply.
Further, the demagnetization detection module comprises: the power switch comprises a sampling unit, a comparison unit and a first pulse generation unit, wherein the sampling unit is used for sampling the drain voltage of a power switch tube; the comparison unit is used for comparing the sampling voltage with a second reference voltage after the power switch tube is turned off and judging whether the sampling voltage is smaller than the second reference voltage; the first pulse generating unit is used for generating a first pulse signal when the sampling voltage is smaller than the second reference voltage. Preferably, the comparing unit is configured to delay a preset time after the power switch is turned off, compare the sampled voltage with the second reference voltage, and determine whether the sampled voltage is smaller than the second reference voltage.
Fig. 4 is a circuit structure diagram of a second embodiment of the LED driving power supply of the present invention, and compared with the embodiment shown in fig. 3, the LED driving power supply of this embodiment has the same peripheral circuits of the controller 303, which are not described herein again, and only the internal circuit structure of the controller 303 is described below:
in this embodiment, the current detection module includes a second comparator 410, and the inverting input terminal of the second comparator 410 inputs a first reference voltage (Vref), and the non-inverting input terminal of the second comparator 410 is connected to the connection point of the power switch 415 and the current detection resistor 305, i.e., at the CS position.
In this embodiment, the switch control module includes an RS flip-flop 411 and a buffer 414, where a set terminal (S) of the RS flip-flop 411 is connected to an output terminal of the demagnetization detection module, a reset terminal (R) of the RS flip-flop 411 is connected to an output terminal of the current detection module, a positive output terminal of the RS flip-flop 411 is connected to an input terminal of the buffer 414, and an output terminal of the buffer 414 is connected to a gate of the power switch 415.
In this embodiment, the sampling unit of the demagnetization detection module includes a first resistor 406 and a second resistor 409, where the first resistor 406 is a high voltage resistor and the second resistor 409 is a low voltage resistor. The first end of the first resistor 406 is connected to the drain of the power switch 415, and the second end of the first resistor 406 is grounded through the second resistor 409. In a specific application, since the highest value of the drain voltage of the power switch tube 415 is the output voltage of the rectifier bridge 301, when the input voltage of the ac power supply 300 is 265V (the highest voltage of the ac power), the highest value of the drain voltage of the power switch tube 415 reaches 374V, so the detection circuit inside the chip must be able to withstand at least 400V. Based on this, the withstand voltage level of the first resistor 406 is sufficiently high, and the ratio of the first resistor 406 to the second resistor 409 is sufficiently large. The sampling unit samples the drain voltage of the power switch tube 415 through a voltage division network formed by the first resistor 406 and the second resistor 409, so that an output signal of a high-voltage signal of the drain of the power switch tube 415 after passing through the voltage division network is a voltage that can be borne by the controller 303.
In this embodiment, the first pulse generating unit of the demagnetization detecting module is a first pulse generator 402. The comparing unit of the demagnetization detecting module includes a first comparator 403, a MOS transistor 407, a capacitor 408, a negative voltage compensator 404, a delay circuit 412, a second pulse generator 413, and a sampling switch 405. The inverting input terminal of the first comparator 403 is connected to the output terminal of the sampling unit, i.e. the connection point of the first resistor 406 and the second resistor 409. The output terminal of the sampling unit is also connected to the non-inverting input terminal of the first comparator 403 through a sampling switch 405 and a negative voltage compensator 404. The gate of the MOS transistor 407 is connected to the positive output terminal of the RS flip-flop 411, the drain of the MOS transistor 407 is connected to the input terminal of the negative voltage compensator 404 and the first terminal of the capacitor 408, the source of the MOS transistor 407 is grounded, and the second terminal of the capacitor 408 is grounded. The input terminal of the delay circuit 412 is connected to the inverted output terminal of the RS flip-flop 411, the output terminal of the delay circuit 412 is connected to the input terminal of the second pulse generator 413, and the output terminal of the second pulse generator 413 is connected to the control terminal of the sampling switch 405.
Finally, it should be noted that, in other embodiments, the circuit structure shown in fig. 4 may be modified or changed, for example, the non-inverting input terminal of the first comparator 403 may also directly input the second reference voltage, and in this case, the capacitor 408 and the negative voltage compensator 404 may not be required; the drain of the MOS transistor 407 may also be connected to the non-inverting input terminal of the first comparator 403 or the output terminal of the sampling unit; the delay circuit 412 and the second pulse generator 413 are replaced with other devices of equivalent functions.
The operation principle of the LED driving power supply of this embodiment in conjunction with fig. 5 is explained as follows:
in the sampling unit of the demagnetization detection module, the sampling unit samples the drain voltage of the power switch tube 415 through a voltage division network composed of a first resistor 406 and a second resistor 409, and the sampling result is input into the comparison unit of the demagnetization detection module.
In the comparing unit of the demagnetization detecting module, after a time delay after the inductor 306 starts demagnetization, the first comparator 403 loads the output voltage of the sampling unit onto the capacitor 408, and takes the voltage on the capacitor 408 as the second reference voltage VC for comparison with the output voltage VR of the sampling unit, as can be seen from the waveform 504 shown in fig. 5, when the inductor 306 demagnetization ends, the output voltage VR of the sampling unit rapidly decreases along with the rapid decrease of the drain voltage of the power switch 415, so that the demagnetization time can be determined by comparing the output voltage VR of the sampling unit with the second reference voltage VC.
The second comparator 410 is used for cycle-by-cycle peak current limiting, i.e. when the power switch 415 is turned on, the current IL of the inductor 306 gradually increases, as shown by the waveform 502 in fig. 5, so that the voltage across the current detection resistor 305 gradually increases. When the voltage across the current detection resistor 305 exceeds the internal reference voltage Vref of the controller 303, the second comparator 410 outputs a high level to the reset terminal (S) of the RS flip-flop 411, and the positive output terminal of the RS flip-flop 411 outputs a low level, and the low level signal outputs a low level gate control signal (GD) to the power switch 415 after passing through the buffer 414, as shown by a waveform 500 in fig. 5, so as to control the power switch 415 to turn off.
When the power switch 415 is turned off, the inductor 306 starts to demagnetize, i.e., the inductor 306 starts to freewheel through the freewheeling diode 304. Also, at the instant the power switch 415 is turned off, the drain voltage of the power switch 415 changes from low level to high level and remains high for the entire demagnetization time, as shown by the waveform 501 in fig. 5. Because the inductor 306, the freewheeling diode 304, the LED lamp bead 308, and the like have equivalent series resistance, the current IL flowing through the inductor 306 becomes smaller and smaller as the demagnetization time of the inductor 306 becomes longer, and therefore the drain voltage of the power switch 415 decreases slightly as the inductor 306 demagnetizes. Considering that the drain voltage is slightly reduced in demagnetization, the voltage on the capacitor 408 must pass through a negative voltage compensator 404 before being input to the non-inverting input terminal of the first comparator 403, so as to ensure that the inductor 306 does not become smaller than the voltage on the capacitor 408 due to the slight reduction of the drain voltage in the entire demagnetization process, thereby causing malfunction. After the voltage of the capacitor 408 is compensated by the negative voltage, the voltage VC input to the non-inverting input terminal of the first comparator 403 is smaller than the voltage VC on the capacitor 408 by Δ V, so that it is ensured that the voltage VR at the inverting input terminal of the first comparator 403 is greater than the voltage VC at the non-inverting input terminal before the demagnetization of the inductor 306 is completed, and thus, an erroneous determination cannot be made.
In addition, at the moment when the power switch 415 is turned off (i.e. at the moment when the inductor 306 starts to demagnetize), the drain voltage of the power switch 415 will have a high-frequency oscillation waveform (not shown in the figure) in a short time when the voltage changes from low level to high level, so the sampling time point must avoid the oscillation stage end to avoid the occurrence of mis-sampling. The scheme of this embodiment is to delay a period of time after the power switch 415 is turned off, and then generate a pulse signal SP, as shown by a waveform 503 in fig. 5, where the pulse signal SP is used to drive the control terminal of the sampling switch 405, load the output voltage of the sampling unit at this time onto the capacitor 408, and then perform comparison. It should be understood that the same function can be achieved by more than one of the above methods, and any method that can achieve this delayed sampling effect is within the scope of this patent. The sampling pulse signal SP is an output signal of the second pulse generator 413, and the sampling delay time is a delay time generated by the delay circuit 412. The input signal of the delay circuit 412 is the inverse output signal of the RS flip-flop 411 (i.e. the inverse of the gate control signal GD of the power switch 415), the output signal of the delay circuit 412 is used as the input signal of the second pulse generator 413, and the second pulse generator 413 generates a pulse signal SP according to the rising edge of the signal, so as to control the sampling switch 405.
In a switching period, when the power switch 415 is turned on (i.e. GD is at a high level), the voltage on the capacitor 408 is reset to 0 by the MOS transistor 407, and the current IL of the inductor 306 linearly increases, and the voltage on the current detection resistor 305 (the voltage at the CS terminal) also linearly increases, when the voltage reaches the first reference voltage (Vref), the second comparator 410 outputs a high level, the high level signal is input to the reset terminal of the RS flip-flop 411, the positive output terminal of the RS flip-flop outputs a low level, and the low level signal outputs a low level gate control signal GD after passing through the buffer 414, so as to control the power switch 415 to turn off, and the demagnetization process of the inductor 306 starts. In addition, when the power switch 415 is turned off, the output terminal of the RS flip-flop 411 changes from low level to high level, the signal passes through the delay circuit 412 to generate a signal delayed for a period of time with respect to the output signal of the output terminal of the RS flip-flop 411, the signal passes through the second pulse generator 413 to generate a pulse signal SP, the pulse signal SP controls the sampling switch 405 to be turned on, and when the sampling switch 405 is turned on, the output signal of the sampling unit (composed of the first resistor 406 and the second resistor 409) is loaded on the capacitor 408. The voltage on the capacitor 408 passes through the negative voltage compensator 404 to generate a second reference voltage, and is input to the non-inverting input terminal of the first comparator 403. When the inductor 306 is demagnetized, the drain voltage of the power switch 415 is decreased instantaneously, and the drain voltage passes through the sampling unit and is input to the inverting input terminal of the first comparator 403. When the first comparator 403 detects that the voltage VR at the inverting input terminal is lower than the second reference voltage VC at the non-inverting input terminal, it is considered that the demagnetization of the inductor 306 is finished, the output terminal of the first comparator 403 outputs a high level, the high level generates a pulse signal ZCD after passing through the first pulse generator 402, as shown by a waveform 505 in fig. 5, the signal is input to the set terminal of the RS flip-flop 411 as a signal that the demagnetization of the inductor 306 is finished, the positive output terminal of the RS flip-flop 411 is reset to a high level, the high level controls the MOS transistor 407 to conduct, so as to reset the capacitor 408 to a 0 potential, and at the same time, the high level signal controls the power switch 415 to conduct again after passing through the buffer 414, and the next cycle starts.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.
Claims (9)
1. The utility model provides a controller of LED drive power supply for control power switch tube, just power switch tube's drain electrode connects freewheel diode's positive pole and the first end of inductance respectively, the second termination LED lamp pearl of inductance's negative terminal, freewheel diode's negative pole connects the positive terminal of LED lamp pearl, its characterized in that, the controller includes:
the demagnetization detection module is used for detecting the drain voltage of the power switch tube when the power switch tube is turned off and judging whether the demagnetization of the inductor is finished according to the drain voltage of the power switch tube;
the current detection module is used for detecting whether the current of the inductor is larger than a first preset value or not;
the switch control module is used for judging the end of demagnetization when the detected drain voltage is smaller than a second reference voltage generated according to the drain voltage and controlling the power switch tube to be switched on; when the current of the inductor is judged to be larger than a first preset value, the power switch tube is controlled to be turned off;
wherein, demagnetization detection module includes sampling unit and comparison unit, the comparison unit includes first comparator, MOS pipe, electric capacity and negative voltage compensator, wherein, the drain electrode of MOS pipe is connected the input of negative voltage compensator, the source ground connection of MOS pipe, the first end of electric capacity is connected respectively the output of sampling unit reaches the input of negative voltage compensator, the second end ground connection of electric capacity, the output of negative voltage compensator is connected the in-phase input of first comparator, the output of first comparator is demagnetized and is ended the signal.
2. The controller of the LED driving power supply according to claim 1, wherein the switch control module comprises an RS flip-flop (411) and a buffer (414), wherein a set terminal of the RS flip-flop (411) is connected to the output terminal of the demagnetization detection module, a reset terminal of the RS flip-flop (411) is connected to the output terminal of the current detection module, a positive output terminal of the RS flip-flop (411) is connected to the input terminal of the buffer (414), and an output terminal of the buffer (414) is connected to the gate of the power switch tube.
3. The controller of the LED driving power supply according to claim 2,
the demagnetization detection module comprises:
the sampling unit is used for sampling the drain voltage of the power switch tube;
the comparison unit is used for comparing the sampling voltage with the second reference voltage after the power switch tube is switched off and judging whether the sampling voltage is smaller than the second reference voltage or not;
and the first pulse generating unit is used for generating a first pulse signal when the sampling voltage is smaller than the second reference voltage.
4. The controller of the LED driving power supply according to claim 3, wherein the sampling unit comprises a first resistor (406) and a second resistor (409), wherein a first end of the first resistor (406) is connected to the drain of the power switch tube (415), and a second end of the first resistor (406) is grounded through the second resistor (409).
5. The controller of the LED driving power supply according to claim 3 or 4, wherein an inverting input terminal of the first comparator (403) is connected to the output terminal of the sampling unit, a non-inverting input terminal of the first comparator (403) inputs the second reference voltage, and a gate of the MOS transistor (407) is connected to a positive output terminal of the RS flip-flop (411).
6. The controller of the LED driving power supply according to claim 2,
and the comparison unit is used for delaying for a preset time after the power switch tube is turned off, then comparing the sampling voltage with the second reference voltage, and judging whether the sampling voltage is smaller than the second reference voltage.
7. The controller of the LED driving power supply according to claim 6, wherein the comparing unit further comprises a delay circuit (412), a second pulse generator (413) and a sampling switch (405), wherein an input terminal of the delay circuit (412) is connected to an inverted output terminal of the RS flip-flop, an output terminal of the delay circuit (412) is connected to an input terminal of the second pulse generator (413), an output terminal of the second pulse generator (413) is connected to a control terminal of the sampling switch (405), a first terminal of the sampling switch (405) is connected to an output terminal of the sampling unit, and a second terminal of the sampling switch (405) is connected to a first terminal of the capacitor (408).
8. The utility model provides a LED drive power supply, is connected with LED lamp pearl (308), its characterized in that includes: the controller (303) as claimed in any one of claims 1 to 7, wherein a cathode of the freewheeling diode (304) and a positive terminal of the LED lamp bead (308) are respectively connected to a positive terminal of an input voltage, a drain of the power switch is connected to an anode of the freewheeling diode (304) and a first terminal of the inductor (306), a second terminal of the inductor (306) is connected to a negative terminal of the LED lamp bead (308), and a current detection terminal of the controller (303) is grounded through the current detection resistor (305).
9. The LED driving power supply according to claim 8, further comprising a rectifier bridge (301), wherein a positive output terminal of the rectifier bridge (301) is connected to a cathode of the freewheeling diode (304) and a positive terminal of the LED lamp bead (308), respectively.
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| CN112351547B (en) * | 2020-12-04 | 2022-05-10 | 华源智信半导体(武汉)有限公司 | Intelligent adjusting method and system for driving LED |
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