CN201657407U - LED constant-current output circuit - Google Patents
LED constant-current output circuit Download PDFInfo
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- CN201657407U CN201657407U CN2010200024925U CN201020002492U CN201657407U CN 201657407 U CN201657407 U CN 201657407U CN 2010200024925 U CN2010200024925 U CN 2010200024925U CN 201020002492 U CN201020002492 U CN 201020002492U CN 201657407 U CN201657407 U CN 201657407U
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Abstract
The utility model relates to an LED constant-current output circuit, which is used in a step-up and step-down structure adopting hysteresis loop control. The LED constant-current output circuit comprises an input voltage sampling circuit, an sampling circuit of the sum of input and output current, a sampling circuit of the sum of input and output voltage, a current and voltage conversion circuit and a compensation algorithm circuit, wherein the current and voltage conversion circuit is connected with the sampling circuit of the sum of input and output current, and the compensation algorithm circuit is connected with the voltage sampling circuit, the sampling circuit of the sum of input and output voltage and the current and voltage conversion circuit. The LED constant-current output circuit realizes that LED output current can not be changed along with variation of input voltage on a condition of constant output voltage.
Description
Technical field
The utility model relates to circuit field, particularly relates to a kind of LED constant current output circuit.
Background technology
Now, shot-light is widely adopted in market or family, to be used for the specific target of throwing light on, can visually play outstanding role like this.This shot-light adopts Halogen lamp LED to realize.Because the luminous efficiency of Halogen lamp LED is the same with incandescent lamp to be very low, the life-span also had only about 2000 hours.
And the life-span of LED reaches 50,000 hours, and any in the market other lighting technology can't be reached.In addition, the effect of LED fluorescent tube is higher 5 to 10 times than conventional incandescent, thus Halogen lamp LED to be replaced gradually by LED be historical development trend.
LED as the problem that shot-light replacement Halogen lamp LED need solve is: LED can compatible rectifier for traditional shot-light (Halogen lamp LED) power supply as shot-light.Because what Halogen lamp LED used is AC adapter, what LED used is constant-current driving, alternating current need be converted to constant-current driving so LED replaces Halogen lamp LED as shot-light.
The LED shot-light replaces Halogen lamp LED general what adopt is buck Topoloty (buck topology) circuit diagram as shown in Figure 1 in the market.
But there are the following problems for above-mentioned solution: because the rectification of existing Halogen lamp LED rectifier output process rectifier bridge is the 12V direct current, the input power supply is the 12V direct current, can be at most 3 series LED power supplies.
Be more series LED power supplies if desired, must change Topology, in order to satisfy above requirement, Buck-Boost (buck) converter that the ring that stagnates is controlled is good a selection, the Buck-Boost Topology (buck topology) that generally uses has buck topological circuit figure as shown in Figure 2 now now.V among Fig. 2
IN, V
OAnd duty ratio D satisfies following relation: V
O/ V
IN=D/ (1-D) wherein, V
OBe output voltage;
V
INBe input voltage;
D is duty ratio (0＜D＜1).
When D＞0.5, V
O＞V
IN, promptly realize boost function; When D＜0.5, V
O＜V
IN, promptly realize buck functionality.
The LED output current of this moment is non-constant, and promptly under the output voltage controlled condition, output current can change with input voltage.
Therefore, how providing a kind of LED constant current output circuit, be used for stagnating and encircle the buck structure of control, make that the LED output current does not change with the change of input voltage under the output voltage controlled condition, is those skilled in the art's technical issues that need to address.
The utility model content
The purpose of this utility model provides a kind of LED constant current output circuit, is implemented under the output voltage controlled condition, and the LED output current does not change with the change of input voltage.
The purpose of this utility model provides a kind of LED constant current output circuit, is used for the buck structure of stagnant ring control;
Described circuit comprises input voltage sample circuit, input and output electric current sum sample circuit, input and output voltage sum sample circuit;
With, the current-to-voltage converting circuit that links to each other with described input and output electric current sum sample circuit, and the backoff algorithm circuit that links to each other with described current-to-voltage converting circuit with described input voltage sample circuit, described input and output voltage sum sample circuit.
Preferably, described backoff algorithm circuit is according to V
SN-COMP=V
SN* (V
IN+ V
O)/V
INCalculate and obtain bucking voltage V
SN-COMP
Wherein, V
SNBe V
INThe internal reference value of the voltage difference between PIN and the CSN PIN;
V
INPIN is for detecting the input voltage pin of resistance, and CSN PIN is for detecting resistance output voltage pin;
V
IN+ V
OBe the input and output voltage sum, obtain by described input and output voltage sum sample circuit;
V
INBe input voltage, obtain by described input voltage sample circuit.
Preferably, the Schottky diode negative electrode links to each other with LED is anodal, and the Schottky diode anode links to each other with the SW pin of described backoff algorithm circuit.
Preferably, described input and output voltage sum sample circuit comprises divider resistance and following divider resistance; Described upward divider resistance is connected between the COMP end of Schottky diode negative electrode and described backoff algorithm circuit; Described divider resistance down is connected between COMP end and the ground.
Preferably, described SW pin links to each other with the drain electrode of N-channel MOS FET, and N-channel MOS FET grid links to each other with described backoff algorithm circuit.
Preferably, the grid of N-channel MOS FET connects the hysteresis comparator output, and the input of hysteresis comparator links to each other with described backoff algorithm circuit.
Preferably, described control LED constant current output circuit is realized by the AP3221 chip.
The described control of this realization new embodiment LED constant current output circuit, based on input voltage is sampled, input and output voltage and the sampling, and to the input and output electric current and the sampling, calculate a suitable voltage through the backoff algorithm circuit, reach under the output voltage controlled condition purpose that output current does not change with the change of input voltage.
This realization is novel to be proposed under above background just, based on input voltage is sampled, input and output voltage and the sampling, and to the input and output electric current and the sampling, calculate a suitable voltage control MOSFET (metal oxide semiconductor field effect tube) Push And Release through the backoff algorithm circuit, reach under the output voltage controlled condition purpose that output current does not change with the change of input voltage.
Description of drawings
Fig. 1 is existing buck topology circuit diagram;
Fig. 2 is existing buck topological circuit figure;
Fig. 3 is the described control of the utility model first embodiment LED constant current output circuit figure;
Fig. 4 is the described control of the utility model second embodiment LED constant current output circuit figure.
Embodiment
The utility model provides a kind of LED constant current output circuit, is implemented under the output voltage controlled condition, and the LED output current does not change with the change of input voltage.
Referring to Fig. 3, this figure is the described control of the utility model first embodiment LED constant current output circuit figure.
The described control of the utility model first embodiment LED constant current output circuit, comprise input voltage sample circuit 101, input and output electric current sum sample circuit 301, input and output voltage sum sample circuit 201, current-to-voltage converting circuit 302, and backoff algorithm circuit 401.
Input voltage sample circuit 101 is used to gather input voltage V
IN
Input and output voltage sum sample circuit 201 is used to gather input voltage V
INAnd output voltage V
oSum.
Input and output electric current sum sample circuit 301 is used to gather the electric current that sample streams is crossed resistance R s both sides.
Current-to-voltage converting circuit 302 links to each other with described input and output electric current sum sample circuit 301, is used for the current value of described input and output electric current sum sample circuit 301 is converted to magnitude of voltage.
Backoff algorithm circuit 401 links to each other with described current-to-voltage converting circuit 302 with described input voltage sample circuit 101, described input and output voltage sum sample circuit 201, is used to calculate a suitable bucking voltage.
Because formula (1) is set up, V
IN* I
IN* η=V
O* I
O(1)
V
IN: input voltage;
I
IN: input current;
η: efficient
V
0: output voltage (i.e. the voltage of the LED lamp of all series connection)
I
0: output current (promptly by the LED electric current)
Simultaneously because formula (2) establishment
I
IN+I
O＝V
SN/R
S (2)
V
SNBe V
INThe internal reference value of the voltage difference between PIN and the CSN PIN; V
INPIN is for detecting the input voltage pin of resistance, and CSN PIN is for detecting resistance output voltage pin;
V
INPIN, CSN PIN is specifically as follows the AP3221 pin;
R
SFor detecting resistance.
Aggregative formula (1), (2) can get:
I
O＝V
SN*V
IN*η/[R
S*(R
IN*η+V
O)] (3)
Because this type of product efficiency is very high, is higher than 96% at least, so formula (3) can be approximately equal to
I
O＝V
SN*V
IN/[R
S*(V
IN+V
O)] (4)
By formula (4) as can be known, output current I
OBe proportional to V
IN/ (V
IN+ V
O), (wherein, V
SN, R
SBe definite value), for making that the output current constant current is I
ODo not change, can change V with input voltage
SNVoltage (the Buck-Boost converter V of the existing ring control that stagnates
SNBe steady state value).If V
SNChange and be proportional to (V
IN+ V
O)/V
IN, V then
SNVariation can be offset top described input voltage variation and input voltage output voltage sum changes I
OInfluence.
Suppose that the VSN in the formula (4) substitutes with VSN-COMP, then
I
O＝V
SIN-COMP*V
IN/[R
S*(V
IN+V
O)] (5)
Definition V
SN-COMP=V
SN* (V
IN+ V
O)/V
IN(6)
V
SN-COMP: the backoff algorithm circuit output voltage.
Can get I to formula (6) substitution formula (5)
O=V
SN/ R
SPromptly the circuit output current after overcompensation only and V
SN, R
SRelevant.
V
SN-COMP＝V
SN*(V
IN+V
O)/V
IN (7)
Backoff algorithm circuit 401 is with the value of input voltage sample circuit 101, input and output voltage sum sample circuit 201,301 samplings of input and output electric current sum sample circuit, be converted to correspondent voltage through backoff algorithm circuit 401, the bound voltage that this voltage and hysteresis comparator are set compares, control the Push And Release of MOSFET, reach the purpose of IO constant output.
Described backoff algorithm circuit 401 can calculate bucking voltage V according to formula (7)
SN-COMP
In the formula (7), V
SNBe V
INThe internal reference value of the voltage difference between PIN and the CSN PIN;
V
IN+ V
OBe the input and output voltage sum, obtain by input and output voltage sum sample circuit;
V
INBe input voltage, obtain by the input voltage sample circuit.
The described control of this realization new embodiment LED constant current output circuit, based on input voltage is sampled, input and output voltage and the sampling, and to the input and output electric current and the sampling, calculate a suitable voltage through the backoff algorithm circuit, reach the purpose that output current does not change with the change of input voltage.
The described control of this realization new embodiment LED constant current output circuit can be the LED power supply of a plurality of series connection.
Described input and output voltage sum sample circuit 201 comprises divider resistance R1 and following divider resistance R2.The COMP that the described divider resistance R1 of going up is connected Schottky diode D negative electrode and described backoff algorithm circuit 401 holds; Described divider resistance R2 down is connected between COMP end and the GND end.
Described SW pin links to each other with the drain electrode of N NMOS N-channel MOS N field effect transistor, and the grid of N NMOS N-channel MOS N field effect transistor links to each other with described backoff algorithm circuit 401.The drain electrode of N NMOS N-channel MOS N field effect transistor links to each other with the Schottky diode anode.
Be connected with hysteresis comparator 501 between metal oxide semiconductor field effect tube and the described backoff algorithm circuit 401.The grid of N NMOS N-channel MOS N field effect transistor connects hysteresis comparator 501 outputs, and the input of hysteresis comparator 501 links to each other with described backoff algorithm circuit 401.
The bound voltage of setting through the bucking voltage and the hysteresis comparator 501 of described backoff algorithm circuit 401 acquisitions compares, and the Push And Release of control MOSFET reaches I
OThe purpose of constant output.
When the upper voltage limit that the bucking voltage that obtains through described backoff algorithm circuit 401 is set less than hysteresis comparator 501, hysteresis comparator 501 output voltages are high, and MOSFET is in conducting state.When the lower voltage limit that the bucking voltage that obtains through described backoff algorithm circuit 401 is set less than hysteresis comparator 501, hysteresis comparator 501 output voltages are low, and MOSFET is in cut-off state.Because the bucking voltage V that backoff algorithm circuit 401 obtains
SN-COMPWith V
SNBetween individual proportionate relationship arranged:
Be V
SN-COMP=V
SN* (V
IN+ V
O)/V
IN
(V
IN+ V
O)/V
IN＞1, so compare and can shorten before backoff algorithm circuit 401 back MOSFET ON time being arranged and not having backoff algorithm circuit 401.MOSFET did not compare the meeting growth before with there being backoff algorithm circuit 401 deadline after backoff algorithm circuit 401 was arranged simultaneously, and the MOSFET ON time shortens and growth deadline, just can offset type I
O=V
SN* V
IN/ [R
S* (V
IN+ V
O)] middle V
IN/ (V
IN+ V
O) to I
OInfluence, both I
ODo not change with input, output voltage.
Referring to Fig. 4, this figure is the described control of the utility model second embodiment LED constant current output circuit figure.The described control of the utility model second embodiment LED constant current output circuit also can be realized by the AP3221 chip.
The described control of the utility model second embodiment LED constant current output circuit AP3221 chip also is to calculate bucking voltage V according to formula (7)
SN-NOMP
In the formula (7), V
SNBe V
INThe internal reference value of the voltage difference between PIN and the CSN PIN;
V
IN+ V
OBe the input and output voltage sum, obtain by input and output voltage sum sample circuit;
V
INBe input voltage, obtain by the input voltage sample circuit.
This realizes the described control of novel second embodiment LED constant current output circuit, based on input voltage is sampled, the sampling of input and output voltage sum, and input and output electric current sum sampled, calculate a suitable voltage through the backoff algorithm circuit, reach the purpose that output current does not change with the change of input voltage.
More than to described control LED constant current output circuit provided by the utility model, be described in detail, used specific case herein principle of the present utility model and execution mode are set forth, the explanation of above embodiment just is used for helping to understand method of the present utility model and core concept thereof; Simultaneously, for one of ordinary skill in the art, according to thought of the present utility model, the part that all can change in specific embodiments and applications, in sum, this description should not be construed as restriction of the present utility model.
Claims (7)
1. a LED constant current output circuit is characterized in that,
Described circuit comprises input voltage sample circuit, input and output electric current sum sample circuit, input and output voltage sum sample circuit;
With, the current-to-voltage converting circuit that links to each other with described input and output electric current sum sample circuit, and the backoff algorithm circuit that links to each other with described current-to-voltage converting circuit with described input voltage sample circuit, described input and output voltage sum sample circuit.
2. LED constant current output circuit according to claim 1 is characterized in that, described backoff algorithm circuit is according to V
SN-COMP=V
SN* (V
IN+ V
O)/V
INCalculate and obtain bucking voltage V
SN-COMPWherein, V
SNBe V
INThe internal reference value of the voltage difference between PIN and the CSN PIN;
V
INPIN is for detecting the input voltage pin of resistance, and CSN PIN is for detecting resistance output voltage pin;
V
IN+ V
OBe the input and output voltage sum, obtain by described input and output voltage sum sample circuit;
V
INBe input voltage, obtain by described input voltage sample circuit.
3. LED constant current output circuit according to claim 1 is characterized in that, the Schottky diode negative electrode links to each other with LED is anodal, and the Schottky diode anode links to each other with the SW pin of described backoff algorithm circuit.
4. LED constant current output circuit according to claim 3 is characterized in that, described input and output voltage sum sample circuit comprises divider resistance and following divider resistance; Described upward divider resistance is connected between the COMP end of Schottky diode negative electrode and described backoff algorithm circuit; Described divider resistance down is connected between COMP end and the ground.
5. LED constant current output circuit according to claim 3 is characterized in that, described SW pin links to each other with the drain electrode of N-channel MOS FET, and N-channel MOS FET grid links to each other with described backoff algorithm circuit.
6. LED constant current output circuit according to claim 5 is characterized in that, the grid of N-channel MOS FET connects the hysteresis comparator output, and the input of hysteresis comparator links to each other with described backoff algorithm circuit.
7. LED constant current output circuit according to claim 1 is characterized in that, described control LED constant current output circuit is realized by the AP3221 chip.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2010200024925U CN201657407U (en) | 2010-01-19 | 2010-01-19 | LED constant-current output circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2010200024925U CN201657407U (en) | 2010-01-19 | 2010-01-19 | LED constant-current output circuit |
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| Publication Number | Publication Date |
|---|---|
| CN201657407U true CN201657407U (en) | 2010-11-24 |
Family
ID=43122634
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2010200024925U Expired - Lifetime CN201657407U (en) | 2010-01-19 | 2010-01-19 | LED constant-current output circuit |
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| Country | Link |
|---|---|
| CN (1) | CN201657407U (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103582223A (en) * | 2012-08-07 | 2014-02-12 | 欧司朗股份有限公司 | Illuminating device |
| CN106413172A (en) * | 2016-06-14 | 2017-02-15 | 深圳欧创芯半导体有限公司 | Buck-boost constant current circuit and output current sampling method thereof |
| CN109039070A (en) * | 2018-08-08 | 2018-12-18 | 深圳市德赛微电子技术有限公司 | A kind of BUCK type DCDC output constant current detection control circuit and method |
-
2010
- 2010-01-19 CN CN2010200024925U patent/CN201657407U/en not_active Expired - Lifetime
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103582223A (en) * | 2012-08-07 | 2014-02-12 | 欧司朗股份有限公司 | Illuminating device |
| CN103582223B (en) * | 2012-08-07 | 2017-06-16 | 欧司朗股份有限公司 | Lighting device |
| CN106413172A (en) * | 2016-06-14 | 2017-02-15 | 深圳欧创芯半导体有限公司 | Buck-boost constant current circuit and output current sampling method thereof |
| CN109039070A (en) * | 2018-08-08 | 2018-12-18 | 深圳市德赛微电子技术有限公司 | A kind of BUCK type DCDC output constant current detection control circuit and method |
| CN109039070B (en) * | 2018-08-08 | 2020-12-15 | 深圳市德赛微电子技术有限公司 | BUCK type DCDC output constant current detection control circuit and method |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CX01 | Expiry of patent term |
Granted publication date: 20101124 |
|
| CX01 | Expiry of patent term |