CN203399354U

CN203399354U - Combined linear constant current source and LED driving circuit

Info

Publication number: CN203399354U
Application number: CN201320394503.2U
Authority: CN
Inventors: 邵蕴奇
Original assignee: SHANGHAI LUQIAN ELECTRONIC TECHNOLOGY Co Ltd
Current assignee: SHANGHAI LUQIAN ELECTRONIC TECHNOLOGY Co Ltd
Priority date: 2013-07-03
Filing date: 2013-07-03
Publication date: 2014-01-15
Anticipated expiration: 2023-07-03

Abstract

The utility model discloses a combined linear constant current source and an LED driving circuit which are mainly used in the LED driving field. The combined linear constant current source comprises a plurality of power field effect transistors and a control circuit; the control circuit includes an input terminal and an output terminal; the source electrodes of the plurality of power field effect transistors are connected in parallel and then are connected with the input terminal of the control circuit; the output terminal of the control circuit is respectively connected with the gate electrodes of the plurality of power field effect transistors; and the drain electrodes of the plurality of power field effect transistors serve as the output terminal of the linear constant current source. The LED driving circuit includes an alternating current, a rectifier bridge, and a plurality of LED light-emitting tubes which are connected with the linear constant current source in series. The beneficial effects of the utility model are that: when the voltage of the electric supply is too high, the heat can be effectively dissipated; when the voltage of the electric supply is too low, the brightness of the LED light-emitting tubes can be effectively configured to be consistent; and the simple circuit structure, low cost, easy large-scale popularization are realized.

Description

Combined linear constant current source and LED drive circuit

Technical Field

The utility model relates to a combination linear constant current source and LED drive circuit, concretely relates to combination linear constant current source and utilize its drive circuit who constitutes, are particularly useful for LED lighting drive.

Background

At present, LED lighting is rapidly popularized due to energy conservation, environmental protection and long service life, and LED lamps and lanterns have widely entered lighting application in various fields. The LED can not be directly connected to alternating current, a corresponding current-limiting driving device needs to be configured, the scheme used for driving the LED at present mainly adopts a traditional high-frequency switching power supply, and due to the fact that a high-frequency switching circuit is needed, the circuit is complex, cost is high, and a linear current-limiting driving scheme is used by a plurality of manufacturers.

In fig. 1, an alternating current 101 charges an energy storage capacitor 103 at the positive and negative half-cycle peak values of a sine wave through a rectifier 102, the energy storage capacitor 103 keeps the voltage at two ends always larger than the voltage at two ends of an LED 105, and a current limiter 104 bears the voltage exceeding the LED on the energy storage capacitor to keep the current of the LED 105 constant. The circuit is characterized in that the circuit is simple, and the constant current source 104 can be integrated in a special IC; the disadvantages of this circuit are: firstly, when the voltage of the mains supply is higher, the power consumption of the constant current source 104 is very large, and although the current constant current source IC uses a package with a metal heat sink, the temperature rise of the IC is still higher, which limits the application power range of the linear driving; secondly, when the voltage of the mains supply is low, the energy storage capacitor 103 cannot maintain that the voltage at the two ends of the energy storage capacitor is always larger than the voltage at the two ends of the LED 105, so that no current flows through the LED 105 in the later discharge period of the energy storage capacitor 103.

Therefore, it is necessary to improve the problems of the linear constant current driving circuit, such as the temperature rise of the integrated constant current source caused by the high mains voltage and the large brightness reduction caused by the low mains voltage.

SUMMERY OF THE UTILITY MODEL

To the technical defect that above-mentioned prior art exists, the to-be-solved technical problem of the utility model is: the combined linear constant current source circuit is designed into an LED linear constant current source driving circuit which is used for carrying out heat shunting by an external resistor when the mains supply is higher.

In order to solve the technical problem, the utility model discloses a technical scheme is: a combined linear constant current source comprises a plurality of power field effect transistors and a control circuit; the control circuit comprises an input end and an output end, the source electrodes of the power field effect transistors are connected in parallel and then connected with the input end of the control circuit, the output end of the control circuit is respectively connected with the gate electrodes of the power field effect transistors, and the drain electrodes of the power field effect transistors are the output ends of the linear constant current source.

Preferably, the control circuit comprises a sampling resistor, an operational amplifier, a reference voltage and a voltage offset circuit; the positive pole of the reference voltage is connected with the non-inverting input end of the operational amplifier, the inverting input end of the operational amplifier is connected with one end of the sampling resistor, the inverting input end of the operational amplifier is used as the input end of the control circuit, and the other end of the sampling resistor is connected with the negative pole of the reference voltage and then grounded; the voltage offset circuit comprises an input end and a plurality of output ends, the input end of the voltage offset circuit is connected with the output end of the operational amplifier, and the output end of the voltage offset circuit is the output end of the control circuit.

Preferably, the voltage offset circuit comprises a plurality of voltage bias circuits, and the plurality of voltage bias circuits are respectively connected in series between the output end of the operational amplifier and a plurality of output ends of the voltage offset circuit.

Preferably, the voltage bias circuits generate different offset voltages, and the offset voltages are used for controlling the conduction priorities of the field effect transistors.

Preferably, the voltage offset circuit comprises a resistor and a plurality of diodes; the plurality of diodes are sequentially connected in series along the same polarity direction to form a diode string, one end of the anode of the diode string after the diode string is connected with the output end of the operational amplifier, one end of the cathode of the diode string after the diode string is connected with one end of the resistor, the other end of the resistor is grounded, and the connection intersection of the two ends of the diode string and each diode is the output end of the voltage deviation circuit.

Utilize above-mentioned combination constant current source circuit, the utility model also discloses an LED drive circuit who utilizes this constant current source circuit to constitute.

An LED driver circuit comprising: the LED constant current source comprises alternating current, a rectifier bridge and a plurality of LED luminous tubes connected in series, wherein the alternating current is connected with the input end of the rectifier bridge, the positive output end of the rectifier bridge is connected with the anodes of the LED luminous tubes connected in series, the negative output end of the rectifier is grounded, the LED constant current source also comprises a linear constant current source, and the cathodes of the LED luminous tubes are respectively connected with the output ends of the linear constant current source.

Preferably, the energy storage device comprises an energy storage capacitor, and the energy storage capacitor is connected in parallel with the positive output end and the negative output end of the rectifier.

As the preferred scheme, the linear constant current source comprises a plurality of power shunt resistors, and one end of each power shunt resistor is connected with the output end of the linear constant current source.

Preferably, one end of each power shunt resistor is connected to an output end branch requiring power shunt, and the other end of each power shunt resistor is connected to another output end branch having a higher conduction priority than the output end branch.

The utility model discloses the positive effect who gains is: when the voltage of the mains supply is higher, part of heat generated by the loss of the constant current driving circuit is borne by the power shunt resistor, so that the temperature rise of the constant current source is reduced; when the mains voltage is low, the LED luminous tubes of the short-circuit part of the combined constant-current source enable the other LED luminous tubes to have enough brightness, and therefore the problem that the brightness of the LED luminous tubes is greatly reduced when the mains voltage is low is solved.

Drawings

Fig. 1 is a conventional linear constant current drive circuit.

Fig. 2 shows the principle of the combined linear constant current source of the present invention.

Fig. 3 is a preferred embodiment of the combined linear constant current source of the present invention.

Fig. 4 is a preferred embodiment of the present invention utilizing a combined linear constant current source for LED driving.

Fig. 5 is another preferred embodiment of the embodiment of fig. 4.

Fig. 6 is yet another preferred embodiment to the embodiment of fig. 4 or 5.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

Fig. 2 is a schematic circuit diagram of the combined linear constant current source of the present invention, which includes

power fets

201, 202, 203 … … and a control circuit 200; all the sources of the

power fets

201, 202, 203 … … are connected in parallel and then connected to the input terminal of the control circuit 200, the drains of the

power fets

201, 202, 203 … … are used as the output branches out1, out2, out3 … … of the linear constant current source, and the output terminal of the control circuit 200 controls the gates of the

power fets

201, 202, 203 … … respectively. Wherein,

the control circuit 200 includes a sampling resistor 207, an operational amplifier 204, a reference voltage 206 and a voltage offset circuit 205; the positive electrode of the reference voltage 206 is connected to the non-inverting input terminal of the operational amplifier 204, the inverting input terminal of the operational amplifier 204 is connected to one end of the sampling resistor 207 and then serves as the input terminal of the control circuit 200, and the other end of the sampling resistor 207 and the negative electrode of the reference voltage 206 are grounded; the voltage offset circuit 205 includes an input terminal and a plurality of output terminals, the input terminal is connected to the output of the operational amplifier 204, and the output terminal is the output of the control circuit 200;

the voltage offset circuit 205 includes a plurality of voltage bias circuits respectively connected in series between the output of the operational amplifier 204 and a plurality of output terminals of the voltage offset circuit 205. The operational amplifier 204 controls the voltage drop of the sum of the currents flowing through the

power fets

201, 202, 203 … … on the sampling resistor 207 to be equal to the voltage of the reference voltage 206, the voltage offset circuit 205 generates a plurality of different offset voltages related to the output of the operational amplifier 204 to control the conduction priorities of the

power fets

201, 202, 203 … …, when the output branches out1, out2, out3 … … of the linear constant current source of the present invention have sufficient bias voltages, the conduction priorities of the power fets are 201, 202, 203 … … from low to high, and when the bias voltages on the branches with high priority conduction are insufficient, the branches with suboptimal pilot conduction of sufficient bias voltages are conducted.

Fig. 3 is a preferred embodiment of the combined linear constant current source of the present invention, which comprises

power fets

301, 302, 303 … … and a control circuit 300; all the sources of the

power fets

301, 302, 303 … … are connected in parallel and then connected to the input terminal of the control circuit 300, the drains of the

power fets

301, 302, 303 … … are used as the output branches out1, out2, out3 … … of the linear constant current source, and the output of the control circuit 300 controls the gates of the

power fets

301, 302, 303 … … respectively. Wherein,

the control circuit 300 includes a sampling resistor 307, an operational amplifier 304, a reference voltage 306 and a voltage offset circuit 305; the positive electrode of the reference voltage 306 is connected to the non-inverting input terminal of the operational amplifier 304, the inverting input terminal of the operational amplifier 304 is connected to one end of the sampling resistor 307 and then serves as the input terminal of the control circuit 300, and the other end of the sampling resistor 307 and the negative electrode of the reference voltage 306 are grounded; the voltage offset circuit 305 includes an input terminal connected to the output of the operational amplifier 304 and a plurality of output terminals, which are the outputs of the control circuit 300;

the voltage offset circuit 305 includes a plurality of diodes 3001, 3002 … … and a resistor 310 connected in series in sequence, the anodes of the diodes 3001, 3002 … … connected in series in sequence are connected to the output of the operational amplifier 304, the cathodes are grounded via the resistor 310, and the two ends of the diodes 3001, 3002 … … connected in series and the cathodes of the series nodes are used as the output terminals of the voltage offset circuit 305 and the control circuit 300 and are connected to the gate terminals of the

power fets

301, 303 … …, respectively.

The operational amplifier 304 controls the voltage drop of the sum of the currents flowing through the

power fets

301, 302, 303 … … on the sampling resistor 307 to be equal to the voltage of the reference voltage 306, the voltage offset circuit 305 generates a plurality of levels offset from the output of the operational amplifier 304 by a plurality of diode drops to control the turn-on priorities of the

power fets

301, 302, 303 … …, respectively, when the output branches out1, out2, out3 … … of the linear constant current source of the present invention have sufficient bias voltages, the turn-on priorities of the power fets are from low to high as 301, 302, 303 … …, and when the bias voltage on the high-priority turn-on branch is insufficient, the sub-priority turn-on branch is turned on.

Fig. 4 is a preferred embodiment of using the combined linear constant current source of the present invention for driving LEDs, which comprises a commercial power 401, a rectifier bridge 402 and a plurality of LED light emitting tubes 405 connected in series in addition to the combined linear constant current source 404; the utility power 401 is connected to the input of the rectifier bridge 402, the positive output electrode of the rectifier bridge 402 is connected to the anodes of the series-connected LED tubes 405, the cathodes of the LED tubes are connected to the corresponding output branches of the linear constant current source 404, and the negative output electrode of the rectifier 402 is grounded.

The working principle of the circuit is as follows: the commercial power 401 outputs a pulsating direct current voltage after passing through the rectifier bridge 402, when the instantaneous value of the pulsating voltage exceeds the total serial voltage of the LED tubes 405, the highest priority output branch of the combined linear constant current source 404 is turned on, and all the LED tubes have current flowing through; when the instantaneous value of the pulsating voltage is slightly lower than the total voltage of the series of LED tubes 405, the bias voltage of the highest priority output branch of the combined linear constant current source 404 is insufficient, and no current flows through the LED tube directly connected to the branch, then a current flows through the second priority conducting branch of the combined constant current source 404, further, when the instantaneous value of the pulsating voltage drops again, resulting in insufficient bias voltage on the second priority conducting branch of the combined constant current source 404, then no current flows through the LED tubes directly connected to the second priority branch, and the current flowing through the combined linear constant current source 404 is transferred to the third priority pilot channel branch of the combined constant current source 404, and so on … ….

According to the embodiment, when the instantaneous value of the power supply voltage is lower, the number of the LED light-emitting tubes connected in series can be automatically reduced, so that no current flows through the LED light-emitting tubes.

The rectifier bridge 404 output is connected in parallel with an energy storage capacitor 403 in fig. 4, as shown in fig. 5, which is an advantageous improvement over the embodiment of fig. 4. The energy storage capacitor 403 can reduce the voltage ripple amplitude of the mains after passing through the rectifier bridge, which is more beneficial to the stability of the brightness of the LED in the ac period of the mains.

Fig. 6 is a further advantageous improvement to the embodiment of fig. 4 or fig. 5, and in addition to the features of fig. 4 and fig. 5, the power splitting resistor 606 and 607 … … is further included, one end of the power splitting resistor 606 is connected to the output branch out1 requiring power splitting, the other end is connected to another output branch out2 having higher conduction priority than the output branch, one end of the power splitting resistor 607 is connected to the output branch out3 requiring power splitting, the other end is connected to another output branch out4 having higher conduction priority than the output branch … …, and so on.

The power-split output branch out1 has lower conduction priority than the output branch out2 of the power-split resistor 606, the output branch out1 starts to have current flow only when the bias voltage of the output branch out2 is insufficient, the power-split output branch out3 has lower conduction priority than the output branch out4 of the power-split resistor 607, and the output branch out3 starts to have current flow only when the bias voltage of the output branch out4 is insufficient, so that the heat generated when the output branch voltage of the constant current source 604 is higher is transferred to the power-split resistors 606, 607 … ….

The effect obtained by the embodiment is as follows: when the voltage of the mains supply is higher, part of heat generated by the loss of the constant current driving circuit is borne by the power shunt resistor, so that the temperature rise of the constant current source is reduced; when the mains voltage is low, the LED luminous tubes of the short-circuit part of the combined constant-current source enable the other LED luminous tubes to have enough brightness, and therefore the problem that the brightness of the LED luminous tubes is greatly reduced when the mains voltage is low is solved.

The above specific embodiments have described only the main features and innovative points of the solution. It will be appreciated by those skilled in the art that the present solution is not limited by the embodiments described above. Without departing from the spirit and scope of the invention, there are numerous variations and modifications that fall within the scope of the claims. The scope of the present solution is defined by the appended claims and equivalents thereof.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. The word "comprising" does not exclude the presence of elements or steps other than those listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements, and the mere fact that, in a list of several circuit claims, several of these means can be represented by one and the same item of hardware is likewise an element, does not indicate that a combination of these means cannot be used to advantage, since they are described in different dependent claims.

It is to be noted that, in this document, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action, without necessarily requiring or implying any such actual relationship or order between such entities or operations, furthermore, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed, or to an element inherent to such a process, method, article, or apparatus, the terms "connected," "connecting," or other variations do not include only the direct connection of two entities, but also the indirect connection through other entities with beneficial and improved effects.

Claims

1. A combined linear constant current source, comprising: comprises a plurality of power field effect transistors and a control circuit; the control circuit comprises an input end and an output end, the source electrodes of the power field effect transistors are connected in parallel and then connected with the input end of the control circuit, the output end of the control circuit is respectively connected with the gate electrodes of the power field effect transistors, and the drain electrodes of the power field effect transistors are the output ends of the linear constant current source.

2. The linear constant current source of claim 1, wherein: the control circuit comprises a sampling resistor, an operational amplifier, a reference voltage and a voltage offset circuit; the positive pole of the reference voltage is connected with the non-inverting input end of the operational amplifier, the inverting input end of the operational amplifier is connected with one end of the sampling resistor, the inverting input end of the operational amplifier is used as the input end of the control circuit, and the other end of the sampling resistor is connected with the negative pole of the reference voltage and then grounded; the voltage offset circuit comprises an input end and a plurality of output ends, the input end of the voltage offset circuit is connected with the output end of the operational amplifier, and the output end of the voltage offset circuit is the output end of the control circuit.

3. The linear constant current source of claim 2, wherein: the voltage offset circuit comprises a plurality of voltage offset circuits, and the voltage offset circuits are respectively connected in series between the output end of the operational amplifier and a plurality of output ends of the voltage offset circuit.

4. The linear constant current source of claim 3, wherein: the voltage bias circuits generate different offset voltages, and the offset voltages are used for controlling the conduction priorities of the field effect transistors.

5. The linear constant current source of claim 2, wherein: the voltage offset circuit comprises a resistor and a plurality of diodes; the plurality of diodes are sequentially connected in series along the same polarity direction to form a diode string, one end of the anode of the diode string after being connected in series is connected with the output end of the operational amplifier, one end of the cathode of the diode string after being connected in series is connected with one end of the resistor, the other end of the resistor is grounded, and the connection intersection of the two ends of the diode string and each diode is the output end of the voltage deviation circuit.

6. An LED driver circuit comprising: alternating current, rectifier bridge and the LED luminotron of a plurality of series connection, the alternating current is connected with rectifier bridge's input, and rectifier bridge's positive output is connected with the positive pole after the LED luminotron of a plurality of series connection establishes ties, rectifier negative output ground connection, its characterized in that: the combined linear constant current source according to claim 1, further comprising a combined linear constant current source, wherein the cathodes of the LED light-emitting tubes are respectively connected to the output terminals of the linear constant current source.

7. The LED driving circuit according to claim 6, wherein: the energy storage capacitor is connected in parallel with the positive and negative output ends of the rectifier.

8. The LED driving circuit according to claim 6 or 7, wherein: the power divider comprises a plurality of power dividing resistors, and one end of each power dividing resistor is connected with the output end of the linear constant current source.

9. The LED driving circuit according to claim 8, wherein: one end of each power shunt resistor is connected with an output end branch circuit needing power shunt, and the other end of each power shunt resistor is connected with another output end branch circuit with higher conduction priority than the output end branch circuit.