CN118283873A - LED driving circuit, driving method and LED lighting lamp thereof - Google Patents

Abstract

The application discloses an LED driving circuit, a driving method and an LED lighting lamp thereof, relates to the technical field of LED driving circuits, solves the problem of insufficient luminous efficiency of an LED lamp string caused by unstable input voltage, and adopts the technical scheme that: the signal sampling circuit is connected to the input power supply and is used for sampling a voltage signal of the input voltage of the input power supply; the driving circuit is used for controlling the light-emitting state of each LED lamp bead in the LED lamp string; the logic circuit is used for controlling the access state of each LED lamp bead in the LED lamp string; the input end of the logic control output module is connected to the signal sampling circuit, the output end of the logic control output module is respectively connected to the driving circuit and the logic circuit, and the logic control output module is used for selecting corresponding conduction time sequences according to the magnitude of the voltage signals, and controlling the switching state of the logic circuit and the conduction state of the driving circuit according to the conduction time sequences so as to enable different LED lamp beads of the LED lamp string to be combined into a multi-section current conduction loop.

Description

LED driving circuit, driving method and LED lighting lamp thereof

Technical Field

The application relates to the technical field of LED driving circuits, in particular to an LED driving circuit, a driving method and an LED lighting lamp thereof.

Background

The LED lighting product mainly comprises an LED light source, an LED driving circuit and a heat dissipation mechanism. The combination mode of the LED light sources may have various forms, for example, a plurality of LED light beads are sequentially connected in series to form a single-string structure, or a plurality of LED light beads are connected in series to form an LED light string, and then a plurality of LED light strings are connected in parallel to form a matrix structure.

In order to reduce the cost, more LED products adopt a linear driving mode; the wide use of linear drives, the efficiency of which presents a significant disadvantage over non-isolated drives, is currently the main contradiction in how to improve the efficiency of linearity. At present, it is common practice to boost the lamp voltage at the rated voltage, but the input power is not constant and the light emission is not uniform during the period of the input voltage change, so that the light emission efficiency of the LED lamp string is reduced.

Disclosure of Invention

The application aims to provide an LED driving circuit, a driving method and an LED lighting lamp thereof, and solves the problem of insufficient luminous efficiency of an LED lamp string caused by unstable input voltage.

In a first aspect of the present application, there is provided an LED driving circuit for driving at least one LED string to emit light, the LED driving circuit comprising:

the signal sampling circuit is connected to the input power supply and is used for sampling a voltage signal of the input voltage of the input power supply;

The driving circuit is used for controlling the light-emitting state of each LED lamp bead in the LED lamp string;

The logic circuit is used for controlling the access state of each LED lamp bead in the LED lamp string;

The input end of the logic control output module is connected to the signal sampling circuit, the output end of the logic control output module is respectively connected to the driving circuit and the logic circuit, and the logic control output module is used for selecting corresponding conduction time sequences according to the magnitude of the voltage signals, and controlling the switching state of the logic circuit and the conduction state of the driving circuit according to the conduction time sequences so as to enable different LED lamp beads of the LED lamp string to be combined into a multi-section current conduction loop.

In an implementation manner of the first aspect of the present application, the input voltage is obtained by rectifying an ac input power supply through a rectifying circuit, and the signal sampling circuit is formed by connecting a first sampling resistor and a second sampling resistor in parallel.

In an implementation manner of the first aspect of the present application, a multiplier is connected between the logic control output module and the signal sampling circuit, a common end of the parallel connection of the first sampling resistor and the second sampling resistor is connected with an input end of the multiplier, and the multiplier is used for preprocessing a voltage signal.

In an implementation manner of the first aspect of the present application, the LED string is formed by sequentially connecting a first LED lamp bead, a second LED lamp bead, a first diode, a third LED lamp bead, a second diode and a fourth LED lamp bead in series; the anode of the first LED lamp bead is connected with the input voltage.

In an implementation manner of the first aspect of the present application, the logic circuit includes a first switch, a second switch, a first transistor and a second transistor, where inputs of the first switch and the second switch are connected to an output of the logic control output module, and are configured to receive a switching signal output from the logic control output module;

the first switch comprises a first driver and a first high-voltage transistor, and the second switch comprises a second driver and a second high-voltage transistor;

the output end of the first driver is connected with the grid electrode of the first high-voltage transistor, the source electrode of the first high-voltage transistor is grounded, and the drain electrode of the first high-voltage transistor is connected with the grid electrode of the first transistor;

The output end of the second driver is connected with the grid electrode of the second high-voltage transistor, the source electrode of the second high-voltage transistor is grounded, and the drain electrode of the second high-voltage transistor is connected with the grid electrode of the second transistor;

After the source electrode of the first transistor is connected with the drain electrode of the second transistor, a series connection node of the first diode and the third LED lamp bead is connected, the drain electrode of the first transistor is respectively connected with the cathode of the first LED lamp bead and the anode of the second LED lamp bead, and the source electrode of the second transistor is respectively connected with the cathode of the second diode and the anode of the fourth LED lamp bead.

In an implementation manner of the first aspect of the present application, the driving circuit includes a third driver, a fourth driver, a fifth driver, a third transistor, a fourth transistor, and a fifth transistor, where inputs of the third driver, the fourth driver, and the fifth driver are respectively connected to outputs of the logic control output module, and are configured to receive a conduction signal output from the logic control output module;

The output end of the third driver is connected with the grid electrode of the third transistor, and the drain electrode of the third transistor is respectively connected with the cathode of the second LED lamp bead and the anode of the first diode;

The output end of the fourth driver is connected with the grid electrode of the fourth transistor, and the drain electrode of the fourth transistor is respectively connected with the cathode of the third LED lamp bead and the anode of the second diode;

The output end of the fifth driver is connected with the grid electrode of the fifth transistor, and the drain electrode of the fifth transistor is connected with the cathode of the fourth LED lamp bead;

And the negative electrode input ends of the first driver, the second driver, the third driver, the fourth driver and the fifth driver are connected with the negative electrode of the input power supply.

In an implementation manner of the first aspect of the present application, the LED driving circuit further includes a current limiting resistor, one end of the current limiting resistor is connected to sources of the third transistor, the fourth transistor and the fifth transistor, and the other end of the current limiting resistor is connected to a ground voltage.

In an implementation manner of the first aspect of the present application, the driving circuit and the logic circuit do not control a lighting state and an on state of the first LED bead of the LED string.

In a second aspect of the present application, an LED driving method is provided, configured to drive at least one LED string to emit light according to a logic signal and a driving signal generated by a turn-on timing, where the LED driving method includes:

sampling a voltage signal of an input voltage of an input power supply;

Selecting a corresponding conduction time sequence according to the magnitude of the voltage signal, and controlling the switching state of the logic circuit and the conduction state of the driving circuit according to the conduction time sequence so as to enable different LED lamp beads of the LED lamp string to be combined into a multi-section current conduction loop;

the driving circuit is used for controlling the light emitting state of each LED lamp bead in the LED lamp string, and the logic circuit is used for controlling the access state of each LED lamp bead in the LED lamp string.

The third aspect of the application also provides an LED lighting lamp, which is provided with the LED driving circuit provided by the first aspect of the application and also comprises an LED light source consisting of at least one LED light string;

the input voltage of the LED driving circuit is obtained by rectifying an alternating current input power supply through a rectifying circuit.

Compared with the prior art, the application has the following beneficial effects:

In the LED driving circuit, the driving method and the LED lighting lamp provided by the application, the switching state of the corresponding conduction time sequence control logic circuit and the conduction state of the driving circuit are selected by sampling the voltage signal of the input voltage generated by the alternating current input power supply and combining the preset conduction time sequence corresponding to the voltage signal, so that each LED lamp bead is combined into the current conduction loops with different sections, the conduction process is different from the conventional forward sequential conduction process, namely, the voltage loss generated by the periodical change of the input voltage of the alternating current input power supply is clamped on the driving circuit by the conduction time sequence provided by the application, and the loss caused by the periodical change of the input voltage is fixed, so that the overall luminous efficiency of the LED lamp string is improved when the input voltage of the alternating current input power supply rises or falls.

Drawings

The accompanying drawings, which are included to provide a further understanding of embodiments of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the principles of the application. In the drawings:

Fig. 1 is a schematic diagram of a structure of an LED driving circuit according to an embodiment of the present application;

Fig. 2 is a schematic diagram of another structure of an LED driving circuit according to an embodiment of the present application;

fig. 3 is a simulation diagram of an operating waveform of an LED driving circuit according to an embodiment of the present application;

Fig. 4 is a schematic diagram of another structure of an LED driving circuit according to an embodiment of the present application;

fig. 5 is a schematic flow chart of an LED driving method according to an embodiment of the present application.

In the drawings, the reference numerals and corresponding part names:

110. A signal sampling circuit; 120. a logic control output module; 130. a logic circuit; 140. a driving circuit; 150. LED lamp strings; 11. a first driver; 12. a second driver; 13. a third driver; 14. a fourth driver; 15. a fifth driver, 16, a sixth driver; 17. a seventh driver; m1, a first transistor; m2, a second transistor; m3, a third transistor; m4, a fourth transistor; m5, fifth transistors; m6, sixth transistor; m7, seventh transistor; r1, a first sampling resistor; r2, a second sampling resistor; r3, a current limiting resistor; LED1, first LED lamp bead; LED2, second LED lamp bead; an LED3 and a third LED lamp bead; LED4, fourth LED lamp bead; LED5, fifth LED lamp bead; d1, a first diode; d2, a second diode; d3, a third diode.

Detailed Description

For the purpose of making apparent the objects, technical solutions and advantages of the present application, the present application will be further described in detail with reference to the following examples and the accompanying drawings, wherein the exemplary embodiments of the present application and the descriptions thereof are for illustrating the present application only and are not to be construed as limiting the present application.

It is noted that the terms "comprises" or "comprising" when utilized in various embodiments of the present application are indicative of the existence of the claimed function, operation or element and do not limit the addition of one or more functions, operations or elements. Furthermore, as used in various embodiments of the application, the terms "comprises," "comprising," and their cognate terms are intended to refer to a particular feature, number, step, operation, element, component, or combination of the foregoing, and should not be interpreted as first excluding the existence of or increasing likelihood of one or more other features, numbers, steps, operations, elements, components, or combinations of the foregoing.

It should be appreciated that terms such as "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present application, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.

First, technical terms of the present application will be described.

The LED lighting lamp, namely a light-emitting diode lighting lamp, is a semiconductor solid light-emitting device. The solid semiconductor chip is used as a luminescent material, and the carrier is compounded in the semiconductor to release excessive energy to cause photon emission, so that red, yellow, blue, green, cyan, orange, purple and white light is directly emitted.

An LED string, also known as an LED colored light strip, or rogowski wire, is composed of a plurality of light emitting diodes (LED light beads).

An LED lamp bead, i.e., a light emitting Diode (LIGHT EMITTING Diode), is a semiconductor device capable of directly converting electrical energy into light energy. The semiconductor device consists of P-type and N-type semiconductor materials, and when current passes through PN junctions formed by the P-type and N-type semiconductor materials, visible light can be emitted. The LED lamp beads have the characteristics of high efficiency, durability, environmental protection and the like, and are widely applied to the fields of illumination, display, decoration, indication and the like.

Referring to fig. 1, fig. 1 is a schematic structural diagram of an LED driving circuit 140 according to an embodiment of the present application, as shown in fig. 1, the LED driving circuit 140 according to the present embodiment is configured to drive at least one LED string 150 to emit light, where the LED driving circuit 140 includes:

A signal sampling circuit 110 connected to the input power source for sampling a voltage signal of an input voltage of the input power source;

a driving circuit 140 for controlling the light emitting state of each LED lamp bead in the LED lamp string 150;

Logic circuit 130 for controlling the access status of each LED light bead in LED light string 150;

the input end of the logic control output module 120 is connected to the signal sampling circuit 110, the output end is respectively connected to the driving circuit 140 and the logic circuit 130, and is used for selecting a corresponding conduction time sequence according to the magnitude of the voltage signal, and controlling the switching state of the logic circuit 130 and the conduction state of the driving circuit 140 according to the conduction time sequence, so that different LED lamp beads of the LED lamp string 150 are combined into a multi-section current conduction loop.

Specifically, the input voltage is obtained by rectifying an ac input power through a rectifying circuit, and the signal sampling circuit 110 is formed by connecting a first sampling resistor R1 and a second sampling resistor R2 in parallel. The rectifying circuit and the signal sampling circuit 110 are common knowledge in the art, so the working principle of this embodiment will be described only briefly. For rectifier circuits, which are generally designed to convert Alternating Current (AC) power to Direct Current (DC) power, they generally include a filtering and rectifying section, which is a filtering section before rectification, the AC power may contain a lot of high frequency noise and ripple, which need to be filtered out, and may be implemented by a filtering circuit, which generally includes a capacitor and an inductor, which may smooth the AC signal, reducing the ripple. For the rectifying portion, a common rectifying technique such as half wave, full wave, bridge, and the like may be employed. The signal sampling circuit 110, which is formed by connecting two sampling resistors in parallel, is generally used for partial pressure sampling, which is a common analog signal sampling technique. In this circuit, two resistors are connected in parallel, together forming a voltage divider for dividing the input voltage signal into two parts, each part passing through a sampling resistor. A brief description is given here of the signal sampling circuit 110: input voltage: the input voltage (Vin) is applied across two parallel sampling resistors (R1 and R2). Principle of partial pressure: according to ohm's law, the current (I1 and I2) through each sampling resistor is inversely proportional to their resistance. Since the voltages of the branches in the parallel circuit are the same, the voltage across each resistor is proportional to their resistance. This means that the voltage will be divided between the two resistors in proportion to their resistance values. Sampling resistance: each sampling resistor may be considered as a sampling point, each capturing a sample of the input voltage. These samples reflect the voltage level of the input voltage at the sampling instant. Sample and hold: in practice, sampling resistors are typically used in conjunction with sample and hold circuits. The sample-and-hold circuit fixes the input voltage to the sampling resistor during the sampling phase and then passes this sample voltage to the ADC for conversion during the hold phase. And (3) outputting: the voltages across the two sampling resistors can be converted into digital values, respectively, which represent the values of the input voltage signal at the sampling instants.

Further, a multiplier is connected between the logic control output module 120 and the signal sampling circuit 110, a common end of the parallel connection of the first sampling resistor R1 and the second sampling resistor R2 is connected with an input end of the multiplier, and the multiplier is used for preprocessing a voltage signal.

In particular, the preprocessing of the voltage signal by the multiplier generally refers to multiplying the sampled voltage signal with a reference signal or digital control signal, in order to achieve the following purposes, such as scaling: the multiplier may adjust the amplitude of the sampled voltage signal to meet a particular dynamic range or to meet the requirements of the subsequent logic control output module 120. For example, the amplitude of the voltage signal obtained by sampling by the signal sampling circuit 110 is narrowed to a range that can be handled. Such as frequency adjustment: the sampled voltage signal may be frequency modulated by a multiplier.

The application needs to solve the problem of insufficient luminous efficiency of the LED string light 150 caused by unstable input voltage of the ac input power. Therefore, when the input power is changed from 175 v to 265v, the conventional driving scheme can only achieve a luminous efficiency of more than 85% at a certain voltage input, and can reduce or darken the lamp beads at the time of voltage adjustment. Therefore, in order to solve the problem of the luminous efficiency of the LED string 150 when the input voltage is varied from 175 v to 265v, the present application selects the on-off state of the corresponding on-time control logic circuit 130 and the on-state of the driving circuit 140 by sampling the voltage signal of the input voltage generated by the ac input power and combining the preset on-time corresponding to the voltage signal, so that each LED lamp bead is combined into a current on loop with different segments, and the on-process is different from the conventional forward sequential on process, that is, the voltage loss generated by the periodic variation of the input voltage of the ac input power is clamped on the driving circuit 140 by the on-time provided by the present application, so that the loss caused by the periodic variation of the input voltage is fixed, and the luminous efficiency of the whole LED string 150 is improved when the input voltage of the ac input power is increased or decreased.

Specifically, as the foregoing embodiments show, the LED lighting fixture is mainly composed of an LED light source, an LED driving circuit 140 and a heat dissipation mechanism. The combination manner of the LED light sources may have various manners, for example, a plurality of LED light beads are sequentially connected in series to form a single-string structure, or a plurality of LED light beads are connected in series to form an LED light string 150, and then a plurality of LED light strings 150 are connected in parallel to each other to form an LED light source with a matrix structure. Therefore, the number of the LED light sources and the number of the LED driving circuits 140 included in the LED lighting product are determined to be constant, so that the present embodiment is not limited specifically, according to the current LED light source, the input voltage is increased or decreased by 10V, or is increased or decreased by 20V, or is increased or decreased by 15V, etc. according to the changing input voltage range and the changing range at a certain interval. For the case of increasing or decreasing the input voltage described in the above embodiment, the voltage signal obtained by sampling by the sampling circuit will also be fixedly changed by a value, in this embodiment, taking a 10V change as an example, when the input voltage is 190V, it is changed to 200V, the voltage signal obtained by sampling will be increased by 0.2V on the basis of 190V correspondence, and other cases of change are not exemplified in this embodiment. In combination with the above description, in the case that the voltage signal is fixedly increased or decreased due to the variation of the input voltage, the present embodiment selects the corresponding turn-on timing according to the magnitude of the voltage signal, and controls the on-off state of the logic circuit 130 and the on-state of the driving circuit 140 according to the turn-on timing.

It is understood that the multi-stage current conduction loop refers to a current conduction loop formed by the input voltage, each bead in the LED string 150, the logic circuit, the driving circuit, and the ground voltage in different variation intervals of the input voltage.

In one embodiment, the LED string 150 is formed by sequentially connecting a first LED lamp bead LED1, a second LED lamp bead LED2, a first diode D1, a third LED lamp bead LED3, a second diode D2, and a fourth LED lamp bead LED4 in series; the anode of the first LED lamp bead LED1 is connected with the input voltage.

Specifically, the LED string 150 generally includes a relatively fixed ratio or lamp voltage (36V for example in this embodiment) for the lamp beads. In the LED string 150, a combination of one LED bead (light emitting diode) and one diode in series is generally used to protect the LEDs from reverse voltage. Such a configuration is common in some LED strings 150, particularly those that require direct connection to a power source via wires. The diode here serves to prevent the LED from being damaged by a high voltage when the positive and negative poles of the power supply are connected incorrectly. When the positive electrode is connected to the positive line of the power supply and the negative electrode is connected to one end of the LED lamp bead, current flows to the LED to make the LED emit light. When the positive and negative poles of the power supply are connected in reverse, the diode will prevent current from flowing in reverse through the LED, thereby protecting the LED from being damaged by excessive voltages. A Diode is a semiconductor device, and is collectively referred to as a Crystal Diode (Crystal Diode). The diode has the characteristic of unidirectional conduction, namely, the diode is conducted under the action of forward voltage only and is in a cut-off state under the action of reverse voltage. The working principle is based on forward bias and reverse bias effects of PN junctions. When a forward voltage is applied to the anode of the diode and a reverse voltage is applied to the cathode of the diode, current can pass through the diode; when a reverse voltage is applied to the positive electrode and a forward voltage is applied to the negative electrode, current cannot pass through the diode.

In one embodiment, the logic circuit 130 includes a first switch, a second switch, a first transistor M1, and a second transistor M2, wherein inputs of the first switch and the second switch are connected to an output of the logic control output module 120, for receiving a switching signal output from the logic control output module 120; the first switch comprises a first driver 11 and a first high voltage transistor, and the second switch comprises a second driver 12 and a second high voltage transistor; the output end of the first driver 11 is connected with the gate of a first high-voltage transistor, the source electrode of the first high-voltage transistor is grounded, and the drain electrode of the first high-voltage transistor is connected with the gate of a first transistor M1; the output end of the second driver 12 is connected with the gate of a second high-voltage transistor, the source electrode of the second high-voltage transistor is grounded, and the drain electrode of the second high-voltage transistor is connected with the gate of a second transistor M2; after the source electrode of the first transistor M1 is connected with the drain electrode of the second transistor M2, a series connection node of the first diode D1 and the third LED lamp bead LED3 is connected, the drain electrode of the first transistor M1 is respectively connected with the cathode of the first LED lamp bead LED1 and the anode of the second LED lamp bead LED2, and the source electrode of the second transistor M2 is respectively connected with the cathode of the second diode D2 and the anode of the fourth LED lamp bead LED 4.

Specifically, referring to fig. 2, the logic circuit 130 is shown to be connected to each LED bead of the LED string 150, and it can be understood that in fig. 2, the LED string 150 contains 4 LED beads in total, so the logic circuit 130 provided in this embodiment contains a first transistor M1 and a second transistor M2. As a general knowledge known to those skilled in the art, the number of the lamp beads in the LED lamp string 150 of the LED light source of the current LED lighting product is mostly 4, and the LED lamp string 150 can be connected in parallel to meet the lighting requirement. But may be varied only for the LED string 150. For example, when the number of switches and transistors provided in the present embodiment is one, i.e. the LED string 150 contains three LED light beads in total, the middle light bead is connected to one diode, and accordingly the logic circuit 130 includes the first switch and the first transistor M1, i.e. the second switch and the second transistor M2 are removed. If the number of the lamp beads is five, a set of sub-logic circuits 130 is correspondingly added, that is, the logic circuits 130 include three switches and three transistors.

The first high-voltage transistor is mainly used for providing a large enough on current for the first transistor M1 to ensure that the first transistor M1 can be smoothly turned on. Accordingly, the second high voltage transistor has the same function as the first high voltage transistor, so as to provide a sufficient on current for the second transistor M2, so as to ensure that the second transistor M2 can be smoothly turned on.

In one embodiment, the driving circuit 140 includes a third driver 13, a fourth driver 14, a fifth driver 15, a third transistor M3, a fourth transistor M4, and a fifth transistor M5, where inputs of the third driver 13, the fourth driver 14, and the fifth driver 15 are respectively connected to the outputs of the logic control output module 120, so as to receive the on signals output from the logic control output module 120; the output end of the third driver 13 is connected with the gate of a third transistor M3, and the drain electrode of the third transistor M3 is respectively connected with the cathode of the second LED lamp bead LED2 and the anode of the first diode D1; the output end of the fourth driver 14 is connected with the gate of the fourth transistor M4, and the drain electrode of the fourth transistor M4 is connected with the cathode of the third LED lamp bead LED3 and the anode of the second diode D2 respectively; the output end of the fifth driver 15 is connected with the gate of a fifth transistor M5, and the drain electrode of the fifth transistor M5 is connected with the cathode of the fourth LED lamp bead LED 4; the negative input ends of the first driver 11, the second driver 12, the third driver 13, the fourth driver 14 and the fifth driver 15 are all connected with the negative electrode of an input power supply.

In this embodiment, the number of the switches and the transistors of the logic circuit 130 is changed in combination with the above embodiment, and the driving circuit 140 provided in this embodiment is also the same change manner, and the number of the current lamp beads is increased or decreased by one or more groups of sub-driving circuits 140, and the connection manner of the corresponding increased circuits is the same as that of the above connection, so that redundant description is omitted in this embodiment.

Specifically, the first to fifth transistors M1 to M5 may be effect transistor MOSFETs, bipolar transistors BJTs, or three-terminal controlled devices having equivalent switching functions, such as insulated gate bipolar transistors IGBTs, or the like. The first to fifth drivers 11 to 15 may employ power amplifiers to supply the on signals of the high voltage transistors included in the first and second switches and the on signals of the third to fifth transistors M3 to M5.

As shown in fig. 2, the LED string 150 is formed by four (or more) LED beads connected in series and connected to the driver circuit 140 and the logic circuit 130 during one half-cycle of rectification (e.g., 10 milliseconds for a half-cycle of a 50Hz power grid). The proportion of the LED beads can be in a fixed multiple relationship, the driving circuit 140 and the logic circuit 130 are controlled by logic to make each string of beads be combined differently, when the input voltage rises or falls, the voltage finally superimposed on the driving circuit 140 is clamped at a fixed voltage (such as 36V), so that the loss of the driving circuit 140 is not increased, and when the voltage of the beads rises step by step, the luminous efficiency is higher, and finally, the luminous efficiency of the LED lighting product is improved.

For example, when the input voltage is 190V, the sampled voltage signal is about 1.2V, which corresponds to a 3-segment current conduction loop drive. When the input voltage rises by 10V each time, the sampling voltage is fixedly changed by about 0.2V, the power MOS is correspondingly turned on (the power MOS is the third transistor M3, the fourth transistor M4 and the fifth transistor M5, the turn-on sequence of the power MOS is determined by design), the LED lamp bead voltage is correspondingly increased by 36V due to the logic switching of the first transistor M1 and the second transistor M2, and each change by 0.2V is finally realized due to the fixed proportion, the lamp voltage is increased by 36V, and the like and is switched 6-7 times. The other means that the voltage drop (i.e., loss) assumed by the power MOS is also fixed at 36V as the input voltage changes. Compared with the traditional scheme, the scheme has the advantages that the loss is fixed, and then the overall efficiency is remarkably improved along with the increase of the lamp voltage. When the voltage is changed from high to low, the lamp voltage is changed along with the voltage by adopting voltage reduction and logic conversion, but the drain voltage drop of the power MOS is always kept unchanged, and higher efficiency is still realized.

Still referring to fig. 2 as an example, the on states of the transistors M3 to M5 are controlled by the driver of the driving circuit 140, and the first transistor M1 and the second transistor M2 are controlled by the first switch SPC1 and the second switch SPC2, respectively. When the input voltage of the ac input power supply is 230Vac (340 VDC) (230V is the rated voltage for testing for europe), the logic control timing thereof is described as follows (-VDC, i.e., GND, +vdc, i.e., dc_bus):

The first section of lamp is lighted: the DC_BUS voltage is in the (72V, 108V) interval, and the current conduction loop is as follows: +VDC→the first LED bead LED1→the first transistor M1→the second transistor M2→the fourth LED bead LED4→ -VDC.

Specifically, for the first-stage lamp lighting, the values of the set 4-stage lamp voltages are all realized by increasing 36V per step. Because the optimal working state of the IC chip of the driving circuit is about 30V, the loss of the IC chip can be reduced by taking the nearest lamp voltage, and the working efficiency of the IC chip can be improved, namely, the reason of presetting the voltage conduction time sequence is that the setting principle is as follows: when alternating voltage is input, the change from zero crossing point to maximum value in one period is sinusoidal, the sampled signal also changes along with the input voltage, the fifth transistor M5 is turned on when the sampling signal is 1.2V, meanwhile, the first transistor M1/second transistor M2 is also turned on, the corresponding LED lamp voltage also reaches the starting condition along with the voltage rise, and the process of the first section is the process of the first LED lamp bead LED 1+the fourth LED lamp bead LED4, namely 72V+36V=108V lamp voltage. Because the voltage of 72V is very low, the three-section light string can be used as all public first sections to gradually accumulate 36V until 288V is accumulated. The first stage of lighting is the first LED bead LED 1+fourth LED bead LED4, and is just 72v+36v=108v lamp voltage.

The second section of lamp is lighted: the DC_BUS voltage is in the (108V, 144V) interval, and the current conduction loop is as follows: +VDC→the first LED bead LED1→the first transistor M1→the third LED bead LED3→the fourth transistor M4→ -VDC.

Specifically, for the second segment of lamp lighting, the input alternating current sine wave voltage continues to increase by about 36V, when the set sampling signal is 1.4V, the first transistor M1/fourth transistor M4 is turned on, the corresponding LED lamp voltage also reaches the on condition along with the voltage rise, and the second segment is just a current loop of the first LED lamp bead LED 1+the third LED lamp bead LED3, namely 72v+72v=144V lamp voltage.

And (3) lighting a third section of lamp: the DC_BUS voltage is in the interval (144V, 180V), and the current conduction loop is as follows: +VDC, first LED bead LED1, third LED bead LED3, second diode D2, fourth LED bead LED4, and fifth transistor M5-VDC.

And lighting a fourth section: the DC_BUS voltage is in the (180V, 216V) interval, and the current conduction loop is as follows: +VDC- & gtfirst LED bead LED 1- & gtsecond LED bead LED 2- & gtthird transistor M3- & gtVDC.

The fifth section of lamp is lighted: the DC_BUS voltage is in the (216V, 252V) interval, and the current conduction loop is as follows: +VDC- & gtfirst LED bead LED 1- & gtsecond LED bead LED 2- & gtfirst diode D1- & gtfourth LED bead LED 4- & gtfifth transistor M5- & gtVDC.

The sixth section of lamp is lighted: DC_BUS voltage is in (252V, 288V), and the current conduction loop is: +VDC, first LED bead LED1, second LED bead LED2, first diode D1, third LED bead LED3, and fourth transistor M4-VDC.

The seventh section of lamp is lighted: the DC _ BUS voltage is in the (288V, + -infinity) interval, the current conduction loop is as follows: +VDC, first LED lamp bead LED1, second LED lamp bead LED2, first diode D1, third LED lamp bead LED3, second diode D2, fourth LED lamp bead LED4, and fifth transistor M5-VDC.

Specifically, for the process of lighting the third to seventh sections, reference may be made to the above-described implementation process of lighting the first and second sections, and redundant description is not made in this embodiment.

When the input voltage of the ac input power source is 220Vac (310 VDC) (domestic rated ac voltage), only six voltage segments are operated at this time due to sampling signals, and the efficiency is the highest, as shown in the following:

The first section of lamp is lighted: the DC_BUS voltage is in the (72V, 108V) interval, and the current conduction loop is as follows: +VDC→the first LED bead LED1→the first transistor M1→the second transistor M2→the fourth LED bead LED4→ -VDC.

The second section of lamp is lighted: the DC_BUS voltage is in the (108V, 144V) interval, and the current conduction loop is as follows: +VDC→the first LED bead LED1→the first transistor M1→the third LED bead LED3→the fourth transistor M4→ -VDC.

And (3) lighting a third section of lamp: the DC_BUS voltage is in the interval (144V, 180V), and the current conduction loop is as follows: +VDC, first LED bead LED1, third LED bead LED3, second diode D2, fourth LED bead LED4, and fifth transistor M5-VDC.

And lighting a fourth section: the DC_BUS voltage is in the (180V, 216V) interval, and the current conduction loop is as follows: +VDC- & gtfirst LED bead LED 1- & gtsecond LED bead LED 2- & gtthird transistor M3- & gtVDC.

The fifth section of lamp is lighted: the DC_BUS voltage is in the (216V, 252V) interval, and the current conduction loop is as follows: +VDC, first LED bead LED1, second LED bead LED2, first diode D1, fourth LED bead LED4, and fifth transistor M5-VDC.

The sixth section of lamp is lighted: DC_BUS voltage is in (252V, 288V), and the current conduction loop is: +VDC, first LED bead LED1, second LED bead LED2, first diode D1, third LED bead LED3, and fourth transistor M4-VDC.

It should be noted that, when the input voltage is reduced, the self-adaptive operation is performed to a smaller number of segments, such as five segments, four segments, etc., and the LED string is adapted to a wider input voltage and emits light completely through the self-adaptive adjustment, so as to improve the light emitting efficiency of the LED string.

In summary, as shown in fig. 3, through the description of the working principle of the multi-segment linear LED lamp beads, the on time of the LED lamp beads is significantly increased, that is, the on time is longer, and more LED lamp beads emit light under the same input power, so that the overall efficiency of the LED lamp string 150 is improved. As can be seen from the simulation waveform diagram of fig. 3, the waveform of each period is mirror symmetrical, so this embodiment illustrates the principle that the first period of the waveform of the input bus current is the same as the rest of the periods.

As shown in fig. 3, a half cycle of the rising portion of the current waveform in the first cycle corresponds to: the first pattern block of the first channel current waveform (third transistor M3), the first pattern block and the second pattern block of the second channel current waveform (fourth transistor M4), and the first pattern block to the fourth pattern block of the third channel current waveform (fifth transistor M5), wherein the fourth pattern block for the half period of the rising portion contains only the first half portion. Accordingly, a half cycle of the falling portion of the current waveform in the first cycle corresponds to: a second pattern block of the first channel current waveform, a third pattern block and a fourth pattern block of the second channel current waveform, and a fourth pattern block to a seventh pattern block of the third channel current waveform, wherein the fourth pattern block comprises only a second half portion for a half period of the falling portion.

From the simulation waveform diagram of fig. 3, seven-segment driving effects can be generally shown by one pattern block of the first channel current waveform, two pattern blocks of the second channel current waveform, and four pattern blocks of the third channel current waveform. Compared with the traditional three-section mode of about 84%, four-section mode of about 85% and five-section mode of about 86%, the efficiency is higher and can exceed 90%. And the input voltage can fully emit light even if being lower than the rated range, so that the adaptability is wider.

As shown in fig. 4, based on the schematic structural diagram of the minimum number of LED beads shown in fig. 2, a fifth LED bead LED5 is added in this embodiment, and based on the description of the above embodiment, each additional bead is added with a corresponding driving circuit and logic circuit, for example, a seventh transistor M7 connected to the anode of the fifth LED bead LED5, a sixth transistor M6 connected to the cathode of the fifth LED bead LED5, and accordingly, in order to control the on state of the sixth transistor M6, a corresponding sixth driver 16 is needed, and accordingly, a seventh transistor M7 of the logic circuit is also needed, and a high voltage transistor and a driver are needed to control the on and off of the logic circuit, so as shown in fig. 4, the output terminal of the seventh driver 17 is connected to the gate of the high voltage transistor, and then the drain of the high voltage transistor is connected to the gate of the seventh transistor M7, which is the same as the connection principle described above, and as a person skilled in the art can understand that when adding more driving circuits and logic circuits, the redundant circuit is not implemented in the same manner.

Based on the content shown in fig. 4, when the input voltage 300Vac (420 VDC) is input, the driving circuit and the driving method provided by the embodiment of the application can be used for lighting more sections of lamp beads, so that the high efficiency of the LED lamp string is realized, and the specific steps are as follows:

The first section of lamp is lighted: the DC_BUS voltage is in the (72V, 108V) interval, and the current conduction loop is as follows: +VDC, first LED bead LED1, first transistor M1, second transistor M2, seventh transistor M7, fifth LED bead LED5, sixth transistor M6 and-VDC.

The second section of lamp is lighted: the DC_BUS voltage is in the (108V, 144V) interval, and the current conduction loop is as follows: +VDC, first LED bead LED1, first transistor M1, second transistor M2, fourth LED bead LED4, fifth transistor M5, and VDC.

And (3) lighting a third section of lamp: the DC_BUS voltage is in the interval (144V, 180V), and the current conduction loop is as follows: +VDC, first LED bead LED1, first transistor M1, second transistor M2, fourth LED bead LED4, third diode D3, fourth transistor M4, sixth transistor M6 and-VDC.

And lighting a fourth section: the DC_BUS voltage is in the (180V, 216V) interval, and the current conduction loop is as follows: +VDC- & gtfirst LED bead LED 1- & gtsecond LED bead LED 2- & gtthird transistor M3- & gtVDC.

The fifth section of lamp is lighted: the DC_BUS voltage is in the (216V, 252V) interval, and the current conduction loop is as follows: +VDC, first LED bead LED1, third LED bead LED3, second diode D2, fourth LED bead LED4, third diode D3, fifth LED bead LED5, sixth transistor M6 and-VDC.

The sixth section of lamp is lighted: DC_BUS voltage is in (252V, 288V), and the current conduction loop is: +VDC, first LED bead LED1, second LED bead LED2, first diode D1, third LED bead LED3, and fourth transistor M4-VDC.

The seventh section of lamp is lighted: the DC_BUS voltage is in the (284V, 324V) interval, and the current conduction loop is as follows: +VDC, first LED bead LED1, second LED bead LED2, first diode D1, third LED bead LED3, second diode D2, seventh transistor M7, fifth LED bead LED5, sixth transistor M6 and-VDC.

The eighth segment of lamp is lighted: the DC_BUS voltage is in the (324V, 360V) interval, and the current conduction loop is as follows: +VDC, first LED lamp bead LED1, second LED lamp bead LED2, first diode D1, third LED lamp bead LED3, second diode D2, fourth LED lamp bead LED4, and fifth transistor M5-VDC.

The ninth segment lights: the DC_BUS voltage is in the interval (360V, 390V), and the current conduction loop is as follows: +VDC, first LED bead LED1, second LED bead LED2, first diode D1, third LED bead LED3, second diode D2, fourth LED bead LED4, third diode D3, fifth LED bead LED5, and sixth transistor M6.

Specifically, for the case shown in fig. 4, the first to ninth segments of the lighting process are provided in this embodiment, and reference may also be made to the above-described implementation process of the first segment of the lighting process and the second segment of the lighting process, which is not described in detail in this embodiment. It should be noted that, fig. 4 clearly shows the connection condition of each device when the number of LED beads is 5, so this embodiment will not be described one by one.

In one embodiment, the LED driving circuit 140 further includes a current limiting resistor R3, one end of the current limiting resistor R3 is connected to the sources of the third transistor M3, the fourth transistor M4 and the fifth transistor M5, and the other end of the current limiting resistor R3 is connected to the ground voltage.

Specifically, the current limiting resistor R3 has the following main functions: protection LED: each LED has a recommended forward current value, and the current limiting resistor R3 can be calculated according to the forward current and the voltage of the LED, so that the LED is ensured to work in the maximum working current range, and the LED is prevented from being damaged due to overlarge current. Stable brightness: the current limiting resistor R3 can limit the current, so that the working state of the LED is stable, and the brightness change caused by the fluctuation of the current is avoided. Voltage distribution: in LED string 150, there may be small differences in voltage across each LED, and current limiting resistor R3 may help balance these voltage differences, ensuring that each LED operates under similar conditions. Prevent overheating: excessive current can cause the LED to generate excessive heat, and the current limiting resistor R3 can help control the current, so that the heating value of the LED is reduced, and the service life is prolonged. Preventing short circuit: if one of the LEDs in the LED string 150 fails or is shorted, the current limiting resistor R3 may limit the current, preventing the entire circuit from being damaged by the short.

In some embodiments, the driving circuit 140 and the logic circuit 130 do not control the light emitting state and the on state of the first LED bead LED1 of the LED string 150.

Specifically, as can be seen from fig. 2 or fig. 4, the first LED lamp bead LED1 is the first lamp bead connected to the input voltage after ac rectification as the LED lamp string, so each current conducting loop must include the first LED lamp bead LED1, otherwise the entire LED lamp string is in the off state.

Referring to fig. 5, fig. 5 is a flow chart of an LED driving method according to an embodiment of the present application, as shown in fig. 4, the LED driving method is used for driving at least one LED string 150 to emit light according to a logic signal and a driving signal generated by a turn-on timing sequence, and the LED driving method includes:

S410, sampling a voltage signal of an input voltage of an input power supply;

S420, selecting a corresponding conduction time sequence according to the magnitude of the voltage signal, and controlling the switching state of the logic circuit 130 and the conduction state of the driving circuit 140 according to the conduction time sequence so as to enable different LED lamp beads of the LED lamp string 150 to be combined into a multi-section current conduction loop; the driving circuit 140 is configured to control a light emitting state of each LED light bead in the LED light string 150, and the logic circuit 130 is configured to control an access state of each LED light bead in the LED light string 150.

In this embodiment, the LED driving method is implemented based on the LED driving circuit 140 provided in the above embodiment, so for the detailed working process of the LED driving method provided in this embodiment, reference may be made to the detailed description of the embodiment of the LED driving circuit provided in the above embodiment, and the detailed description of this embodiment is omitted.

It can be seen that, in the LED driving method provided in the embodiment of the present application, by sampling the voltage signal of the input voltage generated by the ac input power supply and combining the preset conduction timing corresponding to the voltage signal, the corresponding on-off state of the conduction timing control logic circuit 130 and the conduction state of the driving circuit 140 are selected, so that each LED lamp bead is combined into the current conduction loop with different segment numbers, so that the conduction process is different from the conventional forward sequential conduction process, that is, the voltage loss generated by the periodic variation of the input voltage of the ac input power supply is clamped on the driving circuit 140 by the conduction timing provided in the present application, so that the loss caused by the periodic variation of the input voltage is fixed, and therefore, when the input voltage of the ac input power supply rises or falls, the overall luminous efficiency of the LED lamp string 150 is improved.

The embodiment of the application also provides an LED lighting lamp, which is provided with the LED driving circuit 140 provided by the embodiment and further comprises an LED light source consisting of at least one LED light string 150; the input voltage of the LED driving circuit 140 is obtained by rectifying an ac input power through a rectifying circuit.

According to the LED lighting lamp provided with the LED driving circuit 140, through sampling the voltage signal of the input voltage generated by the alternating current input power supply and combining the preset conduction time sequence corresponding to the voltage signal, the corresponding switching state of the conduction time sequence control logic circuit 130 and the conduction state of the driving circuit 140 are selected, so that each LED lamp bead of the LED lamp string 150 is combined into current conduction loops with different sections, the conduction process is different from the conventional forward sequential conduction process, namely, the voltage loss generated by the periodic variation of the input voltage of the alternating current input power supply is fixed on the driving circuit 140 through the conduction time sequence provided by the application, and therefore, the overall lighting efficiency of the LED lighting lamp is improved when the input voltage of the alternating current input power supply rises or falls.

The foregoing description of the embodiments has been provided for the purpose of illustrating the general principles of the application, and is not meant to limit the scope of the application, but to limit the application to the particular embodiments, and any modifications, equivalents, improvements, etc. that fall within the spirit and principles of the application are intended to be included within the scope of the application.

Claims (10)

1. An LED driving circuit, which is configured to drive at least one LED string to emit light, the LED driving circuit comprising:

the signal sampling circuit is connected to the input power supply and is used for sampling a voltage signal of the input voltage of the input power supply;

The driving circuit is used for controlling the light-emitting state of each LED lamp bead in the LED lamp string;

The logic circuit is used for controlling the access state of each LED lamp bead in the LED lamp string;

The input end of the logic control output module is connected to the signal sampling circuit, the output end of the logic control output module is respectively connected to the driving circuit and the logic circuit, and the logic control output module is used for selecting corresponding conduction time sequences according to the magnitude of the voltage signals, and controlling the switching state of the logic circuit and the conduction state of the driving circuit according to the conduction time sequences so as to enable different LED lamp beads of the LED lamp string to be combined into a multi-section current conduction loop.

2. The LED driving circuit according to claim 1, wherein the input voltage is obtained by rectifying an ac input power through a rectifying circuit, and the signal sampling circuit is constituted by a first sampling resistor and a second sampling resistor connected in parallel.

3. An LED driving circuit according to claim 2, wherein a multiplier is connected between the logic control output module and the signal sampling circuit, a common terminal of the first sampling resistor and the second sampling resistor connected in parallel is connected to an input terminal of the multiplier, and the multiplier is used for preprocessing a voltage signal.

4. The LED driving circuit of claim 1, wherein the LED string is formed by sequentially connecting a first LED bead, a second LED bead, a first diode, a third LED bead, a second diode, and a fourth LED bead in series; the anode of the first LED lamp bead is connected with the input voltage.

5. The LED driver circuit of claim 4, wherein the logic circuit comprises a first switch, a second switch, a first transistor, and a second transistor, inputs of the first switch and the second switch being coupled to an output of the logic control output module for receiving the switching signal from the logic control output module;

the first switch comprises a first driver and a first high-voltage transistor, and the second switch comprises a second driver and a second high-voltage transistor;

the output end of the first driver is connected with the grid electrode of the first high-voltage transistor, the source electrode of the first high-voltage transistor is grounded, and the drain electrode of the first high-voltage transistor is connected with the grid electrode of the first transistor;

The output end of the second driver is connected with the grid electrode of the second high-voltage transistor, the source electrode of the second high-voltage transistor is grounded, and the drain electrode of the second high-voltage transistor is connected with the grid electrode of the second transistor;

After the source electrode of the first transistor is connected with the drain electrode of the second transistor, a series connection node of the first diode and the third LED lamp bead is connected, the drain electrode of the first transistor is respectively connected with the cathode of the first LED lamp bead and the anode of the second LED lamp bead, and the source electrode of the second transistor is respectively connected with the cathode of the second diode and the anode of the fourth LED lamp bead.

6. The LED driving circuit of claim 5, wherein the driving circuit comprises a third driver, a fourth driver, a fifth driver, a third transistor, a fourth transistor, and a fifth transistor, wherein inputs of the third driver, the fourth driver, and the fifth driver are respectively connected to the outputs of the logic control output module for receiving the on signal from the logic control output module;

The output end of the third driver is connected with the grid electrode of the third transistor, and the drain electrode of the third transistor is respectively connected with the cathode of the second LED lamp bead and the anode of the first diode;

The output end of the fourth driver is connected with the grid electrode of the fourth transistor, and the drain electrode of the fourth transistor is respectively connected with the cathode of the third LED lamp bead and the anode of the second diode;

The output end of the fifth driver is connected with the grid electrode of the fifth transistor, and the drain electrode of the fifth transistor is connected with the cathode of the fourth LED lamp bead;

And the negative electrode input ends of the first driver, the second driver, the third driver, the fourth driver and the fifth driver are connected with the negative electrode of the input power supply.

7. The LED driving circuit of claim 6, further comprising a current limiting resistor, wherein one end of the current limiting resistor is connected to the sources of the third transistor, the fourth transistor and the fifth transistor, respectively, and the other end of the current limiting resistor is connected to the ground voltage.

8. The LED driver circuit of claim 6, wherein the driver circuit and logic circuit do not control the light state and the on state of the first LED light beads of the LED light string.

9. The LED driving method is characterized by driving at least one LED lamp string to emit light according to a logic signal and a driving signal generated by a conduction time sequence, and comprises the following steps:

sampling a voltage signal of an input voltage of an input power supply;

Selecting a corresponding conduction time sequence according to the magnitude of the voltage signal, and controlling the switching state of the logic circuit and the conduction state of the driving circuit according to the conduction time sequence so as to enable different LED lamp beads of the LED lamp string to be combined into a multi-section current conduction loop;

the driving circuit is used for controlling the light emitting state of each LED lamp bead in the LED lamp string, and the logic circuit is used for controlling the access state of each LED lamp bead in the LED lamp string.

10. An LED lighting fixture, characterized in that the LED lighting fixture has an LED driving circuit according to any one of claims 1 to 8, and further comprises an LED light source composed of at least one LED string;

the input voltage of the LED driving circuit is obtained by rectifying an alternating current input power supply through a rectifying circuit.