CN112996186A

CN112996186A - Pulse-controlled circuit unit, drive circuit, integrated circuit and lighting device

Info

Publication number: CN112996186A
Application number: CN201911307356.9A
Authority: CN
Inventors: 邵蕴奇; 王光亮; 李锐; 步明迅; 李鹤
Original assignee: Anhui Zhanhui Electronic Technology Co ltd
Current assignee: Anhui Zhanhui Electronic Technology Co ltd
Priority date: 2019-12-18
Filing date: 2019-12-18
Publication date: 2021-06-18
Anticipated expiration: 2039-12-18
Also published as: CN112996186B

Abstract

The invention discloses a pulse-controlled circuit unit, a driving circuit, an integrated circuit and a lighting device, wherein the circuit unit comprises a chopper, a filter circuit and a controllable current source; the chopper is connected with an external pulse signal and an original excitation signal, and outputs the pulse signal when the pulse signal is at an effective level and cuts off the original excitation signal when the pulse signal is at an ineffective level; the cut-off frequency of the filter circuit is lower than the frequency of the pulse signal, the filter circuit is connected with the output end of the chopper, discontinuous original excitation signals output by the chopper are filtered, smooth electric signals are output to the controllable current source, and the controllable current source outputs driving current which is in a positive single modulation relation with the smooth electric signals to drive the LED group. The invention uses the pulse signal to control the chopper, outputs smooth electric signals through the filter circuit, and the controllable current source outputs the driving current which is in direct proportion to the duty ratio of the pulse signal, thereby realizing the LED dimming function of continuous current, no electromagnetic interference, no stroboflash and low-brightness dimming.

Description

Pulse-controlled circuit unit, drive circuit, integrated circuit and lighting device

Technical Field

The invention relates to the field of LED illumination control, in particular to a pulse-controlled circuit unit, an LED driving circuit and an illumination device.

Background

The LED is a current mainstream lighting device, it is very easy to control the on or off of the LED, the change of the LED brightness can be realized by controlling the difference of the average current flowing through the LED, and the LED dimming device is realized according to this principle. In addition, the LED with different color temperatures are combined, the brightness of the LED with each color temperature is respectively adjusted, the dimming and color mixing application of the LED device can be realized, for example, the brightness of the LED with two color temperatures of cold white and warm white is respectively controlled, the brightness and the color temperature of the LED lighting device can be controlled, and for example, the red, green and blue LEDs are matched, the brightness of the red, green and blue LEDs is respectively adjusted, and the full-color LED lighting device is realized. There are many devices for adjusting the brightness of the LED, such as the conventional thyristor dimming, the 0-10V dimming, etc., and the intelligent lighting device which is rapidly developed in recent years, and the brightness of the LED is controlled by using the pulse signal. The working principle is as shown in figure 1.

The voltage source V0, the operational amplifier EA0, the field effect transistor Q0 and the resistor RCS together form a constant current source, and the set current value of the constant current source is V0/RCS. The circuit dimming is realized by controlling an enable end EN of an operational amplifier EA0 through a Pulse Width Modulation (PWM), wherein when the PWM is at a high level, the constant current source outputs a set current value, and when the PWM is at a low level, the constant current source is turned off; the larger the PWM duty ratio is, the larger the average output current of the constant current source is, and the brighter the LED is, whereas the smaller the PWM duty ratio is, the smaller the average output current of the constant current source is, and the darker the LED is. By adopting the technical scheme, the current in the LED is pulse type discontinuous current, and the LED dimming circuit has the following defects in dimming:

1) the current of the LED is interrupted, and the light emission has stroboscopic effect;

2) the current in the circuit is discontinuous power current, the larger power current in the form of a switch can generate larger EMI (Electromagnetic Interference), a capacitor needs to be connected in parallel behind the rectifier to eliminate the Interference on a power grid, and the circuit cannot be designed for application with high power factor;

3) the minimum duty ratio is limited, and due to the discrete rising and falling characteristics of the current of the constant current source, the interference on a power grid when the current rises and falls and the like, the LED emits light and is easy to flicker when the PWM duty ratio is low.

Meanwhile, since the PWM is a switch for controlling the current source of the output stage, the current source of the power stage needs to consider the stability of the loop, and the switching speed cannot be designed very fast, the frequency of the PWM cannot be designed to be a high value, and when the frequency is high, the response speed of the constant current source is insufficient, so that the dimming performance is reduced.

Disclosure of Invention

The invention aims to overcome the defects of stroboflash, poor EMI performance and limited minimum duty ratio of light emission caused by the intermittent current of an LED in the prior art, and provides a pulse-controlled circuit unit, an LED driving circuit and a lighting device.

The invention solves the technical problems through the following technical scheme:

the invention provides a pulse-controlled circuit unit, which comprises a chopper, a filter circuit and at least one controllable current source;

the chopper is connected with an external pulse signal and an external original excitation signal and used for outputting the original excitation signal when the pulse signal is at an effective level and cutting off the original excitation signal when the pulse signal is at an ineffective level;

the cut-off frequency of the filter circuit is lower than the frequency of the pulse signal, and the filter circuit is connected with the output end of the chopper and is used for filtering discontinuous original excitation signals output by the chopper and outputting smooth electric signals;

the at least one controllable current source is respectively connected with the output end of the filter circuit and outputs at least one path of driving current, the driving current and the smooth electric signal are in a positive single modulation relationship, and the driving current is used for driving the LED group.

Preferably, the pulse-controlled circuit unit further comprises a pulse-free detection circuit, and the pulse-free detection circuit is used for detecting the duration of the inactive level of the pulse signal and outputting an enable signal to control the at least one controllable current source; when the duration of the invalid level is less than or equal to a first preset time, the enable signal is an active level, and the at least one controllable current source outputs the driving current; when the duration of the invalid level is longer than a first preset time, the enabling signal is the invalid level, and the at least one controllable current source is turned off; the first preset time is greater than the period of the pulse signal.

Preferably, the chopper includes an inverter, a first switch and a second switch, the pulse signal connects an input end of the inverter and a control end of the first switch, an output end of the inverter connects a control end of the second switch, a first connection end of the first switch connects the original excitation signal, a second connection end of the first switch connects a first connection end of the second switch as an output end of the chopper, and a second connection end of the second switch is grounded.

Preferably, the filter circuit includes a first resistor and a first capacitor, one end of the first resistor is connected to the output end of the chopper, the other end of the first resistor is connected to one end of the first capacitor as the output end of the filter circuit, and the other end of the first capacitor is grounded.

Preferably, the controllable current source includes an operational amplifier, a field effect transistor, and a second resistor, a positive phase terminal of the operational amplifier is connected to an output terminal of the filter circuit, an inverted phase terminal of the operational amplifier is connected to a source of the field effect transistor and one end of the second resistor, the other end of the second resistor is grounded, an output terminal of the operational amplifier is connected to a gate of the field effect transistor, and a drain of the field effect transistor serves as an output terminal of the controllable current source.

Preferably, when there are a plurality of the at least one controllable current source, the plurality of controllable current sources are cascaded, and when the controllable current source of the next stage is turned on, the controllable current source of the previous stage is turned off.

Preferably, the pulse-free detection circuit includes a first voltage source, a first diode, a third resistor, a second capacitor, and a first comparator, wherein an anode of the first diode is connected to the pulse signal, a cathode of the first diode is connected to one end of the third resistor, one end of the second capacitor, and a positive phase end of the first comparator, another end of the third resistor and another end of the second capacitor are grounded, a negative phase end of the first comparator is connected to an anode of the first voltage source, a cathode of the first voltage source is grounded, and an output end of the first comparator serves as an output end of the pulse-free detection circuit.

The invention also provides an LED driving circuit, which comprises the pulse control circuit unit, and an LED group, wherein the anode of the LED group is connected with the anode of a power supply, and the cathode of the LED group is connected with the output end of a controllable current source;

or the LED driving circuit further comprises a plurality of LED groups, the LED groups are connected in series, the anode of the first LED group in the LED groups is connected with the anode of the power supply, and the cathodes of the LED groups are respectively connected with the output end of a controllable current source.

Preferably, when the LED driving circuit includes one LED group, two ends of the one LED group are connected in parallel to the third capacitor;

when the LED driving circuit comprises a plurality of LED groups, the two ends of the LED groups are respectively connected with the third capacitor in parallel, and a second diode is respectively connected between two adjacent LED groups in series or a second diode is respectively connected between the negative electrode of the LED group except the first LED group in the LED groups and the output end of the controllable current source in series.

Preferably, the LED driving circuit includes a plurality of the circuit units and a plurality of the pulse signals, the LED driving circuit further includes a plurality of LED units, the LED units include the at least one LED group, different LED units have different color temperatures, the pulse signals are respectively connected to one of the circuit units, the circuit units respectively drive one of the LED units, and the brightness and/or color temperature of the LED units are adjusted by adjusting the duty ratio of the pulse signals.

Preferably, the LED driving circuit further comprises an excitation circuit, and the external original excitation signal is generated by the excitation circuit;

the excitation circuit comprises a second direct current power supply, and the second direct current power supply outputs the original excitation signal;

or, the excitation circuit includes a fourth resistor and a fifth resistor, the positive electrode of the power supply is connected to one end of the fourth resistor, the other end of the fourth resistor and one end of the fifth resistor are connected to be used as the output end of the excitation circuit to output the original excitation signal, the other end of the fifth resistor is grounded, and the negative electrode of the power supply is grounded;

or, the excitation circuit includes a voltage-controlled current source, a second voltage source, a sixth resistor, a seventh resistor, and an eighth resistor, a positive electrode of the power source is connected to one end of the sixth resistor, another end of the sixth resistor is connected to one end of the seventh resistor and a negative phase end of the voltage-controlled current source, another end of the seventh resistor is grounded, a positive electrode of the second voltage source is connected to a positive phase end of the voltage-controlled current source, a negative electrode of the second voltage source is grounded, an output end of the voltage-controlled current source is connected to one end of the eighth resistor as an output end of the excitation circuit, the original excitation signal is output, and another end of the eighth resistor is grounded.

The invention also provides an integrated circuit, which is packaged with the pulse control circuit unit;

or, the integrated circuit is packaged with the aforementioned pulse-controlled circuit unit, and is packaged with a part or all of the aforementioned excitation circuit.

The invention also provides a lighting device which comprises the LED driving circuit.

On the basis of the common knowledge in the field, the above preferred conditions can be combined randomly to obtain the preferred embodiments of the invention.

The positive progress effects of the invention are as follows: the chopper is controlled by pulse signal PWM, the original excitation signal is switched on and off and then is output to a smooth electric signal through the filter circuit, the driving current output by the controllable current source is controlled to be in direct proportion to the duty ratio of the pulse signal, and the LED dimming function with the advantages of continuous current, no electromagnetic interference, no stroboflash, low-brightness dimming and the like in the dimming process is realized. The cut-off frequency of the filter circuit is controlled to be smaller than the frequency of the pulse signal PWM, the filter circuit converts discontinuous signals output by the chopper into smooth electric signals, so that the current in the LED is continuous, stroboflash and electromagnetic interference cannot be caused, a power grid cannot fluctuate due to interference, and the LED cannot flicker when emitting light; because the pulse signal PWM in the chopper controls the on-off of the two switches, the frequency of the pulse signal PWM is not limited, and the wide-range PWM frequency can be compatible. Furthermore, the controllable current source is turned off when the duration time of the invalid level of the external pulse signal PWM by the pulse-free detection circuit is greater than a first preset time, the period that the first preset time is greater than the pulse signal is configured, and the controllable current source can be turned off when the duty ratio of the PWM signal is zero. Furthermore, a plurality of pulse-controlled circuit units and a plurality of pulse signals PWM are used for respectively controlling the LED units with different color temperatures, so that the brightness and the color temperature can be respectively changed or the brightness and the color temperature can be simultaneously changed.

Drawings

Fig. 1 is a schematic diagram of a circuit for dimming by using a pulse signal according to the prior art.

Fig. 2 is a schematic circuit diagram of a pulse-controlled circuit unit according to embodiment 1 of the present invention.

Fig. 3 is a schematic circuit diagram of a pulse-controlled circuit unit according to embodiment 2 of the present invention.

Fig. 4 is a schematic circuit diagram of a pulse-controlled circuit unit including 3 driving circuits according to embodiment 3 of the present invention.

Fig. 5 is a schematic circuit diagram of a pulse-controlled circuit unit including 1-way driving circuit according to embodiment 3 of the present invention.

Fig. 6 is a schematic circuit diagram of an LED driving circuit using a dc power supply as an excitation circuit according to embodiment 4 of the present invention.

Fig. 7 is a schematic circuit diagram of an LED driving circuit using two resistors as an excitation circuit according to embodiment 4 of the present invention.

Fig. 8 is a schematic circuit diagram of an LED driving circuit using a voltage-controlled current source as an excitation circuit according to embodiment 4 of the present invention.

Fig. 9 is a schematic circuit diagram of an LED driving circuit according to embodiment 5 of the present invention.

Fig. 10 is a schematic circuit diagram of another circuit of the LED driving circuit according to embodiment 5 of the present invention.

Fig. 11 is a schematic circuit diagram of an LED driving circuit according to embodiment 6 of the present invention.

Detailed Description

The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention.

Example 1

The present embodiment provides a pulse-controlled circuit unit, as shown in fig. 2, the pulse-controlled circuit unit 1 comprises a chopper 11, a filter circuit 12 and at least one controllable current source 13;

the chopper 11 is connected with an external pulse signal PWM and an external original excitation signal VR, and is used for outputting the original excitation signal VR when the pulse signal PWM is at an effective level and cutting off the original excitation signal VR when the pulse signal PWM is at an ineffective level; the active level here may be a high level or a low level, and is specifically designed according to actual needs.

The filter circuit 12 is connected to the output end of the chopper 11, and is configured to filter the discontinuous original excitation signal output by the chopper 11 and convert the discontinuous original excitation signal into a smooth electric signal, and the cutoff frequency of the filter circuit 12 is configured to be lower than the frequency of the pulse signal PWM, so that the output smooth electric signal is continuous and has no abrupt change.

At least one controllable current source 13 is connected to the output end of the filter circuit 12, and outputs at least one path of driving current, the driving currents and the smooth electrical signal output by the filter circuit 12 are in a positive single modulation relationship, and the driving current is used for driving the LED group. The monotone change relation comprises a positive monotone change and a negative monotone change, wherein the positive monotone change means that when the independent variable increases, the dependent variable increases, or when the independent variable decreases, the dependent variable decreases; an inverse monotonic change means that the dependent variable decreases as the independent variable increases or increases as the independent variable decreases. For example, the dependent variable is configured as a linear function of the independent variable.

Because the filter circuit 12 converts discontinuous original excitation signals into continuous smooth electric signals, the driving current output by the controllable current source 13 is a continuous signal, so that the current in the LED driven by the current source is continuous, and the defect that the LED in the prior art emits light and has stroboscopic effect can be overcome; when the duty ratio of an external pulse signal PWM is low, the cut-off frequency of the filter circuit is controlled to be smaller than the PWM frequency, the output current is still continuous, and the continuous output current cannot generate EMI (electromagnetic interference); meanwhile, continuous output current cannot interfere with a power grid, the power grid cannot fluctuate due to interference, and therefore LED light emitting cannot flicker.

In the embodiment, the chopper is controlled by an external pulse signal PWM, the original excitation signal is subjected to on-off control and then is output to a smooth electric signal through the filter circuit, the driving current output by the controllable current source is controlled to be in direct proportion to the duty ratio of the pulse signal, and the LED dimming function with the advantages of continuous current, no electromagnetic interference, no stroboflash, low-brightness dimming and the like in the dimming process is realized.

Example 2

This embodiment is further improved from embodiment 1, and as shown in fig. 3, the pulse-controlled circuit unit 1 further includes a pulse-free detection circuit 14.

The pulse-less detection circuit 14 is adapted to detect the duration of the inactive level of the pulse signal and to output an enable signal EN to control the at least one controllable current source 13. The pulse-less detection circuit 14 may be connected to the external pulse signal PWM directly as shown in fig. 3, connected to the output terminal of the chopper 11, or connected to another logic signal related to the pulse signal PWM. The pulse-free detection circuit 14 detects the duration time of the invalid level of the pulse signal PWM, when the duration time of the invalid level is less than or equal to a first preset time, the enable signal EN is an active level, and the at least one controllable current source 13 outputs a driving current for driving the LED; when the inactive level lasts for a time greater than the first preset time, the enable signal EN is at the inactive level and the at least one controllable current source 13 is turned off. The first preset time is configured to be longer than the period of the pulse signal PWM, and when the duty ratio of the pulse signal PWM is zero, the enable signal EN is at an inactive level, and the controllable current source 13 is turned off.

In this embodiment, the pulse-less detection circuit is configured to turn off the controllable current source when the inactive level duration of the external pulse signal PWM is greater than the first preset time, the first preset time is configured to be greater than the period of the pulse signal, and the controllable current source can be turned off when the duty ratio of the external pulse signal PWM is zero.

Example 3

This embodiment is a specific circuit implementation of embodiment 2. As shown in fig. 4, the pulse-controlled circuit unit 1 comprises a chopper 11, a filter circuit 12, at least one controllable current source 13 and a pulse-free detection circuit 14.

The chopper 11 includes an inverter INV, a first switch SW1 and a second switch SW2, an external pulse signal PWM is connected to an input terminal of the inverter INV and a third connection terminal, i.e., a control terminal, of the first switch SW1, an output terminal of the inverter INV is connected to a third connection terminal, i.e., a control terminal, of the second switch SW2, a first connection terminal of the first switch SW1 is connected to the original excitation signal VR, a second connection terminal of the first switch SW1 is connected to a first connection terminal of the second switch SW2 as an output terminal of the chopper 11, and a second connection terminal of the second switch SW2 is grounded.

Here, the active level is set to high level, when the pulse signal PWM is high level, the first switch SW1 is turned on, the second switch SW2 is turned off, and the original excitation signal VR is transmitted to the input terminal of the filter circuit 12; conversely, when the pulse signal PWM is at a low level, the second switch SW2 is turned on, the first switch SW1 is turned off, and the input terminal of the filter circuit 12 is grounded. The chopper 11 changes the original excitation signal into a discontinuous original excitation signal in the form of pulses. Because the pulse signal PWM in the chopper 11 controls the on/off of the two switches, and does not control the current source of the output stage as in the prior art, the frequency of the pulse signal PWM is not limited, and can be designed to be a higher value and compatible with a wider range of PWM frequencies.

The filter circuit 12 comprises a first resistor R1 and a first capacitor C1, one end of the first resistor R1 is connected to the output end of the chopper 11, the other end of the first resistor R1 is connected to one end of the first capacitor C1 as the output end of the filter circuit 12, and the other end of the first capacitor C1 is grounded.

The first resistor R1 and the first capacitor C1 form an RC filter, and the cutoff frequency of the RC filter is configured to be lower than the frequency of the pulse signal PWM, so that the voltage across the first capacitor C1, i.e., the output signal of the filter circuit 12, is smoothed, i.e., the filter circuit 12 filters the discontinuous original excitation signal output by the chopper 11, and outputs a smoothed electrical signal.

The at least one controllable current source 13 may be a plurality of controllable current sources 13 cascaded to form a multi-path driving circuit, or may include only one controllable current source 13 of one-path driving circuit as shown in fig. 5. A controllable current source 13 comprises an operational amplifier EA1, a field effect transistor Q1 and a second resistor R2, wherein the non-inverting terminal of the operational amplifier EA1 is connected with the output terminal of the filter circuit 12, the inverting terminal of the operational amplifier EA1 is connected with the source of the field effect transistor Q1 and one end of the second resistor R2, the other end of the second resistor R2 is grounded, the output terminal of the operational amplifier EA1 is connected with the gate of the field effect transistor Q1, and the drain of the field effect transistor Q1 serves as the output terminal of the controllable current source 13. The non-inverting terminal of the operational amplifier EA1 receives the output signal of the filter circuit 12, and the current flowing through the fet Q1 is controlled in proportion to the output signal of the filter circuit 12, even though the driving current outputted from the controllable current source 13 is in proportion to the smoothed electrical signal outputted from the filter circuit 12.

In order to realize the function, a plurality of controllable current sources 13 are cascaded, and when the controllable current source 13 of the later stage is turned on, the controllable current source 13 of the previous stage is turned off, a multi-path driving circuit formed by the plurality of controllable current sources 13 in a cascaded manner may be connected as shown in fig. 4. In fig. 4, the connections of the operational amplifier EA1, the field-effect transistor Q1 and the second resistor R2 of the first-stage controllable current source 131 are the same as those of the above-mentioned controllable current source 13, the positive terminal of the operational amplifier EA1 of the first-stage controllable current source 131 is connected to the negative terminal of the first dc power source VOS1, the positive terminal of the first dc power source VOS1 is connected to the positive terminal of the second-stage controllable current source 132, that is, the positive terminal of the operational amplifier EA2, and the connections of the operational amplifier EA2, the field-effect transistor Q2 and the second resistor R2 of the second-stage controllable current source 132 are the same as those of the first-stage controllable current source 131, and are not described again; the connection of the third stage controllable current source 133 is similar to the connection of the second stage controllable current source 132.

The non-inverting terminal of the operational amplifier EA2 receives the offset voltage VOS1 and the output of the filter circuit 12, and the current of the field-effect transistor Q2 is slightly larger than the current of the field-effect transistor Q1 through the two superposed signals; the non-inverting terminal of the operational amplifier EA3 receives the offset voltages VOS1 and VOS2 and the output of the filter circuit 12, and the three superimposed signals set the current of the fet Q3 to be slightly larger than the current of the fet Q2. Therefore, when the controllable current source of the later stage is switched on, the controllable current source of the former stage is switched off, and the multi-path driving circuit can realize better conversion efficiency of the driving circuit when driving a plurality of LED groups. The values of the bias voltages VOS1 and VOS2 are configured to be much lower than the amplitude of the smoothed electrical signal output by the filter circuit 12, so that the influence of the bias voltages VOS1 and VOS2 on the current shape of the controllable current source 13 is as small as possible. Of course, there are many other circuit configurations that can achieve this function, as long as the controllable current source 13 of the previous stage is turned off when the controllable current source 13 of the next stage is configured to be turned on, which can meet the requirement, for example, the invention patent "a combined linear constant current source and LED driving circuit" of application No. 201310277988.1 and the invention patent "a linear constant current driving circuit" of application No. 201610323004.2 both describe specific implementations of this technology.

The pulse-free detection circuit 14 comprises a first voltage source V1, a first diode D1, a third resistor R3, a second capacitor C2 and a first comparator CM1, wherein the positive pole of the first diode D1 is connected with the pulse signal PWM, the negative pole of the first diode D1 is connected with one end of the third resistor R3, one end of the second capacitor C2 and the positive phase end of the first comparator CM1, the other end of the third resistor R3 and the other end of the second capacitor C2 are grounded, the negative phase end of the first comparator CM1 is connected with the positive pole of the first voltage source V1, the negative pole of the first voltage source V1 is grounded, and the output end of the first comparator CM1 serves as the output end of the pulse-free detection circuit 14.

The amplitude of the first voltage source V1 is set to be smaller than the high level amplitude of the pulse signal PWM. The first diode D1, the third resistor R3 and the second capacitor C2 form an asymmetric charge-discharge circuit, when the pulse signal PWM is at a high level, the first diode D1 instantly charges the second capacitor C2 to a high level, and the first comparator CM1 outputs a high level to enable the controllable current source 13; when the pulse signal PWM is at a low level, the first diode D1 is turned off, the charge on the second capacitor C2 is slowly released through the third resistor R3, after a preset time is reached, the voltage at two ends of the second capacitor C2 is lower than the amplitude of the first voltage source V1, and the first comparator CM1 flips and outputs a low level to turn off the controllable current source 13. Configuring a first preset time to be longer than the period of the pulse signal, when the duty ratio of the pulse signal PWM is not zero, the voltage on the second capacitor C2 is at a high level, and the first comparator CM1 outputs a high level to enable the controllable current source 13; when the duty ratio of the pulse signal PWM is zero, the charge and discharge circuit cannot be charged all the time, the first comparator CM1 outputs a low level all the time, and the controllable current source 13 can be completely turned off.

According to the LED dimming function, the chopper is controlled through the external pulse signal PWM, the original excitation signal is subjected to on-off control and then is output to a smooth electric signal through the filter circuit, the driving current output by the controllable current source is controlled to be in direct proportion to the duty ratio of the pulse signal, the compatibility with the PWM frequency in a wide range is achieved, and the LED dimming function has the advantages of being continuous in current, free of electromagnetic interference, free of stroboflash, capable of meeting low-brightness dimming requirements and the like in the dimming process. Meanwhile, the pulse-free detection circuit turns off the controllable current source when the duration time of the invalid level of the external pulse signal PWM is longer than first preset time, the period that the first preset time is longer than the pulse signal is configured, and the controllable current source can be turned off when the duty ratio of the external pulse signal PWM is zero.

Example 4

In this embodiment, an exciting circuit 2 for generating an external original exciting signal VR is added to the embodiment 3, and 3 LED groups are added as an LED driving circuit for the LED groups to be driven.

The original excitation signal VR is generated by the excitation circuit 2, and the output voltage signal, the output current signal, or a combination signal of the two signals may be a stable dc signal or a dc signal containing an ac component. In practice, the signal may be designed to be dependent on a number of factors, such as being temperature dependent, decreasing the output signal when the temperature reaches a predetermined threshold, etc.; for example, the signal is related to the voltage waveform of the power supply, and the signal with the same shape as the power supply voltage is output to improve the power factor; and for example, the amplitude of the power supply voltage, and outputs a signal which has an inverse monotonic variation relationship with the amplitude of the power supply voltage.

In this embodiment, 3 circuit implementations of the excitation circuit 2 are used, and of course, there are many other implementations and variations, and those skilled in the art can make changes according to actual situations without departing from the scope of the present invention.

As shown in FIG. 6, the first excitation circuit 2 includes a second DC power source VDC, generates a primary excitation signal VR, and inputs it to the pulse-controlled circuit unit 1 according to embodiments 1-3.

As shown in fig. 7, the second excitation circuit 2 includes a fourth resistor R4 and a fifth resistor R5, the excitation circuit 2 is powered by the first rectifier DB1 rectifying the output power of the utility power AC1, the positive pole of the output end of the first rectifier DB1, i.e. the positive pole of the power supply, is connected to one end of the fourth resistor R4, the other end of the fourth resistor R4 and one end of the fifth resistor R5 are connected as the output end of the excitation circuit, the original excitation signal VR is output, the other end of the fifth resistor R5 is grounded, and the negative pole of the output end of the first rectifier DB1, i.e. the negative pole of the power supply, is grounded.

The original excitation signal VR is obtained by collecting the external bus voltage of the rectified output of the mains supply through an excitation circuit 2 consisting of two resistors R4 and R5, and has low harmonic distortion. The original excitation signal VR waveform output by the excitation circuit 2 follows the voltage waveform of the alternating current AC1, and has the characteristics of high power factor and low harmonic distortion, and the output current waveform of the controllable current source generated by the circuit unit 1 also has the same characteristics. The desired performance may also be achieved within the excitation circuit or by additional configuration of the excitation signal at the time of a particular product design.

As shown in fig. 8, the third excitation circuit 2 includes a voltage-controlled current source VCCS, a second voltage source V2, a sixth resistor R6, a seventh resistor R7, and an eighth resistor R8, the excitation circuit 2 is powered by the rectified mains AC1 output power of the second rectifier DB2, the positive electrode of the output end of the second rectifier DB2, i.e. the positive electrode of the power supply, is connected to one end of the sixth resistor R6, the other end of the sixth resistor R6 is connected to one end of the seventh resistor R7 and the negative phase end of the voltage-controlled current source VCCS, the other end of the seventh resistor R7 is grounded, the positive electrode of the second voltage source V2 is connected to the positive phase end of the voltage-controlled current source VCCS, the negative electrode of the second voltage source V2 is grounded, the output end of the voltage-controlled current source VCCS is connected to one end of the eighth resistor R8 as the output end of the excitation.

The second voltage source V2 generates the excitation signal VR at the eighth resistor R8 through the voltage-controlled current source VCCS, the sixth resistor R6 detects the bus voltage, and controls the original excitation signal VR output by the excitation circuit 2 to have an inverse monotonic change relationship with the bus voltage. When the alternating current AC1 changes, the sixth resistor R6 detects the bus voltage, so that the original excitation signal VR is compensated by the bus voltage, and the compensation proportion is configured appropriately, so that the output power of the alternating current AC1 is approximately constant when the voltage of the alternating current AC1 changes, and here, the ideal configuration is that the waveform of the second voltage source V2 is the same as the waveform of the bus voltage, so that a better power factor can be obtained. Alternatively, an energy storage capacitor may be connected in parallel to the output end of the second rectifier DB2 for filtering, so as to sacrifice power factor, smooth the bus voltage and the original excitation signal VR, and reduce the light emission stroboflash of the LED, where the specific function or performance may be optimized according to actual needs, and the second voltage source V2 is a dc voltage signal.

When the power supply of the excitation circuit 2 is an ac power supply, the frequency of the pulse signal PWM is configured to be greater than the frequency of the ac power supply, so that the input terminal of the filter circuit 12 can obtain a sufficient number of sampling times.

Fig. 7 or 8 shows a schematic circuit diagram of the LED driving circuit for driving 3 LED groups, where 3 paths of driving currents output by the pulse-controlled circuit unit 1 are respectively connected to 3 LED groups L1, L2, and L3 connected in series in sequence, a positive electrode of the first LED group L1 is connected to a positive electrode of the power supply, negative electrodes of the 3 LED groups are respectively connected to output ends of 3 controllable current sources 13, and the LED groups are driven by the controllable current sources 13. When the voltage output by the alternating current AC1 is sufficient, the corresponding controllable current sources 13 are turned on, and the first LED group L1, the first LED group L1, the second LED group L2, the first LED group L1, the second LED group L2 and the third LED group L3 are lighted in turn.

When the LED driving circuit drives 1 LED group, only one path of controllable current source is needed, the anode of the LED group is connected with the anode of the power supply, and the cathode of the LED group is connected with the output end of one controllable current source.

Example 5

In this embodiment, the connection mode of the LED groups is improved based on embodiment 4.

When the LED driving circuit drives 3 LED groups, as shown in fig. 9, the LED groups further include third capacitors connected in parallel to the LED groups for smoothing current ripples of the LED groups, and a second diode is respectively connected in series between two adjacent LED groups for blocking a discharge path of the third capacitors. For example, the two ends of the first LED group L1 are connected in parallel with the third capacitor C31, the two ends of the second LED group L2 are connected in parallel with the third capacitor C32, the two ends of the third LED group L3 are connected in parallel with the third capacitor C33, the second diode D21 is connected in series between the first LED group L1 and the second LED group L2, and the second diode D22 is connected in series between the second LED group L2 and the third LED group L3.

The second diode is connected in another way, e.g. D21 and D22 in fig. 10, in series between the last two LED groups and the output of the controllable current source 13 to prevent the third capacitor from discharging through the controllable current source 13.

When the LED driving circuit drives one LED group, the two ends of the LED group are connected with the third capacitor in parallel to smooth the current ripple of the LED group.

Example 6

In this embodiment, on the basis of embodiment 4, a plurality of external pulse signals PWM are introduced to respectively control a plurality of pulse-controlled circuit units 1, and the plurality of circuit units 1 are connected to LED units with different color temperatures, so as to implement a function of adjusting color temperature of LEDs.

The LED driving circuit comprises a plurality of pulse-controlled circuit units 1 and a plurality of pulse signals PWM, the LED driving circuit further comprises a plurality of LED units, each LED unit comprises at least one LED group, different LED units have different color temperatures, the pulse signals PWM are respectively connected with one circuit unit 1, the circuit units 1 respectively drive one LED unit, and the brightness and/or the color temperature of the LED units are adjusted by adjusting the duty ratio of the pulse signals PWM.

As shown in fig. 11, the original excitation signal VR generated by the excitation circuit 2 is connected to the circuit unit I and the circuit unit II respectively, the pulse signal PWM1 is connected to the circuit unit I, the pulse signal PWM2 is connected to the circuit unit II, the circuit unit I and the circuit unit II drive the fourth LED unit L4 and the fifth LED unit L5 respectively, and the fourth LED unit L4 and the fifth LED unit L5 have different color temperatures. The current of the fourth LED unit L4 and the current of the fifth LED unit L5 can be made different by adjusting the duty ratios of the pulse signals PWM1 and PWM2, respectively, and the brightness of the fourth LED unit L4 and the brightness of the fifth LED unit L5 are adjusted, respectively, so that the brightness change or the color temperature change or the simultaneous change of the brightness and the color temperature of the LED units is realized.

Obviously, more circuit units can be used to drive more LED units according to the principle of fig. 11, so as to realize richer color temperature variation.

Example 7

The present embodiment provides an integrated circuit, which encapsulates the pulse-controlled circuit unit described in embodiments 1 to 3; alternatively, the integrated circuit is packaged with the pulse-controlled circuit units described in embodiments 1 to 3, and is packaged with a part or all of the excitation circuit described in embodiment 4.

Example 8

The present embodiment provides a lighting device, including the LED driving circuit according to embodiments 4 to 6, for LED lighting.

While specific embodiments of the invention have been described above, it will be appreciated by those skilled in the art that this is by way of example only, and that the scope of the invention is defined by the appended claims. Various changes and modifications to these embodiments may be made by those skilled in the art without departing from the spirit and scope of the invention, and these changes and modifications are within the scope of the invention.

Claims

1. A pulse-controlled circuit unit, characterized in that it comprises a chopper, a filter circuit and at least one controllable current source;

2. The pulse-controlled circuit unit of claim 1, further comprising a pulse-less detection circuit for detecting a duration of an inactive level of the pulse signal and outputting an enable signal to control the at least one controllable current source; when the duration of the invalid level is less than or equal to a first preset time, the enable signal is an active level, and the at least one controllable current source outputs the driving current; when the duration of the invalid level is longer than a first preset time, the enabling signal is the invalid level, and the at least one controllable current source is turned off; the first preset time is greater than the period of the pulse signal.

3. The pulse-controlled circuit unit according to claim 1, wherein the chopper comprises an inverter, a first switch and a second switch, the pulse signal connects an input terminal of the inverter and a control terminal of the first switch, an output terminal of the inverter connects a control terminal of the second switch, a first connection terminal of the first switch connects the original excitation signal, a second connection terminal of the first switch connects the first connection terminal of the second switch as an output terminal of the chopper, and a second connection terminal of the second switch is grounded.

4. The pulse-controlled circuit unit according to claim 1, wherein the filter circuit includes a first resistor and a first capacitor, one end of the first resistor is connected to the output terminal of the chopper, the other end of the first resistor is connected to one end of the first capacitor as the output terminal of the filter circuit, and the other end of the first capacitor is grounded.

5. The pulse-controlled circuit unit according to claim 1, wherein the controllable current source comprises an operational amplifier, a field-effect transistor and a second resistor, a non-inverting terminal of the operational amplifier is connected to the output terminal of the filter circuit, an inverting terminal of the operational amplifier is connected to a source of the field-effect transistor and one terminal of the second resistor, the other terminal of the second resistor is grounded, an output terminal of the operational amplifier is connected to a gate of the field-effect transistor, and a drain of the field-effect transistor serves as the output terminal of the controllable current source.

6. The pulse-controlled circuit unit according to claim 5, wherein when there are a plurality of the at least one controllable current source, the plurality of controllable current sources are cascaded, and the controllable current source of the previous stage is turned off when the controllable current source of the next stage is turned on.

7. The pulse-controlled circuit unit according to claim 2, wherein the pulse-less detection circuit comprises a first voltage source, a first diode, a third resistor, a second capacitor, and a first comparator, wherein an anode of the first diode is connected to the pulse signal, a cathode of the first diode is connected to one end of the third resistor, one end of the second capacitor, and a positive phase end of the first comparator, another end of the third resistor and another end of the second capacitor are grounded, a negative phase end of the first comparator is connected to an anode of the first voltage source, a cathode of the first voltage source is grounded, and an output end of the first comparator serves as an output end of the pulse-less detection circuit.

8. An LED driving circuit, characterized in that the LED driving circuit comprises a pulse-controlled circuit unit according to any one of claims 1 to 7, and further comprises an LED group, wherein the anode of the LED group is connected with the anode of a power supply, and the cathode of the LED group is connected with the output end of a controllable current source;

or, the LED driving circuit further comprises a plurality of LED groups, and the plurality of LED groups are connected in series; the positive pole of the first LED group in the LED groups is connected with the positive pole of the power supply, and the negative poles of the LED groups are respectively connected with the output end of a controllable current source.

9. The LED driving circuit according to claim 8, wherein when the LED driving circuit includes one LED group, a third capacitor is connected in parallel across the one LED group;

10. The LED driving circuit according to claim 8, wherein the LED driving circuit comprises a plurality of the circuit units and a plurality of the pulse signals, the LED driving circuit further comprises a plurality of LED units, the LED units comprise the at least one LED group, different LED units have different color temperatures, the pulse signals are respectively connected to one of the circuit units, the circuit units respectively drive one of the LED units, and the brightness and/or color temperature of the LED units are adjusted by adjusting the duty ratio of the pulse signals.

11. The LED driver circuit according to claim 8, wherein the LED driver circuit further comprises a driver circuit, the external raw driver signal being generated by the driver circuit;

or, the excitation circuit includes a fourth resistor and a fifth resistor, the positive electrode of the power supply is connected to one end of the fourth resistor, the other end of the fourth resistor and one end of the fifth resistor are connected to be used as the output end of the excitation circuit, the original excitation signal is output, and the other end of the fifth resistor is grounded;

12. An integrated circuit, wherein the integrated circuit is packaged with a pulse controlled circuit element according to any one of claims 1 to 7;

alternatively, the integrated circuit is packaged with a pulse controlled circuit unit according to any of claims 1-7 and with part or all of the excitation circuit according to claim 10.

13. A lighting device comprising the LED driving circuit according to any one of claims 9 to 11.