CN111654939A

CN111654939A - LED drive circuit, drive control circuit and drive control method

Info

Publication number: CN111654939A
Application number: CN202010536005.1A
Authority: CN
Inventors: 王曙光; 刘白仁; 尹凯; 张波
Original assignee: Xiamen Biyi Micro Electronic Technique Co ltd
Current assignee: Xiamen Biyi Micro Electronic Technique Co ltd
Priority date: 2020-06-12
Filing date: 2020-06-12
Publication date: 2020-09-11

Abstract

The invention provides an LED driving circuit, a driving control circuit and a driving control method, wherein the driving control circuit comprises a reference compensation circuit and a first regulating circuit. The reference compensation circuit is used for generating a compensation signal in a preset phase interval to reduce the current sampling signal, so that the current sampling signal is lower than a preset reference signal. The preset phase interval at least comprises part of first phase intervals, and the first phase intervals are corresponding to the open-loop control process. The first adjusting circuit is coupled to the reference compensation circuit and used for controlling the conduction state of a transistor in the LED driving circuit based on the current sampling signal and the compensation signal so as to adjust the current sampling signal. The invention provides an LED drive circuit, a drive control circuit and a drive control method, which can effectively eliminate or reduce an open-loop control process in drive control, eliminate LED lamp flicker and optimize the dimming effect of the LED drive circuit.

Description

LED drive circuit, drive control circuit and drive control method

Technical Field

The invention belongs to the technical field of power electronics, relates to a silicon controlled rectifier dimming technology, and particularly relates to an LED driving circuit, a driving control circuit and a driving control method.

Background

The silicon controlled dimming is a commonly used dimming method at present. The silicon controlled dimmer adopts a phase control method to realize dimming, namely the silicon controlled dimmer is controlled to be conducted at each half cycle of sine wave to obtain a corresponding conduction angle. The size of the conduction angle can be changed by adjusting the chopping phase of the silicon controlled dimmer, so that dimming is realized.

As shown in fig. 1, an existing linear LED driving technology includes a thyristor dimmer, a rectifier circuit, an LED lamp, and a driving control circuit. In the LED driving circuit, when the input voltage is greater than the initial conduction voltage of the LED lamp, current flows through the LED lamp; when the input voltage is lower than the initial turn-on voltage of the LED lamp, the current decreases to 0. Because LEDs are not ideal diodes, the bead voltage can vary within a certain range with the magnitude of the current flowing through it. If the minimum voltage for turning on the LED lamp is the turn-on voltage VLEDL and the voltage required to reach the set operating current iset is the LED load voltage VLEDH when the LED load is operating normally, the current flowing through the LED lamp varies with the BUS voltage when the BUS voltage is between VLEDL and VLEDH. In a common alternating current linear LED driving circuit, the voltage of the positive end of an LED lamp is a sine wave which changes along with the mains supply, and in a sine wave period, the LED lamp is switched between a conducting state and a switching-off state along with the periodic change of the BUS voltage. As can be seen from fig. 1, the operational amplifier OP1 controls the LED driving circuit according to the reference voltage Vref to output an output current fset, where fset is Vref/Rset, and Rset is an external resistor of the output current fset.

Fig. 2 is a schematic diagram of a driving waveform of the LED driving circuit with a phase-cutting angle of 0. At time period T0-T1, VBUS < VLEDL, the current flowing through the LED lamp is 0. In the time period from T1 to T2, VLEDL < VBUS < VLEDH, the current flowing through the LED lamp increases as the BUS voltage increases. At a time period of T2-T3, VBUS > VLEDH, the current flowing through the LED lamp reaches the set value iSet. In the time period from T3 to T4, VLEDL < VBUS < VLEDH, and the current flowing through the LED lamp decreases as the BUS voltage decreases. At time period T4-T5, VBUS < VLEDL, the current flowing through the LED lamp is 0.

Fig. 3 is a schematic diagram of a driving waveform of an LED driving circuit with a phase-cut angle of a certain angle. In the silicon controlled rectifier dimming application, mains supply is chopped through a silicon controlled rectifier dimmer, the obtained VBUS drives the LED lamp, and the dimming is realized by changing the conduction time of the LED lamp in a mains supply period through adjusting the phase-cutting angle of the silicon controlled rectifier dimmer. At time intervals T0-T1, the BUS voltage is chopped by the thyristor dimmer, the voltage is 0, and the current flowing through the LED lamp is 0. In the time period from T1 to T2, the point where the silicon controlled dimmer is turned on corresponds to a BUS voltage > VLEDH, and the current flowing through the LED lamp is set. In the time period from T2 to T3, VLEDL < VBUS < VLEDH, and the current flowing through the LED lamp decreases as the BUS voltage decreases. At time period T3-T4, VBUS < VLEDL, the current flowing through the LED lamp is 0. In the current linear LED current control technology, since only set is set to a large current position, the LED driving circuit cannot maintain the closed-loop control of the current flowing through the LED lamp in the process due to the low BUS voltage at the time period T2 to T3 in fig. 3. The output stage detects the voltage on the output resistor Rset through the operational amplifier OP1, compares the voltage with the internal reference voltage Vref, and controls the gate voltage of the power transistor NMOS to realize the consistency of the voltage on the Rset and the Vref, thereby realizing the effective control of the current flowing through the LED lamp. Because the power transistor NMOS has on-resistance, the Drain terminal needs to have a lowest voltage when a set current flows, and the Drain terminal voltage is already lower than the lowest voltage needed for maintaining the closed-loop control of the loop in the time period from T2 to T3, so that the loop cannot maintain the closed-loop control process. In the time stage process from T2 to T3, the current flowing through the LED lamp is greatly influenced by the BUS voltage, the BUS voltage can shake slightly due to factors such as parasitic inductance existing in an LED driving circuit, the current flowing through the LED lamp correspondingly shakes to cause flickering of the LED lamp, the shorter the conducting time of the BUS voltage is, the larger the proportion of the current flowing through the LED lamp in the whole current in the process is, and the more obvious the shaking is.

In view of the above, it is desirable to provide a new control circuit or control method for solving the above technical problems.

Disclosure of Invention

In order to solve at least part of the problems, the invention provides an LED drive circuit, a drive control circuit and a drive control method, which can effectively eliminate or reduce the adverse effect of open-loop control in LED drive control on a dimming effect, greatly improve the phenomenon of LED lamp flickering and optimize the dimming effect of the LED drive circuit.

The invention discloses a drive control circuit for an LED drive circuit, which comprises:

the reference compensation circuit is used for generating a compensation signal in a preset phase interval to reduce a current sampling signal so as to enable the current sampling signal to be lower than a preset reference signal, the current sampling signal represents the current flowing through the LED load, and the preset reference signal is used for controlling the current flowing through the LED load; the preset phase interval at least comprises a part of first phase interval, the first phase interval is a phase interval corresponding to an open-loop control process, and the open-loop control process is a process that the LED driving circuit is in an open-loop control state when the reference compensation circuit is not used for compensation; and

and the first adjusting circuit is coupled with the reference compensation circuit and used for controlling the conduction state of a transistor in the LED driving circuit based on the current sampling signal and the compensation signal so as to adjust the current sampling signal.

As an embodiment of the present invention, the reference compensation circuit includes a first detection circuit for detecting a first detection signal indicative of a phase. When the first detection signal meets a preset condition, the reference compensation circuit generates a compensation signal in a preset phase interval to reduce the current sampling signal.

As an embodiment of the present invention, the first detection circuit is configured to detect a phase-cut angle. When the phase-cutting angle reaches a set value, the reference compensation circuit generates a compensation signal within the conduction time of the LED load so as to reduce the current sampling signal.

In one embodiment of the invention, the reference compensation circuit is used for controlling and generating the compensation signal to reduce the current sampling signal when the difference value between the bus voltage and the LED load voltage when the LED load normally works reaches a threshold value in the second half period of the bus voltage period.

As an embodiment of the present invention, a current reference signal is obtained based on the preset reference signal and the compensation signal, and the current reference signal is a fixed value smaller than the preset reference signal; or the current reference signal decreases with increasing phase-cutting angle.

As an embodiment of the invention, the reference compensation circuit is configured to control the generation of the compensation signal such that a rate of decrease of the current sampling signal is greater than a first rate of decrease during at least part of the first phase interval. The first drop rate is a drop rate of the current sampling signal in the first phase zone when the reference compensation circuit is not used for compensation.

As an embodiment of the present invention, a reference compensation circuit includes:

the first timer is used for acquiring a timing signal representing the phase cutting angle through timing; and

the first signal conversion module is coupled to the first timer, and is configured to convert the timing signal into a compensation voltage signal and output the compensation voltage signal.

As an embodiment of the present invention, a reference compensation circuit includes: and the filter circuit is used for filtering the sampling voltage to obtain a filter voltage signal representing the phase cutting angle and outputting the filter voltage signal as a compensation signal.

the second timer is used for obtaining a timing signal representing the bus voltage through timing; and

and the second signal conversion module is coupled with the second timer and used for converting the timing signal into a compensation voltage signal and outputting the compensation voltage signal.

As an embodiment of the present invention, a reference compensation circuit includes: and the comparator is used for obtaining a compensation voltage signal according to the difference value of the bus voltage and the preset voltage and outputting the compensation voltage signal.

The invention discloses an LED drive circuit which comprises a silicon controlled rectifier dimmer, a rectifying circuit, an LED load and the drive control circuit.

The invention discloses a drive control method for an LED drive circuit, which comprises the following steps:

detecting a first detection signal representing a phase, and judging whether the first detection signal meets a preset condition;

when the first detection signal meets a preset condition, generating a compensation signal in a preset phase interval to reduce a current sampling signal so as to enable the current sampling signal to be lower than a preset reference signal, wherein the current sampling signal represents the current flowing through the LED load, and the preset reference signal is used for controlling the current flowing through the LED load; the preset phase interval at least comprises a part of first phase interval, the first phase interval is a phase interval corresponding to an open-loop control process, and the open-loop control process is a process that the LED driving circuit is in an open-loop control state when the reference compensation circuit is not used for compensation; and

and controlling the conduction state of a transistor in the LED driving circuit based on the current sampling signal and the compensation signal to adjust the current sampling signal.

As an embodiment of the present invention, the step of detecting the first detection signal representing the phase and determining whether the first detection signal satisfies a preset condition specifically includes: and obtaining a phase cutting angle through the first detection signal, and judging that a preset condition is met when the phase cutting angle reaches a set value.

As an embodiment of the present invention, the step of detecting the first detection signal representing the phase and determining whether the first detection signal satisfies a preset condition specifically includes: the first detection signal is bus voltage, and in the latter half period of a bus voltage period, when a difference value between the bus voltage and the LED load voltage when the LED load normally works reaches a threshold value, the first detection signal is judged to meet a preset condition.

As an embodiment of the present invention, the generating a compensation signal to reduce the current sampling signal within a preset phase interval when the first detection signal satisfies a preset condition so that the current sampling signal is lower than a preset reference signal includes:

controlling the generation of the compensation signal to make the falling rate of the current sampling signal greater than a first falling rate in at least part of the first phase interval; the first drop rate is a drop rate of the current sampling signal in the first phase zone when the reference compensation circuit is not used for compensation.

The invention provides an LED driving circuit, a driving control circuit and a driving control method. The preset phase interval at least comprises part of first phase intervals, and the first phase intervals are phase intervals corresponding to the open-loop control process. By reducing the current flowing through the LED load, the open-loop control process of the current in the first phase interval is at least partially converted into a closed-loop control process, and the current jitter flowing through the LED load can be effectively reduced. The invention can effectively eliminate or reduce the adverse effect of open-loop control on the dimming effect in the LED drive control, greatly improve the phenomenon of LED lamp flickering, and optimize the dimming effect of the LED drive circuit.

Drawings

Fig. 1 shows a schematic diagram of a prior art thyristor-dimmed LED driver circuit.

Fig. 2 shows a schematic diagram of a driving waveform of a related art LED driving circuit with a phase-cutting angle of 0.

Fig. 3 shows a schematic diagram of a driving waveform of a prior art LED driving circuit with a phase-cutting angle of a certain angle.

Fig. 4 shows a schematic diagram of a thyristor-dimmed LED driver circuit according to an embodiment of the invention.

Fig. 5 shows a schematic diagram of a thyristor-dimmed LED driver circuit according to an embodiment of the invention.

Fig. 6 shows a schematic diagram of a thyristor-dimmed LED driver circuit according to an embodiment of the invention.

Fig. 7 is a schematic diagram of a driving waveform of an LED driving circuit with a phase-cut angle at an angle according to an embodiment of the present invention.

FIG. 8 shows a first reference compensation circuit and adder schematic according to an embodiment of the invention.

FIG. 9 shows a first reference compensation circuit and adder schematic according to another embodiment of the invention.

FIG. 10 shows a schematic diagram of a first reference compensation circuit according to another embodiment of the invention.

FIG. 11 shows a second reference compensation circuit and adder schematic according to an embodiment of the invention.

FIG. 12 shows a second reference compensation circuit and adder schematic according to another embodiment of the invention.

Fig. 13 shows a drive control method for an LED drive circuit according to an embodiment of the present invention.

Detailed Description

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.

The description in this section is for several exemplary embodiments only, and the present invention is not limited only to the scope of the embodiments described. It is within the scope of the present disclosure and protection that the same or similar prior art means and some features of the embodiments may be interchanged.

The term "coupled" or "connected" in this specification includes both direct and indirect connections. An indirect connection is a connection made through an intermediate medium, such as a connection made through an electrically conductive medium, which may have parasitic inductance or parasitic capacitance; indirect connections may also include connections through other active or passive devices, such as connections through switches, follower circuits, etc., that serve the same or similar functional purpose. The description of the claims and the description relating to "first" is intended merely to generally identify a feature and is not intended to limit the invention to the best mode or to the best mode disclosed herein.

The embodiment of the invention discloses a drive control circuit for an LED drive circuit, which comprises a reference compensation circuit and a first adjusting circuit. The reference compensation circuit is used for generating a compensation signal in a preset phase interval to reduce a current sampling signal so as to enable the current sampling signal to be lower than a preset reference signal, the current sampling signal represents current flowing through the LED load, and the preset reference signal is used for controlling the current flowing through the LED load. The preset phase interval at least comprises a part of first phase interval, the first phase interval is a phase interval corresponding to an open-loop control process, and the open-loop control process is a process that the LED driving circuit is in an open-loop control state when the reference compensation circuit is not used for compensation. The first adjusting circuit is coupled to the reference compensation circuit and used for controlling the conduction state of a transistor in the LED driving circuit based on the current sampling signal and the compensation signal so as to adjust the current sampling signal. In an embodiment of the present invention, the LED driving circuit may be a linear dimming circuit. In another embodiment of the present invention, the LED driving circuit may also be a switching type dimming circuit. In the invention, the open-loop control process of the current flowing through the LED load in the first phase interval is at least partially converted into the closed-loop control process by reducing the current flowing through the LED load, so that the current jitter flowing through the LED load can be effectively reduced, and the flicker phenomenon of the LED load is improved.

As shown in fig. 4, an embodiment of the present invention discloses an LED driving circuit, which includes a thyristor dimmer 10, a rectifying circuit, an LED load, and a driving control circuit. The driving control circuit includes a first adjusting circuit 20, a reference compensating circuit 30, and other control circuits 40. The other control circuit 40 is used to ensure the normal operation of the drive control circuit. The driving control circuit is used for adjusting and controlling the output quantity of the LED driving circuit, and the adjusted and controlled output quantity can be output current, output voltage or output power. In an embodiment of the invention, the driving control circuit is used for adjusting the output current of the LED driving circuit. As shown in fig. 4, an input terminal of the reference compensation circuit 30 receives the first detection signal, and the reference compensation circuit 30 is configured to generate a compensation signal within a preset phase interval to lower a current sampling signal, which is indicative of a current flowing through the LED load, to be lower than a preset reference signal Vref. The preset phase interval at least comprises a part of first phase interval, the first phase interval is a phase interval corresponding to an open-loop control process, and the open-loop control process is a process that the LED driving circuit is in an open-loop control state when the reference compensation circuit is not used for compensation. Whether the open-loop control process is performed or not depends on the negative terminal voltage of the LED load shown in fig. 4 (i.e., the drain terminal voltage of the transistor shown in fig. 4), and if the negative terminal voltage of the LED load is lower than the minimum voltage required for maintaining the LED load to operate at a certain operating current, the open-loop control process is performed (since the transistor Q has on-resistance, when a certain operating current flows through the transistor, the drain terminal voltage needs to have a minimum voltage, and if the drain terminal voltage is lower than the minimum voltage, the LED driving circuit is in the open-loop control process), otherwise, the closed-loop control process is performed. When the working current of the LED load is changed, the minimum voltage required by the closed-loop control process is correspondingly changed. In an embodiment of the present invention, as shown in fig. 4, the driving control circuit further includes an adder, an input terminal of the adder receives the preset reference signal Vref and the compensation signal, and the adder obtains the current reference signal Vref' based on the preset reference signal Vref and the compensation signal. In addition, the input terminal of the first adjusting circuit 20 is coupled to the adder and the collecting terminal of the current sampling signal, respectively, and the first adjusting circuit 20 is configured to control the conducting state of the transistor in the LED driving circuit based on the current sampling signal and the current reference signal Vref' to adjust the current sampling signal. In the present embodiment, the current reference signal Vref' is obtained based on the preset reference signal Vref and the compensation signal, and it can be understood that the first adjusting circuit 20 is configured to control the on-state of the transistor in the LED driving circuit based on the current sampling signal and the compensation signal to adjust the current sampling signal. In a specific embodiment, as shown in fig. 4, the first adjusting circuit 20 includes an operational amplifier OP1, a non-inverting input terminal of the operational amplifier OP1 is coupled to the output terminal of the adder, and an inverting input terminal of the operational amplifier OP1 is coupled to a sampling resistor, through which a current sampling signal is obtained, the current sampling signal being indicative of the current flowing through the LED load. The operational amplifier OP1 outputs a driving signal to control the on-state of a transistor in the LED driving circuit according to the current sampling signal and the current reference signal Vref' to regulate the current flowing through the LED load.

As shown in fig. 5, an embodiment of the present invention discloses an LED driving circuit, which includes a thyristor dimmer 10, a rectifying circuit, an LED load, a driving control circuit, and other control circuits 40. The drive control circuit includes a first adjusting circuit 20 and a reference compensating circuit 30. An input of the reference compensation circuit 30 receives the first detection signal, and the reference compensation circuit 30 is configured to generate a compensation signal within a predetermined phase interval to reduce the current sampling signal, so that the current sampling signal is lower than a predetermined reference signal Vref, and the current sampling signal represents a current flowing through the LED load. In an embodiment of the present invention, the predetermined phase interval includes all of the first phase intervals, so that the LED driving circuit is in the closed-loop control process in the first phase intervals. The driving control circuit further comprises an adder, wherein the input end of the adder receives the current sampling signal and the compensation signal, and the adder obtains the compensated current sampling signal through the current sampling signal and the compensation signal. In addition, the input end of the first adjusting circuit 20 is coupled to the output end of the adder and the preset reference signal Vref, respectively, and the first adjusting circuit 20 is configured to control the on state of the transistor in the LED driving circuit based on the preset reference signal Vref and the compensated current sampling signal to adjust the current sampling signal. In practice, the compensated current sampling signal is obtained based on the current sampling signal and the compensation signal, and in this embodiment, the current reference signal may be obtained based on a preset reference signal and the compensation signal, and the current reference signal is a reference signal directly corresponding to the current for controlling the current flowing through the LED load. Therefore, it can be understood that the first adjusting circuit 20 is used for controlling the on-state of the transistor in the LED driving circuit based on the current sampling signal and the compensation signal to adjust the current sampling signal.

As shown in fig. 6, an embodiment of the present invention discloses an LED driving circuit, which includes a thyristor dimmer 10, a rectifying circuit, an LED load, and a driving control circuit. The drive control circuit includes a first adjusting circuit 20, a reference compensating circuit 30, and other control circuits 40. Reference compensation circuit 30 includes a first reference compensation circuit 310 and a second reference compensation circuit 320. The input of the first reference compensation circuit 310 receives the first detection signal, and the output of the first reference compensation circuit 310 outputs Vref 1. An input of the second reference compensation circuit 320 is coupled to an output of the first reference compensation circuit 310, and an output of the second reference compensation circuit 320 outputs the compensation signal Vref2 to an input of the adder. When the phase-cut angle satisfies the preset condition, the reference compensation circuit 30 controls to generate the compensation signal Vref2 to lower the current sampling signal from fset to fset'. The current sampling signals shown in fig. 7, i.e., I set '(dotted line segment) in the interval T1' to T2 'and I set' (dotted line segment) in the interval T2 'to T3' are obtained by the first reference compensation circuit 310 and the second reference compensation circuit 320. In the embodiment, the whole conduction state of the LED drive circuit can be in the closed-loop control process, the current jitter flowing through the LED load can be effectively eliminated, and the flicker of the LED load is avoided.

In yet another embodiment of the present invention, reference compensation circuit 30 includes a first reference compensation circuit 310, an input of first reference compensation circuit 310 receiving the first detection signal, an output of first reference compensation circuit 310 outputting compensation signal Vref1 to an input of the first adjustment circuit. The first reference compensation circuit 310 is configured to generate a compensation signal Vref1 within a preset phase interval to lower the current sampling signal so that the current sampling signal is lower than the preset reference signal. As shown in fig. 7, when the on-phase is changed from T1 to T1 ', the phase-cut angle at this time is large, and the preset condition has been satisfied, the first reference compensation circuit 310 controls the generation of the compensation signal Vref1 to lower the current sampling signal from I set to I set'. In fig. 7, VLEDH is the LED load voltage when the LED load is operating normally, and VLEDL is the initial turn-on voltage of the LED load. When the current through the LED load is reduced to Iset', two changes occur: (1) and the voltage at the two ends of the LED load is reduced and is closer to VLEDL, so that the bus voltage VBUS required by the current closed-loop control process of the LED drive circuit is reduced. (2) The current flowing through the transistor Q decreases, meaning that the voltage required at the drain of the transistor Q decreases. Therefore, the bus voltage VBUS required for the closed-loop control process of the current decreases, the corresponding closed-loop control time is prolonged from T2 to T2', and the open-loop control process is shortened.

In an embodiment of the present invention, the reference compensation circuit 30 includes a second reference compensation circuit 320, an input terminal of the second reference compensation circuit 320 receives the first detection signal, and an output terminal of the second reference compensation circuit 320 outputs the compensation signal to an input terminal of the adder. The second reference compensation circuit 320 is configured to generate a compensation signal within a preset phase interval to reduce the current sampling signal so that the current sampling signal is lower than the preset reference signal. As shown in fig. 7, in the first phase zone, the current sampling signal (which is a dotted line segment from T2 'to T3' in fig. 7) is decreased at a constant speed at the phase corresponding to T2 'to T3' so that the rate of decrease of the current sampling signal is greater than the first rate of decrease of the current sampling signal in the first phase zone when the compensation is not performed using the reference compensation circuit. The rate of decrease is (value before decrease-value after decrease)/value before decrease. As can be seen from fig. 7, in the phase interval from T2 'to T3, since the falling rate of the current sampling signal is greater than the first falling rate, the current sampling signal I set' is smaller, and the LED driving circuit can maintain the closed-loop control process, the open-loop control process is effectively shortened. In another embodiment of the present invention, the current sampling signal is reduced at a certain speed at or before the phase corresponding to the voltage VLEDH, so that the current sampling signal is reduced to zero by the LED driving circuit before the phase corresponding to T3, the whole conducting state of the LED driving circuit can be in the process of closed-loop control, the current jitter flowing through the LED load can be effectively eliminated, and the flicker of the LED load can be avoided.

In one embodiment of the invention, the reference compensation circuit includes a first detection circuit for detecting a first detection signal indicative of the phase. In an embodiment of the present invention, the first detection signal may be a time signal, a phase signal, and/or a bus voltage VBUS, etc. When the first detection signal meets a preset condition, the reference compensation circuit generates a compensation signal according to a preset reference signal in a preset phase interval so as to reduce the current sampling signal.

In an embodiment of the invention, the first detection circuit is used for detecting the phase cutting angle. When the phase-cut angle reaches a set value, the reference compensation circuit generates a compensation signal according to a preset reference signal within the conduction time of the LED load so as to reduce the current sampling signal, so that the current sampling signal is lower than the preset reference signal.

In an embodiment of the invention, the reference compensation circuit is configured to, in a second half period of the bus voltage period, control to generate the compensation signal to reduce the current sampling signal when a difference between the bus voltage and an LED load voltage when the LED load normally operates reaches a threshold value, so that the current sampling signal is lower than a preset reference signal. Namely, when the bus voltage is close to the LED load voltage when the LED load normally works, the reference compensation circuit controls and generates a compensation signal, so that the current sampling signal is lower than a preset reference signal.

In an embodiment of the present invention, the current reference signal may be obtained based on a preset reference signal and the compensation signal, and the current reference signal is a fixed value smaller than the preset reference signal. In another embodiment of the present invention, the current reference signal decreases as the phase-cut angle increases.

In an embodiment of the invention, the reference compensation circuit controls the generation of the compensation signal so that the falling rate of the current sampling signal is greater than the first falling rate in at least part of the first phase interval. The first fall rate is a fall rate of the current sampling signal in the first phase zone when the compensation operation is not performed by the reference compensation circuit.

In an embodiment of the present invention, the reference compensation circuit includes a first timer and a first signal conversion module, and the first signal conversion module is configured to convert a received digital signal or an analog signal into an analog signal. In an embodiment of the invention, the first signal conversion module is a first digital-to-analog conversion module. As shown in fig. 8, the reference compensation circuit 310 includes a first timer and a first digital-to-analog conversion module DAC 1. The first timer is used for obtaining a timing signal representing the phase cutting angle through timing. Illustratively, the first timer obtains a timing signal by timing the TO-T1 phase interval shown in fig. 7, that is, starting from the time when the bus voltage is zero, and ending the timing at the bus voltage corresponding TO the T1 phase. The first DAC module DAC1 is coupled to the first timer, the first DAC module DAC1 is configured to convert the timing signal into a compensation voltage signal Vref1 (i.e., a compensation signal), and the first DAC module DAC1 outputs the compensation voltage signal Vref 1. The driving control circuit further comprises an adder coupled to the first DAC1, the adder being configured to generate a current reference signal Vref' according to the preset reference signal Vref and the compensation voltage signal Vref1, the current reference signal being a reference signal directly corresponding to a current for controlling the current flowing through the LED load. The compensation voltage signal Vref1 may be a positive or negative value, and the current reference signal is calculated accordingly: vref + Vref1 or Vref + Vref 1.

As shown in fig. 9, in one embodiment of the present invention, the reference compensation circuit 310 includes a filter circuit. The filter circuit is used for filtering the sampling voltage to obtain a filter voltage signal Vref1 (i.e. a compensation signal) representing the phase cutting angle, and the output end of the filter circuit outputs a filter voltage signal Vref 1. The sampled voltage may be the bus voltage, the voltage at the negative terminal of the LED load, or the voltage drop across a sampling resistor. The driving control circuit further comprises an adder coupled to an output of the filtering circuit, the adder being configured to generate a current reference signal Vref' according to the preset reference signal Vref and the filtered voltage signal Vref 1. As shown in fig. 10, in an embodiment of the invention, the filter circuit includes a first voltage dividing resistor R1, a second voltage dividing resistor R2, a third resistor R3 and a first capacitor C1. The input end of the filter circuit receives the bus voltage, and the output end of the filter circuit is respectively coupled with the third resistor R3 and the first capacitor C1. The output voltage Vout of the filter circuit is the filtered voltage signal Vref 1. Since the bus voltage VBUS is a high voltage, the bus voltage VBUS is divided by the first voltage dividing resistor R1 and the second voltage dividing resistor R2 inside the driving control circuit IC to obtain a divided voltage signal. If the bus voltage is the mains frequency, the divided voltage signal is still the variation signal of the mains frequency, and the divided voltage signal of VBUS is filtered into a constant direct current voltage signal through a low-pass filter composed of a third resistor R3 and a first capacitor C1. The magnitude of the phase-cut angle is reflected by the magnitude of the dc voltage signal, and the larger the phase-cut angle is, the lower the effective value of the bus voltage VBUS is, and the lower the output voltage Vout of the filter circuit is, so that the magnitude of the phase-cut angle is reflected by the filter voltage signal Vref 1. In an embodiment of the present invention, the filtered voltage signal Vref1 may be used to obtain Vref' varying with the phase cut angle by overlapping with the preset reference signal Vref.

In an embodiment of the invention, the reference compensation circuit includes a second timer and a second signal conversion module, and the second signal conversion module is configured to convert a received digital signal or an analog signal into an analog signal. In an embodiment of the invention, the second signal conversion module is a second digital-to-analog conversion module. As shown in fig. 11, the reference compensation circuit 320 includes a second timer and a second digital-to-analog conversion module DAC 2. The second timer is used for obtaining a timing signal representing the bus voltage through timing. The input terminal of the second digital-to-analog conversion module is coupled to the output terminal of the second timer, and the second digital-to-analog conversion module is configured to convert the timing signal into the compensation voltage signal Vref 2. One phase is selected as a timing starting point in a bus voltage period, and each phase is selected as a timing ending point in the second half period of the bus voltage period. The longer the timing time, the smaller the corresponding bus voltage. That is, in the second half period of the bus voltage, the bus voltage gradually decreases, the timing signal gradually increases, and the magnitude of the obtained compensation voltage signal Vref2 gradually increases. The driving control circuit further comprises an adder, an input end of the adder is coupled to an output end of the second digital-to-analog conversion module, and if the reference compensation circuit comprises a second reference compensation circuit (not comprising the first reference compensation circuit), the adder is configured to generate a current reference signal Vref' according to a preset reference signal Vref and the compensation voltage signal Vref 2. As can be seen from Vref '═ Vref + (-Vref2), Vref2 increases in magnitude as the bus voltage decreases, and Vref' decreases accordingly. In another embodiment, the reference compensation circuit comprises a first reference compensation circuit and a second reference compensation circuit, and the drive control circuit further comprises an adder for generating the current reference signal Vref' from the Vref1 generated by the first reference compensation circuit and the compensation voltage signal Vref 2.

As shown in fig. 12, in one embodiment of the present invention, the reference compensation circuit includes a comparator. The comparator is used for obtaining a compensation voltage signal Vref2 (i.e. a compensation signal) according to a difference value between the bus voltage VBUS and the preset voltage Vref _ led, and an output end of the comparator outputs the compensation voltage signal Vref 2. Preferably, the preset voltage Vref _ LED is an LED load voltage when the LED load normally operates. The driving control circuit further comprises an adder, an input terminal of the adder is coupled to an output terminal of the comparator, and if the reference compensation circuit comprises a second reference compensation circuit (not comprising the first reference compensation circuit), the adder is configured to generate the current reference signal Vref' according to the preset reference signal Vref and the compensation voltage signal Vref 2. When the bus voltage VBUS is lower than the Vref _ led, a Vref2 which changes along with the difference is obtained through the comparator, and the preset reference signal Vref and the compensation voltage signal Vref2 are superposed to obtain a current reference signal Vref'. In another embodiment, the reference compensation circuit comprises a first reference compensation circuit and a second reference compensation circuit, and the adder is configured to generate the current reference signal Vref' from the Vref1 and the compensation voltage signal Vref2 generated by the first reference compensation circuit.

The embodiment of the invention discloses an LED driving circuit, which comprises a silicon controlled rectifier dimmer, a rectifying circuit, an LED load and the driving control circuit. The input end of the controlled silicon dimmer can be coupled with power frequency input voltage, the output end of the controlled silicon dimmer is coupled with the rectifying circuit, and bus voltage VBUS can be obtained after rectification by the rectifying circuit. The drive control circuit is used for controlling the output quantity of the LED drive circuit. In an embodiment of the invention, the driving control circuit sends out a driving signal to control the conduction state of the transistor, so as to regulate the current flowing through the LED load.

As shown in fig. 13, an embodiment of the present invention discloses a driving control method for an LED driving circuit, the driving control method including:

s100, detecting a first detection signal representing a phase, and judging whether the first detection signal meets a preset condition;

s100, when the first detection signal meets a preset condition, generating a compensation signal in a preset phase interval to reduce a current sampling signal, so that the current sampling signal is lower than a preset reference signal, wherein the current sampling signal represents the current flowing through the LED load, and the preset reference signal is used for controlling the current flowing through the LED load; the preset phase interval at least comprises a part of first phase interval, the first phase interval is a phase interval corresponding to an open-loop control process, and the open-loop control process is a process that the LED driving circuit is in an open-loop control state when a reference compensation circuit is not used for compensation; and

and S100, controlling the conduction state of a transistor in the LED driving circuit based on the current sampling signal and the compensation signal to adjust the current sampling signal.

In an embodiment of the present invention, the step of detecting the first detection signal representing the phase and determining whether the first detection signal satisfies the predetermined condition specifically includes: and obtaining a phase cutting angle through the first detection signal, and judging that the preset condition is met when the phase cutting angle reaches a set value.

In an embodiment of the present invention, the step of detecting the first detection signal representing the phase and determining whether the first detection signal satisfies the predetermined condition specifically includes: the first detection signal is bus voltage, and in the second half period of a bus voltage period, when a difference value between the bus voltage and the LED load voltage when the LED load normally works reaches a threshold value, the bus voltage and the LED load voltage are judged to meet a preset condition.

In an embodiment of the present invention, a current reference signal may be obtained based on a preset reference signal and a compensation signal, the current reference signal being a fixed value smaller than the preset reference signal; or the current reference signal decreases with increasing phase-cut angle.

In an embodiment of the present invention, when the first detection signal satisfies a predetermined condition, the step of generating a compensation signal according to a predetermined reference signal within a predetermined phase interval to reduce the current sampling signal so that the current sampling signal is lower than the predetermined reference signal includes:

controlling the generation of the compensation signal so that the falling rate of the current sampling signal is larger than a first falling rate in at least part of the first phase interval; the first fall rate is a fall rate of the current sampling signal in the first phase zone when the compensation operation is not performed by the reference compensation circuit.

The invention provides an LED driving circuit, a driving control circuit and a driving control method. The preset phase interval at least comprises part of first phase intervals, and the first phase intervals are phase intervals corresponding to the open-loop control process. By reducing the current flowing through the LED load, the open-loop control process in the first phase interval is at least partially converted into a closed-loop control process, and the current jitter flowing through the LED load can be effectively reduced. The invention can effectively eliminate or reduce the adverse effect of open-loop control on the dimming effect in the LED drive control, greatly improve the phenomenon of LED lamp flickering, and optimize the dimming effect of the LED drive circuit.

The above description and applications of the invention herein are illustrative and are not intended to limit the scope of the invention to the above described embodiments. The descriptions related to the effects or advantages mentioned in the embodiments may not be reflected in the experimental examples due to the uncertainty of the specific condition parameters, and are not used for limiting the embodiments. Variations and modifications of the embodiments disclosed herein are possible, and alternative and equivalent various components of the embodiments will be apparent to those skilled in the art. It will be clear to those skilled in the art that the present invention may be embodied in other forms, structures, arrangements, proportions, and with other components, materials, and parts, without departing from the spirit or essential characteristics thereof. Other variations and modifications of the embodiments disclosed herein may be made without departing from the scope and spirit of the invention.

Claims

1. A drive control circuit for an LED drive circuit, the drive control circuit comprising:

2. The drive control circuit of claim 1, wherein the reference compensation circuit comprises a first detection circuit for detecting a first detection signal indicative of a phase; when the first detection signal meets a preset condition, the reference compensation circuit generates a compensation signal in a preset phase interval to reduce the current sampling signal.

3. The drive control circuit according to claim 2, wherein the first detection circuit is configured to detect a phase-cut angle; when the phase-cutting angle reaches a set value, the reference compensation circuit generates a compensation signal within the conduction time of the LED load so as to reduce the current sampling signal.

4. The drive control circuit of claim 2, wherein the reference compensation circuit is configured to control the generation of the compensation signal to decrease the current sampling signal when a difference between the bus voltage and an LED load voltage at which the LED load operates normally reaches a threshold value in a second half of a period of the bus voltage.

5. The drive control circuit according to claim 3, wherein a current reference signal is obtained based on the preset reference signal and the compensation signal, the current reference signal being a fixed value smaller than the preset reference signal; or the current reference signal decreases with increasing phase-cutting angle.

6. The drive control circuit of claim 1, wherein the reference compensation circuit is configured to control the generation of the compensation signal such that a rate of decrease of the current sample signal is greater than a first rate of decrease during at least a portion of the first phase interval; the first drop rate is a drop rate of the current sampling signal in the first phase zone when the reference compensation circuit is not used for compensation.

7. The drive control circuit of claim 1, wherein the reference compensation circuit comprises:

8. The drive control circuit of claim 1, wherein the reference compensation circuit comprises:

and the filter circuit is used for filtering the sampling voltage to obtain a filter voltage signal representing the phase cutting angle and outputting the filter voltage signal as a compensation signal.

9. The drive control circuit of claim 1, wherein the reference compensation circuit comprises:

10. The drive control circuit of claim 1, wherein the reference compensation circuit comprises:

and the comparator is used for obtaining a compensation voltage signal according to the difference value of the bus voltage and the preset voltage and outputting the compensation voltage signal.

11. An LED driving circuit comprising a thyristor dimmer, a rectifier circuit, an LED load and a drive control circuit as claimed in any one of claims 1 to 10.

12. A drive control method for an LED drive circuit, characterized by comprising:

13. The driving control method according to claim 12, wherein the step of detecting the first detection signal indicative of the phase and determining whether the first detection signal satisfies a predetermined condition is specifically: and obtaining a phase cutting angle through the first detection signal, and judging that a preset condition is met when the phase cutting angle reaches a set value.

14. The driving control method according to claim 12, wherein the step of detecting the first detection signal indicative of the phase and determining whether the first detection signal satisfies a predetermined condition is specifically: the first detection signal is bus voltage, and in the latter half period of a bus voltage period, when a difference value between the bus voltage and the LED load voltage when the LED load normally works reaches a threshold value, the first detection signal is judged to meet a preset condition.

15. The drive control method according to claim 12, characterized in that a current reference signal is obtained based on the preset reference signal and the compensation signal, the current reference signal being a fixed value smaller than the preset reference signal; or the current reference signal decreases with increasing phase-cutting angle.

16. The drive control method according to claim 12, wherein the step of generating a compensation signal to lower a current sampling signal within a preset phase section so that the current sampling signal is lower than a preset reference signal when the first detection signal satisfies a preset condition comprises: