CN112512170B - LED control circuit, LED driving device and driving control method - Google Patents

LED control circuit, LED driving device and driving control method Download PDF

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Publication number
CN112512170B
CN112512170B CN202011225937.0A CN202011225937A CN112512170B CN 112512170 B CN112512170 B CN 112512170B CN 202011225937 A CN202011225937 A CN 202011225937A CN 112512170 B CN112512170 B CN 112512170B
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signal
unit
analog
turn
coupled
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CN112512170A (en
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姚云龙
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Hangzhou Silan Microelectronics Co Ltd
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Hangzhou Silan Microelectronics Co Ltd
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/32—Pulse-control circuits
    • H05B45/325—Pulse-width modulation [PWM]
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/10—Controlling the intensity of the light
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
    • Y02B20/40—Control techniques providing energy savings, e.g. smart controller or presence detection

Abstract

An LED control circuit, an LED driving device and a driving control method, wherein the LED control circuit comprises: analog signal conversion unit, output current calculation unit, error amplification unit and drive arrangement, wherein: the input end of the analog signal conversion unit is input with a PWM dimming signal, and the analog signal conversion unit is suitable for calculating the PWM dimming signal to obtain an analog reference control signal representing dimming brightness; the output current calculation unit is used for calculating a sampling signal obtained by sampling the LED current to obtain an equivalent current signal representing the magnitude of the LED current; the first input end of the error amplifying unit is coupled with the output end of the analog signal conversion unit, and the second input end of the error amplifying unit is coupled with the output end of the output current calculation unit to generate error voltage; and a driving device, one end of which is input with an error voltage, and generates a driving signal according to the error voltage and outputs the driving signal. The LED lamp flashing situation can be avoided through the scheme.

Description

LED control circuit, LED driving device and driving control method
Technical Field
The present invention relates to the field of LED technologies, and in particular, to an LED control circuit, an LED driving device, and a driving control method.
Background
In the conventional LED driving apparatus, the brightness of the LED lamp is adjusted using the PWM signal. The PWM signal is processed by the PWM waveform shaping unit to generate a control signal PWM1, the PWM1 signal is used as an enabling control signal to control the enabling of the driving signal. When the PWM1 signal is high, a driving pulse is generated; when the PWM1 signal is low, no driving pulse is generated.
When the PWM signal is used for directly controlling the enabling of the driving signal, if the brightness of the LED lamp is regulated to be low, the duty ratio of the PWM signal is smaller, namely the time of the PWM signal in a high level is shorter, and the time of the driving enabling is also shorter. For the switching power supply, the number of driving pulses is small, if the PWM signal is slightly dithered, the number of driving pulses is increased or decreased by one, and the LED lamp is obviously perceived as flashing.
Disclosure of Invention
The embodiment of the invention solves the technical problem of how to avoid the flashing of the LED lamp.
In order to solve the above technical problems, an embodiment of the present invention provides an LED control circuit, including an analog signal conversion unit, an output current calculation unit, an error amplification unit, and a driving device, wherein: the input end of the analog signal conversion unit is input with a PWM dimming signal, and the analog signal conversion unit is suitable for calculating the PWM dimming signal to obtain an analog reference control signal representing dimming brightness; the output current calculation unit is characterized in that a sampling signal obtained by sampling the LED current is input to the input end of the output current calculation unit, and the sampling signal is calculated to obtain an equivalent current signal representing the LED current; the first input end of the error amplifying unit is coupled with the output end of the analog signal converting unit, the second input end of the error amplifying unit is coupled with the output end of the output current calculating unit, and error between the analog reference control signal and the equivalent current signal is amplified to generate error voltage; and a driving device, one end of which is input with the error voltage, and generates a driving signal according to the error voltage and outputs the driving signal.
Optionally, the analog signal conversion unit is adapted to perform average value calculation on the PWM dimming signal to obtain the analog reference control signal.
Optionally, the driving device includes: an on signal generating unit, an off signal generating unit, wherein: the first input end of the turn-off signal generating unit is coupled with the output end of the error amplifying unit and is suitable for generating a turn-off signal according to the error voltage; and the input end of the turn-on signal generation unit is input with the analog reference control signal and/or the error voltage, and is suitable for generating a turn-on signal under the control of the analog reference control signal and/or the error voltage.
Optionally, the driving device further includes: flip-flop and logic drive unit, wherein: the first setting end of the trigger is coupled with the output end of the turn-off signal generating unit, and the second setting end of the trigger is coupled with the output end of the turn-on signal generating unit and is suitable for generating a trigger signal according to the turn-off signal and the turn-on signal; the input end of the logic driving unit is coupled with the output end of the trigger, and is suitable for generating and outputting the driving signal according to the trigger signal.
Optionally, the analog signal conversion unit includes a first output terminal; the first output end of the analog signal conversion unit is coupled with the first input end of the error amplification unit, and outputs a first analog reference control signal to the error amplification unit.
Optionally, the first input end of the turn-on signal generating unit is coupled with the output end of the error amplifying unit, receives the error voltage, and generates a turn-on signal according to the error voltage; when the error voltage decreases, the on delay of the on signal generated by the on signal generating unit increases, resulting in an increase in the off time of the driving signal.
Optionally, the LED control circuit further includes: a current zero-crossing detection unit; the current zero-crossing detection unit is used for detecting zero crossing of the inductance current and outputting a zero-crossing detection signal to the opening signal generation unit; under the zero current on mode, the on signal generating unit is controlled by the zero crossing detection signal, and generates the on signal when the zero crossing detection signal is detected and the off time reaches the minimum off time.
Optionally, the on signal generating unit and the off signal generating unit receive the sampling signal; in a hysteresis current working mode, the error voltage controls the minimum turn-off time corresponding to the driving signal and the minimum peak voltage of the sampling signal; when the sampling signal is smaller than the minimum peak voltage and the turn-off time is longer than the minimum turn-off time, the turn-on signal generating unit generates the turn-on signal.
Optionally, the LED control circuit further includes: an oscillator unit; the input end of the oscillator unit is input with the error voltage and is suitable for generating an oscillation signal and respectively inputting the oscillation signal to the turn-off signal generating unit and the turn-on signal generating unit; the on signal generating unit and the off signal generating unit respectively generate an on signal and an off signal according to the oscillating signal, and the error voltage controls the frequency of the oscillating signal and the duty ratio of the driving signal.
Optionally, the analog signal conversion unit further includes a second output terminal, and outputs a second analog reference control signal.
Optionally, the first input end of the turn-on signal generating unit is coupled with the second output end of the analog signal converting unit, receives the second analog reference control signal, and generates the turn-on signal according to the second analog reference control signal; when the second analog reference control signal decreases, the on delay of the on signal generated by the on signal generating unit increases, resulting in an increase in the off time of the driving signal.
Optionally, the first input end of the turn-on signal generating unit is coupled with the output end of the error amplifying unit, and receives the error voltage; a second input end of the analog signal conversion unit is coupled with a second output end of the analog signal conversion unit, and receives the second analog reference control signal; generating the turn-on signal according to the second analog reference control signal and the error voltage; when the second analog reference control signal and/or the error voltage is reduced, the turn-on delay of the turn-on signal generated by the turn-on signal generating unit is increased, resulting in an increase in turn-off time of the driving signal.
Optionally, in the peak current control mode, the off signal generating unit generates the off signal when detecting that the peak value of the LED current reaches the peak current controlled by the error voltage.
Optionally, in the fixed on-time control mode, the off signal generating unit generates the off signal when the on-time is detected to reach the error voltage and/or the on-time controlled by the second analog reference control signal.
Optionally, the LED control circuit further includes: a current zero-crossing detection unit; the current zero-crossing detection unit is used for detecting zero crossing of the inductance current and outputting a zero-crossing detection signal to the opening signal generation unit; under the zero current on mode, the on signal generating unit is controlled by the zero crossing detection signal and the second analog reference control signal, and generates the on signal when the zero crossing detection signal is detected and the off time reaches the minimum off time.
Optionally, the on signal generating unit and the off signal generating unit receive the sampling signal; in a hysteresis current working mode, the second analog reference control signal and/or the error voltage control the minimum turn-off time corresponding to the driving signal and the minimum peak voltage of the sampling signal; when the sampling signal is smaller than the minimum peak voltage and the turn-off time is longer than the minimum turn-off time, the turn-on signal generating unit generates the turn-on signal.
Optionally, the LED control circuit further includes: an oscillator unit; the input end of the oscillator unit is input with the second analog reference control signal and/or the error voltage, and is suitable for generating an oscillation signal and respectively inputting the oscillation signal to the turn-off signal generating unit and the turn-on signal generating unit; the on signal generating unit and the off signal generating unit generate an on signal and an off signal according to the oscillation signal, respectively, and the second analog reference control signal and/or the error voltage control the frequency of the oscillation signal and the duty ratio of the driving signal.
Optionally, the analog signal conversion unit includes: the first transconductance amplifying module, the second filter capacitor and the amplifier module, wherein: the first transconductance amplifying module has a first input end coupled with the input end of the analog signal converting unit, a second input end coupled with the first output end of the amplifier module, and an output end coupled with the input end of the amplifier module and the first end of the second filter capacitor; the first output end of the amplifier module is coupled with the first output end of the analog signal conversion unit, and the second output end of the amplifier module is coupled with the second output end of the analog signal conversion unit; and the second end of the second filter capacitor is grounded.
Optionally, the analog signal conversion unit includes: the system comprises a second transconductance amplifying module, a third filter capacitor, a pulse generating module, an addition and subtraction counting module and a digital-to-analog conversion module, wherein: the first input end of the second transconductance amplifying module is coupled with the input end of the analog signal converting unit, the second input end of the second transconductance amplifying module is coupled with the first output end of the digital-to-analog converting module, and the output end of the second transconductance amplifying module is coupled with the input end of the pulse generating module and the first end of the third filter capacitor; the output end of the pulse generation module is coupled with the input end of the addition and subtraction counting module, and is suitable for generating addition and subtraction pulses and outputting the addition and subtraction pulses to the addition and subtraction counting module when the charge and discharge electric quantity of the third filter capacitor reaches a preset value; the output end of the addition and subtraction counting module is coupled with the input end of the digital-to-analog conversion module and is suitable for counting the addition and subtraction pulses; the digital-to-analog conversion module is characterized in that a first output end of the digital-to-analog conversion module is coupled with a first output end of the analog signal conversion unit, and a second output end of the digital-to-analog conversion module is coupled with a second output end of the analog signal conversion unit, and is suitable for converting the count value of the addition-subtraction count module into a corresponding first analog reference control signal and a corresponding second analog reference control signal; and the second end of the third filter capacitor is grounded.
Optionally, the LED control circuit further includes: the input end of the clamping and subtracting unit inputs a PWM dimming signal or an analog dimming signal, the PWM dimming signal or the analog dimming signal is subjected to clamping and subtracting operation, and the output end of the clamping and subtracting unit is coupled with the input end of the analog signal converting unit and is suitable for obtaining dimming control voltage and outputting the dimming control voltage to the analog signal converting unit; and the analog signal conversion unit is used for calculating the dimming control voltage to obtain the analog reference control signal.
Optionally, the clamping and subtracting unit includes: operational amplifier module, first resistance, second resistance and switching tube, wherein: the first end of the first resistor receives a reference voltage, and the second end of the first resistor is coupled with the first end of the second resistor and the first input end of the operational amplification module; the second input end of the operational amplification module inputs the PWM dimming signal or the analog dimming signal, and the output end of the operational amplification module is coupled with the control end of the switching tube; the second end of the second resistor is coupled with the first end of the switching tube and the output end of the clamping and subtracting unit; the second end of the switching tube is grounded.
The embodiment of the invention also provides an LED driving device, which comprises: the power conversion unit, the power conversion unit includes freewheel diode, inductance, power switch tube and current sampling resistance, LED drive arrangement still includes: an LED control circuit as described in any one of the above; wherein: the driving signal output by the LED control circuit is coupled with the control end of the power switch tube so as to control the power switch tube to be turned on or turned off; the first end of the current sampling resistor is coupled with the input end of the output current calculation unit and the first end of the power switch tube, the second end of the current sampling resistor is grounded, and the second end of the power switch tube is connected with the inductor.
Optionally, the power conversion unit is any one of the following: buck-boost circuitry, flyback circuitry, boost circuitry.
The embodiment of the invention also provides an LED driving control method, which comprises the following steps: receiving a PWM dimming signal; calculating the PWM dimming signal to obtain an analog reference control signal representing dimming brightness; and generating a driving signal according to the analog reference control signal, and driving the LED by adopting the driving signal so as to adjust the brightness of the LED.
Optionally, the calculating the PWM dimming signal includes: and calculating the average value of the PWM dimming signal.
Optionally, when the analog reference control signal decreases, the off time of the driving signal increases.
Optionally, the method further comprises: and receiving an input analog dimming signal, and calculating the analog dimming signal to obtain an analog reference control signal representing dimming brightness.
Compared with the prior art, the technical scheme of the embodiment of the invention has the following beneficial effects:
the PWM dimming signal is input to the analog signal conversion unit, the PWM dimming signal is calculated through the analog signal conversion unit, an analog reference control signal representing the dimming brightness is obtained, compatibility of the PWM dimming signal and an analog dimming pin (used for inputting the analog dimming signal) can be realized, and continuous adjustment of the LED brightness is realized. When the brightness of the LED is lower, the output current is controlled in a closed loop mode by reducing the working frequency, so that the output current of the LED can be accurately controlled, and the condition of LED lamp flashing is avoided.
Drawings
Fig. 1 is a schematic structural view of an LED driving device according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of an LED control circuit according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of another LED control circuit in an embodiment of the invention;
FIG. 4 is a schematic diagram of another LED control circuit in accordance with an embodiment of the present invention;
FIG. 5 is a schematic diagram of a clamping and subtracting unit according to an embodiment of the present invention;
FIG. 6 is a graph of the input and output of the clamping and subtracting unit provided in FIG. 5;
fig. 7 is a schematic structural diagram of an average unit in an embodiment of the present invention;
fig. 8 is a schematic diagram of the structure of another average unit in the embodiment of the present invention;
fig. 9 is a schematic diagram of the structure of a further average unit in the embodiment of the present invention;
FIG. 10 is a schematic diagram of a conventional LED control circuit;
fig. 11 is a waveform diagram of control signals of a conventional LED control circuit;
fig. 12 is a waveform diagram of a control signal of an LED control circuit in an embodiment of the present invention;
fig. 13 is a flowchart of an LED driving control method in an embodiment of the present invention.
Detailed Description
Referring to fig. 10, a schematic diagram of a conventional LED control circuit is shown. In fig. 10, after the PWM dimming signal passes through the PWM wave shaping unit, a control signal PWM1 is generated. The LED control circuit further comprises a driving on-off unit control unit, a logic control unit, an enabling control unit and a driving device, wherein the driving device outputs a driving signal GATE when the enabling control unit is enabled. The enable control unit is controlled by a control signal PWM1. When the control signal PWM1 is at a high level, the enable control unit enables, and the driving signal GATE is at a high level; when the control signal PWM1 is at a low level, the enable control unit is turned off, and the driving signal GATE is at a low level, and no energy is transferred.
If the brightness of the LED is adjusted to be low, the duty ratio of the corresponding control signal PWM1 is small, that is, the time when the control signal PWM1 is at the high level is short and the time when the control signal PWM1 is at the low level is long. At this time, the driving enable time is also short. For the switching power supply, the number of pulses of the driving signal GATE is small, if the PWM dimming signal is slightly dithered, the number of pulses of the driving signal GATE is increased or decreased by one, and the LED lamp flash can be obviously felt, so that the PWM is directly used for enabling control, and the problem of LED lamp flash can exist.
In summary, when the brightness of the LED lamp is low, the brightness of the LED lamp is adjusted, and the lamp flash phenomenon is easy to occur.
In the embodiment of the invention, the PWM dimming signal is input to the analog signal conversion unit, the analog signal conversion unit is used for calculating the PWM dimming signal to obtain the analog reference control signal representing the dimming brightness, and the compatibility of the PWM dimming signal and the analog dimming pin can be realized, so that the continuous adjustment of the LED brightness is realized. When the brightness of the LED is lower, the output current is controlled in a closed loop mode by reducing the working frequency, so that the output current of the LED can be accurately controlled, and the condition of LED lamp flashing is avoided. In order to make the above objects, features and advantages of the present invention more comprehensible, embodiments accompanied with figures are described in detail below.
Referring to fig. 1, a schematic structure of an LED driving device according to an embodiment of the present invention is shown. In the embodiment of the invention, the LED driving device may include a rectifier bridge 101, an input filter capacitor 102, a freewheeling diode 103, an inductor 104, an output capacitor 105, an LED lamp 106, a power switch tube 107, and a sampling resistor 108. The LED driving device may provide power to the LED lamp 106.
In fig. 1, a flywheel diode 103, an inductor 104, and a power switching tube 107 constitute a power conversion unit. It can be understood that the structure of the power conversion unit is not limited to the above description, but may be a buck-boost circuit, a flyback circuit, a boost circuit, etc., which are not repeated in the embodiments of the present invention.
In the embodiment of the present invention, a first end of the inductor 104 is coupled to a first end of the power switch tube 107, and a second end of the inductor 104 is coupled to a first end of the LED lamp 106; the control end of the power switch tube 107 inputs a driving signal GATE, and the second end of the power switch tube 107 is coupled with the first end of the sampling resistor 108; the second end of the sampling resistor 108 is grounded, and the sampling resistor 108 is used for sampling the LED current to obtain a sampling signal Vcs.
In an embodiment of the present invention, the power switch 107 may be an NMOS transistor. The first end of the NMOS tube is a drain electrode, the second end of the NMOS tube is a source electrode, and the control end of the NMOS tube is a grid electrode. In an embodiment of the present invention, the LED driving device further includes an LED control circuit 20.
Referring to fig. 2, a schematic diagram of an LED control circuit in an embodiment of the present invention is provided. In particular implementations, the LED control circuit 20 may include: an analog signal conversion unit 202, an output current calculation unit 203, an error amplification unit 204, and a driving device, wherein:
the input end of the analog signal conversion unit 202 can input a PWM dimming signal, and the received PWM dimming signal is calculated to obtain an analog reference control signal representing dimming brightness;
the input end of the output current calculating unit 203 may input a sampling signal Vcs obtained by sampling the LED current, and calculate the sampling signal Vcs to obtain an equivalent current signal Vb representing the magnitude of the LED current;
a first input terminal of the error amplifying unit 204 may be coupled to an output terminal of the analog signal converting unit 202, receiving the analog reference control signal, and a second input terminal of the error amplifying unit 204 may be coupled to an output terminal of the output current calculating unit 203, receiving the equivalent current signal Vb; the error amplifying unit 204 may amplify an error between the analog reference control signal and the equivalent current signal Vb to obtain an error voltage Vcomp;
one end of the driving device inputs error voltage and generates corresponding driving signal GATE according to the error voltage
And output.
Each of the above units is described in detail below.
In a specific implementation, the driving device may include an on signal generating unit 205 and an off signal generating unit 206, where:
a first input terminal of the shutdown signal generating unit 206 is coupled to the output terminal of the error amplifying unit 204, and is adapted to generate a shutdown signal according to the error voltage Vcomp;
the input terminal of the turn-on signal generating unit 205 inputs an analog reference control signal and/or an error voltage Vcomp, and is adapted to generate a turn-on signal under the control of the analog reference control signal and/or the error voltage Vcomp. The driving signal generated by the driving device can be composed of an on signal and an off signal.
In a specific implementation, the analog signal conversion unit 202 may be an average unit, and perform average calculation on the input PWM dimming signal to obtain an analog reference control signal representing the dimming brightness.
In other embodiments of the present invention, the input end of the analog signal conversion unit 202 may also input an analog dimming signal, and calculate the received analog dimming signal to obtain an analog reference control signal. In other words, the analog signal conversion unit 202 may realize compatibility of the PWM dimming signal with the analog dimming signal.
Since the embodiment of the present invention is mainly directed to an application scenario in which the dimming signal is a PWM dimming signal, in the following embodiment, the dimming signal input to the input terminal of the analog signal conversion unit 202 is a PWM dimming signal unless otherwise described. The analog reference control signal may include at least one of a first analog reference control signal and a second analog reference control signal.
In a specific implementation, the analog signal conversion unit 202 may include a first output terminal, and the first output terminal of the analog signal conversion unit 202 outputs the first analog reference control signal Vref1. A first output terminal of the analog signal conversion unit 202 is coupled to a first input terminal of the error amplification unit 204, and outputs a first analog reference control signal Vref1 to the first input terminal of the error amplification unit 204. At this time, the error voltage Vcomp output by the error amplifying unit 204 is: a voltage obtained by amplifying an error between the first analog reference control signal Vref1 and the equivalent current signal.
In a specific implementation, the analog signal conversion unit 202 may further include a second output terminal. A second output terminal of the analog signal conversion unit 202 may be coupled to a first input terminal of the turn-on signal generating unit 205, and output a second analog reference control signal Vref2 to the first input terminal of the turn-on signal generating unit 205.
In an implementation, the turn-on signal generating unit 205 may further include a second input terminal, and the second input terminal of the turn-on signal generating unit 205 may be coupled to the output terminal of the error amplifying unit 204. The on signal generation unit 205 may be controlled only by the second analog reference control signal Vref 2; the on signal generation unit 205 may be controlled only by the error voltage Vcomp; the turn-on signal generating unit 205 may also be controlled by the second analog reference control signal Vref2 and the error voltage Vcomp at the same time.
In other words, in one embodiment of the present invention, the turn-on signal generating unit 205 includes only the first input terminal, and is controlled by the second analog reference control signal Vref2 input from the first input terminal thereof to generate the turn-on signal.
In another embodiment of the present invention, the turn-on signal generating unit 205 includes only the second input terminal, and is controlled by the error voltage Vcomp input from the second input terminal thereof to generate the turn-on signal.
In yet another embodiment of the present invention, the turn-on signal generating unit 205 includes a first input terminal and a second input terminal, and is controlled by the second analog reference control signal Vref2 and the error voltage Vcomp together to generate the turn-on signal.
In a specific implementation, the first analog reference control signal Vref1 is related to the second analog reference control signal Vref2, and the two signals may be in a proportional relationship or the same.
In the embodiment of the present invention, the second analog reference control signal Vref2 and/or the error voltage Vcomp control the on signal generating unit 207, and adjusts the duty ratio or the frequency of the driving signal by adjusting the minimum off time of the power switching tube 107 or the minimum switching period of the power switching tube 107. Specifically, when the second analog reference control signal Vref2 and/or the error voltage Vcomp decreases, the minimum off time of the power switch 107 is increased, and the on time of the corresponding on signal increases, resulting in an increase in the off time of the driving signal GATE.
As can be seen from the above embodiments, the first analog reference control signal Vref1 and the second analog reference control signal Vref2 are both related to the PWM dimming signal, and therefore, the brightness of the LED can be adjusted by at least one of the first analog reference control signal Vref1 and the second analog reference control signal Vref 2.
In a specific implementation, an input terminal of the output current calculating unit 203 is coupled to the sampling resistor 108 for sampling the current of the LED lamp 106, and an output terminal of the output current calculating unit 203 is coupled to a second input terminal of the error amplifying unit 204. The output current calculation unit 203 calculates the sampling signal Vcs to obtain an equivalent current signal Vb that characterizes the current level of the LED lamp 106.
In an embodiment, a first input terminal of the error amplifying unit 204 is coupled to a first output terminal of the analog signal converting unit 202, and receives a first analog reference control signal Vref1; a second input end of the error amplifying unit 204 is coupled with an output end of the output current calculating unit 203, and receives an equivalent current signal Vb; the output of the error amplification unit 204 is coupled to a first input of the off signal generation unit 206.
The error amplifying unit 204 amplifies the error between the two input signals, that is, the error between the equivalent current signal Vb and the first analog reference control signal Vref1, to obtain an error voltage Vcomp, and inputs the error voltage Vcomp to the first input terminal of the off signal generating unit 206.
In peak current control mode, the error voltage Vcomp may determine the current peak of the inductor current flowing through inductor 104. The off signal generation unit 206 may determine a current peak value of the inductor current according to the received error voltage Vcomp. When detecting that the peak current value of the inductor current flowing through the inductor 104 reaches the peak current value controlled by the error voltage Vcomp, the turn-off signal generating unit 206 may generate a turn-off signal and output the turn-off signal to the control terminal of the power switching tube 107 to control the power switching tube 107 to be turned off.
The error voltage Vcomp may also determine an on time of the power switch 107, and the off signal generating unit 206 determines whether to generate the off signal according to the on time of the power switch 107.
In the embodiment of the present invention, in the fixed on-time control mode, when the off-signal generating unit 206 detects that the on-time of the power switch 107 reaches the on-time controlled by the error voltage Vcomp, an off-signal is generated and output to the control terminal of the power switch 107 to control the power switch 107 to be turned off.
In implementations, the LED control circuit 20 may also include a flip-flop 207. The first set terminal of the flip-flop 207 is coupled to the output terminal of the off signal generating unit 206, and the second set terminal of the flip-flop 207 is coupled to the output terminal of the on signal generating unit 205. The trigger 207 may generate a trigger signal according to a turn-off signal input from the first set terminal and a turn-on signal input from the second set terminal.
In implementations, the LED control circuit 20 may also include a logic drive unit 208. An input terminal of the logic driving unit 208 is coupled to an output terminal of the flip-flop 207, and is adapted to generate a driving signal GATE according to the trigger signal output by the flip-flop 207, and output the driving signal GATE to the control terminal of the power switch tube 107.
In an implementation, the first set terminal of the flip-flop 207 is the 0-set terminal of the flip-flop 207. The output end of the shutdown signal generating unit 206 is coupled to the 0-terminal of the trigger 207, and the shutdown signal generating unit 206 generates a shutdown signal according to the error voltage Vcomp output by the error amplifying unit 204 and outputs the shutdown signal to the 0-terminal of the trigger 207.
In an implementation, the second set terminal of the flip-flop 207 is the set 1 terminal of the flip-flop 207. The output end of the turn-on signal generating unit 205 is coupled to the 1-terminal of the trigger 207, and the turn-on signal generating unit 205 generates an on signal according to the second analog reference control signal Vref2 and/or the error voltage Vcomp output by the analog signal converting unit 202, and outputs the on signal to the 1-terminal of the trigger 207.
As shown in fig. 2, taking the trigger 207 as an RS trigger as an example, the R end of the RS trigger 207 is the 0 end of the RS trigger 207, and the S end is the 1 end of the RS trigger 207. Therefore, the R terminal of the RS flip-flop 207 is coupled to the output terminal of the off signal generating unit 206, and the S terminal of the RS flip-flop 207 is coupled to the output terminal of the on signal generating unit 205.
The flip-flop 207 shown in the embodiment of the present invention is exemplified as an RS flip-flop. It is understood that the flip-flop 207 may be any of a JK flip-flop, a D flip-flop, a T flip-flop, and the like. In other variant embodiments, any of the triggers 207 described above may be used, and the embodiments of the present invention will not be described in detail.
The logic driving unit 208 may output a corresponding driving signal GATE after receiving the trigger signal output from the trigger 207. In practical applications, when the LED control circuit 20 is applied to the LED driving device, the driving signal output by the logic driving unit 208 may be output to the control terminal of the power switch tube 107 to control the power switch tube 107 to be turned on or turned off.
Two dashed lines are shown in fig. 2, which are respectively the connection line between the second output terminal of the analog signal conversion unit 202 and the first input terminal of the turn-on signal generation unit 205, and the connection line between the output terminal of the error amplification unit 204 and the second input terminal of the turn-on signal generation unit 205, where the meaning of the dashed lines is: either one of the above two connection relationships may be selected, or both may be selected at the same time.
That is, the turn-on signal generating unit 205 may include only a first input terminal, and input the second analog reference control signal Vref2. The turn-on signal generating unit 205 may include only the second input terminal, and input the error voltage Vcomp. The turn-on signal generating unit 205 may also include a first input terminal and a second input terminal, where the first input terminal of the turn-on signal generating unit 205 inputs the second analog reference control signal Vref2, and the second input terminal of the turn-on signal generating unit 205 inputs the error voltage Vcomp, and the turn-on signal generating unit 205 is controlled by the second analog reference control signal Vref2 and the error voltage Vcomp.
In a specific implementation, the LED control circuit 20 may further include a current zero crossing detection unit 210.
In the embodiment of the present invention, referring to fig. 1, an input terminal of the current zero-crossing detection unit 210 is connected to a control terminal of the power switch tube 107, and an output terminal of the current zero-crossing detection unit 210 is coupled to a third input terminal of the turn-on signal generating unit 205. The current zero-crossing detection unit 210 outputs a zero-crossing signal in response to zero crossing of the inductor current flowing through the inductor 104.
In the zero-current on mode, if the on signal generating unit 205 includes only the first input terminal, the on signal generating unit 205 is controlled by the zero-crossing signal and the error voltage Vcomp at the same time, and generates and outputs an on signal under the condition that the zero-crossing detection signal is detected to be satisfied and/or the minimum off time is reached.
In the zero-current on mode, if the on signal generating unit 205 includes only the second input terminal, the on signal generating unit 205 is controlled by the zero-crossing signal and the second analog reference control signal Vref2 at the same time, and generates and outputs an on signal when the condition that the zero-crossing detection signal is satisfied and/or the minimum off time is reached is detected.
In the zero-current on mode, if the on signal generating unit 205 includes a first input terminal and a second input terminal, the first on signal generating unit 205 is controlled by the zero-crossing signal, the second analog reference control signal Vref2, and the error voltage Vcomp at the same time, and generates and outputs an on signal when the condition that the zero-crossing detection signal is satisfied and/or the minimum off time is reached is detected.
In a specific implementation, the LED control circuit may further comprise an oscillator unit. Referring to fig. 3, a schematic diagram of another LED control circuit in an embodiment of the present invention is provided.
In the embodiment of the present invention, the oscillator unit 301 may include one input terminal or two input terminals. In fig. 3, the connection between the two inputs of the oscillator unit 301 and the second output of the analog signal conversion unit 202 and the output of the error amplification unit 204 is schematically indicated by a dashed line, which characterizes the following three connection relations:
the oscillator unit 301 may include only one input terminal, and the input terminal is coupled to the second output terminal of the analog signal conversion unit 202 and receives the second analog reference control signal Vref2;
the oscillator unit 301 may comprise only one input terminal coupled to the output terminal of the error amplifying unit 204, receiving the error voltage Vcomp;
the oscillator unit 301 includes a first input terminal and a second input terminal, and the first input terminal of the oscillator unit 301 is coupled to the second output terminal of the analog signal conversion unit 202, and receives the second analog reference control signal Vref2; a second input of the oscillator unit 302 is coupled to the output of the error amplifying unit 204, receiving the error voltage Vcomp.
A first output terminal of the oscillator unit 301 is coupled to a second input terminal of the turn-off signal generating unit 206, and a second output terminal of the oscillator unit 301 is coupled to a fourth input terminal of the turn-on signal generating unit 205.
Under control of the input signal, the oscillator unit 301 generates an oscillation signal, and the output of the oscillator unit 301 is input to the off signal generation unit 206 and the on signal generation unit 205, respectively. The frequency of the oscillation signal is controlled by the second analog reference control signal Vref2 and/or the error voltage Vcomp, which determines the duty cycle of the drive signal GATE.
If the oscillator unit 301 includes only one input terminal, and the input terminal is coupled to the second output terminal of the analog signal conversion unit 202, the input signal is the second analog reference control signal Vref2, and the frequency of the oscillating signal is controlled by the second analog reference control signal Vref 2.
If the oscillator unit 301 includes only one input terminal coupled to the output terminal of the error amplifying unit 204, the input signal is the error voltage Vcomp, and the frequency of the oscillating signal is controlled by the error voltage Vcomp.
If the oscillator unit 301 includes two input terminals, a first input terminal thereof inputs the second analog reference control signal Vref2, and a second input terminal thereof inputs the error voltage Vcomp, the frequency of the oscillation signal is commonly controlled by the second analog reference control signal Vref2 and the error voltage Vcomp.
Referring to fig. 4, a schematic diagram of a structure of still another LED control circuit in an embodiment of the present invention is given. In the embodiment of the present invention, the fifth input terminal of the on signal generating unit 205 may further input the sampling signal Vcs, and the third input terminal of the off signal generating unit 206 may further input the sampling signal Vcs. In fig. 4, at least one of the broken line between the analog signal conversion unit 202 and the on signal generation unit 205, and the broken line between the error amplification unit 204 and the on signal generation unit 205 is substantially connected.
That is, the turn-on signal generating unit 205 may include only a first input terminal, and input the second analog reference control signal Vref2. The turn-on signal generating unit 205 may include only the second input terminal, and input the error voltage Vcomp. The turn-on signal generating unit 205 may also include a first input terminal and a second input terminal, where the first input terminal of the turn-on signal generating unit 205 inputs the second analog reference control signal Vref2, and the second input terminal of the turn-on signal generating unit 205 inputs the error voltage Vcomp, and the turn-on signal generating unit 205 is controlled by the second analog reference control signal Vref2 and the error voltage Vcomp.
In the hysteresis current operation mode, the on signal generating unit 205 is controlled by the second analog reference control signal Vref2 and/or the error voltage Vcomp and the sampling signal Vcs, and the minimum off time of the off signal generating unit 206 and the minimum peak voltage Vcsmin of the sampling signal Vcs are controlled by the second analog reference control signal Vref2 and/or the error voltage Vcomp. When the sampling signal Vcs is smaller than the minimum peak voltage Vcsmin and the turn-off time corresponding to the driving signal (i.e., the time when the driving signal GATE controls the power switch 107 to turn off) is greater than the minimum turn-off time, the turn-on signal generating unit 205 outputs the turn-on signal. The off signal generating unit 206 outputs an off signal when the inductor current reaches a peak current controlled by the error voltage Vcomp.
Dimming the LED lamp 106, when the brightness of the LED lamp 106 is high, in a continuous operation mode, when the inductance current reaches the peak current controlled by the error voltage Vcomp, the turn-off signal generating unit 206 outputs a turn-off signal to turn off the power switching tube 107; when the sampling signal Vcs is smaller than the minimum peak voltage Vcsmin, the on signal generating unit 205 outputs an on signal to turn on the power switching tube 107. When the brightness of the LED lamp 106 is low, the minimum peak voltage Vcsmin is reduced to 0, and in the intermittent operation mode, when the inductance current reaches the peak current controlled by the error voltage Vcomp, the turn-off signal generating unit 206 outputs a turn-off signal to turn off the power switching tube 107; when the on signal generating unit 205 detects that the off time of the power switching tube 107 reaches the minimum off time, the on signal generating unit 205 outputs an on signal to turn on the power switching tube 107.
It should be noted that, in the embodiment of the present invention, the input end of the turn-on signal generating unit 205 includes a first input end to a fifth input end, and the five input ends are only used for distinguishing different input signals, which does not mean that the turn-on signal generating unit 205 must include the five input ends at the same time, but only needs to include a part thereof; furthermore, it is not meant that the on signal generation unit 205 includes only the above-described five inputs.
For example, with the scheme corresponding to fig. 1, the turn-on signal generating unit 205 may include only 1 input terminal (the first input terminal for inputting the second analog reference control signal Vref 2), may include only 2 input terminals (the first input terminal for inputting the second analog reference control signal Vref2, the second input terminal for inputting the error voltage Vcomp), and may include 3 input terminals (the first input terminal for inputting the second analog reference control signal Vref2, the second input terminal for inputting the error voltage Vcomp, and the third input terminal for inputting the zero-crossing signal).
Accordingly, the shutdown signal generation unit 206 also includes a plurality of inputs, which are also only used to distinguish between different input signals.
In implementations, the LED control circuit 20 may also include a loop compensation capacitor 209. A first end of the loop compensation capacitor 209 is coupled to the output of the error amplification unit 204, and a second end of the loop compensation capacitor 209 is grounded.
In a specific implementation, the LED control circuit 20 may further comprise a clamping and subtracting unit 201. The PWM dimming signal may be input to the clamping and subtracting unit 201, to obtain a dimming control voltage Va, and input to the analog signal converting unit 202, the dimming control voltage Va being related to the PWM dimming signal. The analog signal conversion unit 202 may perform average value calculation on the dimming control voltage Va output by the clamping and subtracting unit, to obtain an analog reference control signal.
Referring to fig. 5, a schematic diagram of a clamping and subtracting unit 201 in an embodiment of the present invention is provided. In a specific implementation, the clamping and subtracting unit 201 may include: an operational amplifier 501, a first resistor 502, a second resistor 503, and a switching tube 504, wherein:
the first end of the first resistor 502 inputs the reference voltage Vref, and the second end of the first resistor 502 is coupled to the first end of the second resistor 503 and the first input end of the operational amplifier 501;
a second input terminal of the operational amplifier 501 inputs a dimming signal Vdim, and an output terminal of the operational amplifier 501 is coupled to a gate of the switching tube 504; the dimming signal Vdim may be a PWM dimming signal or an analog dimming signal; the dimming signal in the embodiment of the invention can be a PWM dimming signal;
A second end of the second resistor 503 and a drain electrode of the switching tube 504 are coupled with an output end of the subtraction unit 201;
the source of the switching tube 504 is grounded.
In implementations, the switching tube 504 may be an NMOS tube.
In the embodiment of the present invention, the first input terminal of the operational amplifier 501 may be a "+" terminal, and the second input terminal of the operational amplifier 501 may be a "-" terminal.
When the voltage input by the second input terminal of the operational amplifier 501 is higher than the voltage input by the first input terminal of the operational amplifier 501, that is, the dimming signal Vdim is greater than the reference voltage Vref, the switching tube 504 is turned off, and the dimming control voltage Va is equal to the reference voltage Vref; when the dimming signal Vdim is less than Vref R503/(r502+r503), the dimming control voltage va=0; when the dimming signal Vdim is greater than vref×r503/(r502+r503) and the dimming signal Vdim is less than the reference voltage Vref, the dimming control voltage va= [ Vdim (r502+r503) -vref×r503]/r502; r502 is the resistance value of the first resistor 502, and R503 is the resistance value of the second resistor 503.
Referring to fig. 6, a graph of input-output characteristics of the clamp and subtract unit 201 provided in the above-described embodiment of the present invention is given. As can be seen from fig. 6, by using the clamping and subtracting means 201 to perform the high clamping and subtracting function on the input PWM dimming signal and to perform the high clamping and subtracting the fixed value on the voltage of the input PWM signal, the voltage of the PWM dimming signal can be reduced, and the minimum brightness of the analog dimming can be reduced.
Referring to fig. 7, a schematic diagram of an analog signal conversion unit 202 in an embodiment of the present invention is provided. In a specific embodiment, the analog signal conversion unit 202 may include: a third resistor 701 and a first filter capacitor 702, wherein:
a first end of the third resistor 701 is coupled to the input end of the analog signal conversion unit 202, and receives the dimming control voltage Va, and a second end of the third resistor 701 is coupled to the output end of the analog signal conversion unit 202;
a first end of the first filter capacitor 702 is coupled to the output end of the analog signal conversion unit 202, and a second end of the first filter capacitor 702 is grounded.
In a specific implementation, the first end of the third resistor 701 may be an input end of the analog signal conversion unit 202, and the first end of the first filter capacitor 702 may be an output end of the analog signal conversion unit 202, so as to output the first analog reference control signal Vref1 and the second analog reference control signal Vref2.
The analog signal conversion unit 202 provided in fig. 7 may be regarded as an RC filter circuit, and performs average calculation on the analog dimming signal or the PWM dimming signal.
In implementation, the circuit structure of the analog signal conversion unit 202 may also be other structures.
Referring to fig. 8, a schematic diagram of an analog signal conversion unit 202 according to another embodiment of the present invention is shown, and fig. 1 to 4 are combined. In an implementation, the analog signal conversion unit 202 includes: a first transconductance amplification module 801, a second filter capacitor 802, and an amplifier module 803, wherein:
a first input end of the first transconductance amplifying module 801 is coupled to an input end of the analog signal converting unit 202, receives the dimming control voltage Va, a second input end of the first transconductance amplifying module 801 is coupled to a first output end of the amplifier module 803, and an output end of the first transconductance amplifying module 801 is coupled to an input end of the amplifier module 803 and a first end of the second filter capacitor 802;
a first output terminal of the amplifier module 803 is coupled to a first output terminal of the analog signal conversion unit 202, a second output terminal of the amplifier module 803 is coupled to a second output terminal of the analog signal conversion unit 202, a first analog reference control signal Vref1 and a second analog reference control signal Vref2 are output respectively,
the second terminal of the second filter capacitor 802 is grounded.
In a specific implementation, the first input terminal of the first transconductance amplifying module 801 may also be an input terminal of the analog signal converting unit 202. The first output terminal of the amplifier module 803 may be the first output terminal of the analog signal conversion unit 202, and the second output terminal of the amplifier module 803 may be the second output terminal of the analog signal conversion unit 202.
In a specific implementation, when the frequency of the input PWM dimming signal is low, if a relatively stable analog reference control signal is to be obtained, the analog signal conversion unit 202 provided in fig. 7 requires a relatively large RC constant, the analog signal conversion unit 202 provided in fig. 8 requires that Gm of the first transconductance amplifying module 801 is relatively small and the capacitance of the second filter capacitor 802 is relatively large, which is difficult to be integrated in a chip.
In order to achieve a smooth analog reference control signal output when the frequency of the PWM dimming signal is low, a schematic diagram of the structure of the further analog signal conversion unit 202 in the embodiment of the present invention is given with reference to fig. 9.
In an implementation, the analog signal conversion unit 202 includes: a second transconductance amplifying module 901, a third filter capacitor 902, a pulse generating module 903, an up-down counting module 904, and a digital-to-analog conversion module 905, wherein:
the first input end of the second transconductance amplification module 901 is coupled to the input end of the analog signal conversion unit 202, receives the dimming control voltage Va, the second input end of the second transconductance amplification module 901 is coupled to the first output end of the digital-to-analog conversion module 905, and the output end of the second transconductance amplification module 901 is coupled to the input end of the pulse generation module 903 and the first end of the third filter capacitor 902;
The output end of the pulse generation module 903 is coupled with the input end of the up-down counting module 904; when the charge and discharge electric quantity of the third filter capacitor 902 reaches a preset value, an add-subtract pulse is generated and output to the add-subtract counting module 904;
the output end of the up-down counting module 904 is coupled with the input end of the digital-to-analog conversion module 905 to count up-down pulses;
a first output end of the digital-to-analog conversion module 905 is coupled to a first output end of the analog signal conversion unit 202, and a second output end of the digital-to-analog conversion module 905 is coupled to a second output end of the analog signal conversion unit 202, and outputs a first analog reference control signal Vref1 and a second analog reference control signal Vref2 respectively;
the second terminal of the third filter capacitor 902 is grounded.
In a specific implementation, the first input terminal of the second transconductance amplifying module 901 may also be an input terminal of the analog signal converting unit 202. The first output terminal of the digital-to-analog conversion module 905 may be the first output terminal of the analog signal conversion unit 202, and the second output terminal of the digital-to-analog conversion module 905 may be the second output terminal of the analog signal conversion unit 202.
It is understood that if the analog signal conversion unit 202 includes only one output terminal, the digital-to-analog conversion module 905 also includes only one output terminal.
In the embodiment of the present invention, the input voltage at the first input end of the second transconductance amplifying module 901 is the dimming control voltage Va generated by the clamping and subtracting unit 201, and the output signal at the first output end of the digital-to-analog converting module 905 is the first analog reference control signal Vref1 at the first output end of the analog signal converting unit 202.
When there is a deviation between the dimming control voltage Va and the first analog reference control signal Vref1, charging and discharging of the third filter capacitor 902 occur correspondingly. When the charge/discharge power reaches the set value Q, the pulse generation module 903 generates an add-subtract pulse, and at this time, the power corresponding to the third filter capacitor 902 is cleared. The up-down counting module 904 counts the pulses output from the pulse generating module 903, and converts the counted pulses into a digital signal indicating the accumulated error of the third filter capacitor 902, and the digital signal is input to the digital-to-analog conversion module 905, and the digital-to-analog conversion module 905 obtains the first analog reference control signal Vref1 and the second analog reference control signal Vref2.
Referring to fig. 11, a waveform diagram of a control signal of an LED control circuit of the related art is given. When the control signal PWM1 is at a high level, the driving enable is generated, i.e. the driving signal GATE is generated; when the control signal PWM1 is low, the driving is turned off, i.e., no driving signal GATE is generated.
Referring to fig. 12, a waveform diagram of an analog reference control signal of an LED control circuit in an embodiment of the present invention is given. As can be seen from fig. 12, on the time axis, the analog reference control signal of the LED control circuit in the embodiment of the invention is always in the enabled state, i.e. the driving signal GATE is always generated during the whole dimming process.
From the above, the PWM dimming signal is input to the analog signal conversion unit, and an analog signal corresponding to the PWM dimming signal is obtained as an analog reference control signal. And solving and amplifying errors of an equivalent current signal representing the current of the LED and an analog reference control signal to obtain error voltage, and controlling the turn-off signal generating unit to output a turn-off signal by using the error voltage, namely controlling the turn-on time of the power switch tube. Meanwhile, the on signal generated by the on signal generating unit is controlled by using the analog reference control signal, when the analog reference control signal is smaller, the on delay of the on signal is increased, and then the turn-off time of the switching tube is increased, so that the accurate control of the output current of the LED is realized when the continuous reduction of the output current of the LED can be ensured, and the condition of LED flash is avoided.
The embodiment of the invention also provides a LED driving control method, and the method is described by specific steps with reference to FIG. 13.
In step S301, an input PWM dimming signal is received.
In implementations, a user may trigger a dimming module when there is a need to dim an LED. The dimming module generates a corresponding PWM dimming signal after detecting the triggering action of the user equipment, and inputs the generated PWM dimming signal to the control circuit.
Step S302, the PWM dimming signal is calculated to obtain an analog reference control signal representing the dimming brightness.
In a specific implementation, the control module may receive the input PWM dimming signal and calculate the PWM dimming signal to obtain an analog reference control signal that characterizes the dimming brightness.
In the embodiment of the invention, the control module can calculate the average value of the PWM dimming signal to obtain the average value of the PWM dimming signal as the analog reference control signal.
Step S303, generating a driving signal according to the analog reference control signal, and driving the LED by using the driving signal.
In a specific implementation, after the analog reference control signal is obtained, a driving signal may be generated according to the analog reference control signal, and the generated driving signal is used to drive the LED, so as to adjust the brightness of the LED.
In the embodiment of the invention, when the analog reference control signal is reduced, the turn-off time of the corresponding driving signal is increased, so that the output current of the LED is ensured to be continuously reduced, and when the analog reference control signal is converted, the turn-off time of the corresponding driving signal is changed, so that the output current of the LED is ensured to be continuously changed, further, the accurate control of the output current of the LED is realized, and the condition of flashing of the LED lamp is avoided.
In a specific implementation, the control module may also receive an input analog dimming signal, and calculate the analog dimming signal to obtain an analog reference control signal representing the dimming brightness.
In the embodiment of the invention, the control module can receive the input PWM dimming signal and also can input the analog dimming signal, so that the compatibility of digital dimming and analog signals can be realized.
Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention, and the scope of the invention should be assessed accordingly to that of the appended claims.

Claims (22)

1. An LED control circuit, comprising: analog signal conversion unit, output current calculation unit, error amplification unit and drive arrangement, wherein:
the input end of the analog signal conversion unit is input with a PWM dimming signal, and the analog signal conversion unit is suitable for calculating the PWM dimming signal to obtain an analog reference control signal representing dimming brightness;
the output current calculation unit is characterized in that a sampling signal obtained by sampling the LED current is input to the input end of the output current calculation unit, and the sampling signal is calculated to obtain an equivalent current signal representing the LED current;
The first input end of the error amplifying unit is coupled with the output end of the analog signal converting unit, the second input end of the error amplifying unit is coupled with the output end of the output current calculating unit, and error between the analog reference control signal and the equivalent current signal is amplified to generate error voltage;
a driving device, one end of which is input with the error voltage, and generates a driving signal according to the error voltage and outputs the driving signal; the driving device includes: an on signal generating unit, an off signal generating unit, wherein: the first input end of the turn-off signal generating unit is coupled with the output end of the error amplifying unit and is suitable for generating a turn-off signal according to the error voltage; and the input end of the turn-on signal generation unit is input with the analog reference control signal and/or the error voltage, and is suitable for generating a turn-on signal under the control of the analog reference control signal and/or the error voltage.
2. The LED control circuit of claim 1, wherein the analog signal conversion unit is adapted to perform an average calculation on the PWM dimming signal to obtain the analog reference control signal.
3. The LED control circuit of claim 1, wherein the driving means further comprises: flip-flop and logic drive unit, wherein:
the first setting end of the trigger is coupled with the output end of the turn-off signal generating unit, and the second setting end of the trigger is coupled with the output end of the turn-on signal generating unit and is suitable for generating a trigger signal according to the turn-off signal and the turn-on signal;
the input end of the logic driving unit is coupled with the output end of the trigger, and is suitable for generating and outputting the driving signal according to the trigger signal.
4. The LED control circuit of claim 1, wherein the analog signal conversion unit includes a first output terminal; the first output end of the analog signal conversion unit is coupled with the first input end of the error amplification unit, and outputs a first analog reference control signal to the first input end of the error amplification unit.
5. The LED control circuit of claim 4, wherein the turn-on signal generating unit has a first input coupled to the output of the error amplifying unit, receives the error voltage, and generates a turn-on signal according to the error voltage;
When the error voltage decreases, the on delay of the on signal generated by the on signal generating unit increases, resulting in an increase in the off time of the driving signal.
6. An LED control circuit as recited in claim 5, further comprising: a current zero-crossing detection unit;
the current zero-crossing detection unit is used for detecting zero crossing of the inductance current and outputting a zero-crossing detection signal to the opening signal generation unit;
under the zero current on mode, the on signal generating unit is controlled by the zero crossing detection signal, and generates the on signal when the zero crossing detection signal is detected and the off time reaches the minimum off time.
7. The LED control circuit of claim 5, wherein the on signal generation unit and the off signal generation unit receive the sampling signal;
in a hysteresis current working mode, the error voltage controls the minimum turn-off time corresponding to the driving signal and the minimum peak voltage of the sampling signal; when the sampling signal is smaller than the minimum peak voltage and the turn-off time is longer than the minimum turn-off time, the turn-on signal generating unit generates the turn-on signal.
8. An LED control circuit as recited in claim 4, further comprising: an oscillator unit;
the input end of the oscillator unit is input with the error voltage and is suitable for generating an oscillation signal and respectively inputting the oscillation signal to the turn-off signal generating unit and the turn-on signal generating unit; the on signal generating unit and the off signal generating unit respectively generate an on signal and an off signal according to the oscillating signal, and the error voltage controls the frequency of the oscillating signal and the duty ratio of the driving signal.
9. The LED control circuit according to claim 4 or 5, wherein the off signal generating unit generates the off signal when the off signal generating unit detects that a peak value of the LED current reaches a peak current controlled by the error voltage in a peak current control mode.
10. The LED control circuit according to claim 4 or 5, wherein the off signal generation unit generates the off signal when the on time is detected to reach the on time controlled by the error voltage in the fixed on time control mode.
11. The LED control circuit of claim 4, wherein the analog signal conversion unit further comprises a second output terminal outputting a second analog reference control signal.
12. The LED control circuit of claim 11, wherein the turn-on signal generating unit has a first input coupled to the second output of the analog signal conversion unit, receives the second analog reference control signal, and generates the turn-on signal based on the second analog reference control signal;
when the second analog reference control signal decreases, the on delay of the on signal generated by the on signal generating unit increases, resulting in an increase in the off time of the driving signal.
13. The LED control circuit of claim 11, wherein the turn-on signal generating unit has a first input coupled to the output of the error amplifying unit for receiving the error voltage; a second input end of the analog signal conversion unit is coupled with a second output end of the analog signal conversion unit, and receives the second analog reference control signal; generating the turn-on signal according to the second analog reference control signal and the error voltage;
when the second analog reference control signal and/or the error voltage is reduced, the turn-on delay of the turn-on signal generated by the turn-on signal generating unit is increased, resulting in an increase in turn-off time of the driving signal.
14. The LED control circuit of any of claims 11-13, further comprising: a current zero-crossing detection unit;
the current zero-crossing detection unit is used for detecting zero crossing of the inductance current and outputting a zero-crossing detection signal to the opening signal generation unit;
under the zero current on mode, the on signal generating unit is controlled by the zero crossing detection signal and the second analog reference control signal, and generates the on signal when the zero crossing detection signal is detected and the off time reaches the minimum off time.
15. The LED control circuit according to any one of claims 11 to 13, wherein the on signal generating unit and the off signal generating unit receive the sampling signal;
in a hysteresis current working mode, the second analog reference control signal and/or the error voltage control the minimum turn-off time corresponding to the driving signal and the minimum peak voltage of the sampling signal; when the sampling signal is smaller than the minimum peak voltage and the turn-off time is longer than the minimum turn-off time, the turn-on signal generating unit generates the turn-on signal.
16. The LED control circuit of claim 11, further comprising: an oscillator unit;
The input end of the oscillator unit is input with the second analog reference control signal and/or the error voltage, and is suitable for generating an oscillation signal and respectively inputting the oscillation signal to the turn-off signal generating unit and the turn-on signal generating unit; the on signal generating unit and the off signal generating unit generate an on signal and an off signal according to the oscillation signal, respectively, and the second analog reference control signal and/or the error voltage control the frequency of the oscillation signal and the duty ratio of the driving signal.
17. The LED control circuit of claim 11, wherein the analog signal conversion unit comprises: the first transconductance amplifying module, the second filter capacitor and the amplifier module, wherein:
the first transconductance amplifying module has a first input end coupled with the input end of the analog signal converting unit, a second input end coupled with the first output end of the amplifier module, and an output end coupled with the input end of the amplifier module and the first end of the second filter capacitor;
the first output end of the amplifier module is coupled with the first output end of the analog signal conversion unit, and the second output end of the amplifier module is coupled with the second output end of the analog signal conversion unit;
And the second end of the second filter capacitor is grounded.
18. The LED control circuit of claim 11, wherein the analog signal conversion unit comprises: the system comprises a second transconductance amplifying module, a third filter capacitor, a pulse generating module, an addition and subtraction counting module and a digital-to-analog conversion module, wherein:
the first input end of the second transconductance amplifying module is coupled with the input end of the analog signal converting unit, the second input end of the second transconductance amplifying module is coupled with the first output end of the digital-to-analog converting module, and the output end of the second transconductance amplifying module is coupled with the input end of the pulse generating module and the first end of the third filter capacitor;
the output end of the pulse generation module is coupled with the input end of the addition and subtraction counting module, and is suitable for generating addition and subtraction pulses and outputting the addition and subtraction pulses to the addition and subtraction counting module when the charge and discharge electric quantity of the third filter capacitor reaches a preset value;
the output end of the addition and subtraction counting module is coupled with the input end of the digital-to-analog conversion module and is suitable for counting the addition and subtraction pulses;
the digital-to-analog conversion module is characterized in that a first output end of the digital-to-analog conversion module is coupled with a first output end of the analog signal conversion unit, and a second output end of the digital-to-analog conversion module is coupled with a second output end of the analog signal conversion unit, and is suitable for converting the count value of the addition-subtraction count module into a corresponding first analog reference control signal and a corresponding second analog reference control signal;
And the second end of the third filter capacitor is grounded.
19. The LED control circuit of claim 1, further comprising: the input end of the clamping and subtracting unit inputs a PWM dimming signal or an analog dimming signal, the PWM dimming signal or the analog dimming signal is subjected to clamping and subtracting operation, and the output end of the clamping and subtracting unit is coupled with the input end of the analog signal converting unit and is suitable for obtaining dimming control voltage and outputting the dimming control voltage to the analog signal converting unit;
and the analog signal conversion unit is used for calculating the dimming control voltage to obtain the analog reference control signal.
20. The LED control circuit of claim 19, wherein the clamping and subtracting unit comprises: operational amplifier module, first resistance, second resistance and switching tube, wherein:
the first end of the first resistor receives a reference voltage, and the second end of the first resistor is coupled with the first end of the second resistor and the first input end of the operational amplification module;
the second input end of the operational amplification module inputs the PWM dimming signal or the analog dimming signal, and the output end of the operational amplification module is coupled with the control end of the switching tube;
the second end of the second resistor is coupled with the first end of the switching tube and the output end of the clamping and subtracting unit;
The second end of the switching tube is grounded.
21. An LED driving device, comprising: the power conversion unit, the power conversion unit includes freewheel diode, inductance, power switch tube and current sampling resistance, LED drive arrangement still includes: the LED control circuit according to any one of claims 1 to 20; wherein:
the driving signal output by the LED control circuit is coupled with the control end of the power switch tube so as to control the power switch tube to be turned on or turned off;
the first end of the current sampling resistor is coupled with the input end of the output current calculation unit and the first end of the power switch tube, the second end of the current sampling resistor is grounded, and the second end of the power switch tube is connected with the inductor.
22. The LED driving device according to claim 21, wherein the power conversion unit is any one of: buck-boost circuitry, flyback circuitry, boost circuitry.
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