CN112235903B - Control circuit, control method and LED driving circuit thereof - Google Patents
Control circuit, control method and LED driving circuit thereof Download PDFInfo
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- CN112235903B CN112235903B CN202011178727.0A CN202011178727A CN112235903B CN 112235903 B CN112235903 B CN 112235903B CN 202011178727 A CN202011178727 A CN 202011178727A CN 112235903 B CN112235903 B CN 112235903B
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Abstract
The invention provides a control circuit, a control method and an LED driving circuit thereof, wherein the control circuit comprises a starting judging circuit, a quick starting control circuit, a closed-loop control circuit and a driving signal generating circuit. The start judging circuit is used for outputting a start judging signal according to the detection signal and the preset signal. The quick start control circuit is used for outputting a first control signal to control the output current of the LED drive circuit to be a first output current when the start judging signal is in a first state. The closed loop control circuit is used for outputting a second control signal when the starting judgment signal is in a second state, and the second control signal is used for controlling the output current of the LED drive circuit in the starting stage to be a second output current. The driving signal generating circuit is used for controlling the switching state of the main switching tube according to the first control signal and the second control signal. The control circuit, the control method and the LED driving circuit provided by the invention can realize the rapid starting of the LED driving circuit.
Description
Technical Field
The invention belongs to the field of power electronics, relates to an LED driving technology, and in particular relates to a control circuit, a control method and an LED driving circuit thereof.
Background
The LED lamp is widely applied to the field of illumination due to the characteristics of high brightness, low power consumption, long service life and the like. In the existing dimming LED driving circuit, when the dimming duty ratio is smaller, a long time is required to charge the output voltage to the on voltage of the LED load, which results in a long starting time of the LED driving system when the LED driving system performs the operation of smaller dimming, and the requirements of quick adjustment and response are difficult to meet. The problem is particularly remarkable in dimming and toning applications, and because of the difference of LED lamp pressures or the difference of dimming duty ratios during starting, the starting time of a plurality of strings of LED lamps (comprising two strings) is different, so that the color is disordered, and the time interval between the front lamp and the back lamp is larger. Particularly, in an LED driving system with a high power factor (abbreviated as high PF), the capacitance of the output capacitor is large, the time for charging the output capacitor during starting is long, and the starting is very slow. Therefore, in the high PF LED driving system, the starting time interval of each string of light bars is larger, and the better dimming and toning effects cannot be achieved.
In view of this, it is desirable to provide a new structure or control method for solving the above-mentioned problems when the LED driving circuit is started.
Disclosure of Invention
In order to solve at least part of the problems, the invention provides a control circuit, a control method and an LED driving circuit thereof, so as to effectively solve the problems existing in the starting of the LED driving circuit and realize the rapid starting of the LED driving circuit.
The invention discloses a control circuit for an LED driving circuit, which comprises:
the first input end of the starting judging circuit receives a detection signal representing the output voltage of the LED driving circuit, and the second input end of the starting judging circuit receives a preset signal and is used for outputting a starting judging signal according to the detection signal and the preset signal;
The enabling end of the quick start control circuit is coupled with the output end of the start judging circuit and is used for outputting a first control signal when the start judging signal is in a first state so as to control the output current of the LED driving circuit to be a first output current;
The enabling end of the closed-loop control circuit is coupled with the output end of the starting judging circuit and is used for outputting a second control signal when the starting judging signal is in a second state, the second control signal is used for controlling the output current of the LED driving circuit in the starting stage to be a second output current, and the second control signal is used for controlling the LED driving circuit to realize closed-loop control on the output current when the LED driving circuit is in a closed-loop control stage; the second output current is smaller than the first output current; and
And the first input end of the driving signal generating circuit is coupled with the quick start control circuit, the second input end of the driving signal generating circuit is coupled with the closed loop control circuit, and the output end of the driving signal generating circuit is coupled with the main switching tube in the LED driving circuit and is used for controlling the switching state of the main switching tube according to the first control signal and the second control signal.
In one embodiment of the present invention, a quick start control circuit includes:
a first comparison circuit, a first input end of which receives a first reference signal, a second input end of which receives a sampling signal representing the inductance current, an enabling end of which is coupled with the output end of the starting judgment circuit, and an output end of which outputs a first control signal; the inductance current is a current flowing through an inductance in the LED driving circuit.
In one embodiment of the present invention, a closed loop control circuit includes:
The first input end of the second comparison circuit receives a ramp signal or a sampling signal representing the inductive current, the second input end of the second comparison circuit receives a compensation signal representing the output current, the enabling end of the second comparison circuit is coupled with the output end of the starting judgment circuit, and the output end of the second comparison circuit outputs a second control signal; the inductance current is a current flowing through an inductance in the LED driving circuit.
In an embodiment of the present invention, the detection signal is a degaussing detection signal, and the control circuit further includes:
And the input end of the degaussing detection circuit is coupled with the inductor in the LED driving circuit, and the output end of the degaussing detection circuit is coupled with the input end of the starting judgment circuit and is used for outputting a degaussing detection signal.
In an embodiment of the present invention, the output voltage corresponding to the preset signal is a first voltage, and a ratio of the first voltage to the overvoltage protection voltage of the LED driving circuit ranges from 1/4 to 3/4.
In one embodiment of the present invention, the closed loop control circuit further comprises:
the first input end of the operational amplifier receives the second reference signal, the second input end of the operational amplifier receives a sampling processing signal representing the sampling signal, and the output end of the operational amplifier is coupled with the compensation capacitor to output a compensation signal.
In one embodiment of the present invention, the enable terminal of the operational amplifier is coupled to the output terminal of the start-up determination circuit.
In an embodiment of the present invention, the closed-loop control circuit further includes a sampling signal processing circuit, and the sampling signal processing circuit is configured to output a sampling processing signal according to the sampling signal; the sampling signal processing circuit includes:
a first switch, a first end of which is coupled with the sampling signal end, and a second end of which is coupled with the second input end of the operational amplifier;
a first end of the second switch is coupled with the sampling signal end;
a first end of the third capacitor is coupled with the second end of the second switch, and a second end of the third capacitor is coupled with the reference ground;
A third switch having a first terminal coupled to the first terminal of the third capacitor;
A fourth capacitor, a first end of which is coupled to the second end of the third switch, and a second end of which is coupled to the reference ground;
A fourth switch, a first end of which is coupled to the first end of the fourth capacitor, and a second end of which is coupled to the second input end of the operational amplifier;
a fifth switch having a first end coupled to the first end of the fourth capacitor and a second end coupled to the reference ground; and
And the first end of the sixth switch is coupled with the sampling signal end, and the second end of the sixth switch is coupled with the second input end of the operational amplifier.
In an embodiment of the invention, the control circuit further includes a main switching tube, and a control end of the main switching tube is coupled to the driving signal generating circuit.
The invention also discloses an LED driving circuit, which comprises a rectifying circuit, an input capacitor, an output capacitor, an inductor and the control circuit.
The invention also discloses a control method for the LED drive circuit, which comprises the following steps:
Outputting a start judging signal according to a preset signal and a detection signal representing the output voltage of the LED driving circuit;
Selecting a starting mode of the LED driving circuit according to the starting judging signal; when the starting judgment signal is in a first state, a quick starting control mode is selected, and a first control signal is output to control the output current of the LED drive circuit to be a first output current; when the starting judgment signal is in a second state, a closed-loop control mode is selected, and a second control signal is output to control the output current of the LED drive circuit in a starting stage to be a second output current; the second output current is smaller than the first output current; and
And controlling the switching state of a main switching tube in the LED driving circuit according to the first control signal and the second control signal.
In one embodiment of the present invention, the fast start control method specifically includes:
The first reference signal is compared with a sampling signal representing the inductor current, and a first control signal is output according to the comparison result.
In one embodiment of the present invention, the closed-loop control method specifically includes:
Comparing the sampling signal representing the inductance current with the compensation signal representing the output current, and outputting a second control signal according to the comparison result; or comparing the ramp signal with a compensation signal representing the output current and outputting a second control signal according to the comparison result.
In an embodiment of the present invention, the output voltage corresponding to the preset signal is a first voltage, and a ratio of the first voltage to the overvoltage protection voltage of the LED driving circuit ranges from 1/4 to 3/4.
The invention provides a control circuit, a control method and an LED driving circuit for an LED driving circuit, wherein the control circuit comprises a starting judgment control circuit, a quick starting control circuit, a closed-loop control circuit and a driving signal generation circuit. And outputting a start judging signal by comparing the preset signal with a detection signal representing the output voltage of the LED driving circuit. The method is characterized in that the current output voltage is compared with the preset voltage, if the current output voltage is smaller than the preset voltage, the quick start control circuit is controlled to work, and the output capacitor is charged with larger current; and if the current output voltage is greater than the preset voltage, controlling the closed-loop control circuit to work, charging the output capacitor with smaller current, and enabling the LED driving circuit to reach the preset output voltage and/or output current slowly through closed-loop control. The control circuit, the control method and the LED driving circuit provided by the invention can realize the rapid starting of the LED driving circuit. Meanwhile, in the LED driving circuit of the multi-string LED lamps, the starting time interval between the strings of LED lamps is smaller, and the dimming and toning performance of the LED driving circuit is better.
Drawings
Fig. 1 shows a schematic circuit configuration of an LED driving circuit according to an embodiment of the present invention.
Fig. 2 shows a schematic circuit configuration of a control circuit according to an embodiment of the present invention.
Fig. 3 is a schematic diagram showing a partial circuit configuration of a control circuit according to an embodiment of the present invention.
Fig. 4 shows a partial signal waveform diagram of an LED driving circuit according to an embodiment of the present invention.
Fig. 5 shows a schematic circuit configuration of a control circuit according to another embodiment of the present invention.
Fig. 6 shows a partial signal waveform diagram of an LED driving circuit according to another embodiment of the present invention.
Fig. 7 shows a schematic diagram of steps of a control method for an LED driving 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 present invention, preferred embodiments of the invention are described below in conjunction with the examples, but it should be understood that these descriptions are merely intended to illustrate further features and advantages of the invention, and are not limiting of the claims of the invention.
The description of this section is intended to be illustrative of only a few exemplary embodiments and the invention is not to be limited in scope by the description of the embodiments. It is also within the scope of the description and claims of the invention to interchange some of the technical features of the embodiments with other technical features of the same or similar prior art.
"Coupled" or "connected" in the specification includes both direct and indirect connections. An indirect connection is a connection made through an intermediary, such as 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 through circuits or components such as switches, follower circuits, and the like, that accomplish the same or similar functional objectives.
An embodiment of the invention discloses a control circuit for an LED driving circuit, which comprises a starting judging circuit, a quick starting control circuit, a closed-loop control circuit and a driving signal generating circuit. The first input end of the starting judging circuit is coupled with the detection signal end, the detection signal end is used for outputting a detection signal representing the output voltage of the LED driving circuit, the second input end of the starting judging circuit is coupled with the preset signal end, the preset signal end is used for outputting a preset signal, and the starting judging circuit is used for outputting a starting judging signal according to the detection signal and the preset signal. The enabling end of the quick start control circuit is coupled with the output end of the start judging circuit, and the quick start control circuit is used for outputting a first control signal to control the output current of the LED driving circuit to be a first output current when the start judging signal is in a first state. The enabling end of the closed loop control circuit is coupled with the output end of the starting judging circuit, the closed loop control circuit is used for outputting a second control signal when the starting judging signal is in a second state, and the second control signal is used for controlling the output current of the LED driving circuit in a starting stage to be a second output current. The second control signal can also be used for controlling the LED driving circuit to realize closed-loop control of the output current when the LED driving circuit is in a closed-loop control stage. Wherein the second output current is less than the first output current. The first input end of the driving signal generating circuit is coupled with the output end of the quick start control circuit, the second input end of the driving signal generating circuit is coupled with the output end of the closed loop control circuit, the output end of the driving signal generating circuit is coupled with the control end of the main switching tube in the LED driving circuit, and the driving signal generating circuit controls the switching state of the main switching tube according to the first control signal and the second control signal.
In one embodiment of the present invention, the operation of the LED driving circuit includes a start-up phase and a closed loop control phase. When the LED driving circuit starts to work, the LED driving circuit enters a starting stage. When the start-up phase is completed, the LED drive circuit enters a closed loop control phase. In another embodiment of the present invention, the start-up phase includes a fast start-up procedure and a part of a closed-loop control procedure, that is, the start-up phase includes a control procedure performed by the fast start-up control circuit and the closed-loop control circuit, so as to complete the start-up control of the LED driving circuit. When the starting stage of the LED driving circuit is finished, the LED driving circuit enters a closed-loop control stage, and the closed-loop control circuit is also used for performing closed-loop control on the output current.
In another embodiment of the present invention, the detection signal is a degaussing detection signal, and the degaussing detection signal is obtained by detecting a degaussing time of an inductor in the LED driving circuit. The preset signal is a preset degaussing time signal, and the starting judgment circuit outputs a starting judgment signal by comparing the degaussing detection signal with the preset degaussing time signal. When the degaussing detection signal is greater than the preset degaussing time signal, the output start judging signal is in a first state (such as a high level), and the quick start control circuit is controlled to work. When the degaussing detection signal is smaller than the preset degaussing time signal, the output start judging signal is in a second state (such as low level), and the closed-loop control circuit is controlled to work.
In an embodiment of the present invention, the detection signal is an output voltage of the LED driving circuit, and the output voltage value may be obtained through detection or calculation and conversion. As can be seen from the calculation formula tdem=lm×ics_pk/vo=lm×vcs_pk/(rcs×vo) of the degaussing time, when the sampling voltage vcs_pk and the degaussing time Tdem are known, the output voltage Vo of the current switching period can be obtained. Wherein Tdem is the degaussing time of the inductor in the LED driving circuit, lm is the inductance of the inductor, ics_pk is the peak current flowing through the sampling resistor, vcs_pk is the sampling voltage corresponding to the peak current flowing through the sampling resistor, rcs is the resistance value of the sampling resistor, and Vo is the output voltage of the LED driving circuit. The preset signal is a preset reference voltage, and the start judging circuit outputs a start judging signal by comparing the output voltage with the preset reference voltage. When the output voltage is smaller than the preset reference voltage, the output start judging signal is in a first state (such as a high level), and the quick start control circuit is controlled to work. When the output voltage is smaller than the preset reference voltage, the output capacitor is charged by adopting larger current, so that the output voltage is quickly lifted, and the starting time of the LED driving circuit can be effectively shortened. When the output voltage is greater than the preset reference voltage, the output start judging signal is in a second state (such as a low level), and the closed-loop control circuit is controlled to work. When the output voltage is larger than the preset reference voltage, the output capacitor is charged with smaller current in a closed-loop control mode, and the LED driving circuit is enabled to reach preset output voltage and/or output current slowly through closed-loop control, so that closed-loop control of the output voltage and/or the output current of the LED driving circuit is achieved, and the dimming performance requirement of the LED driving circuit is effectively met.
In an embodiment of the present invention, the output voltage corresponding to the preset signal is a first voltage, that is, when the LED driving circuit stably outputs the preset signal value, the output voltage of the LED driving circuit is the first voltage, and the ratio of the first voltage to the overvoltage protection voltage of the LED driving circuit ranges from 1/4 to 3/4. In another embodiment of the present invention, the first voltage value may be selected according to an overvoltage protection voltage.
An embodiment of the invention discloses a BUCK type LED driving circuit, which comprises a rectifying circuit, an input capacitor C1, a first diode D1, an output capacitor C2, an inductor L1, an LED load and a control circuit, as shown in FIG. 1. The input voltage is rectified by the rectifying circuit to obtain direct-current voltage, the first end of the input capacitor C1 is coupled with the rectifying circuit, and the second end of the input capacitor C1 is coupled with the reference ground. The cathode of the first diode D1 is coupled to the first end of the input capacitor C1. The first end of the output capacitor C2 is coupled to the first end of the input capacitor C1, and the LED load is connected in parallel to the output capacitor C2. The first end of the inductor L1 is coupled to the anode end of the first diode D1, and the second end of the inductor L1 is coupled to the second end of the output capacitor C2. In an embodiment of the present invention, a high voltage supply terminal HVDD of the control circuit receives a bus voltage, the control circuit includes a main switching tube, and a DRAIN terminal DRAIN of the control circuit is coupled to a first terminal of the inductor L1 and a DRAIN of the main switching tube, respectively. In an embodiment of the invention, a sampling end CS of the control circuit is coupled to the sampling resistor Rcs, a dimming signal end DIM receives a PWM dimming signal, the PWM dimming signal is used for performing dimming control on the LED driving circuit, and a ground end GND of the control circuit is coupled to the reference ground. In another embodiment of the present invention, the control circuit further includes an overvoltage protection detection terminal coupled to the first resistor R1.
In one embodiment of the present invention, as shown in fig. 2, the control circuit for the LED driving circuit includes a start-up judging circuit 110, a fast start-up control circuit 120, a closed-loop control circuit 130, and a driving signal generating circuit 140. The first input terminal of the start-up judging circuit 110 receives the degaussing detection signal Tdem, the second input terminal of the start-up judging circuit 110 receives the preset degaussing time signal tdem_ref, and the start-up judging circuit 110 outputs the start-up judging signal qs_en according to the degaussing detection signal Tdem and the preset degaussing time signal tdem_ref. When the degaussing detection signal Tdem is greater than the preset degaussing time signal tdem_ref, the start-up determination circuit 110 outputs the start-up determination signal qs_en to a high level. When the degaussing detection signal Tdem is smaller than the preset degaussing time signal tdem_ref, the start-up determination circuit 110 outputs the start-up determination signal qs_en to a low level.
As shown in fig. 2, the enable terminal of the fast start control circuit 120 is coupled to the output terminal of the start-up determination circuit 110. The enable end of the closed-loop control circuit 130 is coupled to the output end of the start-up judging circuit 110, and an inverter is further coupled between the closed-loop control circuit 130 and the start-up judging circuit 110. When the start-up determination signal qs_en is at a high level, the control circuit controls the fast start-up control circuit 120 to operate, and the fast start-up control circuit 120 outputs a first control signal to control the output current of the LED driving circuit to be a first output current. When the start-up judging signal qs_en is at a low level, the control circuit controls the closed-loop control circuit 130 to operate, and the closed-loop control circuit 130 outputs a second control signal to control the output current of the LED driving circuit in the start-up stage to be the second output current. Wherein the second output current is less than the first output current. The first input end of the driving signal generating circuit 140 is coupled to the output end of the fast start control circuit 120, the second input end of the driving signal generating circuit 140 is coupled to the output end of the closed loop control circuit 130, the output end of the driving signal generating circuit 140 is coupled to the control end of the main switching tube in the LED driving circuit, and the driving signal generating circuit 140 controls the switching state of the main switching tube according to the first control signal and the second control signal. The starting stage of the LED driving circuit is divided into a quick starting control stage and a closed-loop control stage, and different charging control is carried out on the output capacitor in different stages, so that the quick starting of the LED driving circuit is realized, and the closed-loop control of the output voltage and/or the output current of the LED driving circuit is ensured.
In one embodiment of the present invention, as shown in fig. 2, the fast start control circuit 120 includes a first comparison circuit. In a specific embodiment, the first comparator circuit is a first comparator 121, the non-inverting input terminal of the first comparator 121 receives the first reference voltage Vref1, and the inverting input terminal of the first comparator 121 receives a sampling signal representing an inductance current, which is a current flowing through an inductance in the LED driving circuit. In a specific embodiment, the sampling signal is a sampling voltage Vcs corresponding to a peak current flowing through the sampling resistor. The enable end of the first comparator 121 is coupled to the output end of the start-up judging circuit 110, and the first comparator 121 outputs a comparison result signal as a first control signal according to the first reference voltage Vref1 and the sampling voltage Vcs.
In another embodiment of the present invention, as shown in fig. 2, the closed loop control circuit 130 includes a second comparison circuit. In a specific embodiment, the second comparing circuit is a second comparator 132, an inverting input terminal of the second comparator 132 receives the sampling voltage Vcs, and a non-inverting input terminal of the second comparator 132 receives the compensation voltage Vcomp that characterizes the average current flowing through the inductor. The enable end of the second comparator 132 is coupled to the output end of the start-up determining circuit 110, and an inverter is further coupled between the second comparator 132 and the start-up determining circuit 110. The second comparator 132 outputs a comparison result as a second control signal according to the sampling voltage Vcs and the compensation voltage Vcomp.
In an embodiment of the present invention, the closed loop control circuit 130 further includes an operational amplifier 131. The non-inverting input terminal of the operational amplifier 131 receives the second reference voltage Vref2, the inverting input terminal of the operational amplifier 131 receives the sampling signal V1 representing the sampling signal, and the output terminal of the operational amplifier 131 is coupled to the compensation capacitor to output the compensation voltage Vcomp. In another embodiment of the present invention, the enable terminal of the operational amplifier 131 is coupled to the output terminal of the start-up determining circuit 110. An inverter is further coupled between the operational amplifier 131 and the start-up determination circuit 110.
In an embodiment of the present invention, the detection signal is a degaussing detection signal, the control circuit further includes a degaussing detection circuit 150, an input terminal of the degaussing detection circuit 150 is coupled to an inductor in the LED driving circuit, an output terminal of the degaussing detection circuit 150 is coupled to an input terminal of the start-up determining circuit 110, and the degaussing detection circuit 150 is configured to output a degaussing detection signal Tdem according to a degaussing time of the inductor.
In an embodiment of the present invention, as shown in fig. 3, the closed-loop control circuit further includes a sampling signal processing circuit 133, and the sampling signal processing circuit 133 is configured to output a sampling processing signal V1 according to the sampling voltage Vcs. The sampling signal processing circuit 133 includes a first switch S1, a second switch S2, a third switch S3, a fourth switch S4, a fifth switch S5, a sixth switch S6, a third capacitor C3, and a fourth capacitor C4. The first terminal of the first switch S1 is coupled to the sampling signal terminal Vcs, and the second terminal of the first switch S1 is coupled to the inverting input terminal of the operational amplifier 131. The first terminal of the second switch S2 is coupled to the sampling signal terminal Vcs. The first end of the third capacitor C3 is coupled to the second end of the second switch S2, and the second end of the third capacitor C3 is coupled to the reference ground. The first terminal of the third switch S3 is coupled to the first terminal of the third capacitor C3. The first end of the fourth capacitor C4 is coupled to the second end of the third switch S3, and the second end of the fourth capacitor C4 is coupled to the reference ground. The first terminal of the fourth switch S4 is coupled to the first terminal of the fourth capacitor C4, and the second terminal of the fourth switch S4 is coupled to the second input terminal of the operational amplifier 131. The first terminal of the fifth switch S5 is coupled to the first terminal of the fourth capacitor C4, and the second terminal of the fifth switch S5 is coupled to the reference ground. The first terminal of the sixth switch S6 is coupled to the sampling signal terminal Vcs, and the second terminal of the sixth switch S6 is coupled to the second input terminal of the operational amplifier 131.
In one embodiment of the present invention, the switching cycle of the main switching tube is divided into a magnetizing stage, a demagnetizing stage and a dead zone stage. The sampling signal processing circuit 133 operates as follows: when the PWM control signal of the main switching tube is PWM on, in this case, in the magnetizing stage of the inductor, the first switch S1, the second switch S2 and the fifth switch S5 are controlled to be turned on, and the sampling processing signal V1 is consistent with the Vcs voltage. When the PWM control signal of the main switching tube is PWM off, the demagnetizing stage is first entered, the third switch S3 and the fourth switch S4 are controlled to be turned on, and the sampling processing signal V1 is half of the average current of the inductor. And when the demagnetization is finished, entering a dead zone stage, and controlling the sixth switch to be conducted, wherein the sampling processing signal V1 is zero.
In one embodiment of the present invention, a control circuit as shown in FIG. 2 may be used for a low PF LED driver circuit. As shown in fig. 4, when the output voltage Vo of the LED driving circuit is lower than the preset reference voltage, the control circuit controls the fast start control circuit to work, charges the output capacitor with a larger current, and the corresponding current IL flowing through the inductor is a larger current value. When the output voltage Vo is higher than a preset reference voltage, the control circuit controls the closed-loop control circuit to work, the control circuit charges the output capacitor with smaller current so as to realize closed-loop control on the output voltage and the output current, and the LED driving circuit is a current peak control type driving circuit. When the output voltage and the output current reach the preset value of the LED driving circuit, the LED driving system reaches a normal working state, and the compensation voltage Vcomp is stabilized at a certain value.
In one embodiment of the present invention, a control circuit as shown in FIG. 5 may be used for the high PF LED driver circuit. The control circuit includes a start-up determination circuit 210, a fast start-up control circuit 220, a closed loop control circuit 230, and a drive signal generation circuit 240. The fast start control circuit 220 includes a first comparator 221. The closed loop control circuit 230 includes a second comparator 232, an inverting input of the second comparator 232 receiving a ramp signal Vramp, and a non-inverting input of the second comparator 132 receiving a compensation voltage Vcomp that characterizes an average current flowing through the inductor. The second comparator 232 outputs a comparison result according to the ramp signal Vramp and the compensation voltage Vcomp as a second control signal. In one embodiment of the present invention, the closed loop control circuit 230 further includes an operational amplifier 231. As shown in fig. 6, when the output voltage Vo of the LED driving circuit is lower than the preset reference voltage, the control circuit controls the fast start control circuit to work, charges the output capacitor with a larger current, and the corresponding current IL flowing through the inductor is a larger current value. When the output voltage Vo is higher than the preset reference voltage, the control circuit controls the closed-loop control circuit to work, the control circuit charges the output capacitor with smaller current, the second comparator 232 outputs a comparison result according to the ramp signal Vramp and the compensation voltage Vcomp, and the LED driving circuit is a switching time control type driving circuit, so that the waveform of the inductance current IL is a sawtooth waveform with a steamed bread waveform.
As shown in fig. 7, an embodiment of the present invention discloses a control method for an LED driving circuit, the control method comprising the steps of:
S100, outputting a start judging signal according to a preset signal and a detection signal representing the output voltage of the LED driving circuit;
S200, selecting a starting mode of the LED driving circuit according to a starting judgment signal; when the starting judgment signal is in a first state, a quick starting control mode is selected, and a first control signal is output to control the output current of the LED drive circuit to be a first output current; when the starting judgment signal is in a second state, a closed-loop control mode is selected, and a second control signal is output to control the output current of the LED drive circuit in a starting stage to be a second output current; the second output current is smaller than the first output current; and
S300, controlling the switching state of a main switching tube in the LED driving circuit according to the first control signal and the second control signal.
In an embodiment of the present invention, the fast start control method specifically includes: the first reference signal is compared with a sampling signal representing the inductor current, and a first control signal is output according to the comparison result.
In one embodiment of the present invention, the closed-loop control method specifically includes: comparing the sampling signal representing the inductance current with the compensation signal representing the output current, and outputting a second control signal according to the comparison result; or comparing the ramp signal with a compensation signal representing the output current and outputting a second control signal according to the comparison result.
In an embodiment of the invention, the detection signal is a degaussing detection signal.
In an embodiment of the present invention, the output voltage corresponding to the preset signal is a first voltage, and the ratio of the first voltage to the overvoltage protection voltage of the LED driving circuit ranges from 1/4 to 3/4.
The invention provides a control circuit, a control method and an LED driving circuit for an LED driving circuit, wherein the control circuit comprises a starting judgment control circuit, a quick starting control circuit, a closed-loop control circuit and a driving signal generation circuit. And outputting a start judging signal by comparing the preset signal with a detection signal representing the output voltage of the LED driving circuit. The method is characterized in that the current output voltage is compared with the preset voltage, if the current output voltage is smaller than the preset voltage, the quick start control circuit is controlled to work, and the output capacitor is charged with larger current; and if the current output voltage is greater than the preset voltage, controlling the closed-loop control circuit to work, charging the output capacitor with smaller current, and enabling the LED driving circuit to reach the preset output voltage and/or output current slowly through closed-loop control. The control circuit, the control method and the LED driving circuit provided by the invention can realize the rapid starting of the LED driving circuit. Meanwhile, in the LED driving circuit of the multi-string LED lamps, the starting time interval between the strings of LED lamps is smaller, and the dimming and toning performance of the LED driving circuit is better.
The description and applications of the present invention herein above are illustrative and are not intended to limit the scope of the invention to the embodiments described above. The relevant descriptions of effects or advantages and the like related to the embodiments may not be embodied in experimental examples due to uncertainty of specific condition parameters, and are not intended to limit the embodiments. Variations and modifications of the embodiments disclosed herein are possible, and alternatives and equivalents of the various components of the embodiments are known to those of ordinary skill 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 assemblies, materials, and components, 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 (11)
1. A control circuit for an LED driving circuit, the control circuit comprising:
the first input end of the starting judging circuit receives a detection signal representing the output voltage of the LED driving circuit, and the second input end of the starting judging circuit receives a preset signal and is used for outputting a starting judging signal according to the detection signal and the preset signal;
The enabling end of the quick start control circuit is coupled with the output end of the start judging circuit and is used for outputting a first control signal when the start judging signal is in a first state so as to control the output current of the LED driving circuit to be a first output current;
The enabling end of the closed-loop control circuit is coupled with the output end of the starting judging circuit and is used for outputting a second control signal when the starting judging signal is in a second state, the second control signal is used for controlling the output current of the LED driving circuit in a starting stage to be a second output current, and the second control signal is used for controlling the LED driving circuit to realize closed-loop control on the output current when the LED driving circuit is in a closed-loop control stage; the second output current is smaller than the first output current; and
The first input end of the driving signal generating circuit is coupled with the quick start control circuit, the second input end of the driving signal generating circuit is coupled with the closed loop control circuit, and the output end of the driving signal generating circuit is coupled with a main switching tube in the LED driving circuit and used for controlling the switching state of the main switching tube according to the first control signal and the second control signal; wherein the closed loop control circuit includes:
The first input end of the second comparison circuit receives a ramp signal or a sampling signal representing the inductive current, the second input end of the second comparison circuit receives a compensation signal representing the output current, the enabling end of the second comparison circuit is coupled with the output end of the starting judgment circuit, and the output end of the second comparison circuit outputs a second control signal; the inductance current is the current flowing through the inductance in the LED driving circuit;
The first input end of the operational amplifier receives a second reference signal, the second input end of the operational amplifier receives a sampling processing signal representing a sampling signal, and the output end of the operational amplifier is coupled with the compensation capacitor to output a compensation signal; and
A sampling signal processing circuit for outputting a sampling processing signal according to the sampling signal; the sampling signal processing circuit includes:
a first switch, a first end of which is coupled with the sampling signal end, and a second end of which is coupled with the second input end of the operational amplifier;
a first end of the second switch is coupled with the sampling signal end;
a first end of the third capacitor is coupled with the second end of the second switch, and a second end of the third capacitor is coupled with the reference ground;
A third switch having a first terminal coupled to the first terminal of the third capacitor;
A fourth capacitor, a first end of which is coupled to the second end of the third switch, and a second end of which is coupled to the reference ground;
A fourth switch, a first end of which is coupled to the first end of the fourth capacitor, and a second end of which is coupled to the second input end of the operational amplifier;
a fifth switch having a first end coupled to the first end of the fourth capacitor and a second end coupled to the reference ground; and
And the first end of the sixth switch is coupled with the sampling signal end, and the second end of the sixth switch is coupled with the second input end of the operational amplifier.
2. The control circuit of claim 1, wherein the fast start control circuit comprises:
a first comparison circuit, a first input end of which receives a first reference signal, a second input end of which receives a sampling signal representing the inductance current, an enabling end of which is coupled with the output end of the starting judgment circuit, and an output end of which outputs a first control signal; the inductance current is a current flowing through an inductance in the LED driving circuit.
3. The control circuit of claim 1, wherein the detection signal is a degaussing detection signal, the control circuit further comprising:
And the input end of the degaussing detection circuit is coupled with the inductor in the LED driving circuit, and the output end of the degaussing detection circuit is coupled with the input end of the starting judgment circuit and is used for outputting a degaussing detection signal.
4. The control circuit of claim 1, wherein the output voltage corresponding to the preset signal is a first voltage, and a ratio of the first voltage to the overvoltage protection voltage of the LED driving circuit ranges from 1/4 to 3/4.
5. The control circuit of claim 1, wherein an enable terminal of the operational amplifier is coupled to an output terminal of the start-up determination circuit.
6. The control circuit of claim 1, further comprising a main switching tube, wherein a control terminal of the main switching tube is coupled to the driving signal generating circuit.
7. An LED driving circuit, characterized in that the LED driving circuit comprises a rectifying circuit, an input capacitance, an output capacitance, an inductance and a control circuit according to any one of claims 1-6.
8. A control method for the LED driving circuit according to claim 7, characterized in that the control method comprises: outputting a start judging signal according to a preset signal and a detection signal representing the output voltage of the LED driving circuit;
Selecting a starting mode of the LED driving circuit according to the starting judging signal; when the starting judgment signal is in a first state, a quick starting control mode is selected, and a first control signal is output to control the output current of the LED drive circuit to be a first output current; when the starting judgment signal is in a second state, a closed-loop control mode is selected, and a second control signal is output to control the output current of the LED drive circuit in a starting stage to be a second output current; the second output current is smaller than the first output current; and
And controlling the switching state of a main switching tube in the LED driving circuit according to the first control signal and the second control signal.
9. The control method according to claim 8, wherein the quick start control mode specifically includes:
The first reference signal is compared with a sampling signal representing the inductor current, and a first control signal is output according to the comparison result.
10. The control method according to claim 8, wherein the closed-loop control mode specifically includes:
Comparing the sampling signal representing the inductance current with the compensation signal representing the output current, and outputting a second control signal according to the comparison result; or comparing the ramp signal with a compensation signal representing the output current and outputting a second control signal according to the comparison result.
11. The control method of claim 8, wherein the output voltage corresponding to the preset signal is a first voltage, and a ratio of the first voltage to the overvoltage protection voltage of the LED driving circuit ranges from 1/4 to 3/4.
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| CN113423156A (en) * | 2021-06-19 | 2021-09-21 | 浙江榆阳电子有限公司 | Low-dimming-rate quick start circuit of LED dimming power supply and start method thereof |
| CN113473671B (en) * | 2021-07-28 | 2022-09-23 | 上海晶丰明源半导体股份有限公司 | Control circuit for constant current type drive circuit and constant current type drive circuit |
| CN114143931B (en) * | 2021-12-16 | 2023-12-08 | 上海南麟集成电路有限公司 | LED driving circuit |
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