CN102281686B - Compensation control device for LED (Light Emitting Diode) lamp during rapid falling of input voltage and method thereof - Google Patents
Compensation control device for LED (Light Emitting Diode) lamp during rapid falling of input voltage and method thereof Download PDFInfo
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Abstract
The invention discloses a compensation control device for an LED (Light Emitting Diode) lamp during the rapid falling of the input voltage and a method thereof. The compensation control device disclosed by the invention comprises a controller, wherein the controller comprises a detection unit, a PWM (Pulse Width Modulation) signal output unit, a storage unit and a central processing unit; the detection unit detects the input voltage and output voltage of a flyback DC (Direct Current)-DC converter; the PWM signal output unit outputs PWM signals to the flyback DC-DC converter; the storage unit stores a starting compensation threshold when the input voltage of the DC-DC converter falls to the input voltage for starting compensation; and the central processing unit controls the duty ratio of the PMW signals. The method disclosed by the invention comprises the following steps: collecting the input voltage and output voltage of the flyback DC-DC converter in real time through the controller; judging that an operating mode of the DC-DC converter is in a continuous current mode and an interrupted current mode or not; and outputting the PMW signals with the corresponding duty ratio to the flyback DC-DC converter according to the judgment result. In the invention, the input voltage of the LED lamp can be rapidly adjusted to a normal value when rapidly falling.
Description
Technical Field
The invention relates to a drive control technology of an LED lamp, in particular to a compensation control device and a compensation control method of the LED lamp when the input voltage drops rapidly.
Background
In the current LED constant current control circuit, when the LED string lights up, the single chip adjusts the input voltage of the LED lamp through the PI algorithm. When the input voltage drops rapidly, the input voltage cannot be adjusted back to a stable value within a short time (less than 1ms) by means of the PI algorithm of the single chip microcomputer, and particularly when the output is dimmed, human eyes can observe the flicker of the brightness of the LED lamp.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a compensation control device and a compensation control method for an LED lamp when the input voltage of the LED lamp drops rapidly, wherein the input voltage of the LED lamp can be rapidly adjusted to a normal value when the input voltage drops rapidly.
The technical scheme adopted by the invention is as follows: a compensation control device of an LED lamp when the input voltage drops rapidly comprises a power supply input circuit and a constant current circuit; the power input circuit comprises a power module and a flyback DC-DC converter which are electrically connected in sequence; the compensation control device is characterized by comprising a controller, wherein the controller comprises: the device comprises a detection unit, a first PWM signal output unit, a storage unit and a central processing unit; wherein:
the detection unit is used for detecting the input voltage and the output voltage of the flyback DC-DC converter and sending the detection result to the central processing unit;
the first PWM signal output unit is used for outputting PWM signals to the flyback DC-DC converter;
the storage unit is used for storing a preset input voltage starting compensation threshold value when the input voltage of the flyback DC-DC converter drops to the input voltage starting compensation threshold value for starting compensation;
the central processing unit is used for comparing the input voltage detection result of the flyback DC-DC converter sent by the detection unit with a preset input voltage starting compensation threshold of the flyback DC-DC converter and judging whether the input voltage of the flyback DC-DC converter is reduced to be lower than the preset input voltage starting compensation threshold of the flyback DC-DC converter or not; and if the voltage drops below the input voltage starting compensation threshold value of the flyback DC-DC converter, judging whether the working state of the flyback DC-DC converter is in a continuous current working mode or an intermittent current working mode, and controlling the first PWM signal output unit to output PWM signals with corresponding duty ratios to the flyback DC-DC converter according to the judgment result.
The invention also discloses a compensation control method of the LED lamp when the input voltage drops rapidly, wherein the LED lamp comprises a power supply input circuit and a constant current circuit; the power input circuit comprises a power module and a flyback DC-DC converter which are electrically connected in sequence; the voltage compensation control method comprises the following steps:
presetting an input voltage starting compensation threshold value for starting compensation when the input voltage of the flyback DC-DC converter falls;
detecting an input voltage and an output voltage of the flyback DC-DC converter;
the controller compares the input voltage detection result of the flyback DC-DC converter with a preset input voltage starting compensation threshold value, and judges whether the input voltage of the flyback DC-DC converter is reduced below the preset input voltage starting compensation threshold value or not;
if the controller judges that the input voltage of the flyback DC-DC converter is reduced to be lower than a preset input voltage starting compensation threshold value, the controller judges whether the working state of the flyback DC-DC converter is in a continuous current working mode or an intermittent current working mode;
and the controller outputs PWM signals with corresponding duty ratios to the flyback DC-DC converter according to the judged current working mode of the flyback DC-DC converter, so that the output voltage of the flyback DC-DC converter is recovered to a normal value.
After the technical scheme is adopted, the input voltage of the DC-DC converter is detected through the controller, and when the situation that the input voltage drops below the input voltage starting compensation threshold value of the DC-DC converter rapidly is detected, the duty ratio of the PWM driving signal of the flyback DC-DC converter is increased immediately to rapidly adjust the output voltage of the flyback DC-DC converter, so that the adjusting time of the LED current is shortened to 400 us-500 us, and the flicker of the LED lamp brightness observed by human eyes is effectively avoided.
Drawings
The specific structure of the present invention is further described by the following embodiments and the accompanying drawings.
Fig. 1 shows a block circuit diagram of an embodiment of the compensation control device of the present invention.
FIG. 2 is a functional block diagram of an embodiment of a central processing unit of the present invention.
Fig. 3 is a schematic block diagram of one embodiment of a constant current circuit of the present invention.
FIG. 4 shows the corrected voltage A and current I according to an embodiment of the present inventionoutGraph of the relationship between.
Fig. 5 is a flowchart of an embodiment of a voltage compensation control method when the input voltage of the LED lamp rapidly drops according to the present invention.
Detailed Description
Fig. 1 is a circuit block diagram of a compensation control device of an LED lamp when an input voltage rapidly drops. The LED lamp comprises a power module 1, a flyback DC-DC converter 2 and a constant current circuit 4. The input end of the flyback DC-DC converter 2 is electrically connected with the output end of the power module 1, and the output end of the flyback DC-DC converter is electrically connected with the positive electrode end of the LED lamp 3 and used for providing voltage required by work for the LED lamp. The output end of the constant current circuit 4 is electrically connected with the cathode end of the LED lamp 3, and is used for supplying a constant current to the LED lamp 3. The compensation control device comprises a controller 5, wherein one output end of the controller 5 is electrically connected with the control end of the flyback DC-DC converter 2, and the other output end of the controller is electrically connected with the input end of the constant current circuit 4 of the LED lamp.
Please continue to refer to fig. 1. The controller 5 described in the present embodiment includes a first PWM signal output unit 51, a second PWM signal output unit 52, a current on-off signal output unit 53, a storage unit 54, a central processing unit 55, and a detection unit 56.
The first PWM signal output unit 51 outputs a PWM signal to the flyback DC-DC converter 2 under the control of the central processing unit 55. The second PWM signal output unit 52 outputs a PWM signal to the constant current circuit 4 of the LED lamp under the control of the central processing unit 55. The current on/off signal output unit 53 outputs a current on signal or a current off signal to the constant current circuit 4 under the control of the central processing unit 55 to control the on/off of the operating current of the LED lamp. The storage unit 54 stores a preset input voltage start compensation threshold value at which the input voltage of the flyback DC-DC converter drops to start compensation. The detection unit 56 is configured to detect and sample the input voltage and the output voltage of the flyback DC-DC converter 2, and send the detection result to the central processing unit 55. The central processing unit 55 compares the detection result of the input voltage of the flyback DC-DC converter sent by the detection unit 56 with a preset compensation threshold for starting the input voltage of the flyback DC-DC converter, and determines whether the input voltage of the flyback DC-DC converter falls below the preset compensation threshold for starting the input voltage of the flyback DC-DC converter; if the voltage drops below the input voltage start compensation threshold of the flyback DC-DC converter, it is determined whether the operating state of the flyback DC-DC converter 2 is in the continuous current operating mode or the discontinuous current operating mode, and the first PWM signal output unit 51 is controlled to output a PWM signal of a corresponding duty ratio to the flyback DC-DC converter 2 according to the determination result.
As shown in fig. 3, the central processing unit 55 further includes a voltage drop determination subunit 551, a converter operation state determination subunit 552, and a duty ratio calculation subunit 553.
The voltage drop determining subunit 551 compares the detection result sent by the detecting unit 56 with the input voltage start compensation threshold of the DC-DC converter stored in the storage unit 54, and sends a converter operating state change signal to the converter operating state determining subunit 552 when the input voltage of the flyback DC-DC converter 2 drops below the input voltage start compensation threshold of the DC-DC converter.
The converter operating state judging subunit 552 respectively calculates after receiving the converter operating state change signal
Sum of sums of
And comparing the calculation results; if it is not
Greater than
If yes, determining that the flyback DC-DC converter 2 is in the continuous current operating mode, otherwise, determining that the flyback DC-DC converter 2 is in the discontinuous current operating mode, and notifying the determination result to the duty ratio calculation subunit 553; wherein f is the operating frequency of the flyback DC-DC converter 2, IoutIs the output current of the flyback DC-DC converter, f and IoutAre all preset by the controller 5. VinStarting a compensation threshold, V, for a predetermined input voltage of the flyback DC-DC converter 2outIs the output voltage of the flyback DC-DC converter 2 when the input voltage thereof is reduced to be below the preset input voltage start compensation threshold value, A is the correction voltage value, A = (23-10 xI)out) /9 wherein Iout0.5A or more and 1.4A or less; i isoutAt 1.4A, A = 1V, IoutAt 0.5A, a = 2V. I isoutBetween 0.5A and 1.4A, according to a linear variation; a and IoutThe relationship between them is shown in FIG. 4; l ispIs the source side excitation inductance of the flyback DC-DC converter 2.
If the flyback DC-DC converter 2 is in the continuous current operation mode, the duty ratio calculation subunit 553 controls the first PWM signal output unit 51 to output a PWM signal with a duty ratio of D1 to the control terminal of the flyback DC-DC converter 2; wherein,; Vinstarting a compensation threshold, V, for a predetermined input voltage of the flyback DC-DC converteroutFor the output voltage of the flyback DC-DC converter when the input voltage thereof is reduced below the preset input voltage starting compensation threshold valueN is the source side turn number N of the transformer of the flyback DC-DC converterpAnd the number of turns of the secondary side NsRatio of N = Ns/Np(ii) a If the flyback DC-DC converter 2 is determined to be in the discontinuous current operating mode, controlling the first PWM signal output unit 51 to output a PWM signal with a duty ratio of D2 to the control end of the flyback DC-DC converter 2; wherein,
; VInAfterDropfor the input voltage V of the flyback DC-DC converter after the input voltage thereof is reduced to below the preset input voltage start compensation thresholdInBeforeDropFor the input voltage of the flyback DC-DC converter before its input voltage drops below a predetermined input voltage start-up compensation threshold, DBeforeDropThe duty cycle of the flyback DC-DC converter 2 is started before its input voltage drops below a predetermined input voltage starting compensation threshold.
Fig. 3 shows a circuit block diagram of the constant current circuit 4 according to one embodiment of the present invention. The constant current circuit 4 includes a filter circuit 41, a comparator 42, a power drive circuit 43, a switch circuit 44, a first current limit circuit 45, a second current limit circuit 46, and a current sampling circuit 47. The input end of the filter circuit 41 is electrically connected to the second PWM signal output unit 52, and the output end is electrically connected to the first input end of the comparator 42; a second input end of the comparator 42 is electrically connected with an output end of the first current limiting circuit 45, an input end of the first current limiting circuit 45 is electrically connected with the current on-off signal output unit 53, an output end of the comparator 42 is electrically connected with an input end of the power driving circuit 43, and an output end of the power driving circuit 43 is electrically connected with an input end of the switching circuit 44; a first output terminal of the switching circuit 44 is electrically connected to the negative terminal of the LED lamp 3, a second output terminal of the switching circuit 44 is electrically connected to an input terminal of a second current limiting circuit 46, an output terminal of the second current limiting circuit 46 is electrically connected to a second input terminal of the comparator 42, and a second output terminal of the switching circuit 44 is further electrically connected to a current sampling circuit 47.
In the embodiment shown in fig. 4, the switching circuit 44 is mainly composed of an NMOS transistor, the power driving circuit 43 is an OTL power amplifying circuit, the comparator 42 is mainly composed of an operational amplifier, and the first current limiting circuit 45, the second current limiting circuit 46 and the current sampling circuit 47 are all composed of a resistor. The NMOS transistor constituting the switching circuit 44 has a drain electrically connected to the negative terminal of the LED lamp 3, a source electrically connected to the inverting terminal of the operational amplifier constituting the comparator 42 through a resistor constituting the second current limiting circuit 46, and a source connected to the ground through a resistor constituting the current sampling circuit 47. The fixed duty ratio signal generated by the second PWM signal output unit 52 generates a stable voltage for determining the current of the constant current circuit through the filter circuit 41 and outputs the voltage to the positive phase terminal of the operational amplifier constituting the comparator 42. The controller 5 controls the switching of the constant current circuit through the current on-off signal output unit 53. When the current on-off signal output unit 53 is set to output a high level, the constant current control circuit is turned off. When the current on/off signal output unit 53 is set to the input state (high resistance state), the constant current circuit is turned on.
In one embodiment, the controller 5 may be formed by a single chip microcomputer.
As shown in fig. 5, the compensation control method of the present invention includes the steps of:
step S1, presetting an input voltage starting compensation threshold value when the input voltage of the flyback DC-DC converter drops to the input voltage starting compensation threshold value for starting the starting compensation;
step S2, detecting the input voltage and the output voltage of the flyback DC-DC converter 2 in real time;
step S3, the controller 5 compares the detection result of the input voltage of the flyback DC-DC converter 2 with the preset input voltage start compensation threshold of the flyback DC-DC converter, and determines whether the input voltage of the flyback DC-DC converter 2 drops below the preset input voltage start compensation threshold of the flyback DC-DC converter;
step S4, if the input voltage of the DC-DC converter 2 drops below the preset input voltage start compensation threshold of the flyback DC-DC converter, the controller 5 determines whether the operating state of the flyback DC-DC converter 2 is in the continuous current operating mode or the discontinuous current operating mode;
in step S4, the controller 5 determines whether the operating state of the flyback DC-DC converter 2 is in the continuous current operating mode or the discontinuous current operating mode, and further includes:
a. a calculation step: the controller 5 calculates separately
Sum of sums of
The product of (a);
wherein f is the operating frequency of the flyback DC-DC converter 2, IoutIs the output current, f and I of the flyback DC-DC converter 2outAre all preset by the controller 5. VinStarting a compensation threshold, V, for a predetermined input voltage of the flyback DC-DC converter 2outIs the output voltage of the flyback DC-DC converter 2 when the input voltage thereof is reduced below the input voltage start compensation threshold value, A is the correction voltage value, A = (23-10 × I)out) /9 wherein Iout0.5A or more and 1.4A or less; i isoutAt 1.4A, A = 1V, IoutAt 0.5A, a = 2V. I isoutBetween 0.5A and 1.4A, according to a linear variation; a and IoutThe relationship between them is shown in FIG. 4; l ispA source side excitation inductor of a transformer of the flyback DC-DC converter 2;
b. a comparison and judgment step: will be provided with
Product of
Is compared if
Greater than
If so, the controller 5 determines that the flyback DC-DC converter 2 is in the continuous current operating mode, otherwise, the controller 5 determines that the flyback DC-DC converter 2 is in the discontinuous current operating mode.
In step S5, the controller 5 outputs a PWM signal with a corresponding duty ratio to the flyback DC-DC converter 2 according to the determination result in step S4.
In step S5, if it is determined that the flyback DC-DC converter 2 is in the continuous current operating mode, the controller 5 outputs a PWM signal with a duty ratio of D1 to the control terminal of the flyback DC-DC converter 2 (i.e., the gate of the source side MOS transistor of the flyback DC-DC converter 2); wherein,
; Vinstarting a compensation threshold, V, for a predetermined input voltage of the flyback DC-DC converter 2outThe output voltage of the flyback DC-DC converter 2 is when the input voltage thereof is reduced to be below the preset input voltage starting compensation threshold, N is the source side turn number N of the transformer of the flyback DC-DC converterpAnd the number of turns of the secondary side NsRatio of N = Ns/Np；
If the flyback DC-DC converter 2 is in the discontinuous current operating mode, the controller 5 outputs a PWM signal with a duty ratio of D2 to the control end of the flyback DC-DC converter; wherein,
; VInAfterDropfor the input voltage V of the flyback DC-DC converter 2 after the input voltage thereof is reduced to below the preset input voltage start compensation thresholdInBeforeDropFor the input voltage of the flyback DC-DC converter before its input voltage drops below a predetermined input voltage start-up compensation threshold, DBeforeDropFor the flyback DC-DC converter 2 to drop its input voltage to a predetermined outputThe input voltage initiates the duty cycle before the compensation threshold.
The foregoing is illustrative only and is not to be construed as limiting the invention. Insubstantial modifications and variations of the present invention can be made by those skilled in the art without departing from the spirit and scope of the invention.
Claims (7)
1. A compensation control device of an LED lamp when the input voltage drops rapidly comprises a power supply input circuit and a constant current circuit; the power input circuit comprises a power module and a flyback DC-DC converter which are electrically connected in sequence; the compensation control device is characterized by comprising a controller, wherein the controller comprises: the device comprises a detection unit, a first PWM signal output unit, a storage unit and a central processing unit; wherein:
the detection unit is used for detecting the input voltage and the output voltage of the flyback DC-DC converter and sending the detection result to the central processing unit;
the first PWM signal output unit is used for outputting PWM signals to the flyback DC-DC converter;
the storage unit is used for storing a preset input voltage starting compensation threshold value when the input voltage of the flyback DC-DC converter drops to the input voltage starting compensation threshold value for starting compensation;
the central processing unit is used for comparing the input voltage detection result of the flyback DC-DC converter sent by the detection unit with a preset input voltage starting compensation threshold of the flyback DC-DC converter and judging whether the input voltage of the flyback DC-DC converter is reduced to be lower than the preset input voltage starting compensation threshold of the flyback DC-DC converter or not; if the voltage drops below the input voltage starting compensation threshold value of the flyback DC-DC converter, judging whether the working state of the flyback DC-DC converter is in a continuous current working mode or an intermittent current working mode, and controlling the first PWM signal output unit to output PWM signals with corresponding duty ratios to the flyback DC-DC converter according to the judgment result; wherein:
if the central processing unit judges that the input voltage of the flyback DC-DC converter falls below the input voltage starting compensation threshold, the central processing unit respectively calculates
Sum of sums of
And comparing the calculation results; if it is not
Greater than
The product of (1) is judged to be in continuous current work of the flyback DC-DC converterMaking a mode, otherwise, judging that the flyback DC-DC converter is in an interrupted current working mode; wherein f is the working frequency of the flyback DC-DC converter, IoutIs the output current, V, of a flyback DC-DC converterinStarting a compensation threshold, V, for a predetermined input voltage of the flyback DC-DC converteroutIs the output voltage of the flyback DC-DC converter when the input voltage of the flyback DC-DC converter falls below an input voltage starting compensation threshold value, A is a correction voltage value, and A = (23-10 × I)out) /9 wherein Iout0.5A or more and 1.4A or less, LpA source side excitation inductor of the flyback DC-DC converter;
if the flyback DC-DC converter is in a continuous current working mode, the central processing unit controls the first PWM signal output unit to output a PWM signal with the duty ratio of D1 to the control end of the flyback DC-DC converter; wherein,
; Vinstarting a compensation threshold, V, for a predetermined input voltage of the flyback DC-DC converteroutThe output voltage of the flyback DC-DC converter is when the input voltage of the flyback DC-DC converter is reduced to be below an input voltage starting compensation threshold value, and n is the ratio of the number of turns of a source side to the number of turns of a secondary side of the flyback DC-DC converter; if the flyback DC-DC converter is judged to be in the discontinuous current working mode, the central processing unit controls the first PWM signal output unit to output a PWM signal with the duty ratio of D2 to the control end of the flyback DC-DC converter; wherein,
; VInAfterDropfor the input voltage V of the flyback DC-DC converter after the input voltage thereof is reduced to below the preset input voltage start compensation thresholdInBeforeDropFor the input voltage of the flyback DC-DC converter before its input voltage drops below a predetermined input voltage start-up compensation threshold, DBeforeDropStarting a compensation threshold for a flyback DC-DC converter when its input voltage drops to a predetermined input voltageThe duty cycle before the bottom.
2. The compensation control device of claim 1, wherein the central processing unit includes a voltage drop judging subunit, a converter operating state judging subunit, and a duty ratio calculating subunit; wherein:
the voltage drop judging subunit is configured to compare the detection result sent by the detection unit with an input voltage start compensation threshold of the DC-DC converter stored in the storage unit, and send a converter operating state change signal to the converter operating state judging subunit when the input voltage of the flyback DC-DC converter drops below the input voltage start compensation threshold of the DC-DC converter;
the working state judgment subunit of the converter respectively calculates after receiving the working state change signal of the converter
Sum of sums ofAnd comparing the calculation results; if it is not
Greater than
If the current is not the positive voltage, judging that the flyback DC-DC converter is in a continuous current working mode, otherwise, judging that the flyback DC-DC converter is in an intermittent current working mode, and informing the duty ratio calculation subunit of a judgment result; wherein f is the working frequency of the flyback DC-DC converter, IoutIs the output current, V, of a flyback DC-DC converterinStarting a compensation threshold, V, for a predetermined input voltage of the flyback DC-DC converteroutStart-up compensation for flyback DC-DC converter when its input voltage drops to input voltageAn output voltage below a threshold value, A is a correction voltage value, A = (23-10 × I)out) /9 wherein Iout0.5A or more and 1.4A or less, LpA source side excitation inductor of the flyback DC-DC converter;
if the flyback DC-DC converter is in a continuous current working mode, the duty ratio calculating subunit controls the first PWM signal output unit to output a PWM signal with the duty ratio of D1 to the control end of the flyback DC-DC converter; wherein,
; Vinstarting a compensation threshold, V, for a predetermined input voltage of the flyback DC-DC converteroutThe output voltage of the flyback DC-DC converter is when the input voltage of the flyback DC-DC converter is reduced to be below an input voltage starting compensation threshold value, and n is the ratio of the number of turns of a source side to the number of turns of a secondary side of the flyback DC-DC converter; if the flyback DC-DC converter is judged to be in the discontinuous current working mode, controlling the first PWM signal output unit to output a PWM signal with the duty ratio of D2 to the control end of the flyback DC-DC converter; wherein,
; VInAfterDropfor the input voltage V of the flyback DC-DC converter after the input voltage thereof is reduced to below the preset input voltage start compensation thresholdInBeforeDropFor the input voltage of the flyback DC-DC converter before its input voltage drops below a predetermined input voltage start-up compensation threshold, DBeforeDropThe duty cycle of the flyback DC-DC converter is started before the input voltage of the flyback DC-DC converter drops below a preset input voltage starting compensation threshold value.
3. The compensation control device of claim 1 or 2, wherein the controller further comprises:
the second PWM signal output unit outputs PWM signals to the constant current circuit under the control of the central processing unit;
and the current on-off signal output unit outputs a current opening signal or a current cutting-off signal to the constant current circuit under the control of the central processing unit so as to control the on-off of the working current of the LED lamp.
4. The compensation control device of claim 3, wherein the constant current circuit includes a filter circuit, a comparator, a power driving circuit, a switching circuit, a first current limiting circuit, a second current limiting circuit, and a current sampling circuit;
the input end of the filter circuit is electrically connected with the second PWM signal output unit, and the output end of the filter circuit is electrically connected with the first input end of the comparator; the second input end of the comparator is electrically connected with the output end of the first current limiting circuit, the input end of the first current limiting circuit is electrically connected with the current on-off signal output unit, the output end of the comparator is electrically connected with the input end of the power driving circuit, and the output end of the power driving circuit is electrically connected with the input end of the switch circuit; the first output end of the switch circuit is electrically connected with the negative end of the LED lamp, the second output end of the switch circuit is electrically connected with the input end of the second current limiting circuit, the output end of the second current limiting circuit is electrically connected with the second input end of the comparator, and the second output end of the switch circuit is also electrically connected with the current sampling circuit.
5. The compensation control device of claim 4, wherein the first current limiting circuit, the second current limiting circuit, and the current sampling circuit are each comprised of a resistor.
6. The compensation control device of claim 5, wherein the controller is comprised of a single chip microcomputer.
7. A compensation control method for an LED lamp when the input voltage drops rapidly is disclosed, wherein the LED lamp comprises a power supply input circuit and a constant current circuit; the power input circuit comprises a power module and a flyback DC-DC converter which are electrically connected in sequence; the voltage compensation control method is characterized by comprising the following steps of:
presetting an input voltage starting compensation threshold value for starting compensation when the input voltage of the flyback DC-DC converter falls;
detecting an input voltage and an output voltage of the flyback DC-DC converter;
the controller compares the input voltage detection result of the flyback DC-DC converter with a preset input voltage starting compensation threshold value, and judges whether the input voltage of the flyback DC-DC converter is reduced below the preset input voltage starting compensation threshold value or not;
if the controller judges that the input voltage of the flyback DC-DC converter is reduced to be lower than a preset input voltage starting compensation threshold value, the controller judges whether the working state of the flyback DC-DC converter is in a continuous current working mode or an intermittent current working mode; the controller judges whether the working state of the flyback DC-DC converter is in a continuous current working mode or an intermittent current working mode, and comprises a calculation step and a comparison and judgment step:
a. a calculation step: the controllers respectively calculate
Sum of sums of
The product of (a); wherein f is the working frequency of the flyback DC-DC converter, IoutIs the output current, V, of a flyback DC-DC converterinStarting a compensation threshold, V, for a predetermined input voltage of the flyback DC-DC converteroutIs the output voltage of the flyback DC-DC converter when the input voltage of the flyback DC-DC converter is below an input voltage starting compensation threshold value, A is a correction voltage value, and A = (23-10 xI)out) /9 wherein Iout0.5A or more and 1.4A or less, LpA source side excitation inductor of the flyback DC-DC converter;
b. a comparison and judgment step: will be provided with
Product of
Is compared if
Greater thanIf so, the controller judges that the flyback DC-DC converter is in a continuous current working mode; otherwise, the controller judges that the flyback DC-DC converter is in an intermittent current working mode;
the controller outputs PWM signals with corresponding duty ratios to the flyback DC-DC converter according to the judged current working mode of the flyback DC-DC converter, so that the output voltage of the flyback DC-DC converter is recovered to a normal value; wherein:
if the flyback DC-DC converter is judged to be in the continuous current working mode, the controller outputs a PWM signal with the duty ratio of D1 to the control end of the flyback DC-DC converter; wherein,
; Vinstarting a compensation threshold, V, for a predetermined input voltage of the flyback DC-DC converteroutThe output voltage of the flyback DC-DC converter is the output voltage when the input voltage of the flyback DC-DC converter reaches below an input voltage starting compensation threshold value, and n is the ratio of the number of turns of a source side to the number of turns of a secondary side of the flyback DC-DC converter;
if the flyback DC-DC converter is judged to be in the discontinuous current working mode, the controller outputs a PWM signal with the duty ratio of D2 to the control end of the flyback DC-DC converter; wherein,
; VInAfterDropis a flyback DC-DC converterInput voltage V after its input voltage drops below a predetermined input voltage start-up compensation thresholdInBeforeDropFor the input voltage of the flyback DC-DC converter before its input voltage drops below a predetermined input voltage start-up compensation threshold, DBeforeDropThe duty cycle of the flyback DC-DC converter is started before the input voltage of the flyback DC-DC converter drops below a preset input voltage starting compensation threshold value.
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| KR100951258B1 (en) * | 2008-06-03 | 2010-04-02 | 삼성전기주식회사 | Driving circuit of light emitting diode |
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| CN101420811A (en) * | 2007-10-25 | 2009-04-29 | 科博达技术有限公司 | Vehicular HID lamp ballast for implementing soft switch PWM technique based on digital control |
| CN101499713A (en) * | 2008-01-31 | 2009-08-05 | 珠海全志科技有限公司 | Mixed switch power source converter and automatic switching control circuit |
| CN101710785A (en) * | 2008-08-30 | 2010-05-19 | 技领半导体(上海)有限公司 | Converter for adjusting output voltage and related method |
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| CN102281686A (en) | 2011-12-14 |
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Address after: 201203 China Zuchongzhi Road (Shanghai) Free Trade Zone No. 2388 building 1-2 Co-patentee after: Zhejiang Keboda Industrial Co., Ltd. Patentee after: Koboda technology, Limited by Share Ltd Address before: 201203 Shanghai City, Pudong New Area Zhangjiang hi tech park Zuchongzhi Road No. 899 Building No. 2 Co-patentee before: Zhejiang Keboda Industrial Co., Ltd. Patentee before: Keboda Technology Corp. |