CN106131999B - Constant current output circuit and method of LED driving power supply - Google Patents
Constant current output circuit and method of LED driving power supply Download PDFInfo
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- CN106131999B CN106131999B CN201610487006.5A CN201610487006A CN106131999B CN 106131999 B CN106131999 B CN 106131999B CN 201610487006 A CN201610487006 A CN 201610487006A CN 106131999 B CN106131999 B CN 106131999B
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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
- H05B45/37—Converter circuits
Abstract
The invention detects the peak voltage formed by the inductive current on the external precise resistor through the envelope detection technology, compares the peak voltage with a precise reference voltage generated inside to obtain a control voltage, and then utilizes the control voltage to generate a threshold voltage which is inversely changed along with the external inductive current, thereby forcing the inductive current to inversely change, and achieving the purpose of outputting constant current by the LED driving power supply. Compared with the conventional open-loop control, the method has the following advantages in three aspects: 1, insensitivity to input voltage fluctuation (open loop control, failure of feedback and system delay); 2, the method is insensitive to inductance value deviation of mass production (the output current is controlled by an open loop to change along with the inductance value); 3, it is insensitive to LED load voltage variation (open loop control varies with load voltage).
Description
Technical Field
The invention relates to the field of integrated circuit design, in particular to a constant current output circuit of an LED driving power supply.
Background
LED power supplies are one type of power supply, and are devices that provide power to an electronic device, also known as power supplies, deployed such that different power inputs on the device are connected to separate circuit devices with two or three power inputs. (light emitting diode) dry cells and the like are also called power sources; a device that converts ac power to dc power through a transformer and a rectifier is called a rectified power supply. The electronic device that can provide the signal is called the signal source. The transistor can amplify the signal from the front and transmit the amplified signal to the back circuit. The transistor can also be considered as a signal source for the following circuits. Rectified power, the source of the signal, is sometimes also called the power supply.
Devices that convert other forms of energy into electrical energy are called power sources. The generator can convert mechanical energy into electric energy, and the dry battery can convert chemical energy into electric energy. The battery is not electrified, the two poles of the battery are respectively provided with positive and negative charges, voltage is generated by the positive and negative charges (current is formed by directional movement of the charges under the action of the voltage), and the charge conductor is originally provided with the voltage only by adding the voltage to generate the current. When two poles of the battery are connected with a conductor, the battery discharges electric charges for generating current, and when the electric charges are dissipated, the dry battery is called as a power supply; a device that converts ac power to dc power through a transformer and a rectifier is called a rectified power supply. The electronic device that can provide the signal is called a signal source. The LED power supply is a constant current source, and the general switching power supply is a constant voltage source.
However, the constant current output of the current LED power supply generally fluctuates, and for example, input voltage instability, load variation, inductance value deviation and the like all bring fluctuation of the output of the LED power supply, so that the existing LED power supply belongs to open-loop output, and therefore, real constant current output is difficult to realize.
Disclosure of Invention
In view of the above, a first object of the present invention is to provide a monitoring circuit for achieving constant current output of an LED power supply through closed loop feedback.
The second purpose of the invention is to provide a constant current output method.
The first purpose of the invention is realized by the following technical scheme: a constant current output circuit of an LED driving power supply comprises a sampling feedback multiplexing module, wherein the sampling feedback multiplexing module comprises an energy storage unit, a switch unit and a sampling resistor which are sequentially connected in series, the energy storage unit is coupled with the high level of the LED power supply, one end of the sampling resistor is grounded, and the other end of the sampling resistor outputs sampling voltage; the amplifying module is coupled with the sampling voltage and outputs an amplifying voltage following the sampling voltage; the detection module is coupled with the amplified voltage and outputs a modulation voltage within a preset amplitude range; the differential filtering module is coupled with the modulation voltage and outputs a control voltage according to a preset reference voltage; the reversing voltage regulating module is controlled by the control voltage and outputs a reference voltage of a reverse amplification control voltage; the judging module comprises a comparing unit, the comparing unit is used for comparing the reference voltage with the sampling voltage, when the sampling voltage is greater than the reference voltage, a conducting signal is output, and when the sampling voltage is less than the reference voltage, a stopping signal is output; the logic module is coupled to the control end of the switch unit, is controlled by the judging module and responds to the conducting/stopping signal to conduct/stop the switch unit; when the switch unit is switched on, the energy storage unit is charged, and when the switch unit is switched off, the energy storage unit discharges to restrain the current of the LED power supply.
Further, the amplification module is configured as a co-directional amplifier.
Further, the detection module is configured as an active detection circuit.
Further, the differential filtering module comprises an open loop amplifier and a low pass filter.
Further, the constant current output circuit of the LED driving power supply is packaged in a chip, and the chip is at least provided with a pin for coupling the LED power supply and a reference voltage input pin.
Further, the switching unit is configured as a MOS transistor.
Further, the energy storage unit is configured as an inductor.
In order to achieve the second object of the present invention, a constant current output method of an LED power supply is characterized by being configured in a constant current output circuit of the LED driving power supply according to any one of claims 1 to 5,
step one, acquiring sampling voltage reflecting output current of an LED power supply;
amplifying the sampling voltage to form an amplified voltage;
thirdly, detecting the amplified voltage to form a modulated voltage;
step four, carrying out difference and filtering on the modulation voltage to form a control voltage;
step five, forming a reversely amplified reference voltage according to the mode of regulating the resistance value by the control voltage, wherein the amplification gain of the reversely amplified reference voltage is greater than 0;
step six, comparing the reference voltage with the sampling voltage to control the on-off of the switch unit;
and step seven, circulating the step one to the step six to enable the sampling voltage to be equal to the reference voltage.
In conclusion, the invention has the following beneficial effects: by the method, the effect of constant current output is realized, the purpose of monitoring the constant current output of the LED power supply is really realized, and the circuit can adopt an external connection mode and is reasonable and convenient to apply.
Drawings
FIG. 1 is a schematic diagram of a sampling operation circuit;
FIG. 2 is a schematic diagram of an implementation circuit;
fig. 3 is a schematic diagram of waveforms.
Detailed Description
The following detailed description of the embodiments of the present invention is provided in order to make the technical solution of the present invention easier to understand and understand.
The invention detects the peak voltage formed by the inductive current on the external precise resistor through the envelope detection technology, compares the peak voltage with a precise reference voltage generated inside to obtain a control voltage, and then utilizes the control voltage to generate a threshold voltage which is inversely changed along with the external inductive current, thereby forcing the inductive current to inversely change, and achieving the purpose of outputting constant current by the LED driving power supply. Compared with the conventional open-loop control, the method has the following advantages in three aspects:
insensitivity to input voltage fluctuations (open loop control, failure to feed back, system delay)
Insensitivity to inductance deviation in mass production (open-loop control of output current with inductance variation)
Insensitivity to LED load voltage variation (open-loop control varying with load voltage)
The specific implementation method comprises the following steps:
the Current _ pick signal in fig. 1 is a sampled signal of the inductor output Current, and after passing through a homodromous amplifying circuit (amplifying module including OP1, R1, and R2) composed of OP1, a voltage V _ cp amplified by about three times is obtained, and the V _ cp is sent to an active detection circuit (detection module including OP2, D1, and C1) composed of OP2, a diode D1, and a capacitor C1, and after detection, a peak envelope V _ cp _ en of the V _ cp is obtained, and the V _ cp _ en is sent to an error amplifier composed of an OP3 differential filter module (including OP3, R3, and C2), and compared with a constant reference voltage Vref1p2V, and a control voltage is obtained through a low-pass filter composed of R3 and C2: vctl.
The control voltage Vctl generated in fig. 1 is used to adjust the resistance of R6(MOS resistor) in fig. 2, so as to change the threshold voltage V _ th, and the Current _ pick signal is compared with the voltage V _ th through the comparator OP4, so as to generate a control signal to the logic control portion, and then the logic control portion turns off the power MOS transistor MN1, so as to ensure that the peak value of the Current _ pick signal of the inductor Current obtained from the external precision sampling resistor R7 is equal to V _ th.
The specific working principle is as follows: for some reason (the input voltage is increased or the output load is decreased), the inductance Current Io is increased, so that the voltage drop Current _ pick on the sampling resistor R7 is increased, the Current _ pick is increased, so that V _ cp and V _ cp _ en are increased, V _ cp _ en is increased, so that the output control signal Vctl is increased, the increased Vctl forces the MOS variable resistor R6 to be decreased, so that the threshold voltage V _ th is decreased, and V _ th is decreased, so that in the comparison with the Current _ pick in the comparator, the control signal for turning off the power MOS transistor MN1 is generated in advance, MN1 is turned off in advance, so that the peak value of the inductance Current Io is decreased, and the average Current value of the inductance Current is decreased, so that the purpose of reducing the inductance Current is achieved, and in the comparator formed by OP3, V _ cp _ en is compared with a constant reference voltage Vref1p2V, so that the stability of V _ cp _ en is ensured, therefore, the constant of the inductive current is finally ensured through the whole closed loop feedback. The voltage waveform of a part of the working points is shown in fig. 3, which is not described herein.
For example, because the mains voltage fluctuates, or the output Current increases due to other conditions, so that the peak voltage of Current _ pick is greater than 400mv, this voltage obtains a triangular pulse signal V _ cp with a peak voltage greater than 1.2V through the operational amplifier circuit composed of OP1 in fig. 1, the V _ cp passes through the peak detector circuit (composed of OP2, D1 and C1, and C1 is greater than 4 Pf), obtains a peak voltage V _ cp _ en greater than 1.2V, which is compared with the standard voltage Vref1p2V of 1.2V, and obtains a control voltage Vctl ranging from 0 to 2.6V through an RC (resistor R3 may be 800k, and capacitor C2 is approximately 4 Pf), which controls the voltage-controlled resistor R6 in fig. 2, (R6 is a resistor whose resistance value decreases as the control voltage increases), so that it generates a reference voltage V _ pick less than 400mv, which is compared with the Current _ pick, when the Current _ pick is larger than V _ th, a negative pulse is generated, the logic control part in fig. 2 is used to reduce the on-time of MN1 and reduce the peak voltage of the Current _ pick, so as to achieve the purpose of reducing the output Current, when the output Current is small, an increased reference voltage value V _ th is obtained through the same control mechanism, and then the on-time of MN1 is increased through the same OP4 comparison circuit and logic control part, so as to achieve the purpose of increasing the output Current.
The present embodiment is only for explaining the present invention, and it is not limited to the present invention, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present invention.
Claims (8)
1. A constant current output circuit of an LED driving power supply is characterized by comprising
The sampling feedback multiplexing module comprises an energy storage unit, a switch unit and a sampling resistor which are sequentially connected in series, wherein the energy storage unit is coupled with the high level of the LED power supply, one end of the sampling resistor is grounded, and the other end of the sampling resistor outputs sampling voltage;
the amplifying module is coupled with the sampling voltage and outputs an amplifying voltage following the sampling voltage;
the detection module is coupled with the amplified voltage and outputs a modulation voltage within a preset amplitude range;
the differential filtering module is coupled with the modulation voltage and outputs a control voltage according to a preset reference voltage;
the reversing voltage regulating module is controlled by the control voltage and outputs a reference voltage of a reverse amplification control voltage; wherein, controlled by the increase of the control voltage, a reduced reference voltage is output, controlled by the decrease of the control voltage, an increased reference voltage is output;
the judging module comprises a comparing unit, the comparing unit is used for comparing the reference voltage with the sampling voltage, when the sampling voltage is smaller than the reference voltage, a conducting signal is output, and when the sampling voltage is larger than the reference voltage, a stopping signal is output;
the logic module is coupled to the control end of the switch unit, is controlled by the judging module and responds to the conducting/stopping signal to conduct/stop the switch unit;
when the switch unit is switched on, the energy storage unit is charged, and when the switch unit is switched off, the energy storage unit discharges to restrain current change of the LED power supply.
2. The constant-current output circuit of an LED driving power supply according to claim 1, wherein the amplifying module is configured as a homodromous amplifier.
3. The constant current output circuit of an LED driving power supply according to claim 1, wherein the wave detection module is configured as an active wave detection circuit.
4. The constant-current output circuit of an LED driving power supply according to claim 1, wherein the differential filter module comprises an open-loop amplifier and a low-pass filter.
5. The constant current output circuit of an LED driving power supply according to any one of claims 1 to 4, wherein the constant current output circuit of the LED driving power supply is packaged in a chip, and the chip is at least provided with a pin for coupling the LED power supply and a reference voltage input pin.
6. The constant current output circuit of an LED driving power supply according to claim 1, wherein the switching unit is configured as a MOS transistor.
7. The constant-current output circuit of the LED driving power supply as claimed in claim 1, wherein the energy storage unit is configured as an inductor.
8. A constant current output method of an LED power supply, which is characterized in that the constant current output method is configured in the constant current output circuit of the LED driving power supply according to any one of claims 1 to 4,
step one, acquiring sampling voltage reflecting output current of an LED power supply;
amplifying the sampling voltage to form an amplified voltage;
thirdly, detecting the amplified voltage to form a modulated voltage;
step four, carrying out difference and filtering on the modulation voltage to form a control voltage;
step five, forming a reversely amplified reference voltage according to the mode of regulating the resistance value by the control voltage, wherein the amplification gain of the reversely amplified reference voltage is greater than 0;
step six, comparing the reference voltage with the sampling voltage to control the on-off of the switch unit;
and step seven, circulating the step one to the step six to enable the sampling voltage to be equal to the reference voltage.
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| CN201610487006.5A CN106131999B (en) | 2016-06-23 | 2016-06-23 | Constant current output circuit and method of LED driving power supply |
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| CN201610487006.5A CN106131999B (en) | 2016-06-23 | 2016-06-23 | Constant current output circuit and method of LED driving power supply |
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| CN106131999B true CN106131999B (en) | 2020-11-03 |
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Effective date of registration: 20220919 Address after: Room 922, Building 2, No. 111 Xiangke Road, China (Shanghai) Pilot Free Trade Zone, Pudong New Area, Shanghai, 201210 Patentee after: Shanghai Fumanduo Semiconductor Co.,Ltd. Address before: 315000 No. 77, Binhai 2nd Road, Hangzhou Bay New Area, Ningbo, Zhejiang Patentee before: NINGBO XINCHEN MICROELECTRONICS Co.,Ltd. |
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