A driving circuit for improving harmonic current

Abstract

The utility model provides a driving circuit for improving harmonic current, including a rectifier unit, a first resistor, a second resistor, an electrolytic capacitor, a linear constant current control unit and an LED driving module; the input end of the rectifier unit is used to connect to a power supply; the output end of the rectifier unit is respectively connected to one end of the first resistor, the positive electrode of the electrolytic capacitor and the power input end of the LED driving module; the linear constant current control unit includes a connected enable end and a drain end; the enable end of the linear constant current control unit is respectively connected to the other end of the first resistor and one end of the second resistor, and the enable end of the linear constant current control unit provides a reference voltage; the drain end of the linear constant current control unit is connected to the negative electrode of the electrolytic capacitor. When the current of the first resistor increases when a large voltage is input externally, the current of the electrolytic capacitor decreases, and vice versa, the current of the electrolytic capacitor increases, thereby achieving improvement of harmonic current while meeting different voltage application requirements.

Description

Technical Field

[0001] The utility model relates to the technical field of LED driving, in particular to a driving circuit for improving harmonic current. Background Art

[0002] The input current harmonics of electronic products will cause serious pollution to the power system, and will also reduce the transmission efficiency of the power grid, resulting in increased loss of power resources. Therefore, different regions have formulated relevant standards to regulate harmonics. For example, Taiwan Standard 15630 stipulates harmonic limits for LED bulbs greater than 5W, requiring that the total harmonic distortion (THD) of the current shall not exceed 120%. However, the voltage supply is different in different regions, such as 220V power supply or 110V power supply, which results in the same LED product being unable to effectively improve the harmonic problem when used in different regions. Therefore, LED products need to be designed according to the power supply voltage for different regions, resulting in increased R&D costs. Utility Model Content

[0003] The technical problem to be solved by the utility model is to provide a driving circuit for improving harmonic current, so as to improve the harmonic current while meeting the application requirements of different voltages.

[0004] In order to solve the above technical problems, the technical solution adopted by the utility model is:

[0005] A drive circuit for improving harmonic current comprises a rectifier unit, a first resistor, a second resistor, an electrolytic capacitor, a linear constant current control unit and an LED drive module; the input end of the rectifier unit is used to be connected to a power supply; the output end of the rectifier unit is respectively connected to one end of the first resistor, the positive electrode of the electrolytic capacitor and the power input end of the LED drive module; the linear constant current control unit comprises an enable end and a drain end which are connected; the enable end of the linear constant current control unit is respectively connected to the other end of the first resistor and one end of the second resistor, and the enable end of the linear constant current control unit provides a reference voltage; the drain end of the linear constant current control unit is connected to the negative electrode of the electrolytic capacitor.

[0006] Furthermore, it also includes a diode; the positive electrode of the diode is connected to the negative electrode of the electrolytic capacitor; and the negative electrode of the diode is grounded.

[0007] Furthermore, the LED driving module includes a driving unit and a filtering unit; the input end of the filtering unit is connected to the output end of the rectifying unit; the output end of the filtering unit is connected to the power input end of the driving unit; and the power output end of the driving unit is used to connect to the LED light source.

[0008] Furthermore, the filtering unit includes a first inductor, a first capacitor and a third resistor; one end of the first inductor is respectively connected to the output end of the rectifier unit and one end of the third resistor; the other end of the first inductor is respectively connected to the other end of the third resistor, the positive electrode of the first capacitor and the power input end of the driving unit; the negative electrode of the first capacitor is grounded.

[0009] Furthermore, the driving unit includes a driving chip, a second capacitor, a second inductor and a fourth resistor; the power input end of the driving chip is respectively connected to the output end of the filtering unit, the positive electrode of the second capacitor and one end of the fourth resistor; the drain end of the driving chip is connected to one end of the second inductor; the other end of the second inductor is respectively connected to the negative electrode of the second capacitor and the other end of the fourth resistor.

[0010] Furthermore, the driving unit further includes a common-mode capacitor; one end of the common-mode capacitor is connected to the other end of the second inductor; and the other end of the common-mode capacitor is grounded.

[0011] Furthermore, the driving unit further includes a fifth resistor; one end of the fifth resistor is connected to the voltage protection terminal of the driving chip; and the other end of the fifth resistor is grounded.

[0012] Furthermore, the driving unit further includes a sixth resistor; one end of the sixth resistor is connected to the current control end of the driving chip; and the other end of the sixth resistor is grounded.

[0013] Furthermore, it also includes a fuse resistor; one end of the fuse resistor is used to be connected to a power source, and the other end of the fuse resistor is connected to an input end of the rectifier unit.

[0014] The beneficial effects of the utility model are as follows: a reference voltage is provided to the second resistor by a linear constant current control unit, so that the current flowing through the second resistor is fixed, and at the same time, the first resistor and the electrolytic capacitor are connected to the second resistor, so that the sum of the current flowing through the first resistor and the current flowing through the electrolytic capacitor is equal to the current of the second resistor; since one end of the first resistor is connected to the power supply and the other end is connected to the reference voltage, the first resistor can change the current according to the input voltage, thereby controlling the current flowing through the electrolytic capacitor, that is, when the external input voltage is large, the current of the first resistor increases, and the current of the electrolytic capacitor decreases, and vice versa, the current of the electrolytic capacitor increases, and by setting an electrolytic capacitor whose current changes with the external input voltage, the improvement of harmonic current is achieved while meeting the requirements of different voltage applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A circuit connection diagram of a harmonic current improved driving circuit in an embodiment of the utility model;

[0016] Description of labels:

[0017] 1. LED driver module; 11. Filter unit; 12. Driver unit; BR1. Rectifier unit; R1. First resistor; R2. Second resistor; R3. Third resistor; R4. Fourth resistor; R5. Fifth resistor; R6. Sixth resistor; F1. Fuse resistor; E1. First capacitor; E2. Second capacitor; E3. Electrolytic capacitor; C2. Common mode capacitor; IC1. Driver chip; IC2. Linear constant current control unit; D1. Diode; L1. First inductor; L2. Second inductor. DETAILED DESCRIPTION

[0018] In order to explain the technical content, achieved objectives and effects of the present invention in detail, the following is an explanation in conjunction with the implementation modes and the accompanying drawings.

[0019] Please refer to Figure 1 , a driving circuit for improving harmonic current, comprising a rectifier unit, a first resistor, a second resistor, an electrolytic capacitor, a linear constant current control unit and an LED driving module; the input end of the rectifier unit is used to connect to a power supply; the output end of the rectifier unit is respectively connected to one end of the first resistor, the positive electrode of the electrolytic capacitor and the power input end of the LED driving module; the linear constant current control unit includes a connected enable end and a drain end; the enable end of the linear constant current control unit is respectively connected to the other end of the first resistor and one end of the second resistor, and the enable end of the linear constant current control unit provides a reference voltage; the drain end of the linear constant current control unit is connected to the negative electrode of the electrolytic capacitor.

[0020] It can be seen from the above description that the beneficial effect of the utility model is that: a reference voltage is provided to the second resistor through a linear constant current control unit, so that the current flowing through the second resistor is fixed, and at the same time, the first resistor and the electrolytic capacitor are connected to the second resistor, so that the sum of the current flowing through the first resistor and the current flowing through the electrolytic capacitor is equal to the current of the second resistor; since one end of the first resistor is connected to the power supply and the other end is connected to the reference voltage, the first resistor can change the current according to the input voltage, thereby controlling the current flowing through the electrolytic capacitor, that is, when the external input voltage is large, the current of the first resistor increases, the current of the electrolytic capacitor decreases, and vice versa, the current of the electrolytic capacitor increases, and by setting an electrolytic capacitor whose current changes with the external input voltage, the improvement of harmonic current is achieved while meeting the requirements of different voltage applications.

[0021] Furthermore, it also includes a diode; the positive electrode of the diode is connected to the negative electrode of the electrolytic capacitor; and the negative electrode of the diode is grounded.

[0022] From the above description, it can be seen that by setting a diode to provide a discharge circuit for the electrolytic capacitor, it is ensured that the electrolytic capacitor can be discharged in time, and the electric energy in the electrolytic capacitor cannot be completely released due to untimely discharge, which affects the normal operation of the electrolytic capacitor when it is powered on again.

[0023] Furthermore, the LED driving module includes a driving unit and a filtering unit; the input end of the filtering unit is connected to the output end of the rectifying unit; the output end of the filtering unit is connected to the power input end of the driving unit; and the power output end of the driving unit is used to connect to the LED light source.

[0024] It can be seen from the above description that the LED driving unit is composed of a filter unit and an LED driving module, and the filter unit provides a more stable and harmonic-free power supply for the LED driving unit.

[0025] Furthermore, the filtering unit includes a first inductor, a first capacitor and a third resistor; one end of the first inductor is respectively connected to the output end of the rectifier unit and one end of the third resistor; the other end of the first inductor is respectively connected to the other end of the third resistor, the positive electrode of the first capacitor and the power input end of the driving unit; the negative electrode of the first capacitor is grounded.

[0026] It can be seen from the above description that the first inductor, the first capacitor and the third resistor are combined to form a π-shaped filter, which can play the role of EMC filtering.

[0027] Furthermore, the driving unit includes a driving chip, a second capacitor, a second inductor and a fourth resistor; the power input end of the driving chip is respectively connected to the output end of the filtering unit, the positive electrode of the second capacitor and one end of the fourth resistor; the drain end of the driving chip is connected to one end of the second inductor; the other end of the second inductor is respectively connected to the negative electrode of the second capacitor and the other end of the fourth resistor.

[0028] From the above description, it can be seen that by setting a driving chip, a second capacitor, a second inductor and a fourth capacitor to form a buck switch circuit, the second capacitor plays an output filtering role, the second inductor plays an energy storage role as a power inductor, and the fourth resistor acts as a dummy load to discharge the second capacitor, so that the driving unit can work stably and realize the corresponding LED control function.

[0029] Furthermore, the driving unit further includes a common-mode capacitor; one end of the common-mode capacitor is connected to the other end of the second inductor; and the other end of the common-mode capacitor is grounded.

[0030] From the above description, it can be seen that EMI can be optimized by setting common-mode capacitors to absorb common-mode interference.

[0031] Furthermore, the driving unit further includes a fifth resistor; one end of the fifth resistor is connected to the voltage protection terminal of the driving chip; and the other end of the fifth resistor is grounded.

[0032] It can be seen from the above description that by setting the fifth resistor to be connected to the voltage protection terminal of the driving chip, the driving chip can be protected from voltage overvoltage.

[0033] Furthermore, the driving unit further includes a sixth resistor; one end of the sixth resistor is connected to the current control end of the driving chip; and the other end of the sixth resistor is grounded.

[0034] It can be seen from the above description that by setting the sixth resistor to be connected to the current control terminal of the driving chip, the output current can be adjusted by adjusting the resistance value of the sixth resistor.

[0035] Furthermore, it also includes a fuse resistor; one end of the fuse resistor is used to be connected to a power source, and the other end of the fuse resistor is connected to an input end of the rectifier unit.

[0036] It can be seen from the above description that the circuit can be protected by providing a fuse resistor, which will fuse and cut off the circuit when a circuit fault occurs.

[0037] The drive circuit for improving harmonic current provided by the utility model can be applied to LED drive circuit scenarios, and can achieve harmonic improvement while meeting voltage application requirements in different regions. The following is an explanation through specific implementation methods:

[0038] Embodiment 1

[0039] Please refer to Figure 1 , a harmonic current improved driving circuit, comprising a rectifier unit BR1, a first resistor R1, a second resistor R2, an electrolytic capacitor E3, a linear constant current control unit IC2 and an LED driving module 1; the input end of the rectifier unit BR1 is used to connect to a power source; the output end of the rectifier unit BR1 is respectively connected to one end of the first resistor R1, the positive electrode of the electrolytic capacitor E3 and the power input end of the LED driving module 1; wherein a fuse resistor F1 and a diode D1 are also provided; one end of the fuse resistor F1 is used to connect to a power source, and the other end of the fuse resistor F1 is connected to the input end of the rectifier unit BR1; such as Figure 1 As shown, the 4th pin of the rectifier unit BR1 is connected to the neutral line (N) of the power supply, the 2nd pin of the rectifier unit BR1 is connected to the fuse resistor F1, and the other end of the fuse resistor F1 is connected to the live line (L) of the power supply; the positive electrode of the diode D1 is connected to the negative electrode of the electrolytic capacitor E3; and the negative electrode of the diode D1 is grounded.

[0040] The linear constant current control unit IC2 includes a connected enable terminal (CS) and a drain terminal (Drain); the enable terminal of the linear constant current control unit IC2 is respectively connected to the other end of the first resistor R1 and one end of the second resistor R2, and the enable terminal of the linear constant current control unit IC2 provides a reference voltage, which can be adjusted according to actual control needs, such as being set to a voltage value such as 0.6V; the drain terminal of the linear constant current control unit IC2 is connected to the negative electrode of the electrolytic capacitor E3; wherein, in this embodiment, the linear constant current control unit IC2 adopts a linear constant current chip of model BP5131J, which can be replaced by other linear constant current chips with equivalent functions.

[0041] The LED driving module 1 includes a driving unit 12 and a filtering unit 11; the input end of the filtering unit 11 is connected to the output end of the rectifying unit BR1; the output end of the filtering unit 11 is connected to the power input end of the driving unit 12; the power output end of the driving unit 12 is used to connect to the LED light source;

[0042] In an optional embodiment, the filtering unit 11 includes a first inductor L1, a first capacitor E1 and a third resistor R3; wherein the first capacitor E1 is an electrolytic capacitor E3; one end of the first inductor L1 is respectively connected to the output end of the rectifier unit BR1 and one end of the third resistor R3; the other end of the first inductor L1 is respectively connected to the other end of the third resistor R3, the positive electrode of the first capacitor E1 and the power input end of the driving unit 12; the negative electrode of the first capacitor E1 is grounded.

[0043] In another optional embodiment, the driving unit 12 includes a driving chip IC1, a second capacitor E2, a common mode capacitor C2, a second inductor L2, a fourth resistor R4, a fifth resistor R5 and a sixth resistor R6; wherein the second capacitor E2 is an electrolytic capacitor E3; the power input end of the driving chip IC1 is respectively connected to the output end of the filtering unit 11, the positive electrode of the second capacitor E2 and one end of the fourth resistor R4; the drain end of the driving chip IC1 is connected to one end of the second inductor L2; the other end of the second inductor L2 is respectively connected to the negative electrode of the second capacitor E2 and the fourth resistor The other end of R4 is connected; one end of the common-mode capacitor C2 is connected to the other end of the second inductor L2; the other end of the common-mode capacitor C2 is grounded; one end of the fifth resistor R5 is connected to the voltage protection end of the driver chip IC1; the other end of the fifth resistor R5 is grounded; one end of the sixth resistor R6 is connected to the current control end of the driver chip IC1; the other end of the sixth resistor R6 is grounded; wherein, the resistors in this embodiment can realize corresponding functions by connecting multiple resistors in series or in parallel; for example, the sixth resistor R6 controls the current of the driver chip IC1 together by being connected in parallel with the resistor R7.

[0044] In dual input voltage 110V (low voltage) and 220V (high voltage) applications, THD (Total Harmonic Distortion) ≤ 120% must be met; the capacitance of the bridge capacitor needs to be limited, and the capacitance cannot be too large, otherwise the conduction angle of the input current charging the bridge capacitor will become smaller, the power factor will become lower, and the harmonics will become higher; especially when the input voltage is high voltage 220V, the capacitance of the bridge capacitor needs to be smaller or the charging current of the capacitor needs to be smaller, so as to extend the charging time of the bridge electrolytic capacitor (i.e., the electrolytic capacitor after the rectifier bridge stack), increase the conduction angle, and reduce THD; in this embodiment, the principle of the above-mentioned harmonic current improvement driving circuit is as follows:

[0045] After the external power source passes through the rectifier unit BR1, the AC power is rectified into a DC power input; the reference voltage provided by the enable end of the linear constant current control unit IC2 to the second resistor R2 is 0.6V, so the current flowing through the second resistor R2 is: I R2 =0.6 / R2, that is, when the resistance value of the second resistor R2 is determined, the current I R2 Since the current of the first resistor R1 and the electrolytic capacitor E3 flows through the second resistor R2, ie I R2 =I R1 +I E3 , so the current of electrolytic capacitor E3 can be obtained as: I E3 =I R2 -I R1 ; The current combined with the first resistor R1 is: I R1 =U / (R6+R7), U represents the voltage of the input power supply, that is, by setting the resistance value of the first resistor R1, I R1 with I E3 When the resistance values ​​of the first resistor R1 and the second resistor R2 are determined, I E3 The current is controlled by the input power supply voltage.

[0046] When the circuit is applied to a 110V low voltage scenario, the input power is 110V. According to formula I R1 =U / (R6+R7), since U is low voltage, I R2 Smaller; then according to formula I E3 =I R2 -I R1 , due to I R2 is smaller, so I E3 is larger, that is, in low input voltage applications, the charging current of the electrolytic capacitor E3 is limited slightly to meet the harmonic requirements.

[0047] When the circuit is applied to a 220V high voltage scenario, the input power is 220V. According to formula I R1=U / (R6+R7), since U is high voltage, I R2 Larger; then according to formula I E3 =I R2 -I R1 , due to I R2 is larger, so I E3 is smaller, that is, in high input voltage applications, the charging current of the electrolytic capacitor E3 will be greatly limited, thereby meeting the harmonic requirements.

[0048] When the harmonic optimization composed of the linear constant current control unit IC2, the first resistor R1, the second resistor R2 and the diode D1 is not set, the normal operation of the driver chip IC1 requires the electrolytic capacitor E3 and the first capacitor E1 after the rectifier bridge to play a filtering and energy storage role. Due to the energy storage function of the electrolytic capacitor E3 and the first capacitor E1, the voltage after the bridge is raised. Therefore, only when the power supply voltage (LN) is higher than the voltage of the electrolytic capacitor E3 and the first capacitor E1, there is current through the rectifier bridge to charge the electrolytic capacitor E3 and the first capacitor E1, resulting in a smaller conduction angle of the input current, the current waveform phase cannot follow the voltage waveform, the power factor is low, and poor harmonic pollution occurs. The present technical solution can solve this problem and improve the harmonics.

[0049] In summary, the harmonic current improved driving circuit provided by the utility model improves the input power factor and improves the input current harmonics through circuit design innovation on the basis of the existing low power factor circuit, meeting the regulatory requirements. It reduces the interference of such current on the power grid in the application, and at the same time, the circuit is simple and easy to operate, the discrete devices used are highly replaceable, and the parameters and device specifications can be flexibly adjusted according to the product technical requirements to reduce costs.

[0050] The above description is only an embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent transformations made using the contents of the specification and drawings of the present invention, or directly or indirectly applied in the relevant technical field, are also included in the patent protection scope of the present invention.

Claims

1. A driving circuit for improving harmonic current, characterized in that: It includes a rectifier unit, a first resistor, a second resistor, an electrolytic capacitor, a linear constant current control unit and an LED driving module; The input end of the rectifier unit is used to connect to a power source; The output end of the rectifier unit is respectively connected to one end of the first resistor, the positive electrode of the electrolytic capacitor and the power input end of the LED driving module; The linear constant current control unit internally includes an enable terminal and a drain terminal connected to each other; The enable end of the linear constant current control unit is respectively connected to the other end of the first resistor and one end of the second resistor, and the enable end of the linear constant current control unit provides a reference voltage; The drain end of the linear constant current control unit is connected to the negative electrode of the electrolytic capacitor.

2. A harmonic current improved driving circuit according to claim 1, characterized in that: Also includes diodes; The positive electrode of the diode is connected to the negative electrode of the electrolytic capacitor; The cathode of the diode is grounded.

3. The drive circuit for improving harmonic current according to claim 1, characterized in that: The LED driving module includes a driving unit and a filtering unit; The input end of the filtering unit is connected to the output end of the rectifying unit; The output end of the filter unit is connected to the power input end of the drive unit; The power output end of the driving unit is used to connect to the LED light source.

4. A driving circuit for improving harmonic current according to claim 3, characterized in that: The filtering unit includes a first inductor, a first capacitor and a third resistor; One end of the first inductor is respectively connected to the output end of the rectifier unit and one end of the third resistor; The other end of the first inductor is respectively connected to the other end of the third resistor, the positive electrode of the first capacitor and the power input end of the driving unit; A negative electrode of the first capacitor is grounded.

5. The drive circuit for improving harmonic current according to claim 3, characterized in that: The driving unit includes a driving chip, a second capacitor, a second inductor and a fourth resistor; The power input terminal of the driving chip is respectively connected to the output terminal of the filtering unit, the positive electrode of the second capacitor and one end of the fourth resistor; The drain terminal of the driving chip is connected to one end of the second inductor; The other end of the second inductor is connected to the negative electrode of the second capacitor and the other end of the fourth resistor respectively.

6. A harmonic current improved driving circuit according to claim 5, characterized in that: The driving unit further includes a common mode capacitor; One end of the common mode capacitor is connected to the other end of the second inductor; The other end of the common mode capacitor is grounded.

7. The drive circuit for improving harmonic current according to claim 5, characterized in that: The driving unit further includes a fifth resistor; One end of the fifth resistor is connected to the voltage protection end of the driving chip; The other end of the fifth resistor is grounded.

8. The drive circuit for improving harmonic current according to claim 5, characterized in that: The driving unit further includes a sixth resistor; One end of the sixth resistor is connected to the current control end of the driving chip; The other end of the sixth resistor is grounded.

9. The drive circuit for improving harmonic current according to claim 1, characterized in that: Also includes a fuse resistor; One end of the fuse resistor is used to be connected to a power source, and the other end of the fuse resistor is connected to an input end of the rectifier unit.

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