CN106612578A - Driving circuit capable of suppressing electromagnetic interference - Google Patents

Abstract

The application discloses drive circuit with restrain electromagnetic interference, drive circuit includes drive unit, power switching unit and constant current unit. The first end of the inductor of the power switching unit is coupled to the driving unit, the second end of the inductor is coupled to the diode and the first transistor respectively, the third end of the first transistor is coupled to the ground terminal, the first impedance element is connected to the first end or the second end of the diode, the second impedance element is connected to the first end or the third end of the first transistor, the first end of the third impedance element is connected to the second end of the first transistor, and the second end of the third impedance element is coupled to the driving unit.

Description

A drive circuit with electromagnetic interference suppression

technical field

The invention relates to a driving circuit, in particular to a driving circuit capable of suppressing electromagnetic interference (ElectroMagnetic Interference, EMI).

Background technique

Although the known halogen bulbs have high brightness and are often used in projection lamps, they have been gradually replaced by low-wattage (such as 3W-10W) light-emitting diode (LED) projection bulbs due to their large power consumption (such as 50W). replace.

In a known LED projection lamp, such as the standard MR16 (Multifaceted Reflector, multiple reflector) type LED projection bulb, its drive circuit cannot pass the safety requirements of electromagnetic interference (EN55015class B), and even exceeds the safety standards. 20dB. At present, the problem of electromagnetic interference is usually solved by using a common mode choke (or common mode inductor or common mode coil). However, at the currents required by the original circuit, such components are too bulky to fit into a standard MR16 type (ANSI standard, eg ANSI C78.1413-2001) bulb. In addition, there is also a snubber circuit to suppress the electromagnetic interference caused by high-frequency switching, but the addition of the snubber circuit has a great impact on the luminous efficiency, and the effect of suppressing electromagnetic interference is also quite limited (only 5-10dB of suppression ability ), unable to meet the requirements of safety regulations.

Contents of the invention

The object of the present invention is to provide a driving circuit capable of suppressing electromagnetic interference. The drive circuit of the present invention can achieve the effect of suppressing electromagnetic interference under specific space requirements. Preferably, the suppression effect of electromagnetic interference can meet the requirements of laws and regulations.

In order to achieve the above object, according to the present invention, a drive circuit with electromagnetic interference suppression is provided, which drives a light-emitting unit to emit light, and the drive circuit includes a drive unit, a power switching unit and a constant current unit. The power switching unit is coupled to the drive unit, and has an inductor, a diode, a first transistor, a first impedance element, a second impedance element and a third impedance element, the first end of the inductor is coupled to the drive unit, and the second end is respectively coupled to The diode and the first transistor are connected, the third end of the first transistor is coupled to the ground end, the first impedance element is connected to the first end or the second end of the diode, and the second impedance element is connected to the first end or the second end of the first transistor. The third end, the first end of the third impedance element is connected to the second end of the first transistor, and the second end of the third impedance element is coupled to the driving unit. The constant current unit is respectively coupled to the power switching unit, the driving unit and the light emitting unit, and the driving unit controls the constant current unit to output a certain current to drive the light emitting unit to emit light.

In one embodiment, the first impedance element is connected between the second end of the inductor and the first end of the diode, and the first end of the first transistor is respectively connected to the second end of the inductor and the first end of the first impedance element, And the second impedance element is connected between the third end of the first transistor and the ground end.

In one embodiment, the first impedance element is connected between the second end of the inductor and the first end of the diode, and the first end of the second impedance element is respectively connected to the second end of the inductor and the first end of the first impedance element. terminal, the second terminal of the second impedance element is connected to the third terminal of the first transistor, and the third terminal of the first transistor is connected to the ground terminal.

In one embodiment, the second end of the inductor is respectively connected to the first end of the diode and the first end of the first transistor, the first impedance element is connected between the second end of the diode and the constant current unit, and the second impedance element connected between the third terminal of the first transistor and the ground terminal.

In one embodiment, the second end of the inductor is respectively connected to the first end of the diode and the first end of the second impedance element, the first impedance element is connected between the second end of the diode and the constant current unit, and the second impedance element The second end of the first transistor is connected to the first end of the first transistor, and the third end of the first transistor is connected to the ground end.

In one embodiment, the first impedance element or the second impedance element or the third impedance element of the power switching unit is a magnetic bead or a resistor.

In one embodiment, the inductor, the diode, the first transistor, the first impedance element, the second impedance element and the third impedance element of the power switching unit are integrated into an integrated circuit.

In one embodiment, the driving circuit further includes a rectification unit and a detection unit. The rectification unit is coupled to the drive unit and the power switching unit. The detection unit is respectively coupled with the rectification unit, the power switching unit and the driving unit.

In one embodiment, the drive circuit further includes an energy discharge unit, which is respectively coupled to the power switching unit, the constant current unit, and the drive unit, and the energy discharge unit is used in conjunction with the phase dimmer.

In one embodiment, the constant current unit has a first capacitor, a fourth impedance element, and a fifth impedance element, and the first end of the first capacitor is respectively connected to the second end of the diode of the power switching unit and the first end of the fourth impedance element. end, the second end of the fourth impedance element is connected to the first end of the light emitting unit, the first end of the fifth impedance element is connected to the second end of the first capacitor, and the second end of the fifth impedance element is connected to the second end of the light emitting unit.

In one embodiment, the constant current unit further has a first resistor, a second resistor and a second transistor, and the first end of the first resistor is respectively connected to the first end of the fifth impedance element and the second end of the first capacitor, which The second terminal is respectively connected to the first terminal of the second resistor and the driving unit, the second terminal of the second resistor is connected to the ground terminal, and the second terminal and the third terminal of the second transistor are respectively coupled to the driving unit.

In one embodiment, the constant current unit further has a third resistor and a second capacitor, the first end of the second capacitor is connected to the second end of the second transistor and the driving unit, and the first end of the third resistor is respectively connected to the second transistor The third terminal of the drive unit and the second terminal are connected to the ground terminal.

In one embodiment, the fourth impedance element or the fifth impedance element is a magnetic bead or a resistor.

In one embodiment, the driving circuit is applied to a multiple reflector type LED light bulb.

As mentioned above, in the driving circuit of the present invention, due to the main reason of electromagnetic interference, the operating frequency of the integrated circuit of the driving circuit is too high, and the problems generated in the power switching unit are relatively serious. Therefore, by arranging a plurality of impedance elements in the power switching unit, the present invention not only enables the driving circuit to meet the specific circuit space requirements of the light bulb, but also achieves the effect of suppressing electromagnetic interference. In one embodiment, in addition to arranging a plurality of impedance elements on the power switching unit, a plurality of impedance elements are also arranged on the constant current unit, which can also meet the specific circuit space requirements of the light bulb, and make the suppression effect of electromagnetic interference more effective. meet regulatory requirements.

Description of drawings

FIG. 1 is a functional block diagram of a drive circuit with electromagnetic interference suppression in a preferred embodiment of the present invention.

FIG. 2A is a schematic circuit diagram of a driving circuit of an embodiment.

FIG. 2B is an enlarged schematic diagram of a power switching unit of the driving circuit in FIG. 2A .

2C to 2E are schematic circuit diagrams of driving circuits in different implementations of the preferred embodiment of the present invention.

FIG. 2F is an enlarged schematic diagram of a constant current unit of the driving circuit in FIG. 2E .

FIGS. 3A and 3B , and FIGS. 4A and 4B are schematic diagrams of electromagnetic interference curves at different operating frequencies before and after adding impedance elements to the driving circuit in the embodiment of the present invention.

detailed description

A drive circuit with electromagnetic interference suppression according to a preferred embodiment of the present invention will be described below with reference to related drawings, wherein the same components will be described with the same reference numerals.

Please refer to Fig. 1, Fig. 2A and Fig. 2B, wherein, Fig. 1 is a functional block diagram of a drive circuit 1 with electromagnetic interference suppression in a preferred embodiment of the present invention, and Fig. 2A is a circuit of the drive circuit 1 of the embodiment 2B is a schematic diagram of an enlarged circuit of the power switching unit 14 of the driving circuit 1 of FIG. 2A .

The driving circuit 1 of this embodiment has the function of suppressing electromagnetic interference and can be applied, for example but not limited to, to drive a standard MR type LED light bulb, thereby driving the light emitting unit 2 including at least one LED to emit light. Since the circuit installation space of the MR16 type light bulb is quite limited, the driving circuit 1 has a certain space size limitation. Among them, "MR" means a multifaceted reflector, and MR16 means that the front diameter of the bulb is 2 inches (that is, the diameter is about 5 cm long). In other words, the drive circuit 1 of the present embodiment can achieve the effect of suppressing electromagnetic interference (EMI) under the specific space requirement of the MR16 bulb, and preferably, can meet the requirements of safety regulations. However, in different embodiments, the driving circuit 1 can also be applied to other types of LED bulbs, and is not limited to a circuit that can only be applied to standard MR-type LED bulbs.

As shown in FIG. 1 , the driving circuit 1 includes a driving unit 11 , a power switching unit 14 and a constant current unit 16 . In addition, the driving circuit 1 of this embodiment further includes a rectification unit 12 , a detection unit 13 and an energy discharge unit 15 . Wherein, the “coupling” mentioned below may be a physical electrical connection or a physical electrical connection through other elements or a non-physical signal connection, and is not limited. In addition, "connection" may be a direct connection of physical elements, or an indirect connection through other elements, and is not limited thereto.

As shown in Figure 1, the drive unit 11 is respectively coupled with the rectification unit 12, the detection unit 13, the power switching unit 14, the energy discharge unit 15 and the constant current unit 16, and outputs a control signal to control the detection unit 13, the power switching unit 14 and the The constant current unit 16 controls the constant current unit 16 to output a certain current to drive the light emitting unit 2 to emit light. In this embodiment, the drive unit 11 is a circuit composed of an integrated circuit (marked as IC1), four capacitors (marked as C6, C7, C _VCC , C _OFF ) and a resistor (marked as R _OFF ). For the connection relationship, please refer to FIG. 2A . Those skilled in the art can clearly understand the connection relationship of these components from the schematic circuit diagram of FIG. 2A , and details are not repeated here.

The rectification unit 12 is coupled to the driving unit 11 , the detection unit 13 and the power switching unit 14 , and can receive an input voltage. Wherein, the input voltage may be different according to the design requirements of the rectifying unit 12 and the light emitting unit 2 (different implementations may have different input voltages); in one embodiment, the input voltage may be, for example, alternating current (AC) 12V or direct current ( DC) 12V; in different embodiments, the input voltage can also be other voltage values, which is not limited, depending on the specifications of the rectifying unit 12 and the requirements of the LEDs of the light emitting unit 2 . Wherein, after the input voltage is rectified by the rectification unit 12 , a direct current can be obtained and input to the detection unit 13 . The rectification unit 12 of this embodiment is a full-wave rectification unit, and can be a bridge rectifier, as shown in Figure 2A, it includes 4 diodes DB1-DB4, and the connection relationship of the bridge rectifiers (diodes DB1-DB4) is a known technology , no further explanation will be given here.

The detection unit 13 is a circuit composed of three capacitors (marked as C3, C4, C5), three resistors (marked as R4, R5, R6), a diode (marked as D2) and a transistor (marked as Q3) . One end of the transistor Q3 is connected to the rectifier circuit 12 and the power switching unit 14 through the capacitor C3 , and the other end is coupled to the power switching unit 14 and the integrated circuit IC1 (pin 3 ) of the driving unit 11 . In addition, the control terminal (gate) of the transistor Q3 is connected to the capacitor C4 and the resistor R4 and connected to the integrated circuit IC1 (pin 4 ) of the driving circuit 11 to be turned on or off under the control of the integrated circuit IC1 . In addition, the anode of the diode D2 is connected to the integrated circuit IC1 (pin 5 ) through the resistor R5 , and is connected to the resistor R6 and the capacitor C6 respectively, and the cathode of the diode D2 is connected to the input terminal and the diode DB4 of the rectifier unit 12 . The detailed connection relationship of the components of the detection unit 13 can refer to FIG. 2A .

The rectification unit 12 and the detection unit 13 of this embodiment are set up to solve the problem of transformer compatibility. This compatibility means that the original transformer is provided for, for example, a 50W halogen bulb, but when driving the light-emitting unit 2 with LED, due to The load characteristics are different, and the power is also low (for example, 3W~10W). Therefore, when the circuit originally used for halogen lamps is used to drive the light-emitting unit 2 with LEDs, it may cause the LEDs to fail to start or flicker. . Therefore, in this embodiment, the rectification unit 12 and the detection unit 13 need to be added to overcome the problem that the LED cannot be activated or flickers. In different embodiments, the rectification unit 12 and the detection unit 13 may not be provided.

In addition, please refer to FIG. 2A and FIG. 2B , the power switching unit 14 is respectively coupled to the driving unit 11 , the rectifying unit 12 , the detecting unit 13 , the energy discharging unit 15 and the constant current unit 16 . The power switching unit 14 of this embodiment has an inductor L1, a diode D1, a first transistor Q1, a first impedance element B1, a second impedance element B2, and a third impedance element B3. In addition, the power switching unit 14 further has a resistor R0.

A first end of the inductor L1 is coupled to the driving unit 11 , a second end thereof is respectively coupled to the diode D1 and the first transistor Q1 , and a third end of the first transistor Q1 is coupled to the ground end. In addition, the first impedance element B1 is connected to the first end or the second end of the diode D1, the second impedance element B2 is connected to the first end or the third end of the first transistor Q1, and the first end of the third impedance element B3 is connected to The second end of the first transistor Q1 and the second end of the third impedance element B3 are coupled to the driving unit 11 .

In this embodiment, the first end of the inductor L1 is coupled to the driving unit 11 through the detection unit 13 . Here, the first end of the inductor L1 is connected to one end of the capacitor C3 of the detection unit 13 and the output end of the rectification unit 12 (the cathode of the diode DB3), so that the signal output from the output end of the rectification unit 12 can be received by the inductor L1, and the inductor The second end of L1 is respectively connected to the first end of the first impedance element B1 and the first end of the first transistor Q1, and the first impedance element B1 is connected between the second end of the inductor L1 and the first end (anode) of the diode D1 between. In addition, the first end of the first transistor Q1 is respectively connected to the second end of the inductor L1 and the first end of the first impedance element B1, and the second impedance element B2 is connected between the third end of the first transistor Q1 and the ground end .

In addition, the second terminal (cathode) of the diode D1 is respectively connected to the energy drain unit 15 , the integrated circuit IC1 (pin 14 ) of the driving unit 11 and the constant current unit 16 . In addition, the second end (control end, gate) of the first transistor Q1 is connected to the first end of the third impedance element B3, and the second end of the third impedance element B3 is connected to the integrated circuit IC1 (pin 1 of the driving unit 11 ). ). In addition, the first end of the resistor R0 is respectively connected to the third end of the transistor Q3 of the detection unit 13 and the integrated circuit IC1 (pin 3 ) of the driving unit 11, and its second end is respectively connected to the second end of the second impedance element B2, The integrated circuit IC1 (pins 2 and 12 ) of the driving unit 11 and the ground terminal.

The integrated circuit IC1 of the driving unit 11 outputs a high-frequency switching signal, such as but not limited to a pulse width modulation (Pulse width modulation, PWM) signal to control the first transistor Q1 to work in the on/off region, so as to control the first transistor Q1 switching action, and then provide the voltage and current required to drive the light-emitting unit 2 through the energy storage of the inductor L1; because the high-frequency operating frequency of the integrated circuit IC1 will cause the problem of electromagnetic interference in the driving circuit 1, therefore, the present embodiment The power switching unit 14 suppresses electromagnetic interference by adding three impedance elements (the first impedance element B1 , the second impedance element B2 and the third impedance element B3 ) in a boost circuit structure.

The first impedance element B1 or the second impedance element B2 or the third impedance element B3 may be a ferrite bead or a resistor. In this embodiment, the first impedance element B1 , the second impedance element B2 and the third impedance element B3 are respectively magnetic beads as an example. The magnetic bead is a component composed of a ferrite alloy powder, and the material of the alloy will affect the frequency band of the filtering effect; when electromagnetic interference is injected into the surface of the material of the magnetic bead, a very thin layer will be formed on the surface of the component The magnetic wall, the magnetic material inside the wall will cause mutual friction between molecules due to the spin precession effect of the electromagnetic energy injected from the outside, thereby converting the energy of electromagnetic interference into heat energy and dissipating it. In this embodiment, by adding the first impedance element B1 , the second impedance element B2 and the third impedance element B3 in the power switching unit 14 , high-frequency electromagnetic interference signals can be suppressed. In addition, in one embodiment, the first impedance element B1, the second impedance element B2, and the third impedance element B3 can be integrated with the inductor L1, the diode D1, the first transistor Q1, and the resistor R0 into an integrated circuit (that is, power switching The elements of the unit 14 are integrated and made into an IC), thereby reducing space usage, and more conforming to the circuit setting space of the MR16 type light bulb.

In addition, the Bleeder unit 15 is coupled to the power switching unit 14 , the constant current unit 16 and the driving unit 11 respectively. The energy drain unit 15 is mainly configured to carry a silicon controlled rectifier (TRIAC) phase dimmer. In other words, the energy drain unit 15 makes the LED driver compatible with the silicon controlled rectifier dimmer, so as to achieve the purpose of dimming. The energy discharge unit 15 of this embodiment is a resistor R4, one end of the resistor R4 is respectively connected to the cathode of the diode D1 of the power switching unit 14, one end of the capacitor C6, one end of the capacitor C7 and the constant current unit 16, and the other end of the resistor R4 is connected to the drive unit 11 integrated circuit IC1 (pin 15). In another embodiment, the energy-discharging unit 15 may not be provided.

The constant current unit 16 is respectively coupled to the energy drain unit 15 , the power switching unit 14 , the driving unit 11 and the light emitting unit 2 , and the driving unit 11 can control the constant current unit 16 to output a certain current to drive the light emitting unit 2 to emit light. As shown in FIG. 2A , the constant current unit 16 of this embodiment has a first capacitor C1 , a first resistor R1 , a second resistor R2 , a third resistor R3 , a second transistor Q2 and a second capacitor C2 . The first transistor Q1 , the second transistor Q2 and the third transistor Q3 in this embodiment may be, for example but not limited to, n-channel metal-oxide-semiconductor field-effect transistors (Metal-Oxide-Semiconductor Field-Effect Transistor, MOSFET).

The first end of the first capacitor C1 is respectively connected to the second end of the diode D1 of the power switching unit 14 and the first end (anode) of the light emitting unit 2, and the second end of the first capacitor C1 is respectively connected to the second end of the first resistor R1. One terminal, the first terminal of the second transistor Q2 and the second terminal (negative pole) of the light emitting unit 2 . In addition, the second end of the first resistor R1 is respectively connected to the first end of the second resistor R2 and the integrated circuit IC1 (pin 11 ) of the driving unit 11 , and the second end of the second resistor R2 is respectively connected to the integrated circuit of the driving unit 11 . The circuit IC1 (pin 12 ) and the ground terminal, and the second terminal (control terminal, gate) and third terminal of the second transistor Q2 are respectively coupled to the integrated circuit IC1 (pin 9 , pin 10 ) of the driving unit 11 . In addition, the first terminal of the second capacitor C2 is also connected to the second terminal (control terminal, gate) of the second transistor Q2 and the integrated circuit IC1 (pin 9 ) of the driving unit 11, and the first terminal of the third resistor R3 The third terminal of the second transistor Q2 is respectively connected to the integrated circuit IC1 (pin 10 ) of the driving unit 11 , and the second terminal thereof is connected to the ground terminal and the integrated circuit IC1 (pin 12 ).

In this embodiment, the control terminal (gate) of the second transistor Q2 is controlled by the integrated circuit IC1 to work in its linear region, so as to turn on the channel ratio of the second transistor Q2 according to the gate input current, so that the second transistor Q2 The current flowing from the second terminal of Q2 to the third terminal is a constant current, so that the current flowing through the light emitting unit 2 is a constant current, thereby driving the light emitting unit 2 to emit light.

In addition, please refer to FIG. 2C and FIG. 2D , which are schematic circuit diagrams of driving circuits 1a and 1b in different implementations of the preferred embodiment of the present invention.

As shown in FIG. 2C, the first impedance element B1 of the power switching unit 14a of the driving circuit 1a is also connected between the second end of the inductance L1 and the first end of the diode D1. The difference is that the first end of the second impedance element B2 of the power switching unit 14a is respectively connected to the second end of the inductor L1 and the first end of the first impedance element B1, and the second end of the second impedance element B2 is connected to the first end of the first impedance element B2. The second terminal of the transistor Q1 and the third terminal of the first transistor Q1 are connected to the ground terminal and the second terminal of the resistor R0 respectively.

In addition, as shown in FIG. 2D, the second impedance element B2 of the power switching unit 14b of the drive circuit 1b is also connected between the third terminal of the first transistor Q1 and the ground terminal, but the same as that of the drive circuit 1 of FIG. 2A The difference is that the second end of the inductor L1 of the power switching unit 14b is respectively connected to the first end of the diode D1 and the first end of the first transistor Q1, and the first impedance element B1 is connected between the second end (cathode) of the diode D1 and the first end of the first transistor Q1. Between the energy discharge unit 15 and the constant current unit 16 .

In addition, other technical features of the driving circuits 1a, 1b can refer to the same elements of the driving circuit 1, and will not be repeated here.

It should be mentioned again that, in another embodiment (not shown in the figure), the first impedance element B1 of the driving circuit can be connected between the second end of the diode D1 and the constant current unit 16, and the second end of the inductor L1 The first end of the diode D1 and the first end of the second impedance element B2 can be respectively connected, the second end of the second impedance element B2 is connected to the first end of the first transistor Q1, and the third end of the first transistor Q1 is connected to ground end. In other words, in different implementations, with respect to the driving circuit 1b, when the second impedance element B2 is connected between the second end of the inductor L1 (and the first end of the diode D1) and the first end of the first transistor Q1 , the drive circuit also has the effect of suppressing electromagnetic interference.

In addition, please refer to FIG. 2E and FIG. 2F respectively, wherein FIG. 2E is a schematic circuit diagram of a drive circuit 1c in yet another embodiment of a preferred embodiment of the present invention, and FIG. 2F is a constant current unit 16c of the drive circuit 1c in FIG. 2E The enlarged schematic diagram of the circuit.

As shown in FIG. 2E and FIG. 2F , compared with the driving circuit 1 of FIG. 2A , the main difference between the driving circuit 1c of this embodiment and the driving circuit 1 of FIG. In addition to a capacitor C1, a first resistor R1, a second resistor R2, a third resistor R3, a second transistor Q2 and a second capacitor C2, the constant current unit 16c of this embodiment further has a fourth impedance element B4 and a fifth impedance Element B5. Wherein, the first end of the first capacitor C1 is respectively connected to the second end of the diode D1 of the power switching unit 14 and the first end of the fourth impedance element B4, and the second end of the fourth impedance element B4 is connected to the first end of the light emitting unit 2. terminal (positive pole), and the first terminal of the fifth impedance element B5 is connected to the second terminal of the first capacitor C1, and its second terminal is connected to the second terminal (negative pole) of the light emitting unit 2 . In addition, the first end of the first resistor R1 is respectively connected to the first end of the fifth impedance element B5 and the second end of the first capacitor C1, and its second end is respectively connected to the first end of the second resistor R2 and the drive unit 11. integrated circuit IC1 (pin 11), and the second end of the second resistor R2 is respectively connected to the integrated circuit IC1 (pin 12) of the driving unit 11 and the ground end, and the second end (control end, gate) of the second transistor Q2 pole) and the third terminal are respectively coupled to the integrated circuit IC1 (pin 9 and pin 10 ) of the drive unit 11 . In addition, the first terminal of the second capacitor C2 is connected to the second terminal (control terminal, gate) of the second transistor Q2 and the integrated circuit IC1 (pin 9 ) of the driving unit 11, and the first terminals of the third resistor R3 are respectively The third terminal of the second transistor Q2 is connected to the integrated circuit IC1 (pin 10 ) of the driving unit 11 , and the second terminal thereof is connected to the ground terminal.

Similarly, the gate of the second transistor Q2 in this embodiment is controlled by the integrated circuit IC1 and operates in its linear region, so that the channel ratio of the second transistor Q2 is turned on according to the gate input current, so that the second transistor Q2 is controlled by the second transistor Q2. The current flowing from the two terminals to the third terminal is a constant current, so that the current flowing through the light emitting unit 2 is a constant current, thereby driving the light emitting unit 2 to emit light. However, since the control of the second transistor Q2 by the integrated circuit IC1 will also cause electromagnetic interference, this embodiment further suppresses the electromagnetic interference generated by the second transistor Q2 by adding two impedance elements B4 and B5 in the constant current unit 16c. interference problem. The fourth impedance element B4 or the fifth impedance element B5 can also be a magnetic bead or a resistor. In this embodiment, the fourth impedance element B4 and the fifth impedance element B5 are respectively magnetic beads as an example.

In addition, please refer to FIG. 3A to FIG. 4B, wherein, FIG. 3A and FIG. 3B, and FIG. After (that is, the driving circuit 1c in FIG. 2E ), a schematic diagram of electromagnetic interference curves at different operating frequencies. 3A and 3B are graphs of electromagnetic waves on horizontal performance (Horizontal Performance), and FIGS. 4A and 4B are graphs of electromagnetic waves on vertical performance (Vertical Performance).

As shown in FIG. 3A , the broken line L is the safety standard of the MR16 type LED light bulb at different frequencies. In the test of horizontal performance, before adding impedance elements (B1~B5, magnetic beads), the peak values of electromagnetic waves (points 1~5) generated by the integrated circuit IC1 of the driving circuit at different operating frequencies all exceed the broken line L (A gauge standard), and the highest value exceeded (point 5) reached 23.99dB. However, as shown in FIG. 3B, after setting three impedance elements (B1, B2, B3) in the power switching unit 14 and setting two impedance elements (B4, B5) in the constant current unit 16c, at different operating frequencies The peak value of the electromagnetic waves (points 1 to 3) generated under the condition is only about 24dB at most, which is lower than the requirements of regulations.

In addition, as shown in Figure 4A, in the vertical performance test, before adding impedance elements (B1-B5, magnetic beads), the peak values of electromagnetic waves (points 1-7) generated by the drive circuit at different operating frequencies all exceeded Safety standard, and exceeds the highest value (point 7) to reach 19.75dB. However, as shown in FIG. 4B, after setting three impedance elements (B1, B2, B3) in the power switching unit 14 and two impedance elements (B4, B5) in the constant current unit 16c, under different operating frequencies The peak value of the generated electromagnetic waves (points 1-4) is about 30dB at most, which also meets the requirements of regulations.

As mentioned above, in the drive circuits 1, 1a-1c of this embodiment, due to the main electromagnetic interference, the operating frequency of the integrated circuit IC1 of the drive circuit 11 is too high, and the EMI generated by the power switching unit and the constant current unit The problem is more serious, therefore, in the driving circuit 1, 1a, 1b, by correspondingly setting three impedance elements (B1, B2, B3) in the power switching unit 14, 14a, 14b, and in the driving circuit 1c, setting two Impedance elements (B4, B5) in the constant current unit 16c not only make the drive circuits 1, 1a-1c meet the specific space requirements of standard MR16 LED light bulbs, but also achieve the effect of suppressing electromagnetic interference, and in the drive circuit 1c In the embodiment, the suppression effect of electromagnetic interference can meet the requirements of regulations.

In addition, it is supplemented that if the circuit originally driving the light emitting unit 2 is not provided with any of the above-mentioned impedance elements B1-B5, the EMI will exceed the safety standard by about 20-30 dB. If the common mode choke coil is used to suppress EMI like the known technology, although it has the effect of suppressing EMI, it is impossible to place all the driving circuits in the standard MR16 type bulb; if the EMI is suppressed by adding a snubber circuit, then Not only does it have a great impact on the luminous efficiency, but also the effect of suppressing EMI interference is quite limited (only 5-10dB suppression capability), which cannot meet the requirements of safety regulations. And through the circuit design of the composite component of the present invention, not only the circuit component can be placed in the standard MR16 bulb, but also the problem of EMI exceeding the standard can be solved. Furthermore, in the above-mentioned power switching units 14, 14a, 14b, the impedance elements B1-B3 can be integrated with other components into an integrated circuit (that is, the components of the power switching unit 14 are integrated and made into an IC), thus Reduce space usage. In addition, due to the limited circuit setting space of the standard MR16 LED light bulb, in implementation, the driving circuits 1, 1a-1c use 4-layer boards. If smaller components or ICs or transistors integrating external parts are used in the future, Then it is not limited to use a 4-layer board, but can also be simplified to, for example, a 2-layer board.

To sum up, in the driving circuit of the present invention, due to the main reason of electromagnetic interference, the operating frequency of the integrated circuit of the driving circuit is too high, and the problems generated in the power switching unit are relatively serious. Therefore, by arranging a plurality of impedance elements in the power switching unit, the present invention not only enables the driving circuit to meet the specific circuit space requirements of the light bulb, but also achieves the effect of suppressing electromagnetic interference. In one embodiment, in addition to arranging a plurality of impedance elements on the power switching unit, a plurality of impedance elements are also arranged on the constant current unit, which can also meet the specific circuit space requirements of the light bulb and reduce the electromagnetic interference of the driving circuit. The suppression effect can meet the requirements of regulations.

The above description is for illustration only, not for limitation. Any equivalent modification or change made without departing from the spirit and scope of the present invention shall be included in the scope of the attached patent application.

Claims (14)

1. a kind of drive circuit with suppression electromagnetic interference, it drives luminescence unit to light, described to drive electricity Road includes：

Driver element；

Power supply switch unit, with the driver element coupling, and with inductance, diode, the first transistor, First impedor, the second impedor and the 3rd impedor, the first end of the inductance couples the drive Moving cell, its second end is respectively coupled to the diode and the first transistor, the first transistor 3rd end is coupled in earth terminal, and first impedor is connected to the first end of the diode or the second end, Second impedor is connected to the first end of the first transistor or the 3rd end, the 3rd impedance element The first end of part connects the second end of the first transistor, and the 3rd impedor second end coupling The driver element；And

Constant current unit, respectively with the power supply switch unit, the driver element and the luminescence unit coupling Connect, and the driver element controls the certain electric current of the constant current unit output and drives the luminescence unit to light.

2. drive circuit according to claim 1, wherein first impedor is connected to the electricity Between second end of sense and the first end of the diode, the first end of the first transistor connects respectively institute The second end and the described first impedor first end of inductance are stated, and second impedor is connected to institute State between the 3rd end of the first transistor and the earth terminal.

3. drive circuit according to claim 1, wherein first impedor is connected to the electricity Between second end of sense and the first end of the diode, the second impedor first end connects respectively In the second end of the inductance and the described first impedor first end, described second impedor second 3rd end of the end connection the first transistor, and earth terminal described in the three-terminal link of the first transistor.

4. drive circuit according to claim 1, wherein the second end of the inductance connects respectively described The first end of the first end of diode and the first transistor, first impedor is connected to described two Between second end of pole pipe and the constant current unit, and second impedor to be connected to described first brilliant Between 3rd end of body pipe and the earth terminal.

5. drive circuit according to claim 1, wherein the second end of the inductance connects respectively described The first end of diode and the described second impedor first end, first impedor is connected to described Between second end of diode and the constant current unit, the second impedor second end connection is described The first end of the first transistor, and earth terminal described in the three-terminal link of the first transistor.

6. drive circuit according to claim 1, wherein first resistance of the power supply switch unit Anti- element or second impedor or the 3rd impedor are magnetic bead or resistance.

7. drive circuit according to claim 1, wherein the inductance of the power supply switch unit, The diode, the first transistor, first impedor, second impedor and described 3rd impedor is integrated into integrated circuit.

8. drive circuit according to claim 1, further includes：

Rectification unit, couples respectively with the driver element and the power supply switch unit；And

Detector unit, couples respectively with the rectification unit, the power supply switch unit and the driver element.

9. drive circuit according to claim 1, further includes：

Energy unit is let out, respectively with the power supply switch unit, the constant current unit and the driver element coupling Connect, and described letting out can unit and phase dimmer fit applications.

10. drive circuit according to claim 1, wherein the constant current unit have the first electric capacity, 4th impedor and the 5th impedor, the first end of first electric capacity connects respectively the power supply switching Second end of the diode of unit and the 4th impedor first end, the 4th impedor The second end connect the first end of the luminescence unit, the 5th impedor first end connection described the Second end of one electric capacity, its second end connects the second end of the luminescence unit.

11. drive circuits according to claim 10, wherein the constant current unit further has the One resistance, second resistance and transistor seconds, the first end of the first resistor connects respectively the 5th resistance Second end of the first end of anti-element and first electric capacity, its second end connects respectively the second resistance First end and the driver element, the second end of the second resistance connects the earth terminal, and described second Second end of transistor is respectively coupled to the driver element with the 3rd end.

12. drive circuits according to claim 11, wherein the constant current unit further has the Three resistance and the second electric capacity, the first end of second electric capacity connects the second end and the institute of the transistor seconds State driver element, the first end of the 3rd resistor connects respectively the 3rd end of the transistor seconds and described Driver element, its second end connects the earth terminal.

13. drive circuits according to claim 10, wherein the 4th impedor or the described 5th Impedor is magnetic bead or resistance.

14. drive circuits according to claim 1, it is applied to the light emitting diode of multipath reflection cover type Bulb.