Dial-up dimming LED drive circuit

Abstract

The utility model provides a dial-up dimming LED drive circuit, which comprises an input rectification circuit, a flyback circuit, a dial-up dimming circuit and an LED load circuit, a first terminal and a second terminal of the input rectification circuit are respectively used for connecting an anode and a cathode of an AC power supply, a third terminal and a fourth terminal of the input rectification circuit are respectively connected to the first terminal and the second terminal of the flyback circuit, and the first terminal and the second terminal of the flyback circuit are respectively connected with the anode and the cathode of the AC power supply. The second terminal, the third terminal and the fourth terminal of the flyback circuit are connected to the first terminal, the second terminal and the third terminal of the dial dimming circuit respectively, the first terminal and the second terminal of the LED load circuit are connected to the fifth terminal and the sixth terminal of the flyback circuit respectively, and the second terminal and the third terminal are used for being connected with the two ends of an LED load respectively. The fourth terminal of the input rectification circuit, the second terminal of the flyback circuit, and the first terminal of the dial dimming circuit are all connected to a circuit reference ground.

Description

Technical Field

[0001] The utility model relates to the field of semiconductors, and particularly to a DIP dimming LED drive circuit. Background Art

[0002] In a traditional DIP dimming LED drive circuit, dimming is achieved by using a DIP switch to control the resistance value of a current sensing resistor connected between the primary winding of a transformer and the circuit reference ground. This DIP dimming method has two drawbacks: 1) When the DIP switch hard-cuts the resistance value of the current sensing resistor, the current flowing through the DIP switch is relatively large, and the DIP contacts are prone to oxidation; 2) Since the DIP position is close to the wiring positions at both ends of the circuit board, the current loop of the DIP path is relatively large, and it is difficult to handle electromagnetic interference. Summary of the Utility Model

[0003] In view of one or more of the above problems, a DIP dimming LED drive circuit according to an embodiment of the present utility model is provided. Among them, by using a DIP switch to adjust the ratio of a voltage dividing resistor that divides the primary current representation voltage representing the current flowing through the primary winding of the transformer, the current flowing through the primary winding of the transformer is adjusted, thereby adjusting the output current flowing through the LED load and realizing DIP dimming. Since this DIP dimming method controls the primary current representation divided voltage generated by dividing the primary current representation voltage, there is no problem of contact oxidation, the power loop is not affected, and it does not affect electromagnetic interference.

[0004] The DIP dimming LED drive circuit according to an embodiment of the present utility model includes an input rectifier circuit, a flyback circuit, a DIP dimming circuit, and an LED load circuit. Among them: the first and second terminals of the input rectifier circuit are respectively used to connect to the positive and negative poles of an AC power supply, and the third and fourth terminals are respectively connected to the first and second terminals of the flyback circuit. The second, third, and fourth terminals of the flyback circuit are respectively connected to the first, second, and third terminals of the DIP dimming circuit, and the first and second terminals of the LED load circuit are respectively connected to the fifth and sixth terminals of the flyback circuit, and the second and third terminals are respectively used to connect to both ends of the LED load. Here, the fourth terminal of the input rectifier circuit, the second terminal of the flyback circuit, and the first terminal of the DIP dimming circuit are all connected to the circuit reference ground.

[0005] In some embodiments, the DIP dimming circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a first DIP switch, and a second DIP switch. Among them: the first resistor is connected between the first and second terminals of the DIP dimming circuit, the second resistor is connected between the second and third terminals of the DIP dimming circuit, the third resistor and the first DIP switch are connected in series between the first and third terminals of the DIP dimming circuit, and the fourth resistor and the second DIP switch are connected in series between the first and third terminals of the DIP dimming circuit.

[0006] In some embodiments, the flyback circuit includes a transformer and a switching transistor. Among them, two terminals of the secondary winding of the transformer are respectively used as the fifth and sixth terminals of the flyback circuit, and the switching transistor is connected between the primary winding of the transformer and the third terminal of the flyback circuit. Here, the switching transistor can be a GaN switching transistor. In addition, the flyback circuit further includes a control chip. The switching transistor is included in the control chip. The source and drain of the switching transistor are respectively connected to the switching transistor source pin and the switching transistor drain pin of the control chip, and the switching transistor source pin of the control chip is used as the third terminal of the flyback circuit.

[0007] In some embodiments, the LED load circuit includes a filter capacitor and a rectifier diode. The second terminal of the LED load circuit is grounded. The filter capacitor is connected between the second and third terminals of the LED load circuit, and the rectifier diode is connected between the first and third terminals of the LED load circuit. Description of the Drawings

[0008] The present invention can be better understood from the following description of the specific embodiments in conjunction with the drawings, where:

[0009] Figure 1 A schematic structural diagram of a DIP dimming LED driver circuit according to an embodiment of the present invention is shown.

[0010] Figure 2 Shown is Figure 1 A schematic diagram showing an example of the pin layout and internal logic structure of the control chip U shown. Detailed Embodiments

[0011] The features and exemplary embodiments of various aspects of the present invention will be described in detail below. In the following detailed description, many specific details are set forth in order to provide a comprehensive understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention can be practiced without some of these specific details. The following description of the embodiments is only intended to provide a better understanding of the present invention by showing examples of the present invention. The present invention is in no way limited to any specific configuration set forth below, but covers any modification, replacement, and improvement of elements and components without departing from the spirit of the present invention. Well-known structures and techniques are not shown in the drawings and the following description so as to avoid unnecessarily obscuring the present invention. In addition, it should be noted that the term "A is connected to B" used here can mean "A is directly connected to B" or "A is indirectly connected to B via one or more other elements".

[0012] In view of one or more problems existing in traditional DIP dimming LED driver circuits, a DIP dimming LED driver circuit according to an embodiment of the present invention is proposed. Among them, by adjusting the ratio of the voltage-dividing resistors that divide the primary current representation voltage representing the current flowing through the primary winding of the transformer through DIP switches, the current flowing through the primary winding of the transformer is adjusted, so as to adjust the output current flowing through the LED load and achieve DIP dimming. This DIP dimming method controls the primary current representation voltage division generated by dividing the primary current representation voltage, has no problem of contact oxidation, the power loop is not affected, and it will not affect electromagnetic interference.

[0013] Figure 1 The structural schematic diagram of a DIP dimming LED driver circuit according to an embodiment of the present invention is shown. As Figure 1 shown, the DIP dimming LED driver circuit according to an embodiment of the present invention includes an input rectifier circuit 102, a flyback circuit 104, a DIP dimming circuit 106, and an LED load circuit 108, where: the first and second terminals of the input rectifier circuit 102 are respectively used to connect to the positive and negative poles of the AC power supply, and the third and fourth terminals are respectively connected to the first and second terminals of the flyback circuit 104; the second, third, and fourth terminals of the flyback circuit 104 are respectively connected to the first, second, and third terminals of the DIP dimming circuit 106; the first and second terminals of the LED load circuit 108 are respectively connected to the fifth and sixth terminals of the flyback circuit 104, and the second and third terminals are respectively used to connect to both ends of the LED load. Here, the fourth terminal of the input rectifier circuit 102, the second terminal of the flyback circuit 104, and the first terminal of the DIP dimming circuit 106 are all connected to the circuit reference ground.

[0014] As Figure 1 shown, in some embodiments, the input rectifier circuit 102 includes a fuse resistor F1, rectifier diodes D1, D2, D3, D4, and a filter capacitor C1.

[0015] As Figure 1 shown, in some embodiments, the flyback circuit 104 includes a transformer T1 and a switching transistor M (not shown in the figure). Among them, the two terminals of the secondary winding Ns of the transformer T1 are respectively used as the fifth and sixth terminals of the flyback circuit 104, and the switching transistor M is connected between the primary winding Np of the transformer T1 and the third terminal of the flyback circuit 104. Here, the switching transistor can be implemented as, for example, a GaN switching transistor. In addition, the flyback circuit 104 further includes a control chip U, the switching transistor M is included in the control chip U, the source and drain of the switching transistor M are respectively connected to the switching transistor source pin Source and the switching transistor drain pin Drain of the control chip U, and the switching transistor source pin Source of the control chip U is used as the third terminal of the flyback circuit 104.

[0016] As Figure 1 shown, in some embodiments, the DIP switch dimming circuit 106 includes a current sensing resistor R2, an upper bias resistor R3, lower bias resistors R4 and R5, and DIP switches SW1 and SW2. Among them, the current sensing resistor R2 is connected between the first and second terminals of the DIP switch dimming circuit 106, the upper bias resistor R3 is connected between the second and third terminals of the DIP switch dimming circuit 106, the lower bias resistor R4 and the DIP switch SW1 are connected in series between the first and third terminals of the DIP switch dimming circuit 106, and the lower bias resistor R5 and the DIP switch SW2 are connected in series between the first and third terminals of the DIP switch dimming circuit 106. When the DIP switch SW1 is in the on state and the DIP switch SW2 is in the off state, the lower bias resistor R4 is connected between the current sensing pin CS of the control chip U (i.e., the fourth terminal of the flyback circuit 104) and the circuit reference ground; when the DIP switch SW2 is in the on state and the DIP switch SW1 is in the off state, the lower bias resistor R5 is connected between the current sensing pin CS of the control chip U and the circuit reference ground; when the DIP switches SW1 and SW2 are both in the on state, the lower bias resistors R4 and R5 are connected in parallel between the current sensing pin CS of the control chip U and the circuit reference ground; when the DIP switches SW1 and SW2 are both in the off state, no lower bias resistor is connected between the current sensing pin CS of the control chip U and the circuit reference ground.

[0017] As Figure 1 shown, in some embodiments, the LED load circuit 108 includes a rectifier diode D5 and a filter capacitor EC2. Among them, the second terminal of the LED load circuit 108 is grounded, the filter capacitor EC2 is connected between the second and third terminals of the LED load circuit 108, and the rectifier diode D5 is connected between the first and third terminals of the LED load circuit 108.

[0018] Figure 2 Shows Figure 1 a schematic diagram of an example of the pin layout and internal logic structure of the control chip U shown. As Figure 2 shown, the control chip U includes a power input pin VDD, a high-voltage power supply pin HV, an output overvoltage protection setting pin OVP, a current sensing pin CS, a power ground pin GND, a switch source pin Source, and a switch drain pin Drain, and includes the following functional modules:

[0019] · A high-voltage power supply module 202, connected to the high-voltage power supply pin HV, for receiving a chip startup voltage (i.e., the rectified and filtered voltage Vin generated by rectifying and filtering the AC input voltage) via the high-voltage power supply pin HV.

[0020] · An undervoltage protection module 204, connected to the power input pin VDD, is used to control the switching transistor M to change from the on state to the off state when the chip supply voltage VDD at the power input pin VDD is less than the undervoltage protection voltage of the control chip U.

[0021] · An output overvoltage protection setting module 206, connected to the output overvoltage protection setting pin OVP, is used to set the maximum value of the system output voltage V by setting a fixed ratio between the output overvoltage protection voltage Vovp generated by setting a fixed current flowing through the output overvoltage setting resistor R1 and the voltage difference VD, where the voltage difference VD is the voltage difference between the plateau voltage Vdrain generated at the drain of the switching transistor M when the secondary winding Ns of the transformer T1 demagnetizes and the rectified and filtered voltage Vin (i.e., the voltage reflected from the secondary winding Ns of the transformer T1 to the primary winding Np during the demagnetization of the secondary winding Ns of the transformer T1). In other words, the voltage difference VD is superimposed on the rectified and filtered Vin to obtain the plateau voltage Vdrain. For example, when the resistance value of the output overvoltage setting resistor R1 increases, the output overvoltage protection voltage Vovp increases, the voltage difference VD increases, and the maximum value of the system output voltage V LED becomes larger; conversely, when the resistance value of the output overvoltage setting resistor R1 decreases, the output overvoltage protection voltage Vovp decreases, the voltage difference VD decreases, and the maximum value of the system output voltage V LED becomes smaller. LED

[0022] · A constant current control module 208, connected to the current sensing pin CS, is used to control the output current flowing through the LED load to remain constant based on the primary current representative divided voltage Vcs generated by dividing the primary current representative voltage Vsource representing the current flowing through the primary winding Np of the transformer T1.

[0023] · A logic control module 210 is used to generate a switching transistor control signal for controlling the on and off of the switching transistor M by performing a logical operation on the relevant signals from the output overvoltage protection setting module 206 and the constant current control module 208.

[0024] · A driving module 212 is used to drive the switching transistor M to switch between the on state and the off state based on the switching transistor control signal.

[0025] Such as Figure 1 and Figure 2As shown, the working principle of the DIP switch dimming LED driver circuit 100 for DIP switch dimming is as follows: The control chip U is connected to the current sensing resistor R2 via the source terminal Source of the switching transistor to detect the primary current representative voltage Vsource that characterizes the current flowing through the primary winding Np of the transformer T1; the control chip U is connected to the connection point between the upper bias resistor R3 and the lower bias resistors R4 and R5 via the current sensing pin CS to detect the primary current representative divided voltage Vcs generated by dividing the primary current representative voltage Vsource by the upper bias resistor R3 and the lower bias resistors R4 and / or R5; the control chip U adjusts the ratio of the upper bias resistor R3 to the lower bias resistors R4 and / or R5 to adjust the primary current representative voltage Vsource, thereby changing the output current flowing through the LED load and realizing DIP switch dimming. For example, when both the DIP switches SW1 and SW2 are in the off state, Vcs = Vsource, and the peak current Ip1 flowing through the primary winding Np of the transformer T1 is Ip1 = Vcs / R2; when the DIP switch SW1 is in the on state and the DIP switch SW2 is in the off state or when the DIP switch SW1 is in the off state and the DIP switch SW2 is in the on state, Vsource = Vcs + V_R3 (V_R3 is the voltage across the upper bias resistor R3), and the peak current Ip2 flowing through the primary winding Np of the transformer T1 is Ip2 = (Vcs + V_R3) / R2. Since Ip2 > Ip1, the output current flowing through the LED load becomes larger; when both the DIP switches SW1 and SW2 are in the on state, the resistance value generated by the parallel connection of the lower bias resistors R4 and R5 is smaller than that of the lower bias resistor R4 or R5, the voltage ratio of the upper bias resistor R3 increases, the voltage V_R3 across the upper bias resistor R3 further increases, and the peak current flowing through the primary winding Np of the transformer T1 further increases. Through the above DIP switch method, DIP switch dimming can be realized.

[0026] As Figure 1 and Figure 2As shown, the operation process of the LED driving circuit 100 includes: during the period when the switching transistor M is in the conducting state, the primary winding Np of the transformer T1 stores energy, and the current Ip flowing through the primary winding Np of the transformer T1 continuously increases. The constant current control module 208 detects the primary current representative divided voltage Vcs via the current sensing pin CS, and controls the switching transistor M to change from the conducting state to the off state when the primary current representative divided voltage Vcs rises to the internally set threshold voltage comp. During the period when the switching transistor M is in the off state, the energy stored in the primary winding Np of the transformer T1 is discharged to the secondary winding Ns of the transformer T1. After the energy stored in the primary winding Np of the transformer T1 is completely discharged, the inductor of the primary winding Np of the transformer T1 resonates with the parasitic capacitance between the drain and source of the switching transistor M, and the constant current control module 208 controls the switching transistor M to change from the off state to the conducting state at the resonance valley. The logic control module 210 detects the voltage difference VD between the plateau voltage Vdrain generated at the drain of the switching transistor M when the secondary winding Ns of the transformer T1 demagnetizes and the rectified and filtered voltage Vin, and sets the system output voltage V based on it. LED maximum value. When power is initially applied, the system output voltage V LED rises from 0. At this time, the voltage difference between Vdrain and Vin is too low, and the control chip U defaults the system to the open-loop state. At this time, the peak voltage of the primary current representative divided voltage Vcs is fixed at 1 / 2 times the overcurrent protection voltage, and the system output voltage V LED rises rapidly. When the system output voltage V LED is high enough, the voltage difference VD between Vdrain and Vin reaches the set closed-loop threshold, and the logic control module 210 determines that the system enters the closed-loop state. At this time, N*V LED *Tdem = Ip_pk*LP, where Ip_pk represents the peak current flowing through the primary winding Np of the transformer T1, Tdem represents the duration of the demagnetization state of the secondary winding Ns of the transformer T1 (i.e., the demagnetization time), LP represents the inductance value of the primary winding Np of the transformer T1, and N represents the turns ratio of the primary winding Np to the secondary winding Ns of the transformer T1. The output current Io flowing through the LED load is Io = 1 / 2*N*Ip_pk*(Ton + Tdem) / Tsw, where Tsw represents the duration of one switching cycle of the switching transistor M. The constant current control module 208 controls Vsource_pk*(Ton + Tdem) / Tsw = Vref, where Vsource_pk represents the peak voltage of the primary current representative voltage Vsource, and Vref is the internally set reference voltage. Therefore, Io = 1 / 2*N*Vref / R2, and the system realizes the constant current function.

[0027] The features, structures, or characteristics described above can be combined in one or more embodiments in any suitable manner. In the above description, numerous specific details are provided to give a thorough understanding of the embodiments of the present utility model. However, those skilled in the art will realize that the technical solutions of the present utility model can be practiced without one or more of the specific details, or other methods, components, materials, etc. can be adopted. In other cases, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring the main technical concept of the present utility model.

Claims

1. A dial-code dimming LED driving circuit, characterized in that: It includes input rectification circuit, flyback circuit, dial dimming circuit, and LED load circuit, among which: The first and second terminals of the input rectifier circuit are respectively used to connect the positive electrode and the negative electrode of the AC power supply, and the third and fourth terminals are respectively connected to the first and second terminals of the flyback circuit; The second, third, and fourth terminals of the flyback circuit are respectively connected to the first, second, and third terminals of the dial dimming circuit; and The first and second terminals of the LED load circuit are respectively connected to the fifth and sixth terminals of the flyback circuit, and the second and third terminals are respectively used to connect two ends of the LED load.

2. The dial-code dimming LED driving circuit according to claim 1, characterized in that: The fourth terminal of the input rectifier circuit, the second terminal of the flyback circuit, and the first terminal of the dial dimming circuit are all connected to a circuit reference ground.

3. The dial-code dimming LED driving circuit according to claim 2, characterized in that: The dip-code dimming circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a first dip-code switch, and a second dip-code switch, wherein: The first resistor is connected between the first and second terminals of the dial dimming circuit; The second resistor is connected between the second and third terminals of the dial dimming circuit; The third resistor and the first dip switch are connected in series between the first and third terminals of the dip dimming circuit; and The fourth resistor and the second dip switch are connected in series between the first and third terminals of the dip dimming circuit.

4. The dial-code dimming LED driving circuit according to claim 2, characterized in that: The flyback circuit includes a transformer and a switch tube, wherein: The two terminals of the secondary winding of the transformer are used as the fifth and sixth terminals of the flyback circuit respectively; and The switch tube is connected between the primary winding of the transformer and the third terminal of the flyback circuit.

5. The dial-code dimming LED driving circuit according to claim 4, characterized in that: The switch tube is a GaN switch tube.

6. The dial-code dimming LED driving circuit according to claim 4, characterized in that: The flyback circuit also includes a control chip, and the switch tube is included in the control chip.

7. The dial-code dimming LED driving circuit according to claim 6, characterized in that: The source and drain of the switch tube are respectively connected to the switch tube source pin and the switch tube drain pin of the control chip, and the switch tube source pin of the control chip is used as the third terminal of the flyback circuit.

8. The dial-code dimming LED driving circuit according to claim 1, characterized in that: The LED load circuit includes a filter capacitor and a rectifier diode.

9. The dial-code dimming LED driving circuit according to claim 8, characterized in that: The second terminal of the LED load circuit is grounded, and the filter capacitor is connected between the second and third terminals of the LED load circuit.

10. The dial-code dimming LED driving circuit according to claim 8, characterized in that: The rectifying diode is connected between the first and third terminals of the LED load circuit.

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