Novel LED drive circuit with multi-mode current sampling

Abstract

The invention relates to the field of electronic circuits, and provides a novel LED drive circuit with multi-mode current sampling, which comprises a BUCK circuit, a switch switching circuit, a multi-mode sampling module, a sampling comparison circuit and a control module, and is characterized in that the input end of the BUCK circuit is connected with an input power supply, the output end of the BUCK circuit is connected with an LED lamp, and the controlled end of the BUCK circuit is connected with the output end of the control module; the multi-mode sampling module is connected with a current sampling end of the BUCK circuit through the switch switching circuit, and the switch switching circuit is used for switching when the working mode of the BUCK circuit is changed, so that the multi-mode sampling module adopts corresponding sampling modes in different working modes. The output end of the sampling comparison circuit is connected with the input end of the sampling comparison circuit, and the output end of the sampling comparison circuit is connected with the input end of the control module; according to the invention, the average inductance current in the BUCK circuit can be accurately sampled in a continuous mode, a critical mode and a discontinuous mode.

Description

Technical Field

[0001] The present invention relates to the field of electronic circuits, and in particular to a novel LED driving circuit with multi-mode current sampling. Background Art

[0002] In LED lighting applications, it is sometimes necessary to connect multiple output loads to a common anode in order to reduce the number of wiring terminals, such as applications with multiple LED loads with different output colors. Figure 2 and 3 As shown in the figure, a current sampling resistor is connected in series with the inductor loop of the BUCK circuit, which is a traditional method for collecting output current for control. However, its disadvantage is that the voltage at the midpoint of the BUCK changes rapidly, which makes the current sampling easily disturbed, resulting in poor control accuracy and high voltage resistance requirements for the IC. In some applications, the BUCK only works in critical mode, and the peak value of the MOS tube current is collected by a resistor to control the output current; or the BUCK only works in continuous mode, and the current of the MOS tube is collected at the middle moment of the MOS tube conduction time to control the output current or the peak-peak value is collected to control the output current.

[0003] In the continuous mode BUCK circuit, the ripple current flowing through the output filter capacitor is small; in the critical mode BUCK circuit, the ripple current flowing through the output filter capacitor is large; in the discontinuous mode BUCK circuit, the ripple current flowing through the output filter capacitor is the largest. The life of the electrolytic capacitor is related to the ripple current flowing through it. The larger the current, the shorter the life. In addition, for the continuous mode, the operating frequency is higher and the switching loss is large; for the critical mode and discontinuous mode, the operating frequency is lower and the switching loss is smaller. Since LED lighting often requires dimming control, the size of the output current is variable. Therefore, when the current is large, it is hoped that the BUCK can work in the continuous mode, so that the ripple current flowing through the output filter capacitor is small, which prolongs the life of the capacitor. At the same time, due to the large output current amplitude, the operating frequency will not be very high; when the current is small, it is hoped that the BUCK can work in the critical or discontinuous mode. Due to the small output current, the BUCK operating frequency will not be too low.

[0004] It can be seen that when in use, according to needs, the BUCK circuit of LED lighting often needs to switch between continuous, critical or intermittent modes, and the current of each mode needs to be collected, but the existing circuit cannot simply and effectively process the current signal of the intermittent mode. Summary of the invention

[0005] The problem solved by the present invention is how to provide a simple current signal processing method so that the LED driver can accurately sample the average inductor current in the BUCK circuit in the continuous, critical and discontinuous modes.

[0006] In order to solve the above problems, the present invention provides a novel LED driving circuit with multi-mode current sampling, comprising: a BUCK circuit, a switch switching circuit, a multi-mode sampling module, a sampling comparison circuit and a control module, wherein the input end of the BUCK circuit is connected to an input power supply, the output end is connected to an LED lamp, and the controlled end is connected to the output end of the control module. The multi-mode sampling module is connected to the current sampling end of the BUCK circuit via the switch switching circuit. The switch switching circuit is used to perform switch switching when the working mode of the BUCK circuit changes, so that the multi-mode sampling module adopts a corresponding sampling method under different working modes. The working modes include continuous, critical and intermittent modes. The output end of the sampling comparison circuit is connected to the input end of the sampling comparison circuit, and the output end of the sampling comparison circuit is connected to the input end of the control module.

[0007] Furthermore, the BUCK circuit includes a first MOS tube, a first diode, a first inductor, a first resistor and a first capacitor. The gate of the first MOS tube is connected to the output end of the control module to control the first inductor to charge or discharge through the first diode and the first capacitor according to the signal of the control module. The first resistor is a current sampling resistor, and the first resistor is connected in series with the drain and source of the first MOS tube.

[0008] Furthermore, the BUCK circuit also includes a second capacitor, which is connected to the input power supply and is used to filter the input power supply.

[0009] Further, the multi-mode sampling module includes a first sampling circuit and a second sampling circuit, the switch switching circuit includes a first switch, a second switch, a third switch, a second resistor, a first voltage regulator and a first NOT gate, the controlled end of the first switch is connected to the output end of the control module, the input end is connected to the first resistor, the output end is connected to the input end of the second switch through the first sampling circuit, the output ends of the second switch and the third switch are connected to the input end of the second sampling circuit, the output end of the second sampling circuit is connected to the input end of the sampling comparison circuit, the input end of the third switch is grounded, the first end of the first voltage regulator is grounded, and the second end is respectively connected to the controlled end of the second switch and the input end of the first NOT gate, the output end of the first NOT gate is connected to the controlled end of the third switch, the first end of the second resistor is connected to the auxiliary winding of the first inductor, and the second end is connected to the second end of the first voltage regulator.

[0010] Furthermore, the switch switching circuit also includes a second diode and a third resistor, the anode of the second diode is connected to the output end of the control module, and the cathode is connected to the second end of the first voltage regulator tube through the third resistor.

[0011] Furthermore, the first sampling circuit includes a fourth resistor, a third capacitor and a first follower, the first end of the fourth resistor is connected to the output end of the first switch, the second end is connected to the input end of the first follower, the first end of the third capacitor is connected to the second end of the fourth resistor, the second end is grounded, and the output end of the first follower is connected to the input end of the second switch.

[0012] Furthermore, the second sampling circuit includes a fifth resistor and a fourth capacitor, a first end of the fifth resistor is connected to the output end of the second switch, and a second end is connected to the sampling comparison circuit, a first end of the fourth capacitor is connected to the second end of the fifth resistor, and a second end is grounded.

[0013] Furthermore, in the BUCK circuit, the source of the first MOS tube is grounded via the first resistor, the drain is connected to the anode of the first diode, the cathode of the first diode is connected to the input power supply, the cathode of the first diode is also respectively connected to the first end of the first capacitor and the positive electrode of the LED lamp, the first end of the first inductor is connected to the drain of the first MOS tube, and the second end is respectively connected to the second end of the first capacitor and the negative electrode of the LED lamp.

[0014] Furthermore, in the BUCK circuit, the drain of the first MOS tube is connected to the input power supply, the source is respectively connected to the first end of the first inductor and the cathode of the first diode, the anode of the first diode is grounded via the first resistor, the second end of the first inductor is respectively connected to the first end of the first capacitor and the positive electrode of the LED lamp, and the second end of the first capacitor and the negative electrode of the LED lamp are connected to the anode of the first diode.

[0015] Furthermore, the sampling and comparison circuit includes a first comparator, a positive input terminal of the first comparator is connected to a reference voltage, a negative input terminal is connected to an output terminal of the multi-mode sampling module, and an output terminal is connected to an input terminal of the control module.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] By switching the three analog switches in the switch switching circuit when the BUCK circuit works in different modes, the multi-mode sampling module adopts the corresponding sampling circuit structure and sampling method in the continuous, critical and discontinuous modes, so as to accurately sample the average inductor current in the BUCK circuit in the continuous, critical and discontinuous modes. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the overall principle structure of an embodiment of the present invention;

[0019] Figure 2 This is one of the schematic diagrams of the current sampling principle of the BUCK circuit of the prior art of the present invention;

[0020] Figure 3 This is the second schematic diagram of the current sampling principle of the BUCK circuit of the prior art of the present invention;

[0021] Figure 4 This is one of the current waveform schematic diagrams of the continuous mode of the prior art of the present invention;

[0022] Figure 5 This is the second schematic diagram of the current waveform in the continuous mode of the prior art of the present invention;

[0023] Figure 6 A schematic diagram of a current waveform in a critical mode of the prior art of the present invention;

[0024] Figure 7 One of the overall circuit principle diagrams of an embodiment of the present invention;

[0025] Figure 8 is a schematic diagram of a current waveform in a continuous mode according to an embodiment of the present invention;

[0026] Fig. 9 is a schematic diagram of a current waveform in a critical mode of an embodiment of the present invention;

[0027] Fig.10 is a schematic diagram of a current waveform in a discontinuous mode according to an embodiment of the present invention;

[0028] Fig.11 This is the second overall circuit schematic diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0029] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0030] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] In the description of this specification, the description with reference to the terms "embodiment", "one embodiment" and "one implementation" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or implementation are included in at least one embodiment or implementation of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or implementation. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or implementations in a suitable manner.

[0032] like Figure 1 As shown, the present invention provides a novel LED driving circuit with multi-mode current sampling, including: a BUCK circuit, a switch switching circuit, a multi-mode sampling module, a sampling comparison circuit and a control module, wherein the input end of the BUCK circuit is connected to an input power supply, the output end is connected to an LED lamp, and the controlled end is connected to the output end of the control module. The multi-mode sampling module is connected to the current sampling end of the BUCK circuit via the switch switching circuit. The switch switching circuit is used to perform switch switching when the working mode of the BUCK circuit changes, so that the multi-mode sampling module adopts a corresponding sampling method in different working modes. The working modes include continuous, critical and intermittent modes. The output end of the sampling comparison circuit is connected to the input end of the sampling comparison circuit, and the output end of the sampling comparison circuit is connected to the input end of the control module.

[0033] It should be noted that in the prior art, the solution of connecting the inductor circuit in series with the current sampling resistor is generally adopted. Figure 2 , or use the solution of connecting a current sampling resistor in series with the MOS tube, which can be referred to Figure 3 ; When the solution of connecting the inductor circuit in series with the current sampling resistor is adopted, such as Figure 4 As shown in the figure, for the continuous mode buck circuit, the current (i1) when the MOS tube is turned on and the current (i2) passing through the inductor when the MOS tube is turned off can be sampled, and the average current flowing through the inductor is (i1+i2) / 2. When the solution of connecting the current sampling resistor in series with the MOS tube is adopted, when the buck circuit works in the continuous mode, Figure 5 As shown, the current at the midpoint of the MOS conduction time can be measured. This current value is the average value of the inductor current. When the BUCK circuit works in the critical mode, such as Figure 6 As shown, the average current passing through the inductor is 1 / 2 of the peak current. The advantage of connecting the current sampling resistor in series with the MOS tube is that it shares a common ground with the control circuit, and the current signal can be conveniently processed by the control circuit. However, the existing technical solutions cannot simply and effectively process the current signal in the discontinuous mode.

[0034] In view of the above shortcomings, in this embodiment, the BUCK circuit adopts a current sampling method of a current sampling resistor connected in series on a MOS tube. At the same time, a switch switching circuit and a multi-mode sampling module are provided. When the BUCK circuit works in different modes, the switch switching circuit is switched so that in the continuous, critical and discontinuous modes, the multi-mode sampling module adopts a corresponding sampling circuit structure and sampling method to achieve accurate sampling of the average inductor current in the BUCK circuit in the continuous, critical and discontinuous modes.

[0035] In one embodiment of the present invention, Figure 7 As shown, the LED driving circuit includes a BUCK circuit, a switch switching circuit, a multi-mode sampling module, a sampling comparison circuit and a control module, wherein:

[0036] U6 is a control module, which is used to receive the sampled current information and send out a control signal. The sampling comparison circuit adopts a first comparator U7. The positive input terminal of the first comparator U7 is connected to the reference voltage Vref, and the negative input terminal is connected to the output terminal of the multi-mode sampling module. That is, the first comparator U7 receives the collected current sampling signal, compares the current sampling signal with the reference voltage Vref, and transmits it to the control module U6 through its output terminal after processing, so that the control module U6 can accurately obtain the current sampling information.

[0037] The BUCK circuit includes a first MOS tube Q1, a first diode D1, a first inductor T1, a first resistor R1, a first capacitor C2, and a second capacitor C1. The gate of the first MOS tube Q1 is connected to the output end of the control module U6, so as to control the first inductor T1' to charge according to the signal of the control module U6, or to make the first inductor T1' discharge through the first diode D1 and the first capacitor C2. By changing the charging and discharging time and state of the first inductor T1, the power output by the BUCK circuit can be controlled. The first resistor R1 is a current sampling resistor. The first resistor R1 is connected in series with the drain and source of the first MOS tube Q1 to collect the current passing through the MOS tube. The second capacitor C1 is connected to the input power supply for filtering the input power supply.

[0038] The multi-mode sampling module includes a first sampling circuit and a second sampling circuit. The switch switching circuit includes a first switch U1, a second switch U3, a third switch U4, a second resistor R5, a first voltage regulator D3, a first NOT gate U5, a second diode D2 and a third resistor R4. The controlled end of the first switch U1 is connected to the output end of the control module U6, the input end is connected to the first resistor R1, the output end is connected to the input end of the second switch U3 through the first sampling circuit, the output ends of the second switch U3 and the third switch U4 are connected to the input end of the second sampling circuit, the output end of the second sampling circuit is connected to the input end of the sampling comparison circuit, the input end of the third switch U4 is grounded, the first end of the first voltage regulator D3 is grounded, and the second end is respectively connected to the controlled end of the second switch U3 and the input end of the first NOT gate U5, the output end of the first NOT gate U5 is connected to the third switch The controlled end of U4, the first end of the second resistor R5 is connected to the auxiliary winding of the first inductor T1, the second end is connected to the second end of the first voltage regulator D3, the anode of the second diode D2 is connected to the output end of the control module U6, and the cathode is connected to the second end of the first voltage regulator D3 through the third resistor R4, wherein the first switch U1, the second switch U3, and the third switch U4 are analog switches, when powered on, the first switch U1 will be turned on, when the auxiliary winding of the first inductor T1 has current on the first inductor T1, a switch voltage is provided through the second resistor R5, and the first voltage regulator D3 stabilizes the switch voltage, ensuring the control accuracy of the switch, due to the existence of the first NOT gate U5, the switch signals received by the second switch U3 and the third switch U4 are opposite, and only one will be turned on at the same time, and the different sampling circuits are realized when switching;

[0039] The first sampling circuit includes a fourth resistor R2, a third capacitor C3 and a first follower U2, wherein a first end of the fourth resistor R2 is connected to an output end of the first switch U1, and a second end is connected to an input end of the first follower U2, a first end of the third capacitor C3 is connected to a second end of the fourth resistor R2, and a second end is grounded, and an output end of the first follower U2 is connected to an input end of the second switch U3; the second sampling circuit includes a fifth resistor R3 and a fourth capacitor C4, a first end of the fifth resistor R3 is connected to an output end of the second switch U3, and a second end is connected to a first comparator U7, a first end of the fourth capacitor R2 is connected to a second end of the fifth resistor R5, and a second end is grounded.

[0040] In the above circuit, the specific scheme and principle of current sampling in CCM, CRM and DCM modes are as follows:

[0041] like Figure 7As shown, the voltage value of the third capacitor C3 is the average voltage on the first resistor R1 during the conduction period of the first MOS tube Q1, and this voltage is connected to the RC filter circuit composed of the fifth resistor R3 and the fourth capacitor C4 through the analog switch. During the conduction period of the first MOS tube Q1 or the first diode D1, the second switch U3 is turned on and the third switch U4 is turned off; during the period when the first MOS tube Q1 and the first diode D1 are not turned on, the second switch U3 is turned off and the third switch U4 is turned on. Among them, the discontinuous mode corresponds to the non-conduction of the first MOS tube Q1 and the first diode D1, and the continuous or critical mode corresponds to the continuous mode or the critical mode when one of the first MOS tube Q1 and the first diode D1 is turned on at any time;

[0042] For the continuous mode buck circuit, the average current flowing through the first MOS tube Q1 during the conduction period is the average current of the buck inductor, that is, the average output current of the buck circuit, such as Figure 8 As mentioned above, the voltage value of the third capacitor C3 represents the average current flowing through the MOS tube during the conduction period of the first MOS tube Q1. In the continuous mode, the second switch U3 is always on and the third switch U4 is kept off, so the voltage of the fourth capacitor C4 is equal to the voltage of the third capacitor C3, and the voltage of the fourth capacitor C4 represents the output current of the BUCK;

[0043] In continuous mode, the current waveform of the BUCK circuit is as follows: Figure 8 As shown;

[0044] The current waveform of the BUCK circuit in critical mode is as follows: Fig. 9 As shown in FIG. 1 , for the critical mode BUCK circuit, the average current flowing through the first MOS tube Q1 during the conduction period is the average current of the BUCK inductor, that is, the output average current of the BUCK circuit, as shown in FIG. Fig. 9 As shown, the voltage value of the third capacitor C3 represents the average current flowing through the MOS tube during the conduction period of the first MOS tube Q1 in the same reason as the continuous mode. In the critical mode, the second switch U3 is always on and the third switch U4 remains off, so the voltage of the fourth capacitor C4 is equal to the voltage of the third capacitor C3, and the voltage of the fourth capacitor C4 represents the output current of the BUCK.

[0045] The current waveform of the BUCK circuit in discontinuous mode is as follows: Fig.10As shown, the peak current of the first MOS tube Q1 can be combined with three times t1, t2, and t3 to calculate the output current of the BUCK, where t1 is the time period when the first MOS tube Q1 is turned on, t2 is the time period when the first diode D1 is turned on, and t3 is the time period when both the first MOS tube Q1 and the first diode D1 are not turned on. During t1 and t2, the average current is 1 / 2 of the peak current, represented by ipk, and during t3, the current is zero. Therefore, the total average current calculation formula is: (ipk / 2)*(t1+t2) / (t1+t2+t3). In this formula, when t3=0, it is the continuous mode and critical mode;

[0046] In one embodiment of the present invention, in the BUCK circuit, the MOS tube may be connected to the high end, and a current sampling resistor may be connected in series between the low end diode and the ground, such as Fig.11 As shown, in the BUCK circuit, the drain of the first MOS tube Q1 is connected to the input power supply, the source is respectively connected to the first end of the first inductor L1 and the cathode of the first diode D1, the anode of the first diode D1 is grounded via the first resistor R1, the second end of the first inductor T1 is respectively connected to the first end of the first capacitor C2 and the positive electrode of the LED lamp, and the second end of the first capacitor C2 and the negative electrode of the LED lamp are connected to the anode of the first diode D1.

[0047] Although the disclosure is disclosed as above, the protection scope of the disclosure is not limited thereto. Those skilled in the art may make various changes and modifications without departing from the spirit and scope of the disclosure, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A novel LED driving circuit with multi-mode current sampling, characterized in that: include: A BUCK circuit, a switch switching circuit, a multi-mode sampling module, a sampling comparison circuit and a control module, wherein the input end of the BUCK circuit is connected to an input power supply, the output end is connected to an LED lamp, the controlled end is connected to the output end of the control module, the multi-mode sampling module is connected to the current sampling end of the BUCK circuit via the switch switching circuit, the switch switching circuit is used to perform switch switching when the working mode of the BUCK circuit changes, so that the multi-mode sampling module adopts a corresponding sampling method under different working modes, the working modes include continuous, critical and intermittent modes, the output end of the sampling comparison circuit is connected to the input end of the sampling comparison circuit, and the output end of the sampling comparison circuit is connected to the input end of the control module.

2. The novel LED driving circuit with multi-mode current sampling according to claim 1, characterized in that: The BUCK circuit includes a first MOS tube, a first diode, a first inductor, a first resistor and a first capacitor. The gate of the first MOS tube is connected to the output end of the control module to control the first inductor to charge or discharge through the first diode and the first capacitor according to a signal of the control module. The first resistor is a current sampling resistor and is connected in series with the drain and source of the first MOS tube.

3. The novel LED driving circuit with multi-mode current sampling according to claim 2, characterized in that: The BUCK circuit further includes a second capacitor connected to the input power supply and configured to filter the input power supply.

4. The novel LED driving circuit with multi-mode current sampling according to claim 3, characterized in that: The multi-mode sampling module includes a first sampling circuit and a second sampling circuit. The switch switching circuit includes a first switch, a second switch, a third switch, a second resistor, a first voltage regulator and a first NOT gate. The controlled end of the first switch is connected to the output end of the control module, the input end is connected to the first resistor, and the output end is connected to the input end of the second switch through the first sampling circuit. The output ends of the second switch and the third switch are connected to the input end of the second sampling circuit. The output end of the second sampling circuit is connected to the input end of the sampling comparison circuit. The input end of the third switch is grounded. The first end of the first voltage regulator is grounded, and the second end is respectively connected to the controlled end of the second switch and the input end of the first NOT gate. The output end of the first NOT gate is connected to the controlled end of the third switch. The first end of the second resistor is connected to the auxiliary winding of the first inductor, and the second end is connected to the second end of the first voltage regulator.

5. The novel LED driving circuit with multi-mode current sampling according to claim 4, characterized in that: The switch switching circuit also includes a second diode and a third resistor. The anode of the second diode is connected to the output end of the control module, and the cathode is connected to the second end of the first voltage regulator tube through the third resistor.

6. The novel LED driving circuit with multi-mode current sampling according to claim 5, characterized in that: The first sampling circuit includes a fourth resistor, a third capacitor and a first follower, the first end of the fourth resistor is connected to the output end of the first switch, the second end is connected to the input end of the first follower, the first end of the third capacitor is connected to the second end of the fourth resistor, the second end is grounded, and the output end of the first follower is connected to the input end of the second switch.

7. The novel LED driving circuit with multi-mode current sampling according to claim 6, characterized in that: The second sampling circuit includes a fifth resistor and a fourth capacitor. The first end of the fifth resistor is connected to the output end of the second switch, and the second end is connected to the sampling comparison circuit. The first end of the fourth capacitor is connected to the second end of the fifth resistor, and the second end is grounded.

8. The novel LED driving circuit with multi-mode current sampling according to claim 2, characterized in that: In the BUCK circuit, the source of the first MOS tube is grounded via the first resistor, the drain is connected to the anode of the first diode, the cathode of the first diode is connected to the input power supply, the cathode of the first diode is also connected to the first end of the first capacitor and the positive electrode of the LED lamp respectively, the first end of the first inductor is connected to the drain of the first MOS tube, and the second end is connected to the second end of the first capacitor and the negative electrode of the LED lamp respectively.

9. The novel LED driving circuit with multi-mode current sampling according to claim 2, characterized in that: In the BUCK circuit, the drain of the first MOS tube is connected to the input power supply, the source is respectively connected to the first end of the first inductor and the cathode of the first diode, the anode of the first diode is grounded via the first resistor, the second end of the first inductor is respectively connected to the first end of the first capacitor and the positive electrode of the LED lamp, and the second end of the first capacitor and the negative electrode of the LED lamp are connected to the anode of the first diode.

10. The novel LED driving circuit with multi-mode current sampling according to claim 1, characterized in that: The sampling and comparison circuit comprises a first comparator, wherein a positive input terminal of the first comparator is connected to a reference voltage, a negative input terminal is connected to an output terminal of the multi-mode sampling module, and an output terminal is connected to an input terminal of the control module.

Images