LLC resonant conversion circuit and LED driving power supply

Abstract

The present invention relates to an LLC resonant conversion circuit and an LED driving power supply, comprising an energy conversion unit, an output unit, a signal detection unit, a signal control unit and a resonance control unit; the energy conversion unit controls the operation of the power supply and performs energy conversion based on the working state of the resonance control unit; the output unit processes the signal output by the energy conversion unit and generates an output voltage; the signal detection unit detects the output voltage and outputs a detection signal; the signal control unit controls the on-off between the driving unit and the resonance control unit according to the detection signal output by the signal detection unit; the resonance control unit switches its own working state according to the control of the signal control unit. The present invention does not need to add an additional auxiliary circuit, nor does it need to increase the volume of the LLC main transformer. By adjusting the resonance frequency and the resonance working state according to the change of the output voltage, the power supply can work near the resonance point under full load and light load, thereby reducing loss and heat generation and improving LLC efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of LED driving power supplies, and more specifically, to an LLC resonant conversion circuit and an LED driving power supply. Background Art

[0002] With the wide application of LED driver power in the market and the rise of global energy costs, the working conditions of LED power are constantly improving, and the requirements for power efficiency level are becoming more and more stringent. In recent years, in order to pursue high-efficiency power supply, soft switching technology has been widely used in the power supply field. The most common is LLC topology. At the resonant point frequency, the gain is 1, the efficiency is the highest, and the input voltage is equivalent to the output load. The voltage on other inductors and capacitors is equivalent to zero, and no large loss will be generated on these resonant components.

[0003] However, there are certain defects in the existing solutions, as follows:

[0004] 1. Use a fixed output voltage, the output voltage is a fixed value. Since the voltage range of the terminal customer's lamps varies greatly, it is not conducive to matching the terminal customer's lamps and cannot meet the customer's usage needs. This method has no practical value.

[0005] 2. When the output load voltage decreases, the LLC efficiency can be improved by adding an auxiliary circuit to reduce the switching frequency. Adding an auxiliary circuit requires adding an auxiliary winding, which results in greater power loss and more severe heat generation. The circuit is more complex and has obvious disadvantages.

[0006] 3. Reduce the frequency by increasing the size of the LLC main transformer to meet the output voltage change requirements. However, this will increase the power cost and the size of the power supply. This is contrary to the requirements of miniaturization, low cost and high frequency of LED power supplies.

[0007] 4. The LED driver power supply does not add a device to change the resonant frequency by light load or heavy load. In this case, when the resonant frequency is too large or too small, the primary side does not transfer energy to the output side, and the current circulates inside the primary side, causing losses. At the same time, the greater the proportion of this time in the cycle, the greater the effective value of the primary current, which will also increase the conduction loss of the primary side, causing serious heating of the power supply. Summary of the invention

[0008] The technical problem to be solved by the present invention is to provide an LLC resonant conversion circuit and an LED driving power supply in view of the defects of the prior art.

[0009] The technical solution adopted by the present invention to solve the technical problem is: constructing an LLC resonant conversion circuit including: an energy conversion unit, an output unit, a signal detection unit, a signal control unit and a resonance control unit;

[0010] The energy conversion unit is connected to the resonance control unit and is used to control the operation of the power supply and perform energy conversion based on the working state of the resonance control unit;

[0011] The output unit is connected to the energy conversion unit and is used to process the signal output by the energy conversion unit and generate an output voltage;

[0012] The signal detection unit is connected to the output unit, and is used to detect the output voltage generated by the output unit and output a detection signal;

[0013] The signal control unit is connected to the driving unit and the signal detection unit, and is used to control the connection between the driving unit and the resonance control unit according to the detection signal output by the signal detection unit;

[0014] The resonance control unit is connected to the signal control unit and is used to switch its own working state according to the control of the signal control unit.

[0015] In the LLC resonant conversion circuit of the present invention, the signal detection unit includes: a first detection comparison circuit and a second detection comparison circuit;

[0016] The input end of the first detection comparison circuit is connected to the output end of the output unit, and the output end of the first detection circuit is connected to the first input end of the signal control unit;

[0017] An input end of the second detection and comparison circuit is connected to the first detection and comparison circuit, and an output end of the second detection and comparison circuit is connected to a second input end of the signal control unit.

[0018] In the LLC resonant conversion circuit of the present invention, the signal control unit includes: a first photoelectric control circuit and a second photoelectric control circuit;

[0019] The input end of the first photoelectric control circuit is connected to the output end of the first detection comparison circuit as the first input end of the signal control unit, and the output end of the first photoelectric control circuit is connected to the resonance control unit;

[0020] The input end of the second photoelectric control circuit is connected to the output end of the second detection comparison circuit as the second input end of the signal control unit, and the output end of the second photoelectric control circuit is connected to the resonance control unit.

[0021] In the LLC resonant conversion circuit of the present invention, the first photoelectric control circuit includes: a first photoelectric switch and a first switch circuit;

[0022] The input end of the first photoelectric switch is connected to the output end of the first detection and comparison circuit, the output end of the first photoelectric switch is connected to the input end of the first switch circuit, the conduction end of the first switch circuit is connected to the first output end of the driving unit, and the output end of the first switch circuit is connected to the first input end of the resonance control unit.

[0023] In the LLC resonant conversion circuit of the present invention, the second photoelectric control circuit includes: a second photoelectric switch and a second switch circuit;

[0024] The input end of the second photoelectric switch is connected to the output end of the second detection and comparison circuit, the output end of the second photoelectric switch is connected to the input end of the second switch circuit, the conduction end of the second switch circuit is connected to the second output end of the driving unit, and the output end of the second switch circuit is connected to the second input end of the resonance control unit.

[0025] In the LLC resonant conversion circuit of the present invention, the resonance control unit comprises: a first resonant circuit and a second resonant circuit;

[0026] The input end of the first resonant circuit is connected to the output end of the first switch circuit as the first input end of the resonance control unit, and the output end of the first resonant circuit is connected to the input end of the energy conversion unit;

[0027] The input end of the second resonant circuit is connected to the output end of the second switch circuit as the second input end of the resonance control unit, and the output end of the second resonant circuit is connected to the input end of the energy conversion unit.

[0028] In the LLC resonant conversion circuit of the present invention, the first resonant circuit comprises: a third switch circuit and a second resonant cavity;

[0029] The input end of the third switch circuit is connected to the output end of the first switch circuit as the input end of the first resonant circuit, and the output end of the third switch circuit is connected to the input end of the energy conversion unit through the second resonant cavity.

[0030] In the LLC resonant conversion circuit of the present invention, the second resonant circuit comprises: a fourth switch circuit and a first resonant cavity;

[0031] The input end of the fourth switch circuit is connected to the output end of the second switch circuit as the input end of the second resonant circuit, and the output end of the fourth switch circuit is connected to the input end of the energy conversion unit through the first resonant cavity.

[0032] In the LLC resonant conversion circuit described in the present invention, the output unit includes: a first diode, a second diode, an output capacitor and an output resistor;

[0033] The anode of the first diode is connected to the first output terminal of the energy conversion unit, and the cathode of the first diode is connected to the cathode of the second diode and connected to the output terminal of the LED driving power supply;

[0034] The anode of the second diode is connected to the second output terminal of the energy conversion unit, the first terminal of the output capacitor is connected to the cathode of the first diode, the second terminal of the output capacitor is grounded, and the output resistor is connected in parallel with the output capacitor.

[0035] In the LLC resonant conversion circuit of the present invention, the first detection comparison circuit comprises: a seventh resistor, a fourth resistor, an eighth resistor, a second comparison operator and an input portion of a first photocoupler;

[0036] A first end of the seventh resistor is connected to the output end of the LED driving power supply, and a second end of the seventh resistor is connected to the input end of the second detection comparison circuit;

[0037] The first end of the fourth resistor is connected to the power supply voltage, the second end of the fourth resistor is connected to the negative input end of the second comparator, the positive end of the second comparator is connected to the first end of the seventh resistor, the output end of the second comparator is connected to the input end of the input part of the first photoelectric coupler through the eighth resistor, the ground end of the second comparator and the ground end of the input end of the first photoelectric coupler are grounded, and the power supply end of the second comparator is connected to the power supply voltage.

[0038] In the LLC resonant conversion circuit of the present invention, the second detection comparison circuit comprises: a sixth resistor, a fifth resistor, a ninth resistor, a third comparison operator and an input portion of a second photoelectric coupler;

[0039] The first end of the sixth resistor is connected to the second end of the seventh resistor as the input end of the second detection comparison circuit, and the second end of the sixth resistor is grounded;

[0040] The first end of the fifth resistor is connected to the positive input end of the third comparison operator and to the second end of the fourth resistor, and the second end of the fifth resistor is grounded;

[0041] The negative input terminal of the third comparison operator is connected to the first terminal of the sixth resistor, the output terminal of the third comparison operator is connected to the input terminal of the input part of the second photoelectric coupler through the ninth resistor, and the ground terminal of the input terminal of the second photoelectric coupler is grounded.

[0042] In the LLC resonant conversion circuit of the present invention, the first photoelectric switch includes: an output portion of a first photoelectric coupler; the first switch circuit includes: a first transistor and a second transistor;

[0043] The input end of the output part of the first photocoupler is connected to a high level, the output end of the output part of the first photocoupler is connected to the input end of the first transistor and the input end of the second transistor, and the output part of the first photocoupler is photoelectrically coupled with the input part of the first photocoupler;

[0044] The control end of the first transistor is connected to the first output end of the driving unit through the second resistor, and the output end of the first transistor is connected to the third switch circuit;

[0045] The control end of the second transistor is connected to the second output end of the driving unit through a third resistor, and the output end of the second transistor is connected to the third switch circuit.

[0046] In the LLC resonant conversion circuit of the present invention, the second photoelectric switch includes: an output portion of a second photoelectric coupler; the second switch circuit includes: a third transistor and a fourth transistor;

[0047] The input end of the output part of the second photocoupler is connected to a high level, the output end of the output part of the second photocoupler is connected to the input end of the third transistor and the input end of the fourth transistor, and the output part of the second photocoupler is photoelectrically coupled with the input part of the second photocoupler;

[0048] The control end of the third transistor is connected to the first output end of the driving unit through a second resistor, and the output end of the third transistor is connected to the fourth switch circuit;

[0049] The control end of the fourth transistor is connected to the second output end of the driving unit through a third resistor, and the output end of the fourth transistor is connected to the fourth switch circuit.

[0050] In the LLC resonant conversion circuit of the present invention, the fourth switch circuit includes: a third MOS transistor and a fourth MOS transistor; the first resonant cavity includes: a second inductor and a second capacitor;

[0051] The gate of the third MOS tube is connected to the output end of the third triode, the source of the third MOS tube is connected to the drain of the fourth MOS tube and the first end of the second inductor, and the drain of the third MOS tube is connected to the input signal;

[0052] The gate of the fourth MOS tube is connected to the output end of the fourth triode, the source of the fourth MOS tube is grounded, and the second end of the second inductor is connected to the input end of the energy conversion unit through the second capacitor.

[0053] In the LLC resonant conversion circuit of the present invention, the third switch circuit includes: a first MOS transistor and a second MOS transistor; the second resonant cavity includes: a first inductor, a first capacitor, the second inductor and the second capacitor;

[0054] The gate of the first MOS transistor is connected to the output end of the first triode, the source of the first MOS transistor is connected to the drain of the second MOS transistor and the first end of the first inductor, and the drain of the first MOS transistor is connected to the input signal;

[0055] The gate of the second MOS tube is connected to the output end of the second triode, and the source of the second MOS tube is grounded;

[0056] The second end of the first inductor is connected to the first end of the second inductor through the first capacitor.

[0057] The present invention also provides an LED driving power supply, comprising: the LLC resonant conversion circuit described above.

[0058] The LLC resonant conversion circuit and LED driving power supply implemented in the present invention have the following beneficial effects: including an energy conversion unit, an output unit, a signal detection unit, a signal control unit and a resonance control unit; the energy conversion unit controls the operation of the power supply and performs energy conversion based on the working state of the resonance control unit; the output unit processes the signal output by the energy conversion unit and generates an output voltage; the signal detection unit detects the output voltage and outputs a detection signal; the signal control unit controls the on-off between the driving unit and the resonance control unit according to the detection signal output by the signal detection unit; the resonance control unit switches its own working state according to the control of the signal control unit. The present invention does not need to add additional auxiliary circuits, nor does it need to increase the volume of the LLC main transformer. By adjusting the resonant frequency and the resonant working state according to the change of the output voltage, the power supply can work near the resonance point under full load and light load, reducing losses and heat generation, and improving LLC efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0060] Figure 1 It is a principle block diagram of the first embodiment of the LLC resonant conversion circuit provided by the present invention;

[0061] Figure 2It is a principle block diagram of the second embodiment of the LLC resonant conversion circuit provided by the present invention;

[0062] Figure 3 It is a circuit diagram of an LLC resonant conversion circuit provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0063] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0064] refer to Figure 1 , which is a principle block diagram of Embodiment 1 of the LLC resonant conversion circuit provided by the present invention.

[0065] Specifically, Figure 1 As shown, the LLC resonant conversion circuit may include: an energy conversion unit 40 , an output unit 50 , a signal detection unit 10 , a signal control unit 20 and a resonance control unit 30 .

[0066] The energy conversion unit 40 is connected to the resonance control unit 30 , and is used to control the operation of the power supply and perform energy conversion based on the operation state of the resonance control unit 30 .

[0067] The output unit 50 is connected to the energy conversion unit 40 and is used to process the signal output by the energy conversion unit 40 and generate an output voltage.

[0068] The signal detection unit 10 is connected to the output unit 50 and is used to detect the output voltage generated by the output unit 50 and output a detection signal.

[0069] The signal control unit 20 is connected to the driving unit U1 and the signal detection unit 10 , and is used to control the connection between the driving unit U1 and the resonance control unit 30 according to the detection signal output by the signal detection unit 10 .

[0070] The resonance control unit 30 is connected to the signal control unit 20 and is used to switch its own working state according to the control of the signal control unit 20 .

[0071] Specifically, the signal detection unit 10 detects the output voltage and outputs a corresponding detection signal based on the detected output voltage to control the signal control unit 20 to perform corresponding on-off control, so that the resonance control unit 30 can select different working states and resonance modes based on the on-off control of the signal control unit 20, thereby achieving the purpose of adjusting the resonance frequency and the resonance mode in real time as the output voltage changes, so that the light load efficiency can be improved without affecting the full load efficiency of the driving power supply, so that both full load and light load can operate near the resonance point, effectively reducing losses and heat, improving the working efficiency of the LLC resonant conversion circuit, and improving the service life and reliability of the driving power supply.

[0072] Furthermore, if Figure 2 The figure shows a principle block diagram of the second embodiment of the present invention.

[0073] like Figure 2 As shown, in this embodiment, the signal detection unit 10 includes: a first detection comparison circuit 11 and a second detection comparison circuit 12.

[0074] The input end of the first detection comparison circuit 11 is connected to the output end of the output unit 50, and the output end of the first detection circuit is connected to the first input end of the signal control unit 20. The input end of the second detection comparison circuit 12 is connected to the first detection comparison circuit 11, and the output end of the second detection comparison circuit 12 is connected to the second input end of the signal control unit 20.

[0075] Furthermore, if Figure 2 As shown, the signal control unit 20 includes: a first photoelectric control circuit 21 and a second photoelectric control circuit 22 .

[0076] An input end of the first photoelectric control circuit 21 is connected to an output end of the first detection and comparison circuit 11 as a first input end of the signal control unit 20 , and an output end of the first photoelectric control circuit 21 is connected to the resonance control unit 30 .

[0077] An input end of the second photoelectric control circuit 22 is connected to an output end of the second detection and comparison circuit 12 as a second input end of the signal control unit 20 , and an output end of the second photoelectric control circuit 22 is connected to the resonance control unit 30 .

[0078] Optionally, in some embodiments, such as Figure 2 As shown, the first photoelectric control circuit 21 includes: a first photoelectric switch 211 and a first switch circuit 212 .

[0079] The input end of the first photoelectric switch 211 is connected to the output end of the first detection and comparison circuit 11, the output end of the first photoelectric switch 211 is connected to the input end of the first switch circuit 212, the conduction end of the first switch circuit 212 is connected to the first output end of the driving unit U1, and the output end of the first switch circuit 212 is connected to the first input end of the resonance control unit 30.

[0080] Optionally, in some embodiments, such as Figure 2 As shown, the second photoelectric control circuit 22 includes: a second photoelectric switch 221 and a second switch circuit 222 .

[0081] The input end of the second photoelectric switch 221 is connected to the output end of the second detection and comparison circuit 12, the output end of the second photoelectric switch 221 is connected to the input end of the second switch circuit 222, the conduction end of the second switch circuit 222 is connected to the second output end of the driving unit U1, and the output end of the second switch circuit 222 is connected to the second input end of the resonance control unit 30.

[0082] Furthermore, if Figure 2 As shown, in this embodiment, the resonance control unit 30 includes: a first resonance circuit 31 and a second resonance circuit 32 .

[0083] The input end of the first resonant circuit 31 is connected to the output end of the first switch circuit 212 as the first input end of the resonance control unit 30 , and the output end of the first resonant circuit 31 is connected to the input end of the energy conversion unit 40 .

[0084] The input end of the second resonant circuit 32 is connected to the output end of the second switch circuit 222 as the second input end of the resonance control unit 30 , and the output end of the second resonant circuit 32 is connected to the input end of the energy conversion unit 40 .

[0085] Optionally, in some embodiments, such as Figure 2 As shown, the first resonant circuit 31 includes: a third switch circuit 311 and a second resonant cavity 312 .

[0086] The input end of the third switch circuit 311 is connected to the output end of the first switch circuit 212 as the input end of the first resonance circuit 31 , and the output end of the third switch circuit 311 is connected to the input end of the energy conversion unit 40 through the second resonance cavity 312 .

[0087] Optionally, in some embodiments, such as Figure 2 As shown, the second resonant circuit 32 includes: a fourth switch circuit 321 and a first resonant cavity 322 .

[0088] The input end of the fourth switch circuit 321 is connected to the output end of the second switch circuit 222 as the input end of the second resonance circuit 32 , and the output end of the fourth switch circuit 321 is connected to the input end of the energy conversion unit 40 through the first resonance cavity 322 .

[0089] Specifically, Figure 2As shown, when the first detection and comparison circuit 11 is turned on, the first photoelectric switch 211 is turned on, and then the first switch circuit 212 is controlled to be turned on, so that the first output end and the second output end of the driving unit U1 can output the first drive signal and the second drive signal through the second resistor R2 and the third resistor R3 respectively. Among them, the first drive signal and the second drive signal are transmitted to the third switch circuit 311 through the first switch circuit 212, and at this time, the resonance control unit 30 enters the first resonance mode, that is, at this time, the second resonance cavity 312 works, and the first resonance cavity 322 does not work. When the second detection and comparison circuit 12 is turned on, the second photoelectric switch 221 is turned on, and then the second switch circuit 222 is controlled to be turned on, so that the first output end and the second output end of the driving unit U1 can output the first drive signal and the second drive signal through the second resistor R2 and the third resistor R3 respectively. Among them, the first drive signal and the second drive signal are transmitted to the fourth switch circuit 321 through the second switch circuit 222, and at this time, the resonance control unit 30 enters the second resonance mode, that is, at this time, the first resonance cavity 322 works, and the second resonance cavity 312 does not work.

[0090] The on or off of the first detection comparison circuit 11 and the on or off of the second detection comparison circuit 12 are determined by the output voltage. Therefore, the embodiment of the present invention can adjust the resonance mode and the resonance frequency according to the change of the output voltage, so that the efficiency of the light load can be improved without affecting the full load efficiency. Both the full load and the light load can work near the resonance point, reducing the loss and heat, thereby improving the working efficiency of the LLC resonant conversion circuit.

[0091] The following is a description of the specific embodiments.

[0092] refer to Figure 3 , which is a circuit diagram of an optional embodiment of the LLC resonant conversion circuit provided by the present invention.

[0093] Specifically, Figure 3 As shown, in this embodiment, the output unit 50 includes: a first diode D1, a second diode D2, an output capacitor C0 and an output resistor R0.

[0094] The anode of the first diode D1 is connected to the first output terminal of the energy conversion unit 40 , and the cathode of the first diode D1 is connected to the cathode of the second diode D2 and connected to the output terminal of the LED driving power supply.

[0095] The anode of the second diode D2 is connected to the second output terminal of the energy conversion unit 40 , the first terminal of the output capacitor C0 is connected to the cathode of the first diode D1 , the second terminal of the output capacitor C0 is grounded, and the output resistor R0 is connected in parallel with the output capacitor C0 .

[0096] like Figure 3As shown, in this embodiment, the first detection comparison circuit 11 includes: a seventh resistor R7, a fourth resistor R4, an eighth resistor R8, a second comparison operator U2 and an input part OT1-B of the first photocoupler.

[0097] A first end of the seventh resistor R7 is connected to the output end of the LED driving power supply, and a second end of the seventh resistor R7 is connected to the input end of the second detection and comparison circuit 12 .

[0098] A first end of the fourth resistor R4 is connected to the power supply voltage (VCC2), a second end of the fourth resistor R4 is connected to the negative input end of the second comparator U2, a positive end of the second comparator U2 is connected to the first end of the seventh resistor R7, an output end of the second comparator U2 is connected to the input end of the input part OT1-B of the first photocoupler through an eighth resistor R8, a ground end of the second comparator U2 and a ground end of the input part OT1-B of the first photocoupler are grounded, and a power supply end of the second comparator U2 is connected to the power supply voltage.

[0099] like Figure 3 As shown, in this embodiment, the second detection comparison circuit 12 includes: a sixth resistor R6, a fifth resistor R5, a ninth resistor R9, a third comparison operator U3 and an input part OT2-B of the second photocoupler.

[0100] The first end of the sixth resistor R6 is connected to the second end of the seventh resistor R7 as the input end of the second detection and comparison circuit 12, and the second end of the sixth resistor R6 is grounded.

[0101] A first end of the fifth resistor R5 is connected to the positive input end of the third comparison operator U3 and to the second end of the fourth resistor R4 , and a second end of the fifth resistor R5 is grounded.

[0102] The negative input terminal of the third comparison operator U3 is connected to the first end of the sixth resistor R6, and the output terminal of the third comparison operator U3 is connected to the input terminal of the input part OT2-B of the second photocoupler through the ninth resistor R9. The ground terminal of the input part OT2-B of the second photocoupler is grounded.

[0103] like Figure 3 As shown, in this embodiment, the first photoelectric switch 211 includes: an output part OT1-A of a first photoelectric coupler; the first switch circuit 212 includes: a first transistor and a second transistor.

[0104] The input end of the output part OT1-A of the first photocoupler is connected to a high level (VCC1), the output end of the output part OT1-A of the first photocoupler is connected to the input end of the first transistor and the input end of the second transistor, and the output part OT1-A of the first photocoupler is photoelectrically coupled with the input part OT1-B of the first photocoupler;

[0105] The control end of the first transistor is connected to the first output end of the driving unit U1 through the second resistor R2, and the output end of the first transistor is connected to the third switch circuit 311;

[0106] The control end of the second transistor is connected to the second output end of the driving unit U1 through the third resistor R3 , and the output end of the second transistor is connected to the third switch circuit 311 .

[0107] like Figure 3 As shown, in this embodiment, the second photoelectric switch 221 includes: an output portion OT2-A of a second photocoupler; and the second switch circuit 222 includes: a third transistor and a fourth transistor.

[0108] The input end of the output part OT2-A of the second photocoupler is connected to a high level, the output end of the output part OT2-A of the second photocoupler is connected to the input end of the third transistor and the input end of the fourth transistor, and the output part OT2-A of the second photocoupler is photoelectrically coupled with the input part OT2-B of the second photocoupler;

[0109] The control end of the third transistor is connected to the first output end of the driving unit U1 through the second resistor R2, and the output end of the third transistor is connected to the fourth switch circuit 321;

[0110] The control end of the fourth transistor is connected to the second output end of the driving unit U1 through the third resistor R3 , and the output end of the fourth transistor is connected to the fourth switch circuit 321 .

[0111] like Figure 3 As shown, in this embodiment, the fourth switch circuit 321 includes: a third MOS transistor Q3 and a fourth MOS transistor Q4; the first resonant cavity 322 includes: a second inductor L2 and a second capacitor C2.

[0112] The gate of the third MOS transistor Q3 is connected to the output end of the third triode, the source of the third MOS transistor Q3 is connected to the drain of the fourth MOS transistor Q4 and the first end of the second inductor L2, and the drain of the third MOS transistor Q3 is connected to the input signal (UIN).

[0113] The gate of the fourth MOS transistor Q4 is connected to the output end of the fourth triode, the source of the fourth MOS transistor Q4 is grounded, and the second end of the second inductor L2 is connected to the input end of the energy conversion unit 40 through the second capacitor C2.

[0114] like Figure 3 As shown, in this embodiment, the third switch circuit 311 includes: a first MOS transistor Q1 and a second MOS transistor Q2; the second resonant cavity 312 includes: a first inductor L1, a first capacitor C1, a second inductor L2 and a second capacitor C2.

[0115] The gate of the first MOS transistor Q1 is connected to the output end of the first transistor, the source of the first MOS transistor Q1 is connected to the drain of the second MOS transistor Q2 and the first end of the first inductor L1, and the drain of the first MOS transistor Q1 is connected to the input signal.

[0116] The gate of the second MOS transistor Q2 is connected to the output end of the second transistor, and the source of the second MOS transistor Q2 is grounded.

[0117] The second end of the first inductor L1 is connected to the first end of the second inductor L2 via the first capacitor C1.

[0118] Optionally, in the embodiment of the present invention, the first triode, the second triode, the third triode and the fourth triode may all be implemented by two triodes connected in series.

[0119] In some embodiments, such as Figure 3 As shown, the first transistor can be composed of a transistor Q1A and a transistor Q1B connected in series. The base of the transistor Q1A and the base of the transistor Q1B are connected to form a control end of the first transistor, the collector of the transistor Q1A is the input end of the first transistor, the emitter of the transistor Q1A and the emitter of the transistor Q1B are connected to form an output end of the first transistor, and the collector of the transistor Q1B is connected to the driving unit U1.

[0120] Similarly, the second triode can be composed of a triode Q2A and a triode Q2B connected in series, wherein the base of the triode Q2A and the base of the triode Q2B are connected to form a control end of the second triode, the collector of the triode Q2A is the input end of the second triode, the emitter of the triode Q2A and the emitter of the triode Q2B are connected to form an output end of the second triode, and the collector of the triode Q2B is grounded.

[0121] The third transistor can be composed of a transistor Q3A and a transistor Q3B connected in series, wherein the base of the transistor Q3A and the base of the transistor Q3B are connected to form a control end of the third transistor, the collector of the transistor Q3A is the input end of the third transistor, the emitter of the transistor Q3A and the emitter of the transistor Q3B are connected to form an output end of the third transistor, and the collector of the transistor Q3B is connected to the driving unit U1.

[0122] The fourth transistor may be composed of a transistor Q4A and a transistor Q4B connected in series, wherein the base of the transistor Q4A and the base of the transistor Q4B are connected to form a control end of the fourth transistor, the collector of the transistor Q4A is the input end of the fourth transistor, the emitter of the transistor Q4A and the emitter of the transistor Q4B are connected to form an output end of the fourth transistor, and the collector of the transistor Q4B is grounded.

[0123] like Figure 3As shown, in this embodiment, the energy conversion unit includes a transformer, wherein the first end of the primary winding T1A of the transformer is connected to the second capacitor C2 as the input end of the energy conversion unit, and the second end of the primary winding T1A of the transformer is grounded. The first output end of the secondary winding T1B of the transformer is connected to the anode of the first diode D1 as the first output end of the energy conversion unit, the second output end of the secondary winding T1B of the transformer is connected to the anode of the second diode D2 as the second output end of the energy conversion unit, and the third output end of the secondary winding T1B of the transformer is grounded.

[0124] like Figure 3 As shown, in the embodiment of the present invention, the specific working principle of the LLC resonant conversion circuit is as follows:

[0125] The first resonant cavity 322 is composed of a second inductor L2 and a second capacitor C2. The second resonant cavity 312 is composed of a first inductor L1, a first capacitor C1, a second inductor L2 and a second capacitor C2. The resonant frequencies are: and

[0126] Specifically, when the output voltage signal UO changes, the voltage changes at the sampling point A and the sampling point B are compared with the fixed voltage signals at the point C of the second comparison operator U2 and the point D of the third comparison operator U3 to obtain the high and low levels of the output ends of the second comparison operator U2 and the third comparison operator U3, thereby determining the conduction and cutoff of the input part OT1-B of the first photocoupler and the input part OT2-B of the second photocoupler. The conduction and cutoff of the input part OT1-B of the first photocoupler and the input part OT2-B of the second photocoupler are respectively used to determine the conduction and cutoff of the output part OT1-A of the first photocoupler and the output part OT2-A of the second photocoupler.

[0127] The conduction and cutoff of the output part OT1-A of the first photocoupler determines the switching of the transistors Q1A and Q1B, and the switching of the transistors Q1A and Q1B determines whether a driving signal is provided from the GDA pin (first output end) of the driving unit U1 through the second resistor R2, the transistors Q1A and Q1B to the first MOS transistor Q1 to make it work; at the same time, the conduction and cutoff of the output part OT1-A of the first photocoupler also determines the switching of the transistors Q2A and Q2B, and the switching of the transistors Q2A and Q2B determines whether a driving signal is provided from the GDB pin (second output end) of the driving unit U1 through the third resistor R3, the transistors Q2A and Q2B to the second MOS transistor Q2 to make it work. Whether the first MOS transistor Q1 and the second MOS transistor Q2 work or not determines whether the second resonant cavity 312 (L1, C1, L2, C2) works or not and the size of the resonant frequency fr2.

[0128] The conduction and cutoff of the output part OT2-A of the second photocoupler determines the switch of the transistor Q3A and the transistor Q3B, and the switch of the transistor Q3A and the transistor Q3B determines whether a driving signal is provided from the GDA pin of the driving unit U1 through the second resistor R2, the transistor Q3A and the transistor Q3B to the third MOS transistor Q3 to make it work; at the same time, the conduction and cutoff of the output part OT2-A of the second photocoupler also determines the switch of the transistor Q4A and the transistor Q4B, and the switch of the transistor Q4A and the transistor Q4B determines whether a driving signal is provided from the GDB pin of the driving unit U1 through the third resistor R3, the transistor Q4A and the transistor Q4B to the fourth OS transistor to make it work. Whether the third MOS transistor Q3 and the fourth MSO transistor work or not determines whether the first resonant cavity 322 (L1, C2) works or not and the size of the resonant frequency fr1.

[0129] Therefore, whether the resonant elements (L1, C1, L2, C2) of the second resonant cavity 312 participate in the resonance or the resonant elements (L2, C2) of the first resonant cavity 322 participate in the resonance is determined according to the change of the output voltage UO, that is, it can automatically change to the resonant frequency fr1 or fr2 according to the change of the output voltage, so that both light load and heavy load work as close to the resonant frequency point as possible, so that the LLC resonant conversion circuit always works in the best working efficiency area.

[0130] Here’s how it works:

[0131] First, when the output voltage signal of the LED driving power supply decreases, the output voltage is reduced through the voltage division of the seventh resistor R7 and the sixth resistor R6 and compared with the fixed voltage VCC2 through the voltage division of the fourth resistor R4 and the fifth resistor R5, so that the voltage signal at point A is smaller than the voltage signal at point C. At this time, the output end of the second comparison operator U2 outputs a low level; at the same time, the voltage signal at point B is smaller than the voltage signal at point D, so the output end of the third comparison operator U3 outputs a high level.

[0132] 1) When the second comparison operator U2 outputs a low level, the input part OT1-B of the first photocoupler is turned off. Since the input part OT1-B of the first photocoupler is turned off, the output part OT1-A of the first photocoupler is turned off. The output part OT1-A of the first photocoupler is turned off, so that the transistors Q1A and Q1B, the transistors Q2A and Q2B are turned off. At this time, there is no drive signal output to make the transistors Q1A and Q1B, the transistors Q2A and Q2B work, and the first MOS transistor Q1 and the second MOS transistor Q2 are turned off.

[0133] The first MOS transistor Q1 and the second MOS transistor Q2 are turned off, so that the four elements L1, L2, C1, and C2 in the second resonant cavity 312 do not work.

[0134] 2) When the third comparison operator U3 outputs a high level, the input part OT2-B of the second photocoupler is turned on. Since the input part OT2-B of the second photocoupler is turned on, the output part OT2-A of the second photocoupler is turned on, and the output part OT2-A of the second photocoupler is turned on, so that the triode Q3A and the triode Q3B, the triode Q4A and the triode Q4B are turned on. At this time, a driving signal is output through the GDA pin and the GDB pin of the driving unit U1, so that the triode Q3A and the triode Q3B, the triode Q4A and the triode Q4B work, and respectively drive the third MOS tube Q3 and the fourth MOS tube Q4, that is, the third MOS tube Q3 and the fourth MOS tube Q4 are turned on. The third MOS tube Q3 and the fourth MOS tube Q4 are turned on, so that the two elements L2 and C2 of the first resonant cavity 322 participate in the resonance. Finally, the purpose of reducing the output voltage and increasing the resonant frequency is achieved.

[0135] Second, when the output voltage signal of the LED driving power supply increases, the output voltage is increased by the voltage division of the seventh resistor R7 and the sixth resistor R6 and compared with the voltage division of the fixed voltage VCC2 by the fourth resistor R4 and the fifth resistor R5, so that the voltage signal at point A is greater than the voltage signal at point C. At this time, the output end of the second comparison operator U2 outputs a high level; at the same time, the voltage signal at point B is greater than the voltage signal at point D, so the output end of the third comparison operator U3 outputs a low level.

[0136] 1) When the second comparison operator U2 outputs a high level, the input part OT1-B of the first photocoupler is turned on. Since the input part OT1-B of the first photocoupler is turned on, the output part OT1-A of the first photocoupler is turned on, and the output part OT1-A of the first photocoupler is turned on so that the transistors Q1A and Q1B, the transistors Q2A and Q2B are turned on. At this time, a driving signal will pass through the GDA pin and the GDB pin of U1 to make the transistors Q1A and Q1B, the transistors Q2A and Q2B work, and drive the first MOS transistor Q1 and the second MOS transistor Q2 respectively, that is, the first MOS transistor Q1 and the second MOS transistor Q2 are turned on. When the first MOS transistor Q1 and the second MOS transistor Q2 are turned on, the four elements L1, L2, C1, and C2 of the second resonant cavity 312 simultaneously participate in the resonant operation.

[0137] 2) When the third comparison operator U3 outputs a low level, the input part OT2-B of the second photocoupler is cut off. Since the input part OT2-B of the second photocoupler is cut off, the output part OT2-A of the second photocoupler is cut off, and the output part OT2-A of the second photocoupler is cut off, so that the transistors Q3A and Q3B, the transistors Q4A and Q4B are turned off. At this time, there will be no driving signal through the GDA pin and the GDB pin of U1 to make the transistors Q3A and Q3B, the transistors Q4A and Q4B work, and the third MOS tube Q3 and the fourth MOS tube Q4 are turned off. The third MOS tube Q3 and the fourth MOS tube Q4 are turned off so that the L2 and C2 components of the first resonant cavity 322 do not participate in the resonance. Finally, the purpose of increasing the output voltage and reducing the resonant frequency is achieved.

[0138] The embodiment of the present invention samples the output voltage, and samples or compares or switches the signal through resistors, comparators, optocouplers, MOS tubes, inductors, capacitors and other devices, to reflect the change of the output voltage to the change of the resonant frequency, so as to effectively change the resonant cavity parameters and the resonant frequency by detecting the sampled output voltage. The resonant frequency is adjusted in real time according to the weight of the output voltage load, so that both light load and heavy load (full load) work as close to the resonant frequency point as possible, thereby improving the working efficiency of the LLC circuit. It also improves the applicable voltage range and reliability of the LED drive power supply.

[0139] Furthermore, in some other embodiments, the present invention also provides an LED driving power supply. Optionally, the LED driving power supply may include the LLC resonant conversion circuit disclosed in the embodiments of the present invention.

[0140] By providing the LLC resonant conversion circuit, the working efficiency of the LED driving power supply can be improved, and the applicable voltage range and reliability of the LED driving power supply can be effectively increased.

[0141] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0142] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0143] The steps of the method or algorithm described in conjunction with the embodiments disclosed herein may be implemented directly using hardware, a software module executed by a processor, or a combination of the two. The software module may be placed in a random access memory (RAM), a memory, a read-only memory (ROM), an electrically programmable ROM, an electrically erasable programmable ROM, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0144] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot limit the scope of protection of the present invention. All equivalent changes and modifications made to the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. An LLC resonant conversion circuit, characterized in that: include: An energy conversion unit, an output unit, a signal detection unit, a signal control unit and a resonance control unit; The energy conversion unit is connected to the resonance control unit and is used to control the operation of the power supply and perform energy conversion based on the working state of the resonance control unit; The output unit is connected to the energy conversion unit and is used to process the signal output by the energy conversion unit and generate an output voltage; The signal detection unit is connected to the output unit, and is used to detect the output voltage generated by the output unit and output a detection signal; The signal detection unit includes: a first detection comparison circuit and a second detection comparison circuit; the input end of the first detection comparison circuit is connected to the output end of the output unit, and the output end of the first detection comparison circuit is connected to the first input end of the signal control unit; the input end of the second detection comparison circuit is connected to the first detection comparison circuit, and the output end of the second detection comparison circuit is connected to the second input end of the signal control unit; The signal control unit is connected to the driving unit and the signal detection unit, and is used to control the on / off between the driving unit and the resonance control unit according to the detection signal output by the signal detection unit; the signal control unit includes: a first photoelectric control circuit and a second photoelectric control circuit; the input end of the first photoelectric control circuit is connected to the output end of the first detection comparison circuit as the first input end of the signal control unit, and the output end of the first photoelectric control circuit is connected to the resonance control unit; the input end of the second photoelectric control circuit is connected to the output end of the second detection comparison circuit as the second input end of the signal control unit, and the output end of the second photoelectric control circuit is connected to the resonance control unit; the first photoelectric control circuit includes: a first photoelectric switch and a first switch The first photoelectric control circuit comprises: a second photoelectric switch and a second switch circuit; the input end of the first photoelectric switch is connected to the output end of the first detection and comparison circuit, the output end of the first photoelectric switch is connected to the input end of the first switch circuit, the conduction end of the first switch circuit is connected to the first output end of the driving unit, and the output end of the first switch circuit is connected to the first input end of the resonance control unit; the second photoelectric control circuit comprises: a second photoelectric switch and a second switch circuit; the input end of the second photoelectric switch is connected to the output end of the second detection and comparison circuit, the output end of the second photoelectric switch is connected to the input end of the second switch circuit, the conduction end of the second switch circuit is connected to the second output end of the driving unit, and the output end of the second switch circuit is connected to the second input end of the resonance control unit; The resonance control unit is connected to the signal control unit and is used to switch its own working state according to the control of the signal control unit; the resonance control unit includes: a first resonance circuit and a second resonance circuit; the input end of the first resonance circuit is connected to the output end of the first switch circuit as the first input end of the resonance control unit, and the output end of the first resonance circuit is connected to the input end of the energy conversion unit; the input end of the second resonance circuit is connected to the output end of the second switch circuit as the second input end of the resonance control unit, and the output end of the second resonance circuit is connected to the input end of the energy conversion unit; The first resonant circuit includes: a third switching circuit and a second resonant cavity; the input end of the third switching circuit is connected to the output end of the first switching circuit as the input end of the first resonant circuit, and the output end of the third switching circuit is connected to the input end of the energy conversion unit through the second resonant cavity.

2. The LLC resonant conversion circuit according to claim 1, characterized in that: The second resonant circuit comprises: a fourth switch circuit and a first resonant cavity; The input end of the fourth switch circuit is connected to the output end of the second switch circuit as the input end of the second resonant circuit, and the output end of the fourth switch circuit is connected to the input end of the energy conversion unit through the first resonant cavity.

3. The LLC resonant conversion circuit according to claim 2, characterized in that: The output unit includes: a first diode, a second diode, an output capacitor and an output resistor; The anode of the first diode is connected to the first output terminal of the energy conversion unit, and the cathode of the first diode is connected to the cathode of the second diode and connected to the output terminal of the LED driving power supply; The anode of the second diode is connected to the second output terminal of the energy conversion unit, the first terminal of the output capacitor is connected to the cathode of the first diode, the second terminal of the output capacitor is grounded, and the output resistor is connected in parallel with the output capacitor.

4. The LLC resonant conversion circuit according to claim 3, characterized in that: The first detection comparison circuit includes: a seventh resistor, a fourth resistor, an eighth resistor, a second comparison operator and an input portion of a first photocoupler; A first end of the seventh resistor is connected to the output end of the LED driving power supply, and a second end of the seventh resistor is connected to the input end of the second detection comparison circuit; The first end of the fourth resistor is connected to the power supply voltage, the second end of the fourth resistor is connected to the negative input end of the second comparator, the positive end of the second comparator is connected to the first end of the seventh resistor, the output end of the second comparator is connected to the input end of the input part of the first photoelectric coupler through the eighth resistor, the ground end of the second comparator and the ground end of the input end of the first photoelectric coupler are grounded, and the power supply end of the second comparator is connected to the power supply voltage.

5. The LLC resonant conversion circuit according to claim 4, characterized in that: The second detection comparison circuit includes: a sixth resistor, a fifth resistor, a ninth resistor, a third comparison operator and an input portion of a second photocoupler; The first end of the sixth resistor is connected to the second end of the seventh resistor as the input end of the second detection comparison circuit, and the second end of the sixth resistor is grounded; The first end of the fifth resistor is connected to the positive input end of the third comparison operator and to the second end of the fourth resistor, and the second end of the fifth resistor is grounded; The negative input terminal of the third comparison operator is connected to the first terminal of the sixth resistor, the output terminal of the third comparison operator is connected to the input terminal of the input part of the second photoelectric coupler through the ninth resistor, and the ground terminal of the input terminal of the second photoelectric coupler is grounded.

6. The LLC resonant conversion circuit according to claim 4, characterized in that: The first photoelectric switch includes: an output portion of a first photoelectric coupler; the first switch circuit includes: a first transistor and a second transistor; The input end of the output part of the first photocoupler is connected to a high level, the output end of the output part of the first photocoupler is connected to the input end of the first transistor and the input end of the second transistor, and the output part of the first photocoupler is photoelectrically coupled with the input part of the first photocoupler; The control end of the first transistor is connected to the first output end of the driving unit through a second resistor, and the output end of the first transistor is connected to the third switch circuit; The control end of the second transistor is connected to the second output end of the driving unit through a third resistor, and the output end of the second transistor is connected to the third switch circuit.

7. The LLC resonant conversion circuit according to claim 6, characterized in that: The second photoelectric switch includes: an output portion of a second photoelectric coupler; the second switch circuit includes: a third transistor and a fourth transistor; The input end of the output part of the second photocoupler is connected to a high level, the output end of the output part of the second photocoupler is connected to the input end of the third transistor and the input end of the fourth transistor, and the output part of the second photocoupler is photoelectrically coupled with the input part of the second photocoupler; The control end of the third transistor is connected to the first output end of the driving unit through a second resistor, and the output end of the third transistor is connected to the fourth switch circuit; The control end of the fourth transistor is connected to the second output end of the driving unit through a third resistor, and the output end of the fourth transistor is connected to the fourth switch circuit.

8. The LLC resonant conversion circuit according to claim 7, characterized in that: The fourth switch circuit includes: a third MOS tube and a fourth MOS tube; the first resonant cavity includes: a second inductor and a second capacitor; The gate of the third MOS tube is connected to the output end of the third triode, the source of the third MOS tube is connected to the drain of the fourth MOS tube and the first end of the second inductor, and the drain of the third MOS tube is connected to the input signal; The gate of the fourth MOS tube is connected to the output end of the fourth triode, the source of the fourth MOS tube is grounded, and the second end of the second inductor is connected to the input end of the energy conversion unit through the second capacitor.

9. The LLC resonant conversion circuit according to claim 8, characterized in that: The third switch circuit includes: a first MOS transistor and a second MOS transistor; the second resonant cavity includes: a first inductor, a first capacitor, the second inductor and the second capacitor; The gate of the first MOS transistor is connected to the output end of the first triode, the source of the first MOS transistor is connected to the drain of the second MOS transistor and the first end of the first inductor, and the drain of the first MOS transistor is connected to the input signal; The gate of the second MOS tube is connected to the output end of the second triode, and the source of the second MOS tube is grounded; The second end of the first inductor is connected to the first end of the second inductor through the first capacitor.

10. An LED driving power supply, characterized in that: include: The LLC resonant conversion circuit according to any one of claims 1 to 9.

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