A low-frequency flash LED lamp circuit

Abstract

The present invention discloses a low-frequency flicker LED lamp circuit, comprising a rectifier circuit for converting a mains AC voltage into a DC voltage output, a filter capacitor for controlling a fluctuation range of a DC voltage output by the rectifier circuit, a constant current conversion circuit for converting a DC voltage output by the rectifier circuit into a constant current output, an LED light-emitting circuit capable of emitting light under the drive of the constant current conversion circuit, and an electronic switch circuit. The electronic switch circuit has two states, namely, an on state and an off state, and can be turned on or off according to the instantaneous voltage of the mains, thereby reducing the discharge time of the filter capacitor and increasing the mains power supply time. The advantages are low cost and a power factor greater than or equal to 0.7, which can meet the technical requirements of subsequent products.

Description

Technical Field

[0001] The invention relates to an LED lamp circuit, in particular to a low-frequency flicker LED lamp circuit. Background Art

[0002] LED lighting fixtures with power between 5W and 25W usually require the power factor of the mains input current to be greater than 0.5. Currently, the LED lamp circuit that meets this power factor requirement usually includes a rectifier circuit, a constant current conversion circuit, an LED light-emitting circuit, and a filter capacitor. The circuit structure diagram is as follows: Figure 1 As shown. In the above LED lamp circuit, the rectifier circuit has a first input terminal, a second input terminal, a positive output terminal and a negative output terminal, the constant current conversion circuit has a positive electrode, a negative electrode, a positive output terminal and a negative output terminal, the LED light-emitting circuit has a positive electrode and a negative electrode, and the filter capacitor has a positive electrode and a negative electrode; the first input terminal and the second input terminal of the rectifier circuit are respectively connected to the live wire and the neutral wire of the mains, the positive output terminal of the rectifier circuit is connected to the positive electrode of the constant current conversion circuit, the negative output terminal of the rectifier circuit is connected to the negative electrode of the constant current conversion circuit, the positive output terminal and the negative output terminal of the constant current conversion circuit are respectively connected to the positive electrode and the negative electrode of the LED light-emitting circuit, the positive output terminal of the rectifier circuit is connected to the positive electrode of the filter capacitor, and the negative output terminal of the rectifier circuit is connected to the negative electrode of the filter capacitor. The rectifier circuit converts the AC voltage of the mains into a DC voltage and outputs it between its positive output terminal and negative output terminal. After the charging and discharging of the filter capacitor, the DC voltage fluctuation between the positive output terminal and the negative output terminal of the rectifier circuit is small; the constant current conversion circuit is implemented by a linear constant current circuit or a constant current circuit in the form of a step-down switching power supply. The DC voltage output by the rectifier circuit is connected between the positive and negative electrodes of the constant current conversion circuit, and a constant low-ripple DC current is output between the positive and negative output terminals of the constant current conversion circuit, thereby driving the LED light-emitting circuit to emit light in the form of low-frequency flicker.

[0003] The above LED lamp circuit not only has low flicker characteristics, but also has low cost. Based on the current conventional power factor standard, the power factor of the mains input current of this type of LED lamp circuit is not very high, usually just slightly greater than 0.5. However, with the EU's increasing requirements for the power factor of LED lighting fixtures with a power of 5W-25W, this type of LED lamp circuit requires that the power factor of its mains input current be greater than or equal to 0.7 while maintaining low flicker light emission. Therefore, the current low-cost and low-flicker LED lamp circuit of this type can no longer meet the technical requirements of subsequent products. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a low-frequency flicker LED lamp circuit which has a low cost and a power factor greater than or equal to 0.7 and can meet the technical requirements of subsequent products.

[0005] The technical solution adopted by the present invention to solve the above technical problems is: a low-frequency flicker LED lamp circuit, including a rectifier circuit for converting the AC voltage of the mains into a DC voltage output, a filter capacitor for reducing the fluctuation range of the DC voltage output by the rectifier circuit, a constant current conversion circuit for converting the DC voltage output by the rectifier circuit into a constant current output, and an LED light-emitting circuit that can emit light under the drive of the constant current conversion circuit. The low-frequency flicker LED lamp circuit also includes an electronic switch circuit, which has two states of on and off, and can be turned on or off according to the instantaneous voltage of the mains, thereby reducing the discharge time of the filter capacitor and increasing the mains power supply time.

[0006] The rectifier circuit has a first input terminal, a second input terminal, a positive output terminal, a negative output terminal and an instantaneous voltage terminal for outputting the instantaneous voltage of the mains. The constant current conversion circuit has a positive pole, a negative pole, a positive output terminal and a negative output terminal. The LED light-emitting circuit has a positive pole and a negative pole. The filter capacitor has a positive pole and a negative pole. The electronic switch circuit has a first terminal, a second terminal and a control terminal. The electronic switch circuit is provided with a first comparison voltage and a second comparison voltage. The first comparison voltage is greater than the second comparison voltage and less than the peak voltage of the mains. When the voltage connected to the control terminal of the electronic switch circuit is greater than or equal to the first comparison voltage, the electronic switch circuit is unidirectionally conducted from the first terminal to the second terminal. When the voltage connected to the control terminal of the electronic switch circuit is less than the second comparison voltage, the electronic switch circuit is unidirectionally conducted from the second terminal to the first terminal. When the voltage connected to the control end of the electronic switch circuit is greater than or equal to the second comparison voltage and less than the first comparison voltage, the first end and the second end of the electronic switch circuit are cut off, the positive output end of the rectifier circuit is connected to the positive electrode of the constant current conversion circuit, the negative output end of the rectifier circuit is connected to the negative electrode of the constant current conversion circuit, the positive output end of the constant current conversion circuit is connected to the positive electrode of the LED light-emitting circuit, the negative output end of the constant current conversion circuit is connected to the negative electrode of the LED light-emitting circuit, the negative output end of the rectifier circuit is connected to the negative electrode of the filter capacitor, the control end of the electronic switch circuit is connected to the instantaneous voltage end of the rectifier circuit, the second end of the electronic switch circuit is connected to the positive electrode of the filter capacitor, and the first end of the electronic switch circuit is connected to the positive output end of the rectifier circuit.In this structure, when the rectifier circuit is connected to the mains, the AC voltage of the mains is converted into a DC voltage. The maximum value of the voltage output between the positive output terminal and the negative output terminal of the rectifier circuit is the peak voltage of the mains, and the minimum value is 0, and it changes periodically in the form of a positive half-cycle of a sinusoidal wave. In a voltage change cycle, when the instantaneous voltage of the mains output by the rectifier circuit is greater than or equal to the first comparison voltage of the electronic switch circuit, the mains, after rectification, supplies power to the constant current conversion circuit on the one hand, and on the other hand, because the electronic switch circuit is unidirectionally conducted, the filter capacitor is charged. When the instantaneous voltage output by the mains after passing through the rectifier circuit is less than the first comparison voltage and greater than or equal to the second comparison voltage, the electronic switch circuit is cut off, and the mains voltage can neither charge the filter capacitor nor supply power to the constant current conversion circuit. At this time, only the mains voltage provides voltage for the constant current conversion circuit after passing through the rectifier circuit. When the instantaneous voltage output by the mains after passing through the rectifier circuit is less than the second comparison voltage, because the electronic switch circuit is unidirectionally conducted, the instantaneous voltage of the mains is lower than the voltage across the filter capacitor. At this time, the filter capacitor provides a working voltage for the constant current conversion circuit, while the mains cannot provide voltage for the constant current conversion circuit. Thus, the structure controls the extension of the duration of the input current in a mains voltage cycle through the electronic switch circuit, significantly improves the power factor, and makes the power factor of the mains supply current reach above 0.7. In addition, the voltage between the positive and negative electrodes of the constant current conversion circuit is maintained between the second comparison voltage and the peak value of the mains voltage. By adjusting the constant current conversion circuit, a low ripple current is output, thereby making the LED light-emitting circuit emit light with low frequency flicker.

[0007] The electronic switch circuit includes a unidirectional electronic switch and a unidirectional conduction circuit. The unidirectional electronic switch has a positive pole, a negative pole and a control terminal. When the positive pole and the negative pole of the unidirectional electronic switch are connected, the current direction is from the positive pole to the negative pole. When the current is reversed, the current flowing through the unidirectional electronic switch is zero. When the positive pole and the negative pole of the unidirectional electronic switch are cut off, no matter what the current direction between the positive pole and the negative pole is, the unidirectional electronic switch cannot flow current. The unidirectional conduction circuit has a positive pole and a negative pole. When the current direction is from the positive pole to the negative pole, the positive pole and the negative pole of the unidirectional conduction circuit are connected. When the current is reversed, the positive and negative electrodes of the one-way conducting circuit are cut off, the positive electrode of the one-way electronic switch is connected to the negative electrode of the one-way conducting circuit and the connection end thereof is the second end of the electronic switch circuit, the negative electrode of the one-way electronic switch is connected to the positive electrode of the one-way conducting circuit and the connection end thereof is the first end of the electronic switch circuit, the control end of the one-way electronic switch is the control end of the electronic switch circuit, the second comparison voltage is set in the internal circuit of the one-way electronic switch, and the magnitude of the first comparison voltage is the lowest voltage across the filter capacitor.

[0008] The unidirectional electronic switch comprises a first resistor, a second resistor, a first diode and a first MOS tube, wherein the first diode is a voltage stabilizing diode, the first MOS tube is a PMOS tube, one end of the first resistor is a control end of the unidirectional electronic switch, the drain of the first MOS tube is the negative electrode of the unidirectional electronic switch circuit, the source of the first MOS tube, one end of the second resistor and the negative electrode of the first diode are connected and the connection end thereof is the positive electrode of the unidirectional electronic switch, the other end of the first resistor, the other end of the second resistor, the positive electrode of the first diode and the gate of the first MOS tube are connected; the unidirectional conduction circuit comprises a second diode, the second diode is a rectifier diode, the positive electrode of the second diode is the positive electrode of the unidirectional conduction circuit, and the negative electrode of the second diode is the negative electrode of the unidirectional conduction circuit. In the circuit, since a parasitic diode is provided between the source and drain of the first MOS tube, the positive and negative directions of the parasitic diode are consistent with the positive and negative directions of the second diode, the parasitic diode and the second diode are connected in parallel to form a unidirectional conduction circuit, and if the parasitic diode has sufficient pulse current carrying capacity, the second diode can be omitted. The circuit uses the conduction threshold voltage of the gate of the MOS tube and determines the magnitude of the second comparison voltage by setting the resistance ratio of the first resistor and the second resistor. The circuit is simple and low in cost, and the first end and the second end of the electronic switch circuit are turned on and off in a low-impedance switch state when they are turned on, so it has the advantage of low loss when the filter capacitor is charged and discharged.

[0009] The rectifier circuit includes a first full-bridge rectifier stack, a third diode and a third resistor, the third diode is a rectifier diode, the first full-bridge rectifier stack has two AC input terminals, a positive voltage output terminal and a negative voltage output terminal, the two AC input terminals of the first full-bridge rectifier stack serve as the first input terminal and the second input terminal of the rectifier circuit respectively, the positive voltage output terminal of the first full-bridge rectifier stack, one end of the third resistor and the positive electrode of the third diode are connected and the connection end is the instantaneous voltage terminal of the rectifier circuit, the cathode of the third diode is the positive output terminal of the rectifier circuit, the negative voltage output terminal of the first full-bridge rectifier stack is connected to the other end of the third resistor and the connection end is the negative output terminal of the rectifier circuit; the filter capacitor is a first electrolytic capacitor, the positive electrode of the first electrolytic capacitor is the positive electrode of the filter capacitor, and the negative electrode of the first electrolytic capacitor is the negative electrode of the filter capacitor.

[0010] The rectifier circuit has a first input terminal, a second input terminal, a positive output terminal, a negative output terminal and an instantaneous voltage terminal for outputting the instantaneous voltage of the mains. The constant current conversion circuit has a positive pole, a negative pole, a positive output terminal and a negative output terminal. The LED light-emitting circuit has a positive pole and a negative pole. The filter capacitor has a positive pole and a negative pole. The electronic switch circuit has a first terminal, a second terminal and a control terminal. The electronic switch circuit is provided with a first comparison voltage and a second comparison voltage. The first comparison voltage is greater than the second comparison voltage and less than the peak voltage of the mains. When the voltage connected to the control terminal of the electronic switch circuit is greater than or equal to the first comparison voltage, the electronic switch circuit is unidirectionally conducted from the first terminal to the second terminal. When the voltage connected to the control terminal of the electronic switch circuit is less than the second comparison voltage, the electronic switch circuit is unidirectionally conducted from the second terminal to the first terminal. When the voltage connected to the control end of the electronic switch circuit is greater than or equal to the second comparison voltage and less than the first comparison voltage, the first end and the second end of the electronic switch circuit are cut off, the positive output end of the rectifier circuit is connected to the positive electrode of the constant current conversion circuit, the negative output end of the rectifier circuit is connected to the negative electrode of the constant current conversion circuit, the positive output end of the constant current conversion circuit is connected to the positive electrode of the LED light-emitting circuit, the negative output end of the constant current conversion circuit is connected to the negative electrode of the LED light-emitting circuit, the positive output end of the rectifier circuit is connected to the positive electrode of the filter capacitor, the control end of the electronic switch circuit is connected to the instantaneous voltage end of the rectifier circuit, the first end of the electronic switch circuit is connected to the negative electrode of the filter capacitor, and the second end of the electronic switch circuit is connected to the negative output end of the rectifier circuit.In this structure, when the rectifier circuit is connected to the mains, the AC voltage of the mains is converted into a DC voltage. The maximum value of the voltage output between the positive output terminal and the negative output terminal of the rectifier circuit is the peak voltage of the mains, and the minimum value is 0, and it changes periodically in the form of a positive half-cycle of a sinusoidal wave. In a voltage change cycle, when the instantaneous voltage of the mains output by the rectifier circuit is greater than or equal to the first comparison voltage of the electronic switch circuit, the mains, after rectification, supplies power to the constant current conversion circuit on the one hand, and on the other hand, because the electronic switch circuit is unidirectionally conducted, the filter capacitor is charged. When the instantaneous voltage output by the mains after passing through the rectifier circuit is less than the first comparison voltage and greater than or equal to the second comparison voltage, the electronic switch circuit is cut off, and the mains voltage can neither charge the filter capacitor nor supply power to the constant current conversion circuit. At this time, only the mains voltage provides voltage for the constant current conversion circuit after passing through the rectifier circuit. When the instantaneous voltage output by the mains after passing through the rectifier circuit is less than the second comparison voltage, because the electronic switch circuit is unidirectionally conducted, the instantaneous voltage of the mains is lower than the voltage across the filter capacitor. At this time, the filter capacitor provides a working voltage for the constant current conversion circuit, while the mains cannot provide voltage for the constant current conversion circuit. Thus, the structure controls the extension of the duration of the input current in a mains voltage cycle through the electronic switch circuit, significantly improves the power factor, and makes the power factor of the mains supply current reach above 0.7. In addition, the voltage between the positive and negative electrodes of the constant current conversion circuit is maintained between the second comparison voltage and the peak value of the mains voltage. By adjusting the constant current conversion circuit, a low ripple current is output, thereby making the LED light-emitting circuit emit light with low frequency flicker.

[0011] The electronic switch circuit includes a unidirectional electronic switch and a unidirectional conduction circuit. The unidirectional electronic switch has a positive pole, a negative pole and a control terminal. When the positive pole and the negative pole of the unidirectional electronic switch are connected, the current direction is from the positive pole to the negative pole. When the current is reversed, the current flowing through the unidirectional electronic switch is zero. When the positive pole and the negative pole of the unidirectional electronic switch are cut off, no matter what the current direction between the positive pole and the negative pole is, the unidirectional electronic switch cannot flow current. The unidirectional conduction circuit has a positive pole and a negative pole. When the current direction is from the positive pole to the negative pole, the positive pole and the negative pole of the unidirectional conduction circuit When the current is reversed, the positive and negative electrodes of the one-way conducting circuit are cut off, the positive electrode of the one-way electronic switch is connected to the negative electrode of the one-way conducting circuit and the connection end thereof is the second end of the electronic switch circuit, the negative electrode of the one-way electronic switch is connected to the positive electrode of the one-way conducting circuit and the connection end thereof is the first end of the electronic switch circuit, the control end of the one-way electronic switch is the control end of the electronic switch circuit, the second comparison voltage is set in the internal circuit of the one-way electronic switch, and the magnitude of the first comparison voltage is the lowest voltage across the filter capacitor.

[0012] The unidirectional electronic switch comprises a fourth resistor, a fifth resistor, a fourth diode and a second MOS tube, wherein the fourth diode is a voltage stabilizing diode, the second MOS tube is an NMOS tube, one end of the fourth resistor is a control end of the unidirectional electronic switch circuit, the drain of the second MOS tube is the positive electrode of the unidirectional electronic switch circuit, the source of the second MOS tube, one end of the fifth resistor and the positive electrode of the fourth diode are connected and the connection end thereof is the negative electrode of the unidirectional electronic switch circuit, the other end of the fourth resistor, the other end of the fifth resistor, the negative electrode of the fourth diode and the gate of the second MOS tube are connected; the unidirectional conduction circuit comprises a fifth diode, the fifth diode is a rectifier diode, the positive electrode of the fifth diode is the positive electrode of the unidirectional conduction circuit, and the negative electrode of the fifth diode is the negative electrode of the unidirectional conduction circuit. In the circuit, since there is a parasitic diode between the source and the drain of the second MOS tube, the positive and negative directions of the parasitic diode are consistent with the positive and negative directions of the second diode, the parasitic diode and the second diode are connected in parallel to form a unidirectional conduction circuit. If the parasitic diode has sufficient pulse current carrying capacity, the fifth diode can be omitted. The circuit uses the conduction threshold voltage of the MOS gate and can determine the size of the second comparison voltage by setting the resistance ratio of the fourth resistor and the fifth resistor. The circuit is simple and low in cost. When the first end and the second end of the electronic switch circuit are turned on, they are turned on and off in a low-impedance switch state, so when the filter capacitor is charged and discharged, it has the advantage of low loss.

[0013] The rectifier circuit includes a second full-bridge rectifier stack, a sixth diode and a sixth resistor, the sixth diode is a rectifier diode, the second full-bridge rectifier stack has two AC input terminals, a positive voltage output terminal and a negative voltage output terminal, the two AC input terminals of the second full-bridge rectifier stack serve as the first input terminal and the second input terminal of the rectifier circuit respectively, the negative voltage output terminal of the second full-bridge rectifier stack, one end of the sixth resistor and the negative electrode of the sixth diode are connected and the connection end is the instantaneous voltage terminal of the rectifier circuit, the positive electrode of the sixth diode is the negative output terminal of the rectifier circuit, the positive voltage output terminal of the second full-bridge rectifier stack is connected to the other end of the sixth resistor and the connection end is the positive output terminal of the rectifier circuit, the filter capacitor is a second electrolytic capacitor, the positive electrode of the second electrolytic capacitor is the positive electrode of the filter capacitor, and the negative electrode of the second electrolytic capacitor is the negative electrode of the filter capacitor.

[0014] Compared with the prior art, the advantage of the present invention lies in that an electronic switch circuit is provided, which has two states, namely, on and off, and can be turned on or off according to the instantaneous voltage of the AC power, thereby reducing the discharge time of the filter capacitor and increasing the AC power supply time, thereby extending the duration of the input current in a AC power voltage cycle. On the basis of low cost, the power factor can be increased to greater than or equal to 0.7, meeting the technical requirements of subsequent products. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a circuit block diagram of an existing low-frequency flicker LED lamp circuit;

[0016] Figure 2 4 is a circuit block diagram of a low-frequency flicker LED lamp circuit according to Embodiment 1 of the present invention;

[0017] Figure 3 This is a circuit block diagram of a low-flicker LED lamp circuit according to Embodiment 2 of the present invention;

[0018] Figure 4 A circuit block diagram of an electronic switch circuit of a low-frequency flicker LED lamp circuit according to Embodiment 1 and Embodiment 2 of the present invention;

[0019] Figure 5 It is a partial circuit diagram of a low-frequency flicker LED lamp circuit according to the first embodiment of the present invention;

[0020] Figure 6 It is a partial circuit diagram of a low-flicker LED lamp circuit according to the second embodiment of the present invention. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below with reference to the accompanying drawings.

[0022] Embodiment 1: A low-frequency flicker LED lamp circuit includes a rectifier circuit for converting AC voltage of a mains into a DC voltage output, a filter capacitor for reducing the fluctuation range of the DC voltage output by the rectifier circuit, a constant current conversion circuit for converting the DC voltage output by the rectifier circuit into a constant current output, and an LED light-emitting circuit that can emit light under the drive of the constant current conversion circuit. The low-frequency flicker LED lamp circuit also includes an electronic switch circuit. The electronic switch circuit has two states, namely, on and off. It can be turned on or off according to the instantaneous voltage of the mains, thereby reducing the discharge time of the filter capacitor and increasing the mains power supply time.

[0023] In this embodiment, Figure 2As shown, the rectifier circuit has a first input terminal, a second input terminal, a positive output terminal, a negative output terminal and an instantaneous voltage terminal for outputting the instantaneous voltage of the mains, the constant current conversion circuit has a positive pole, a negative pole, a positive output terminal and a negative output terminal, the LED light-emitting circuit has a positive pole and a negative pole, the filter capacitor has a positive pole and a negative pole, the electronic switch circuit has a first terminal, a second terminal and a control terminal, and a first comparison voltage and a second comparison voltage are provided at the electronic switch circuit, the first comparison voltage is greater than the second comparison voltage and less than the peak voltage of the mains, when the voltage connected to the control terminal of the electronic switch circuit is greater than or equal to the first comparison voltage, the electronic switch circuit is unidirectionally conducted from the first terminal to the second terminal, and when the voltage connected to the control terminal of the electronic switch circuit is less than the second comparison voltage, the electronic switch circuit is unidirectionally conducted from the first terminal to the second terminal. The two ends are unidirectionally conducted to the first end. When the voltage connected to the control end of the electronic switch circuit is greater than or equal to the second comparison voltage and less than the first comparison voltage, the first end and the second end of the electronic switch circuit are cut off, the positive output end of the rectifier circuit is connected to the positive electrode of the constant current conversion circuit, the negative output end of the rectifier circuit is connected to the negative electrode of the constant current conversion circuit, the positive output end of the constant current conversion circuit is connected to the positive electrode of the LED light-emitting circuit, the negative output end of the constant current conversion circuit is connected to the negative electrode of the LED light-emitting circuit, the negative output end of the rectifier circuit is connected to the negative electrode of the filter capacitor, the control end of the electronic switch circuit is connected to the instantaneous voltage end of the rectifier circuit, the second end of the electronic switch circuit is connected to the positive electrode of the filter capacitor, and the first end of the electronic switch circuit is connected to the positive output end of the rectifier circuit.

[0024] In this embodiment, Figure 4 As shown, the electronic switch circuit includes a unidirectional electronic switch and a unidirectional conduction circuit. The unidirectional electronic switch has a positive pole, a negative pole and a control terminal. When the positive pole and the negative pole of the unidirectional electronic switch are connected, the current direction is from the positive pole to the negative pole. When the current is reversed, the current flowing through the unidirectional electronic switch is zero. When the positive pole and the negative pole of the unidirectional electronic switch are cut off, no matter what the current direction between the positive pole and the negative pole is, the unidirectional electronic switch cannot flow current. The unidirectional conduction circuit has a positive pole and a negative pole. When the current direction is from the positive pole to the negative pole, the unidirectional conduction circuit The positive and negative electrodes of the circuit are conductive, and when the current is reversed, the positive and negative electrodes of the unidirectional conductive circuit are cut off, the positive electrode of the unidirectional electronic switch is connected to the negative electrode of the unidirectional conductive circuit and the connection end thereof is the second end of the electronic switch circuit, the negative electrode of the unidirectional electronic switch is connected to the positive electrode of the unidirectional conductive circuit and the connection end thereof is the first end of the electronic switch circuit, the control end of the unidirectional electronic switch is the control end of the electronic switch circuit, the second comparison voltage is set in the internal circuit of the unidirectional electronic switch, and the magnitude of the first comparison voltage is the lowest voltage across the filter capacitor.

[0025] In this embodiment, Figure 5As shown, the unidirectional electronic switch includes a first resistor R1, a second resistor R2, a first diode D1 and a first MOS transistor Q1, the first diode D1 is a voltage stabilizing diode, the first MOS transistor Q1 is a PMOS transistor, one end of the first resistor R1 is a control end of the unidirectional electronic switch, the drain of the first MOS transistor Q1 is the negative electrode of the unidirectional electronic switch circuit, the source of the first MOS transistor Q1, one end of the second resistor R2 and the negative electrode of the first diode D1 are connected and the connection end thereof is the positive electrode of the unidirectional electronic switch, the other end of the first resistor R1, the other end of the second resistor R2, the positive electrode of the first diode D1 and the gate of the first MOS transistor Q1 are connected; the unidirectional conduction circuit includes a second diode D2, the second diode D2 is a rectifier diode, the positive electrode of the second diode D2 is the positive electrode of the unidirectional conduction circuit, and the negative electrode of the second diode D2 is the negative electrode of the unidirectional conduction circuit.

[0026] In this embodiment, Figure 5 As shown, the rectifier circuit includes a first full-bridge rectifier bridge stack Db1, a third diode D3 and a third resistor R3, the third diode D3 is a rectifier diode, the first full-bridge rectifier bridge stack Db1 has two AC input terminals, a positive voltage output terminal and a negative voltage output terminal, the two AC input terminals of the first full-bridge rectifier bridge stack Db1 serve as the first input terminal and the second input terminal of the rectifier circuit respectively, the positive voltage output terminal of the first full-bridge rectifier bridge stack Db1, one end of the third resistor R3 and the positive electrode of the third diode D3 are connected and the connection end thereof is the instantaneous voltage terminal of the rectifier circuit, the cathode of the third diode D3 is the positive output terminal of the rectifier circuit, the negative voltage output terminal of the first full-bridge rectifier bridge stack Db1 and the other end of the third resistor R3 are connected and the connection end thereof is the negative output terminal of the rectifier circuit; the filter capacitor is a first electrolytic capacitor C1, the positive electrode of the first electrolytic capacitor C1 is the positive electrode of the filter capacitor, and the negative electrode of the first electrolytic capacitor C1 is the negative electrode of the filter capacitor.

[0027] Embodiment 2: A low-frequency flicker LED lamp circuit includes a rectifier circuit for converting AC voltage of a mains into a DC voltage output, a filter capacitor for reducing the fluctuation range of the DC voltage output by the rectifier circuit, a constant current conversion circuit for converting the DC voltage output by the rectifier circuit into a constant current output, and an LED light-emitting circuit that can emit light under the drive of the constant current conversion circuit. The low-frequency flicker LED lamp circuit also includes an electronic switch circuit, which has two states of on and off, and can be turned on or off according to the instantaneous voltage of the mains, thereby reducing the discharge time of the filter capacitor and increasing the mains power supply time.

[0028] In this embodiment, Figure 3As shown, the rectifier circuit has a first input terminal, a second input terminal, a positive output terminal, a negative output terminal and an instantaneous voltage terminal for outputting the instantaneous voltage of the mains, the constant current conversion circuit has a positive pole, a negative pole, a positive output terminal and a negative output terminal, the LED light-emitting circuit has a positive pole and a negative pole, the filter capacitor has a positive pole and a negative pole, the electronic switch circuit has a first terminal, a second terminal and a control terminal, and a first comparison voltage and a second comparison voltage are provided at the electronic switch circuit, the first comparison voltage is greater than the second comparison voltage and less than the peak voltage of the mains, when the voltage connected to the control terminal of the electronic switch circuit is greater than or equal to the first comparison voltage, the electronic switch circuit is unidirectionally conducted from the first terminal to the second terminal, and when the voltage connected to the control terminal of the electronic switch circuit is less than the second comparison voltage, the electronic switch circuit is unidirectionally conducted from the first terminal to the second terminal. The two ends are unidirectionally conducted to the first end. When the voltage connected to the control end of the electronic switch circuit is greater than or equal to the second comparison voltage and less than the first comparison voltage, the first end and the second end of the electronic switch circuit are cut off, the positive output end of the rectifier circuit is connected to the positive electrode of the constant current conversion circuit, the negative output end of the rectifier circuit is connected to the negative electrode of the constant current conversion circuit, the positive output end of the constant current conversion circuit is connected to the positive electrode of the LED light-emitting circuit, the negative output end of the constant current conversion circuit is connected to the negative electrode of the LED light-emitting circuit, the positive output end of the rectifier circuit is connected to the positive electrode of the filter capacitor, the control end of the electronic switch circuit is connected to the instantaneous voltage end of the rectifier circuit, the first end of the electronic switch circuit is connected to the negative electrode of the filter capacitor, and the second end of the electronic switch circuit is connected to the negative output end of the rectifier circuit.

[0029] In this embodiment, Figure 4 As shown, the electronic switch circuit includes a unidirectional electronic switch and a unidirectional conduction circuit. The unidirectional electronic switch has a positive pole, a negative pole and a control terminal. When the positive pole and the negative pole of the unidirectional electronic switch are connected, the current direction is from the positive pole to the negative pole. When the current is reversed, the current flowing through the unidirectional electronic switch is zero. When the positive pole and the negative pole of the unidirectional electronic switch are cut off, no matter what the current direction between the positive pole and the negative pole is, the unidirectional electronic switch cannot flow current. The unidirectional conduction circuit has a positive pole and a negative pole. When the current direction is from the positive pole to the negative pole, the unidirectional electronic switch The positive and negative electrodes of the one-way conducting circuit are conductive, and when the current is reversed, the positive and negative electrodes of the one-way conducting circuit are cut off. The positive electrode of the one-way electronic switch is connected to the negative electrode of the one-way conducting circuit and the connection end thereof is the second end of the electronic switch circuit. The negative electrode of the one-way electronic switch is connected to the positive electrode of the one-way conducting circuit and the connection end thereof is the first end of the electronic switch circuit. The control end of the one-way electronic switch is the control end of the electronic switch circuit. The second comparison voltage is set in the internal circuit of the one-way electronic switch. The magnitude of the first comparison voltage is the lowest voltage across the filter capacitor.

[0030] In this embodiment, Figure 6As shown, the unidirectional electronic switch includes a fourth resistor R4, a fifth resistor R5, a fourth diode D4 and a second MOS transistor Q2, the fourth diode D4 is a voltage stabilizing diode, the second MOS transistor Q2 is an NMOS transistor, one end of the fourth resistor R4 is a control end of the unidirectional electronic switch circuit, the drain of the second MOS transistor Q2 is the positive electrode of the unidirectional electronic switch circuit, the source of the second MOS transistor Q2, one end of the fifth resistor R5 and the positive electrode of the fourth diode D4 are connected, and the connection end thereof is the negative electrode of the unidirectional electronic switch circuit, the other end of the fourth resistor R4, the other end of the fifth resistor R5 and the negative electrode of the fourth diode D4 are connected to the gate of the second MOS transistor Q2; the unidirectional conduction circuit includes a fifth diode D5, the fifth diode D5 is a rectifier diode, the positive electrode of the fifth diode D5 is the positive electrode of the unidirectional conduction circuit, and the negative electrode of the fifth diode D5 is the negative electrode of the unidirectional conduction circuit.

[0031] In this embodiment, Figure 6 As shown, the rectifier circuit includes a second full-bridge rectifier stack Db2, a sixth diode D6 and a sixth resistor R6, the sixth diode D6 is a rectifier diode, the second full-bridge rectifier stack Db2 has two AC input terminals, a positive voltage output terminal and a negative voltage output terminal, the two AC input terminals of the second full-bridge rectifier stack Db2 serve as the first input terminal and the second input terminal of the rectifier circuit respectively, the negative voltage output terminal of the second full-bridge rectifier stack Db2, one end of the sixth resistor R6 and the negative electrode of the sixth diode D6 are connected and the connection end thereof is the instantaneous voltage terminal of the rectifier circuit, the positive electrode of the sixth diode D6 is the negative output terminal of the rectifier circuit, the positive voltage output terminal of the second full-bridge rectifier stack Db2 and the other end of the sixth resistor R6 are connected and the connection end thereof is the positive output terminal of the rectifier circuit, the filter capacitor is the second electrolytic capacitor C2, the positive electrode of the second electrolytic capacitor C2 is the positive electrode of the filter capacitor, and the negative electrode of the second electrolytic capacitor C2 is the negative electrode of the filter capacitor.

Claims

1. A low-frequency LED lamp circuit, comprising a rectifier circuit for converting AC voltage of a mains into DC voltage output, a filter capacitor for reducing the fluctuation range of the DC voltage output by the rectifier circuit, a constant current conversion circuit for converting the DC voltage output by the rectifier circuit into a constant current output, and an LED light-emitting circuit capable of emitting light under the drive of the constant current conversion circuit, characterized in that The low-frequency strobe LED lamp circuit also includes an electronic switch circuit, which has two states: on and off, and can be turned on or off according to the instantaneous voltage of the mains, thereby reducing the discharge time of the filter capacitor and increasing the mains power supply time; The rectifier circuit has a first input terminal, a second input terminal, a positive output terminal, a negative output terminal and an instantaneous voltage terminal for outputting the instantaneous voltage of the mains. The constant current conversion circuit has a positive pole, a negative pole, a positive output terminal and a negative output terminal. The LED light-emitting circuit has a positive pole and a negative pole. The filter capacitor has a positive pole and a negative pole. The electronic switch circuit has a first terminal, a second terminal and a control terminal. The electronic switch circuit is provided with a first comparison voltage and a second comparison voltage. The first comparison voltage is greater than the second comparison voltage and less than the peak voltage of the mains. When the voltage connected to the control terminal of the electronic switch circuit is greater than or equal to the first comparison voltage, the electronic switch circuit conducts a unidirectional current from the first terminal to the second terminal. When the voltage connected to the control end of the electronic switch circuit is less than the second comparison voltage, the electronic switch circuit is unidirectionally connected from the second end to the first end; when the voltage connected to the control end of the electronic switch circuit is greater than or equal to the second comparison voltage and less than the first comparison voltage, the first end and the second end of the electronic switch circuit are cut off; the positive output end of the rectifier circuit is connected to the positive electrode of the constant current conversion circuit, the negative output end of the rectifier circuit is connected to the negative electrode of the constant current conversion circuit, the positive output end of the constant current conversion circuit is connected to the positive electrode of the LED light-emitting circuit, and the negative output end of the constant current conversion circuit is connected to the negative electrode of the LED light-emitting circuit; The negative output terminal of the rectifier circuit is connected to the negative electrode of the filter capacitor, the control terminal of the electronic switch circuit is connected to the instantaneous voltage terminal of the rectifier circuit, the second terminal of the electronic switch circuit is connected to the positive electrode of the filter capacitor, and the first terminal of the electronic switch circuit is connected to the positive output terminal of the rectifier circuit; or the positive output terminal of the rectifier circuit is connected to the positive electrode of the filter capacitor, the control terminal of the electronic switch circuit is connected to the instantaneous voltage terminal of the rectifier circuit, the first terminal of the electronic switch circuit is connected to the negative electrode of the filter capacitor, and the second terminal of the electronic switch circuit is connected to the negative output terminal of the rectifier circuit; The electronic switch circuit includes a unidirectional electronic switch and a unidirectional conduction circuit. The unidirectional electronic switch has a positive pole, a negative pole and a control terminal. When the positive pole and the negative pole of the unidirectional electronic switch are connected, the current direction is from the positive pole to the negative pole. When the current is reversed, the current flowing through the unidirectional electronic switch is zero. When the positive pole and the negative pole of the unidirectional electronic switch are cut off, no matter what the current direction between the positive pole and the negative pole is, the unidirectional electronic switch cannot flow current. The unidirectional conduction circuit has a positive pole and a negative pole. When the current direction is from the positive pole to the negative pole, the positive pole and the negative pole of the unidirectional conduction circuit are connected. When the current is reversed, the positive and negative electrodes of the one-way conducting circuit are cut off, the positive electrode of the one-way electronic switch is connected to the negative electrode of the one-way conducting circuit and the connection end thereof is the second end of the electronic switch circuit, the negative electrode of the one-way electronic switch is connected to the positive electrode of the one-way conducting circuit and the connection end thereof is the first end of the electronic switch circuit, the control end of the one-way electronic switch is the control end of the electronic switch circuit, the second comparison voltage is set in the internal circuit of the one-way electronic switch, and the magnitude of the first comparison voltage is the lowest voltage across the filter capacitor.

2. A low-flicker LED lamp circuit according to claim 1, characterized in that When the negative output end of the rectifier circuit is connected to the negative electrode of the filter capacitor, the control end of the electronic switch circuit is connected to the instantaneous voltage end of the rectifier circuit, the second end of the electronic switch circuit is connected to the positive electrode of the filter capacitor, and the first end of the electronic switch circuit is connected to the positive output end of the rectifier circuit, the unidirectional electronic switch includes a first resistor, a second resistor, a first diode and a first MOS tube, the first diode is a voltage regulator diode, the first MOS tube is a PMOS tube, one end of the first resistor is the control end of the unidirectional electronic switch, the drain of the first MOS tube is the negative electrode of the unidirectional electronic switch circuit, the source of the first MOS tube, one end of the second resistor and the negative electrode of the first diode are connected and the connection end is the positive electrode of the unidirectional electronic switch, the other end of the first resistor, the other end of the second resistor, the positive electrode of the first diode and the gate of the first MOS tube are connected; the unidirectional conduction circuit includes a second diode, the second diode is a rectifier diode, the positive electrode of the second diode is the positive electrode of the unidirectional conduction circuit, and the negative electrode of the second diode is the negative electrode of the unidirectional conduction circuit.

3. A low-flicker LED lamp circuit according to claim 2, characterized in that The rectifier circuit includes a first full-bridge rectifier stack, a third diode and a third resistor, the third diode is a rectifier diode, the first full-bridge rectifier stack has two AC input terminals, a positive voltage output terminal and a negative voltage output terminal, the two AC input terminals of the first full-bridge rectifier stack serve as the first input terminal and the second input terminal of the rectifier circuit respectively, the positive voltage output terminal of the first full-bridge rectifier stack, one end of the third resistor and the positive electrode of the third diode are connected and the connection end is the instantaneous voltage terminal of the rectifier circuit, the cathode of the third diode is the positive output terminal of the rectifier circuit, the negative voltage output terminal of the first full-bridge rectifier stack is connected to the other end of the third resistor and the connection end is the negative output terminal of the rectifier circuit; the filter capacitor is a first electrolytic capacitor, the positive electrode of the first electrolytic capacitor is the positive electrode of the filter capacitor, and the negative electrode of the first electrolytic capacitor is the negative electrode of the filter capacitor.

4. A low-flicker LED lamp circuit according to claim 1, characterized in that When the positive output end of the rectifier circuit is connected to the positive electrode of the filter capacitor, the control end of the electronic switch circuit is connected to the instantaneous voltage end of the rectifier circuit, the first end of the electronic switch circuit is connected to the negative electrode of the filter capacitor, and the second end of the electronic switch circuit is connected to the negative output end of the rectifier circuit, the unidirectional electronic switch includes a fourth resistor, a fifth resistor, a fourth diode and a second MOS transistor, the fourth diode is a voltage regulator diode, the second MOS transistor is an NMOS transistor, one end of the fourth resistor is the control end of the unidirectional electronic switch circuit, the drain of the second MOS transistor is the positive electrode of the unidirectional electronic switch circuit, the source of the second MOS transistor, one end of the fifth resistor and the positive electrode of the fourth diode are connected and the connection end is the negative electrode of the unidirectional electronic switch circuit, the other end of the fourth resistor, the other end of the fifth resistor, the negative electrode of the fourth diode and the gate of the second MOS transistor are connected; the unidirectional conduction circuit includes a fifth diode, the fifth diode is a rectifier diode, the positive electrode of the fifth diode is the positive electrode of the unidirectional conduction circuit, and the negative electrode of the fifth diode is the negative electrode of the unidirectional conduction circuit.

5. A low-flicker LED lamp circuit according to claim 4, characterized in that The rectifier circuit includes a second full-bridge rectifier stack, a sixth diode and a sixth resistor, the sixth diode is a rectifier diode, the second full-bridge rectifier stack has two AC input terminals, a positive voltage output terminal and a negative voltage output terminal, the two AC input terminals of the second full-bridge rectifier stack serve as the first input terminal and the second input terminal of the rectifier circuit respectively, the negative voltage output terminal of the second full-bridge rectifier stack, one end of the sixth resistor and the negative electrode of the sixth diode are connected and the connection end is the instantaneous voltage terminal of the rectifier circuit, the positive electrode of the sixth diode is the negative output terminal of the rectifier circuit, the positive voltage output terminal of the second full-bridge rectifier stack is connected to the other end of the sixth resistor and the connection end is the positive output terminal of the rectifier circuit, the filter capacitor is a second electrolytic capacitor, the positive electrode of the second electrolytic capacitor is the positive electrode of the filter capacitor, and the negative electrode of the second electrolytic capacitor is the negative electrode of the filter capacitor.

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