Dimming signal conversion circuit and LED lamp

Abstract

The utility model provides a dimming signal conversion circuit and an LED lamp, and the dimming signal conversion circuit comprises a voltage division module which is composed of a plurality of resistors, and one end of the voltage division module is used for accessing a PWM signal; one end of the high-frequency filter capacitor is electrically connected with the other end of the voltage division module, and the other end is grounded; the RC delay module comprises a delay resistor and a low-frequency filter capacitor; one end of the delay resistor is electrically connected with the other end of the voltage division module, and the other end is connected with a driving circuit; one end of the low-frequency filter capacitor is connected with the other end of the delay resistor, and the other end of the low-frequency filter capacitor is grounded; and the capacitance value of the low-frequency filter capacitor is 2.2-10 uF. According to the utility model, the input PWM signal is converted into a smooth and continuously changing regular waveform through the dimming signal conversion circuit, the working duty ratio of the driving circuit can be increased, and in each period, the driving circuit performs dimming action with a small floating range according to an analog level, so that the howling noise during dimming can be effectively reduced, and the dimming effect is improved. And the minimum brightness of dimming can be reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of LED lamps, and in particular to a dimming signal conversion circuit and an LED lamp. Background Art

[0002] Lighting, particularly LED (Light Emitting Diode) lamps, plays a vital role in our lives and work. In practice, people often need to adjust the brightness of LED lamps based on the specific application scenario. Some known LED lamp dimming solutions adjust the brightness of the LED lamp's light source by adjusting the duty cycle of a control signal (such as a PWM signal).

[0003] For the dimming method that adjusts the duty cycle of the PWM signal, the larger the PWM signal's duty cycle, the longer its effective duration, and the corresponding brighter the LED lamp's brightness. However, this dimming method has a "dimming dead zone." In this "dimming dead zone," the LED lamp's brightness does not change with changes in the PWM duty cycle, so the LED lamp's dimming depth cannot be achieved very deeply, for example, the dimming depth cannot reach below 10%.

[0004] To further increase the dimming depth, one feasible approach is to reduce the frequency of the PWM signal. This can significantly improve the dimming depth, but the current on the load will ripple, which can cause the LED lamp to flicker and fail to maintain stable lighting. Utility Model Content

[0005] In view of this, an object of the present invention is to provide a dimming signal conversion circuit and an LED lamp to improve the above-mentioned problem.

[0006] A dimming signal conversion circuit, used for converting a received PWM signal into an analog level and then outputting the analog level, comprising:

[0007] The voltage divider module is composed of several resistors, one end of which is used to connect to the PWM signal;

[0008] a high-frequency filter capacitor, one end of which is electrically connected to the other end of the voltage divider module and the other end of which is grounded;

[0009] The RC delay module includes a delay resistor and a low-frequency filter capacitor; one end of the delay resistor is electrically connected to the other end of the voltage divider module, and the other end is used to connect to the drive circuit; one end of the low-frequency filter capacitor is connected to the other end of the delay resistor, and the other end of the low-frequency filter capacitor is grounded; and the capacitance value of the low-frequency filter capacitor is 2.2-10uF.

[0010] Preferably, the voltage divider module includes a first resistor and a second resistor, one end of the first resistor is used to access the PWM signal, and the other end is connected to one end of the second resistor, one end of the high-frequency filter capacitor and one end of the delay resistor; the other end of the second resistor is grounded.

[0011] Preferably, the resistance of the first resistor is 47 ohms, and the resistance of the second resistor is 1K ohms.

[0012] Preferably, the capacitance value of the high-frequency filter capacitor C1 is 0.1 uF.

[0013] Preferably, the resistance of the delay resistor is 2.2K ohms.

[0014] Preferably, the waveform of the analog level is a smooth, constantly changing regular waveform.

[0015] An embodiment of the present invention also provides an LED lamp, which includes a dimming controller for outputting a PWM signal, a driving circuit, an LED light source, and a dimming signal conversion circuit as described above; wherein the dimming controller, the dimming signal conversion circuit, the driving circuit, and the LED light source are electrically connected in sequence, and the dimming signal conversion circuit is suitable for receiving the PWM signal output by the dimming controller and converting it into an analog level and outputting it to the driving circuit.

[0016] Preferably, the frequency of the PWM signal is 100-500 Hz.

[0017] To summarize, this embodiment converts the input PWM signal into a smooth, constantly changing regular waveform through the dimming signal conversion circuit, and then uses the smooth, constantly changing regular waveform to control the driving circuit, which can increase the duty cycle of the driving circuit and allow the driving circuit to be in working state most of the time. In each cycle, the driving circuit performs dimming actions with a very small floating range according to the constantly changing analog level, which can effectively reduce the howling noise during dimming and reduce the minimum dimming brightness. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 This is a circuit diagram of a dimming signal conversion circuit provided by the first embodiment of the present utility model.

[0020] Figure 2It is a structural diagram of an LED lamp provided by the second embodiment of the present utility model.

[0021] Figure 3 A waveform diagram of an analog level provided in the first embodiment of the present invention.

[0022] Figure 4 for Figure 3 Waveform characteristic diagram of the analog level. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the utility model for which protection is sought, but merely represents the selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0024] See also Figure 1 The first embodiment of the present invention provides a dimming signal conversion circuit, which is suitable for being arranged between a dimming controller and a driving circuit, and converting a PWM signal received from the dimming controller into an analog level and outputting the analog level to the driving circuit, and includes:

[0025] The voltage divider module is composed of several resistors, one end of which is used to access the PWM signal.

[0026] Specifically, the voltage dividing module includes a first resistor R1 and a second resistor R2.

[0027] A high-frequency filter capacitor C1, one end of which is electrically connected to the other end of the voltage divider module and the other end of which is grounded;

[0028] The RC delay module includes a delay resistor R3 and a low-frequency filter capacitor C2; one end of the delay resistor R3 is electrically connected to the other end of the voltage divider module, and the other end is used to connect to the drive circuit; one end of the low-frequency filter capacitor C2 is connected to the other end of the delay resistor R3, and the other end of the low-frequency filter capacitor C2 is grounded; and the capacitance value of the low-frequency filter capacitor C2 is 2.2-10uF.

[0029] In this embodiment, one end of the first resistor R1 is used to receive the PWM signal, and the other end is connected to one end of the second resistor R2, one end of the high-frequency filter capacitor C1 and one end of the delay resistor R3; the other end of the second resistor R2 is grounded.

[0030] In particular, in one possible implementation of the present invention, the resistance of the first resistor R1 is 47 ohms, the resistance of the second resistor R2 is 1K ohms, the capacitance of the high-frequency filter capacitor C1 is 0.1 uF, and the resistance of the delay resistor R3 is 2.2K ohms.

[0031] Of course, in other embodiments of the present invention, the resistance values ​​of the above-mentioned resistors and the capacitance values ​​of the capacitors can be adjusted according to actual needs, and the present invention does not make specific limitations.

[0032] See also Figure 2 The second embodiment of the present invention further provides an LED lamp, which includes a dimming controller 210 for outputting a PWM signal, a driving circuit 230, an LED light source 240, and a dimming signal conversion circuit 210 as in any of the above embodiments; wherein the dimming controller 210, the dimming signal conversion circuit 220, the driving circuit 230, and the LED light source 240 are electrically connected in sequence, and the dimming signal conversion circuit 220 is suitable for receiving the PWM signal output by the dimming controller 210, and converting it into an analog level and outputting it to the driving circuit 230.

[0033] Preferably, the frequency of the PWM signal output by the dimming controller 210 is 100-500 Hz.

[0034] The detailed working principle of this embodiment is described in detail below.

[0035] In this embodiment, the analog voltage level received by the driver circuit 230 ranges from 0.25V to 2.3V. When the voltage is ≥ 2.3V, the brightness is 100%. When the voltage is < 0.25V, the LED light source 240 turns off. When the duty cycle is 100%, the voltage divided by the first resistor R1 and the second resistor R2 must be close to 2.3V. This ensures that the corresponding brightness of the LED light source 240 is 100%, while also ensuring that the voltage drops below 2.3V quickly after dimming begins, allowing the brightness of the light source to change synchronously. At this time, because the duty cycle of the PWM signal is large and there is no ripple, the filtering effect of the high-frequency filter capacitor C1 and the low-frequency filter capacitor C2 is not significant.

[0036] When the duty cycle of the PWM signal begins to decrease, the PWM signal generates ripples. The high-frequency filter capacitor C1 and the low-frequency filter capacitor C2 start to filter out the high frequency and C2 filters out the low frequency, thereby compensating for the ripples generated by the PWM signal.

[0037] However, since the frequency of the PWM signal in this embodiment is relatively low, such as between 100Hz-500Hz, the ripple generated by the PWM signal is relatively large, and C1 and C2 cannot completely compensate for the ripple. However, since the capacitance of C2 is relatively large (2.2-10uF), the analog level output to the driving circuit 230 after the conversion is completed can be a smooth, constantly changing regular waveform. This embodiment utilizes the characteristic of not being able to completely compensate for the ripple to achieve specific dimming.

[0038] Specifically, if Figure 3 As shown, in this embodiment, the smooth and constantly changing regular waveform is roughly a triangular wave, and its changing pattern can be calculated based on the duty cycle of the PWM signal at that time and the ratio of R1 and R2 and the delay formula of R3 and C2:

[0039] t=Vpwm*D*(R2 / (R1+R2))*R3*C2*ln((Vpwm*D*(R2 / (R1+R2))-Vth) / Vpw m*D*(R2 / (R1+R2)))

[0040] Where t is the delay time, Vpwm is the voltage of the PWM signal, usually 3.3V, D is the real-time duty cycle, and Vth is the preset dimming voltage, which can be positioned at any value between 0.15-0.7V. This value is the average value of the analog voltage.

[0041] This smooth, constantly changing regular waveform has the following characteristic parameters:

[0042] Maximum value - Vmax, minimum value - Vmin, opening time - Ton, closing time - Toff, switching threshold - Vth, usually 4ms≤(Ton+Toff)≤10ms, frequency f range is between 100Hz-250Hz (if the frequency is too high, the driving circuit 230 will not have time to respond, and there will be relatively large howling noise).

[0043] When the analog level is greater than Vth: from Vth to Vmax and then to Vth, the driving circuit 230 is turned on and the duty cycle of the driving circuit 230 is adjusted according to the real-time value of the analog level.

[0044] When the analog level value is less than Vth, the driving circuit 230 is turned off;

[0045] According to the above control method, there are two advantages:

[0046] 1. Compared with the conventional PWM direct dimming method, the duty cycle Toff / (Ton+Toff) of the off state in each cycle in this embodiment is very small, which can optimize the noise problem of PWM dimming.

[0047] 2. Compared with conventional analog level dimming or PWM to analog level dimming, this embodiment can make the minimum brightness that the driving circuit 230 can adjust lower by adjusting parameters such as Vmax, Ton, Toff. For example, the light is usually turned off when the voltage is lower than 0.25V, corresponding to a brightness of 5%. However, when this embodiment uses an analog level with a smooth and constantly changing regular waveform for dimming, the minimum brightness that can be adjusted can be reduced to 2%.

[0048] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A dimming signal conversion circuit, used for converting a received PWM signal into an analog level and then outputting it, characterized in that: include: The voltage divider module is composed of several resistors, one end of which is used to connect to the PWM signal; a high-frequency filter capacitor, one end of which is electrically connected to the other end of the voltage divider module and the other end of which is grounded; The RC delay module includes a delay resistor and a low-frequency filter capacitor; one end of the delay resistor is electrically connected to the other end of the voltage divider module, and the other end is used to connect to the drive circuit; one end of the low-frequency filter capacitor is connected to the other end of the delay resistor, and the other end of the low-frequency filter capacitor is grounded; and the capacitance value of the low-frequency filter capacitor is 2.2-10uF.

2. The dimming signal conversion circuit according to claim 1, wherein: The voltage divider module includes a first resistor and a second resistor, one end of the first resistor is used to receive the PWM signal, and the other end is connected to one end of the second resistor, one end of the high-frequency filter capacitor and one end of the delay resistor; the other end of the second resistor is grounded.

3. The dimming signal conversion circuit according to claim 2, wherein: The resistance of the first resistor is 47 ohms, and the resistance of the second resistor is 1K ohms.

4. The dimming signal conversion circuit according to claim 1, wherein: The capacitance value of the high-frequency filter capacitor C1 is 0.1 uF.

5. The dimming signal conversion circuit according to claim 1, wherein: The resistance of the delay resistor is 2.2K ohms.

6. An LED lamp, characterized in that: It includes a dimming controller for outputting a PWM signal, a driving circuit, an LED light source, and a dimming signal conversion circuit as described in any one of claims 1 to 5; wherein the dimming controller, the dimming signal conversion circuit, the driving circuit, and the LED light source are electrically connected in sequence, and the dimming signal conversion circuit is suitable for receiving the PWM signal output by the dimming controller and converting it into an analog level and outputting it to the driving circuit.

7. The LED lamp according to claim 6, characterized in that: The frequency of the PWM signal is 100-500 Hz.

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