Variable frequency dimming high-precision optocoupler circuit and driving power supply thereof

Abstract

The application discloses a high-precision optocoupler circuit for frequency conversion and dimming and a dimming power supply thereof. The high-precision optocoupler circuit for frequency conversion and dimming comprises an optocoupler unit, a PWM operational amplifier unit, a dimming signal processing unit and a control unit. The optocoupler unit is used for isolating a primary side and a secondary side. The PWM operational amplifier unit is connected with the optocoupler unit. The dimming signal processing unit is arranged on the secondary side of a driving power supply and connected with the control unit. The control unit is used for frequency compensation. In the application, the control unit is used for acquiring reference voltages and a reference voltage under different input voltages, and the frequency adjustment method of output PWM is used for compensation, so that the dimming precision is realized under high-voltage input and low-voltage input and under dynamic change of a load.

Description

Technical Field

[0001] This invention relates to the field of LED lighting driver power supplies, specifically to a high-precision optocoupler circuit for frequency conversion dimming and its driver power supply. Background Technology

[0002] With the development of LED technology, LED technology has been widely used in lighting. "Dimmability" is a very important advantage of LED light sources compared to traditional light sources. Not only can it achieve dimming, but due to its small size, it can also achieve ultra-low depth and high precision dimming on the basis of traditional light sources. Therefore, dimmable LED lamps have the most widespread application function. However, dimming also puts forward high reliability dimming requirements on the power supply, such as 0-10V dimming, which is most widely used in North America and Europe.

[0003] The main factors affecting dimming are as follows: Within the full voltage input range of 108-380Vac, it's difficult to achieve high-precision dimming while simultaneously ensuring fast low-voltage start-up and high-voltage load regulation. Firstly, different input voltages affect the optocoupler's operating frequency, thus impacting the transfer ratio and leading to inaccurate dimming at low and high voltage inputs. Secondly, the transformer's core inductance is crucial. While prioritizing the conversion efficiency between low and high voltages during power regulation, it's also essential to consider the significant deviation in input power resulting from the combined linear and load regulation due to changes in load voltage during color temperature adjustment. This could potentially violate North American Energy Star regulations. For PSR flyback power supplies, this further deviates the voltage across the primary auxiliary winding, resulting in a voltage drop to the optocoupler that is either too high or too low. This leads to varying current flows through the optocoupler, causing corresponding rise time deviations and ultimately resulting in a higher dimming frequency. These issues necessitate further optimization of the driver power supply to achieve optimal dimming performance.

[0004] To address the aforementioned issues, existing LED driver power supplies need improvement and enhancement to solve the problem of high-precision dimming under full voltage input, multiple power adjustments, and color tuning. Summary of the Invention

[0005] In view of this, the present invention provides a high-precision optocoupler circuit for frequency conversion dimming and its driving power supply, which is used to solve the problem of low efficiency of existing LED driving power supply solutions in the context of large voltage input, multiple power output and high dimming accuracy requirements. While meeting the requirements of efficiency and high-precision dimming, the present invention solves the problem of poor dimming adjustment rate at high and low voltages due to large voltage spans by means of frequency adjustment.

[0006] Based on the overall concept of the invention, the technical solution is as follows:

[0007] A high-precision optocoupler circuit for frequency conversion dimming includes:

[0008] An optocoupler unit includes an optocoupler for isolating the primary side and the secondary side, wherein the input terminal of the optocoupler is located on the secondary side of the driving power supply, and the output terminal of the optocoupler is located on the primary side of the driving power supply.

[0009] The PWM operational amplifier unit, which is connected to the optocoupler unit, is used to collect feedback signals at different input voltages and send them to the control unit. It can respond to changes in the input voltage in real time and output a corresponding reference voltage.

[0010] The dimming signal processing unit is located on the secondary side of the drive power supply and connected to the control unit. It is used to preprocess the externally input 0-10V dimming signal or PWM signal and transmit the preprocessed dimming signal to the control unit.

[0011] The control unit is located on the secondary side of the drive power supply and is connected to the optocoupler unit and the PWM operational amplifier unit respectively. It is used to determine the input signal of the PWM operational amplifier unit and output the dimming signal with the corresponding frequency and duty cycle. It is also used to analyze the pre-processed dimming signal sent by the dimming signal processing unit and send the dimming signal to the input terminal of the optocoupler unit according to the input signal of the PWM operational amplifier unit and after corresponding frequency compensation.

[0012] The present invention also includes the following method for frequency conversion dimming:

[0013] S1: Obtain the reference voltages for the lowest and highest input voltages collected by the PWM operational amplifier unit;

[0014] S2: Calculate the input voltage difference coefficient and output load ratio coefficient based on the reference of the lowest and highest input voltages;

[0015] S3: Obtain the reference voltage when the input voltage is at the center value;

[0016] S4: The control unit sets the PWM frequency corresponding to the reference voltage output to the optocoupler;

[0017] S5: Perform frequency compensation based on the input voltage difference coefficient at different input voltages.

[0018] The present invention also provides a driving power supply including the above-described high-precision optocoupler circuit for frequency conversion dimming and a method for frequency conversion dimming.

[0019] The beneficial effects that the technical solution provided by the present invention can achieve are as follows:

[0020] 1. This invention addresses the issue that voltage fluctuations in the auxiliary power supply windings of the primary and secondary sides under different input voltages can cause changes in the duty cycle and frequency of the output from a traditional 0-10V dimming chip to the optocoupler as the input voltage and output load dynamically change. This results in inaccurate dimming under high and low voltage inputs, heavy loads, and light loads. In this invention, a control unit acquires reference voltages and a base reference voltage for different input voltages, and compensates for this by adjusting the frequency of the output PWM, thereby achieving accurate dimming under high and low voltage inputs and dynamic load changes.

[0021] 2. Replacing the dimming chip with a control unit not only makes dimming more precise, but also integrates more functions such as color adjustment. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings required in the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0023] Figure 1 This is a structural diagram of a high-precision optocoupler circuit for frequency conversion dimming provided in an embodiment of the present invention;

[0024] Figure 2 This invention provides a method for frequency conversion dimming according to an embodiment of the present invention. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Please see Figure 1 The high-precision optocoupler circuit for frequency conversion dimming described in this embodiment includes:

[0027] The optocoupler unit includes an optocoupler U1, used to isolate the primary and secondary sides of the driving power supply. The input terminal of the optocoupler is located on the secondary side of the driving power supply, and the output terminal is located on the primary side. The transmission ratio of the optocoupler is 300. A resistor R1 controls the rising edge of the duty cycle received by the optocoupler. When this resistor increases, the current flowing through it decreases. This results in a longer rising edge, leading to a larger pulse width amplitude within the same pulse width time, thus reducing the high-level time and consequently lowering the duty cycle. A resistor R2 limits the current input to the optocoupler, thereby changing the transmission ratio coefficient of the optocoupler.

[0028] The PWM operational amplifier unit, connected to the optocoupler unit, includes resistors R3, R4, and R5, as well as operational amplifier U2. Resistors R3 and R4 form a basic acquisition circuit for obtaining changes in input voltage and output load. Resistor R5 and operational amplifier U2 constitute a feedback signal for acquiring different input voltages and sending it to the control unit. The changing voltage is reflected in resistors R4 and R5 as a change in resistance R5, thus enabling real-time response to changes in input voltage and outputting a corresponding reference voltage.

[0029] The dimming signal processing unit, located on the secondary side of the drive power supply and connected to the control unit, is used to preprocess externally input 0-10V dimming signals or PWM signals. When the preprocessed signal is 0-10V, it filters the corresponding voltage signal into an amplitude signal and transmits the preprocessed dimming signal to the control unit. When the preprocessed signal is a PWM amplitude signal, it transmits the signal directly to the control unit without amplitude change.

[0030] The control unit is located on the secondary side of the drive power supply and is connected to the optocoupler unit and the PWM operational amplifier unit respectively. It collects the reference voltage emitted by the PWM operational amplifier unit, performs pre-judgment processing based on the reference voltage, and outputs a dimming signal with PWM frequency and duty cycle corresponding to the input voltage to the input terminal of the optocoupler unit. For specific implementation, see the following variable frequency dimming method.

[0031] The control unit is also used to parse the pre-processed dimming signal sent by the dimming signal processing unit, and send the dimming signal to the input terminal of the optocoupler unit according to the input signal of the PWM operational amplifier unit and after corresponding frequency compensation.

[0032] The present invention also includes the following method for frequency conversion dimming:

[0033] S1: Obtain the reference voltages for the lowest and highest input voltages acquired by the PWM operational amplifier unit; let REF_L be the reference voltage for the lowest input voltage and REF_H be the reference voltage for the highest input voltage.

[0034] S2: Calculate the input voltage difference coefficient and output load ratio coefficient based on the reference of the minimum and maximum input voltages; the minimum reference voltage is REF_L, and the maximum reference voltage is REF_H. The input voltage difference coefficient REF_CO = ((REF_H-REF_L) / (REF_H)+(REF_L) / (REF_H-REF_L)) / 2, the turns ratio of the primary and secondary auxiliary windings is K, the maximum output voltage is Vup, and the minimum output voltage is Vdown. Then the corresponding output load ratio coefficient REF_LO = (10×K) / (1.5×(V_up-V_down)).

[0035] In the above steps, the minimum input voltage is 108V, the maximum input voltage is 305V, the maximum output voltage is 45V, and the minimum output voltage is 30V. Based on the above steps, the input voltage difference coefficient is 0.65, and the output load ratio coefficient is 0.222-0.226.

[0036] S3: Obtain the reference voltage REF_S when the input voltage is at the center value = (REF_H-REF_L) / 2×REF_LO;

[0037] S4: The control unit sets the reference voltage to correspond to the PWM frequency output to the optocoupler, PWM_S = 800~900Hz;

[0038] S5: Frequency compensation is performed based on the input voltage difference coefficient for different input or output voltages. Because some power supplies use external undervoltage protection circuits under different input voltages, the VCC voltage to the chip varies due to the constant resistance value. Even with linear voltage regulation, voltage instability still exists on the chip's power supply pins, causing fluctuations in the internal voltage amplitude reference of the chip with a digital dimming port, leading to "false judgments." This false judgment is further caused by significant amplitude fluctuations in the PWM duty cycle signal transmitted from the secondary side via the optocoupler, resulting in amplitude changes in the PWM waveform entering the primary side chip. Therefore, under varying input or output voltages, frequency compensation is performed based on the PWM frequency output to the optocoupler input corresponding to the reference voltage. The PWM frequency output to the optocoupler corresponding to the reference voltage is set to PWM_S = 850Hz.

[0039] S5a: When performing frequency compensation based on the input voltage difference coefficient, if the reference voltage REF_NO corresponding to the current input voltage is lower than the reference voltage REF_S, the PWM frequency output to the input terminal of the optocoupler is (REF_S-REF_NO)×REF_CO×10×(850)+850.

[0040] S5b: When the reference voltage REF_NO corresponding to the current input voltage is higher than the reference voltage REF_S, the PWM frequency output to the input terminal of the optocoupler is 850-(REF_NO-REF_S)×REF_CO×10×(850).

[0041] The present invention also provides a driving power supply including the above-described high-precision optocoupler circuit for frequency conversion dimming and a method for frequency conversion dimming.

[0042] The above are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be regarded as limitations on the present invention. Several equivalent transformations, improvements and modifications can be made without departing from the concept of the present invention. These equivalent transformations, improvements and modifications should also be regarded as the protection scope of the present invention. Here, the embodiments will not be repeated. The protection scope of the present invention should be determined by the scope defined in the claims.

Claims

1. A high-precision optocoupler circuit for frequency conversion dimming, comprising: an optocoupler unit comprising an optocoupler for isolating a primary side from a secondary side, wherein an input end of the optocoupler is arranged at the secondary side of a driving power supply, and an output end of the optocoupler is arranged at the primary side of the driving power supply; a PWM operational amplifier unit connected to the optocoupler unit; a dimming signal processing unit arranged at the secondary side of the driving power supply; a control unit arranged at the secondary side of the driving power supply, and connected to the optocoupler unit, the PWM operational amplifier unit, and the dimming signal processing unit, respectively; characterized in that the control unit is configured to perform the following steps to achieve frequency conversion dimming: S1: obtaining a reference voltage REF_L at a lowest input voltage and a reference voltage REF_H at a highest input voltage collected by the PWM operational amplifier unit; S2: calculating an input voltage difference coefficient REF_CO and an output load proportion coefficient REF_LO according to the reference voltages REF_L and REF_H; S3: obtaining a reference reference voltage REF_S at a center value of the input voltage; S4: setting a reference PWM frequency PWM_S output to the optocoupler corresponding to the reference reference voltage REF_S; and S5: when a reference voltage REF_NO corresponding to a current input voltage is obtained, if the reference voltage REF_NO is different from the reference reference voltage REF_S, performing a compensation operation on the reference PWM frequency PWM_S according to the input voltage difference coefficient REF_CO calculated in step (S2) to generate and output a compensated PWM frequency to the input end of the optocoupler unit. In step S2, the calculation formulas of the input voltage difference coefficient REF_CO and the output load proportion coefficient REF_LO are: REF_CO = ((REF_H - REF_L) / (REF_H) + (REF_L) / (REF_H - REF_L)) / 2; and REF_LO = (10 × K) / (1.5 × (Vup - Vdown)), where K is the turn ratio of the primary-secondary auxiliary winding, Vup is the maximum output voltage, and Vdown is the minimum output voltage.

2. The high-precision optocoupler circuit of claim 1, wherein, In step S3, the calculation formula of the reference reference voltage REF_S is: REF_S = ((REF_H - REF_L) / 2) × REF_LO.

3. The high-precision optocoupler circuit of claim 2, wherein, ​ 4. The high-precision optocoupler circuit of claim 3, wherein, The compensation operation in the step S5 includes: when the reference voltage REF_NO corresponding to the current input voltage is lower than the reference voltage REF_S, the PWM frequency output to the optocoupler input end is (REF_S-REF_NO)×REF_CO×10×(PWM_S)+PWM_S; when the reference voltage REF_NO corresponding to the current input voltage is higher than the reference voltage REF_S, the PWM frequency output to the optocoupler input end is PWM_S-(REF_NO-REF_S)×REF_CO×10×(PWM_S).

5. A drive power supply characterized by comprising: The high-precision optocoupler circuit of frequency conversion dimming comprises the optocoupler circuit according to any one of claims 1 to 4.

Images