CN114501720A - Control method and device for stable output of cold light source - Google Patents

The application provides a control method and a device for stable output of a cold light source, belonging to the technical field of medical cold light sources, and the method comprises the following steps: acquiring a preset value; acquiring a current value, a temperature value and an optical power value; and obtaining stable optical power output through calculation and data processing. After the working mode is determined, the current adjustment precision is improved and the stability of the current is ensured by the cooperation of the analog voltage and the PWM duty ratio; the effective temperature value is calculated and obtained, the rotating speed of the fan is adjusted, and the temperature of the LED is effectively controlled; by obtaining and calculating the optical power value, the current is finely adjusted on the premise of ensuring that the temperature is within the error range, so as to ensure the stable output of the optical power. Although the stability of current, temperature, the attenuation of LED or LD and the like are all factors influencing the stability of the output of the cold light source, the problem of unstable output is well solved by the method of matching debugging.

Control method and device for stable output of cold light source

Technical Field

The invention relates to the technical field of medical cold light sources, in particular to a dimming method and a brightness control method of a medical cold light source.

Background

In the prior art, many medical devices are illuminated by cold light sources, particularly medical cold light sources, generally adopt one or more high-power LEDs or/and LDs, and according to different use environments, the LEDs or/and LDs with different wave bands can be selected to meet different brightness requirements.

The dimming methods of the currently common LED and LD are two kinds of analog dimming and PWM dimming. The analog dimming is to change the LED current by changing the analog voltage of the driving chip, so as to adjust the light power, but this will affect the chromaticity of the light and cause color cast. The PWM dimming mode controls the turn-off of the LED or LD by changing the duty ratio of the pulse to achieve the adjustment of the light power, but this method may reduce the precision under the condition of large current, and further may not satisfy the function of continuous adjustment.

The stable constant current drive and the good heat dissipation system can enable the LED and the LD to output stably, but the LED and the LD can be attenuated when the LED and the LD are lightened for a long time, and the output light power can be smaller than a preset value. Therefore, the stable output of the LED or and LD takes into consideration the attenuation of the LED or and LD in addition to the stable driving current and the good heat dissipation system.

Disclosure of Invention

In order to solve the problems that the control precision of an LED cold light source is reduced under a large current and the optical power is unstable in the using process, the application provides a method for adjusting the driving current with high precision and ensuring the stability of the optical power, and the specific solution is as follows.

A control method for stable output of cold light source is characterized by comprising the following steps,

step S1: and reading preset values in the memory to obtain an analog voltage value V0, a PWM duty ratio and light power value B0, a temperature upper limit value T0, a current Error range Error _ A0 and a light power Error range Error _ B0 of the control target current value A0.

Step S2: the analog voltage for controlling the driving current is adjusted to be a preset analog voltage value V0, a current value A1 is obtained, a current difference value is calculated, the current difference value is compared with a current error range, real-time feedback control is carried out, and a target current value A0 is achieved, and the process comprises the following steps:

(1) when | A1-A0| > Error _ A0, and A1 > A0, the PWM duty is reduced until A0 is reached;

(2) when | A1-A0| > Error _ A0, and A1 < A0, the PWM duty cycle is increased until A0 is reached.

Step S3: and acquiring a current temperature value T1, and calculating a calculated temperature difference value T = | T0-T1 |. According to temperature difference T, the rotational speed of adjustment fan to guarantee to fall the noise to minimum under the radiating prerequisite fully, its process includes:

(1) when T1< T0 and | T0-T1| > F1 are detected, the rotating speed of the fan is reduced to 5% of the original rotating speed;

(2) when T1< T0 and | T0-T1| < F2 are detected, the rotating speed of the fan is increased to 5 percent of the original rotating speed;

(3) and when T1> T0 is detected, alarming.

Step S4: obtaining a current optical power value B1, calculating an optical power difference, comparing the optical power difference with an optical power error range, and performing real-time feedback control to achieve a target optical power value B0, wherein the process comprises:

(1) when | B1-B0| > Error _ B0, and B1> B0, the PWM duty cycle is decreased to decrease the current until B0 is reached;

(2) when | B1-B0| > Error _ B0, and B1< B0, the PWM duty cycle is increased to increase the current until B0 is reached.

Step S5: and when the temperature value, the current value and the optical power value are within the error range and the optical power value is within the preset value range, assigning the current value to the target current A0, and returning to the step S2.

The invention also provides a device, which comprises a control system (1), a light source driver (2), a light source module (3), a temperature feedback (4), a current feedback (5), a heat dissipation controller (6), a light power feedback (7) and a heat dissipation actuator (8), wherein a main chip of the control system (1) is a microcontroller processor, and data and signals such as current, light power, temperature, alarm processing, light source lighting time recording and the like are all completed by the processor; the light source drive (2) adopts constant current drive, and the analog voltage and the PWM signal provided in the control system (1) are used for controlling the maximum drive current and the output current of each gradient; the light source module (3) is composed of one or more LEDs or LDs with large current; the temperature feedback (4) acquires an analog signal through a temperature sensor, and carries out AD conversion to calculate a current temperature value; the current feedback (5) acquires an analog signal through sampling, carries out AD conversion and calculates the current value; the heat dissipation controller (6) adjusts the rotating speed of the fan according to the feedback temperature data; the optical power feedback (7) is composed of an optical sensor and a memory; the optical sensor is used for acquiring the current optical power value in real time, and the memory is used for storing information such as the serial number of the light source module, correction data, some preset parameters related to current, optical power and service life, and self-defined parameters in a user-defined mode; the heat dissipation actuator (8) consists of a fan and a radiator and is characterized in that,

the light source module (3) and the optical power feedback (7) are structurally integrated, and the memory is arranged in the optical power feedback unit instead of the control module, mainly considering the flexibility of practical use. Even under the same driving current, the light power of different LEDs or LDs is not completely the same and has certain discreteness, so that each LED or LD has respective correction data, a memory storing information corresponding to the light source modules one by one is placed in the light source module, and even if any other module is replaced, the light source can work accurately.

Furthermore, in the control system (1), the main chip may be a microcontroller processor, a DSP or an FPGA.

Further, the temperature sensor in the temperature feedback (4) may be a thermistor or an IC temperature sensor.

Furthermore, the control system (1) controls the analog voltage driving the maximum current to be generated by dividing the voltage through a digital potentiometer or generated by a voltage output analog-to-digital converter.

Furthermore, the heat dissipation controller (6) can be used for controlling the rotating speed of the fan or the power of the semiconductor refrigeration sheet.

Furthermore, the heat dissipation actuator (8) can be a fan forced radiator, a water-cooling radiator or a semiconductor refrigeration sheet.

Drawings

Fig. 1 is a flowchart of a control method for stable output of a cold light source according to an embodiment of the present disclosure.

FIG. 2 is a diagram of an example of a method and apparatus for controlling stable output of a cold light source.

Detailed Description

The present application will now be described in further detail with reference to the accompanying drawings.

The embodiment of the application discloses a method and a device for controlling stable output of a light cold source.

Fig. 2 (1) shows a control system, a main chip is a microcontroller processor, and data and signals such as current, light power, temperature, alarm processing, and recording light source lighting time are all completed by the processor. (2) The light source driving adopts constant current driving, and the analog voltage and PWM signal provided by the control unit are used for controlling the maximum driving current and the output current of each gradient. (3) The light source module consists of a light source module and a light power feedback unit. The light source module is composed of one or more LEDs or LDs with large current and a heat sink. The optical power feedback unit is composed of an optical sensor and a memory. The optical sensor is used for acquiring the current optical power value in real time, and the memory is used for storing information such as the serial number of the light source module, correction data, some preset parameters related to current, optical power and service life, self-defined parameters in a self-defined mode and the like. (4) And the temperature feedback is realized, and the analog signal is obtained through the temperature sensor and is subjected to AD conversion so as to calculate the current temperature value. (5) The current feedback is realized, an analog signal is obtained through sampling, AD conversion is carried out, and the current value is calculated. (6) The cooling controller adjusts the rotating speed of the fan according to the feedback temperature data. (7) The optical power feedback is composed of an optical sensor and a memory. The optical sensor is used for acquiring the current optical power value in real time, and the memory is used for storing information such as the serial number of the light source module, correction data, some preset parameters related to current, optical power and service life, self-defined parameters in a self-defined mode and the like. (8) The heat dissipation actuator consists of a fan and a heat radiator.

The stable output of light source module is under the prerequisite of guaranteeing the operating temperature within range, guarantees that drive current value and light power value are all in error range, and the step of whole control flow and method includes:

h1, determining preset value

The memory is used for storing information such as the serial number of the light source module, correction data, some preset parameters related to current, light power and service life, and self-defined parameters in a self-defined mode. Since the values of the light power of different LEDs or LDs are not exactly the same even at the same driving current and have a certain dispersion, each LED or LD has its own correction data stored in the memory. In the standard mode, 10 steps of current are respectively provided for the LED or the LD, the tested light power value of each step is stored in the memory to be used as correction data, and information such as current parameters, module numbers and the like of each step is stored in the memory. Structurally, the memory is integrated with the light source module, mainly considering the flexibility of practical use. Even under the same driving current, the light power of different LEDs or LDs is not completely the same and has certain discreteness, so that each LED or LD has respective correction data, a memory storing information corresponding to the light source modules one by one is placed in the light source module, and even if any other module is replaced, the light source can work accurately.

H2, determining the stability of working current

The control of the current is completed in a mode of combining an analog voltage signal and a PWM duty ratio, the coarse adjustment is completed through the analog voltage, and the fine adjustment is completed through the PWM duty ratio, so that the adjustment precision and the adjustment range are ensured, and sudden change of the current and the brightness can not be generated. According to the selected operation mode and current gradient, the relevant information of the target current value A0, the target light power value B0, the temperature upper limit value T0, the running Time Time, etc. are read from the memory. Adjusting the analog voltage signal through a control system, adjusting the current to a target current A1, starting current sampling after starting a light source, confirming the current value, obtaining a current difference value A between the current value A1 and a target current value A0 through calculation, comparing the current difference value A with a preset error range, and if the current difference value A is within the error range, indicating that the target current value A1 is reached, and outputting the current normally by a driving module; if the current difference exceeds the error range, further real-time adjustment needs to be performed through current feedback, including:

(1) when | A1-A0| > Error _ A0, and A1 > A0, the PWM duty is reduced until A0 is reached;

(2) when | A1-A0| > Error _ A0, and A1 < A0, the PWM duty cycle is increased until A0 is reached.

H3, real-time temperature detection

And the control system and the temperature feedback are combined to complete real-time temperature detection. The temperature sensor can adopt a thermistor, and when the temperature changes, the corresponding resistance value changes correspondingly. The resistance value of the thermistor is converted into a resistance value by obtaining a voltage value through an AD converter and then converted into a corresponding temperature value according to the resistance value, and the conversion formula is as follows:

Rt=R*EXP（B*（1/T1-1/T2））

where T1 and T2 refer to kelvin temperatures, i.e., T2=273.15+ 25. Rt is the resistance of the thermistor at a temperature of T1; r is the nominal resistance value of the thermistor at the normal temperature of T2; b is an important parameter of the thermistor and has a value of 3380;

and acquiring a current temperature value T1, calculating a temperature difference value T = | T0-T1|, and adjusting the rotating speed of the fan according to the temperature difference value T so as to reduce the noise to the minimum on the premise of ensuring sufficient heat dissipation. The process comprises the following steps:

(1) when T1< T0 is detected and | T0-T1| is >10 ℃, the rotating speed of the fan is reduced to 5% of the original rotating speed;

(2) when T1< T0 is detected and | T0-T1| <5 ℃, the rotating speed of the fan is increased to 5% of the original rotating speed;

(3) and when T1> T0 is detected, alarming.

H4, determining optical power output stabilization

Under the premise of ensuring the current to be stable, the current optical power value B1 is collected in real time to judge whether the light source outputs stably, namely: (I) when B1 is less than B0 and 70%, calculating the operation time of the light source, if the operation time is far less than the theoretical life, indicating that the LED or the LD is abnormally attenuated, and controlling a system to give an alarm;

when B1 ≧ B0 × 70%, in order to ensure stable output, real-time feedback data and processing are required, that is:

(1) when | B1-B0| > Error _ B0, and B1> B0, the PWM duty cycle is decreased to decrease the current until B0 is reached;

(2) when | B1-B0| exceeds Error _ B0, and B1< B0, the PWM duty cycle is increased to increase the current until B0 is reached.

H5, after the stable output of the optical power is determined, the current is assigned to the target current A0, and the operation jumps to H2.