TWI670993B - Light-emitting diode flash control system and method - Google Patents

Abstract

A light-emitting diode flash frequency control system and method includes a control and memory unit, a power circuit electrically connected to the control and memory unit and having an energy storage capacitor, an LED light-emitting unit receiving a driving current output by the power circuit, a The circuit switch is turned on or off by the control and the memory unit control, and a current and voltage detection unit is arranged between the power circuit and the LED light emitting unit to detect the actual current value and actual voltage value of the LED light emitting unit and transmit it to the control Recording with the memory unit; wherein the power circuit is controlled by the control and memory unit to switch to constant voltage or constant current output, pre-charge at the constant voltage output, and then switch to constant current output to light the LED light emitting unit, To achieve high-speed response.

Description

Light-emitting diode flash frequency control system and method

The invention relates to a lighting device applied by an automatic optical inspection system (AOI), and specifically relates to a strobe control system and method for a light emitting diode (LED), which can be used at two types of constant current and constant voltage. Switching between driving modes effectively shortens the response time of the light emitting diode to meet the requirements.

The constant current driving method of light emitting diode (LED) lighting is a mature technology, which can improve the service life of the LED, and reduce the problems of wavelength, color temperature shift and brightness decay. In addition, the LED light emission energy is positively related to the driving current, so using a constant current drive can effectively control the consistency of the light emitting energy, and is not easily affected by temperature changes or the forward voltage of the diode.

However, the disadvantage of constant current drive is that it needs to detect the actual LED drive load to get the correct current feedback, resulting in the current regulation time needs to be extended to hundreds of microseconds (us), or even milliseconds (ms). . Therefore, constant current drive cannot be applied to LED lighting devices that require high-speed response (Instant ON / OFF).

For the automated optical inspection system (AOI), the LED lighting device will use Strobe control to achieve high-speed response to reduce the exposure time of the camera and avoid blurring caused by movement or vibration of the image. The on-the-fly system is combined with other image sensors to increase production speed and reduce inspection man-hour cost. In the LED lighting device used by the automated optical inspection system (AOI), the response time of each LED lighting must be limited to a few microseconds (us) in order to effectively synchronize the exposure with the image sensor. Under the requirement of high-speed response function, the LED lighting device used in the automated optical inspection system (AOI) can still only be driven by constant voltage, but it is not easy to control the uniformity of the luminous energy using constant voltage driving.

In view of the above, the industry urgently needs an LED flash frequency control system and method capable of achieving high-speed response by a constant current drive method, which is suitable for an automated optical inspection system (AOI) to make the luminous flux stable and uniform when the LED is lit, avoiding the use of Variation with temperature changes, while increasing productivity and extending LED life.

The object of the present invention is to provide a light-emitting diode flash frequency control system and method, which can use a constant current driving method to achieve high-speed response.

The invention provides a light-emitting diode flash control system including a control and memory unit, a power circuit electrically connected to the control and memory unit and having an energy storage capacitor, and an LED light-emitting unit receiving a driving current output by the power circuit. And a circuit switch is controlled by the control and memory unit to be turned on or off, and is characterized in that it also has a current and voltage detection unit set between the power circuit and the LED light emitting unit to detect the actual current value of the LED light emitting unit and The actual voltage value is transmitted to the control and memory unit for recording; the power circuit is controlled by the control and memory unit to switch to a constant voltage or constant current output.

The invention also provides a light-emitting diode flicker control method, which can use the aforementioned flicker control system to perform the following steps: obtaining the actual voltage value when an LED light-emitting unit is lit and the drive current reaches a target current value; ensuring the LED The light emitting unit is not lit, a power supply circuit precharges an energy storage capacitor in the power supply circuit with a constant voltage output driving current that matches the actual voltage value; and the power supply circuit switches the constant current output to light up the LED light emitting unit , Then return to the previous step and repeat it, and finally end.

In this way, the power supply circuit will be precharged at a constant voltage and then switched to a constant current output to light up the LED light-emitting unit to shorten the response time of the LED light-emitting unit. At the same time, the constant-current drive method is used to ensure that the LED light-emitting unit The luminous stability of the emitted light.

In order to specifically explain the system functions, execution methods and technical effects of the present invention, a preferred embodiment is provided below and described in detail with reference to the drawings. As shown in FIG. 1, the light emitting diode flicker control system of the preferred embodiment provided by the present invention includes a control and memory unit 20, and a power circuit 30 receives control and memory unit 20 to output a constant voltage or a constant current. An LED light emitting unit 50 receives the driving current from the power circuit 30 and emits light. A current and voltage detecting unit 40 is disposed between the power circuit 30 and the LED light emitting unit 50 to detect the actual current of the LED light emitting unit 50. Value and actual voltage value, and a loop switch 60, which is controlled by the control and memory unit 20 to turn the LED light emitting unit 50 on or off.

The power supply circuit 30 has an energy storage capacitor (not shown) for stabilizing the output driving current. The current and voltage detection unit 40 is electrically connected to the control and memory unit 20 to return the actual current value and actual voltage value of the LED light emitting unit 50. The control and memory unit 20 records the foregoing actual current value and actual voltage value to perform the power circuit 30 Feedback control. In addition, the loop switch 60 is a short-circuit connection device, usually using one of a power transistor, a relay, or a photoelectric switch, which can turn on or cut off the power circuit of the LED light emitting unit 50, so the LED can be lit only when the loop switch 60 is turned on. Light emitting unit 50.

With the foregoing light-emitting diode flicker control system, the light-emitting diode flicker control method shown in FIG. 2 can be performed.

First, step S1 is performed to perform pre-lighting in a constant current driving mode. The control and memory unit 20 will turn on the circuit switch 60 and let the power supply circuit 30 output a driving current to light up the LED light emitting unit 50 so that the current passing through the LED light emitting unit 50 (That is, the actual current value detected by the current-voltage detection unit 40) is consistent with a target current value. At the same time, the actual voltage value of the LED light-emitting unit 50 is detected by the current-voltage detection unit 40 and transmitted back to the control and memory unit 20 for recording, and the loop switch 60 is closed after completion.

Next, step S2 is performed to perform pre-charging in a constant voltage driving manner, and the power supply circuit 30 outputs a driving current in accordance with the actual voltage value recorded in step S1 to ensure that the energy storage capacitor of the power supply circuit 30 is in a state that can be output immediately. At this time, the loop switch 60 is kept off, so the LED light emitting unit 50 is not turned on.

After the pre-charging of the energy storage capacitor is completed, step S3 is triggered to turn on the loop switch 60, thereby lighting the LED light emitting unit 50, and at the same time, the power supply circuit 30 is changed from a constant voltage drive to a constant current drive. Since the energy storage capacitor of the power supply circuit 30 is already in a state that can be output immediately at step S2, it takes only a few microseconds (us) after the loop switch 60 is activated to quickly light up the LED light emitting unit 50 and pass the The actual current value of the LED light emitting unit 50 corresponds to the target current value. When the loop switch 60 is kept on, the power circuit 30 maintains the actual current value of the LED light emitting unit 50 to the target current value through the feedback control of the current and voltage detection unit 40 and the control and memory unit 20, and at the same time the current and voltage detection unit 40 continuously detects the actual voltage value of the LED light emitting unit 50 and transmits it to the control and memory unit 20 for recording.

After the LED light-emitting unit 50 is turned on for a predetermined time, step S4 is then executed, the loop switch 60 is turned off, so that the LED light-emitting unit 50 is turned off, and the power circuit 30 is changed to a constant voltage output according to the actual voltage value stored in the control and memory unit 20, Let the energy storage capacitor of the power supply circuit 30 be in an immediately outputtable state, and then return to step S3 and repeat the execution, until the entire operation is completed, go to step S5 to close the loop switch and stop the output of the power supply circuit 30 to end.

By the aforementioned light-emitting diode flicker control method, the power supply circuit 30 will be regularly switched to a constant voltage or constant-current drive mode under the control of the control and memory unit 20, so that the light-emitting diode flicker control system of the present invention When the LED light emitting unit 50 is turned on, it can meet the requirements of high-speed response.

In addition, since the LED light emitting unit 50 is driven by a constant current when it is lit, it can effectively control the light flux emitted by the LEDs in the LED light emitting unit 50 to be stable and consistent, avoiding variations due to changes in use time and temperature, and can Extend LED life.

20‧‧‧Control and memory unit

30‧‧‧Power circuit

40‧‧‧Current and voltage detection unit

50‧‧‧LED light emitting unit

60‧‧‧loop switch

Steps S1 ~ S5‧‧‧‧

FIG. 1 is a system block diagram of a light-emitting diode flash control system provided by the present invention.

FIG. 2 is a flowchart of a method for controlling a flash frequency of a light emitting diode provided by the present invention.

Claims (7)

A light emitting diode flash frequency control system includes a control and memory unit, a power circuit electrically connected to the control and memory unit and having an energy storage capacitor, an LED light emitting unit receiving a driving current output by the power circuit, and A loop switch is turned on or off under the control of the control and memory unit, and is also characterized by a current and voltage detection unit disposed between the power circuit and the LED light emitting unit to detect an actual LED light emitting unit. The current value and an actual voltage value are transmitted to the control and memory unit for recording. The power circuit is controlled by the control and memory unit to switch to a constant voltage or constant current output. The light-emitting diode flash control system according to claim 1, wherein the loop switch is a short-circuit connection device selected from one of a power transistor, a relay, or a photoelectric switch. The light-emitting diode flash control system according to claim 1, wherein when the loop switch is turned on, the power supply circuit outputs constant current; when the loop switch is turned off, the power supply circuit outputs constant voltage. A light-emitting diode flash frequency control method includes the following steps: obtaining an actual voltage value when an LED light-emitting unit is lit and the driving current reaches a target current value; ensuring that the LED light-emitting unit is not lit, and a power source The circuit pre-charges an energy storage capacitor in the power supply circuit with a constant voltage output driving current that matches the actual voltage value; and the power supply circuit switches to a constant current output, lights up the LED light emitting unit, and then returns to the previous one The steps are repeated and the process ends. The flash frequency control method for a light emitting diode according to claim 4, wherein when the LED light emitting unit is lighted, the current and voltage detecting unit continuously detects the actual voltage value of the LED light emitting unit and transmits it to the control and Memory unit to record. As described in claim 4, the first step is to turn on a loop switch, and at the same time let the power circuit output the driving current to the LED light-emitting unit for pre-lighting, and then the current voltage The detection unit detects and obtains the actual voltage value and sends it back to the control and memory unit for recording, and then closes the loop switch. The flashing control method for a light-emitting diode according to claim 4, wherein the LED light-emitting unit controls whether the LED light-emitting unit can be lighted by turning on or off a loop switch.