Integrated control circuit for LED strobe and flash

Abstract

The present invention relates to the field of LED strobe and flash control. Disclosed is an integrated control circuit for LED strobe and flash. In the circuit, an MCU module plays a core role: in a strobe mode, the MCU module sequentially acquires strobe pulse signals transmitted by a camera on the basis of a set frequency, and generates corresponding strobe PWM control signals on the basis of the duty cycles of the strobe pulse signals; and in a flash mode, the MCU module generates corresponding flash PWM control signals on the basis of flash pulse signals with a set pulse width that are transmitted by the camera. Subsequently, an LED signal control module receives these PWM control signals and converts same into switch control signals, so as to accurately control the turned-on / turned-off states and brightness of LED lights in an LED light source module. Such a design not only simplifies the structure of the circuit, but also improves the flexibility and response speed of the control circuit, thereby achieving an efficient and stable light source control effect.

Description

An integrated control circuit for LED strobe and flashing Technical Field

[0001] This invention relates to the field of LED strobe and strobe control, and more particularly to an integrated control circuit for LED strobe and strobe. Background Technology

[0002] In the fields of security and traffic monitoring, supplementary lighting devices provide necessary illumination for cameras in low-light environments to ensure the clarity of video recording and captured images. Currently, LED supplementary lighting devices on the market mainly perform two functions: strobe and stro. The strobe function is used to synchronize with each frame of the camera shutter, ensuring continuous supplementary lighting during video recording; the stro is used to provide high-brightness instantaneous supplementary lighting when capturing images to capture detailed features of objects. The brightness adjustment of these two functions is crucial for ensuring the quality of recording and capturing images, but excessive brightness may pose safety hazards to pedestrians and drivers, and does not meet energy conservation and environmental protection requirements. However, most supplementary lights on the market today either have non-adjustable brightness or only limited strobe brightness adjustment, making it difficult to meet the needs of high-quality image capture.

[0003] Existing lighting solutions primarily focus on power supply design and control methods, with two prominent approaches: a flyback power supply with a secondary DC-DC converter providing constant current, and a flyback power supply with a secondary DC-DC converter providing boost and constant voltage. While these solutions effectively provide the required strobe and flicker functions, they all require a secondary DC-DC converter circuit to control strobe and flicker separately, resulting in complex circuit design, a large number of components, large circuit board size, and high cost. In contrast, this patent proposes an innovative circuit that allows strobe and flicker to share a single power supply and a single signal control circuit, eliminating the need for a secondary DC-DC converter circuit. This simplifies the control logic, reduces the number of required components, minimizes space requirements, and significantly lowers costs. This improvement not only enhances the flexibility and adaptability of the control circuit but also provides users with a more economical and efficient solution. Technical issues

[0004] To enable strobe and flashing to share a single power supply and signal control circuit, thereby simplifying the control logic and reducing the number of required components, this invention proposes an integrated control circuit for LED strobe and flashing. Technical solutions

[0005] An integrated control circuit for LED strobe and flashing includes:

[0006] LED light source module;

[0007] The AC-DC conversion module is used to connect to AC power and convert it into DC power voltage before inputting it into the LED light source module.

[0008] The MCU module is used to sequentially acquire strobe pulse signals continuously emitted by the camera at a set frequency in strobe mode, and generate a corresponding strobe PWM control signal based on the duty cycle of the strobe pulse signal; one strobe pulse signal corresponds to one control cycle, and one control cycle includes a lighting period and an off period; it is also used to acquire strobe pulse signals with a set pulse width emitted by the camera in strobe mode, and generate a corresponding strobe PWM control signal by processing the strobe pulse signal;

[0009] The LED signal control module, which is connected to the MCU module, is used to convert the PWM control signal into a corresponding switching control signal, and to control the on / off state and brightness of the LEDs in the LED light source module through the switching control signal; the PWM control signal is a strobe PWM control signal or a flash PWM control signal.

[0010] Furthermore, the LED signal control module includes:

[0011] The second MOSFET Q2 is connected to the signal conversion unit; the input terminal of the signal conversion unit is connected to the output of the MCU module, and the output terminal is connected to the gate of the second MOSFET Q2; the drain of the second MOSFET Q2 is connected to the negative terminal pin of the LED in the LED light source module.

[0012] The signal conversion unit is used to receive the PWM control signal output by the MCU module, convert it into a corresponding switching control signal, and drive the second MOSFET Q2 through the switching control signal. At the same time, it controls the conduction pulse width and frequency of the second MOSFET Q2, thereby controlling the on / off state and brightness of the LED.

[0013] Furthermore, the MCU module is also used to set or adjust the duty cycle and flashing frequency of the strobe PWM control signal and the strobe PWM control signal, wherein the brightness of the LED light is controlled by adjusting the duty cycle of the strobe PWM control signal and the strobe PWM control signal.

[0014] Furthermore, the step of generating a corresponding strobe PWM control signal by processing the strobe pulse signal specifically involves: extracting the width information of the strobe pulse signal and generating a corresponding strobe PWM control signal based on the width information.

[0015] Furthermore, the AC-DC conversion module is specifically used to convert the incoming AC power into DC power supply voltage and auxiliary power supply voltage; wherein, the DC power supply voltage is the power supply for the LED light source module, and the auxiliary power supply voltage is the power supply for the LED signal control module and the MCU module.

[0016] Furthermore, the LED light source module includes a current sensing resistor; the current sensing resistor is used to convert the actual operating current flowing through the LED lamp into a voltage signal;

[0017] The MCU module is also used to read the voltage signal converted by the current detection resistor in real time, calculate the actual operating current of the LED lamp based on the voltage signal, and generate a corresponding voltage adjustment signal based on the difference between the actual operating current and the preset target current.

[0018] The AC-DC conversion module is also used to adjust the DC power supply voltage it outputs to the LED light source module according to the voltage adjustment signal, so that the peak current of the LED lamp is stabilized within a preset range.

[0019] Furthermore, the signal conversion unit includes:

[0020] The fourth chip U4; the enable pin EN of the fourth chip U4 is connected to one end of the eleventh resistor R11, the ground pin GND is grounded, the input pin IN+ is connected to one end of the thirteenth resistor R13 and then connected to the PWM control signal output by the MCU module, the output pin OUT is connected to one end of the twelfth resistor R12, the power supply pin VDD is connected to one end of the eighth capacitor C8 and the other end of the eleventh resistor R11 and then connected to the auxiliary power supply voltage output by the AC-DC conversion module; the other end of the eighth capacitor C8 is grounded; the other end of the twelfth resistor R12 is connected to one end of the fourteenth resistor R14 and then connected to the gate of the second MOSFET Q2; the other end of the thirteenth resistor R13 is connected to the other end of the fourteenth resistor R14 and then grounded.

[0021] Furthermore, in the LED light source module:

[0022] The positive pin of the LED is connected to the DC power supply voltage output by the AC-DC conversion module, and the negative pin is connected to the drain of the second MOSFET Q2; one end of the current sensing resistor R15 is connected to the source of the second MOSFET Q2, and the other end is grounded with the other end of the fourteenth resistor R14.

[0023] Furthermore, the control chip in the MCU module is an STM32.

[0024] Furthermore, the fourth chip U4 is model SGM48539. Beneficial effects

[0025] Compared with the prior art, the present invention has at least the following beneficial effects:

[0026] (1) The control circuit provided by the present invention can achieve efficient management of LED strobe and strobe modes through a single power supply and a single signal control circuit. In this circuit, the MCU module plays a core role: in strobe mode, it sequentially acquires the strobe pulse signals emitted by the camera based on a set frequency, and generates corresponding strobe PWM control signals according to the duty cycle of these signals; in strobe mode, it generates corresponding strobe PWM control signals according to the strobe pulse signals with a set pulse width emitted by the camera. Subsequently, the LED signal control module receives these PWM control signals and converts them into switching control signals, thereby accurately controlling the on / off state and brightness of the LED lamps in the LED light source module. This design not only simplifies the circuit structure, but also improves the flexibility and response speed of the control circuit, achieving efficient and stable light source control effect, so that a single circuit can meet the strobe and strobe requirements in different application scenarios.

[0027] (2) In this invention, the MCU module can not only generate corresponding PWM control signals based on strobe or strobe pulse signals, but also set or adjust the duty cycle and flashing frequency of these control signals, thereby finely adjusting the brightness of the LED light. Especially in strobe mode, by extracting the width information of the strobe pulse signal to generate the corresponding strobe PWM control signal, the flexibility and accuracy of the control are further enhanced;

[0028] (3) In this invention, the LED light source module includes a current sensing resistor, which converts the actual operating current flowing through the LED lamp into a voltage signal for the MCU module to read. The MCU module calculates the actual operating current based on this voltage signal and generates a voltage adjustment signal accordingly. The AC-DC conversion module adjusts the DC power supply voltage it outputs to the LED light source module based on the voltage adjustment signal to ensure that the peak current of the LED lamp is stable within a preset range, thereby improving the stability and reliability of the circuit.

[0029] (4) In this invention, the AC-DC conversion module can not only convert the incoming AC power into DC power supply voltage for the LED light source module, but also provide auxiliary power supply voltage for the LED signal control module and MCU module, thus realizing efficient energy conversion and utilization;

[0030] (5) The present invention, through the design of a specific chip (such as the fourth chip U4 of model SGM48539) and a MOS transistor (Q2), enables the PWM control signal to be effectively converted into a switching control signal, thereby controlling the on / off state and brightness of the LED, and improving the working efficiency and response speed of the entire circuit. Attached Figure Description

[0031] Figure 1 is a circuit diagram of an integrated control circuit for LED strobe and flash according to an embodiment of the present invention;

[0032] Figure 2 is a circuit diagram of the AC-DC conversion module according to an embodiment of the present invention;

[0033] Figure 3 is a circuit diagram of the LED signal control module and the LED light source module according to an embodiment of the present invention;

[0034] Figure 4 is a strobe signal diagram with the horizontal axis representing 2ms in an embodiment of the present invention;

[0035] Figure 5 is a strobe signal diagram with the horizontal axis being 2µs in one grid in an embodiment of the present invention;

[0036] Figure 6 is a strobe signal diagram with the horizontal axis representing 2ms in an embodiment of the present invention;

[0037] Figure 7 is a strobe signal diagram with the horizontal axis being 2µs in an embodiment of the present invention. Embodiments of the present invention

[0038] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0039] To enable both strobe and flashing to share a single power supply and signal control circuit, thereby simplifying the control logic and reducing the number of required components, as shown in Figure 1, this invention proposes an integrated control circuit for LED strobe and flashing, comprising:

[0040] LED light source module;

[0041] The LED light source module includes a current detection resistor; the current detection resistor is used to convert the actual operating current flowing through the LED lamp into a voltage signal Vis.

[0042] The AC-DC conversion module is used to connect to AC220V power and convert it into DC power voltage before inputting it into the LED light source module.

[0043] The MCU module is used to sequentially acquire the strobe pulse signals continuously emitted by the camera based on a set frequency in strobe mode, and generate a corresponding strobe PWM control signal based on the duty cycle of the strobe pulse signal; one strobe pulse signal corresponds to one control cycle, and one control cycle includes a lighting period and an off period.

[0044] The MCU module is also used to acquire a strobe pulse signal with a set pulse width emitted by the camera in strobe mode, and generate a corresponding strobe PWM control signal by processing the strobe pulse signal.

[0045] The step of generating a corresponding strobe PWM control signal by processing the strobe pulse signal specifically involves: extracting the width information of the strobe pulse signal and generating a corresponding strobe PWM control signal based on the width information.

[0046] In this invention, the MCU module can not only generate corresponding PWM control signals based on strobe or flash pulse signals, but also set or adjust the duty cycle and flashing frequency of these control signals, thereby finely adjusting the brightness of the LED light. Especially in flash mode, by extracting the width information of the flash pulse signal to generate the corresponding flash PWM control signal, the flexibility and accuracy of control are further enhanced.

[0047] The MCU module is also used to set or adjust the duty cycle and flashing frequency of the strobe PWM control signal and the burst PWM control signal, wherein the brightness of the LED light is controlled by adjusting the duty cycle of the strobe PWM control signal and the burst PWM control signal.

[0048] The MCU module is also used to read the voltage signal converted by the current detection resistor in real time, calculate the actual operating current of the LED lamp based on the voltage signal, and generate a corresponding voltage adjustment signal VF based on the difference between the actual operating current and the preset target current.

[0049] The AC-DC conversion module is also used to adjust the DC power supply voltage it outputs to the LED light source module according to the voltage adjustment signal, so that the peak current of the LED lamp is stabilized within a preset range.

[0050] In this invention, the LED light source module includes a current sensing resistor that converts the actual operating current flowing through the LED into a voltage signal Vis for the MCU module to read. The MCU module calculates the actual operating current based on this voltage signal and generates a voltage adjustment signal VF accordingly. The AC-DC conversion module adjusts the DC power supply voltage it outputs to the LED light source module based on the voltage adjustment signal VF, ensuring that the peak current of the LED remains stable within a preset range, thus improving the stability and reliability of the circuit. Specifically, this precise feedback control mechanism enables the AC-DC conversion module to adjust the DC power supply voltage it outputs to the LED light source module in real time according to the voltage adjustment signal VF. This process ensures that even under load changes or environmental fluctuations, the peak current of the LED remains within a preset range, thereby extending the lifespan of the LED and improving the stability and reliability of the control circuit. Furthermore, in this way, the entire control circuit not only provides efficient energy conversion but also achieves precise control of the LED current. This design significantly improves the overall performance of the control circuit and reduces potential problems caused by current instability.

[0051] In this embodiment, the control chip in the MCU module is an STM32, but it is not limited to this model. Specifically, the STM32 series microcontrollers are known for their high performance, low power consumption, and abundant peripheral resources, making them ideal for complex real-time control systems, such as the integrated LED strobe and strobe control circuit in this invention. The STM32 microcontroller features multiple timers, PWM output channels, and a high-speed ADC (analog-to-digital converter), enabling efficient processing of strobe or strobe pulse signals from the camera and generating corresponding high-frequency PWM control signals. Furthermore, the STM32 supports various communication interfaces (such as I²C, SPI, UART, etc.), facilitating data interaction with other peripheral devices and further enhancing the system's scalability and flexibility.

[0052] The LED signal control module, which is connected to the MCU module, is used to convert the PWM control signal LED-PB-CTRL into a corresponding switch control signal LED-PB, and control the on / off state and brightness of the LEDs in the LED light source module through the switch control signal LED-PB; the PWM control signal LED-PB-CTRL is a strobe PWM control signal or a flash PWM control signal.

[0053] As shown in Figure 3, the LED signal control module includes:

[0054] The second MOSFET Q2 is connected to the signal conversion unit; the input terminal of the signal conversion unit is connected to the output of the MCU module, and the output terminal is connected to the gate of the second MOSFET Q2; the drain of the second MOSFET Q2 is connected to the negative terminal pin of the LED in the LED light source module.

[0055] The signal conversion unit is used to receive the PWM control signal output by the MCU module, convert it into a corresponding switching control signal, and drive the second MOSFET Q2 through the switching control signal. At the same time, it controls the conduction pulse width and frequency of the second MOSFET Q2, thereby controlling the on / off state and brightness of the LED.

[0056] The signal conversion unit includes:

[0057] The fourth chip U4; the enable pin EN of the fourth chip U4 is connected to one end of the eleventh resistor R11, the ground pin GND is grounded, the input pin IN+ is connected to one end of the thirteenth resistor R13 and then connected to the PWM control signal output by the MCU module, the output pin OUT is connected to one end of the twelfth resistor R12, the power supply pin VDD is connected to one end of the eighth capacitor C8 and the other end of the eleventh resistor R11 and then connected to the auxiliary power supply voltage output by the AC-DC conversion module; the other end of the eighth capacitor C8 is grounded; the other end of the twelfth resistor R12 is connected to one end of the fourteenth resistor R14 and then connected to the gate of the second MOSFET Q2; the other end of the thirteenth resistor R13 is connected to the other end of the fourteenth resistor R14 and then grounded.

[0058] In this embodiment, the PWM control signal generated by the MCU module is sent to the LED signal control module, which includes a specific chip (the fourth chip U4 of model SGM48539) and a MOSFET (the second MOSFET Q2). The function of the LED signal control module is to convert the high-frequency PWM control signal output by the MCU module into a switching control signal that can directly drive the MOSFET. Since the signal amplitude output by the MCU module is low and insufficient to directly drive the MOSFET, an additional driver chip is needed to enhance the signal strength and convert it into a switching control signal that can actually be used to control the LED's on / off state.

[0059] This invention, through the design of a specific chip (the fourth chip U4 of SGM48539) and a MOSFET (Q2), enables the PWM control signal to be effectively converted into a switching control signal, thereby controlling the on / off state and brightness of the LED, improving the overall circuit efficiency and response speed.

[0060] It should be noted that the fourth chip U4 is model SGM48539, but it is not limited to this model. Specifically, the SGM48539 is a high-performance analog switch chip with low on-resistance and high bandwidth, suitable for applications requiring fast response and precise control. In the LED strobe and strobe integrated control circuit of this invention, the main function of the SGM48539 is to convert the PWM control signal output by the MCU module into corresponding switching control signals, and drive the MOSFET (second MOSFET Q2) through these signals, thereby achieving precise control over the on / off state and brightness of the LED. Although the SGM48539 is selected as a key component in this embodiment, this choice is not unique. Other signal driver chips can also be used depending on the actual application requirements and specific system design requirements.

[0061] In the LED light source module:

[0062] The positive pin of the LED is connected to the DC power supply voltage output by the AC-DC conversion module, and the negative pin is connected to the drain of the second MOSFET Q2; one end of the current sensing resistor R15 is connected to the source of the second MOSFET Q2, and the other end is grounded with the other end of the fourteenth resistor R14.

[0063] The AC-DC conversion module is specifically used to convert the incoming AC power into DC power supply voltage and auxiliary power supply voltage; wherein, the DC power supply voltage is the power supply for the LED light source module, and the auxiliary power supply voltage is the power supply for the LED signal control module and the MCU module.

[0064] In this invention, the AC-DC conversion module not only converts the incoming AC power into DC power supply voltage for the LED light source module, but also provides auxiliary power supply voltage for the LED signal control module and MCU module, thus achieving efficient energy conversion and utilization.

[0065] As shown in Figure 2, one end of the sixth resistor R6 is connected to the voltage adjustment signal VF (a PWM signal) generated by the MCU module. This signal is converted into a relatively smooth DC voltage signal Vc4 by a low-pass filter composed of resistor R6 and capacitor C4. This DC voltage signal is used to adjust the operating state of the adjustable reference voltage source TL431 (U3). Since TL431 has a fixed 2.5V reference voltage, when the voltage connected to the reference input terminal of TL431 through R5 changes, the current flowing through R5 will change. This change further affects the current through the feedback resistor network (including R2 and R7), thereby changing the current intensity on the LED side of the optocoupler (U2). The other side of the optocoupler adjusts its output current according to the received light intensity (the light intensity refers to the amount of light emitted by the LED inside the optocoupler, which directly affects the signal intensity received by the phototransistor on the other side of the optocoupler). This output current is fed back to the feedback pin F of the PWM controller (U1). The PWM controller adjusts the on-time of the MOSFET switch (Q1) based on this feedback signal, thereby changing the voltage level output from the secondary side of transformer T1, ultimately achieving precise control of the DC power supply voltage output. In this way, the MCU module reads the voltage signal converted by the current sensing resistor in real time and adjusts the voltage adjustment signal VF (i.e., changes the duty cycle of the voltage adjustment signal VF) based on this voltage signal in real time, forming a closed-loop control that dynamically adjusts the voltage supplied to the LED light source module, ensuring its stability and adapting to different brightness requirements.

[0066] Regarding the fact that a change in the voltage connected to the TL431 reference input via R5 will cause a change in the current flowing through R5, further explanation is needed as follows:

[0067] 1. Apply to the reference input of TL431:

[0068] The DC voltage signal Vc4 is connected to the reference input (REF pin) of the TL431 through resistor R5. Ideally, in order to maintain the internal reference voltage (2.5V) of the TL431, the TL431 will adjust its cathode voltage (i.e., control the current flowing through itself) so that the voltage difference from the REF pin to the cathode remains constant.

[0069] 2. Relationship between voltage and current:

[0070] When Vc4 changes, it means that the voltage applied to the REF pin of the TL431 has changed. Since the goal of the TL431 is to maintain a voltage of 2.5V between its REF pin and the cathode, when the externally applied voltage (i.e., Vc4) changes, the TL431 must adjust its cathode voltage (change the current flowing through it) to compensate for this change.

[0071] If Vc4 increases, in order to maintain the 2.5V reference voltage, the TL431 will reduce the current flowing through it, thereby lowering the cathode voltage; conversely, if Vc4 decreases, the TL431 will increase the current flowing through it, thereby increasing the cathode voltage.

[0072] 3. Impact on R5:

[0073] Because the TL431 adjusts its cathode voltage (i.e., changes the current flowing through R5), this in turn affects the voltage drop across R5. In other words, the change in Vc4 causes the TL431 to adjust its behavior, thereby changing the current flowing through R5.

[0074] Additionally, it's worth explaining that the secondary DC-DC converter circuit can convert the DC voltage after primary rectification and regulation into the specific voltage required by the system or load. This allows for a stable output voltage even with input voltage fluctuations. Furthermore, when the circuit requires multiple different supply voltages, multiple outputs can be easily achieved through the secondary DC-DC converter. This invention eliminates the need for a secondary DC-DC converter circuit through two improvements:

[0075] One aspect is:

[0076] 1. Direct rectification and filtering: In this embodiment, a high-efficiency rectifier D1 and a filter capacitor C6 are used to directly convert the AC voltage on the secondary side of the transformer into a relatively stable DC voltage, avoiding additional voltage transformation steps.

[0077] 2. Precision feedback control: The feedback network composed of optocoupler U2 and TL431 is used to monitor and adjust the output DC power supply voltage in real time to ensure output stability without the need for an additional DC-DC conversion stage.

[0078] 3. Single-stage PWM control: The switching frequency and duty cycle of MOSFET Q1 are precisely controlled by the PWM controller U1 (such as OB2362) to effectively regulate the DC power supply voltage and meet the needs of different loads.

[0079] 4. Simplified circuit structure: The above methods simplify circuit design, reduce the number of required components, lower costs, and reduce circuit board size, while improving the overall system reliability and efficiency.

[0080] II. Another aspect is:

[0081] The core of this invention lies in processing the input low-frequency control signal (strobe pulse signal or strobe pulse signal) through the MCU module to generate a high-frequency PWM control signal, thereby realizing efficient and simple LED strobe and strobe control, eliminating the need for the traditional secondary DC-DC conversion circuit.

[0082] Specifically:

[0083] 1. In strobe mode, the MCU module receives strobe pulse signals from the camera. Based on these low-frequency control signals, the MCU module generates corresponding high-frequency strobe PWM control signals. For example, in strobe mode, with a set frequency (overall frequency) of 100Hz and a duty cycle (overall duty cycle) of 30%, it means that the camera needs the LED to light up 100 times per second, each lasting 3ms, with each flash pulse signal corresponding to one strobe pulse signal. When the MCU receives the strobe pulse signal, it generates a high-frequency (local frequency) strobe PWM control signal greater than 100kHz. In other words, during the aforementioned 3ms lighting period, the LED is not continuously lit, but rather rapidly switches on and off at a frequency greater than 100kHz and with a local duty cycle (i.e., the duty cycle of the strobe PWM control signal set by the MCU module). Here, the local duty cycle refers to the proportion of time the LED is at a high level (on) within these 3ms.

[0084] By adjusting the duty cycle (partial duty cycle) of this strobe PWM control signal, the actual brightness of the LED can be further fine-tuned. Even if the total illumination time is fixed at 3ms, by changing the specific duration of the LED illumination during this period (i.e., the partial duty cycle), the brightness output of the LED can be adjusted more precisely without changing the overall brightness perception. This adapts to different shooting needs or environmental conditions, overcoming the problem of the limited brightness adjustment range in existing technologies, which prevents good compatibility with cameras.

[0085] In other words, in strobe mode, these two duty cycles work together to ensure that the LED light can provide a stable supplementary lighting effect. The overall duty cycle determines the on / off rhythm of the LED light within one second, while the local duty cycle is used to precisely control the brightness of the LED light each time it is turned on. This invention achieves fine-tuning of LED light brightness through two levels of frequency (overall frequency and local frequency) and duty cycle (overall duty cycle and local duty cycle).

[0086] 2. In strobe mode, the MCU module receives a strobe pulse signal with a set pulse width from the camera. For example, a strobe pulse signal with a pulse width of 3ms. The MCU module also processes this low-frequency control signal and generates a corresponding high-frequency strobe PWM control signal. During this process, the MCU module generates a high-frequency strobe PWM control signal greater than 100kHz within the effective time of the strobe pulse signal, and controls the brightness of the LED light by adjusting the duty cycle of this high-frequency PWM signal.

[0087] In this regard, it is necessary to explain:

[0088] There are also two duty cycles in strobe mode:

[0089] 2.1 Overall duty cycle (pulse width):

[0090] In strobe mode, the camera emits a pulse signal with a fixed pulse width, such as 3ms. This means that the LED needs to provide high-brightness illumination during this 3ms period.

[0091] This 3ms can be considered as the "on period" within the entire cycle, while the rest of the time is the "off period." If we only consider this aspect, then for a strobe event, there is a clear overall duty cycle (for example, within a very short time window, 3ms is the on period, and the rest of the time is the off period). However, when discussing strobes, we usually focus more on the behavior within this specific time period, rather than the obvious periodicity of flickering.

[0092] 2.2 Local Duty Cycle (i.e., the duty cycle of the strobe PWM control signal):

[0093] During this 3ms on-time period, the LED is not continuously lit, but rather switches on and off rapidly at a frequency greater than 100kHz. The duty cycle here refers to the proportion of time the LED is at a high level (on) within these 3ms.

[0094] By adjusting this local duty cycle, the actual brightness output of the LED can be further fine-tuned while keeping the total on-time constant. Even if the total on-time is fixed at 3ms, by changing the specific duration of the LED's illumination during this period (i.e., the local duty cycle), the brightness output of the LED can be adjusted more precisely without changing the overall perceived brightness.

[0095] 2.3 Significance in practical applications:

[0096] Control in strobe mode: In strobe mode, while the primary goal is to provide the highest possible brightness within the 3ms timeframe, this doesn't mean the local duty cycle is always 100%. Depending on specific needs, the MCU module can adjust the local duty cycle to achieve different levels of brightness control. For example, in some cases, maximum brightness may not be required; instead, a medium or lower level of brightness may be needed, which can be achieved by adjusting the local duty cycle.

[0097] In other words, although the core of strobe mode lies in providing high-intensity illumination within a short time period (such as 3ms), there are still two levels of duty cycle control in actual implementation:

[0098] Overall duty cycle: determines the total time window for the strobe event to occur (e.g., 3ms).

[0099] Local duty cycle: Used to precisely control the brightness of LED lights during a specified on-time period.

[0100] The combined effect of these two duty cycles ensures that the circuit can flexibly adapt to different application scenarios. Even in strobe mode, the ideal brightness effect can be achieved by adjusting the high-frequency PWM duty cycle.

[0101] In summary, this invention processes the input low-frequency control signal (strobe pulse signal or strobe pulse signal) through an MCU module and generates a high-frequency PWM control signal (strobe PWM control signal or strobe PWM control signal). This eliminates the need for a traditional secondary DC-DC converter circuit because this design directly achieves precise voltage and brightness adjustment on the primary side. The main function of the secondary DC-DC converter circuit is to further convert the rectified and regulated DC voltage from the primary side into the specific voltage required by the system or load, and to provide electrical isolation and multiple outputs. However, in this invention, the MCU module generates a high-frequency PWM control signal through precise analysis and conversion of the input low-frequency signal, which is directly used to control the switching state and brightness of the LED light, thus achieving efficient dimming without additional voltage conversion steps. This method not only simplifies the circuit structure and reduces the number of components, but also improves the circuit's response speed and efficiency. While secondary DC-DC converter circuits can integrate PWM control logic to generate high-frequency PWM signals, this increases circuit complexity and cost. This invention, however, directly generates high-frequency PWM control signals through an MCU module, combined with precise feedback control (such as using optocouplers U2 and TL431), ensuring stable output voltage and meeting the demands of different loads. Therefore, efficient and stable power supply and dimming control can be achieved without a secondary DC-DC converter circuit. This strategy effectively reduces circuit complexity and cost while improving overall performance.

[0102] Therefore, although the secondary DC-DC conversion circuit is important in traditional power supply design, this invention successfully eliminates this step by optimizing the circuit design and adopting advanced control strategies, thus achieving a simpler and more efficient power supply solution.

[0103] Additionally, it should be noted that:

[0104] The strobe signals of the LED light (including: strobe pulse signal, strobe PWM control signal, the switching control signal corresponding to the strobe PWM control signal, and strobe current) are shown in Figures 4 and 5:

[0105] In Figures 4 and 5, 1, 2, 3, and 4 represent the strobe pulse signal, the strobe PWM control signal, the corresponding switch control signal of the strobe PWM control signal, and the channel corresponding to the strobe lightning current, respectively. In the figures, 1=5V, 2=5V, and 3=5V on the vertical axis indicate that the vertical axis of the corresponding channel is one 5V increment; 4=5A indicates that the vertical axis of the corresponding channel is one 5A increment. The horizontal axis of Figure 4 is one 2ms increment, and the horizontal axis of Figure 5 is one 2µs increment; that is, Figure 5 is the expanded waveform diagram of Figure 4.

[0106] The strobe signals of an LED light (including: strobe pulse signal, strobe PWM control signal, the switching control signal corresponding to the strobe PWM control signal, and strobe lightning current) are shown in Figures 6 and 7:

[0107] In Figures 6 and 7, 1, 2, 3, and 4 represent the strobe pulse signal, the strobe PWM control signal, the corresponding switch control signal of the strobe PWM control signal, and the channel corresponding to the strobe lightning current, respectively. In the figures, 1=5V, 2=5V, and 3=5V on the vertical axis indicate that the vertical axis of the corresponding channel is one 5V increment; 4=5A indicates that the vertical axis of the corresponding channel is one 5A increment. The horizontal axis of Figure 6 is one 2ms increment, and the horizontal axis of Figure 7 is one 2µs increment; that is, Figure 7 is the expanded waveform diagram of Figure 6.

[0108] In other words:

[0109] Figure 4 shows a longer time scale (2ms / division) of the stroboscopic signal to observe the overall trend.

[0110] Figure 5 shows a shorter time scale (2 μs / division) of the stroboscopic signal, allowing for detailed observation of each pulse.

[0111] Figure 6 shows a longer timescale (2 ms / division) of the strobe signal to observe the overall trend.

[0112] Figure 7 shows a shorter timescale (2 μs / division) of the strobe signal, allowing for detailed observation of each pulse.

[0113] In the diagram, T represents the trigger point, which is the moment when the oscilloscope begins acquiring data.

[0114] Additionally, it should be noted that:

[0115] 1. Dimming mechanism in LED strobe mode:

[0116] In strobe mode, brightness adjustment is achieved by adjusting the duty cycle of the PWM control signal. Specifically, during each illumination period, the LED current can be equivalently calculated as the peak current multiplied by the duty cycle of the high-frequency PWM waveform at that time. For example, when the duty cycle is 50%, the average current of the LED during this period will be half of the peak current. Therefore, by changing the duty cycle of the PWM control signal, the brightness of the LED can be flexibly adjusted while keeping the total illumination time constant. This mechanism enables fine-grained brightness adjustment even in strobe mode, thereby meeting the shooting needs or environmental conditions in different scenarios.

[0117] 2. Dimming mechanism in LED strobe mode:

[0118] Similarly, in strobe mode, brightness is controlled by adjusting the duty cycle of the PWM control signal. While the primary purpose of strobe mode is to provide high-brightness illumination for a short period, different brightness levels may be required in practical applications. By adjusting the duty cycle of the strobe PWM control signal, the actual brightness of the LED can be precisely controlled within the 3ms illumination period. For example, adjusting the duty cycle from 100% to 80% reduces the average current of the LED during this time, thus lowering its brightness. This not only provides high-intensity illumination when needed but also allows for flexible brightness adjustment based on specific requirements, ensuring optimal shooting results. This method achieves efficient and precise brightness adjustment, suitable for various complex lighting requirements.

[0119] The control circuit provided by this invention can efficiently manage LED strobe and strobe modes using a single power supply and a single signal control circuit. In this circuit, the MCU module plays a core role: in strobe mode, it sequentially acquires strobe pulse signals emitted by the camera based on a set frequency and generates corresponding strobe PWM control signals according to the duty cycle of these signals; in strobe mode, it generates corresponding strobe PWM control signals based on strobe pulse signals with a set pulse width emitted by the camera. Subsequently, the LED signal control module receives these PWM control signals and converts them into switching control signals, thereby precisely controlling the on / off state and brightness of the LEDs in the LED light source module. This design not only simplifies the circuit structure but also improves the flexibility and response speed of the control circuit, achieving efficient and stable light source control, allowing a single circuit to meet the strobe and strobe requirements of different application scenarios.

Claims

1. An integrated control circuit for LED strobe and flashing, characterized in that, include: LED light source module; The AC-DC conversion module is used to connect to AC power and convert it into DC power voltage before inputting it into the LED light source module. The MCU module is used to sequentially acquire strobe pulse signals continuously emitted by the camera at a set frequency in strobe mode, and generate a corresponding strobe PWM control signal based on the duty cycle of the strobe pulse signal; one strobe pulse signal corresponds to one control cycle, and one control cycle includes a lighting period and an off period; it is also used to acquire strobe pulse signals with a set pulse width emitted by the camera in strobe mode, and generate a corresponding strobe PWM control signal by processing the strobe pulse signal; The LED signal control module, which is connected to the MCU module, is used to convert the PWM control signal into a corresponding switching control signal, and to control the on / off state and brightness of the LEDs in the LED light source module through the switching control signal; the PWM control signal is a strobe PWM control signal or a flash PWM control signal. The LED light source module includes a current sensing resistor; the current sensing resistor is used to convert the actual operating current flowing through the LED lamp into a voltage signal. The MCU module is also used to read the voltage signal converted by the current detection resistor in real time, calculate the actual operating current of the LED lamp based on the voltage signal, and generate a corresponding voltage adjustment signal based on the difference between the actual operating current and the preset target current. The AC-DC conversion module is also used to adjust the DC power supply voltage it outputs to the LED light source module according to the voltage adjustment signal, so that the peak current of the LED lamp is stabilized within a preset range. The AC-DC conversion module includes: The low-pass filter is connected to a PWM voltage adjustment signal VF generated by the MCU module at one end, and outputs a relatively smooth DC voltage signal Vc4 at the other end. The reference voltage source TL431 has its reference input terminal connected to the DC voltage signal Vc4 output by the low-pass filter through resistor R5. It has a fixed 2.5V reference voltage inside and adjusts the cathode voltage and the current flowing through itself according to the externally applied voltage changes. A feedback resistor network is used to transmit the output current variation of the reference voltage source TL431 to the optocoupler U2; The current intensity on the light-emitting diode side of the optocoupler U2 is affected by the feedback resistor network, and its output current is adjusted according to the received light intensity. The PWM controller U1 receives the output current of the optocoupler U2 as a feedback signal through its feedback pin F, and adjusts the conduction time of the MOSFET switch Q1 accordingly, thereby changing the voltage level output on the secondary side of the transformer T1 and realizing precise control of the DC power supply voltage output. The MOSFET switch Q1 is controlled by the PWM controller U1 to turn on and off, thereby adjusting the output voltage on the secondary side of the transformer T1 to meet the needs of different loads. The MCU module is also used to set or adjust the duty cycle and flashing frequency of the strobe PWM control signal and the burst PWM control signal, wherein the brightness of the LED light is controlled by adjusting the duty cycle of the strobe PWM control signal and the burst PWM control signal; specifically: In strobe mode: The MCU module receives the strobe pulse signal from the camera and generates a high-frequency strobe PWM control signal based on the strobe pulse signal; The MCU module sets the overall frequency and the overall duty cycle. The overall duty cycle corresponds to the duration of each illumination, that is, the proportion of time the LED light is on in each cycle under the set overall frequency. During each lighting period, the MCU module generates a local strobe PWM control signal with a frequency greater than the overall frequency, and further fine-tunes the actual brightness output of the LED by adjusting the duty cycle of the local strobe PWM control signal. The overall duty cycle determines the on / off rhythm of the LED light within one second, while the local duty cycle is used to precisely control the brightness of the LED light each time it is turned on. In strobe mode: The MCU module receives a strobe pulse signal with a set pulse width from the camera and generates a high-frequency strobe PWM control signal based on the strobe pulse signal. The MCU module sets the overall frequency and overall duty cycle. The overall duty cycle corresponds to the effective time period of the strobe pulse signal, that is, the LED light provides high-brightness illumination during this time period. During each effective time period, the MCU module generates a local strobe PWM control signal with a frequency greater than the overall frequency, and further fine-tunes the actual brightness output of the LED by adjusting the duty cycle of the local strobe PWM control signal. The overall duty cycle determines the duration of an LED's on / off state during a strobe event, while the local duty cycle is used to precisely control the LED's brightness during that on / off period.

2. An integrated control circuit for LED strobe and flashing according to claim 1, characterized in that, The LED signal control module includes: The second MOSFET Q2 is connected to the signal conversion unit; the input terminal of the signal conversion unit is connected to the output of the MCU module, and the output terminal is connected to the gate of the second MOSFET Q2; the drain of the second MOSFET Q2 is connected to the negative terminal pin of the LED in the LED light source module. The signal conversion unit is used to receive the PWM control signal output by the MCU module, convert it into a corresponding switching control signal, and drive the second MOSFET Q2 through the switching control signal. At the same time, it controls the conduction pulse width and frequency of the second MOSFET Q2, thereby controlling the on / off state and brightness of the LED.

3. An integrated control circuit for LED strobe and flashing according to claim 2, characterized in that, The step of generating a corresponding strobe PWM control signal by processing the strobe pulse signal specifically involves: extracting the width information of the strobe pulse signal and generating a corresponding strobe PWM control signal based on the width information.

4. An integrated control circuit for LED strobe and flashing according to claim 3, characterized in that, The AC-DC conversion module is specifically used to convert the incoming AC power into DC power supply voltage and auxiliary power supply voltage; wherein, the DC power supply voltage is the power supply for the LED light source module, and the auxiliary power supply voltage is the power supply for the LED signal control module and the MCU module.

5. An integrated control circuit for LED strobe and flashing according to claim 4, characterized in that, The signal conversion unit includes: The fourth chip U4; the enable pin EN of the fourth chip U4 is connected to one end of the eleventh resistor R11, the ground pin GND is grounded, the input pin IN+ is connected to one end of the thirteenth resistor R13 and then connected to the PWM control signal output by the MCU module, the output pin OUT is connected to one end of the twelfth resistor R12, the power supply pin VDD is connected to one end of the eighth capacitor C8 and the other end of the eleventh resistor R11 and then connected to the auxiliary power supply voltage output by the AC-DC conversion module; the other end of the eighth capacitor C8 is grounded; the other end of the twelfth resistor R12 is connected to one end of the fourteenth resistor R14 and then connected to the gate of the second MOSFET Q2; the other end of the thirteenth resistor R13 is connected to the other end of the fourteenth resistor R14 and then grounded.

6. An integrated control circuit for LED strobe and flashing according to claim 5, characterized in that, In the LED light source module: The positive pin of the LED is connected to the DC power supply voltage output by the AC-DC conversion module, and the negative pin is connected to the drain of the second MOSFET Q2; one end of the current sensing resistor R15 is connected to the source of the second MOSFET Q2, and the other end is grounded with the other end of the fourteenth resistor R14.

7. An integrated control circuit for LED strobe and flashing according to any one of claims 1 to 6, characterized in that, The control chip in the MCU module is an STM32.

8. An integrated control circuit for LED strobe and flashing according to claim 5, characterized in that, The fourth chip U4 is model SGM48539.

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