High-power pulse flash circuit based on LED light source and applied to flash lamp

Abstract

Disclosed in the present invention is a high-power pulse flash circuit based on a light-emitting diode (LED) light source and applied to a flash lamp, comprising: an LED light source group; an energy storage capacitor, having one end electrically connected to the LED light source group, and the other end grounded; an NMOS switch transistor, having a gate electrically connected to a PWM control signal, and a source grounded; a flyback diode, having an input end electrically connected to a drain of the NMOS switch transistor, and an output end electrically connected to an input end of the LED light source group; and a choke inductor, having one end electrically connected to an output end of the LED light source group, and the other end electrically connected to the input end of the flyback diode and the drain of the NMOS switch transistor. The present invention mainly uses a pulse-resistant high-current LED light source to replace a traditional xenon light source on a flash lamp, significantly prolonging the service life of the flash lamp; and compared with traditional LED continuous lamps, an ultra-small LED flash lamp can achieve the photography effect of a larger LED continuous lamp with the power of 50-100 times, the present invention has extremely high portability, in addition, the cost of photography devices is significantly reduced.

Description

A high-power pulsed flash circuit based on LED light source for use in flash lamps Technical Field

[0001] This invention relates to the field of power electronics technology, and in particular to a high-power pulsed flash circuit based on an LED light source applied to a flash lamp. Background Technology

[0002] In today's photography industry, various flash units, as essential lighting equipment for taking photos, still have a strong market demand. Currently, the most common flash unit is the xenon lamp.

[0003] In the process of implementing the flash circuit of the embodiments of this invention, the inventors of this patent have discovered at least the following technical problems in the prior art:

[0004] Using xenon lamps as flashlights results in short lifespan, low luminous efficiency, and the need for high voltage triggering, leading to complex circuitry.

[0005] LED light sources have advantages such as long lifespan and high luminous efficiency. The inventors of this patent considered using LED light sources as flashlights for supplemental lighting in photography. However, when using ordinary LED light sources for supplemental lighting in camera photography, the photos become increasingly dark as the camera shutter speed increases, eventually becoming completely black, failing to achieve the desired supplemental lighting effect. While choosing higher-power LED lamps could appropriately increase brightness, the size and cost of the lamp would double, making it less than ideal.

[0006] In conclusion, existing flash units cannot meet actual usage needs. Summary of the Invention

[0007] This invention provides a high-power pulsed flash circuit, a camera, and a video camera based on an LED light source applied to a flash unit, solving the problem that existing flash units cannot meet practical application needs.

[0008] One embodiment of the present invention provides a high-power pulsed flash circuit based on LED light source for use in flash lamps, comprising: a light-emitting diode (LED) light source group; an energy storage capacitor, one end of which is electrically connected to the LED light source group and the other end of which is grounded; an NMOS switch, the gate of which is electrically connected to a PWM control signal and the source of which is grounded; a freewheeling diode, the input end of which is electrically connected to the drain of the NMOS switch and the output end of which is electrically connected to the input end of the LED light source group; and a choke inductor, one end of which is electrically connected to the output end of the LED light source group and the other end of which is electrically connected to the input end of the freewheeling diode and the drain of the NMOS switch.

[0009] Optionally, the number of light-emitting diode light sources in the light-emitting diode light source group is two or more.

[0010] Optionally, the current amplitudes of two adjacent light-emitting diode light sources are the same.

[0011] Optionally, the current amplitudes of two adjacent light-emitting diode light sources can be different.

[0012] Optionally, the energy storage capacitor is specifically an energy storage capacitor with adjustable energy storage capacity.

[0013] Optionally, the energy storage capacitor is specifically an energy storage capacitor with an adjustable operating voltage.

[0014] Optionally, the flash circuit further includes an MCU electrically connected to the gate of the NMOS switch.

[0015] Optionally, the MCU is specifically an MCU with an adjustable pulse wave duty cycle.

[0016] On the other hand, embodiments of the present invention also provide a camera, including: the flash circuit described in the foregoing embodiments; and a camera body electrically connected to the flash circuit.

[0017] Thirdly, embodiments of the present invention also provide a camera, including: the flash circuit described in the foregoing embodiments; and a camera body electrically connected to the flash circuit.

[0018] One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages:

[0019] This invention primarily achieves the replacement of traditional xenon light sources with pulse-resistant, high-current LED light sources in flash units, significantly improving flash unit lifespan. Due to the higher luminous efficiency of LED light sources, less energy is required for the same flash index. This allows for a significant increase in the total number of flashes while using the same battery capacity, ensuring longer lifespan for portable flash units or compact on-camera flashes and enhancing product competitiveness. Compared to traditional LED constant-on lights, this ultra-compact LED flash unit achieves the photographic effect of a larger LED constant-on light with 50-100 times the power, offering extremely high portability and significantly reducing the cost of photographic equipment. Attached Figure Description

[0020] Figure 1 is a structural diagram of a high-power pulsed flash circuit based on an LED light source applied to a flash lamp according to an embodiment of the present invention;

[0021] Figure 2 is a schematic diagram of the current flow direction of the flash circuit described in Figure 1 when the PWM-H level is high and the NMOS switch is turned on;

[0022] Figure 3 is a schematic diagram of the current flow direction of the flash circuit described in Figure 1 when PWM-L is low and the NMOS switch is turned off;

[0023] Figure 4 shows the waveform of the PWM control signal in the flash circuit described in Figure 1;

[0024] Figure 5 shows the operating current waveform of the LED light source group in the flash circuit described in Figure 1.

[0025] In the diagram: LED1 - Light-emitting diode light source group, EC1 - Energy storage capacitor, D1 - Freewheeling diode, Q1 - NMOS switch. Detailed Implementation

[0026] This invention provides a high-power pulsed flash circuit based on an LED light source for use in flash lamps, which solves the problem that existing flash lamps cannot meet practical application requirements.

[0027] First, the terms appearing in the instruction manual will be explained.

[0028] 1. PWM

[0029] PWM (Pulse Width Modulation) is a method of digitally encoding analog signal levels. Using a high-resolution counter, the duty cycle of a square wave is modulated to encode the level of a specific analog signal. The PWM signal is still digital because at any given moment, the full-amplitude DC power supply is either fully on or fully off. A voltage or current source is applied to the analog load as a repeating pulse sequence of on / off states. On means the DC power supply is applied to the load, and off means the power supply is disconnected.

[0030] The main characteristics of PWM pulses include:

[0031] Duty cycle: The ratio of the time the pulse is at a high level (pulse width) to the total cycle time within a PWM cycle is called the duty cycle. The magnitude of the duty cycle determines the average voltage or current level of the PWM signal.

[0032] Frequency: The frequency of a PWM signal is the reciprocal of its period. It determines how fast the PWM signal changes.

[0033] Resolution: The resolution of a PWM depends on the number of bits in the counter or register used to control the pulse width. The more bits, the higher the resolution and the higher the analog accuracy that can be achieved.

[0034] 2. LED

[0035] LED (Light Emitting Diode) is a solid-state semiconductor device that can convert electrical energy into visible light; it can directly convert electricity into light.

[0036] 3. MCU

[0037] MCU (Microcontroller Unit), also known as a single-chip microcomputer or microcontroller, is an integrated circuit chip that includes a processor, memory, timers, and peripheral devices such as input / output ports.

[0038] To better understand the flash circuit described above, a detailed description of the flash circuit will be provided below with reference to the accompanying drawings and specific embodiments. Obviously, the embodiments described in this invention are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0039] (I) Circuit Structure

[0040] Please refer to Figure 1. The high-power pulsed flash circuit based on LED light source applied to a flash lamp according to the present invention includes:

[0041] LED1, a light-emitting diode light source group;

[0042] One end of the energy storage capacitor EC1 is electrically connected to the input terminal of the light-emitting diode light source group LED1, and the other end is grounded;

[0043] NMOS switch Q1 has its gate electrically connected to the PWM control signal and its source grounded.

[0044] The freewheeling diode D1 has its input terminal electrically connected to the drain of the NMOS switch Q1, and its output terminal electrically connected to the input terminal of the light-emitting diode light source group LED1.

[0045] The choke inductor L1 is electrically connected at one end to the output terminal of the LED light source group LED1, and at the other end to the input terminal of the freewheeling diode D1 and the drain of the NMOS switch Q1.

[0046] In this invention, there is no limitation on the number of LEDs in the LED light source group; the number can be two or more, such as two, five, or ten. In specific applications, the exact number of LEDs can be selected according to actual needs, and this invention does not impose any limitation.

[0047] In a plurality of LED light sources, the current amplitudes of two adjacent LED light sources may be the same or different; this invention does not limit this. In specific applications, depending on actual needs, the current amplitudes of all LED light sources can be set to be the same, or the current amplitudes of all LED light sources can be set to be different, or the current amplitudes of some LED light sources can be set to be the same, while the current amplitudes of other LED light sources can be set to be different. By controlling the current amplitudes of the LED light sources, the flash energy of the flash circuit is adjusted.

[0048] Preferably, the energy storage capacitor is an adjustable energy storage capacitor. By adjusting the energy storage capacity of the energy storage capacitor, the flash energy of the flash circuit can be adjusted.

[0049] Preferably, the energy storage capacitor is an energy storage capacitor with an adjustable operating voltage. The flash energy of the flash circuit can be adjusted by adjusting the operating voltage applied to the energy storage capacitor.

[0050] Preferably, the flash circuit of the present invention further includes an MCU. The MCU is electrically connected to the gate of the NMOS switch. Integrating the MCU and the flash circuit together can meet the needs of different photography and videography scenarios. For example, the flash circuit with its built-in MCU can be seamlessly connected to ordinary cameras and camcorders.

[0051] Preferably, the MCU is an adjustable pulse wave duty cycle MCU. By adjusting the pulse wave duty cycle of the MCU, the overall current of the flash circuit is adjusted, thereby adjusting the flash energy to meet the actual needs of different photography and videography applications. For example, when the pulse wave duty cycle is increased, the current of the choke inductor L1 increases more, resulting in a larger overall current and thus increased flash energy; conversely, when the pulse wave duty cycle is decreased, the current of the choke inductor L1 decreases more, resulting in a smaller overall current and thus decreased flash energy.

[0052] (II) The Role of Electronic Components in Flash Circuits

[0053] Please continue to refer to Figure 1. The functions of each electronic component in the high-power pulsed flash circuit of this invention, based on LED light source application in a flash lamp, are as follows:

[0054] The energy storage capacitor EC1 is used to provide light-emitting energy for the light-emitting diode light source group LED1;

[0055] LED1, as a light-emitting element, is a light source capable of withstanding large-amplitude pulse currents;

[0056] The choke inductor L1 has two functions: first, to limit the current through the LED light source group LED1 to prevent it from burning out due to overcurrent; and second, to stabilize the current of the LED light source group LED1 during a single working PWM pulse group, thus emitting stable light.

[0057] The NMOS switch Q1, as a switching element, is used to control the on-time and off-time of the LED light source group LED1 and the high-level turn-on branch to GND (i.e., ground), so as to adjust the current value of the LED light source group LED1 and the high-level turn-on branch.

[0058] When the NMOS switch Q1 is turned off, the current in the choke inductor L1 cannot change abruptly. The current flows through the freewheeling diode D1 to the light-emitting diode light source group LED1 to form a discharge circuit.

[0059] It should be noted that the high-power pulsed flash circuit based on LED light source applied to flash lamps has a high-level turn-on branch and a low-level turn-off branch.

[0060] The high-level turn-on branch refers to the path through which current flows when the PWM control signal is high and the NMOS switch Q1 is turned on.

[0061] The low-level shutdown branch refers to the discharge circuit through which current flows when the PWM control signal is low and the NMOS switch Q1 is turned off.

[0062] As shown in Figure 2, in the high-level turn-on branch, the current passes through the energy storage capacitor EC1, the light-emitting diode light source group LED1, the choke inductor L1, and the NMOS switch Q1 in sequence.

[0063] As shown in Figure 3, in the low-level off branch, the current passes through the light-emitting diode light source group LED1, the choke inductor L1, and the freewheeling diode D1 in sequence.

[0064] (III) Circuit Operation

[0065] As shown in Figure 4, in the waveform diagram of the PWM control signal, PWM-H represents a high level and PWM-L represents a low level. The PWM pulse group has a fixed width, with a nominal width of 9ms.

[0066] Please refer to Figures 1 and 4 simultaneously. The operation of a high-power pulsed flash circuit based on an LED light source in a flash unit is as follows:

[0067] 1) Before the PWM control signal is given:

[0068] The energy storage capacitor EC1 is charged by the charging power supply and maintained at the set voltage value.

[0069] 2) When a PWM pulse group control signal is issued through the MCU control circuit:

[0070] A) When PWM is high (i.e., PWM-H):

[0071] In the circuit, NMOS switch Q1 is turned on, and energy storage capacitor EC1 discharges through LED light source group LED1, choke inductor L1, and NMOS switch Q1, causing the current of LED light source group LED1 to rise linearly. Among them, choke inductor L1 determines the rising slope.

[0072] B) When PWM is low (i.e., PWM-L):

[0073] When the NMOS switch Q1 in the circuit is turned off, the current of the choke inductor L1 cannot suddenly drop to zero. Instead, it flows through the freewheeling diode D1 to form a discharge circuit to the LED light source group LED1, and the current of the LED light source group LED1 decreases linearly.

[0074] C) The flash energy of the flash lamp is adjusted by regulating the current amplitude of the LED1 light source group. The specific flash energy is determined by the current value of the selected LED1 light source group, which has high pulse current tolerance, the capacitance of the energy storage capacitor EC1, and the operating voltage. The circuit's principle for controlling the current of the LED1 light source group is as follows:

[0075] The average current value of the LED light source group LED1 is adjusted by outputting PWM-H and PWM-L pulse waves at a specific period, limiting the pulse wave length, and adjusting the ratio of the time length of PWM-H and PWM-L within the period. Specifically:

[0076] When the duty cycle is increased, the time ratio of PWM-H to PWM-L increases, the current rise ratio of choke inductor L1 increases, the overall current is larger, achieving the effect of increasing current, which manifests as increased flash energy.

[0077] When the duty cycle is reduced, the time ratio of PWM-H to PWM-L decreases, the current drop of the choke inductor L1 increases, the overall current is smaller, achieving the effect of reducing current, which manifests as a reduction in flash energy.

[0078] This invention also provides a camera, comprising: the flash circuit described in the foregoing embodiments; and a camera body electrically connected to the flash circuit.

[0079] This invention also provides a camera, including: the flash circuit described in the foregoing embodiments; and a camera body electrically connected to the flash circuit.

[0080] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A high-power pulsed flash circuit based on an LED light source applied to a flash lamp, characterized in that, include: LED light source group; The energy storage capacitor has one end electrically connected to the light-emitting diode light source group and the other end grounded. The NMOS switch has its gate electrically connected to the PWM control signal and its source grounded. The freewheeling diode has its input terminal electrically connected to the drain of the NMOS switch and its output terminal electrically connected to the input terminal of the LED light source group. The choke inductor has one end electrically connected to the output terminal of the LED light source group, and the other end electrically connected to the input terminal of the freewheeling diode and the drain of the NMOS switch.

2. The flash circuit as described in claim 1, characterized in that, The number of light-emitting diodes in the light-emitting diode light source group is two or more.

3. The flash circuit as described in claim 2, characterized in that, The current amplitudes of two adjacent light-emitting diode light sources are the same.

4. The flash circuit as described in claim 3, characterized in that, The current amplitudes of two adjacent light-emitting diode (LED) sources are different.

5. The flash circuit as described in claim 4, characterized in that, The energy storage capacitor is specifically an energy storage capacitor with adjustable energy storage capacity.

6. The flash circuit as described in claim 5, characterized in that, The energy storage capacitor is specifically an energy storage capacitor with an adjustable operating voltage.

7. The flash circuit as described in claim 6, characterized in that, The flash circuit also includes: The MCU is electrically connected to the gate of the NMOS switch.

8. The flash circuit as described in claim 7, characterized in that, Specifically, the MCU is an MCU with an adjustable pulse wave duty cycle.

9. A camera, characterized in that, include: The flash circuit as described in any one of claims 8; The camera body is electrically connected to the flash circuit.

10. A camera, characterized in that, include: The flash circuit as described in any one of claims 8; The main camera is electrically connected to the flash circuit.

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