LED drive circuit, drive circuit board, drive chip and endoscope

Abstract

The invention provides an LED drive circuit, a drive circuit board, a drive chip and an endoscope. The LED driving circuit comprises a boosting unit, a first resistor and a second resistor, the power end of the boosting unit is connected with a power supply; the input grounding end of the boosting unit is grounded; the first output end of the boosting unit is connected with the first end of the first resistor; the second output end of the boosting unit is connected with the first end of the second resistor, and the first end of the second resistor is also used for being connected with the negative electrode end of the LED array; the output grounding end of the boosting unit and the second end of the second resistor are grounded; the second end of the first resistor is used for being connected with the positive electrode end of the LED array. And the boosting unit is used for adaptively adjusting the output voltage of the LED driving circuit according to the scale of the LED array, and the output voltage is used for driving the LED array to be lightened. The method and the device are used for achieving the effects of dynamically adapting to the scale change of the LED array and improving the hot plug protection of the LED.

Description

Technical Field

[0001] This application relates to the field of LED driver circuit design technology, and in particular to an LED driver circuit, driver circuit board, driver chip and endoscope. Background Technology

[0002] In medical procedures or diagnostics, endoscopes are crucial instruments for observing internal cavities of the human body. Endoscopes require high-brightness, high-stability light-emitting diode (LED) light sources to illuminate target areas within the cavity in real time. The quality of the LED light source directly affects image clarity and surgical safety.

[0003] In related technologies, DC regulated power supplies are typically used to drive LED lighting. Specifically, such as... Figure 1 As shown, the LED driver circuit includes a switching unit, such as a MOSFET or a transistor. The source terminal of the switching unit serves as the first input terminal of the LED driver circuit, used to connect to a DC regulated power supply. The gate terminal of the switching unit serves as the second input terminal of the LED driver circuit, used to input a Pulse Width Modulation (PWM) dimming signal. The drain terminal of the switching unit serves as the output terminal of the LED driver circuit, used to connect to the positive terminal of the LED array, while the negative terminal of the LED array is grounded. When the PWM signal is high, the switching unit is turned on, the LED driver circuit outputs a constant voltage, and the LED is lit. When the PWM signal is low, the switching unit is turned off, and the LED is off.

[0004] However, with the increasing demands for lighting in medical surgeries, achieving optimal imaging results for endoscopes requires flexible configuration of varying numbers of LEDs based on different clinical scenarios, while ensuring absolute safety and flicker-free operation during hot-swapping. Under these conditions, the aforementioned driving solutions suffer from limitations in dynamically adapting to changes in the number of LEDs and insufficient protection against LED hot-swapping.

[0005] Therefore, there is an urgent need for a new type of LED driving circuit specifically designed for endoscopes to meet the lighting requirements of medical endoscopes. Summary of the Invention

[0006] This application provides an LED driver circuit, driver circuit board, driver chip, and endoscope to solve the problems that existing driver solutions typically cannot dynamically adapt to changes in the number of LEDs and have insufficient protection against LED hot-swapping.

[0007] In a first aspect, this application provides an LED driving circuit, comprising: a boost unit, a first resistor, and a second resistor, wherein:

[0008] The power supply end of the voltage boosting unit is used for connecting a power supply; the input ground end of the voltage boosting unit is grounded; the first output end of the voltage boosting unit is connected with the first end of the first resistor; the second output end of the voltage boosting unit is connected with the first end of the second resistor, and the first end of the second resistor is also used for connecting with the negative electrode end of the LED array; the output ground end of the voltage boosting unit is grounded together with the second end of the second resistor;

[0009] The second end of the first resistor is used for connecting with the positive electrode end of the LED array.

[0010] The voltage boosting unit is used for adaptively adjusting the output voltage of the LED driving circuit according to the scale of the LED array, and the output voltage is used for driving the LED array to light up.

[0011] In a possible implementation, the LED driving circuit further comprises a switching unit, the input end of the switching unit is connected with the second end of the first resistor, and the output end of the switching unit is used for connecting with the positive electrode end of the LED array.

[0012] When the voltage at the second end of the first resistor is greater than the conduction voltage of the switching unit, the switching unit is turned on, and the LED array is lit up.

[0013] In a possible implementation, the switching unit comprises a first diode, the cathode end of the first diode is used as the input end of the switching unit, and the anode end of the first diode is used as the output end of the switching unit.

[0014] In a possible implementation, the first diode is a voltage stabilizing diode.

[0015] In a possible implementation, the LED driving circuit further comprises a third resistor, the first end of the third resistor is connected with the output end of the switching unit, and the second end of the third resistor is grounded.

[0016] In a possible implementation, the voltage boosting unit further comprises an input end used for connecting with a PWM dimming signal.

[0017] The low-pass filter is integrated in the voltage boosting unit, and the voltage boosting unit is further used for adaptively adjusting the output voltage of the LED driving circuit according to the PWM dimming signal and the feedback voltage at the second end of the second resistor, and controlling the output current of the LED driving circuit to be stabilized at a preset constant value.

[0018] In a possible implementation, the voltage boosting unit comprises a voltage boosting chip, a voltage boosting inductor, a second diode and a voltage boosting capacitor; wherein,

[0019] The first end of the boost chip is used as a power end of the boost unit, and the first end of the boost chip is connected with the first end of the boost inductor; the second end of the boost chip is used as an input ground end of the boost unit; the third end of the boost chip is used for inputting a PWM dimming signal; the fourth end of the boost chip, the cathode end of the second diode and the positive end of the boost capacitor are connected together, and the connected end is used as a first output end of the boost unit; the fifth end of the boost chip is used as a second output end of the boost unit; the sixth end of the boost chip is connected with the negative end of the boost capacitor, and the connected end is used as an output ground end of the boost unit.

[0020] The anode end of the second diode is connected with the second end of the boost inductor.

[0021] In a second aspect, the application provides a driving circuit board, comprising the LED driving circuit of any one of the first aspect.

[0022] In a third aspect, the application provides a driving chip, comprising the LED driving circuit of any one of the first aspect, or the driving chip comprises the driving circuit board of the second aspect.

[0023] In a fourth aspect, the application provides an endoscope, comprising an LED array and the LED driving circuit of any one of the first aspect, or the endoscope comprises the LED array and the driving circuit board of the second aspect, or the endoscope comprises the LED array and the driving chip of the third aspect.

[0024] The LED driving circuit, the driving circuit board, the driving chip and the endoscope provided by the application, wherein the LED driving circuit comprises: a boosting unit, a first resistor and a second resistor; a power supply end of the boosting unit is used for connecting a power supply; an input ground end of the boosting unit is grounded; a first output end of the boosting unit is connected with a first end of the first resistor; a second output end of the boosting unit is connected with a first end of the second resistor, and the first end of the second resistor is also used for connecting with a negative electrode end of an LED array; an output ground end of the boosting unit and a second end of the second resistor are both grounded; a second end of the first resistor is used for connecting with a positive electrode end of the LED array; the boosting unit is used for adaptively adjusting an output voltage of the LED driving circuit according to a scale of the LED array, and the output voltage is used for driving the LED array to light up. Since the forward voltage required for lighting up the LED array changes when the scale of the LED array changes, the boosting unit dynamically adjusts the output voltage of the boosting unit by detecting the scale of the LED array, so as to accurately stabilize the output voltage at the level required for lighting up the LED array, thereby ensuring that the LED array always obtains stable and appropriate driving voltage regardless of the change of the scale of the LED array, so as to stabilize the light emission. The adaptive mechanism also greatly suppresses the impact of current and voltage in the hot plug process, thereby improving the safety. The first resistor serves as a current limiting protection resistor, and the highest current is limited through the resistor, thereby effectively preventing the LED in the LED array from being burned out due to the sudden increase of the current. In addition, the adaptability to different LED array scales improves the versatility of the LED driving circuit and reduces the production and maintenance costs. The harsh requirements of safety, reliability, stability and flexibility for medical endoscope illumination are met. BRIEF DESCRIPTION OF DRAWINGS

[0025] The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate embodiments consistent with the present application and, together with the description, further serve to explain the principles of the application.

[0026] Figure 1 The LED driving circuit provided in the related art;

[0027] Figure 2 The structure diagram of the LED driving circuit provided in the embodiment of the application Figure 1 ;

[0028] Figure 3 The structure diagram of the LED driving circuit provided in the embodiment of the application Figure 2 .

[0029] Through the above drawings, the specific embodiments of the application have been shown, and more detailed descriptions will be given hereinafter. These drawings and textual descriptions are not intended to limit the scope of the concept of the application by any means, but to illustrate the concept of the application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0030] The exemplary embodiments will be described in detail herein with reference to the attached drawings. In the following description, like reference numerals refer to like elements, unless the context clearly dictates otherwise. The following description of exemplary embodiments is not representative of all possible embodiments consistent with the present application. Instead, it is merely intended to provide an example of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0031] The terms "first", "second", and the like, herein and in the claims, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the use of such terms as "first" and "second" are arbitrary labels and are used merely for purposes of distinguishing between the elements being described. Furthermore, these terms are not necessarily used in a sequence monotonically increasing sense, but are used merely as distinct references to elements. The terms "comprises", "comprising", "includes", "including", "has", "having" and the like, are inclusive and are used as equivalents for "consisting of" and "consisting essentially of" and are open-ended, allowing for the inclusion of additional elements or steps without departing from the scope of the application. The terms "may" and "may be" are used in their potential sense, meaning that there is an expected possibility of events occurring.

[0032] In medical practice, different models of endoscopes may have different numbers of LED light beads (for example, some use 3 in series, and some use 5 in series), and hot swapping of endoscopes may be required during surgery. Figure 1 The LED driving circuit shown in the prior art cannot dynamically adapt to changes in the number of LEDs. For example, when the number of LEDs increases, in order to ensure that the output power of all LEDs meets the illumination requirements of the endoscope, the topology or parameters of the LED driving circuit need to be changed, resulting in high cost and poor versatility. Moreover, current surges are easily caused during hot swapping. For example, when new LEDs are connected, the instantaneous output current of the circuit may exceed the rated value of the LEDs, causing the LEDs to burn out. When the LEDs are removed, the current of the remaining LEDs may suddenly increase, causing overload. Although some solutions control the on-off of the LEDs by adding MOS switches, additional circuit design is required, and the switching action of the MOS may introduce voltage fluctuations, ultimately resulting in insufficient protection during hot swapping.

[0033] To solve the above problems, the LED driving circuit provided by the present application is based on the design of a boost unit, which adjusts the output voltage of the LED driving circuit adaptively, realizes flexible configuration of the size of the LED array, and does not need to adjust the circuit topology or parameters. The adaptive mechanism also greatly suppresses the current and voltage surges during hot swapping, improving safety. The introduction of the current-limiting resistor effectively prevents the LEDs in the LED array from being burned out due to a sudden increase in current.

[0034] The technical solutions of the present application and how the technical solutions of the present application solve the above technical problems will be described in detail below with specific examples. The following specific examples can be combined with each other, and the same or similar concepts or processes can not be described again in some examples. The embodiments of the present application will be described below with reference to the drawings.

[0035] Figure 2 Structure diagram of the LED driving circuit provided by the embodiments of the present application Figure 1 As shown in the structure diagram of the LED driving circuit provided by the embodiments of the present application, Figure 2 the LED driving circuit comprises a boost unit, a first resistor and a second resistor, wherein:

[0036] The power supply end of the boost unit is used for connecting a power supply; the input ground end of the boost unit is grounded; the first output end of the boost unit is connected with the first end of the first resistor; the second output end of the boost unit is connected with the first end of the second resistor, and the first end of the second resistor is also used for connecting with the negative electrode end of the LED array; the output ground end of the boost unit and the second end of the second resistor are both grounded;

[0037] The second end of the first resistor is used for connecting with the positive electrode end of the LED array;

[0038] The boost unit is used for adaptively adjusting the output voltage of the LED driving circuit according to the scale of the LED array, and the output voltage is used for driving the LED array to light up.

[0039] For example, the power supply is a direct current power supply working in the range of 2.7V~5.5V, for example, the power supply is a medical rechargeable lithium battery with a rated voltage of 3.7V. The positive electrode of the power supply is connected to the power supply end of the boost unit, and the negative electrode is connected to the input ground end (GND) of the boost unit.

[0040] The boost unit is, for example, a boost type LED driving controller integrated with a power switch, the power supply end of which is connected to the above-mentioned 3.7V power supply, the input ground end of which is connected to the power supply ground, the first output end of which is connected to the first end of the first resistor as a boosted voltage node, and the second end of the first resistor is connected to the positive electrode end of the LED array. The first resistor is usually a small resistance resistor, for example, the first resistor is a 10Ω current limiting protection resistor. By selecting the resistance value of the first resistor, the maximum current in the LED driving circuit can be set, which needs to be within the safe working current range of the LED array. The second output end of the boost unit can be regarded as a feedback pin, which is connected with the first end of the second resistor and the negative electrode end of the LED array at a node. The output ground end of the boost unit can be regarded as a power ground, which is grounded together with the second end of the second resistor.

[0041] The LED array is composed of N LEDs in series, or in parallel, or in series-parallel. The positive terminal is connected to the second terminal of the first resistor, and the negative terminal is connected to the first terminal of the second resistor (i.e. the feedback node).

[0042] It should be noted that the boost unit adopts a constant current control mechanism, so that the output current (i.e. LED current) of the LED driving circuit is stabilized at a preset constant value. In addition, the output current is not directly measured, but the measurement of the output current is realized by detecting the voltage at the first terminal of the second resistor.

[0043] For example, the boost unit stabilizes the voltage of the feedback pin at 200mV, since the feedback pin is connected to the first terminal of the second resistor (i.e. the feedback node), i.e. the voltage across the second resistor is fixed at 200mV. Taking the second resistor as 2Ω for example, according to Ohm's law, the current I_LED flowing through the second resistor (i.e. the entire LED array) is 0.2 / 2, i.e. 100mA. By changing the resistance value of the second resistor, the constant current of the LED can be accurately set. In this embodiment, the second resistor can be understood as the setting resistor of the LED array current.

[0044] The output voltage V_out of the LED driving circuit is the sum of the total forward voltage drop V_LEDs of the LED array, the voltage drop V_R1 of the first resistor and the voltage drop V_R2 of the second resistor, i.e. V_out=V_LEDs+V_R1+V_R2. Among them, the voltage drop V_R2 of the second resistor is constant, for example, V_R2 is 200mV, the first resistor is 10Ω, the voltage drop V_R1 of the first resistor is I_LED R1=0.1A 10Ω=1V, then the output voltage V_out of the LED driving circuit is V_LEDs+1.2V. When the scale of the LED array is expanded to cause V_LEDs to increase, in order to maintain a constant I_LED, the boost unit will automatically adjust the output voltage V_out to be higher; otherwise, the output voltage V_out will be lowered. Thus, the output voltage is adaptively adjusted according to the scale of the LED array.

[0045] For example, after each power-up of the LED driving circuit, the boost unit will automatically detect the scale of the LED array, and then adaptively adjust the output voltage according to the scale of the LED array to drive the LED array to light up.

[0046] As can be seen from the above embodiments, the first resistor serves as a current-limiting protection resistor, which can effectively limit the peak current in abnormal situations (such as instantaneous impact), and cooperates with the constant current control to provide double protection for the LED to prevent the LED from being burned out. The second resistor serves as a current-limiting resistor of the LED current loop, and provides a feedback voltage for the boost unit. The boost unit maintains the current of the LED array at a preset constant value by monitoring the feedback voltage at the first end of the second resistor, ensures the constant current output of the LED driving circuit, and adaptively adjusts the output voltage according to the size of the LED array.

[0047] For example, when the LED array is unplugged (for example, the head module of a dynamic plug-in endoscope, causing the LED to be hot-plugged), the feedback voltage at the first end (i.e., the feedback node) of the second resistor will be much higher than 200 mV, triggering the fault protection mechanism (such as turning off the output) of the boost unit, which can ensure the safety of the circuit interface.

[0048] Through the above LED driving circuit, not only a constant driving current can be provided for the LED array, but also the output voltage can be automatically adjusted according to the size (such as the number of series-connected LEDs) of the LED array, achieving dynamic adaptation.

[0049] Since the forward voltage required to light up the LED array changes when the size of the LED array changes, the boost unit dynamically adjusts the output voltage of the boost unit by detecting the size of the LED array, so as to accurately stabilize the output voltage at the level required to light up the LED array, achieving that no matter how the size of the LED array changes, the LED driving circuit can ensure that the LED array always obtains a stable and appropriate driving voltage, thereby stabilizing the light emission. The adaptive mechanism also greatly suppresses the impact of current and voltage during hot plugging, improving safety. The first resistor serves as a current-limiting protection resistor, which limits the maximum current through the resistor, effectively preventing the LEDs in the LED array from being burned out due to a sudden increase in current. In addition, the adaptability to different LED array sizes improves the versatility of the LED driving circuit, reduces production and maintenance costs, and meets the stringent requirements of medical endoscope illumination for safety, reliability, stability and flexibility.

[0050] In some embodiments, the LED driving circuit further comprises a switching unit, an input end of the switching unit is connected with the second end of the first resistor, and an output end of the switching unit is used to be connected with the positive electrode end of the LED array; when the voltage at the second end of the first resistor is greater than the on-voltage of the switching unit, the switching unit is turned on, and the LED array is lit up.

[0051] It should be understood that the switch unit forms a voltage-controlled automatic switch. After the LED driving circuit is powered on, the boost unit starts to work. As the output voltage of the boost unit (herein referred to as the voltage at the second end of the first resistor) rises, when the voltage is greater than the on-voltage of the switch unit, the switch unit is fully turned on, the current flows into the LED array, and the LED is lit. Then, the boost unit continues to maintain a constant LED current and an adaptive output voltage according to the feedback voltage of the first end of the second resistor (i.e., the feedback node).

[0052] It should be noted that the on-resistance of the switch unit is extremely small, and has little effect on the current. The on-voltage of the switch unit can be appropriately selected according to the supply voltage.

[0053] For ease of understanding, it is illustrated by way of example that, when the supply voltage is 3.3V and the LED array is a single 2.8V LED, if there is no switch unit, the LED will be directly lit after the LED driving circuit is powered on. However, when the switch unit with an on-voltage of 3.3V or above is provided in the LED driving circuit, the output voltage of the boost unit (i.e., the voltage at the second end of the first resistor) needs to be greater than the on-voltage of the switch unit, so that the switch unit can be turned on to light the LED, thereby realizing the control of the switching of the LED.

[0054] The switch unit effectively prevents the large current from impacting the LED array when the output voltage is unstable at the initial stage of powering on the LED driving circuit, realizes smooth starting, and thereby protects the LED. If the input voltage is too low or the output voltage is reduced due to a fault, when the output voltage of the boost unit is lower than the on-voltage of the switch unit, the switch unit will automatically cut off, cutting off the LED loop, preventing the LED array from working in an abnormal state of low voltage, and realizing under-voltage protection. The switch unit is voltage self-driven, does not require an additional control circuit, and has a simple structure. The switch unit also realizes automatic control of lighting of the LED.

[0055] By way of example, the switch unit includes a first diode and a P-MOSFET. The source of the P-MOSFET is connected to the second end of the first resistor, the drain of the P-MOSFET is connected to the positive terminal of the LED array, the gate of the P-MOSFET is grounded, the cathode of the first diode is connected to the source of the P-MOSFET, and the anode of the first diode is connected to the gate of the P-MOSFET through a resistor.

[0056] By way of example, in some implementations, the switch unit includes a first diode. The cathode of the first diode serves as the input end of the switch unit, and the anode of the first diode serves as the output end of the switch unit.

[0057] For example, the switch unit can be composed of two first diodes in parallel, or the switch unit includes one first diode. The two first diodes in parallel are redundant to each other, for example, if one of the first diodes is disconnected due to hardware failure, the other first diode can normally realize the switching function.

[0058] Specifically, in some embodiments, the first diode is a zener diode. The zener diode in this embodiment only serves as a switch. When the zener diode is turned on, the LED is lit, and when the zener diode is turned off, the LED is extinguished, thereby preventing the LED from being unable to be turned off.

[0059] In the embodiments of the present application, the switch unit is connected in series between the LED driving circuit and the LED array, which can automatically control the timing of the LED lighting. The output voltage of the LED driving circuit itself is used as a control signal, and the switch unit is only turned on when the voltage is high enough to ensure the normal and stable operation of the LED, thereby realizing the functions of soft start and under-voltage shutdown, and further enhancing the reliability and safety of the endoscope illumination system.

[0060] In some embodiments, the LED driving circuit further includes a third resistor, a first end of the third resistor being connected to the output end of the switch unit, and a second end of the third resistor being grounded.

[0061] The third resistor can be regarded as a discharge resistor, and its resistance value is relatively large. Its main function is to provide a safe charge discharge path for the LED array after the LED array is powered off.

[0062] For example, when the switch unit is turned on, the current flowing through the third resistor is small due to the large resistance value of the third resistor, and the current on the third resistor can be ignored relative to the current flowing into the LED array. When the power supply is cut off or the endoscope provided with the LED driving circuit is hot-plugged out, the boost unit and the switch unit stop working, but at this time, the LED array itself and some capacitors connected thereto still store charges, so that the positive terminal of the LED array is maintained at a relatively high voltage. If the residual charge is not discharged, a large current pulse will be generated due to the high voltage when the next power-on or insertion occurs, which will damage the LED or the LED driving circuit. In the case where the third resistor is provided in the LED driving circuit, the residual charge will form a loop through the third resistor and be discharged slowly. The speed of discharge is determined by the resistance value of the third resistor and the total capacitance in the circuit. The smaller the resistance value of the third resistor, the faster the discharge. Therefore, the third resistor effectively prevents secondary damage and electric shock risk caused by residual voltage, that is, the setting of the third resistor realizes the discharge protection of the residual voltage in the LED driving circuit.

[0063] The third resistor (discharge resistor) is arranged between the output end of the switch unit and the ground, thereby adding a key safety and protection layer to the whole LED driving circuit. The residual charge problem of the high-voltage LED array after power-off is solved, and the safety, reliability and user experience of the medical endoscope LED driving circuit are significantly improved.

[0064] In some embodiments, the boost unit further comprises an input end for accessing the PWM dimming signal; a low-pass filter is integrated in the boost unit, and the boost unit is further configured to adaptively adjust the output voltage of the LED driving circuit according to the PWM dimming signal and the feedback voltage at the second end of the second resistor, and control the output current of the LED driving circuit to be stable at a preset constant value.

[0065] As shown in Figure 3 The structure of the LED driving circuit provided by the embodiments of the present application is shown in Figure 2 In some embodiments, the boost unit comprises a boost chip, a boost inductor, a second diode and a boost capacitor; the first end of the boost chip is used as the power end of the boost unit, and the first end of the boost chip is connected with the first end of the boost inductor; the second end of the boost chip is used as the input ground end of the boost unit; the third end of the boost chip is used for accessing the PWM dimming signal; the fourth end of the boost chip, the cathode end of the second diode and the positive end of the boost capacitor are connected together, and the connected end is used as the first output end of the boost unit; the fifth end of the boost chip is used as the second output end of the boost unit; the sixth end of the boost chip is connected with the negative end of the boost capacitor, and the connected end is used as the output ground end of the boost unit; the anode end of the second diode is connected with the second end of the boost inductor.

[0066] The boost chip is internally integrated with a switch tube, such as a 1.35A NMOS switch tube, which stores energy for voltage boosting through the boost inductor. When the switch tube in the boost chip is turned on, the second diode is turned off, which is used to prevent the charge stored in the boost capacitor from flowing back to the ground, so as to ensure that the energy is only delivered to the LED array; when the switch tube in the boost chip is turned off, the second diode is turned on, and the energy stored in the boost inductor charges the boost capacitor through the second diode and supplies power to the LED array. In the stage when the switch tube is turned off and the second diode is turned on, the boost inductor and the power supply together charge the capacitor; in the stage when the switch tube is turned on and the second diode is turned off, the boost capacitor alone undertakes the task of supplying power to the load (i.e. the LED array), and discharges itself. Through the charging-discharging cycle, the pulsed input voltage is smoothed into a stable and small-ripple DC output voltage. For example, the charging-discharging cycle is repeated at a very high frequency (e.g. 1.1MHz), and finally the lower input voltage (e.g. 2.7V~5.5V) is boosted to a higher and stable output voltage (e.g. up to 38V) to drive the LED array to light up.

[0067] In addition, when a transient change in load occurs (e.g., the LED suddenly needs a larger current), the boost capacitor can quickly provide or absorb the transient current, preventing a large drop or overshoot in the output voltage.

[0068] For example, the PWM dimming signal is generated by an external control unit, and the frequency range of the PWM dimming signal is, for example, 2KHz~60KHz. For example, the external control unit provides a PWM dimming signal with a duty cycle D, and the duty cycle D represents the target brightness level. The received PWM dimming signal is smoothed by a low-pass filter integrated in the boost unit (specifically, a boost chip), such as a 600Hz low-pass filter, to obtain a smooth brightness reference analog signal. The boost unit continuously monitors the feedback voltage at the first end of the second resistor and dynamically adjusts the PWM duty cycle to ensure that the feedback voltage is always stable at, for example, 200mV, thereby achieving precise dimming of the output current with linear variation of the PWM duty cycle, smooth variation of the DC voltage, avoiding sudden changes in current, and achieving flicker-free dimming. The PWM duty cycle represents the brightness level of the LED, and the greater the PWM duty cycle, the higher the brightness of the LED.

[0069] In the embodiments of the present application, a high-frequency PWM digital dimming signal is converted into a smooth DC analog reference voltage by a low-pass filter integrated in the boost unit, and the voltage is used to precisely modulate the reference of constant current control, thereby eliminating LED flicker in the dimming process at the root, eliminating the influence of LED flicker on the visual recognition of doctors, improving the image quality during the operation, and further improving the accuracy of medical diagnosis.

[0070] Next, the present application provides a driving circuit board, comprising: the LED driving circuit in the above-mentioned LED driving circuit embodiment.

[0071] The LED driving circuit is integrated on the driving circuit board, which can achieve wide-range voltage adaptive driving. For example, when different models (LED array scales are different) of endoscopes are connected, the driving circuit board can automatically detect and adaptively output a voltage that meets the lighting requirements of the LED array of the endoscope, and ensure that the brightness of the LED array is consistent. By receiving an external PWM dimming signal, the driving circuit board can perform smooth and flicker-free brightness adjustment within the full brightness range. In addition, hot plug safety protection is provided.

[0072] It should be noted that the specific implementation of the driving circuit board can be referred to the above-mentioned embodiments of the LED driving circuit, which will not be described here again.

[0073] The present application provides a driving chip, which comprises the LED driving circuit in the above-mentioned LED driving circuit embodiment; or, the driving chip comprises the driving circuit board in the above-mentioned embodiment.

[0074] The application also provides an endoscope, which comprises the LED array and the LED driving circuit in the above-mentioned embodiments, or the endoscope comprises the LED array and the driving circuit board, or the endoscope comprises the LED array and the driving chip.

[0075] Those skilled in the art can understand that all or part of the steps of the above-mentioned method embodiments can be completed by program instruction related hardware. The foregoing program can be stored in a computer readable storage medium. The program executes the steps of the above-mentioned method embodiments when executed; and the foregoing storage medium includes ROM, RAM, magnetic disc or optical disc and various storage medium capable of storing program codes.

[0076] Finally, it should be noted that other embodiments of the present application will readily occur to those skilled in the art upon consideration of the specification and practice of the application disclosed herein. The present application is intended to cover any variations, uses or adaptive changes of the present application following the general principles of the present application and including known or customary technical means in the art not disclosed by the present application, and is not limited to the precise structures described above and shown in the drawings, and various modifications and changes can be made without departing from the scope thereof. The scope of the present application is only limited by the appended claims.

Claims

1. An LED driving circuit, characterized in that, include: The boost unit, the first resistor, and the second resistor, wherein: The power supply terminal of the boost unit is used to connect to the power supply; the input ground terminal of the boost unit is grounded; the first output terminal of the boost unit is connected to the first terminal of the first resistor; the second output terminal of the boost unit is connected to the first terminal of the second resistor, and the first terminal of the second resistor is also used to connect to the negative terminal of the LED array; the output ground terminal of the boost unit and the second terminal of the second resistor are both grounded. The second end of the first resistor is used to connect to the positive terminal of the LED array; The boost unit is used to adaptively adjust the output voltage of the LED driving circuit according to the size of the LED array, and the output voltage is used to drive the LED array to light up.

2. The LED driving circuit according to claim 1, characterized in that, The LED driving circuit further includes a switching unit, the input terminal of which is connected to the second terminal of the first resistor, and the output terminal of which is connected to the positive terminal of the LED array. When the voltage at the second end of the first resistor is greater than the on-state voltage of the switching unit, the switching unit is turned on, and the LED array is lit.

3. The LED driving circuit according to claim 2, characterized in that, The switching unit includes a first diode, with the cathode of the first diode serving as the input terminal of the switching unit and the anode of the first diode serving as the output terminal of the switching unit.

4. The LED driving circuit according to claim 3, characterized in that, The first diode is a Zener diode.

5. The LED driving circuit according to claim 2, characterized in that, The LED driving circuit also includes a third resistor, the first end of which is connected to the output terminal of the switching unit, and the second end of which is grounded.

6. The LED driving circuit according to any one of claims 1 to 5, characterized in that, The boost unit also includes an input terminal for receiving pulse width modulation dimming signals; The boost unit integrates a low-pass filter. The boost unit is also used to adaptively adjust the output voltage of the LED driving circuit according to the pulse width modulation dimming signal and the feedback voltage at the second end of the second resistor, and control the output current of the LED driving circuit to stabilize at a preset constant value.

7. The LED driving circuit according to claim 6, characterized in that, The boost unit includes a boost chip, a boost inductor, a second diode, and a boost capacitor; wherein, The first terminal of the boost chip serves as the power supply terminal of the boost unit, and is connected to the first terminal of the boost inductor; the second terminal of the boost chip serves as the input ground terminal of the boost unit; the third terminal of the boost chip is used to receive a pulse width modulation (PWM) dimming signal; the fourth terminal of the boost chip, the cathode of the second diode, and the positive terminal of the boost capacitor are connected together, and this common connection terminal serves as the first output terminal of the boost unit; the fifth terminal of the boost chip serves as the second output terminal of the boost unit; the sixth terminal of the boost chip is connected together with the negative terminal of the boost capacitor, and this common connection terminal serves as the output ground terminal of the boost unit. The anode of the second diode is connected to the second terminal of the boost inductor.

8. A driving circuit board, characterized in that, Includes the LED driving circuit as described in any one of claims 1 to 7.

9. A driver chip, characterized in that, The LED driving circuit includes any one of claims 1 to 7, or the driving chip includes the driving circuit board of claim 8.

10. An endoscope, characterized in that, The endoscope includes an LED array and an LED driving circuit as described in any one of claims 1 to 7, or the endoscope includes an LED array and a driving circuit board as described in claim 8, or the endoscope includes an LED array and a driving chip as described in claim 9.

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