A high-power, brightness-adjustable cold light source for endoscopes and its control system

Abstract

The present invention belongs to the field of endoscope light source and endoscope light source control system, and relates to an endoscope cold light source with high power and adjustable brightness, including: a 48V switching power supply, a positive and negative 12V and 5V switching power supply, a cold light source main circuit, a cold light source control circuit, a human-machine interface circuit and a remote control interface circuit, wherein: the 48V switching power supply provides power for the cold light source main circuit; the positive and negative 12V and 5V switching power supplies provide power for other circuits other than the cold light source main circuit; the 48V direct current of the cold light source main circuit is converted into low-voltage high-frequency alternating current through a push-pull transformer, and then a direct current voltage is obtained through synchronous rectification and LC filtering, and the direct current voltage drives a high-power LED to emit light through a linear power MOSFET tube; the human-machine interface circuit and the remote control interface circuit are respectively used to set the LED current output percentage locally and remotely. The endoscope cold light source of the present invention has the characteristics of high power, adjustable brightness, and extremely small brightness fluctuation. The present invention also provides an endoscope cold light source control system with high power and adjustable brightness.

Description

Technical Field

[0001] The invention belongs to the field of endoscope light sources and endoscope light source control systems, and relates to a high-power, brightness-adjustable endoscope cold light source and a control system thereof. Background Art

[0002] With the development of LED technology, high-power LED lighting is increasingly used, and it has become a trend to use high-power LEDs instead of xenon lamps in the field of medical equipment. In order to simplify the LED drive circuit, the usual LED lighting uses a single-loop current feedback switching power supply. With the increasing demand for high-quality and high-definition endoscopes, from 1080P to 4K resolution, and then to the emergence of 8K and 3D stereoscopic video endoscopes, the demand for the quality of the light source supporting the endoscope is constantly increasing. At the same time, the frame rate of endoscopic video images is also constantly increasing, from 30 frames per second to 60 frames and possibly 120 frames in the future, all of which put forward new requirements for the light source of the endoscope. Summary of the invention

[0003] Aiming at the new demand of high-quality endoscopes for their supporting light sources, the present invention provides an endoscope cold light source with high power and adjustable brightness.

[0004] The invention also provides a high-power and brightness-adjustable endoscope cold light source control system.

[0005] The high-power and adjustable brightness endoscope cold light source of the present invention is realized by the following technical solution:

[0006] A high-power and brightness-adjustable cold light source for endoscopes, comprising: a 48V switching power supply, positive and negative 12V and 5V switching power supplies, a cold light source main circuit, a cold light source control circuit, a human-machine interface circuit and a remote control interface circuit, wherein:

[0007] The 48V switching power supply provides power for the main circuit of the cold light source; the positive and negative 12V and 5V switching power supplies provide power for other circuits outside the main circuit of the cold light source; the 48V DC of the main circuit of the cold light source is converted into low-voltage and high-frequency AC through a push-pull transformer, and then a DC voltage is obtained through synchronous rectification and LC filtering. The DC voltage drives the high-power LED to emit light through a linear power MOSFET tube; the human-machine interface circuit and the remote control interface circuit are used to set the LED current output percentage locally and remotely respectively.

[0008] Preferably, the output current of the endoscope cold light source can be adjusted from 10% to 100% in 5% steps.

[0009] Preferably, the main circuit of the cold light source includes: a push-pull high-frequency transformer, a primary-side driving circuit, a secondary-side self-driven synchronous rectification and filtering circuit, a high-power LED and its light-emitting driving circuit; wherein: the primary-side driving circuit uses a linear MOSFET power tube to drive the push-pull high-frequency transformer; the secondary-side self-driven synchronous rectification and filtering circuit uses a power MOSFET transistor with an on-resistance of 1.8 milliohms instead of a conventional rectifier diode.

[0010] Preferably, the cold light source control circuit includes: an output current detection circuit, MCU control software and peripheral logic circuit, an output current control circuit, an output voltage detection and DS differential voltage detection circuit and a primary side current detection resistor, wherein: the MCU control software and the peripheral logic circuit provide the output current control circuit with an LED output current setting value.

[0011] Preferably, the output current detection circuit, the output current control circuit, the high-power LED and its light-emitting drive circuit form a high-power LED current control loop.

[0012] Preferably, a push-pull high-frequency transformer, a primary-side driving circuit, a secondary-side self-driven synchronous rectification and filtering circuit, an output voltage detection and DS differential pressure detection circuit, a primary-side current detection resistor, an MCU control software and a peripheral logic circuit constitute a DS differential pressure control loop of the output power MOSFET.

[0013] The high-power and adjustable-brightness endoscope cold light source control system of the present invention is implemented by the following technical solutions:

[0014] A high-power and brightness-adjustable endoscope cold light source control system is used to control the endoscope cold light source of the present invention, and includes two sets of parallel control loops, namely: a high-power LED current control loop and an output MOSFET DS differential pressure control loop.

[0015] Preferably, the high-power LED current control loop is implemented by hardware and is a linear power supply circuit, and also has an overcurrent protection circuit.

[0016] Preferably, the DS differential voltage control loop of the output MOSFET includes three cascade controller loops, namely: an outer loop differential voltage controller, a middle loop output voltage controller and an inner loop primary side current controller.

[0017] Preferably, the setting value of the differential pressure controller of the outer loop is determined by the MCU software according to the operating parameters of the output MOSFET according to formula (1):

[0018] Vsv=α·Rds·Isv (1)

[0019] Where: α is the margin factor; Rds is the maximum on-resistance of the power MOSFET transistor at Vgs = 10V; Isv is the operating current setting value of the high-power LED.

[0020] Compared with the prior art, the present invention has significant advantages and positive effects, including:

[0021] (1) The endoscope cold light source of the present invention has the characteristics of high power, adjustable brightness, and extremely small brightness fluctuation. It has two parallel control loops, high-power LED output current control and power MOSFET transistor DS voltage difference control. The high-power LED brightness is stable and the power consumption of the power MOSFET transistor is low. The output current control loop is implemented by hardware, with high speed, and has an overcurrent protection circuit, which can quickly prevent the expensive high-power LED device from overcurrent. The DS voltage difference control loop is mainly implemented by MCU software, with low cost.

[0022] (2) The DS voltage difference control loop includes three cascade controllers. Both the primary current and secondary voltage of the push-pull transformer can be effectively controlled. The primary current control of the innermost loop uses a linear low on-resistance MOSFET, which has a small current impact and a smooth current change on the secondary side of the transformer, reducing the impact of high-frequency harmonics on subsequent currents, which is beneficial to stabilizing the LED luminous intensity.

[0023] (3) The output current of the endoscope cold light source of the present invention can be adjusted from 10% to 100% in steps of 5%, with a wide adjustment range.

[0024] (4) The endoscope cold light source of the present invention can be used as a matching high-quality light source for various high-definition endoscopes such as 1080P and 4K. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The overall structure of an endoscope cold light source in one embodiment of the present invention;

[0026] Figure 2 The energy flow and control signal flow of the cold light source of the endoscope in one embodiment of the present invention;

[0027] Figure 3 This is a structural diagram of a control system for an endoscope cold light source in one embodiment of the present invention;

[0028] Figure 4 This is a structural diagram of a high-power LED current control circuit of an endoscope cold light source in one embodiment of the present invention. DETAILED DESCRIPTION

[0029] The specific implementation of the present invention is described below in conjunction with the accompanying drawings, but the implementation of the present invention is not limited thereto.

[0030] The present invention provides a matching LED cold light source for an endoscope, a high-power and adjustable brightness endoscope cold light source, including: a 48V switching power supply, positive and negative 12V and 5V switching power supplies, a cold light source main circuit, a cold light source control circuit, a human-machine interface circuit and a remote control interface circuit, wherein:

[0031] The 48V switching power supply provides power for the main circuit of the cold light source (DC / DC main circuit), and the positive and negative 12V and 5V switching power supplies provide power for the remaining other circuits; the 48V DC of the main circuit of the cold light source is converted into low-voltage high-frequency AC through a push-pull transformer, and then a DC voltage is obtained through synchronous rectification and LC filtering, and the DC voltage is then driven by a linear power MOSFET tube to drive the high-power LED to emit light. The human-machine interface circuit and the remote control interface circuit are used to set the LED current output percentage locally and remotely respectively. The set value is output by the 12-bit DAC inside the MCU. The output current can be adjusted from 10% to 100% in 5% steps, with a wide adjustment range.

[0032] The endoscope cold light source of the present invention has two sets of parallel control loops, a high-power LED current control loop and a DS differential pressure control loop of an output MOSFET. The high-power LED current control loop is implemented by hardware, is a linear power supply circuit, has a high bandwidth, ensures the stability of the high-power LED current output, and has an overcurrent protection circuit to ensure the safe operation of the high-power LED; the DS differential pressure control loop is a switching power supply circuit, which is mainly implemented by MCU software and necessary hardware drive circuits, has low cost, ensures the stability of the D-pole and S-pole voltage differences of the MOSFET, and the two sets of parallel control loops ensure that the output current of the cold light source is constant, the power MOSFET transistor itself generates less heat and has high efficiency. The DS differential pressure control loop includes an outer differential pressure control loop, a middle output voltage control loop and an inner primary current control loop. The DC / DC main transformer works in a push-pull topology mode, and the primary side of the push-pull transformer adopts a linear MOSFET drive to reduce current impact; the secondary side of the push-pull transformer adopts self-driven synchronous rectification to further reduce losses and improve efficiency.

[0033] Specifically, see Figure 1 A high-power and adjustable brightness endoscope cold light source includes: a 48V output switching power supply M10, a positive and negative 12V and 5V output switching power supply M11, a cold light source main circuit M12, a cold light source control circuit M13, a human-machine interface circuit M14 and a remote control interface circuit M15. Among them:

[0034] The 48V output switching power supply M10 converts 220V AC mains power into 48V DC power to supply power to the main circuit of the cold light source.

[0035] The positive and negative 12V and 5V output switching power supply M11 converts the 220V AC mains power into positive and negative 12V and 5V power supplies to power all other circuits except the main circuit of the cold light source.

[0036] The cold light source main circuit M12 includes a push-pull transformer, a self-driven synchronous rectification circuit, an LC filter circuit, a high-power LED device, a linear power MOSFET device and a resistive current sensor. The high-power LED device is CFT-90-W, and the linear power MOSFET is IPB017N10N5LF.

[0037] The cold light source control circuit M13 includes: MCU (Micro Control Unit) detection and control software, current and voltage detection circuits, operational amplifiers and comparators;

[0038] The human-machine interface circuit M14 includes buttons and an OLED display screen. The buttons are connected to the I / O port of the MCU. The display screen is OLED-128O064D-GPP3N, which is connected to the MCU via an SPI interface.

[0039] The remote control interface circuit M15 converts the MCU on-chip peripheral UART into an RS422 interface through the MAX490 chip and connects to the endoscope host.

[0040] In a preferred embodiment, see Figure 2 The main circuit of the cold light source includes: a 48V switching power supply M20, a push-pull high-frequency transformer M21, a primary-side driving circuit M22, a secondary-side self-driven synchronous rectification and filtering circuit M23, a high-power LED and its light-emitting driving circuit M24; the control circuit of the cold light source includes: an output current detection circuit M25, an MCU control software and a peripheral logic circuit M26, an output current control circuit M27, an output voltage detection and DS differential pressure detection circuit M28 and a primary-side current detection resistor M29. Figure 2 The MCU control software and the peripheral logic circuit M26 in the output current control circuit M27 provide the LED output current setting value. The output current detection circuit M25, the output current control circuit M27 and the high-power LED and its light-emitting drive circuit M24 form a high-power LED current control loop. The structure of the high-power LED current control loop is shown in FIG. Figure 3 , see the specific hardware circuit implementation Figure 4 .

[0041] Figure 2 The push-pull high-frequency transformer M21, the primary-side driving circuit M22, the secondary-side self-driven synchronous rectification and filtering circuit M23, the output voltage detection and DS differential pressure detection circuit M28, the primary-side current detection resistor M29, the MCU control software and the peripheral logic circuit M26 constitute the differential pressure control loop (DS differential pressure control loop) of the D-pole and S-pole of the output power MOSFET. The structure of the DS differential pressure control loop is shown in Figure 3The primary side driving circuit M22 is driven by two linear MOSFET power tubes IPB110N20N3LF to drive a push-pull high-frequency transformer. The use of linear MOSFET can better control the current rise and fall speed of the primary side of the transformer, reduce the current impact on the secondary side of the transformer, and is conducive to the stability of the subsequent high-power LED working voltage and current. At the same time, the power MOSFET has a very small resistance when it is fully turned on, and does not increase power consumption. The secondary side self-driven synchronous rectification and filtering circuit M23 uses a power MOSFET transistor BSZ018N04LS6 with an on-resistance of 1.8 milliohms to replace the usual rectifier diode, which can reduce the voltage drop during rectification and improve efficiency. Output voltage detection and DS differential voltage detection circuit M28 The output voltage detection is realized by resistor voltage division and RC filter, and then connected to the MCU's on-chip ADC (Analog to Digital Converter); The DS differential voltage detection circuit uses the differential instrumentation amplifier INA826 to amplify and filter the differential voltage between the D and S poles of the MOSFET, and then connects to the MCU's on-chip ADC; The primary side current detection resistor M29 uses two 10 milliohm 5 watt current detection resistors in parallel, which are connected to the MCU's ADC after amplification. For details, see Figure 4 The MCU control software and peripheral logic circuit M26 implement voltage and current detection and conversion, run the control algorithm, and then output the set value or control quantity through its on-chip DAC (Digital to Analog Converter).

[0042] See also Figure 3 The whole control system of the high-power adjustable brightness endoscope cold light source includes two parallel control loops, a high-power LED current control loop and an output MOSFET DS differential pressure control loop.

[0043] The high-power LED current control loop is implemented by hardware and has a fast response speed. For detailed description, see Figure 4 , the set value is set by the user through the human-machine interface, and then the MCU software outputs the set value through its DAC. The luminous intensity of the LED is positively correlated with its operating current. According to the device parameters, the user can adjust the range to (0%, 10%~100%), 0% is to turn off the LED light, 10% is the minimum setting value, and 100% is the maximum setting value. The minimum setting value is 10% because too little light is not needed in practice. The adjustment step from 10% to 100% is 5%. For the CFT-90-W high-power LED, the relationship between its relative luminous intensity and current is shown in Table 1. The MCU converts the relative light intensity set by the user into the LED operating current setting value according to the linear interpolation method.

[0044] Table 1 Relationship between relative light intensity and operating current of CFT-90-W

[0045] Relative light intensity (%) 10 35 60 80 94 100 Working current(A) 1.5 5 10 15 20 22.5

[0046] Figure 4 The high-power LED current control loop uses a 10M bandwidth amplifier OPA4197 with 4 operational amplifiers. U1D is used to measure the current of the high-power LED CFT-90-W. Resistors R01 and R02 are connected in parallel as current sensing resistors. After being amplified 17 times by the same-phase amplifier, one path is sent to the ADC of the MCU for other parameter calculation and display purposes. The other path is connected to resistor R23 as the input of the amplifier U1B as the controlled quantity. U1A, as a voltage follower, amplifies the current setting value output by the DAC of the MCU. U1B is a differential amplifier. It calculates the error between the current setting value and the measured value and amplifies it 10 times before sending it to U1C for PI operation. The output of U1C drives the high-power MOSFET transistor Q01IPB017N10N5LF through resistor R03. Since the current of the high-power LED changes with factors such as the external voltage Upv and temperature, a larger proportional gain can be used to achieve rapid stabilization of the LED current and overcome the fluctuation of Upv; the integral link realizes compensation for slow-changing disturbances such as temperature.

[0047] The DS differential pressure control loop of the output MOSFET includes three cascade controller loops, namely: the differential pressure controller of the outer loop, the output voltage controller of the middle loop and the primary current controller of the inner loop. The output value of the previous controller is the set value of the next controller. The set value of the differential pressure controller of the outer loop is determined by the MCU software according to the working parameters of the output MOSFET according to formula (1).

[0048] Vsv=α·Rds·Isv (1)

[0049] Where α is the margin coefficient, which can be taken as 1.3; Rds is the maximum on-resistance of the power MOSFET transistor at Vgs = 10V, which is 17mΩ (milliohm) for IPB017N10N5LF; Isv is the operating current setting value of the high-power LED, which is calculated by the MCU according to the light intensity setting value set by the user through Table 1 and linear interpolation.

[0050] Figure 3 The measured differential pressure value M39 of the DS terminal of the output MOSFET is amplified by the differential amplifier and then sent to the ADC of the MCU. The MCU obtains the differential pressure value V of the DS terminal through the ADC. ds The differential pressure controller M33 calculates the difference between the differential pressure setting value at the DS end and the differential pressure measurement value, and then obtains U through the non-zero initial PI control algorithm. SV The specific algorithm is shown in formula (2). The use of non-zero initial value reduces the transition time to reach the steady state.

[0051]

[0052] Where U SV0 is the initial constant, take 3940mV; K P1 is the proportionality coefficient, take 0.618; K I1 is the integral coefficient, take 0.06; V ds is the measured value of the differential voltage at the DS terminal of the output MOSFET; V SV It is the differential pressure setting value at DS end.

[0053] Figure 3 The output voltage controller M34 sets its set value U SV And the voltage U on the filter capacitor PV After calculating the difference, the current setting value of the next level of control is obtained, and its algorithm is shown in formula (3).

[0054]

[0055] Where I SV0 is the initial constant, take 150mA; K P2 is the proportionality coefficient, take 8; K I2 is the integral coefficient, take 0.8.

[0056] The primary side current controller M35 includes an MCU timer on-chip peripheral (for outputting PWM square waves), a comparator LM331, and a power MOSFET driver 2EDN7523F. The 100kHz frequency PWM signal output of the MCU is connected to the two inputs of 2EDN7523F. The output of 2EDN7523F drives the linear power MOSFET transistor IPB110N20N3LF, and IPB110N20N3LF drives the push-pull transformer. The primary side current setting value of the push-pull transformer is Isv1, and the primary side current measurement value is Ipv1; the output of LM331 is connected to the enable terminal of 2EDN7523F. Only when Isv1 is greater than Ipv1, the power MOSFET driver 2EDN7523F can output a PWM drive signal, thereby adjusting the duty cycle of the PWM wave according to the set current value. In order to ensure the integrity of the power MOSFET switching process, the comparator is set to a 20% hysteresis, and the Ipv1 measurement circuit uses a RC low-pass filter with a filter time constant of 50 nanoseconds. The use of linear power MOSFET reduces the current impact on the primary and secondary sides of the transformer during the switching process, and also reduces the interference in the primary side current measurement process.

[0057] Figure 3In addition to the two parallel control loops mentioned above, there is also an overcurrent protection circuit M3A module, including a high-speed comparator LMV7219 and a trigger 74LVC1G74. When working normally and the LED has no overcurrent, the trigger outputs a low level, and the electronic switch EW1 is in a disconnected state, which does not affect the normal operation of the LED current control loop; when the LED current is greater than its overcurrent setting value of 27 amperes, which is set by the reference power supply REF3030 through a resistor divider, the comparator flips to make the trigger output a high level and latch the state. At this time, the electronic switch EW1 is closed, shutting off the current flowing through the LED, protecting the expensive high-power LED. At the same time, the overcurrent protection circuit M3A notifies the MCU of the overcurrent state. After 10 seconds, the MCU tries to reset the overcurrent protection circuit again. If overcurrent occurs again, it reports a fault and can only be put into operation again after repair and restart.

[0058] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A high-power and adjustable brightness endoscope cold light source, characterized in that: The endoscope cold light source includes two sets of parallel control loops: a high-power LED current control loop and a MOSFET DS differential voltage control loop; wherein: the high-power LED current control loop is a linear power supply circuit; the DS differential voltage control loop is a switching power supply circuit; the two sets of parallel control loops ensure that the output current of the endoscope cold light source is constant, the MOSFET itself generates less heat and has high efficiency; The endoscope cold light source includes: 48V switching power supply, positive and negative 12V and 5V switching power supply, cold light source main circuit, cold light source control circuit, human-machine interface circuit and remote control interface circuit, among which: 48V switching power supply provides power for the cold light source main circuit; positive and negative 12V and 5V switching power supply provide power for other circuits other than the cold light source main circuit; 48V DC of the cold light source main circuit is converted into low-voltage high-frequency AC through a push-pull transformer, and then a DC voltage is obtained through synchronous rectification and LC filtering, and the DC voltage drives a high-power LED to emit light through a MOSFET; the human-machine interface circuit and the remote control interface circuit are used to set the LED current output percentage locally and remotely respectively; The main circuit of the cold light source includes: a push-pull high-frequency transformer, a primary-side drive circuit, a secondary-side self-driven synchronous rectification and filtering circuit, a high-power LED and its light-emitting drive circuit; the cold light source control circuit includes: an output current detection circuit, an MCU control software and a peripheral logic circuit, an output current control circuit, an output voltage detection and DS differential pressure detection circuit and a primary-side current detection resistor; wherein: The output current detection circuit, the output current control circuit, the high-power LED and its light-emitting drive circuit constitute a high-power LED current control loop; The push-pull high-frequency transformer, primary-side driving circuit, secondary-side self-driven synchronous rectification and filtering circuit, output voltage detection and DS differential voltage detection circuit, primary-side current detection resistor, MCU control software and peripheral logic circuit constitute the DS differential voltage control loop of MOSFET.

2. The endoscope cold light source according to claim 1, characterized in that: The output current of the endoscope cold light source can be adjusted from 10% to 100% in 5% steps.

3. The endoscope cold light source according to claim 1, characterized in that: The primary side driving circuit uses MOSFET to drive the push-pull high-frequency transformer; the secondary side self-driven synchronous rectification and filtering circuit uses MOSFET with an on-resistance of 1.8 milliohms instead of the rectifier diode.

4. The endoscope cold light source according to claim 3, characterized in that: The MCU control software and peripheral logic circuit provide the LED output current setting value to the output current control circuit.

5. A high-power and adjustable brightness endoscope cold light source control system, characterized in that: Used to control the endoscope cold light source according to any one of claims 1 to 4, comprising two sets of parallel control loops, namely: a high-power LED current control loop and a MOSFET DS differential pressure control loop.

6. The endoscope cold light source control system according to claim 5, characterized in that: The high-power LED current control loop is implemented by hardware and is a linear power supply circuit, and also has an overcurrent protection circuit.

7. The endoscope cold light source control system according to claim 5, characterized in that: The DS differential voltage control loop of MOSFET includes three cascade controller loops, namely: the differential voltage controller of the outer loop, the output voltage controller of the middle loop and the primary side current controller of the inner loop.

8. The endoscope cold light source control system according to claim 7, characterized in that: The setting value of the differential pressure controller of the outer loop is determined by the MCU software according to the working parameters of the MOSFET according to formula (1): （1） in: α is the margin factor; Rds is the maximum on-resistance of MOSFET at Vgs=10V; ISV Set the operating current value for high-power LEDs.

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