Power supply circuit for medical display

Abstract

The utility model relates to the technical field of display circuits, and discloses a power supply circuit for a medical display, which aims to solve the technical problem that the image display quality is influenced by noise existing in a conventional power supply system, and comprises a protective tube, a first common mode inductor and a second common mode inductor which are sequentially connected in series in an alternating current input line, the TVS tube, the first X capacitor and the second X capacitor are connected in parallel in an alternating current input line, and a first series capacitor circuit and a first series resistor circuit are further connected in parallel between the rear stage of the first common mode inductor and the front stage of the second common mode inductor. The overvoltage protection and anti-interference performance is improved by combining a TVS tube, a first X capacitor and a second X capacitor; the first series capacitance circuit and the first series resistance circuit further attenuate residual interference and improve circuit stability and anti-noise capability, so that the power supply quality of the medical display is remarkably improved, and the image display definition and the equipment reliability are guaranteed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of display circuit, and particularly relates to a power supply circuit for medical display. BACKGROUND

[0002] With the continuous progress of medical technology and the increasing demand for medical diagnosis, medical display plays an increasingly important role in medical imaging diagnosis, surgical monitoring, ward management and other aspects. Medical display needs to provide high-resolution, high-contrast and high-brightness image display effect, so that doctors can make accurate diagnosis and operation. However, since the requirements of medical equipment for power supply are quite strict, the power supply system of medical display not only needs to stably and reliably provide the required power, but also must meet the high standard requirements of medical equipment for electromagnetic compatibility (EMC) and power factor.

[0003] The power supply system of medical display is usually composed of alternating current input power supply, filter circuit, rectifier circuit, power factor correction (PFC) circuit and other parts. Since medical display may work in high-precision and high-stability environment for a long time, the power supply system must have high anti-interference ability, low noise characteristics and precise power control. In addition, in order to ensure the safety of medical equipment and comply with relevant electrical standards, the power supply system also needs to have overvoltage and overcurrent protection functions, and can efficiently convert electric energy to reduce energy consumption.

[0004] The traditional power supply system of medical display has too much high-frequency noise, which affects the image quality of the display and reduces the stability and reliability of the display, especially in medical environment, such noise may have a negative impact on diagnosis and monitoring. CONTENT OF THE UTILITY MODEL

[0005] The utility model aims at providing a power supply circuit for medical display, to solve the technical problem that the existing power supply system has noise affecting image display quality.

[0006] In order to achieve the above-mentioned purpose, the specific technical scheme of the power supply circuit for medical display of the utility model is as follows:

[0007] The utility model relates to a power supply circuit for medical display, including AC input line, rectifier circuit and power factor correction circuit, AC input line includes fuse tube, first common mode inductance and second common mode inductance in AC input line for inhibiting common mode electromagnetic interference in input power supply in series, TVS tube, first X capacitor and second X capacitor are connected in parallel between AC input line, TVS tube, first X capacitor are located in the former stage of first common mode inductance, and second X capacitor is located in the latter stage of first common mode inductance, first common mode inductance latter stage and second common mode inductance former stage still have first series capacitor circuit and first series resistance circuit in parallel, wherein, first series capacitor circuit includes two first Y capacitor and second Y capacitor in series, and first series resistance circuit includes two first resistance and second resistance in series, and first resistance and second resistance are connected with third resistance and fourth resistance in parallel respectively.

[0008] The power supply circuit for medical display of the utility model effectively inhibits common mode electromagnetic interference in input power supply by connecting first common mode inductance and second common mode inductance in series in AC input line, ensures the stability of input signal, by connecting TVS tube, first X capacitor and second X capacitor in parallel, improves the overvoltage protection ability of circuit, and enhances the anti-interference performance, wherein TVS tube is located in the former stage of first common mode inductance, can quickly respond to input surge voltage, and protects the latter stage circuit from being damaged, the reasonable arrangement of first X capacitor and second X capacitor further optimizes the filtering effect of circuit, reduces the interference of high-frequency noise to system, furthermore, by connecting first series capacitor circuit and first series resistance circuit in parallel between first common mode inductance latter stage and second common mode inductance former stage, the first Y capacitor and second Y capacitor in first series capacitor circuit share the energy of electromagnetic noise, and the voltage division and damping characteristics of first series resistance circuit effectively attenuate residual interference, further improve the stability and anti-noise ability of circuit, this design can significantly improve the power quality of medical display, avoid the problem of image display quality decline caused by power noise influence, thereby meeting the requirement of high-precision medical equipment on display definition and reliability.

[0009] By the series connection of four resistors, the voltage is shared by the first and second resistors in series, avoiding a single resistor from bearing too high voltage, and improving the stability and safety of circuit operation, the third and fourth resistors in parallel share part of the power, effectively reducing the heat consumption of a single resistor and reducing the risk of damage caused by overheating, and the mixed connection structure has better damping characteristics for high-frequency signals, further attenuating electromagnetic interference and improving the anti-noise ability and stability of circuit

[0010] Further, the latter stage of the second common mode inductance is connected to a rectifier stack for converting alternating current into direct current and outputting a first direct current, and the positive output end of the rectifier stack sequentially passes through a first diode and a thermistor to supply a second direct current to the next stage circuit.

[0011] Further, the power factor correction circuit comprises a PFC controller and an NMOS tube, and is further provided with an induction circuit for transmitting an induced voltage to the PFC controller, comprising an inductor, a first induction coil and a second diode connected in series, a second end of the inductor being connected with an anode of the first diode, a cathode of the second diode being connected with a cathode of the first diode, the first induction coil, a detection end of the PFC controller being connected with ground through a third resistor and a second induction coil in sequence, the first induction coil and the second induction coil being coupled.

[0012] Further, a drive pulse signal of the PFC controller is connected with a gate of the NMOS tube through a fifth resistor and a sixth resistor in sequence, the sixth resistor being connected in parallel with a third diode, an anode of the third diode being connected with the gate of the NMOS tube, a drain of the NMOS tube being connected with an anode of the second diode, a source of the NMOS tube being connected with ground through a current detection resistor, a control loop comparator input end of the PFC controller being connected with the source of the NMOS tube through a seventh resistor and being connected with ground through a first capacitor.

[0013] The power supply circuit for the medical display has the following advantages:

[0014] In the AC input circuit, the first common mode inductor and the second common mode inductor are connected in series, and the TVS tube, the first X capacitor and the second X capacitor are configured, so that the common mode electromagnetic interference is effectively inhibited, the overvoltage protection capability and the high-frequency noise resistance performance are enhanced, and the stability of the input signal is ensured; the arrangement of the first series capacitor circuit and the first series resistor circuit further improves the anti-interference effect by sharing and attenuating electromagnetic noise. The first diode and the thermistor are connected after the rectifier stack, the conversion efficiency from AC to DC is optimized, stable second DC power is provided, and the subsequent load is adapted. The power factor correction circuit adopts the PFC controller and the NMOS tube, through the design of the induction circuit and the coupled induction coil, efficient voltage detection and transmission are realized, and through precise control of the drive pulse signal and the current loop, the power factor and the energy utilization rate are improved, the stable output characteristics and the fast dynamic response capability are ensured; in addition, the drive circuit of the PFC controller is combined with the protection design of multiple resistors, capacitors and third diodes, the system anti-interference capability is enhanced, and the damage of the NMOS tube caused by overload or reverse current is prevented. Through the multi-layer protection and optimization design, the technical problems of noise interference and insufficient power factor in the existing power supply system are solved from input to output, the image distortion or quality decline of the medical display caused by the power quality problem is effectively avoided, and the strict requirements of high-precision medical equipment on stability, high efficiency and image display clarity are fully met. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 The EMC circuit structure diagram in the AC power input circuit of the utility model is shown.

[0016] Figure 2 The power factor correction circuit structure diagram is provided. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical scheme and advantages of the utility model more clearly, the following will be further detailed in combination with the drawings and examples.The specific examples described here are only used to explain the utility model, and are not used to limit the utility model.

[0018] The utility model provides a power supply circuit for medical display,

[0019] Refer to Figure 1 The AC input circuit includes a first AC circuit and a second AC circuit, an EMC circuit is arranged in the AC input circuit, a first common mode inductor L3 and a second common mode inductor L6 are arranged in the EMC circuit, a TVS tube and an X capacitor C1 are arranged in parallel between the first AC circuit and the second AC circuit in the front stage of the first common mode inductor, and a safety tube F1 is connected in series in the second AC circuit; an X capacitor C2, a first series capacitor circuit and a first series resistor circuit are arranged in parallel between the first AC circuit and the second AC circuit in the AC input circuit between the first common mode inductor L3 and the second common mode inductor L6, the first series capacitor circuit includes two series-connected Y capacitors C3 and C4, the first series resistor circuit includes two series-connected resistors R49 and R50, and the resistors R49 and R50 are respectively connected in parallel with resistors R9 and R48.

[0020] The rear stage of the second common mode inductor L6 is connected with a rectifier stack U3, which is used for rectifying AC into DC, and a DC 1 is output through the positive output end of the rectifier stack U3.

[0021] Working principle: in the EMC circuit of the AC input circuit, in order to effectively suppress electromagnetic interference and protect the subsequent circuit. The input current first passes through the first common mode inductor L3, and the main function of the inductor is to suppress common mode interference signals. In order to further reduce noise, the TVS tube D2 and the X capacitor C1 are connected in parallel between the first AC circuit and the second AC circuit. The TVS tube D2 is used for protecting the circuit from the impact of instantaneous overvoltage, and the X capacitor C1 is used for filtering high-frequency noise to ensure the quality of the power supply.

[0022] The second common-mode inductor L6 continues to suppress common-mode noise in the current. To further enhance the filtering effect, a plurality of filtering elements are added to the AC input line between the first common-mode inductor L3 and the second common-mode inductor L6, including the parallel X capacitor C2, and the series first series capacitor circuit and the first series resistance circuit. Among them, the first series capacitor circuit is composed of Y capacitor C3 and Y capacitor C4, mainly used to filter out differential mode noise and prevent the circuit from being disturbed by high frequency interference. The first series resistance circuit is composed of resistance R49 and resistance R50 in series, which are connected in parallel with resistance R9 and resistance R48, which helps to further suppress high frequency signals and stray noise in the current. Finally, the rear end of the second common-mode inductor L6 converts alternating current into direct current through the rectifier stack U3, and outputs direct current DC1 through the positive output end of the rectifier stack for subsequent circuit use.

[0023] Since Y capacitor is mainly used to suppress common-mode interference, the series design superimposes the voltage resistance of each capacitor, improving the overall voltage resistance level and ensuring the safe operation of the circuit in a high-voltage environment.

[0024] Referring to Figure 2 , the positive output end of the rectifier stack U3 supplies the second direct current VBUS to the next stage circuit through the diode D14 and the thermistor RT1 in turn. An induction circuit is provided, including inductance L4, induction coil L1B and diode D3 connected in series, the second end of inductance L4 is connected with the anode of diode D14, and the cathode of diode D3 is connected with the cathode of diode D14.

[0025] The active power factor correction circuit includes PFC controller Q1 and NMOS tube Q9, the first end of PFC controller Q1 is a power supply end, which is powered by an auxiliary power supply;

[0026] The second end of PFC controller Q1 is the output end of error amplifier, the third end of PFC controller Q1 is the inverting input end of error amplifier, the inverting input end of error amplifier is connected with the output end of error amplifier in turn through resistance R67, resistance R53, capacitor C41, and capacitor C42 is connected in parallel across resistance R53 and capacitor C41; the inverting input end of error amplifier is also connected with the second direct current VBUS in turn through resistance R70, resistance R71, resistance R72, resistance R73;

[0027] The fourth end of PFC controller Q1 is the driving pulse output end, which is connected with the gate of NMOS tube Q9 in turn through resistance R68 and resistance R77, diode D15 is connected in parallel across resistance R77, the anode of diode D15 is connected with the gate of NMOS tube Q9, the source of NMOS tube Q9 is connected to ground through current detection resistance R80, and the drain of NMOS tube Q9 is connected with the anode of diode D3.

[0028] The 5th end of the PFC controller Q1 is an input end of a control loop comparator, connected with the source of the NMOS Q9 through a resistor R79 and grounded through a capacitor C34.

[0029] The 6th end of the PFC controller Q1 is an input end of a multiplier, connected with the 1st end of the inductor L4 through a resistor R74, a resistor R75 and a resistor R76 in sequence;

[0030] The 7th end of the PFC controller Q1 is a detection end, connected with an inductive coil L1A through a resistor R51 in sequence, the inductive coil L1A and an inductive coil L1B are wound on the same core, the inductive signal in the inductive coil L1B is coupled into the inductive coil L1A, and the zero current detection end is detected.

[0031] The 8th end of the PFC controller Q1 is a ground end, grounded through a capacitor C34.

[0032] Working principle: the rectifier stack U3 converts the alternating power supply into a direct current power supply, and outputs a second direct current VBUS to the next stage circuit through a diode D14 and a thermistor RT1. The inductive circuit is composed of an inductor L4, an inductive coil L1B and a diode D3. The second end of the inductor L4 is connected with the anode of the diode D14, and is connected with the inductive coil L1B and the diode D3 in series.

[0033] The PFC controller Q1 outputs a driving pulse signal through the 4th end, and is connected with the gate of the NMOS Q9 through a resistor R68 and a resistor R77, so as to adjust the switching state of the NMOS Q9. The cooperation of the diode D15 and the resistor R77 ensures the stability of the gate signal. The source of the NMOS Q9 is grounded through a current detection resistor R80 and fed back to the PFC controller Q1 through a resistor R79, so as to adjust the current and perform power factor correction.

[0034] The zero current detection end is connected with the inductive coil L1A and the resistor R51, realizes the detection of the zero crossing point of the current, and provides an accurate reference for the power factor correction. The whole circuit relies on the accurate control of the PFC controller Q1 to keep the synchronization between the input current and the voltage, ensures that the current waveform is consistent with the voltage waveform as much as possible, and thus realizes the optimization of the power factor.

[0035] The power supply circuit for the medical display has the following advantages:

[0036] The EMC circuit improves the electromagnetic compatibility of the power supply circuit, which can effectively suppress various electromagnetic interferences and power supply noises. By using the combination of common mode inductance, X capacitor, Y capacitor and resistance, the circuit can realize the filtering of noise in different frequency bands, ensure the purity of the power supply signal, and avoid the influence of high-frequency noise on the subsequent equipment. The use of TVS tube and capacitor also enhances the protection ability of the circuit to transient voltage, improves the anti-interference ability of the electrical system, thereby reducing the risk of circuit damage.

[0037] Further, the safety fuse F1 is used to protect the circuit from overcurrent damage, ensuring the safety of the circuit. The function of the rectifier stack U3 is to convert the input AC power supply into stable DC power, ensuring the stable operation of the circuit. Through the above design, the EMC circuit can effectively improve the stability and reliability of the electrical equipment, prolong its service life, and ensure compliance with relevant electromagnetic compatibility standards, which helps to avoid equipment failure or performance degradation caused by electromagnetic interference.

[0038] The circuit effectively improves the power factor of the power supply through active power factor correction, reducing the waste of electrical energy. The coordinated work of PFC controller Q1 and NMOS tube Q9 not only realizes efficient power factor correction, but also ensures the waveform alignment of current and voltage, reduces the impact on the power grid, and helps to reduce the generation of harmonics. Through the cooperation of zero-current detection and inductive circuit, the circuit can accurately capture the current signal change, optimize the current waveform, and further improve the adjustment accuracy of the power factor.

[0039] In addition, the use of diode D14, diode D3, diode D15 and other elements in the circuit effectively protects the circuit from overvoltage and reverse current interference, ensuring the safety and stability of the system. Through the cooperation of thermistor RT1 and current detection resistor R80, the circuit also has overcurrent protection function to prevent circuit damage caused by excessive current. Overall, this circuit design improves the efficiency and reliability of the power supply system, reducing electromagnetic interference to the environment.

[0040] The above only describes the preferred embodiments of the present application, and does not limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A power supply circuit for a medical display comprising an AC input line, a rectifier circuit and a power factor correction circuit, characterized in that, The AC input line includes: The fuse (F1), the first common mode inductor (L3) and the second common mode inductor (L6) are connected in series in the AC input line, for suppressing common mode electromagnetic interference in the input power supply; The TVS tube (D2), the first X capacitor (C1) and the second X capacitor (C2) are connected in parallel between the AC input lines, the TVS tube (D2) and the first X capacitor (C1) are located in the front stage of the first common mode inductor (L3), and the second X capacitor (C2) is located in the rear stage of the first common mode inductor (L3); The first series capacitor circuit and the first series resistance circuit are also connected in parallel between the rear stage of the first common mode inductor (L3) and the front stage of the second common mode inductor (L6), wherein the first series capacitor circuit includes two series-connected first Y capacitor (C3) and second Y capacitor (C12), and the first series resistance circuit includes two series-connected first resistance (R49) and second resistance (R50), and the first resistance (R49) and the second resistance (R50) are respectively connected in parallel with the third resistance (R9) and the fourth resistance (R48).

2. The power supply circuit for a medical display according to claim 1, characterized by, The rear stage of the second common mode inductor (L6) is connected to the rectifier stack (U3) for converting AC to DC, and outputs the first DC (DC1), and the positive output end of the rectifier stack (U3) is sequentially connected to the second DC (VBUS) for supplying power to the next stage circuit through the first diode (D14) and the thermistor (RT1).

3. The power supply circuit for a medical display according to claim 2, characterized by, The power factor correction circuit includes a PFC controller (Q1) and an NMOS tube (Q9), and an induction circuit is further provided for transmitting an induction voltage to the PFC controller (Q1), which includes an inductor (L4), a first induction coil (L1B) and a second diode (D3) connected in series, the second end of the inductor (L4) is connected to the anode of the first diode (D14), the cathode of the second diode (D3) is connected to the cathode of the first diode (D14), the first induction coil (L1B) and the second induction coil (L1A) are coupled.

4. The power supply circuit for a medical display according to claim 3, characterized by, The driving pulse signal of the PFC controller (Q1) is sequentially connected to the gate of the NMOS tube (Q9) through the fifth resistance (R68) and the sixth resistance (R77), the sixth resistance (R77) is connected in parallel with the third diode (D15), the anode of the third diode (D15) is connected to the gate of the NMOS tube (Q9), the drain of the NMOS tube (Q9) is connected to the anode of the second diode (D3), the source of the NMOS tube (Q9) is connected to the ground through the current detection resistance (R80), the control loop comparator input end of the PFC controller (Q1) is connected to the source of the NMOS tube (Q9) through the seventh resistance (R79), and is connected to the ground through the first capacitor (C34).

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