Circuit for automatically identifying and protecting open-circuit fault of electronic ballast

Abstract

The invention relates to the field of electronic ballasts, and provides a circuit for automatically identifying and protecting an open-circuit fault of an electronic ballast, which comprises a single chip microcomputer U2, a signal processing unit, a driving unit and an open-circuit detection unit, and is characterized in that an input end of the signal processing unit is connected with a signal output pin of the single chip microcomputer U2; the input end of the driving unit is connected with the driving signal output end of the signal processing unit, the input end of the open circuit detection unit is connected with the voltage output end of the driving unit, and the output end of the open circuit detection unit is connected with the detection signal input end of the single chip microcomputer U2. By means of the technical scheme, the problems that in the prior art, response is delayed, real-time detection capacity is lacked and equipment is prone to being damaged in open-circuit fault response measures are solved.

Description

Technical Field

[0001] The invention relates to the field of electronic ballasts, and in particular to a circuit for automatically identifying open-circuit faults of electronic ballasts and providing protection. Background Art

[0002] In the application scenarios of ultraviolet germicidal lamps, electronic ballasts play a vital role. However, they are usually faced with many factors that lead to open circuits. On the one hand, with the increase of usage time, ultraviolet lamps will inevitably age, such as the filament inside the lamp gradually melting, the phosphor layer falling off, gas leakage, etc. These situations will cause the conductivity of the lamp to decrease until the circuit is disconnected. On the other hand, line faults are also a common cause of open circuits. For example, if the wire connecting the lamp and the ballast is bent, stretched, oxidized, etc. for a long time, a short circuit may occur; or if the solder joints in the circuit are loose or desoldering, the current will not be able to pass through the ultraviolet lamp normally, thereby affecting the normal operation of the electronic ballast.

[0003] When facing an open circuit fault, traditional electronic ballasts usually use overcurrent protection, fuses or thermal switches to prevent circuit damage. However, these protection measures have obvious shortcomings. In terms of overcurrent protection, it is usually based on monitoring the current in the circuit, and the protection action is triggered when the current exceeds the set threshold. However, at the moment of the open circuit fault, since the current change in the circuit does not reach the overcurrent protection threshold instantly, but requires a certain amount of time to accumulate, this leads to a delayed response problem in the overcurrent protection, and the circuit cannot be cut off in time when the open circuit fault occurs, which may cause the switch components in the ballast to be damaged due to long-term exposure to abnormal current. Summary of the invention

[0004] The present invention provides a circuit for automatically identifying an open circuit fault of an electronic ballast and protecting the circuit, which solves the problems in the related art of open circuit fault response measures such as delayed response, lack of real-time detection capability and easy damage to equipment.

[0005] The technical solution of the present invention is as follows:

[0006] A circuit for automatically identifying open-circuit faults and protecting electronic ballasts comprises a single-chip microcomputer U2, a signal processing unit, a driving unit, and an open-circuit detection unit, wherein the input end of the signal processing unit is connected to the signal output pin of the single-chip microcomputer U2, the signal processing unit processes the signal output by the single-chip microcomputer U2 and transmits it to the driving unit and the open-circuit detection unit, the input end of the driving unit is connected to the driving signal output end of the signal processing unit, the driving unit outputs a driving signal according to the signal output by the signal processing unit, the input end of the open-circuit detection unit is connected to the voltage output end of the driving unit, the output end of the open-circuit detection unit is connected to the detection signal input end of the single-chip microcomputer U2, the open-circuit detection unit processes the voltage output by the driving unit and transmits it to the single-chip microcomputer U2, the single-chip microcomputer U2 determines the circuit condition through the signal output by the open-circuit detection unit and outputs a corresponding signal to the signal processing unit.

[0007] Furthermore, the signal processing unit is a gate drive chip U301, the signal output pins of the single-chip computer U2 are PB14 pin and PB15 pin, the input end of the gate drive chip U301 is HIN pin and LIN pin, the PB14 pin is connected to the LIN pin, a resistor R305 is connected in series between the PB14 pin and the LIN pin, the PB15 pin is connected to the HIN pin, a resistor R304 is connected in series between the PB15 and HIN pins, the single-chip computer U2 outputs a PWM_L signal through the PB14 pin, the PB14 pin transmits the PWM_L signal to the gate drive chip U301 through the resistor R305 and the LIN pin, the single-chip computer U2 outputs a PWM_H signal through the PB15 pin, the PB15 pin transmits the PWM_H signal to the gate drive chip U301 through the resistor R304 and the HIN pin.

[0008] Further, the driving unit includes a MOS tube Q301 and a MOS tube Q302, and the driving signal output end of the signal processing unit is a HO pin and a LO pin;

[0009] The HO pin is connected to the gate of the MOS tube Q301, R302 is connected in series between the HO pin and the gate of the MOS tube Q301, the drain of the MOS tube Q301 is connected to the power supply vdc1, the LO pin is connected to the gate of the MOS tube Q302, R306 is connected in series between the LO pin and the gate of the MOS tube Q302, the source of the MOS tube Q302 is grounded, the drain of the MOS tube Q302 is connected to the source of the MOS tube Q301, and the MOS tube Q301 and the MOS tube Q302 are alternately turned on and off under the signals of the HO pin and the LO pin of the signal processing unit.

[0010] Furthermore, the voltage generated by the driving unit reaches the input terminal VLAMP2 of the open circuit detection unit after being divided by resistors RL1, RL2 and RL3. The open circuit detection unit includes a resistor R131, a resistor R112, a diode D111, a voltage regulator ZD106 and a MOS tube Q102.

[0011] The diode D111, the resistor R131, the resistor R112, and the voltage regulator ZD106 are connected in series in sequence, the anode of the diode D111 is connected to the input terminal VLAMP2, the anode of the voltage regulator ZD106 is connected to the gate of the MOS tube Q102, the source of the MOS tube Q102 is connected to the power supply, the drain of the MOS tube Q102 is connected to the output terminal OPEN_IO of the open circuit detection unit, and the output terminal OPEN_IO is connected to the PA15 pin of the single-chip computer U2;

[0012] The voltage of the input terminal VLAMP2 reaches the gate of the MOS tube Q102 after passing through the diode D111, the resistor R131, the resistor R112, and the voltage regulator ZD106; when the circuit is open, the voltage reaching the gate of the MOS tube Q102 from the input terminal VLAMP2 is greater than the voltage threshold of the gate of the MOS tube Q102, the source and the drain of the MOS tube Q102 are turned on, the current flows to the output terminal OPEN_IO, and the PA15 pin of the single-chip computer U2 detects the current; when the ballast works normally, the voltage reaching the gate of the MOS tube Q102 from the input terminal VLAMP2 is less than the voltage threshold of the gate of the MOS tube Q102, no current flows to the output terminal OPEN_IO, and the PA15 pin of the single-chip computer U2 does not detect the current.

[0013] Furthermore, it also includes a current detection module, which includes a sampling resistor R501, a voltage amplification unit, and a voltage comparison unit;

[0014] The sampling resistor R501 is connected in series on the output circuit of the electronic ballast. The sampling resistor R501 adopts a high-precision small-resistance sampling resistor. The voltage amplifying unit is connected in parallel at both ends of the sampling resistor R501. The voltage amplifying unit collects the voltage difference between the two ends of the sampling resistor R501, amplifies the voltage difference and outputs it. The voltage comparison unit is connected in series with the voltage amplifying unit. The voltage comparison unit receives the voltage output by the voltage amplifying unit, compares the output voltage with the reference voltage and outputs the corresponding high and low levels. The output end of the voltage comparison unit is connected to the PB13 pin of the single-chip computer U2. The single-chip computer U2 determines whether the ballast is open according to the high and low levels output by the voltage comparison unit.

[0015] Further, the voltage amplification unit includes an operational amplifier OP1, a feedback resistor RF1, a resistor R502, and a resistor R503;

[0016] The non-inverting input terminal and the inverting input terminal of the operational amplifier are respectively connected to the two ends of the sampling resistor R501, the resistor R502 and the resistor R503 are respectively connected in series to the non-inverting input terminal and the inverting input terminal, the positive power supply terminal of the operational amplifier OP1 is connected to the power supply, the negative power supply terminal of the operational amplifier OP1 is grounded, the capacitor C503 is connected in series to the negative power supply terminal of the operational amplifier OP1, the output terminal of the operational amplifier OP1 is connected to the voltage comparison unit, and the two ends of the feedback resistor RF1 are respectively connected to the output terminal of the operational amplifier OP1 and the inverting input terminal of the operational amplifier OP1.

[0017] Furthermore, the voltage comparison unit includes a voltage comparator COMP1 and a reference voltage source REF1, the inverting input terminal of the voltage comparator COMP1 is connected to the output terminal of the voltage amplification unit, the non-inverting input terminal of the voltage comparator COMP1 is connected to the reference voltage source REF1, the positive power supply terminal of the voltage comparator COMP1 is connected to the power supply, the negative power supply terminal of the voltage comparator COMP1 is grounded, the positive power supply terminal and the negative power supply terminal of the voltage comparator COMP1 are respectively connected in series with capacitors C504 and C505, and the output terminal of the voltage comparator COMP1 is connected to the PB13 pin of the microcontroller U2.

[0018] Furthermore, the reference voltage source REF1 adopts a voltage regulator TL431, the anode of the voltage regulator TL431 is grounded, the cathode of the voltage regulator TL431 is connected to the power supply, the reference electrode of the voltage regulator TL431 is connected to the in-phase input terminal of the voltage comparator COMP1, and a resistor R504 is connected in series between the cathode of the voltage regulator TL431 and the reference electrode.

[0019] The working principle and beneficial effects of the present invention are:

[0020] The single-chip microcomputer U2 of the present invention serves as the core coordinator of all parties. Compared with the traditional single over-current protection, fuse or thermal switch, it no longer relies solely on simple current or temperature threshold judgment, but makes comprehensive decisions based on multi-unit feedback information, which greatly improves the accuracy and timeliness of fault judgment; the signal processing unit optimizes signal transmission to avoid interference delays and ensure rapid system response; the drive unit provides a precise voltage source for open circuit detection while ensuring the normal operation of the ballast, facilitating real-time monitoring; the open circuit detection unit monitors voltage changes in real time and quickly detects open circuit faults, overcoming the defect of delayed response of traditional measures, and notifying the single-chip microcomputer to take protective measures as soon as possible, effectively avoiding damage to the equipment due to long-term abnormal operation of open circuit faults. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0022] Figure 1 is a circuit schematic diagram of an open circuit detection unit in the present invention;

[0023] Figure 2 is a circuit schematic diagram of the signal processing unit and the driving unit in the present invention;

[0024] Figure 3 It is the circuit principle diagram of the single chip computer U2 in the present invention;

[0025] Figure 4 It is the circuit principle diagram of the current detection module in the present invention. DETAILED DESCRIPTION

[0026] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] like Figure 1 to Figure 4 As shown, this embodiment proposes a circuit for automatically identifying open circuit faults and protecting electronic ballasts, including a single-chip microcomputer U2, a signal processing unit, a driving unit, and an open circuit detection unit. The input end of the signal processing unit is connected to the signal output pin of the single-chip microcomputer U2. The signal processing unit processes the signal output by the single-chip microcomputer U2 and transmits it to the driving unit and the open circuit detection unit. The input end of the driving unit is connected to the driving signal output end of the signal processing unit. The driving unit outputs a driving signal according to the signal output by the signal processing unit. The input end of the open circuit detection unit is connected to the voltage output end of the driving unit. The output end of the open circuit detection unit is connected to the detection signal input end of the single-chip microcomputer U2. The open circuit detection unit processes the voltage output by the driving unit and transmits it to the single-chip microcomputer U2. The single-chip microcomputer U2 determines the circuit condition through the signal output by the open circuit detection unit and outputs a corresponding signal to the signal processing unit.

[0028] In this embodiment, the single-chip microcomputer U2 refers to a microcontroller (Microcontroller), which is often abbreviated as MCU (Microcontroller Unit). It is an integrated circuit chip that integrates functional components such as a central processing unit (CPU), a random access memory (RAM), a read-only memory (ROM), an input and output interface (I / O interface), a timer / counter, etc. on a single chip. It has the characteristics of small size, low power consumption, and strong control function. It is widely used in various electronic devices, such as home appliances, industrial control, automotive electronics, and intelligent instruments. The single-chip microcomputer U2 serves as the control core of the entire circuit, receives the signal from the open circuit detection unit, and accurately judges the circuit situation based on these signals. At the same time, according to the judgment result, the corresponding control signal is output to the signal processing unit to coordinate the coordinated work of each unit to realize the automatic recognition and protection function of the electronic ballast for open circuit faults. One end of the signal processing unit is connected to the signal output pin of the single-chip microcomputer U2, receives the command signal issued by the single-chip microcomputer, and performs a series of processing such as conversion, amplification, and filtering on it, and transmits the processed appropriate signal to the driving unit. The driving unit generates the driving signal required to drive the normal operation of the electronic ballast based on the signal output by the signal processing unit, drives key components such as the power switch tube, and enables the ballast to convert the input power into an electric energy form suitable for the load (such as the ultraviolet lamp), and provides a voltage output for the open circuit detection unit. The open circuit detection unit obtains the voltage output by the driving unit, and performs voltage monitoring and comparison operations based on it. The detected characteristic signal related to the open circuit fault is processed and transmitted to the single-chip microcomputer U2, providing a key basis for the single-chip microcomputer to determine whether there is an open circuit in the circuit. The open circuit detection unit can capture the open circuit fault signal in the circuit in real time and accurately, overcome the disadvantage of delayed response of traditional protection measures, and feedback the fault information to the single-chip microcomputer as soon as possible, so as to realize the rapid detection of open circuit faults.

[0029] In this embodiment, the signal processing unit is the gate drive chip U301, the signal output pins of the single-chip computer U2 are the PB14 pin and the PB15 pin, the input end of the gate drive chip U301 is the HIN pin and the LIN pin, the PB14 pin is connected to the LIN pin, and a resistor R305 is connected in series between the PB14 pin and the LIN pin; the PB15 pin is connected to the HIN pin, and a resistor R304 is connected in series between the PB15 and the HIN pins, the single-chip computer U2 outputs the PWM_L signal through the PB14 pin, and the PB14 pin transmits the PWM_L signal to the gate drive chip U301 through the resistor R305 and the LIN pin, and the single-chip computer U2 outputs the PWM_H signal through the PB15 pin, and the PB15 pin transmits the PWM_H signal to the gate drive chip U301 through the resistor R304 and the HIN pin.

[0030] In this embodiment, the gate driver chip U301 is an integrated circuit specifically used to drive the gate of a power semiconductor device (such as MOSFET, IGBT, etc.). It plays a vital role in various power conversion and control circuits such as power management, motor drive, inverter, electronic ballast, etc., ensuring that the power device can perform switching operations reliably and efficiently. The gate of the power semiconductor device requires a certain voltage and current to achieve rapid conduction and cutoff. The gate driver chip can provide a sufficiently large current so that the gate capacitor of the power device can be quickly charged and discharged, thereby achieving rapid switching conversion. For example, in an electronic ballast, the gate driver chip can convert the control signal into a signal with sufficient strength to drive power devices such as MOS tube Q301 and MOS tube Q302 to meet its fast switching requirements. The single-chip microcomputer U2 outputs a PWM_L signal through the PB14 pin and a PWM_H signal through the PB15 pin. These two PWM (pulse width modulation) signals are used to control the working state of the gate driver chip U301, thereby indirectly controlling the power output and other related parameters of the electronic ballast. The PWM signal output by its pin can accurately control the duty cycle, frequency and other parameters of the signal, so as to realize flexible adjustment of the ballast drive signal. Resistors R304 and R305 are connected in series between the PB15-HIN pin and the PB14-LIN pin as current limiting resistors. They limit the current flowing from the microcontroller pin to the input pin of the gate driver chip to prevent excessive current from damaging the input pin of the gate driver chip. The reliability of the circuit is improved and the input stage circuit of the gate driver chip is protected. Since the signal output by the microcontroller pin may cause the current to increase instantly due to various reasons (such as power supply fluctuations, signal interference, etc.), the current limiting resistor can effectively avoid this situation from causing damage to the gate driver chip, thereby extending the service life of the circuit components. The HIN and LIN pins of the gate driver chip U301 are the input pins of the gate driver chip U301, which are used to receive the PWM_H and PWM_L signals sent by the microcontroller U2. These signals will be converted into drive signals that can drive the power devices (such as MOSFET, etc.) in the ballast through the processing circuit inside the gate driver chip. The signal conversion and power amplification functions are realized. The relatively weak control signal output by the microcontroller is converted into a signal with sufficient driving capability to effectively control the power devices in the ballast, ensure that the ballast can work stably, and provide appropriate power for the lamp. At the same time, the processing mechanism inside the gate driver chip can ensure the quality of the output drive signal, such as ensuring that the rising and falling edges of the signal have appropriate slopes to reduce the generation of electromagnetic interference.

[0031] In this embodiment, the driving unit includes a MOS transistor Q301 and a MOS transistor Q302, and the driving signal output terminals of the signal processing unit are the HO pin and the LO pin. The HO pin is connected to the gate of the MOS transistor Q301, and R302 is connected in series between the HO pin and the gate of the MOS transistor Q301. The drain of the MOS transistor Q301 is connected to the power supply vdc1, the LO pin is connected to the gate of the MOS transistor Q302, and R306 is connected in series between the LO pin and the gate of the MOS transistor Q302. The source of the MOS transistor Q302 is grounded, and the drain of the MOS transistor Q302 is connected to the source of the MOS transistor Q301. The MOS transistor Q301 and the MOS transistor Q302 are alternately turned on and off under the signals of the HO pin and the LO pin of the signal processing unit.

[0032] MOS tube Q301 and MOS tube Q302 are MOSFET tube Q301 and MOSFET tube Q302. MOSFET tube mainly consists of gate (G), source (S) and drain (D). Structurally, it has an insulating layer (usually silicon dioxide) separating the gate from the conductive channel. Its working principle is based on the control of the semiconductor conductive channel by the electric field. When a suitable voltage is applied between the gate and the source, a conductive channel is formed in the semiconductor region below the insulating layer, thereby controlling the current between the drain and the source. If the gate-source voltage is lower than the threshold voltage, the conductive channel is not formed, the MOSFET is in the cut-off state, and the drain-source current is extremely small; when the gate-source voltage is higher than the threshold voltage, the conductive channel is formed, the MOSFET is turned on, and the drain-source current depends on factors such as the drain-source voltage and the channel resistance.

[0033] MOS tubes Q301 and Q302 form the upper and lower bridge arms of the half-bridge drive circuit. The half-bridge drive circuit is mainly composed of two power switch devices (such as MOS tubes Q301 and MOS tubes Q302), a capacitor (such as capacitor C303) and an inductor (such as inductor L301A), and also includes control components such as driver chips. In a typical half-bridge drive circuit, two MOSFET tubes form the upper and lower bridge arms, and an LC resonant circuit composed of an inductor and a capacitor (such as inductor L301A and capacitor C303) is connected in the middle. When the driver chip outputs a signal to turn on the MOSFET tube of the upper bridge arm (such as MOS tube Q301) and turn off the MOSFET tube of the lower bridge arm (such as MOS tube Q302), the power supply vdc1 voltage charges the inductor L301A through the MOS tube Q301, and the capacitor C303 also starts to charge. The current flows from the power supply through the MOS tube Q301, the inductor and the capacitor to supply power to the load; when the driver chip controls the MOS tube Q301 to be turned off and the MOS tube Q302 to be turned on, the inductor and the capacitor are discharged through the MOS tube Q302 to maintain the load current. Through the alternating turn-on and turn-off of the upper and lower bridge arm MOSFET tubes, a high-frequency AC voltage is generated on the load, realizing the function of converting the DC power supply into a high-frequency AC power supply. The MOS tubes Q301 and Q302 are alternately turned on and off under the control of the drive signal output by the signal processing unit (the HO pin and the LO pin of the gate drive chip U301). Resistors R302 and R306 are connected in series between the HO pin-Q301 gate and the LO pin-Q302 gate, respectively, to limit current and suppress oscillation. The current flowing from the output pin of the signal processing unit to the gate of the MOS tube is limited to prevent excessive current from damaging the gate of the MOS tube. At the same time, due to the parasitic capacitance between the gate and source of the MOS tube, oscillation may occur during the switching process. These resistors can effectively suppress this oscillation and make the switching process of the MOS tube more stable. The inductor L301A and the capacitor C303 together form an LC resonant circuit, which is used to convert the DC voltage into a high-frequency AC voltage and play a role in filtering and energy storage. In the process of alternating conduction and cutoff of the MOS tube Q301 and the MOS tube Q302, the inductor L301A stores and releases energy, and the inductor L301A and the capacitor C303 jointly maintain the stability of the output voltage, making the output voltage smoother and reducing ripple.

[0034] In this embodiment, the voltage generated by the driving unit reaches the input terminal VLAMP2 of the open circuit detection unit after being divided by the resistors RL1, RL2, and RL3. The open circuit detection unit includes a resistor R131, a resistor R112, a diode D111, a voltage regulator ZD106, and a MOS transistor Q102. The diode D111, the resistor R131, the resistor R112, and the voltage regulator ZD106 are connected in series in sequence, the positive electrode of the diode D111 is connected to the input terminal VLAMP2, the positive electrode of the voltage regulator ZD106 is connected to the gate of the MOS transistor Q102, the source of the MOS transistor Q102 is connected to the power supply, the drain of the MOS transistor Q102 is connected to the output terminal OPEN_IO of the open circuit detection unit, and the output terminal OPEN_IO is connected to the PA15 pin of the single-chip computer U2. The voltage at the input terminal VLAMP2 reaches the gate of the MOS tube Q102 after passing through the diode D111, the resistor R131, the resistor R112, and the voltage regulator ZD106; when the ultraviolet lamp is open, the voltage reaching the gate of the MOS tube Q102 from the input terminal VLAMP2 is greater than the voltage threshold of the gate of the MOS tube Q102, the source and drain of the MOS tube Q102 are turned on, the current flows to the output terminal OPEN_IO, and the PA15 pin of the microcontroller U2 detects the current; when the ballast works normally, the voltage reaching the gate of the MOS tube Q102 from the input terminal VLAMP2 is less than the voltage threshold of the gate of the MOS tube Q102, no current flows to the output terminal OPEN_IO, and the PA15 pin of the microcontroller U2 does not detect the current.

[0035] Resistors R131, R112, diode D111, and voltage regulator ZD106 together form a voltage divider circuit, which divides the voltage of the input terminal VLAMP2, thereby controlling the voltage reaching the gate of the MOS tube Q102. When the ultraviolet lamp is open and working normally, the voltage of the gate of the MOS tube Q102 can reach or be lower than its threshold voltage, thereby controlling the on and off states of the MOS tube. Diode D111 plays a unidirectional conductive role, only allowing current to flow from the input terminal VLAMP2 to the resistor R131 and other subsequent circuits, while preventing reverse current. This can prevent the reverse flow of current from affecting the front-end circuit or other components in certain circumstances (such as voltage fluctuations or interference in the circuit), and protect the normal operation of the circuit. The voltage regulator ZD106 is used to stabilize the voltage of the gate of the MOS tube Q102. When the voltage of the input terminal VLAMP2 changes, the voltage regulator ZD106 can stabilize the voltage at its two ends at a specific value (voltage regulation value), thereby providing a relatively stable gate voltage reference for the MOS tube Q102. In this way, the on and off states of the MOS tube Q102 can be more accurately determined by the open circuit or normal working state of the ballast, without being affected by the voltage fluctuation at the input end. As a switching element, the MOS tube Q102 controls the on and off states between the source and the drain according to the comparison result between the gate voltage and the threshold voltage. When the ultraviolet lamp is open, the gate voltage is greater than the threshold voltage, the MOS tube Q102 is turned on, and the current flows to the output terminal OPEN_IO. The PA15 pin of the single-chip computer U2 can detect the current, thereby knowing that the ballast has an open circuit fault; when the ballast is working normally, the gate voltage is less than the threshold voltage, the MOS tube Q102 is turned off, no current flows to the output terminal OPEN_IO, and the PA15 pin of the single-chip computer U2 does not detect the current, indicating that the ballast is normal. The MOS tube Q102 realizes the signal conversion and transmission of the open circuit state. The open circuit or normal working state of the ballast is converted into a current signal that can be detected by the single-chip computer U2, providing the single-chip computer with accurate open circuit fault detection information, so that the entire circuit system can take corresponding protection measures or perform status indication and other operations in time. At the same time, the MOS tube has a higher input impedance and a faster switching speed, which can quickly respond to changes in gate voltage and improve the real-time performance of open circuit detection.

[0036] In this embodiment, the circuit for automatically identifying and protecting the electronic ballast from an open circuit fault also includes a current detection module, which is arranged on the output circuit of the ultraviolet lamp. The current detection module includes a sampling resistor R501, a voltage amplification unit, and a voltage comparison unit. The sampling resistor R501 is connected in series to the output circuit of the electronic ballast, and the sampling resistor R501 adopts a high-precision small-resistance sampling resistor. The voltage amplification unit is connected in parallel to both ends of the sampling resistor R501. The voltage amplification unit collects the voltage difference between both ends of the sampling resistor R501, amplifies the voltage difference and outputs it. The voltage comparison unit is connected in series with the voltage amplification unit. The voltage comparison unit receives the voltage output by the voltage amplification unit, and compares the output voltage with the reference voltage to output the corresponding high and low levels. The output end of the voltage comparison unit is connected to the PB13 pin of the single-chip microcomputer U2. The single-chip microcomputer U2 determines whether the ballast is open circuit according to the high and low levels output by the voltage comparison unit.

[0037] The sampling resistor R501 is connected in series to the output circuit of the electronic ballast. Using Ohm's law (U=IR), when current flows through, a voltage difference proportional to the current will be generated at both ends. Because it uses high-precision and small resistance, it can accurately reflect the current size and has little effect on the overall circuit. It will not cause excessive power loss and voltage drop due to its own excessive resistance. The sampling resistor R501 provides a simple and effective current detection method. The high precision ensures the accuracy of current detection, and the small resistance reduces the interference to the normal operation of the circuit, providing a reliable original signal source for subsequent voltage amplification and comparison. The voltage amplification unit is connected in parallel to both ends of the sampling resistor R501, collects the weak voltage difference between its two ends, and amplifies the voltage difference. Because the voltage difference generated by the sampling resistor is usually very small, direct use for subsequent processing may cause the signal to be unclear or submerged by noise. The amplification unit can amplify it to a suitable amplitude, which is convenient for the voltage comparison unit to make accurate comparisons and single-chip microcomputer detection. The voltage amplification unit improves the signal strength and signal-to-noise ratio, making the subsequent voltage comparison and the judgment of the single-chip microcomputer more accurate and reliable, and enhancing the sensitivity of the entire current detection module to small current changes, so that the working state of the ballast can be detected more accurately and abnormal conditions such as open circuit can be discovered in time. The voltage comparison unit is connected in series with the voltage amplification unit, receives the amplified voltage signal, and compares it with the internally set reference voltage. According to the comparison result, the corresponding high and low level signals are output. When the amplified voltage is higher than the reference voltage, a high level is output; otherwise, a low level is output. The voltage comparison unit converts the analog voltage signal into a digital high and low level signal, which is convenient for digital circuits such as single-chip microcomputers to process and judge. This digital output method improves the signal's anti-interference ability and processing speed, so that the single-chip microcomputer can quickly and accurately judge whether the ballast is open circuit according to the output of the voltage comparison unit, thereby realizing automatic identification and protection functions. The single-chip microcomputer U2 receives the high and low level signals output by the voltage comparison unit through the PB13 pin, and judges the working state of the ballast according to the signal. When a high-level or low-level signal is received, the microcontroller can determine whether the ballast has an open-circuit fault based on preset programs and algorithms, and take corresponding protective measures, such as cutting off the power supply, issuing an alarm signal, etc.

[0038] In this embodiment, the voltage amplification unit includes an operational amplifier OP1, a feedback resistor RF1, a resistor R502, and a resistor R503. The non-inverting input terminal and the inverting input terminal of the operational amplifier are respectively connected to the two ends of the sampling resistor R501, the resistor R502 and the resistor R503 are respectively connected in series to the non-inverting input terminal and the inverting input terminal, the positive power supply terminal of the operational amplifier OP1 is connected to the power supply, the negative power supply terminal of the operational amplifier OP1 is grounded, the negative power supply terminal of the operational amplifier OP1 is connected in series with a capacitor C503, the output terminal of the operational amplifier OP1 is connected to the voltage comparison unit, and the two ends of the feedback resistor RF1 are respectively connected to the output terminal of the operational amplifier OP1 and the inverting input terminal of the operational amplifier OP1.

[0039] As the core amplifier component, the operational amplifier OP1 amplifies the weak voltage difference across the sampling resistor R501. Its high gain characteristic can amplify the input tiny voltage signal to a suitable amplitude so that the subsequent circuit (such as the voltage comparison unit) can process and judge it. The feedback resistor RF1 and the operational amplifier OP1 form a negative feedback circuit, which determines the amplification factor of the operational amplifier. Different resistance values ​​of the feedback resistor RF1 can set different amplification factors to meet the requirements of the subsequent circuit for the signal amplitude. Negative feedback can also improve the performance of the operational amplifier, such as reducing the temperature drift of the gain, increasing the bandwidth, reducing nonlinear distortion, etc., making the amplified signal more stable and accurate. Resistors R502 and R503 are connected in series to the in-phase input and inverting input of the operational amplifier OP1, respectively, to play the role of current limiting and voltage dividing. Current limiting can prevent excessive current from flowing into the input of the operational amplifier and protect the operational amplifier from being damaged; voltage dividing can adjust the voltage input to the two ends of the operational amplifier according to the specific requirements of the circuit so that it works within a suitable range. Capacitor C503 is connected in series to the negative power supply end of the operational amplifier OP1 to play a filtering role. Filter out high-frequency noise and interference in the power supply to provide a cleaner and more stable power supply environment for the operational amplifier.

[0040] In this embodiment, the voltage comparison unit includes a voltage comparator COMP1 and a reference voltage source REF1. The inverting input terminal of the voltage comparator COMP1 is connected to the output terminal of the voltage amplification unit, the non-inverting input terminal of the voltage comparator COMP1 is connected to the reference voltage source REF1, the positive power supply terminal of the voltage comparator COMP1 is connected to the power supply, the negative power supply terminal of the voltage comparator COMP1 is grounded, the positive power supply terminal and the negative power supply terminal of the voltage comparator COMP1 are respectively connected in series with capacitors C504 and C505, and the output terminal of the voltage comparator COMP1 is connected to the PB13 pin of the microcontroller U2.

[0041] The core function of the voltage comparator COMP1 is to compare the voltage signal output by the voltage amplifier unit with the reference voltage provided by the reference voltage source REF1. When the amplified voltage is higher than the reference voltage, a low level is output; when the amplified voltage is lower than the reference voltage, a high level is output. Through this comparison, the analog voltage signal is converted into a digital high and low level signal, which is convenient for digital circuits such as microcontrollers to process and judge. The reference voltage source REF1 provides a stable and accurate reference voltage for the non-inverting input of the voltage comparator COMP1. This reference voltage is the reference standard for voltage comparison, and its stability and accuracy directly affect the result of voltage comparison and the performance of the entire circuit. Capacitors C504 and C505 are connected in series to the positive power supply terminal and the negative power supply terminal of the voltage comparator COMP1, respectively, to play a filtering role. Filter out high-frequency noise and interference in the power supply to provide a cleaner and more stable power supply environment for the voltage comparator.

[0042] In this embodiment, the reference voltage source REF1 adopts a voltage regulator TL431, the anode of the voltage regulator TL431 is grounded, the cathode of the voltage regulator TL431 is connected to the power supply, the reference electrode of the voltage regulator TL431 is connected to the non-inverting input terminal of the voltage comparator COMP1, and a resistor R504 is connected in series between the cathode of the voltage regulator TL431 and the reference electrode.

[0043] The voltage regulator TL431 is used as a reference voltage source to provide a stable and accurate reference voltage for the voltage comparator COMP1. TL431 has a 2.5V reference voltage source inside. Through the connection of the external circuit, its output voltage can be set to any stable value between 2.5V and 36V. In this circuit, its cathode is connected to the power supply, the anode is grounded, and the reference electrode is connected to the in-phase input terminal of the voltage comparator COMP1. In conjunction with the resistor R504, the output reference voltage value is determined. Resistor R504 cooperates with the voltage regulator TL431 to determine the specific value of the reference voltage through the voltage division principle. By changing the resistance value of R504, the reference voltage output by TL431 can be adjusted to meet the requirements of the voltage comparator COMP1 for the reference voltage. Resistor R504 provides a flexible way to adjust the reference voltage, so that circuit designers can accurately set the reference voltage value according to actual needs, enhance the adaptability and adjustability of the circuit, and facilitate the use with different voltage amplifier units and voltage comparators to achieve accurate detection and judgment of the ballast for open circuit faults.

[0044] The working process of the circuit for automatically identifying and protecting the open circuit fault of the electronic ballast in this embodiment is as follows: 1. Normal working state: the single-chip computer U2 outputs PWM_L and PWM_H signals, which are processed by the signal processing unit and driven by the driving unit to emit light normally. At this time, a normal current passes through the sampling resistor R501 in the current detection module, generating a voltage drop, which is amplified and compared with the reference voltage. At this time, the amplified voltage is greater than the reference voltage, and the voltage comparator COMP1 outputs a low level to the PB13 pin of the single-chip computer. At the same time, the signal of the input terminal VLMAP2 reaches the OPEN_IO pin after being processed by the open circuit detection unit. Because the ballast is working normally, the voltage of the input terminal VLMAP2 is small, which is not enough to turn on the source and drain of the MOS tube Q102, so the voltage at the OPEN_IO pin is close to 0V. The single-chip computer determines that the ballast is working normally based on the status of these two pins and continuously outputs a normal driving signal. 2. Open circuit state of UV lamp: The voltage at the input terminal VLMAP2 will generate a peak voltage. After voltage division, the source and drain of MOS tube Q102 are turned on, and the voltage at the OPEN_IO pin increases. At the same time, the output loop circuit of the UV lamp instantly becomes zero, and the voltage drop across the sampling resistor R501 in the current detection module becomes zero. The amplified voltage is less than the reference voltage, and the voltage comparator COMP1 outputs a high level to the PB13 pin of the microcontroller. Protection action: When the microcontroller U2 detects that the voltage at the OPEN_IO pin increases and the PB13 pin becomes a high level, it determines that the ballast has an open circuit fault, and immediately outputs a control signal to the ballast drive circuit (such as controlling the U301 chip to stop working or adjust its output state), turning off the output of the ballast, thereby protecting the ballast. At the same time, the microcontroller can also record fault information and send the fault information to external devices through communication interfaces (such as serial ports, Bluetooth, etc., if there are relevant modules in the circuit) for alarm or further processing.

[0045] In this embodiment, the combination of the open circuit detection unit and the current detection module can improve the accuracy of fault detection. If the voltage change of the OPEN_IO pin is used to determine whether the ultraviolet lamp is open, this single detection method may result in misjudgment. After combining the current detection and protection module, the detection of the output circuit current of the ultraviolet lamp is added, forming a dual detection mechanism of voltage and current. When the lamp tube is open, not only the voltage of the OPEN_IO pin will change, but the output circuit current will also become zero. Only when these two conditions are met at the same time, the single-chip microcomputer will determine it as an open circuit fault, which greatly improves the accuracy of fault detection and avoids misjudgment caused by abnormal single detection signal. At the same time, the combination of the two forms a comprehensive protection mechanism, covering a variety of possible fault conditions of the ballast, from open circuit to various current anomalies, can be effectively monitored and protected. This makes the entire electronic ballast system more stable and reliable, reduces downtime and maintenance costs caused by faults, and improves system availability and user satisfaction.

[0046] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A circuit for automatically identifying open circuit faults of electronic ballasts and protecting them, characterized in that: It includes a single-chip computer U2, a signal processing unit, a driving unit, and an open circuit detection unit. The input end of the signal processing unit is connected to the signal output pin of the single-chip computer U2. The signal processing unit processes the signal output by the single-chip computer U2 and transmits it to the driving unit and the open circuit detection unit. The input end of the driving unit is connected to the driving signal output end of the signal processing unit. The driving unit outputs a driving signal according to the signal output by the signal processing unit. The input end of the open circuit detection unit is connected to the voltage output end of the driving unit. The output end of the open circuit detection unit is connected to the detection signal input end of the single-chip computer U2. The open circuit detection unit processes the voltage output by the driving unit and transmits it to the single-chip computer U2. The single-chip computer U2 determines the circuit condition through the signal output by the open circuit detection unit and outputs a corresponding signal to the signal processing unit.

2. A circuit for automatically identifying an open circuit fault of an electronic ballast and protecting the electronic ballast according to claim 1, characterized in that: The signal processing unit is a gate drive chip U301, the signal output pins of the single-chip computer U2 are the PB14 pin and the PB15 pin, the input end of the gate drive chip U301 is the HIN pin and the LIN pin, the PB14 pin is connected to the LIN pin, a resistor R305 is connected in series between the PB14 pin and the LIN pin, the PB15 pin is connected to the HIN pin, a resistor R304 is connected in series between the PB15 pin and the HIN pin, the single-chip computer U2 outputs a PWM_L signal through the PB14 pin, the PB14 pin transmits the PWM_L signal to the gate drive chip U301 through the resistor R305 and the LIN pin, the single-chip computer U2 outputs a PWM_H signal through the PB15 pin, the PB15 pin transmits the PWM_H signal to the gate drive chip U301 through the resistor R304 and the HIN pin.

3. A circuit for automatically identifying an open circuit fault of an electronic ballast and protecting the electronic ballast according to claim 1, characterized in that: The driving unit includes a MOS tube Q301 and a MOS tube Q302, and the driving signal output end of the signal processing unit is a HO pin and a LO pin; The HO pin is connected to the gate of the MOS tube Q301, R302 is connected in series between the HO pin and the gate of the MOS tube Q301, the drain of the MOS tube Q301 is connected to the power supply vdc1, the LO pin is connected to the gate of the MOS tube Q302, R306 is connected in series between the LO pin and the gate of the MOS tube Q302, the source of the MOS tube Q302 is grounded, the drain of the MOS tube Q302 is connected to the source of the MOS tube Q301, and the MOS tube Q301 and the MOS tube Q302 are alternately turned on and off under the signals of the HO pin and the LO pin of the signal processing unit.

4. The circuit for automatically identifying an open circuit fault of an electronic ballast and protecting the electronic ballast according to claim 1, characterized in that: The voltage generated by the driving unit reaches the input terminal VLAMP2 of the open circuit detection unit after being divided by resistors RL1, RL2 and RL3. The open circuit detection unit includes a resistor R131, a resistor R112, a diode D111, a voltage regulator ZD106 and a MOS tube Q102. The diode D111, the resistor R131, the resistor R112, and the voltage regulator ZD106 are connected in series in sequence, the anode of the diode D111 is connected to the input terminal VLAMP2, the anode of the voltage regulator ZD106 is connected to the gate of the MOS tube Q102, the source of the MOS tube Q102 is connected to the power supply, the drain of the MOS tube Q102 is connected to the output terminal OPEN_IO of the open circuit detection unit, and the output terminal OPEN_IO is connected to the PA15 pin of the single-chip computer U2; The voltage of the input terminal VLAMP2 reaches the gate of the MOS tube Q102 after passing through the diode D111, the resistor R131, the resistor R112, and the voltage regulator ZD106; when the circuit is open, the voltage reaching the gate of the MOS tube Q102 from the input terminal VLAMP2 is greater than the voltage threshold of the gate of the MOS tube Q102, the source and the drain of the MOS tube Q102 are turned on, the current flows to the output terminal OPEN_IO, and the PA15 pin of the single-chip computer U2 detects the current; when the ballast works normally, the voltage reaching the gate of the MOS tube Q102 from the input terminal VLAMP2 is less than the voltage threshold of the gate of the MOS tube Q102, no current flows to the output terminal OPEN_IO, and the PA15 pin of the single-chip computer U2 does not detect the current.

5. The circuit for automatically identifying an open circuit fault of an electronic ballast and protecting the electronic ballast according to claim 1, characterized in that: It also includes a current detection module, which includes a sampling resistor R501, a voltage amplification unit, and a voltage comparison unit; The sampling resistor R501 is connected in series on the output circuit of the electronic ballast. The sampling resistor R501 adopts a high-precision small-resistance sampling resistor. The voltage amplifying unit is connected in parallel at both ends of the sampling resistor R501. The voltage amplifying unit collects the voltage difference between the two ends of the sampling resistor R501, amplifies the voltage difference and outputs it. The voltage comparison unit is connected in series with the voltage amplifying unit. The voltage comparison unit receives the voltage output by the voltage amplifying unit, compares the output voltage with the reference voltage and outputs the corresponding high and low levels. The output end of the voltage comparison unit is connected to the PB13 pin of the single-chip computer U2. The single-chip computer U2 determines whether the ballast is open according to the high and low levels output by the voltage comparison unit.

6. A circuit for automatically identifying an open circuit fault of an electronic ballast and protecting it according to claim 5, characterized in that: The voltage amplification unit includes an operational amplifier OP1, a feedback resistor RF1, a resistor R502, and a resistor R503; The non-inverting input terminal and the inverting input terminal of the operational amplifier are respectively connected to the two ends of the sampling resistor R501, the resistor R502 and the resistor R503 are respectively connected in series to the non-inverting input terminal and the inverting input terminal, the positive power supply terminal of the operational amplifier OP1 is connected to the power supply, the negative power supply terminal of the operational amplifier OP1 is grounded, the capacitor C503 is connected in series to the negative power supply terminal of the operational amplifier OP1, the output terminal of the operational amplifier OP1 is connected to the voltage comparison unit, and the two ends of the feedback resistor RF1 are respectively connected to the output terminal of the operational amplifier OP1 and the inverting input terminal of the operational amplifier OP1.

7. A circuit for automatically identifying an open circuit fault of an electronic ballast and protecting the same according to claim 5, characterized in that: The voltage comparison unit includes a voltage comparator COMP1 and a reference voltage source REF1. The inverting input terminal of the voltage comparator COMP1 is connected to the output terminal of the voltage amplification unit, the non-inverting input terminal of the voltage comparator COMP1 is connected to the reference voltage source REF1, the positive power supply terminal of the voltage comparator COMP1 is connected to the power supply, the negative power supply terminal of the voltage comparator COMP1 is grounded, the positive power supply terminal and the negative power supply terminal of the voltage comparator COMP1 are respectively connected in series with capacitors C504 and C505, and the output terminal of the voltage comparator COMP1 is connected to the PB13 pin of the microcontroller U2.

8. A circuit for automatically identifying an open circuit fault of an electronic ballast and protecting the same according to claim 7, characterized in that: The reference voltage source REF1 adopts a voltage regulator TL431, the anode of the voltage regulator TL431 is grounded, the cathode of the voltage regulator TL431 is connected to the power supply, the reference electrode of the voltage regulator TL431 is connected to the in-phase input terminal of the voltage comparator COMP1, and a resistor R504 is connected in series between the cathode of the voltage regulator TL431 and the reference electrode.

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