CN102883514B - Fluorescent tube lighting device and driving method thereof - Google Patents

Abstract

The invention relates to a fluorescent tube lighting device and a driving method thereof, wherein the fluorescent tube lighting device comprises a fluorescent tube, an open circuit protection unit and a driving device, the driving device comprises a current converter and a power supply unit, the current converter receives a power supply voltage and lights the fluorescent tube in a double high voltage mode according to a trigger signal. The open-circuit protection unit can detect and judge the open-circuit condition at the two ends of the fluorescent lamp tube to generate an open-circuit protection signal; the inverter receives a power voltage and lights the fluorescent lamp tube by a double high voltage mode according to a trigger signal; the power unit coupled to the open circuit protection unit and the inverter is used for providing power voltage and determining whether to turn off the inverter according to the open circuit protection signal. Therefore, when the fluorescent lamp tube is open-circuited or the driving voltage of the fluorescent lamp tube is greater than the rated operating voltage, the inverter is immediately turned off to avoid the situations of overheating and burning of the elements.

Description

Fluorescent tube lighting device and driving method thereof

technical field

The present invention relates to a lighting device, and in particular to a fluorescent tube lighting device with open circuit protection and overvoltage protection functions and a driving method thereof.

Background technique

Fluorescent tubes have the advantages of low operating temperature, high luminous efficiency, long service life, and multiple colors, so they are widely used in today's lighting equipment, such as indoor lighting, backlight modules for display panels, and other applications. The electric energy conversion circuit, also known as an inverter, is usually used to drive/light a cold cathode fluorescent lamp (Cold Cathode Fluorescenee Lamp; CCFL). The inverter receives a direct current (DC) input voltage and provides an alternating current (AC) driving voltage to the CCFL.

As far as the method of lighting the fluorescent tube is concerned, two methods can be distinguished at present: lighting with a single high voltage method, or lighting with a double high voltage method. The single high-voltage method means that one end of the fluorescent tube receives the driving voltage provided by the inverter, and the other end of the fluorescent tube is electrically connected to the ground terminal, so that the fluorescent tube can be lighted accordingly. In a suitable example, the above-mentioned single high-voltage method is also called a lighting method in which one side is high voltage and the other side is low voltage.

However, lighting with a single high voltage will cause the lighting equipment to operate in a positive voltage cycle in a certain period and in a negative voltage cycle in another period, which will cause low energy conversion efficiency and cause power components in the lighting equipment The temperature rises, thus affecting the service life of the fluorescent tube. In contrast, the double high-voltage lighting equipment uses electronic components to raise the level at both ends of the fluorescent tube, so that the AC drive voltage generated by the inverter only needs to oscillate at a single voltage level. For example, the above-mentioned The AC drive voltages are all raised to a positive voltage level. Compared with the single high voltage lighting method, the double high voltage lighting method has better energy conversion efficiency and slows down the temperature rise of power components.

At present, most fluorescent lamps on the market are lit by a single high-voltage method. This type of lighting technology usually uses the voltage signal in the fluorescent lamp that is closer to the ground voltage to perform circuit protection measures such as open circuit protection and overvoltage protection. The reason is that low-voltage signals are easier. Processing, and these circuit protection measures must also be available in practical applications. On the other hand, due to the relatively new driving technology of dual high-voltage lighting, and both ends of the fluorescent tube are high-voltage signals, it is difficult to process and convert these high-voltage signals with conventional circuit protection measures. Therefore, in order to innovate and break through the currently known fluorescent tube driving technology, how to develop a circuit protection measure applicable to the dual high voltage mode is an urgent and unresolved direction in this field.

Contents of the invention

The invention provides a fluorescent tube lighting device and its driving method. When the tube is open circuited or the drive voltage of the tube exceeds the rated operating voltage, the inverter will be shut down immediately to avoid causing components Conditions of overheating and burning.

The invention provides a lighting device for a fluorescent tube, which includes a fluorescent tube, an AC/DC voltage converter, an open circuit protection unit, and a driving device. The AC/DC voltage converter receives an AC voltage and converts the AC voltage into a first DC voltage and a second DC voltage respectively. The open circuit protection unit is coupled to the fluorescent tube, which can detect and judge the open circuit of both ends of the fluorescent tube to generate an open circuit protection signal. The drive device includes an inverter and a power supply unit. The inverter coupled to the fluorescent tube receives and operates under a power supply voltage, and uses a double high voltage method to light the fluorescent tube according to a trigger signal. The power supply unit is coupled to the open-circuit protection unit and the converter. The power supply unit can provide the above-mentioned power supply voltage, and determines whether to shut down the converter by stopping supplying the power supply voltage according to the open-circuit protection signal generated by the open-circuit protection unit.

In an embodiment of the present invention, the fluorescent tube lighting device further includes an overvoltage protection unit coupled between the open circuit protection unit and the power supply unit. The overvoltage protection unit generates and outputs an overvoltage protection signal when the level of the open circuit protection signal is greater than an operating voltage. Therefore, the above-mentioned power supply unit will determine whether to stop supplying the power supply voltage according to the above-mentioned open-circuit protection signal and the over-voltage protection signal, so as to determine whether to turn off the inverter.

In an embodiment of the present invention, the above-mentioned power supply unit includes an oscillation unit, a switching control unit, and a switching unit. The oscillating unit is charged with a first DC voltage to generate a charging voltage and a trigger signal. The switching control unit uses the charging voltage to charge, and generates a power supply signal according to the charging voltage and the open circuit protection signal. The switching unit receives a second direct current voltage and determines whether to provide the second direct current voltage as the power supply voltage to the converter according to the power supply signal. In some embodiments, the power supply unit further includes a voltage stabilizing unit, and the voltage stabilizing unit can stabilize the second DC voltage to the power supply voltage.

In an embodiment of the present invention, the oscillation unit can also receive a commutation signal from the inverter, and when the inverter starts to operate, the inverter will pull down the commutation signal to the ground voltage, so that the oscillation unit Stop generating charging voltage and trigger signal. Therefore, if the two ends of the fluorescent tube are not open, the open circuit protection unit will continuously enable the open circuit protection signal, so that the switching control unit can use the open circuit protection signal to charge, so that when the oscillation unit stops generating the charging voltage, Continuously generate power supply signal. On the other hand, if the two ends of the fluorescent tube are open-circuited, the open-circuit protection unit will disable the open-circuit protection signal, so that the switching control unit stops generating the power supply signal.

From another point of view, the present invention provides a method for driving a fluorescent lamp, which includes the following steps. A power supply voltage is provided to an inverter, so that the inverter can light the fluorescent lamp by means of a double high voltage according to a trigger signal. Detect open-circuit conditions at both ends of the fluorescent tube to generate an open-circuit protection signal. And, according to the open circuit protection signal, it is determined whether to shut down the converter. In addition, for other implementation details of the driving method of the fluorescent tube, please refer to the above description, and will not be repeated here.

Based on the above, the open-circuit protection unit of the embodiment of the present invention will continue to enable the above-mentioned open-circuit protection signal when the lamp tube is operating normally, so that the switching control unit in the power supply unit can continuously generate power supply signals, so that the inverter can operate normally. Bright fluorescent tubes. In contrast, when the lamp is open circuit (usually occurs when the lamp is broken or the lamp is abnormal), the open circuit protection signal will be disabled accordingly, and the power supply signal will be stopped immediately to shut down the inverter in real time.

On the other hand, if the AC drive voltage output by the inverter is higher than the rated operating voltage, the overvoltage protection unit will also generate an overvoltage protection signal to immediately shut down the inverter. Therefore, when the above two situations occur, the lighting device according to the embodiment of the present invention can shut down the inverter in time so that it cannot continue to increase the driving voltage of the fluorescent tube, so as to avoid possible dangerous situations such as overheating and burning of the components.

Description of drawings

FIG. 1 is a schematic block diagram of a fluorescent tube lighting device according to an embodiment of the present invention.

FIG. 2 is a partial circuit diagram of a fluorescent tube lighting device according to an embodiment of the present invention.

FIG. 3 is another partial circuit diagram of the fluorescent tube lighting device according to an embodiment of the present invention.

[Description of main component symbols]

100: Lighting equipment for fluorescent tubes

110: Fluorescent tube

120: Inverter

122: Controller

124: High side driver

126: switch unit

128: Resonance tank

130: Power supply unit

132: AC/DC voltage converter

134: Oscillating unit

136: switch control unit

138: Switch unit

139: voltage stabilizing unit

140: Open circuit protection unit

150: Overvoltage protection unit

160: Feedback detection unit

170: auxiliary voltage generator

AC: AC voltage

CPV: charging voltage

DC_H: first DC voltage

DC_L: second DC voltage

DC_aux: auxiliary voltage

DV: AC drive voltage

FB: feedback signal

INS: commutation signal

OLPS: open circuit protection signal

OVPS: overvoltage protection signal

PLS: power supply signal

PWM1, PWM2: pulse width modulation signal

TRS: trigger signal

VCC: supply voltage

R1～R12: resistance

C1～C9: capacitance

D1～D6: Diodes

DZ1～DZ4: Zener diodes

L1: Inductance

MP1, MN1～MN2: Transistors

DBI: bidirectional diode

T1, T11, T12: Transformers

SW1, SW2: switch

A, B, C: nodes

Detailed ways

In order to make the above-mentioned features and advantages of the present invention more comprehensible, the following specific embodiments are described in detail together with the accompanying drawings.

Reference will now be made in detail to the exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. In addition, wherever possible, elements/components/symbols with the same reference numerals are used in the drawings and embodiments to represent the same or similar parts.

FIG. 1 is a schematic block diagram of a lighting device 100 using a fluorescent tube 110 according to an embodiment of the present invention. 1, the lighting device 100 can drive a fluorescent tube (fluorescent tube) 110 for lighting, so the lighting device 100 includes a fluorescent tube 110, an AC/DC voltage converter 132, an open circuit protection unit 140 and a driving device. The driving device includes an inverter 120 and a power unit 130 . In this embodiment, the lighting device 100 may further include an overvoltage protection unit 150 , a feedback detection unit 160 and an auxiliary voltage generator 170 , and the structure and operation of these components will be described one by one below.

The fluorescent tube 110 can be, for example, a cold-cathode fluorescent tube with specifications such as T1 and T3, or a hot-cathode (hot-cathode) fluorescent tube with other specifications. Therefore, as long as it is a fluorescent tube that can be lit/driven by a dual-high voltage method, it belongs to The fluorescent tube 110 described in the embodiment of the present invention. The power unit 130 is used to provide a power voltage VCC. In terms of the detailed structure of the power unit 130 , the power unit 130 includes an oscillation unit 134 , a switch control unit 136 and a switch unit 138 . In addition, the power unit 130 also includes a voltage stabilizing unit 139 . The braking method of the AC/DC voltage converter 132 and the power unit 130 will be described below.

The AC/DC voltage converter 132 receives the AC voltage AC, and converts the AC voltage AC into a first DC voltage DC_H and a second DC voltage DC_L, wherein the level of the first DC voltage DC_H is greater than the level of the second DC voltage DC_L , so that the AC/DC voltage converter 132 can respectively provide voltages of different levels to the required electronic components. Wherein, the AC/DC voltage converter 132 can be implemented by using electronic components such as bridge rectifiers and filter capacitors, which will not be repeated here.

The oscillating unit 134 is charged by the first DC voltage D CH to generate the charging voltage CPV and the trigger signal TRS. The switching control unit 136 uses the charging voltage CPV for charging, and generates a power supply signal PLS according to the charging voltage CPV and the open circuit protection signal OLPS. Moreover, the switch unit 138 receives the second DC voltage DC_L, and determines whether to provide the second DC voltage DC_L as the power supply voltage VCC of the converter 120 according to the power supply signal PLS. The voltage stabilizing unit 139 is coupled between the switching unit 138 and the inverter 120 for stabilizing the second DC voltage DC_L at the power supply voltage VCC.

Please continue to refer to FIG. 1 , the inverter 120 can receive and operate under the power voltage VCC, and generate an AC driving voltage DV according to the trigger signal TRS for lighting the fluorescent tube 110 in a dual high voltage manner. The detailed structure of the inverter 120 is described in detail here. The inverter 120 includes a controller 122 , a high voltage side driver 124 , a switch unit 126 and a resonant tank 128 .

The controller 122 operates under the power voltage VCC, and generates a first pulse width modulation signal PWM1 and a second pulse width modulation signal PWM2 according to the trigger signal TRS. The high voltage side driver 124 is coupled to the controller 122 and used for adjusting the level of the first pulse width modulation signal PWM1. The switch unit 126 is coupled to the controller 122 and the high-side driver 124 . The switch unit 126 receives the first DC voltage DC_H, and makes the first DC voltage DC_H controlled by the second PWM signal PWM2 and the adjusted first PWM signal PWM1 to generate the commutation signal INS. With the mutual switching of the conduction states of the switch unit 126 , the power transmitted from the first DC voltage DC_H to the resonant tank 128 can be controlled. Thus, the resonant tank 128 will generate a corresponding AC driving voltage DV, and then light the fluorescent tube 110 in a dual high voltage driving manner.

In order to prevent the oscillation unit 134 from continuously generating the trigger signal TRS during the operation of the inverter 120, when the inverter 120 starts to operate, the commutation signal INS generated by the switching unit 126 will follow the first pulse width The mutual switching of the modulation signal PWM1 and the second pulse width modulation signal PWM2 is pulled down to the ground voltage, so that the oscillation unit 134 stops generating the charging voltage CPV and the trigger signal TRS. In some embodiments, after the oscillating unit 134 stops generating the charging voltage CPV, the fluorescent lamp 110 is already on, and the switching control unit 136 is charged by the open circuit protection signal OLPS to continuously generate the power supply signal PLS. , let the inverter 120 continuously light the fluorescent tube 110 .

However, if the fluorescent tube 110 is not actually lit at this time, or the two ends of the fluorescent tube 110 are in an open circuit state, this open circuit situation usually occurs when the lamp tube is damaged and broken, and the lamp tube is disconnected. In the case of incorrect placement or abnormality of the lamp tube, if there is no specific circuit protection measure to perform functions such as open circuit protection or overvoltage protection, the inverter 120 will continue to increase the voltage level of the AC driving voltage DV .

Because the lighting equipment 100 that is lit in a double high voltage way often makes the level of the driving voltage DV higher than 300V, in other words, the driving voltage level at both ends of the fluorescent tube 110 is usually between 300V and 3000V (this is just an example). , the embodiments of the present invention are not limited to this voltage range). Such a high-voltage driving method is very likely to cause overheating of the electronic components in the lighting device 100, and even burns due to excessive driving voltage DV. As a result, the fluorescent tube 110 and the lighting device 100 will be damaged due to overheating. .

Here, the embodiment of the present invention utilizes the open circuit protection unit 140 and the overvoltage protection unit 150 of FIG. 1 to achieve functions such as open circuit protection and overvoltage protection. That is to say, the open-circuit protection unit 140 in FIG. 1 can detect and determine the open-circuit situation at both ends of the fluorescent lamp 110 to generate the open-circuit protection signal OLPS. The overvoltage protection unit 150 is coupled to the open circuit protection unit 140 and the power supply unit 130 , and generates the overvoltage protection signal OVPS when the level of the open circuit protection signal OLPS is greater than a rated operating voltage. The switching control unit 136 in the power supply unit 130 determines whether to stop generating the power supply signal PLS according to the open circuit protection signal OLPS and the overvoltage protection signal OVPS, so as to control the switching unit 138 to stop providing the second DC voltage DC_L.

Therefore, when the fluorescent tube 110 is not actually lit, or when both ends of the fluorescent tube 110 are in an open state, the lighting device 100 of the fluorescent tube 110 can immediately turn off the inverter 120 to avoid illuminating The electronic components in the device 100 produce adverse conditions such as overheating or burning, which further prolongs the service life of the fluorescent tube 110 and the lighting device 100 .

Please continue to refer to FIG. 1 , the feedback detection unit 160 can detect the fluorescent tube 110 and generate a feedback signal FB according to the detection result. Therefore, the controller 122 can adjust the duty cycle or frequency of the first PWM signal PWM1 and the second PWM signal PWM2 according to the feedback signal FB, so as to improve the lighting efficiency of the fluorescent tube 110 . In addition, the lighting device 100 of the fluorescent tube 110 can generate an auxiliary voltage DC_aux through the auxiliary voltage generator 170 and transmit the auxiliary voltage DC_aux to the switching unit 138 to stabilize the operation performance of the lighting device 100 . Therefore, the voltage stabilizing unit 139 can also use the auxiliary voltage DC_aux to generate the working voltage VCC required by the controller 122 . Briefly, the auxiliary voltage generator 170 responds to the resonant tank 128 in the inverter 120 to generate the auxiliary voltage DC_aux.

In order to enable those skilled in the art to better understand the embodiment of the present invention, FIG. 2 is a partial circuit diagram of a fluorescent lamp 110 lighting device 100 according to an embodiment of the present invention. Please refer to FIG. 2 below to illustrate the oscillation unit 134 and switching control The circuit structure of the unit 136 , the switching unit 138 and the voltage stabilizing unit 139 .

Referring to FIG. 2 , the oscillation unit 134 includes resistors R1 - R3 , a resistor R9 , a capacitor C3 , a diode D3 , a bidirectional diode DBI and a zener diode DZ2 . The first terminals of the resistors R1 and R9 receive the first DC voltage DC_H, the second terminal of the resistor R1 is used to provide the charging voltage CPV, and the second terminal of the resistor R9 is coupled to a ground terminal. The first end of the capacitor C3 is coupled to the second end of the resistor R1, and the second end of the capacitor C3 is coupled to the ground. The anode of the diode D3 is coupled to the second end of the resistor R1 , and the cathode of the diode D3 receives the commutation signal INS generated by the switching unit 126 of the inverter 120 .

The first anode of the bidirectional diode DBI is coupled to the second terminal of the resistor R1, and the first terminal of the resistor R2 is coupled to the second anode of the bidirectional diode DBI, and the second terminal of the resistor R2 is used to provide the trigger signal TRS. The first end of the resistor R3 is coupled to the second end of the resistor R2, and the second end of the resistor R3 is coupled to the ground. The cathode of the Zener diode DZ2 is coupled to the second end of the resistor R2, and the anode of the Zener diode DZ2 is coupled to the ground.

In circuit operation, assuming that the inverter 110 has not started to operate, the inverter signal INS should be floating, so the diode D3 is in a non-conductive state. At this time, the first DC voltage DC_H charges the capacitor C3 through the resistor R1 to generate the charging voltage CPV. When the charging voltage CPV is greater than the critical voltage of the bidirectional diode DBI, the bidirectional diode DBI will be turned on. At this time, the voltage adjustment circuit formed by the resistors R2, R3 and the Zener diode DZ2 will generate the trigger signal TRS.

On the other hand, when the inverter 120 starts to operate due to the activation of the controller 122 , the level of the inverter signal INS generated by the switch units 126 will be pulled down to the ground voltage along with mutual switching. At this time, the diode D3 will be in a conduction state, which will cause the level of the node A to approach the ground voltage. Therefore, the oscillation unit 134 stops generating the charging voltage CPV and the trigger signal TRS after the inverter 120 is activated.

The switching control unit 136 includes resistors R4 - R6 , capacitors C4 - C5 , diodes D4 - D5 and an N-type transistor MN1 . The anode of the diode D4 is used to receive the charging voltage CPV. The anode of the diode D5 is used to receive the open circuit protection signal OLPS, and the cathode of the diode D5 is coupled to the cathode of the diode D4. A first end of the resistor R4 is coupled to the cathode of the diode D4, and a second end of the resistor R4 is used to provide the power supply signal PLS. The first end of the capacitor C4 is coupled to the second end of the resistor R4, and the second end of the capacitor C4 is coupled to the ground. A first end of the resistor R5 is coupled to a second end of the resistor R4, and a second end of the resistor R5 is coupled to the ground.

In this embodiment, the drain of the N-type transistor MN1 is coupled to the second end of the resistor R4. The gate of the N-type transistor MN1 receives the overvoltage protection signal OVPS, and the source of the N-type transistor MN1 is coupled to the ground terminal. Both the first ends of the capacitor C5 and the resistor R6 are coupled to the gate of the N-type transistor MN1 , and the second ends of the capacitor C5 and the resistor R6 are both coupled to the ground.

Therefore, in the circuit operation, it is assumed that neither the open-circuit protection signal OLPS nor the over-voltage protection signal OVPS is generated yet, so the switching control unit 136 only receives the charging voltage CPV from the oscillation unit 134 . Therefore, the diode D4 will be turned on according to the charging voltage CPV, and the charging voltage CPV will charge the capacitor C4 through the resistor R4, and the charging delay time depends on the RC effect between the resistor R4 and the capacitor C4. In this way, the adjustment unit 130 can generate the power supply signal PLS accordingly.

Furthermore, when the inverter 120 is activated and the two ends of the fluorescent tube 110 are not open, the open circuit protection unit 140 will continuously enable the open circuit protection signal OLPS, and the enabled open circuit protection signal OLPS will return to diode D5. Therefore, when the oscillation unit 134 stops generating the charging voltage CPV, the returned open-circuit protection signal OLPS turns on the diode D5 to charge the capacitor C4 through the resistor R4. In this way, even if the oscillating unit 134 stops generating the charging voltage CPV, the adjusting unit 136 can still continuously generate the power supply signal PLS when both ends of the fluorescent tube 110 are not open.

In addition, when the level of the open-circuit protection signal OLPS is greater than the rated operating voltage, the over-voltage protection unit 150 will enable the over-voltage protection signal OVPS (for example, make the over-voltage protection signal OVPS higher than the turn-on voltage level of the transistor MN1) . Therefore, the source and the drain of the N-type transistor MN1 are turned on and the level of the power supply signal PLS is pulled down to the ground voltage, that is, the level of the node B approaches the ground voltage. In this way, the switching unit 138 stops transmitting the second DC voltage D LL and the auxiliary voltage DC_aux because there is no supply of the power supply signal PLS.

Returning to FIG. 2 , the switching unit 138 includes resistors R7 - R8 , a capacitor C6 , a P-type transistor MP1 and an N-type transistor MN2 . The source of the P-type transistor MP1 receives the second DC voltage DC_L, and the source of the P-type transistor MP1 is also coupled to the first terminal of the capacitor C6 and the first terminal of the resistor R7. The second terminal of the capacitor C6 is coupled to the ground terminal, and the second terminal of the resistor R7 is coupled to the gate of the P-type transistor MP1. The drain of the P-type transistor MP1 can provide the power supply voltage VCC. The drain of the N-type transistor MN2 is coupled to the gate of the P-type transistor MP1, and the source of the N-type transistor MN2 is coupled to the ground terminal. In addition, the gate of the N-type transistor MN2 receives the power supply signal PLS. A first end of the resistor R8 is coupled to the source of the P-type transistor MP1, and a second end of the resistor R8 is coupled to a second end of the capacitor C6.

Therefore, in circuit operation, the source and drain of the N-type transistor MN2 will be turned on according to the power supply signal PLS, and then the level of the gate of the P-type transistor MP1 will be pulled down to the ground voltage. At this time, the P-type transistor MP1 is also turned on, so that the second DC voltage DC_L and/or the auxiliary voltage DC_aux are transmitted to the voltage stabilizing unit 139 . The capacitor C6, the resistor R7 and the resistor R8 can be used to adjust the conduction speed of the P-type transistor MP1.

The voltage stabilizing unit 139 includes a capacitor C7 and a Zener diode DZ3. The first end of the capacitor C7 is coupled to the cathode of the Zener diode DZ3 and simultaneously receives the power voltage VCC from the switching unit 138 , and the second end of the capacitor C7 and the anode of the Zener diode DZ3 are both coupled to the ground. Therefore, in terms of circuit operation, the voltage from the switching unit 138 will charge the capacitor C7, and the voltage drop across the capacitor C7 will be stabilized at the level of the working voltage VCC through the Zener diode DZ3.

3 is another partial circuit diagram of the lighting device 100 of the fluorescent tube 110 according to an embodiment of the present invention. Please refer to FIG. The circuit structure of the overvoltage protection unit 150 , the feedback detection unit 160 and the auxiliary voltage generator 170 .

Referring to FIG. 3 , the switch unit 126 includes resistors R10 - R11 and switches SW1 - SW2 . In this embodiment, the switches SW1 - SW2 are N-type transistors as an example. In the switch unit 126 , the first end of the resistor R10 receives the adjusted first PWM signal PWM1 , and the first end of the resistor R11 also receives the second PWM signal PWM2 . The second terminals of the resistor R10 and the resistor R11 are respectively coupled to the control terminals of the switch SW1 and the switch SW2 (eg, the gate terminal of the N-type transistor). The first end of the switch SW1 receives the first DC voltage DC_H, and the second end of the switch SW1 and the first end of the switch SW2 are both coupled to the resonant tank 128 . The second end of the switch SW2 is coupled to the ground.

In the resonant tank 128, a capacitor C8 and a transformer T1 are included. A first end of the capacitor C8 is coupled to the switch unit 126 , and the transformer T1 has a primary side T11 and a secondary side T12 . The primary side T11 is coupled between the second terminal of the capacitor C8 and the ground terminal, and the secondary side T12 is connected in parallel with the fluorescent tube 110 .

In circuit operation, the switch SW1 receives the adjusted first PWM signal PWM1 through the resistor R10, and the switch SW2 receives the second PWM signal PWM2 through the resistor R11. Therefore, the switch SW1 and the switch SW2 will adjust their conduction states according to the adjusted first PWM signal PWM1 and the second PWM signal PWM2, so as to control the voltage transmitted from the first DC voltage DC_H to the resonant tank 128 electricity. The resonant tank 128 performs voltage boosting and filtering operations through the capacitor C8 and the transformer T1 to generate an AC driving voltage DV to light the fluorescent lamp 110 .

It should be noted that the open circuit protection unit 140 of this embodiment includes capacitors C1 - C2 and diodes D1 - D2 . A first end of the capacitor C1 is coupled to the fluorescent tube 110 , a second end of the capacitor C1 is coupled to a first end of the capacitor C2 , and a second end of the capacitor C2 is coupled to the ground. The anode and the cathode of the diode D1 are respectively coupled to the ground terminal and the second terminal of the capacitor C1. The anode of the diode D2 is coupled to the second end of the capacitor C1, and the cathode of the diode D2 is used to provide the open circuit protection signal OLPS. In addition, the overvoltage protection unit 150 includes a zener diode DZ1, the anode of which is used to receive the open circuit protection signal OLPS, and the cathode of the zener diode DZ1 is used to provide the overvoltage protection signal OVPS. Wherein, the breakdown voltage of the Zener diode DZ1 is equal to the rated operating voltage. That is to say, the rated operating voltage referred to here is the upper limit value of the voltage level of the overvoltage protection signal OVPS under normal operation.

In the circuit operation, assuming that the two ends of the fluorescent tube 110 are not open and the inverter 120 is started, the AC driving voltage DV of the fluorescent tube 110 received through the capacitor C1 can be divided by the capacitor C1 and the capacitor C2 and The charge storage effect, together with the voltage clamping of the diode D1, will generate an appropriate voltage on the node C to roughly maintain the open circuit protection signal OLPS at an appropriate voltage level. Thus, referring to FIG. 2 and FIG. 3 at the same time, the open circuit protection unit 140 can continuously enable the open circuit protection signal OLPS, so that the adjustment unit 136 can continuously generate the power supply signal PLS.

However, if the two ends of the fluorescent tube 110 are suddenly opened after the inverter 120 is started, the AC driving voltage DV of the fluorescent tube 110 will increase suddenly, and the voltage level of the overvoltage protection signal OVPS will increase accordingly. Therefore, in the circuit operation, when the overvoltage protection signal OVPS exceeds the breakdown voltage of the Zener diode DZ1, it indicates that the AC driving voltage DV is abnormal and exceeds a preset voltage level, so the Zener diode DZ1 of the overvoltage protection unit 150 It will collapse and conduct both ends, so that the voltage level of the overvoltage protection signal OVPS is higher than the conduction voltage of the N-type transistor MN1 in FIG. 2, so that the power supply signal PLS is pulled down to the ground voltage to stop providing the second DC voltage DC_L and the auxiliary voltage DC_aux are supplied to the converter 120 .

In addition, when the two ends of the fluorescent tube 110 are suddenly open-circuited, the AC driving voltage DV may suddenly change from a positive voltage level to a negative voltage level. In this way, through the voltage clamping of the diode D1 and the diode D2, the voltage level of the open circuit protection signal OLPS will be pulled down to approximately equal to the ground voltage (equivalent to disabling the open circuit protection signal OLPS). Therefore, the level of the returned open circuit protection signal OLPS cannot charge the capacitor C4 of the switching control unit 136 in FIG. 2 , so the switching control unit 136 stops generating the power supply signal PLS.

Please continue to refer to FIG. 3 , the feedback detection unit 160 includes a capacitor C9 and a Zener diode DZ4 . A first end of the capacitor C9 is electrically connected to the fluorescent tube 110 . The cathode of the Zener diode DZ4 is coupled to the second end of the capacitor C9, and the anode of the Zener diode DZ4 is electrically connected to the ground. In terms of circuit operation, the Zener diode DZ4 is used to limit the voltage of the second terminal of the capacitor C9. In addition, the capacitor C9 receives the voltage from the fluorescent tube 110 to generate a corresponding feedback signal FB.

On the other hand, the auxiliary voltage generator 170 includes an inductor L1, a diode D6 and a resistor R12. Wherein, the inductor L1 senses the current of the primary side T11 of the transformer T1, and generates an induced current accordingly. In addition, the anode of the diode D6 receives the induced current and transmits it to the first terminal of the resistor R12. Therefore, the auxiliary voltage generator 170 can generate the corresponding auxiliary voltage DC_aux through the second terminal of the resistor R12.

To sum up, the open-circuit protection unit of the embodiment of the present invention will continue to enable the above-mentioned open-circuit protection signal when the lamp is in normal operation, so that the switching control unit in the power supply unit can continuously generate a power supply signal, so that the inverter Light the fluorescent tube normally. In contrast, when the lamp is open circuit (usually occurs when the lamp is broken or the lamp is abnormal), the open circuit protection signal will be disabled accordingly, and the power supply signal will be stopped immediately to shut down the inverter in real time.

On the other hand, if the AC drive voltage output by the inverter is higher than the rated operating voltage, the overvoltage protection unit will also generate an overvoltage protection signal to immediately shut down the inverter. Therefore, when the above two situations occur, the lighting device according to the embodiment of the present invention can shut down the inverter in time so that it cannot continue to increase the driving voltage of the fluorescent tube, so as to avoid possible dangerous situations such as overheating and burning of the components.

Although the present invention has been disclosed as above with the embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the technical field can make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be defined by the scope of the appended patent application.

Claims (23)

1. A lighting device for a fluorescent tube, characterized in that it comprises: a fluorescent tube; an AC/DC voltage converter for receiving an AC voltage and converting the AC voltage into a first DC voltage and a second DC voltage; An open-circuit protection unit, coupled to the fluorescent tube to detect and determine the open-circuit condition at both ends of the fluorescent tube to generate an open-circuit protection signal; and A driving device, comprising: An inverter, coupled to the fluorescent tube, is used to receive a power supply voltage, and light the fluorescent tube in a dual high-voltage manner according to a trigger signal; and A power supply unit, coupled to the open-circuit protection unit and the converter, to provide the power supply voltage, and to determine whether to shut down the converter according to the open-circuit protection signal; it also includes: An overvoltage protection unit, coupled to the open circuit protection unit and the power supply unit, is used to generate an overvoltage protection signal when the level of the open circuit protection signal is greater than a rated operating voltage, wherein the power supply unit is based on the open circuit protection signal and the overvoltage protection signal to determine whether to stop supplying the power supply voltage to the converter. 2. The fluorescent tube lighting device according to claim 1, wherein the overvoltage protection unit comprises: A first Zener diode, the anode of which receives the open circuit protection signal, the cathode of the first Zener diode is used to provide the overvoltage protection signal, and the breakdown voltage of the first Zener diode is equal to the rated operating voltage. 3. The fluorescent tube lighting device according to claim 1, wherein the open circuit protection unit comprises: a first capacitor, the first end of which is coupled to the fluorescent tube; a second capacitor, the first terminal of which is coupled to the second terminal of the first capacitor, and the second terminal of the second capacitor is coupled to a ground terminal; a first diode, the anode of which is coupled to the ground terminal, and the cathode of the first diode is coupled to the second terminal of the first capacitor; and A second diode, the anode of which is coupled to the second terminal of the first capacitor, and the cathode of the second diode is used for providing the open circuit protection signal. 4. The fluorescent tube lighting device according to claim 1, wherein the power supply unit comprises: an oscillating unit, charged by the first DC voltage to generate a charging voltage and the trigger signal; A switching control unit, which uses the charging voltage to charge, and generates a power supply signal according to the charging voltage and the open circuit protection signal; and A switching unit receives the second DC voltage and determines whether to provide the second DC voltage as the power supply voltage to the converter according to the power supply signal. 5. The fluorescent tube lighting device according to claim 4, wherein the oscillation unit receives a commutation signal from the inverter, and when the inverter starts to operate, the inverter The current signal is pulled down to the ground voltage, so that the oscillation unit stops generating the charging voltage and the trigger signal. 6. The lighting device of fluorescent tube as claimed in claim 5, characterized in that, When the two ends of the fluorescent tube are not open, the open circuit protection unit continuously enables the open circuit protection signal, and the switching control unit also uses the open circuit protection signal for charging, so that when the oscillation unit stops generating the charging voltage , continuously generating the supply signal, and, When the two ends of the fluorescent tube are open-circuited, the open-circuit protection unit disables the open-circuit protection signal, so that the switching control unit stops generating the power supply signal. 7. The fluorescent tube lighting device according to claim 5, wherein the switching control unit receives an overvoltage protection signal when the level of the open circuit protection signal is greater than a rated operating voltage, so as to stop generating the power supply signal . 8. The fluorescent tube lighting device according to claim 4, characterized in that the oscillating unit comprises: a first resistor, the first end of which receives the first DC voltage, and the second end of the first resistor is used to provide the charging voltage; a ninth resistor, the first terminal of which receives the first DC voltage, and the second terminal of the ninth resistor is coupled to a ground terminal; a third capacitor, the first terminal of which is coupled to the second terminal of the first resistor, and the second terminal of the third capacitor is coupled to the ground terminal; a third diode, the anode of which is coupled to the second end of the first resistor, and the cathode of the third diode receives a commutation signal of the converter; a bidirectional diode, the first anode of which is coupled to the second end of the first resistor; a second resistor, the first end of which is coupled to the second anode of the bidirectional diode, and the second end of the second resistor is used to provide the trigger signal; a third resistor, the first terminal of which is coupled to the second terminal of the second resistor, and the second terminal of the third resistor is coupled to the ground terminal; and A second Zener diode, the cathode of which is coupled to the second terminal of the second resistor, and the anode of the second Zener diode is coupled to the ground terminal. 9. The fluorescent tube lighting device according to claim 4, wherein the switching control unit comprises: a fourth diode, the anode of which receives the charging voltage; a fifth diode, the anode of which receives the open circuit protection signal, and the cathode of the fifth diode is coupled to the cathode of the fourth diode; a fourth resistor, the first end of which is coupled to the cathode of the fourth diode, and the second end of the fourth resistor is used to provide the power supply signal; a fourth capacitor, the first terminal of which is coupled to the second terminal of the fourth resistor, and the second terminal of the fourth capacitor is coupled to a ground terminal; and a fifth resistor, the first terminal of which is coupled to the second terminal of the fourth resistor, the second terminal of the fifth resistor is coupled to the ground terminal, Wherein, the switching control unit utilizes the charging voltage or the open circuit protection signal to continuously generate the power supply signal. 10. The fluorescent tube lighting device according to claim 9, wherein the switching control unit further comprises: A first N-type transistor, the drain of which is coupled to the second end of the fourth resistor, the gate of the first N-type transistor receives an overvoltage protection signal, and the source of the first N-type transistor is coupled to to the earth terminal; a fifth capacitor, the first terminal of which is coupled to the gate of the first N-type transistor, and the second terminal of the fifth capacitor is coupled to the ground terminal; and a sixth resistor, the first terminal of which is coupled to the gate of the first N-type transistor, and the second terminal of the sixth resistor is coupled to the ground terminal, Wherein, when the overvoltage protection signal is enabled, the level of the power supply signal is pulled down to a ground voltage, so that the switching unit stops transmitting the second DC voltage. 11. The fluorescent tube lighting device according to claim 4, wherein the switching unit comprises: a sixth capacitor, the first terminal of which receives the second DC voltage, and the second terminal of the sixth capacitor is coupled to a ground terminal; a P-type transistor, the source of which receives the second DC voltage, and the drain of the P-type transistor is used to provide the power supply voltage; a seventh resistor, the first end of which is coupled to the source of the P-type transistor, and the second end of the seventh resistor is coupled to the gate of the P-type transistor; an eighth resistor, the first terminal of which is coupled to the source of the P-type transistor, and the second terminal of the eighth resistor is coupled to the second terminal of the sixth capacitor; and A second N-type transistor, the drain of which is coupled to the gate of the P-type transistor, the gate of the second N-type transistor receives the power supply signal, and the source of the N-type transistor is coupled to the ground terminal, wherein The N-type transistor is turned on according to the power supply signal. 12. The fluorescent tube lighting device according to claim 4, wherein the power supply unit further comprises: A voltage stabilizing unit, coupled between the switching unit and the inverter, is used for stabilizing the second DC voltage at the power supply voltage. 13. The fluorescent tube lighting device according to claim 12, wherein the voltage stabilizing unit comprises: a seventh capacitor, the first terminal of which is used to receive the second DC voltage from the switching unit, the second terminal of the seventh capacitor is coupled to a ground terminal; and A third Zener diode, the cathode of which is coupled to the first terminal of the seventh capacitor, and the anode of the third Zener diode is coupled to the ground terminal. 14. The fluorescent tube lighting device according to claim 1, wherein the inverter comprises: a controller, which operates under the power supply voltage, and generates a first pulse width modulation signal and a second pulse width modulation signal according to the trigger signal; a high voltage side driver, coupled to the controller, for adjusting the level of the first PWM signal; a switch unit, coupled to the controller and the high-voltage side driver, for receiving the first direct current voltage and being controlled by the second pulse width modulation signal and the adjusted first pulse width modulation signal; as well as A resonant tank, coupled to the switch unit, is used to generate the driving voltage to light the fluorescent tube. 15. The fluorescent tube lighting device according to claim 14, wherein the switch unit comprises: a tenth resistor, the first terminal of which receives the adjusted first PWM signal; an eleventh resistor, the first end of which receives the second PWM signal; a first switch, the first terminal of which receives the first DC voltage, the control terminal of the first switch is coupled to the second terminal of the tenth resistor, and the second terminal of the first switch is coupled to the resonance tank; as well as A second switch, the first terminal of which is coupled to the second terminal of the first switch, the control terminal of the second switch is coupled to the second terminal of the eleventh resistor, and the second terminal of the second switch is coupled to a ground terminal. 16. The fluorescent tube lighting device according to claim 14, wherein the resonant tank comprises: an eighth capacitor, the first end of which is coupled to the switch unit; and A transformer has a primary side and a secondary side, wherein the primary side is coupled between the second terminal of the eighth capacitor and a ground terminal, and the secondary side and the fluorescent tube are connected in parallel. 17. The fluorescent tube lighting device according to claim 14, further comprising: a feedback detection unit for detecting the fluorescent tube and generating a feedback signal according to the detection result, wherein the controller adjusts the first pulse width modulation signal and the second pulse width modulation signal according to the feedback signal . 18. The fluorescent tube lighting device according to claim 17, wherein the feedback detection unit comprises: a ninth capacitor, the first end of which is coupled to the fluorescent tube, and the second end of the ninth capacitor is used to provide the feedback signal; and A fourth Zener diode, the cathode of which is coupled to the second terminal of the ninth capacitor, and the anode of the third Zener diode is coupled to a ground terminal. 19. The fluorescent tube lighting device according to claim 14, further comprising: An auxiliary voltage generator generates an auxiliary voltage according to the resonance tank, wherein the switching unit also receives the auxiliary voltage, and transmits the auxiliary voltage according to the power supply signal. 20. The fluorescent tube lighting device according to claim 19, wherein the auxiliary voltage generator comprises: An inductor, which induces the current in the resonance tank, and generates an induced current accordingly; a sixth diode, the anode of which receives the induced current; and A twelfth resistor, the first end of which is coupled to the cathode of the sixth diode, and the second end of the twelfth resistor generates the auxiliary voltage. 21. A method for driving a fluorescent lamp, comprising the following steps: Provide a power supply voltage to an inverter, so that the inverter lights up the fluorescent tube according to a trigger signal and uses a double high voltage method; detecting open-circuit conditions at both ends of the fluorescent tube to generate an open-circuit protection signal; and Deciding whether to shut down the converter according to the open circuit protection signal; also includes: receiving an AC voltage, and converting the AC voltage into a first DC voltage and a second DC voltage; charging with the first DC voltage to generate a charging voltage and the trigger signal; charging with the charging voltage, and generating a power supply signal according to the charging voltage and the open circuit protection signal; and receiving the second direct current voltage, and determining whether to provide the second direct current voltage as the power supply voltage to the converter according to the power supply signal; 22. The driving method of a fluorescent lamp according to claim 21, wherein determining whether to turn off the inverter according to the open circuit protection signal comprises the following steps: After the inverter starts to operate, the inverter pulls down the commutation signal to ground voltage, so as to stop generating the charging voltage and the trigger signal; When the two ends of the fluorescent tube are not open-circuited, continuously enable the open-circuit protection signal, so as to use the open-circuit protection signal for charging, and continuously generate the power supply signal when the charging voltage is stopped; and When the two ends of the fluorescent tube are open-circuited, the open-circuit protection signal is disabled to stop generating the power supply signal. 23. The method for driving a fluorescent lamp according to claim 21, further comprising: When the level of the open circuit protection signal is greater than a rated operating voltage, an overvoltage protection signal is generated; and When the overvoltage protection signal is enabled, the supply voltage to the converter is stopped.