Driver system and method with multi-function protection for cold-cathode fluorescent lamp and external-electrode fluorescent lamp

System and method for driving a cold-cathode fluorescent lamp. The system includes a control subsystem configured to generate one or more control signals, and a power supply subsystem configured to receive the one or more control signals and a DC input voltage, convert the DC input voltage to an AC output voltage, and send the AC output voltage to a cold-cathode fluorescent lamp. If the DC input voltage is lower than a predetermined threshold, the system for driving the cold-cathode fluorescent lamp is turned off in response to the one or more control signals.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority to Chinese Patent Application No.200510102863.0, filed Sep. 13, 2005, commonly assigned, incorporated by reference herein for all purposes.

NOT APPLICABLE

NOT APPLICABLE

BACKGROUND OF THE INVENTION

The present invention is directed to integrated circuits. More particularly, the invention provides a system and method with multi-function protection. Merely by way of example, the invention has been applied to driving one or more cold-cathode fluorescent lamps, and/or one or more external-electrode fluorescent lamps. But it would be recognized that the invention has a much broader range of applicability.

The cold-cathode fluorescent lamp (CCFL) and external-electrode fluorescent lamp (EEFL) have been widely used to provide backlight for a liquid crystal display (LCD) module. The CCFL and EEFL often each require a high alternate current (AC) voltage such as 2 kV for ignition and normal operation. Such a high AC voltage can be provided by a CCFL driver system or an EEFL driver system. The CCFL driver system and the EEFL driver system each receive a low direct current (DC) voltage and convert the low DC voltage to the high AC voltage.

FIG. 1is a simplified conventional driver system for CCFL and/or EEFL. The driver system100includes a control subsystem110and an AC power supply subsystem120. The control subsystem110receives a power supply voltage VDDAand certain control signals. The control signals include an enabling (ENA) signal and a dimming (DIM) signal. In response, the control subsystem110outputs gate drive signals to the AC power supply subsystem120. The AC power supply subsystem120includes MOSFET transistors and power transformers, and receives a low DC voltage VIN. The MOSFET transistors convert the low DC voltage VINto a low AC voltage in response to the gate drive signals. The low AC voltage is boosted to a high AC voltage VOUTby the power transformers, and the high AC voltage VOUTis sent to drive a system190. The system190includes CCFLs and/or EEFLs. The system190provides a current and voltage feedback to the control subsystem110.

As discussed above, the power transformers can boost the AC voltage. The increase in AC voltage is often accomplished by a high turn ratio between the secondary winding and the primary winding. The secondary winding usually is formed by a wire having a small diameter such as 0.05 mm. The wire can easily be damaged by bending in the manufacturing process. For example, a breakpoint may exist at the winding terminal that is connected to pins in the transformer bobbin. If the gap at the breakpoint is small, the high AC voltage can jump through the gap by arcing and still drive the system190including CCFLs and/or EEFLs. But the arcing process can produce a large amount of heat and even a visible fire. Under these conditions, the driver system100should be turned off to prevent any accidents.

FIG. 2is a simplified conventional system for detecting breakpoint in transformer secondary winding. The secondary winding of a transformer T1includes pins5and6. The pin6is biased to the low DC voltage VINthat is different from the ground voltage. Additionally, the DC voltage at the pin5is received by a high impedance voltage divider. As shown inFIG. 2, the voltage divider includes resistors R1and R2and outputs a voltage VDIVto a transistor Q1. If no breakpoint exists in the secondary winding, the voltage VDIVwould be equal to a fraction of VIN. As a result, the transistor Q1is turned on, and the control subsystem110is enabled. If a breakpoint exists in the secondary winding, the voltage VDIVwould be equal to zero. As a result, the transistor Q1is turned off, and the control subsystem110is disabled. The driver system100for CCFL and/or EEFL is thus protected. But the system as shown inFIG. 2often cannot effectively detect breakpoints for multiple transformers.

Hence it is highly desirable to improve protection techniques for CCFL driver system and EEFL driver system.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to integrated circuits. More particularly, the invention provides a system and method with multi-function protection. Merely by way of example, the invention has been applied to driving one or more cold-cathode fluorescent lamps, and/or one or more external-electrode fluorescent lamps. But it would be recognized that the invention has a much broader range of applicability.

According to one embodiment of the present invention, a system for driving a cold-cathode fluorescent lamp is provided. The system includes a control subsystem configured to generate one or more control signals, and a power supply subsystem configured to receive the one or more control signals and a DC input voltage, convert the DC input voltage to an AC output voltage, and send the AC output voltage to a cold-cathode fluorescent lamp. If the DC input voltage is lower than a predetermined threshold, the system for driving the cold-cathode fluorescent lamp is turned off in response to the one or more control signals.

According to another embodiment, a system for driving a cold-cathode fluorescent lamp includes a control subsystem configured to generate one or more control signals, and a power supply subsystem configured to receive the one or more control signals and a DC input voltage, convert the DC input voltage to an AC output voltage, and send the AC output voltage to a cold-cathode fluorescent lamp. If the DC input voltage is higher than a predetermined threshold, the system for driving the cold-cathode fluorescent lamp is turned off in response to the one or more control signals.

According to yet another embodiment, a system for driving a cold-cathode fluorescent lamp includes a control subsystem configured to generate one or more control signals, and a power supply subsystem configured to receive the one or more control signals and a DC input voltage, convert the DC input voltage to an AC output voltage, and send the AC output voltage to a cold-cathode fluorescent lamp. The power supply subsystem includes a transformer including a primary winding and a secondary winding. If the DC input voltage is lower than a first predetermined threshold, the system for driving the cold-cathode fluorescent lamp is turned off in response to the one or more control signals. If the DC input voltage is higher than a second predetermined threshold, the system for driving the cold-cathode fluorescent lamp is turned off in response to the one or more control signals. If the secondary winding includes a breakpoint, the system for driving the cold-cathode fluorescent lamp is turned off in response to the one or more control signals.

According to yet another embodiment, a system for driving a cold-cathode fluorescent lamp includes a control subsystem configured to generate one or more control signals, and a power supply subsystem configured to receive the one or more control signals and a DC input voltage, convert the DC input voltage to an AC output voltage, and send the AC output voltage to a cold-cathode fluorescent lamp. The power supply subsystem includes a first resistor, a second resistor, a first capacitor, and a transformer including a primary winding and a secondary winding. The secondary winding, the first resistor, and the second resistor are in series. The second resistor is located between the first resistor and the secondary winding, and the secondary winding includes a first terminal biased to a ground voltage level. The first resistor includes a second terminal and a third terminal. The second terminal is biased to the DC input voltage, and the third terminal is coupled to the second resistor. The first resistor and the first capacitor are in parallel between the second terminal and the third terminal, and the third terminal is associated with a first detected voltage. The first detected voltage is compared to a first predetermined voltage for determining the one or more control signals.

According to yet another embodiment, a method for driving a cold-cathode fluorescent lamp includes receiving a DC input voltage, determining whether the DC input voltage is lower than a first predetermined threshold or higher than a second predetermined threshold, and generating one or more control signals based on at least information associated with the DC input voltage, the first predetermined threshold, and the second predetermined threshold. Additionally, the method includes receiving the one or more control signals, converting the DC input voltage into an AC output voltage in response to the one or more control signals, and sending the AC output voltage to a cold-cathode fluorescent lamp. If the DC input voltage is lower than the first predetermined threshold, the AC output voltage is substantially equal to zero. If the DC input voltage is higher than the second predetermined threshold, the AC output voltage is substantially equal to zero.

According to yet another embodiment, a system for driving an external-electrode fluorescent lamp includes a control subsystem configured to generate one or more control signals, and a power supply subsystem configured to receive the one or more control signals and a DC input voltage, convert the DC input voltage to an AC output voltage, and send the AC output voltage to an external-electrode fluorescent lamp. If the DC input voltage is lower than a predetermined threshold, the system for driving the external-electrode fluorescent lamp is turned off in response to the one or more control signals.

According to yet another embodiment, a system for driving an external-electrode fluorescent lamp includes a control subsystem configured to generate one or more control signals, and a power supply subsystem configured to receive the one or more control signals and a DC input voltage, convert the DC input voltage to an AC output voltage, and send the AC output voltage to an external-electrode fluorescent lamp. If the DC input voltage is higher than a predetermined threshold, the system for driving the external-electrode fluorescent lamp is turned off in response to the one or more control signals.

According to yet another embodiment, a system for driving an external-electrode fluorescent lamp includes a control subsystem configured to generate one or more control signals, and a power supply subsystem configured to receive the one or more control signals and a DC input voltage, convert the DC input voltage to an AC output voltage, and send the AC output voltage to an external-electrode fluorescent lamp. The power supply subsystem includes a transformer including a primary winding and a secondary winding. If the DC input voltage is lower than a first predetermined threshold, the system for driving the external-electrode fluorescent lamp is turned off in response to the one or more control signals. If the DC input voltage is higher than a second predetermined threshold, the system for driving the external-electrode fluorescent lamp is turned off in response to the one or more control signals. If the secondary winding includes a breakpoint, the system for driving the external-electrode fluorescent lamp is turned off in response to the one or more control signals.

According to yet another embodiment, a system for driving an external-electrode fluorescent lamp includes a control subsystem configured to generate one or more control signals, and a power supply subsystem configured to receive the one or more control signals and a DC input voltage, convert the DC input voltage to an AC output voltage, and send the AC output voltage to an external-electrode fluorescent lamp. The power supply subsystem includes a first resistor, a second resistor, a first capacitor, and a transformer including a primary winding and a secondary winding. The secondary winding, the first resistor, and the second resistor are in series. The second resistor is located between the first resistor and the secondary winding, and the secondary winding includes a first terminal biased to a ground voltage level. The first resistor includes a second terminal and a third terminal. The second terminal is biased to the DC input voltage, and the third terminal is coupled to the second resistor. The first resistor and the first capacitor are in parallel between the second terminal and the third terminal. The third terminal is associated with a first detected voltage, and the first detected voltage is compared to a first predetermined voltage for determining the one or more control signals.

According to yet another embodiment, a method for driving an external-electrode fluorescent lamp includes receiving a DC input voltage, determining whether the DC input voltage is lower than a first predetermined threshold or higher than a second predetermined threshold, and generating one or more control signals based on at least information associated with the DC input voltage, the first predetermined threshold, and the second predetermined threshold. Additionally, the method includes receiving the one or more control signals, converting the DC input voltage into an AC output voltage in response to the one or more control signals, and sending the AC output voltage to an external-electrode fluorescent lamp. If the DC input voltage is lower than the first predetermined threshold, the AC output voltage is substantially equal to zero. If the DC input voltage is higher than the second predetermined threshold, the AC output voltage is substantially equal to zero.

Many benefits are achieved by way of the present invention over conventional techniques. For example, some embodiments of the present invention provide a driver system with one or more protection mechanisms. For example, the driver system is protected against under-voltage system power supply, over-voltage system power supply, and/or breaking of transformer secondary winding. In another example, the driver system is used to drive one or more cold-cathode fluorescent lamps and/or one or more external-electrode fluorescent lamp. Certain embodiments of the present invention provide protection against breaking of a secondary winding. The breaking of the secondary winding can cause arcing, which may damage the secondary winding. Arcing often is difficult to detect during the testing process, so it is very important to protect the driver system when the breaking of the secondary winding occurs. Some embodiments of the present invention provide protection against under-voltage system power supply. Such protection is very important because a low DC input voltage can cause current stress to a power MOSFET transistor. Certain embodiments of the present invention provide protection against over-voltage system power supply. Such protection is very important because a high DC input voltage can cause voltage stress between the drain and source of a power MOSFET transistor. Depending upon the embodiment, one or more of these benefits may be achieved. These and other benefits will be described in more detail throughout the present specification and more particularly below.

Various additional objects, features and advantages of the present invention can be more fully appreciated with reference to the detailed description and the accompanying drawings that follow.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to integrated circuits. More particularly, the invention provides a system and method with multi-function protection. Merely by way of example, the invention has been applied to driving one or more cold-cathode fluorescent lamps, and/or one or more external-electrode fluorescent lamps. But it would be recognized that the invention has a much broader range of applicability.

FIG. 3is a simplified driver system according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. The driver system300includes a control subsystem310and an AC power supply subsystem320. The control subsystem310includes a comparator430, a control logic component440, and a gate drive component450. The AC power supply subsystem320includes resistors410,420,540,545,550,555and640, transistors510,515,520,525and710, transformers530and535, capacitors560,565,570,575and630, and comparators610and620. Although the above has been shown using a selected group of components for the system300, there can be many alternatives, modifications, and variations. For example, some of the components may be expanded and/or combined. Other components may be inserted to those noted above. Depending upon the embodiment, the arrangement of components may be interchanged with others replaced. For example, the system300is used to regulate one or more cold-cathode fluorescent lamps and/or external-electrode fluorescent lamps. Further details of these components are found throughout the present specification and more particularly below.

The control subsystem310receives a power supply voltage VDDAand certain control signals. For example, the power supply voltage VDDAis equal to 5 volts. In another example, the control signals include an enabling (ENA) signal and a dimming (DIM) signal. The control subsystem310outputs gate drive signals312and314to the AC power supply subsystem320. Additionally, the AC power supply subsystem320receives a DC voltage VINand generates AC voltages VOUT1and VOUT2. For example, the DC voltage VINis equal to 12 volts. In another example, the peak-to-peak amplitude for each of the AC voltages VOUT1and VOUT2ranges from several hundred volts to several thousand volts. In yet another example, the AC voltages VOUT1and VOUT2are sent to drive cold-cathode fluorescent lamps and/or external-electrode fluorescent lamps.

FIG. 4is a simplified subsystem for protecting the driver system300according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. The subsystem400includes the comparator430, the control logic component440, the gate drive component450, and the resistors410and420. Although the above has been shown using a selected group of components for the subsystem400, there can be many alternatives, modifications, and variations. For example, some of the components may be expanded and/or combined. Other components may be inserted to those noted above. Depending upon the embodiment, the arrangement of components may be interchanged with others replaced. For example, the subsystem400is used to protect the driver system300for one or more cold-cathode fluorescent lamps and/or one or more external-electrode fluorescent lamps. Further details of these components are found throughout the present specification and more particularly below.

The comparator430, the control logic component440, and the gate drive component450are parts of the control subsystem310. Additionally, the resistors410and420are parts of the AC power supply subsystem320. The resistor410has resistance R1, and the resistor420has resistance R2. The resistors410and420are connected in series through a node411to form a voltage divider and coupled between the ground voltage and the DC voltage VIN. The comparator430includes input terminals431and432and an output terminal433. The input terminal431is biased to a predetermined reference voltage VREF, and the input terminal432is biased to a detected voltage VDET, which is the voltage potential at the node411. The comparator430compares the reference voltage VREFand the detected voltage VDET, and in response outputs a comparison signal to the control signal component440. Based on at least the comparison signal, the control logic component440provides a control signal to the gate drive component450, which in response can turn on or off the driver system300.

In one embodiment, if the comparison signal indicates the detected voltage VDETis lower than the reference voltage VREF, the control signal from the control logic component440instructs the gate drive component450to turn off the driver system300. For example,

Hence the driver system300is turned off if VINis lower than a threshold voltage that is equal to

FIGS. 5,6, and7are simplified diagrams showing a subsystem for protecting the driver system300according to another embodiment of the present invention. These diagrams are merely examples, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. The subsystem500includes the comparators430and610, the control logic component440, the gate drive component450, the resistors540,550and640, the transistors510,520and710, the transformer530, and the capacitors560and630. Although the above has been shown using a selected group of components for the subsystem500, there can be many alternatives, modifications, and variations. For example, some of the components may be expanded and/or combined. Other components may be inserted to those noted above. Depending upon the embodiment, the arrangement of components may be interchanged with others replaced. For example, the subsystem500is used to protect the driver system300for one or more cold-cathode fluorescent lamps and/or one or more external-electrode fluorescent lamps. Further details of these components are found throughout the present specification and more particularly below.

The comparator430, the control logic component440, and the gate drive component450are parts of the control subsystem310. Additionally, the comparator610, the resistors540,550and640, the transistors510,520and710, the transformer530, and the capacitors560and630are parts of the AC power supply subsystem320. As shown inFIG. 5, the transformer530includes a primary winding531and a secondary winding532. The secondary winding532has resistance Rsecondary, the resistor540has resistance R11, and the resistor550has resistance R12. The resistors540and550and the secondary winding532are connected in series and coupled between the ground voltage and the DC voltage VIN. Additionally, the resistor540and the capacitor560are in parallel between nodes541and542. At the node542, the voltage potential is equal to a detected voltage V1.

In one embodiment, an AC voltage exists at pin7of the transformer531. For example, the AC voltage has a frequency of 50 kHz. The AC voltage is filtered out by the resistors540and550and the capacitor560. For example, the capacitor560provides low impedance to the AC voltage. In another example, the capacitor560has a capacitance value of 27 nF. Accordingly, the AC component can be ignored for the detected voltage V1, and the detected voltage V1is determined as follows:

As shown inFIG. 6, the comparator610includes input terminals611and612and an output terminal613. The input terminal611is biased to a predetermined reference voltage V0, and the input terminal612is biased to the detected voltage V1. The comparator610compares the reference voltage V0and the detected voltage V1, and in response generates a comparison signal at the output terminal613. For example, the reference voltage V0is equal to 5 volts. In another example, the comparison signal is at the logic low level if the detected voltage V1is higher than the reference voltage V0. In yet another example, the comparison signal614is at the logic high level if the detected voltage V1is lower than the reference voltage V0.

In another embodiment, the subsystem500includes another comparator620. The comparator620includes input terminals621and622and an output terminal623. The input terminal621is biased to the predetermined reference voltage V0, and the input terminal622is biased to another detected voltage V2. The comparator620compares the reference voltage V0and the detected voltage V2, and in response outputs a comparison signal at the output terminal623. For example, the reference voltage V0is equal to 5 volts. In another example, the comparison signal is at the logic low level if the detected voltage V1is higher than the reference voltage V0. In yet another example, the comparison signal is at the logic high level if the detected voltage V1is lower than the reference voltage V0.

As shown inFIG. 6, the output terminals613and623are directly connected at a node631. The node631is coupled to a node641through the resistor640, and is coupled to the ground voltage level through the capacitor630. For example, the resistor640has a resistance value of 10 kΩ. In another example, the capacitor630has a capacitance value of 100 pF. At the node631, a signal614is outputted to the transistor710. For example, the signal614is at the logic high level only if both the comparison signals at the output terminals613and623are at the logic high level. In another example, the signal614is at the logic low level if at least one of the comparison signals at the output terminals613and623is at the logic low level.

As shown inFIG. 7, the signal614is used to turn on or off the transistor710. The transistor701serves as a switch. For example, the transistor710is closed or turned on if the signal614is at the logic low level. Hence, the input terminal432is biased to substantially the ground voltage level, which is lower than the reference voltage VREF. In another example, the transistor710is open or turned off if the signal614is at the logic high level. Hence the input terminal432is biased to the voltage at the node411as discussed above forFIG. 4.

The comparator430compares the voltage level at the input terminal432and the reference voltage VREFat the input terminal431, and in response outputs the comparison signal to the control signal component440. Based on at least the comparison signal, the control logic component440provides a control signal to the gate drive component450, which in response can turn on or off the driver system300. In one embodiment, if the comparison signal indicates the voltage level at the input terminal432is lower than the reference voltage VREF, the control signal from the control logic component440instructs the gate drive component450to turn off the driver system300.

As discussed above, the detected voltage V1can be determined according to Equation 4. In one embodiment,

Hence the comparison signal at the output terminal613is at the logic low level if VINis larger than a threshold voltage that is equal to

R11+R12+RsecondaryR12+Rsecondary×V0.
For example, R11equals 13 MΩ, R12equals 6.2 MΩ, Rsecondaryequals 600 Ω, and V0equals 5 volts, so the threshold voltage is equal to about 15.5 volts. If VINis higher than 15.5 volts, the comparison signal at the output terminal613is at the logic low level. If the comparison signal at the output terminal613is at the logic low level, the signal614is also at the logic low level. Hence, the driver system300is turned off if VINis larger than the threshold voltage.

In another embodiment, the secondary winding532includes one or more breakpoints, so Rsecondaryof the secondary winding532becomes very large. Accordingly, the detected voltage V1is substantially equal to the DC voltage VINas follows:

For example, the DC voltage VINis higher than the reference voltage V0. Accordingly, the detected voltage V1is also higher than the reference voltage V0based on Equation 7. In another example, the DC voltage VINis equal to 12 volts, and the reference voltage V0is equal to 5 volts. Hence the comparison signal at the output terminal613is at the logic low level, and the signal614is also at the logic low level. Accordingly, the driver system300is turned off if the secondary winding532includes one or more breakpoints.

Returning toFIG. 3, the control subsystem310outputs the gate drive signals312and314to the AC power supply subsystem320. The control subsystem310includes the gate drive component450, and the AC power supply subsystem320includes the transistors510and520. The gate drive signals312and314are generated by the gate drive component450and received by the transistors520and510respectively. The transistors510and520are coupled to the primary winding531of the transformer530. Additionally, the secondary winding532of the transformer530is coupled to a terminal571of the capacitor570. Another terminal572of the capacitor570provides the AC voltage VOUT1. The gate drive signals312and314turns on or off the driver system300by controlling the AC voltage VOUT1.

The driver system300includes the transformers530and535. The transformer530is associated with the transistors510and520, the resistors540and550, the capacitors560and570, and the comparator610. The transformer535is associated with the transistors515and525, the resistors545and555, the capacitors565and575, and the comparator620. For example, the arrangement and operation principle for the transformer535, the transistors515and525, the resistors545and555, the capacitors565and575, and the comparator620are substantially the same as the arrangement and operation principle for the transformer530, the transistors510and520, the resistors540and550, the capacitors560and570, and the comparator610. In another example, the transformer530is used to generate the AC voltage VOUT1, and the transformer535is used to generate the AC voltage VOUT2. The AC voltages VOUT1and VOUT2can be the same or different.

As discussed above and further emphasized here,FIGS. 3-7are merely examples, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. For example, one of the transformers530and535and certain associated components are removed. In another example, one or more additional transformers and some associated components are added to generate one or more additional AC voltages. As discussed above, the driver system300includes three protection mechanisms. Specifically, the driver system300is turned off if the DC voltage VINis lower than a threshold voltage, if the DC voltage VINis larger than a threshold voltage, or if the secondary winding of anyone of the transformers530and535includes one or more breakpoints. In one embodiment, the driver system300is modified so that one of these three protection mechanisms is removed. In another embodiment, the driver system300is modified so that two of these three protection mechanisms are removed.

According to another embodiment of the present invention, a system for driving a cold-cathode fluorescent lamp includes a control subsystem configured to generate one or more control signals, and a power supply subsystem configured to receive the one or more control signals and a DC input voltage, convert the DC input voltage to an AC output voltage, and send the AC output voltage to a cold-cathode fluorescent lamp. If the DC input voltage is lower than a predetermined threshold, the system for driving the cold-cathode fluorescent lamp is turned off in response to the one or more control signals. For example, the system is implemented according to the system300including the subsystem400.

According to another embodiment, a system for driving a cold-cathode fluorescent lamp includes a control subsystem configured to generate one or more control signals, and a power supply subsystem configured to receive the one or more control signals and a DC input voltage, convert the DC input voltage to an AC output voltage, and send the AC output voltage to a cold-cathode fluorescent lamp. If the DC input voltage is higher than a predetermined threshold, the system for driving the cold-cathode fluorescent lamp is turned off in response to the one or more control signals. For example, the system is implemented according to the system300including the subsystem500.

According to yet another embodiment, a system for driving a cold-cathode fluorescent lamp includes a control subsystem configured to generate one or more control signals, and a power supply subsystem configured to receive the one or more control signals and a DC input voltage, convert the DC input voltage to an AC output voltage, and send the AC output voltage to a cold-cathode fluorescent lamp. The power supply subsystem includes a transformer including a primary winding and a secondary winding. If the DC input voltage is lower than a first predetermined threshold, the system for driving the cold-cathode fluorescent lamp is turned off in response to the one or more control signals. If the DC input voltage is higher than a second predetermined threshold, the system for driving the cold-cathode fluorescent lamp is turned off in response to the one or more control signals. If the secondary winding includes a breakpoint, the system for driving the cold-cathode fluorescent lamp is turned off in response to the one or more control signals. For example, the system is implemented according to the system300including the subsystem400and the subsystem500.

According to yet another embodiment, a system for driving a cold-cathode fluorescent lamp includes a control subsystem configured to generate one or more control signals, and a power supply subsystem configured to receive the one or more control signals and a DC input voltage, convert the DC input voltage to an AC output voltage, and send the AC output voltage to a cold-cathode fluorescent lamp. The power supply subsystem includes a first resistor, a second resistor, a first capacitor, and a transformer including a primary winding and a secondary winding. The secondary winding, the first resistor, and the second resistor are in series. The second resistor is located between the first resistor and the secondary winding, and the secondary winding includes a first terminal biased to a ground voltage level. The first resistor includes a second terminal and a third terminal. The second terminal is biased to the DC input voltage, and the third terminal is coupled to the second resistor. The first resistor and the first capacitor are in parallel between the second terminal and the third terminal, and the third terminal is associated with a first detected voltage. The first detected voltage is compared to a first predetermined voltage for determining the one or more control signals. For example, the system is implemented according to the system300including the subsystem500.

According to yet another embodiment, a method for driving a cold-cathode fluorescent lamp includes receiving a DC input voltage, determining whether the DC input voltage is lower than a first predetermined threshold or higher than a second predetermined threshold, and generating one or more control signals based on at least information associated with the DC input voltage, the first predetermined threshold, and the second predetermined threshold. Additionally, the method includes receiving the one or more control signals, converting the DC input voltage into an AC output voltage in response to the one or more control signals, and sending the AC output voltage to a cold-cathode fluorescent lamp. If the DC input voltage is lower than the first predetermined threshold, the AC output voltage is substantially equal to zero. If the DC input voltage is higher than the second predetermined threshold, the AC output voltage is substantially equal to zero. For example, the converting the DC input voltage into an AC output voltage is performed by at least a transformer. The transformer includes a primary winding and a secondary winding. Additionally, the method includes determining whether the secondary winding includes a breakpoint. If the secondary winding includes a breakpoint, the AC output voltage is substantially equal to zero. In another example, the method is performed by the system300including the subsystem400and the subsystem500.

According to yet another embodiment, a system for driving an external-electrode fluorescent lamp includes a control subsystem configured to generate one or more control signals, and a power supply subsystem configured to receive the one or more control signals and a DC input voltage, convert the DC input voltage to an AC output voltage, and send the AC output voltage to an external-electrode fluorescent lamp. If the DC input voltage is lower than a predetermined threshold, the system for driving the external-electrode fluorescent lamp is turned off in response to the one or more control signals. For example, the system is implemented according to the system300including the subsystem400.

According to yet another embodiment, a system for driving an external-electrode fluorescent lamp includes a control subsystem configured to generate one or more control signals, and a power supply subsystem configured to receive the one or more control signals and a DC input voltage, convert the DC input voltage to an AC output voltage, and send the AC output voltage to an external-electrode fluorescent lamp. If the DC input voltage is higher than a predetermined threshold, the system for driving the external-electrode fluorescent lamp is turned off in response to the one or more control signals. For example, the system is implemented according to the system300including the subsystem500.

According to yet another embodiment, a system for driving an external-electrode fluorescent lamp includes a control subsystem configured to generate one or more control signals, and a power supply subsystem configured to receive the one or more control signals and a DC input voltage, convert the DC input voltage to an AC output voltage, and send the AC output voltage to an external-electrode fluorescent lamp. The power supply subsystem includes a transformer including a primary winding and a secondary winding. If the DC input voltage is lower than a first predetermined threshold, the system for driving the external-electrode fluorescent lamp is turned off in response to the one or more control signals. If the DC input voltage is higher than a second predetermined threshold, the system for driving the external-electrode fluorescent lamp is turned off in response to the one or more control signals. If the secondary winding includes a breakpoint, the system for driving the external-electrode fluorescent lamp is turned off in response to the one or more control signals. For example, the system is implemented according to the system300including the subsystem400and the subsystem500.

According to yet another embodiment, a system for driving an external-electrode fluorescent lamp includes a control subsystem configured to generate one or more control signals, and a power supply subsystem configured to receive the one or more control signals and a DC input voltage, convert the DC input voltage to an AC output voltage, and send the AC output voltage to an external-electrode fluorescent lamp. The power supply subsystem includes a first resistor, a second resistor, a first capacitor, and a transformer including a primary winding and a secondary winding. The secondary winding, the first resistor, and the second resistor are in series. The second resistor is located between the first resistor and the secondary winding, and the secondary winding includes a first terminal biased to a ground voltage level. The first resistor includes a second terminal and a third terminal. The second terminal is biased to the DC input voltage, and the third terminal is coupled to the second resistor. The first resistor and the first capacitor are in parallel between the second terminal and the third terminal. The third terminal is associated with a first detected voltage, and the first detected voltage is compared to a first predetermined voltage for determining the one or more control signals. For example, the system is implemented according to the system300including the subsystem500.

According to yet another embodiment, a method for driving an external-electrode fluorescent lamp includes receiving a DC input voltage, determining whether the DC input voltage is lower than a first predetermined threshold or higher than a second predetermined threshold, and generating one or more control signals based on at least information associated with the DC input voltage, the first predetermined threshold, and the second predetermined threshold. Additionally, the method includes receiving the one or more control signals, converting the DC input voltage into an AC output voltage in response to the one or more control signals, and sending the AC output voltage to an external-electrode fluorescent lamp. If the DC input voltage is lower than the first predetermined threshold, the AC output voltage is substantially equal to zero. If the DC input voltage is higher than the second predetermined threshold, the AC output voltage is substantially equal to zero. For example, the converting the DC input voltage into an AC output voltage is performed by at least a transformer. The transformer includes a primary winding and a secondary winding. Additionally, the method includes determining whether the secondary winding includes a breakpoint. If the secondary winding includes a breakpoint, the AC output voltage is substantially equal to zero. In another example, the method is performed by the system300including the subsystem400and the subsystem500.

The present invention has various advantages. Some embodiments of the present invention provide a driver system with one or more protection mechanisms. For example, the driver system is protected against under-voltage system power supply, over-voltage system power supply, and/or breaking of transformer secondary winding. In another example, the driver system is used to drive one or more cold-cathode fluorescent lamps and/or one or more external-electrode fluorescent lamps. Certain embodiments of the present invention provide protection against breaking of a secondary winding. The breaking of the secondary winding can cause arcing, which may damage the secondary winding. Arcing often is difficult to detect during the testing process, so it is very important to protect the driver system when the breaking of the secondary winding occurs. Some embodiments of the present invention provide protection against under-voltage system power supply. Such protection is very important because a low DC input voltage can cause current stress to a power MOSFET transistor. Certain embodiments of the present invention provide protection against over-voltage system power supply. Such protection is very important because a high DC input voltage can cause voltage stress between the drain and source of a power MOSFET transistor.