Light tube apparatus

The present application is related to a light tube apparatus and more particularly related to a light tube apparatus with safety design.

Electroluminescence, an optical and electrical phenomenon, was discover in 1907. Electroluminescence refers the process when a material emits light when a passage of an electric field or current occurs. LED stands for light-emitting diode. The very first LED was reported being created in 1927 by a Russian inventor. During decades' development, the first practical LED was found in 1961, and was issued patent by the U.S. patent office in 1962. In the second half of 1962, the first commercial LED product emitting low-intensity infrared light was introduced. The first visible-spectrum LED, which limited to red, was then developed in 1962.

After the invention of LEDs, the neon indicator and incandescent lamps are gradually replaced. However, the cost of initial commercial LEDs was extremely high, making them rare to be applied for practical use. Also, LEDs only illuminated red light at early stage. The brightness of the light only could be used as indicator for it was too dark to illuminate an area. Unlike modern LEDs which are bound in transparent plastic cases, LEDs in early stage were packed in metal cases.

With high light output, LEDs are available across the visible, infrared wavelengths, and ultraviolet lighting fixtures. Recently, there is a high-output white light LED. And this kind of high-output white light LEDs are suitable for room and outdoor area lighting. Having led to new displays and sensors, LEDs are now be used in advertising, traffic signals, medical devices, camera flashes, lighted wallpaper, aviation lighting, horticultural grow lights, and automotive headlamps. Also, they are used in cellphones to show messages.

A Fluorescent lamp refers to a gas-discharge lamps. The invention of fluorescent lamps, which are also called fluorescent tubes, can be traced back to hundreds of years ago. Being invented by Thomas Edison in 1896, fluorescent lamps used calcium tungstate as the substance to fluoresce then. In 1939, they were firstly introduced to the market as commercial products with variety of types.

In a fluorescent lamp tube, there is a mix of mercury vapor, xenon, argon, and neon, or krypton. A fluorescent coating coats on the inner wall of the lamp. The fluorescent coating is made of blends of rare-earth phosphor and metallic salts. Normally, the electrodes of the lamp comprise coiled tungsten. The electrodes are also coated with strontium, calcium oxides and barium. An internal opaque reflector can be found in some fluorescent lamps. Normally, the shape of the light tubes is straight. Sometimes, the light tubes are made circle for special usages. Also, u-shaped tubes are seen to provide light for more compact areas.

Because there is mercury in fluorescent lamps, it is likely that the mercury contaminates the environment after the lamps are broken. Electromagnetic ballasts in fluorescent lamps are capable of producing buzzing mouse. Radio frequency interference is likely to be made by old fluorescent lamps. The operation of fluorescent lamps requires specific temperature, which is best around room temperature. If the lamps are placed in places with too low or high temperature, the efficacy of the lamps decreases.

In real lighting device design, details are critical no matter how small they appear. For example, to fix two components together conveniently usually brings large technical effect in the field of light device particularly when any such design involves a very large number of products to be sold around the world.

In some embodiments, a light tube apparatus includes a tubular housing, a LED module, an EMI circuit, a rectifier circuit, a filter circuit, a conversion circuit, a safety circuit, and a PWM modulation circuit.

The LED module is enclosed by the tubular housing and emitting a light passing through the tubular housing.

The EMI circuit is used for anti-interference of an alternating current signal from a power source. The rectifier circuit is connected with the EMI circuit for rectifying the alternating current signal to generate a direct current signal. The filter circuit is used for filtering the direct current signal.

The conversion circuit is used for converting a voltage of the direct current signal to drive the LED module. The safety circuit is connected to a dimming signal from a dimmer for preventing an incorrect connection when the dimmer is connected in wrong direction causing loop breakage.

The PWM modulation circuit connected to the conversion circuit and the safety circuit for performing a pulse width modulation for the dimming signal supplied to the conversion circuit for adjusting a luminance level of the LED module.

In some embodiments, the EMI circuit includes a first inductor col, a second inductor coil and a voltage sensitive resistor, a first end of the voltage sensitive resistor and a first stage input of the first inductor coil are connected to a positive terminal of the power source, a second end of the voltage sensitive resistor and a second stage input of the first inductor coil are connected to a negative terminal of the power source, a first stage output of the first inductor is connected to a first stage input of the second inductor coil, a first stage output of the second inductor coil and a second stage output of the second inductor coil are used as output ends of the EMI circuit.

In some embodiments, the rectifier circuit includes a rectifier bridge.

In some embodiments, the filter circuit includes a second capacitor, a third resistor and a third inductor, a first end of the second capacitor and a first end of the third resistor are connected to a first end of the third inductor as an input of the filter circuit, a second end of the second capacitor is grounded, a second end of the third resistor is connected to a second end of the third inductor as an output of the filter circuit.

In some embodiments, the PWM modulation circuit includes a PWM chip, an optical coupler, a third Zener diode, a sixth diode, a twenty-eighth resistor, a first divider resistor, a second divider resistor, a third divider resistor, a fourth divider resistor, a fifth divider resistor, a sixth divider resistor, a seventh divider resistor, a first filter capacitor, a second filter capacitor, a third filter capacitor and a fourth filter capacitor, wherein an input of a light source of the optical coupler is connected to a negative end of the third Zener diode and a first end of the twenty-eighth resistor used as an input of the PWM modulation circuit, an output of a light source of optical coupler and a positive end of the third Zener diode are grounded, a second end of the twenty-eighth resistor is connected to a negative end of the sixth diode, a positive end of the sixth diode is connected to a reference voltage, an input end of a light receiver of the optical coupler is connected to a first end of the sixth divider resistor, a second end of the sixth divider resistor is connected to a first serial port of the PWM chip, a first end of the first divider resistor and a first end of the seventh divider resistor are connected to a management end of the PWM chip, a second end of the first divider resistor is connected to a first end of the second divider resistor, a first end of the fourth filter capacitor is connected to a comparison end of the PMW chip, a first end of the first filter capacitor is connected to voltage regulator end of the PWM chip, a second end of the seventh divider resistor and a first end of the third divider resistor are connected to an empty end of the PMW chip a first end of the fourth divider resistor and a first end of the second filter capacitor are connected to an input end of the PWM chip, a first end of the fifth divider resistor and a first end of the third filter capacitor are connected to a second serial port of the PWM chip, a second end of the fifth divider resistor is used as an output end of the PMW chip, a second end of the fourth filter capacitor, a second end of the second divider resistor, a second end of the first filter capacitor, a second end of the third divider resistor, a second end of the second filter capacitor and a second end of the third filter capacitor are grounded

In some embodiments, the safety circuit includes a tenth diode, a transient voltage suppressor diode and a thermal resistor, a positive terminal of the tenth diode is used as an input of the safety circuit, a negative terminal of the tenth diode is connected to a first end of the transient voltage suppressor diode and a first end of the thermal resistor, a second end of the thermal resistor is used as an output of the safety circuit, a second end of the transient voltage suppressor diode is grounded.

In some embodiments, the light tube apparatus may also include a first end cap and a second end cap, wherein the EMI circuit, the rectifier circuit, the filter circuit and the safety circuit are placed in at least one of the first end cap and the second end cap, the first end cap and the second end cap are disposed at two opposite ends of the tubular housing.

In some embodiments, the light tube apparatus may also include a second power circuit and a power terminal, wherein the first end cap and the second end cap are detachably removable, when the first end cap and the second end cap are removed from the tubular housing, the second power circuit supplies electricity to the LED module.

In some embodiments, the power terminal receives a direct current source.

In some embodiments, the power terminal is connected to another light tube apparatus for receiving the direct current source.

In some embodiments, the power terminal also receives a control command from the another light tube, the second power circuit controls the LED module according to the control command.

In some embodiments, the second power circuit converts a alternating current to a direct current to drive the light source module.

In some embodiments, the light tube apparatus may also include a wireless circuit connected to the safety circuit and the conversion circuit, the wireless circuit is disconnected from the conversion circuit unless the safety circuit indicates a correct connection is done.

In some embodiments, the safety circuit includes a timer for waiting a predetermined time period before indicating the correct connection is done.

In some embodiments, the safety circuit executes a test operation for a predetermined time period before enabling the conversion circuit.

In some embodiments, the safety circuit triggers an alarm message to inform users the incorrect connection.

In some embodiments, the safety circuit sends the alarm message transmitted to a speaker to inform the users.

In some embodiments, the safety circuit shows the alarm message with an indicator.

In some embodiments, the indicator is a LED chip of the LED module.

In some embodiments, the safety circuit is connected to a fuse to turn off the conversion circuit.

FIG. 1 illustrates a structure diagram of an embodiment.

FIG. 2 illustrates a circuit diagram example for an embodiment.

FIG. 3 illustrates a connection example.

FIG. 4 illustrates another connection example.

FIG. 5A and FIG. 5B shows another embodiment.

FIG. 6 illustrates another way to use the embodiment.

FIG. 7 illustrates another embodiment circuit diagram.

Some standard LED light tubes need to be connected under regular indoor power source to work normally. If DIM+, DIM− of dimming ends of low voltage are connected to L, N lines of high voltage alternating current, LED light tubes are damaged and fail to work normally.

In the following embodiments, a LED light tube has circuits for performing following processing on an alternating current signal form a power source. Anti-interference, rectifying, filtering, voltage conversion and pulse width modulation are handled before a direct current is supplied to drive a LED light source. When a dimmer is incorrectly connected, a safety circuit breaks the loop for protecting the LED light tube. Therefore, when the connection is corrected, the LED light tube is able to function normally, instead of being damaged and fail to work.

FIG. 1 shows a structure diagram showing an embodiment with misconnection prevention.

The LED light tube includes an EMI (Electro-Magnetic Interference) circuit 101 , a rectifying circuit 102 , a filtering circuit 103 , a conversion circuit 104 , a PWM modulation circuit 105 and a safety circuit 106 .

The EMI circuit 101 is connected to a power source 100 for anti-interference processing to an alternating current signal from the power source 100 .

The rectifying circuit 102 is connected to the EMI circuit 101 for rectifying the alternating current signal for generating a direct current signal.

The filter circuit 103 is connected to the rectifying circuit 102 for filtering the direct current signal.

The conversion circuit 104 is connected to the filter circuit 103 for voltage conversion on the filtered direct current signal.

The safety circuit 106 is used for receiving a dimming signal from a dimmer and causes a loop breakage to shut down the electric loop.

The PWM modulation circuit 105 is connected to the conversion circuit 104 and the safety circuit 106 for pulse modulation on the dimming signal supplied to the conversion circuit 104 to adjust a luminance level of the LED light source.

FIG. 2 shows an exemplary circuit with safety design. For brevity, only portions related to the embodiments related to claimed inventions

The EMI circuit 101 includes a first inductor coil L 1 , a second inductor coil L 2 and a voltage sensitive resistor RV 1 .

A first end of the voltage sensitive resistor RV 1 and a first stage input of the first inductor coil L 1 are connected to a positive end of the power source.

A second end of the voltage sensitive resistor RV 1 and a second stage input of the first inductor coil L 1 are connected to a negative end of the power source.

The first stage output of the first inductor coil L 1 is connected a first stage input of the second inductor coil L 2 . The second stage output of the first inductor coil L 1 is connected to a second stage input of the second inductor coil L 2 . The first stage output of the second inductor coil L 2 and the second stage output of the second inductor coil L 2 are used as an output end of the EMI circuit 101 .

In some embodiments, the rectifying circuit 102 includes rectifying bridge BD 1 .

In some embodiments, the filtering circuit 103 includes a second capacitor C 2 , a third resistor R 3 and a third inductor L 3 .

A first end of the second capacitor C 2 , a first end of the third resistor and a first end of the third inductor L 3 are connected as an input of the filter circuit 103 . The

A second end of the second capacitor C 2 is grounded. A second end of the third resistor R 3 is connected to a second end of the third inductor L 3 as an output of the filter circuit 103 .

In some embodiments, the conversion circuit 104 includes a transformer TR 1 , a transformer chip U 1 , a fourth inductor coil L 4 , a first transistor Q 1 , a second transistor Q 2 , a third transistor QG 1 , a first Zener diode ZD 1 , a second Zener diode ZDg 1 , a first diode D 01 , a second diode D 2 , a third diode D 3 , a fourth diode D 4 , a fifth diode D 5 , a first energy saving capacitor C 01 , a second energy saving capacitor C 02 , a third energy saving capacitor C 03 , a fourth energy saving capacitor C 03 , a fourth energy saving capacitor CG 2 , a third capacitor C 3 , a sixth capacitor C 6 , a seventh capacitor C 7 , an eighth capacitor C 8 , a ninth capacitor C 9 , a tenth capacitor C 10 , an eleventh capacitor C 11 , a twelfth capacitor C 12 , a thirteen capacitor C 13 , a fourteenth capacitor C 14 , a fifteenth capacitor C 15 , a current limit resistor R 01 , a second current limit resistor R 02 , a third current limit resistor R 03 , a seventh resistor R 7 , an eighth resistor R 08 , a ninth resistor R 9 , a tenth resistor R 10 , an eleven resistor R 11 , a twelfth resistor R 12 , a thirteenth resistor R 13 , a fourteenth resistor R 14 , a fifteenth resistor R 15 , a sixteenth resistor R 16 , a seventeenth resistor R 17 , an eighteenth resistor R 18 , a nineteenth resistor R 19 , a twentieth resistor R 20 , a twenty-first resistor R 21 , a twenty-second resistor R 22 , a twenty-third resistor R 23 , a twenty-fourth resistor R 24 , a twenty-fifth resistor R 25 , a twenty-sixth resistor R 26 , a twenty-seventh resistor R 27 , a twenty-ninth resistor R 29 , a thirty-first resistor R 31 , a thirty-sixth resistor R 36 and a fourth current limit resistor RG 2 .

A first end of the seventh resistor R 7 , a first end of the ninth resistor R 9 , a first end of the third capacitor C 3 , a first end of the twelfth resistor R 12 , a first end of the thirteenth resistor R 13 , a first end of the fourteenth resistor R 14 and a first end of the sixth capacitor C 6 are connected together and are connected an input of a first stage coil of the transformer TR 1 ,

A second end of the ninth resistor R 9 is connected to a first end of the tenth resistor R 10 . A second end of the tenth resistor R 10 , a first end of the eleventh resistor R 11 , a first end of the seventh capacitor C 7 , a first end of the fifteenth capacitor C 15 and a negative end of the second diode D 2 are connected together and are connected to an input end VIN of the transformer chip U 1 .

A positive end of the second diode D 2 is connected to an output end of the second transistor Q 2 . A control end of the second transistor Q 2 is connected to a first end of the fifth resistor R 15 and a negative end of the Zener diode ZD 1 .

An input end of the second transistor Q 2 , a second end of the fifth resistor R 15 , a first end of the eighth capacitor C 8 and a negative end of the third diode D 3 are connected. A positive end of the third diode D 3 is connected to a first end of the sixteenth resistor R 16 .

A second end of the sixteenth resistor R 16 is connected to a first end of the seventeenth resistor R 17 . A second end of the twelfth resistor R 12 , a second end of the thirteenth resistor R 13 , a second end of the fourteenth resistor R 14 , a second end of the sixth capacitor C 6 and a negative end of the fifth diode D 5 are connected together.

A second end of the seventh capacitor C 7 , a second end of the fifteenth capacitor C 15 , a positive end of the first Zener diode ZD 1 , a second end of the eighth capacitor C 8 and a second end of third capacitor C 3 are grounded.

A positive end of the fifth diode D 5 is connected to an output end of the first transistor Q 1 . The control end of the first transistor Q 1 , a positive end of the fourth diode D 4 , a first end of the nineteenth resistor R 19 and a first end of the twenty-first resistor R 21 are connected together.

A negative end of the fourth diode D 4 is connected to a first end of the eighteenth resistor R 18 . A second end of the eighteenth resistor R 18 , a second end of the nineteenth resistor R 19 and output DRV of the transformer chip U 1 are connected together.

A second end of the seventeenth resistor R 17 , a first end of the twenty-second resistor R 22 and a first end of the fourteenth capacitor C 14 are connected together and are connected to a detection end ZCS of the transformer chip U 1 .

An input end of the first transistor Q 1 , a second end of the twenty-first resistor R 21 , a first end of the twentieth resistor R 20 , a first end of the twenty-third resistor R 23 , a first end of the twenty-fifth resistor R 25 and a first end of the twenty-sixth resistor R 26 are connected together. A second end of the eleventh resistor R 11 , a first end of the twenty-ninth resistor R 29 and a first end of the tenth capacitor C 10 and are connected to a PWM pulse input end of the transformer chip U 1 . A second end of the twenty-ninth resistor R 29 is used as an output end of the conversion circuit. A second end of the seventh resistor R 7 is connected to a first end of the eighth resistor R 8 .

A second end of the eighth resistor R 8 , a first end of the thirty-sixth resistor R 36 and a first end of the ninth capacitor C 9 are connected. A second end of the thirty-sixth resistor R 36 , a first end of the twelfth capacitor C 12 and a first end of the twenty-seventh resistor R 27 are connected together.

A second end of the twelfth capacitor C 12 , a second end of the thirteenth capacitor C 13 and a serial port COM of the transformer chip U 1 are connected. A first end of the eleventh capacitor C 11 , a first end of the sixth capacitor C 16 and a feedback capacitor end CF of the transformer chip U 1 .

A second end of the sixteenth capacitor C 16 is connected to a first end of the thirty-first resistor R 31 . A second end of the ninth capacitor C 9 , a second end of the tenth capacitor C 10 , a second end of the eleventh capacitor C 11 , a second end of the thirty-first resistor R 31 , a second end of the twenty-seventh resistor R 27 , a second end of the thirteenth capacitor C 13 , a second end of the twenty-second resistor R 22 , a second end of the fourteenth capacitor C 14 , a second end of the twenty-third resistor R 23 , a second end of the twenty-fourth resistor R 24 , a second end of the twenty-fifth resistor R 25 and a second end of the twenty-sixth resistor R 26 are grounded.

A first end of the first current limit resistor R 01 , a first end of the second current limit resistor R 02 and a positive end of the first diode D 01 are connected. A second end of the first current limit resistor R 01 , a second end of the second current limit resistor R 02 and a first end of the first energy saving capacitor C 01 are connected.

A second end of the first energy saving capacitor C 01 , a negative end of the first diode D 01 , a first end of the second energy saving capacitor C 02 , a first end of the third energy saving capacitor C 03 , a first end of the third current limit resistor R 03 , an input end of the third transistor QG 1 and a first end of the fourth current limit resistor RG 2 are connected and are connected to a first stage input of the fourth inductor coil L 4 .

A second end of the second energy saving capacitor C 02 , a second end of the third energy saving capacitor C 03 and a second end of the third current limit resistor R 03 are connected and are connected to a second stage end of the fourth inductor coil L 4 .

An output end of the third transistor QG 1 is connected to a first end of the fourth energy saving capacitor CG 2 . A control end of the third transistor QG 1 is connected to a second end of the fourth current limit resistor RG 2 and a negative end of the second Zener diode ZDg 1 . A positive end of the second Zener diode ZDg 1 and a second end of the fourth energy saving capacitor CG 2 are grounded.

The first transistor Q 1 may be a field effect transistor or a triode.

The gate terminal, drain terminal and the source terminal of the field effect transistor are the control end, the input end and the output end of the first transistor Q 1 .

The base terminal, collector terminal and emitter terminal of the triode are the control end, the input end and the output end of the first transistor Q 1 .

The second transistor Q 2 includes a field effect transistor or a triode.

The gate terminal, drain terminal and the source terminal of the field effect transistor are the control end, the input end and the output end of the second transistor Q 2 .

The base terminal, collector terminal and emitter terminal of the triode are the control end, the input end and the output end of the second transistor Q 2 .

The third transistor Q 3 includes a field effect transistor or a triode.

The gate terminal, drain terminal and the source terminal of the field effect transistor are the control end, the input end and the output end of the third transistor Q 3 .

The base terminal, collector terminal and emitter terminal of the triode are the control end, the input end and the output end of the third transistor Q 3 .

In some embodiments, the PWM modulation circuit 105 includes a pulse width modulation (PWM) chip US 1 , an optical coupler U 2 , a third Zener diode ZD 2 , a sixth diode D 6 , a twenty-eighth resistor R 28 , a first divider resistor RS 1 , a second divider resistor RS 2 , a third divider resistor RS 3 , a fourth divider resistor RS 4 , a fifth divider resistor RS 5 , a sixth divider resistor RS 6 , a seventh divider resistor RS 7 , a first filter capacitor CS 1 , a second filter capacitor CS 2 , a third filter capacitor CS 3 and a fourth filter capacitor CS 4 .

An input end of the light source of the optical coupler U 2 , a negative end of the third Zener diode ZD 2 and a first end of the twenty-eighth resistor R 28 are connected and are used as an input end of the PWM modulation circuit 105 .

An output end of a light source of the optical coupler U 2 and a positive end of the third Zener diode are grounded. A second end of the twenty-eighth resistor R 28 is connected to a negative end of the sixth diode D 6 . The positive end of the sixth diode D 6 are connected to a reference voltage. An input of the receiver of the optical coupler U 2 is connected to a first end of the sixth divider resistor RS 6 . A second end of the sixth divider resistor RS 6 is connected to first serial portion DIM 0 of the PWM chip US 1 . A first end of the first divider resistor RS 1 and a first end of the seventh divider resistor RS 7 are connected to a management end ISET of the PWM chip US 1 .

The second end of the first divider resistor RS 1 is connected to a first end of the second divider resistor RS 2 . A first end of the fourth filter capacitor CS 4 is connected to a comparison end Vlow of the PWM chip US 1 .

A first end of the first filter capacitor CS 1 is connected to a Zender end FSET of the PWM chip US 1 . A second end of the seventh divider resistor RS 7 and a first end of the third divider resistor RS 3 are connected to an empty end NC of the PWM chip US 1 .

A first end of the fourth divider resistor RS 4 and a first end of the second filter capacitor CS 2 are connected to an input end VIN of the PWM chip US 1 .

The fourth divider voltage VIN, a first end of the fifth divider resistor RS 5 and a first end of the third filter capacitor CS 3 are connected to a second serial port DIM 1 of the PWM chip US 1 . A second end of the fifth divider resistor RS 5 is used as an output end of the PWM modulation circuit 105 . A second end of the fourth filter capacitor CS 4 , a second end of the second divider resistor RS 2 , a second end of the first filter capacitor CS 1 , a second end of the third divider resistor RS 3 , a second of the second filter capacitor CS 2 and a second end of the third filter capacitor CS 3 are grounded.

In some embodiments, the safety circuit 106 includes a twelfth diode D 1 , a transient voltage suppressor diode TVS 1 and a thermal resistor PTC 1 .

A positive end of the twelfth diode D 1 is an input end of the safety circuit 106 . A negative end of the twelfth diode D 1 and a first end of the transient voltage suppressor diode TVS 1 are connected to a first end of the thermal resistor PTC 1 .

A second end of the thermal resistor PTC 1 is an output end of the safety circuit 106 . A second end of the transient voltage suppressor diode TVS 1 is grounded.

FIG. 3 and FIG. 4 show a correct connection and an incorrect connection diagram for LED light tubes.

In some embodiments, when a user connects a dimmer as shown in FIG. 3 , the LED light tube works normally and emits light.

When a user connects the dimmer as FIG. 4 , the LED light tube does not emit light but the LED light tube is not damaged. When the user corrects the connection, the LED light tube works normally.

Please refer to FIG. 1 to FIG. 4 . The operation of the circuit embodiments is explained as follows.

First, L end and N end of the power source are connected to two pins of one end of the LED light tube. Two pins are connected to an external power source like 110V or 220V alternating current source.

The EMI circuit 101 filters EMI interference. The rectifying circuit 102 then rectifies the power to get a rectified signal. The rectified current is then filtered by the filter circuit 103 to get a filtered signal. The filtered signal is converted by the conversion circuit 104 to generate a constant current supplying to the LED modules in the LED light tube.

The dimming ends DIM+ and DIM− are connected to two pins of the other end of the LED light tube connecting to an external dimmer for receiving a dimming signal of a dimmer. The dimming signal may be a voltage signal or a PWM signal.

The dimming signal first passes through the safety circuit 106 , then to the PWM modulation circuit 105 . The PWM modulation circuit 105 converts the dimming signal to a standard PWM signal supplying to the PWM end of the conversion circuit 104 .

The transformer chip U 1 recognizes the pulse width of the standard PWM signal and adjusts sampling of the internal current of the transformer chip U 1 to control amount of the output current to adjust luminance level of the LED modules in the LED light tube.

The safety circuit 106 is connected in series between the PWM modulation circuit 105 and the dimming ends DIM+, DIM- to prevent low voltage DIM+, DIM− ends to be connected to L, N ends of high voltage while preventing the LED light tube not getting damaged.

Even the user makes mistake on connection for a while, when the connection is corrected, the LED light tube still works normally. The safety circuit 106 monitors voltage of the DIM+, DIM− ends. When a voltage in DIM+, DIM− ends is higher than a predetermined threshold, the voltage is lowered to safe voltage quickly to ensure that the PWM modulation circuit 105 not being damaged by high voltage.

When the DIM+, DIM− of low voltage are connected correctly, when the dimming signal of the ends has lower voltage than a clamping voltage of the TVS 1 , the TVS 1 does not work. When the current of the dimming signal is lower than an operation current of the PTC!, the PTC 1 is at low impedance and does not work. The dimming signal may be correctly detected by the PWM modulation circuit and the LED light tube is adjusted correctly for its luminance level.

When the DIM+, DIM− of low voltage are connected to L, N ends of high voltage, the high voltage signal passes through the positive temperature parameter fuse PTC 1 and two-way transient voltage suppressor diode TVS 1 . Because the current passing through the PTC 1 is large, the PTC 1 quickly increases its impedance when it is getting hotter quickly to limit current passing through the TVS 1 so as to keep the TVS 1 safe, not being damaged.

Meanwhile, the TVS may limit voltages at its two ends below 18V to ensure the DIMI end of the PWM chip US 1 not being damaged, when usually DIMI voltage should not exceed 20V. The diode D 1 is used for preventing the current back flowing to the DIMI end of the US 1 to protect the end. When the user finds the incorrect connection, the user corrects the error and the LED light tube works normally.

The PWM modulation circuit 105 automatically recognizes the dimming signal at DIM+, DIM− ends. The dimming signal may be a voltage signal or a PWM signal. The PWM modulation circuit 105 converts different voltage or dimming signal with different duty radio to a standard PWM signal with different duty ratio.

The standard PWM signal is supplied to the PWM end of the conversion circuit 104 . The transformer chip U 1 of the conversion circuit 104 recognizes the duty ratio of the standard PWM signal to adjust sampling base voltage, i.e. the voltage of the U 1 ISEN end, for current inside the transformer chip U 1 to control the output current and thus adjusts luminance level.

In summary, these embodiments provide a LED light tube apparatus with safety design for preventing incorrect connection damaging the LED light tube apparatus.

In FIG. 5A and FIG. 5B , the light tube apparatus may also include a first end cap 8804 and a second end cap 8807 , wherein the EMI circuit, the rectifier circuit, the filter circuit and the safety circuit together as a module 8803 are placed in at least one of the first end cap 8804 and the second end cap 8807 , the first end cap 8803 and the second end cap 8807 are disposed at two opposite ends of the tubular housing.

In FIG. 5A and FIG. 5B , the light tube apparatus may also include a second power circuit 8801 and a power terminal 8802 , wherein the first end cap 8804 and the second end cap 8807 are detachably removable. When the first end cap 8804 and the second end cap 8807 are removed from the tubular housing, the second power circuit 8801 supplies electricity to the LED module 8805 .

In FIG. 6 , the power terminal 8703 receives a direct current source 8701 . For example, when the LED light tube is to be installed in a bracket specifically designed for LED light tube, instead of a traditional light tube bracket, in which compatibility of multiple types of traditional light tubes need to be considered thus rendering unnecessary burden like blaster. In such case, the two end caps are removed, e.g. via screw structures or magnetic structures.

In FIG. 6 , the power terminal 8704 of another light tube is connected to the light tube apparatus just explained for receiving the direct current source. In such design, such LED light tube may be connected in series and scalable on deploying such LED light tubes.

In FIG. 6 , the power terminal also receives a control command 8706 from another light tube, the second power circuit controls the LED module according to the control command. In such design, the dimmer for controlling a first LED light tube may be shared to control a second LED light tube, simplifying control design.

In some embodiments, the second power circuit converts an alternating current to a direct current to drive the light source module.

In FIG. 7 , the light tube apparatus may also include a wireless circuit 8401 connected to the safety circuit 8402 and the conversion circuit 8403 , the wireless circuit 8401 is disconnected from the conversion circuit 8403 unless the safety circuit 8402 indicates a correct connection is done.

In FIG. 7 , the safety circuit 8402 includes a timer 8404 for waiting a predetermined time period before indicating the correct connection is done.

In some embodiments, the safety circuit executes a test operation for a predetermined time period before enabling the conversion circuit.

In some embodiments, the safety circuit triggers an alarm message to inform users the incorrect connection.

In FIG. 7 , the safety circuit sends the alarm message transmitted to a speaker 8406 to inform the users.

In FIG. 7 , the safety circuit shows the alarm message with an indicator 8405 .

In some embodiments, the indicator is a LED chip of the LED module.

In FIG. 7 , the safety circuit is connected to a fuse 8408 to turn off the conversion circuit 8403 .

The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings.

The embodiments were chosen and described in order to best explain the principles of the techniques and their practical applications. Others skilled in the art are thereby enabled to best utilize the techniques and various embodiments with various modifications as are suited to the particular use contemplated.

Although the disclosure and examples have been fully described with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of the disclosure and examples as defined by the claims.