Solid-state lighting operable with ballasts and line voltages without ambiguity

A light-emitting diode (LED) lamp using an LED driving circuit, at least two frequency sensitive devices, at least six diodes configured to convert an AC voltage into a DC voltage and manage electric current flows, a switch control module, and a return current switch operates normally with an input voltage from either ballast or line voltages of AC mains. The LED driving circuit may be configured to operate normally only with the AC mains providing a regulated power and a current to LED arrays. When an input AC voltage is applied to the LED lamp, the at least six diodes and the at least two frequency sensitive devices can detect the input AC voltage, control electric current flowing into the switch control module or the LED driving circuit, and complete current returns so that the LED lamp can operate with either the ballast or the AC mains without operational ambiguity.

BACKGROUND

Technical Field

The present disclosure relates to light-emitting diode (LED) lamps that work with conventional fluorescent lamp fixtures configured to electrically connect either ballasts or line voltages.

Description of the Related Art

Solid-state lighting from semiconductor light-emitting diodes (LEDs) has received much attention in general lighting applications today. Because of its potential for more energy savings, better environmental protection (with no hazardous materials used), higher efficiency, smaller size, and longer lifetime than conventional incandescent bulbs and fluorescent tubes, the LED-based solid-state lighting will be a mainstream for general lighting in the near future. Meanwhile, as LED technologies develop with the drive for energy efficiency and clean technologies worldwide, more families and organizations will adopt LED lighting for their illumination applications. In this trend, the potential safety concerns such as risk of electric shock and fire become especially important and need to be well addressed.

In today's retrofit applications of an LED lamp to replace an existing fluorescent lamp, consumers may choose either to adopt a ballast-compatible LED lamp with an existing ballast used to operate the fluorescent lamp or to employ an AC mains-operable LED lamp by removing/bypassing the ballast. Either application has its advantages and disadvantages. In the former case, although the ballast consumes extra power, it is straightforward to replace the fluorescent lamp without rewiring, which consumers have a first impression that it is the best alternative. But the fact is that total cost of ownership for this approach is high regardless of very low initial cost. For example, the ballast-compatible LED lamps work only with particular types of ballasts. If the existing ballast is not compatible with the ballast-compatible LED lamp, the consumer will have to replace the ballast. Some facilities built long time ago incorporate different types of fixtures, which requires extensive labor for both identifying ballasts and replacing incompatible ones. Moreover, a ballast-compatible LED lamp can operate longer than the ballast. When an old ballast fails, a new ballast will be needed to replace in order to keep the ballast-compatible LED lamps working. Maintenance will be complicated, sometimes for the lamps and sometimes for the ballasts. The incurred cost will preponderate over the initial cost savings by changeover to the ballast-compatible LED lamps for hundreds of fixtures throughout a facility. In addition, replacing a failed ballast requires a certified electrician. The labor costs and long-term maintenance costs will be unacceptable to end users. From energy saving point of view, a ballast constantly draws power, even when the ballast-compatible LED lamps are dead or not installed. In this sense, any energy saved while using the ballast-compatible LED lamps becomes meaningless with the constant energy use by the ballast. In the long run, the ballast-compatible LED lamps are more expensive and less efficient than self-sustaining AC mains-operable LED lamps.

On the contrary, an AC mains-operable LED lamp does not require a ballast to operate. Before use of the AC mains-operable LED lamp, the ballast in a fixture must be removed or bypassed. Removing or bypassing the ballast does not require an electrician and can be replaced by end users. Each AC mains-operable LED lamp is self-sustaining. Once installed, the AC mains-operable LED lamps will only need to be replaced after 50,000 hours. In view of above advantages and disadvantages of both the ballast-compatible LED lamps and the AC mains-operable LED lamps, it seems that market needs a most cost-effective solution by using a universal LED lamp that can be used with the AC mains and is compatible with a ballast so that LED lamp users can save an initial cost by changeover to such an LED lamp followed by retrofitting the lamp fixture to be used with the AC mains when the ballast dies.

Ballasts have several different types. However, in the US, electronic ballasts are most popular in lamp fixtures because they are more efficient and less expensive than other types of ballasts. Nevertheless, it is better for the ballast-compatible LED lamp to be compatible with either electronic ballasts or other types of ballasts.

As mentioned above, a cost-effective solution may be to use a ballast as part of an LED driver to operate a lamp. In some prior art schemes, a switching mode power supply (SMPS) type LED driver is proposed to use with a ballast, but has not been completely accepted due to occasional fires that arise inside the ballast. The cause of these fires has been identified to be a large dc input capacitor in the SMPS type LED driver, which may destroy a capacitor in the ballast due to excessive initial resonant voltage. A conventional SMPS type LED driver for AC mains comprises a Buck converter, which can efficiently convert input voltages of 110˜277 VAC into a DC voltage required to power LEDs in an LED lamp. However, the ballast has an output voltage much higher than 277 VAC with a frequency well above 60 Hz. Such a Buck converter is controlled by a control logic, which has several drawbacks that limit its use in ballast applications. First, the control logic has a low operating voltage range which inherently limits the wide range of input voltages that can be used. Second, an over-voltage protection (OVP) function in the control logic starts at a low voltage limited by the low operating voltage. When an input voltage from a ballast exceeds a certain value, OVP functions to stop operation, shutting down the lamp. Third, the Buck converter operates in a continuous conduction mode, in which an input current fails to follow the input voltage, leading to a low power factor with the AC mains and turn-on or other operational failures with the ballast. Fourth, the control logic is solely powered by a voltage built up by an input capacitor with a small capacitance to meet a short start-up requirement. When the input voltage drops to the minimum operating voltage level, the control logic fails to operate and sends no signals to the switch, and the Buck converter stops to function until the input voltage level recovers, resulting in flickering. For an LED lamp operating solely with a ballast, the power and current control is basically via an impedance or output voltage control. In the former case, when input frequency changes, the impedance changes, altering an AC current to flow into the driving circuit. A ballast is, in practice, supposed to operate two or more lamps, and its output frequency of the ballast decreases as a load increases, meaning that the total power consumption does not linearly increase as the number of lamps used increases. In the worst case, an LED lamp that is designed for a group of three or four lamps in a fixture powered by a ballast may be burned out due to over-rated current flowing into the LED arrays in the lamp if only one of such a lamp is installed and operated for a long time in the fixture. For the latter case, the output voltage control approach may work with an electronic ballast but cannot be used in AC mains. In general, conventional LED drivers fail to work with a ballast and to properly operate an LED lamp at a regulated power, resulting in unstable lighting output. It goes without saying that the same LED drivers can flawlessly operate the LED lamp with the AC mains.

In U.S. Pat. No. 9,288,867, a ballast compatible and AC mains operable LED driver is disclosed to operate an LED lamp with either a ballast or a line voltage. However, the driver used needs to operate in a wide range of input voltage and frequency by using a power factor correction (PFC) and control device specially designed for such an application. When such a PFC and control device is not available, a dual mode operation seems impossible to achieve. In the present disclosure, a novel approach using a general-purpose PFC and control device to achieve functionality with either ballasts or line voltages in LED lamps will be well addressed.

SUMMARY

The present disclosure aims to provide a novel approach for an LED lamp to operate with either line voltages from AC mains or a ballast. The LED lamp may include a housing having one end or two opposite ends; one or more LED arrays; one or two lamp bases respectively connected to the one end or two opposite ends of the housing; at least two frequency sensitive devices; at least six diodes configured to manage electric current flows and to convert an alternating current (AC) input voltage from the line voltages of the AC mains or from the ballast into a direct current (DC) voltage; a switch control module; a return current control switch; and an LED driving circuit. The LED lamp is used to replace a fluorescent lamp in a retrofit or newly-made lamp fixture that could have an existing ballast installed or simply an AC mains-ready configuration. When such an LED lamp is installed in the fixture, the at least six diodes and the at least two frequency sensitive devices can detect if the input AC voltage from the ballast or line voltages from AC mains is applied, control electric current flows, and complete current returns so that the LED lamp can operate with either the existing ballast or the line voltages from AC mains without operational ambiguity.

The at least two frequency sensitive devices, the at least six diodes, the switch control module, and the return current control switch connected with the switch control module incorporating with the LED driving circuit are essential to make such a dual-mode operation possible. The LED driving circuit may include an input filter, a power factor correction (PFC) and control device, a Buck converter in communicating with the PFC and control device, and an output capacitor in parallel with a resistor connected to the Buck converter to build up an output voltage and to power the one or more LED arrays. The Buck converter comprises a first switch controlled by the PFC and control device, a current sensing resistor, a diode, and an inductor with its current charging and discharging controlled by the first switch. The PFC and control device detects zero current in the inductor generating control signals to control the first switch on and off with a constant on-time and a varied off-time. By adapting switching frequencies, the LED driving circuit can provide an accurate output LED current required to operate the one or more LED arrays when the input AC voltage is from a regular 110, 277, or 347 VAC line voltages of the AC mains. That is, when the input AC voltage is from the AC mains, the at least two frequency sensitive devices and the at least six diodes manage to drastically reduce a current flowing into the switch control module. Whereas the input DC voltage to the LED driving circuit is normal, the LED driving circuit is enabled to operate and provide a proper current required to the one or more LED arrays. On the other hand, when the input AC voltage is from the ballast, the at least two frequency sensitive devices and the at least six diodes manage a current flowing into the switch control module. Because supply current from the ballast is limited, the inrush current flowing into the switch control module crashes the input DC voltage to a substantially low level, which is not sufficiently high enough to operate the LED driving circuit. Instead, the return current control switch connected with the switch control module is enabled by the switch control module to conduct a current from the one or more LED arrays back to an applicable electrical connection terminal, thus completing the power transfer to the one or more LED arrays for using ballast as a power source.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

FIG. 1is a block diagram of an LED lamp800operable with either line voltages from AC mains or a ballast according to the present disclosure. The LED lamp800comprises a light emission portion700; a lamp base660comprising two electrical connection terminals255and256each respectively with two bi-pins250and350protruding outwards; at least six diodes comprising at least one rectifier603comprising at least four diodes611,612,613, and614interconnected at four input/output ports402,404,503, and504and at least two current control diodes618and619; an LED driving circuit100having two inputs connected to the input/outputs503and504receiving a direct current (DC) voltage rectified from the at least one rectifier603; and one or more LED arrays214disposed in the light emission portion700. The two pins of the respective bi-pins250and350are interconnected before connecting to the at least one rectifier603via the input/output ports402and404. The LED lamp800further comprises at least two frequency sensitive devices616and617together with the at least two current control diodes618and619configured to manage electric current flows; a switch control module710; and a return current control switch620controlled by the switch control module710. The LED lamp800is used to replace a fluorescent lamp in a retrofit or newly-made lamp fixture that could have an existing ballast installed or simply an AC mains-ready configuration. When the LED lamp800is installed in the fixture sockets electrically connected with either the ballast or the AC mains, the at least two frequency sensitive devices616and617and the at least two current control diodes618and619detect if an input AC voltage is from the ballast or the line voltages from the AC mains.

If the input AC voltage is from line voltages, such as 110, 277, or 347 V, of the AC mains, the at least two frequency sensitive devices616and617and the at least two current control diodes618and619substantially reduce a current to flow into the switch control module710, thus disabling the switch control module710and the return current control switch620. Instead, a normal DC voltage appears between the input/output ports503and504, enabling the LED driving circuit100to operate normally. The electric current flows into the LED driving circuit100, continuing to flow into the one or more LED arrays214. The current returned from the one or more LED arrays214goes through the LED driving circuit100, further down to the input/output port504, completing the power transfer to the one or more LED arrays214for the line voltages as a power source.

If the input AC voltage from the ballast is detected, the at least two frequency sensitive devices616and617and the at least two current control diodes618and619promote a current to flow into the switch control module710, thus enabling the switch control module710. Because a supply current from the ballast is limited, the inrush current flowing into the switch control module710crashes the input DC voltage between the input/output ports503and504to a substantially low level, which is not sufficiently high enough to operate the LED driving circuit100, thus disabling the LED driving circuit100. Instead, when the switch control module710is enabled, the return current control switch620is turned on by the switch control module710, which conduct a current returned from the one or more LED arrays214back to an applicable electrical connection terminal, thus completing the power transfer to the one or more LED arrays214for the ballast as a power source.

In general, the LED lamp800depicted inFIG. 1may fit in different sockets and thus may have different base types and shapes. InFIG. 1, although the LED lamp800is shown to have two sets of the electrical connection terminals255and256each with respective bi-pins250and350, the LED lamp800may have only one pin on each of the two electrical connection terminals255and256. The dotted line connected between AC sources and the two sets of the electrical connection terminals255and256denotes such a possibility. Nevertheless, the LED lamp800may come in a wide variety of shapes and rest on various electrical connection terminals with base types fixed with two or four pins used in compact fluorescent lamps (CFLs) and compact fluorescent bulbs, or with other E-base types used in other fluorescent lamps. Base types for two pin plug-in CFLs comprise G23, GX23, and G24D. For 4 pin plug-in CFLs, base types comprise G24Q, GX24Q, and 2G11. Base types for compact fluorescent bulbs comprise two-pin GU24, GU10 and GU5.3. The E-base types, although not of a pin-type, comprise E26, E27, or E39. As mentioned above, because the two pins of the respective bi-pins250and350in the LED lamp800are interconnected before connecting to the at least one rectifier603via the input/output ports402and404, either two-pin or four-pin operation works with the LED lamp800.

FIG. 2is a block diagram of a linear LED tube lamp900operable with either line voltages from AC mains or a ballast according to the present disclosure. The linear LED tube lamp900inFIG. 2has all the component as the LED lamp800inFIG. 1does except that the two bi-pins250and350protruding outwards from the two ends of the linear LED tube lamp900with the two electrical connection terminals255and256. InFIG. 2, the same numerals are used for the same components as inFIG. 1. The linear LED tube lamp900comprises a housing having two opposite ends; two lamp bases810and820having respective bi-pins250and350at each end of the housing; at least six diodes comprising at least one rectifier603comprising at least four diodes611,612,613, and614interconnected at four input/output ports402,404,503, and504and at least two current control diodes618and619; an LED driving circuit100having two inputs connected to input/outputs503and504; and one or more LED arrays214disposed in a light emission portion700. The two pins of the respective bi-pins250and350are interconnected before connecting to the at least one rectifier603via the input/output ports402and404. The linear LED tube lamp900further comprises at least two frequency sensitive devices616and617together with at least two current control diodes618and619configured to manage electric current flows; a switch control module710; and a return current control switch620controlled by the switch control module710. The linear LED tube lamp900is used to replace a linear fluorescent lamp such as T5, T8, or T12 lamps in a retrofit or newly-made lamp fixture that could have an existing ballast installed or simply an AC mains-ready configuration. When the linear LED tube lamp900is installed in the fixture, the at least two frequency sensitive devices616and617and the at least two current control diodes618and619detect if an input AC voltage is from a ballast or line voltages from AC mains.

If the input AC voltage is from the AC mains, the at least two frequency sensitive devices616and617and the at least two current control diodes618and619substantially reduce a current to flow into the switch control module710, thus disabling the switch control module710and the return current control switch620. Instead, a normal DC voltage appears between the input/output ports503and504, thus enabling the LED driving circuit100to operate normally. The electric current flows into the LED driving circuit100, continuing to flow into the one or more LED arrays214. The current returned from the one or more LED arrays214goes through the LED driving circuit100, further down to the input/output port504, completing the power transfer to the one or more LED arrays214.

If the input AC voltage from either T5, T8, or T12 fluorescent tube ballast is detected, the at least two frequency sensitive devices616and617and the at least two current control diodes618and619promote a current to flow into the switch control module710, thus enabling the switch control module710. Because supply current from the ballast is limited, the inrush current flowing into the switch control module710crashes the input DC voltage between the input/output ports503and504to a substantially low level, which is not sufficiently high enough to operate the LED driving circuit100, thus disabling the LED driving circuit100. Instead, when the switch control module710is enabled, the return current control switch620is turned on by the switch control module710, which conduct a current returned from the one or more LED arrays214back to an applicable electrical connection terminal, thus completing the power transfer to the one or more LED arrays214.

In general, the linear LED tube lamp900depicted inFIG. 2may fit in different sockets such as ones used in either T5, T8, or T12 fluorescent tubes. InFIG. 2, although the linear LED tube lamp900is shown to have the two electrical connection terminals255and256each with respective bi-pins250and350to receive power from AC sources, the linear LED tube lamp900may receive power from only one of two pins of each of two bi-pins250and350. The dotted line connected between AC sources and the two electrical connection terminals255and256inFIG. 2denotes such a possibility. Nevertheless, the linear LED tube lamp900may come in different lamp bases such as G13 and G5. As mentioned above, because the two pins of the respective bi-pins250and350in the linear LED tube lamp900are interconnected before connecting to the at least one rectifier603via the input/output ports402and404, either two-pin or four-pin operation works with the linear LED tube lamp900. Although the linear LED tube lamp900depicted inFIG. 2has a double-ended configuration, a single-ended operation is possible as long as the input AC voltage is applied between the input/output ports402and404. InFIGS. 1 and 2, although only one rectifier603is shown, each of the LED lamp800or the linear LED tube lamp900may comprise two rectifiers, featuring any-two input connection operable as long as a higher electrical potential port (i.e. the input/output port503) and a lower electrical potential port (i.e. the input/output port504) of each rectifier are respectively connected each other.

FIG. 3is a block diagram of an LED driving circuit100used in an LED lamp operable with either line voltages from AC mains or a ballast according to the present disclosure. InFIG. 3, the same numerals are used for the same components as inFIGS. 1 and 2. The LED driving circuit100connects to input/output ports503and504interconnected with at least one rectifier603with either line voltages from the AC mains or a ballast applied to ports402and404. When an input AC voltage applies between the ports402and404, the at least one rectifier603converts an alternating current (AC) input voltage into a direct current (DC) voltage between the input/output ports503and504. The LED driving circuit100comprises an input filter102used to filter an input voltage from the input/output ports503and504and to suppress EMI noise created in the LED driving circuit100, a power factor correction (PFC) and control device103, a Buck converter200in communicating with the PFC and control device103, an output capacitor105in parallel with a resistor106connected to the Buck converter200to build up an output voltage and to power the one or more LED arrays214, and a current sensing resistor107. A high electric potential at the input/output port503and a low electric potential at the input/output port504respectively connect to the high side and the low side of the input filter102with the low electric potential input/output port504as a common ground. The Buck converter200comprises a first switch201controlled by the PFC and control device103, a diode202, and an inductor203with its current charging and discharging controlled by the first switch201. The PFC and control device103detects zero current in the inductor203and generate control signals to control the first switch201on and off with a constant on-time and a varied off-time. By adapting switching frequencies, the PFC and control device103controls the first switch201on and off in a way that the inductor203is charged during on-time and discharged during off-time until a desired output voltage Voacross the one or more LED arrays214is reached to light up the one or more LED arrays214. An average inductor current is thus equal to the output current that flows into the LED array214. When the first switch201is on, the diode202is reverse-biased, and an input current flows from an output port108in the input filter102, the output resistor106, the inductor203, the first switch201, the first port204of the current sensing resistor107, the current sensing resistor107itself, and the second port205of the current sensing resistor107, back to the low electric potential port504. When the current flowing into the inductor203increases, the voltage across the current sensing resistor107increases. The PFC and control device103connecting to the first and the second ports204and205of the current sensing resistor107continuously receives signals and adjusts the off-time such that the output voltage and current to the one or more LED arrays214are regulated to meet the output requirements. The output capacitor105in parallel with the resistor106connecting to the inductor203thus can receive energy to build up an output voltage and to power the one or more LED arrays214.

InFIG. 3, the inductor203is configured as a primary winding of a transformer. When the power is on, an input current enters the input filter102and then the PFC and control device103, turning on the first switch201. Whereas the diode202is reverse-biased, the input current goes from the resistor106, the inductor203, the first switch201, and the current sensing resistor107to the common ground504. When the input current goes into the inductor203, energy is stored in it. The PFC and control device103detects the input voltage level and controls the first switch201on and off in a way that a desired output voltage Voacross the one or more LED arrays214is reached to light up the one or more LED arrays214. When the first switch201is off, the diode202is forward-biased, and the inductor203releases the energy stored, resulting in a loop current flowing from the diode202and the one or more LED arrays214, back to the inductor203, completing the energy transfer to the one or more LED arrays214. When the first switch201is on, the input current flows into the one or more LED arrays214, the inductor203, the first switch201, and the current sensing resistor107, creating a voltage drop across the current sensing resistor107. The voltage appearing at the port204of the current sensing resistor107inputs to the PFC and control device103to control the off-time of the switch201. The closed loop operation in both on-time and off-time of the switch201ensures the output current to be accurately controlled within 4%.

The LED driving circuit100may further comprise a voltage feedback module300. The voltage feedback module300has two connection ports301and302, with the first connection port301connecting to a high side of a secondary winding207in the transformer and with the second connection port302connecting to the PFC and control device103, as shown inFIG. 3. The voltage feedback module300continuously monitors the output voltage by using the secondary winding207in the transformer. When the voltage at the high side of the secondary winding207in the transformer is higher than a becoming lower operating voltage in the PFC and control device103due to increased internal operations, the diode (not shown) in the voltage feedback module300conducts to supply energy in time through the second connection port302and to sustain the operating voltage in the PFC and control device103. That is, the voltage feedback module300extracts partial energy from the output voltage to sustain the PFC and control device103. Although the function of the voltage feedback module300is essential for flicker-free operation of the LED lamps, a different LED driving circuit design may eliminate its use.

FIG. 4is an embodiment of a switch control module used in an LED lamp operable with either line voltages from AC mains or a ballast according to the present disclosure. Referring toFIGS. 3 and 4, the LED driving circuit100is further interconnected with at least two frequency sensitive devices616and617; at least two current control diodes618and619configured to manage electric current flows; a switch control module710comprising a resistor711, a capacitor712, and a Zener diode713(inFIG. 4) connected in parallel; and a return current control switch620controlled by the switch control module710. The return current control switch620is connected with the first switch201at a port206in the LED driving circuit100. When the input AC voltage is applied between the ports402and404, the at least two frequency sensitive devices616and617and the at least two current control diodes618and619detect if an input AC voltage is from the ballast or the AC mains, and allow or limit a current flow into the switch control module710.

Referring toFIGS. 3 and 4, if the input AC voltage is from line voltages of the AC mains, the at least two frequency sensitive devices616and617and the at least two current control diodes618and619detect the input AC voltage at a low frequency of 50˜60 Hz and substantially reduce the current to flow into the switch control module710. Whereas the current is small enough, the capacitor712, further discharged by the resistor711, is never charged to a voltage level set by the Zener voltage of the Zener diode713, thus disabling the switch control module710and in turn completely switching off the return current control switch620. On the other hand, a normal DC voltage appears between the input/output ports503and504, thus enabling the LED driving circuit100to operate normally. Consequently, the electric current flows into the one or more LED arrays214, the inductor203, the first switch201in the LED driving circuit100, the current sensing resistor107, back to the input/output port504, completing the power transfer to the one or more LED arrays214.

When an input AC voltage from the ballast is detected, the at least two frequency sensitive devices616and617and the at least two current control diodes618and619promote a current to flow into the switch control module710. The current flowing into the switch control module710rapidly charges the capacitor712in the switch control module710to a voltage level set by the Zener voltage of the Zener diode713. The frequency sensitive device617and the current control diode619continue to allow the current to flow in and pump the capacitor712, maintaining the Zener voltage. As long as the Zener voltage is maintained, the switch control module710is enabled to turn on the return current control switch620. Thus, an input current from the port503, passing through the input filter102and the output module and the one or more LED arrays214can flow out via the return current control switch620back to the input/output port504, thus completing the power transfer to the one or more LED arrays214. Because supply current from the ballast is limited, the inrush current flowing into the switch control module710crashes the input DC voltage between the input/output ports503and504to a substantially low level, which is not sufficiently high enough to operate the LED driving circuit100, thus disabling the LED driving circuit100.

FIG. 5is a block diagram of an LED lamp850operable with a ballast according to the present disclosure.FIG. 5is similar toFIG. 1, except that an input filter102and an output module101replace the LED driving circuit100inFIG. 1. InFIG. 5, the same numerals are used for the same components as inFIG. 1.FIG. 6is an embodiment of an output module used in an LED lamp operable with a ballast according to the present disclosure. Referring toFIGS. 5 and 6, when an input AC voltage from the ballast is detected, the at least two frequency sensitive devices616and617and the at least two current control diodes618and619promote a current to flow into the switch control module710. As depicted inFIG. 4, the switch control module710comprises a resistor711, a capacitor712, and a Zener diode713connected in parallel. The current flowing into the switch control module710charges the capacitor712to a voltage level set by a Zener voltage of the Zener diode713. As long as the Zener voltage is maintained on the capacitor712, the switch control module710is enabled to turn on the return current control switch620. Thus, an input current from the port503, passing through the input filter102and the output module101and the one or more LED arrays214can flow out via the return current control switch620back to an applicable electrical connection terminal, thus completing the power transfer to the one or more LED arrays214. InFIG. 6, the output module101connected to the one or more LED arrays214may comprise a resistor104and a capacitor105connected in parallel, configured to build up an output voltage supplied to one or more LED arrays214. The output module may further comprise an inductor106connected in series with the resistor104and the capacitor105, configured to smooth out a current increase.

The LED lamp850depicted inFIG. 5may fit in various sockets and thus may have various base types and shapes. InFIG. 5, although the LED lamp850is shown to have the two electrical connection terminals255and256each with respective bi-pins250and350, the LED lamp850may have only one pin on each of the two electrical connection terminals255and256. The dotted line connected between the ballast and the two electrical connection terminals255and256denotes such a possibility. Nevertheless, the LED lamp850may come in a wide variety of shapes and rest on various electrical connection terminals with base types fixed with two or four pins used in compact fluorescent lamps (CFLs) and compact fluorescent bulbs, or other E-base types used in other fluorescent lamps. Base types for two pin plug-in CFLs comprise G23, GX23, and G24D. For 4 pin plug-in CFLs, base types comprise G24Q, GX24Q, and 2G11. Base types for compact fluorescent bulbs comprise two-pin GU24, GU10 and GU5.3. The E-base types, although not of a pin-type, comprise E26, E27, or E39. As mentioned above, because the two pins of the respective bi-pins250and350in the LED lamp850are interconnected before connecting to the rectifier603via the input/output ports402and404, either two-pin or four-pin operation works with the LED lamp850.

FIG. 7is a block diagram of a linear LED tube lamp950operable with a ballast according to the present disclosure.FIG. 7is similar toFIG. 5, except that the linear LED tube lamp950inFIG. 5comprises two bi-pins250and350protruding outwards from the two ends of the linear LED tube lamp950with two electrical connection terminals255and256. When an input AC voltage from the ballast is detected, the at least two frequency sensitive devices616and617and the at least two current control diodes618and619promote a current to flow into the switch control module710. The current flowing into the switch control module710charges the capacitor712in the switch control module710to a voltage level set by the Zener voltage of the Zener diode713. As long as the Zener voltage is maintained, the switch control module710is enabled to turn on the return current control switch620. Thus, an input current from the port503, passing through the input filter102and the output module and the one or more LED arrays214can flow out via the return current control switch620back to an applicable electrical connection terminal, thus completing the power transfer to the one or more LED arrays214. Not like a conventional ballast compatible only linear LED tube lamp, which can easily be burned out when an AC voltage from the AC mains is accidentally applied to the bi-pins250and350, the linear LED tube lamp950according to the present disclosure has an advantage, of which no fire hazard is possible due to said misapplication. This is because the return current control switch620can only be turned on by the switch control module710, which can only be enabled by AC voltage at a high frequency such as 40˜65 kHz from the ballast.

The linear LED tube lamp950depicted inFIG. 7may fit in different sockets such as ones used in T5, T8, or T12 fluorescent tubes. InFIG. 5, although the linear LED tube lamp950is shown to have the two electrical connection terminals255and256each with the respective bi-pins250and350to receive power from AC sources, the linear LED tube lamp950may receive power from only one of two pins of each of bi-pins250and350. The dotted line connected between the ballast and the two electrical connection terminals255and256inFIG. 5denotes such a possibility. Nevertheless, the linear LED tube lamp950may come in different lamp bases such as G13 and G5. As mentioned above, because the two pins of the respective bi-pins250and350in the linear LED tube lamp950are interconnected before connecting to the at least one rectifier603via the input/output ports402and404, either two-pin or four-pin operation works with the linear LED tube lamp950.

InFIGS. 1-3, 5, and 7, the return current switch620may comprise electrical terminals of at least one relay. The at least one relay may comprise a solid-state relay, an electronic relay, or an electro-mechanical relay. The return current switch620may comprise electrical terminals of at least one triac. The return current switch620may comprise electrical terminals of at least one electronic switch. The at least one electronic switch may comprise a metal-oxide-semiconductor field-effect transistor (MOSFET), a field-effect transistor (FET), a transistor, a back-to-back thyristor, a silicon-controlled rectifier (SCR), or a combination thereof.

Whereas preferred embodiments of the present disclosure have been shown and described, it will be realized that alterations, modifications, and improvements may be made thereto without departing from the scope of the following claims. Another LED driving circuit with another frequency sensitive devices or another electric current flow management in an LED lamp using various kinds of combinations to accomplish the same or different objectives could be easily adapted for use from the present disclosure. Accordingly, the foregoing descriptions and attached drawings are by way of example only, and are not intended to be limiting.