Solid-state lighting with a battery backup control
An LED luminaire comprises a rechargeable battery, LED array(s), at least two drivers, a battery charging circuit, and a detection and control circuit. The LED luminaire may be used to replace a fluorescent or a conventional LED lamp connected to AC mains. The at least two drivers comprise a power switching driver and a constant current driver. The power switching driver is configured to power the LED array(s) and the battery charging circuit whereas the constant current driver is configured to convert a battery terminal voltage from the rechargeable battery to a DC voltage to light up the LED array(s) when a line voltage from the AC mains is unavailable. The detection and control circuit is configured to disable the constant current driver when the line voltage from the AC mains is available or to enable the constant current driver when the line voltage from the AC mains is unavailable.
1. A light-emitting diode (LED) luminaire, comprising:
one or more LED arrays;
a rechargeable battery;
a full-wave rectifier configured to convert a line voltage from alternate-current (AC) mains into a first direct-current (DC) voltage;
an input filter configured to suppress an electromagnetic interference (EMI) noise;
a power switching driver comprising a transformer having a primary side and a secondary side, a first rectifier and a second rectifier on the secondary side of the transformer, and a power factor correction (PFC) and control circuit, the power switching driver coupled to the full-wave rectifier via the input filter and configured to convert the first DC voltage into a second DC voltage and a third DC voltage, respectively, via the first rectifier and the second rectifier;
a battery charging circuit comprising a voltage control circuit, a current control circuit, and a first transistor circuit, the battery charging circuit configured to receive and regulate the third DC voltage into a fourth DC voltage to charge the rechargeable battery to a battery terminal voltage;
a battery-operated driver comprising an input transistor and a constant current driver, the constant current driver configured to convert the battery terminal voltage into a fifth DC voltage; and
a detection and control circuit comprising multiple transistor circuits, the detection and control circuit configured to control the input transistor and to enable or disable the constant current driver,
wherein:
the second DC voltage is utilized to operate the one or more LED arrays with a full lumen output when the line voltage from the AC mains is available; and
the fifth DC voltage is utilized to operate the one or more LED arrays with a reduced lumen output relative to the full lumen output when the battery-operated driver is enabled.
2. The LED luminaire of claim 1 , wherein the voltage control circuit comprises a first operational amplifier, a first voltage reference, a first voltage divider coupled to the first operational amplifier, and a first diode, the voltage control circuit configured to sample the third DC voltage and the fourth DC voltage and to partially control a charging current flowing into the rechargeable battery via the first transistor circuit.
3. The LED luminaire of claim 1 , wherein the current control circuit comprises a second operational amplifier, a second voltage reference, a second voltage divider coupled to the second operational amplifier, and a second diode, the current control circuit configured to partially control a charging current flowing into the rechargeable battery via the first transistor circuit.
4. The LED luminaire of claim 1 , wherein the first transistor circuit comprises a first transistor and a third diode connected in series with the first transistor, wherein the first transistor is coupled to the voltage control circuit and the current control circuit, and wherein the first transistor circuit is coupled between the third DC voltage and the fourth DC voltage and to regulate a charging current to charge the rechargeable battery.
5. The LED luminaire of claim 1 , wherein the power switching driver further comprises a third rectifier configured to generate a sixth DC voltage to signal that the line voltage from the AC mains is available.
6. The LED luminaire of claim 5 , wherein the multiple transistor circuits comprise a second transistor circuit configured to receive the sixth DC voltage and to pull down a control voltage to the input transistor and to disable the constant current driver.
7. The LED luminaire of claim 6 , wherein the multiple transistor circuits further comprise a third transistor circuit and a fourth transistor circuit, wherein the third transistor circuit and the fourth transistor circuit are coupled between the second transistor circuit and the input transistor, and wherein the third transistor circuit and the fourth transistor circuit are configured to regulate and to deliver the battery terminal voltage to the input transistor.
8. The LED luminaire of claim 7 , wherein the input transistor is configured to further receive a control voltage from the second transistor circuit to activate the constant current driver when enabled.
9. The LED luminaire of claim 8 , wherein the third transistor circuit and the fourth transistor circuit comprise at least one Zener diode and at least two resistors, the at least one Zener diode and the at least two resistors configured to regulate the battery terminal voltage and to balance out the fourth DC voltage, the sixth DC voltage, and the battery terminal voltage for safe and reliable operations.
10. The LED luminaire of claim 1 , wherein the detection and control circuit further comprises a pair of metal-oxide-semiconductor field-effect transistor (MOSFET) circuits configured to monitor an electric grid and to determine whether the line voltage from the electric grid is available or not, and wherein the pair of MOSFET circuits send out a high-level signal voltage equivalent to an operating voltage of the pair of MOSFET circuits so as to turn off the input transistor and to disable the constant current driver when the line voltage from the electric grid is available.
11. The LED luminaire of claim 10 , wherein the pair of MOSFET circuits comprise two MOSFETs, a capacitor, and a third operational amplifier with a reference voltage, wherein the two MOSFETs and the third operational amplifier are configured to receive the battery terminal voltage, wherein the third operational amplifier is configured to compare a voltage across the capacitor to the reference voltage, and wherein the third operational amplifier is configured to send out a low-level signal voltage equivalent to a grounding voltage when the line voltage from the electric grid is unavailable.
12. The LED luminaire of claim 11 , wherein the low-level signal voltage is configured to apply to the second transistor circuit to pull up a control voltage to the input transistor and to enable the constant current driver.
13. The LED luminaire of claim 1 , wherein the constant current driver comprises a boost converter with the fifth DC voltage higher than the battery terminal voltage and a forward voltage across the one or more LED arrays to operate the one or more LED arrays without flickering.
14. The LED luminaire of claim 1 , wherein the constant current driver further comprises at least one inductor and at least one diode coupled to the one or more LED arrays, wherein the first rectifier is coupled to the one or more LED arrays, and wherein the at least one diode and the first rectifier are configured to avoid voltage crossovers between the second DC voltage and the fifth DC voltage.
15. The LED luminaire of claim 1 , wherein the power switching driver is a step-down converter with the second DC voltage lower than the first DC voltage but higher than the third DC voltage.
16. The LED luminaire of claim 1 , wherein the detection and control circuit further comprises a switch, and wherein when enabled, the switch is configured to allow the rechargeable battery to be charged when the line voltage from the AC mains is available or to be discharged so as to operate the battery-operated driver when the line voltage from the AC mains is unavailable.