TECHNICAL FIELD

The present disclosure generally relates to methods and structures that incorporate linear power supplies into light emitting devices while simultaneously providing a suitable power factor and flicker percentage for the lamp. The present disclosure also relates to methods and structures that incorporate linear power supplies into light emitting devices providing acceptable thermal performance, and providing EMI filtering while receiving pulse width modulation (PWM) control signals.

BACKGROUND

Improvements in lighting technology often rely on finite light sources (e.g., light-emitting diode (LED) devices) to generate light. In many applications, LED devices offer superior performance to conventional light sources (e.g., incandescent and halogen lamps). Further, light bulbs have become smarter in recent years. People can now replace standard incandescent bulbs with smart bulbs that can be controlled wirelessly using smart phones or tablets. How to make a smart lamp not only with decent quality meeting all the standards, but also at a low price can be a challenge. This can be complicated by lighting standards that may be required of an area or jurisdiction. For example, smart lighting products sold in California are to meet CEC Title 21 tier 2 standards.

SUMMARY

In one embodiment, the methods and structures of the present disclosure provide a smart bulb with low standby power, low EMI emission, low cost, low flicker percentage, and a high-power factor in a linear power supply design.

In one aspect, a driver circuit for lighting applications is provided that includes a linear power supply circuit, in which the circuits when integrated into a smart bulb can provide a low standby power, low EMI emission, low cost, low flicker percentage, and a high-power factor.

In one embodiment, the driver circuit that includes an input side including a power input circuit and an output side including a light emitting diode (LED) output current circuit. The output side of the driver circuit includes an output smoothing capacitor for controlling flicker percentage. A light emitting diode (LED) power supply circuit is present between the input side and the output side of the driver circuit. The light emitting diode (LED) power supply circuit is for controlling current from the AC power input circuit to the light emitting diode (LED) output current circuit, wherein the LED power supply circuit includes at least one linear current regulator. The driver circuit includes a controller circuit including a controller for signaling the light emitting diode (LED) power supply to control current to the light emitting diode (LED) output current circuit to provide a lighting characteristic. In one embodiment, the at least one linear current regulator includes at least two linear current regulators that are in parallel connection, wherein by said parallel connection thermal load is divided between the at least two linear current regulators.

In some embodiments, the driver circuit can simultaneously provide both a flicker percentage that is less than 30%, and a power factor that is greater than 0.7. In some embodiments, the driver circuit does not include an input smoothing capacitor for controlling flickering in the input side of the driver circuit. In the driver circuit, the flickering percentage is controlled by the output capacitance only, via the output smoothing capacitor.

In some embodiments, the driver circuit further includes a communications module in communication with the controller circuit. The communications module can feed a pulse width modulation (PWM) signal to the input side of the driver circuit. This signal may be used to control the dimming settings of the light engine of the lamp being powered through the driver circuit. In some embodiments, the driver circuit further includes an electromagnetic interference (EMI) filter in the input side of the driver circuit. The electromagnetic interference (EMI) filter can be present between the bridge rectifier of the power input circuit and the light emitting diode (LED) power supply circuit.

In another aspect, a lamp is provided that can include a linear power supply circuit, in which the circuits when integrated into a smart bulb can provide a low standby power, low EMI emission, low cost, low flicker percentage, and a high-power factor. In some embodiments, the lamp includes light emitting diodes (LEDs) for providing light; and a driver package including an input side having a power input circuit and an output side having a light emitting diode (LED) output current circuit to the light engine, wherein the output side of the driver circuit includes an output smoothing capacitor for controlling flicker percentage. The driver circuit can also include a light emitting diode (LED) power supply circuit present between the input side and the output side of the driver circuit, wherein the LED power supply circuit includes at least one linear current regulator. The driver circuit can also include a controller circuit including a controller for signaling the light emitting diode (LED) power supply to control current to the light emitting diode (LED) output current circuit for powering the light engine. In one embodiment, the at least one linear current regulator includes at least two linear current regulators that are in parallel connection, wherein by the parallel connection thermal load is divided between the at least two linear current regulators.

In some embodiments, the light emitting diodes (LEDs) of lamp includes from 5 light emitting diodes (LEDs) to 25 light emitting diodes (LEDs) that are connected in series. In some embodiments, the lamp can simultaneously provide both a flicker percentage that is less than 30%, and a power factor that is greater than 0.7. The lamp may further include a communications module in communication with the controller circuit. The communications module can feed a pulse width modulation (PWM) signal to the input side of the driver circuit. The lamp may further include an electromagnetic interference (EMI) filter in the input side of the driver circuit. The EMI filter may filter the noise of the pulse width modulation (PWM) signal being fed to the driver circuit.

In another aspect, a method of powering a lighting device is provided, in which the method can provide a lamp having a low standby power, low EMI emission, low cost, low flicker percentage, and a high-power factor. In one embodiment, the method includes positioning a driver circuit between a power source and a light engine, the driver circuit including an input side including a power input circuit for communication to the power source, and an output side in communication with the light engine. The method further includes controlling flickering performance by positioning an output smoothing capacitor in the output side of the driver circuit, wherein the input side of the circuit does not include an input smoothing capacitor. The method further includes controlling current from the power source to the light engine with a light emitting diode (LED) power supply circuit that is present between the input side and the output side of the driver circuit. The light emitting diode (LED) power supply circuit includes at one linear current regulator. In some embodiments, the at least one linear current regulator includes at least two linear current regulators that are in parallel connection, wherein by the parallel connection thermal load is divided between the at least two linear current regulators. In some embodiments, the method can provide a lamp having a flicker percentage that is less than 30%, and having a power factor that is greater than 0.7. In some embodiments, controlling the current by the light emitting diode (LED) power supply circuit can include a pulse width modulation (PWM) control signal that is fed into the input side of the circuit. In some embodiments, the method may further include filtering noise from the pulse width modulation (PWM) control signal with an EMI filter positioned between the light emitting diode (LED) power supply circuit and the power source.

