1. CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority to Chinese Patent Application No. 201910124049.0, filed Feb. 19, 2019, incorporated by reference herein for all purposes.

2. BACKGROUND OF THE INVENTION

Certain embodiments of the present invention are directed to integrated circuits. More particularly, some embodiments of the invention provide systems and methods for voltage conversion. Merely by way of example, some embodiments of the invention have been applied to light emitting diode (LED) lighting systems that include TRIAC dimmers. But it would be recognized that the invention has a much broader range of applicability.

A conventional lighting system often includes a TRIAC dimmer that is a dimmer including a Triode for Alternating Current (TRIAC). For example, the TRIAC dimmer is either a leading-edge TRIAC dimmer or a trailing-edge TRIAC dimmer. Usually, the leading-edge TRIAC dimmer and the trailing-edge TRIAC dimmer are configured to receive an alternating-current (AC) input voltage, process the AC input voltage by clipping part of the waveform of the AC input voltage, and generate a voltage that is then received by a rectifier (e.g., a full wave rectifying bridge) in order to generate a rectified output voltage. The rectified output voltage is converted to a DC voltage by an RC filtering circuit that includes a resistor and a capacitor, and the DC voltage is then used to control a driver to generate a drive signal for one or more light emitting diodes (LEDs).

FIG. 1is a simplified diagram of a conventional lighting system that includes a TRIAC dimmer. The conventional lighting system100includes a TRIAC dimmer110, a rectifier120, resistors170,172and174, a capacitor180, a driver140, and one or more LEDs150. As shown, the resistors170and172are parts of a voltage divider, and the resistor174and the capacitor180are parts of an RC filtering circuit. For example, the rectifier120is a full wave rectifying bridge that includes diodes132,134,136and138.

The TRIAC dimmer110receives an AC input voltage114(e.g., VLine) and generates a voltage112. The voltage112is received by the rectifier120(e.g., a full wave rectifying bridge), which then generates a rectified output voltage122. The rectified output voltage122is larger than or equal to zero. As shown inFIG. 1, the rectified output voltage122is received by the resistor170and the one or more LEDs150. In response, the voltage divider including the resistors170and172generates a voltage182(e.g., Vs), as follows:

Vs=R2R1+R2×Vo(Equation⁢⁢1)
where Vsrepresents the voltage182, and Vorepresents the voltage122. Additionally, R1represents the resistance of the resistor170, and R2represents the resistance of the resistor172. The voltage182(e.g., Vs) is received by the resistor174. In response, the RC filtering circuit including the resistor174and the capacitor180generates a reference voltage184(e.g., VREF). For example, the reference voltage184(e.g., VREF) is a DC voltage. The reference voltage184is received by the driver140, which in response affects (e.g., controls) a load current142that flows through the one or more LEDs150. Referring toFIG. 1, each cycle of the AC input voltage114(e.g., VLine) has a phase angel (e.g., ϕ) that changes from 0 to π and then from π to 2π.

FIG. 2Ashows a conventional timing diagram for the voltage182of the lighting system100that includes a leading-edge TRIAC dimmer as the TRIAC dimmer110, andFIG. 2Bshows a conventional timing diagram for the voltage182of the lighting system100that includes a trailing-edge TRIAC dimmer as the TRIAC dimmer110. For each cycle of the AC input voltage114(e.g., VLine), time t1corresponds to phase 0, time t2corresponds to phase ϕJ, time t3corresponds to phase ϕK, time t4corresponds to phase π, time is corresponds to phase π+ϕJ, time t6corresponds to phase π+ϕK, and time t7corresponds to phase 2π.

As shown inFIG. 2A, the waveform220represents the voltage182(e.g., Vs) as a function of time if the TRIAC dimmer110is a leading-edge TRIAC dimmer. The leading-edge TRIAC dimmer processes the AC input voltage114(e.g., VLine) by clipping part of the waveform that corresponds to the phase starting at 0 and ending at ϕJand clipping part of the waveform that corresponds to the phase starting at π and ending at π+ϕJ, for each cycle of the AC input voltage114(e.g., VLine). For each cycle, the AC input voltage114(e.g., VLine) is clipped by the leading-edge TRIAC dimmer from time t1to time t2and from time t4to time t5, but the AC input voltage114(e.g., VLine) is not clipped by the leading-edge TRIAC dimmer from time t2to time t4and from time t5to time t7.

As shown inFIG. 2B, the waveform230represents the voltage182(e.g., Vs) as a function of time if the TRIAC dimmer110is a trailing-edge TRIAC dimmer. The trailing-edge TRIAC dimmer processes the AC input voltage114(e.g., VLine) by clipping part of the waveform that corresponds to the phase starting at ϕKand ending at π and clipping part of the waveform that corresponds to the phase starting at π+ϕKand ending at 2π, for each cycle of the AC input voltage114(e.g., VLine). For each cycle, the AC input voltage114(e.g., VLine) is clipped by the trailing-edge TRIAC dimmer from time t3to time t4and from time t6to time t7, but the AC input voltage114(e.g., VLine) is not clipped by the leading-edge TRIAC dimmer from time t1to time t3and from time t4to time t6.

As shown inFIG. 1, it is often difficult to integrate the RC filtering circuit into an integrated circuit (IC) chip with limited size. Hence it is highly desirable to improve the LED drive techniques that use one or more TRIAC dimmers.

3. BRIEF SUMMARY OF THE INVENTION

Certain embodiments of the present invention are directed to integrated circuits. More particularly, some embodiments of the invention provide systems and methods for voltage conversion. Merely by way of example, some embodiments of the invention have been applied to light emitting diode (LED) lighting systems that include TRIAC dimmers. But it would be recognized that the invention has a much broader range of applicability.

According to some embodiments, a system for voltage conversion to drive one or more light emitting diodes with at least a TRIAC dimmer, the system comprising: a phase detector configured to receive a first rectified voltage generated based at least in part on an AC input voltage processed by at least the TRIAC dimmer, the phase detector being further configured to generate a digital signal representing phase information associated with the first rectified voltage; a voltage generator configured to receive the digital signal and generate a DC voltage based at least in part on the digital signal; and a driver configured to receive the DC voltage and affect, based at least in part on the DC voltage, a current flowing through the one or more light emitting diodes; wherein the current changes with the phase information according to a predetermined function.

According to certain embodiments, a method for voltage conversion to drive one or more light emitting diodes with at least a TRIAC dimmer, the method comprising: receiving a first rectified voltage generated based at least in part on an AC input voltage processed by at least the TRIAC dimmer; processing at least information associated with the first rectified voltage; generating a digital signal representing phase information associated with the first rectified voltage; receiving the digital signal; generating a DC voltage based at least in part on the digital signal; receiving the DC voltage; and affecting, based at least in part on the DC voltage, a current flowing through the one or more light emitting diodes; wherein the current changes with the phase information according to a predetermined function.

Depending upon embodiment, one or more benefits may be achieved. These benefits and various additional objects, features and advantages of the present invention can be fully appreciated with reference to the detailed description and accompanying drawings that follow.

