One example described herein includes a light-emitting diode (LED) driver system. The system includes an error amplifier configured to compare an input voltage with a reference voltage to generate a control voltage. The system further includes an amplifier output stage configured to control an output current through a first current path and a shunt current through a second current path based on the control voltage. The amplifier output stage comprises a slew-rate controller configured to control a slew-rate of the shunt current. The shunt current can be provided through a shunt resistor in the second current path and added to the output current to provide a total current through an LED string.

One example described herein includes a light-emitting diode (LED) driver system. The system includes an error amplifier configured to compare an input voltage with a reference voltage to generate a control voltage. The system further includes an amplifier output stage configured to control an output current through a first current path and a shunt current through a second current path based on the control voltage. The amplifier output stage comprises a slew-rate controller configured to control a slew-rate of the shunt current. The shunt current can be provided through a shunt resistor in the second current path and added to the output current to provide a total current through an LED string.

The invention provides an LED drive power supply and a controller thereof. The controller comprises a ground terminal, a sampling terminal, and a power supply terminal. The ground terminal and an output ground of a power supply module have different potentials. A drain of a power switching transistor is coupled to a positive output terminal of the power supply module, a source of the power switching transistor and the sampling terminal are coupled to a first terminal of a sampling resistor, and a second terminal of the sampling resistor is coupled to the ground terminal. The controller further includes a logic control circuit determining whether a sampling voltage input by the sampling terminal is zero; a driver generating a first driving signal to the power switching transistor; and a bias circuit configured to receive a power supply voltage.

The invention provides an LED drive power supply and a controller thereof. The controller comprises a ground terminal, a sampling terminal, and a power supply terminal. The ground terminal and an output ground of a power supply module have different potentials. A drain of a power switching transistor is coupled to a positive output terminal of the power supply module, a source of the power switching transistor and the sampling terminal are coupled to a first terminal of a sampling resistor, and a second terminal of the sampling resistor is coupled to the ground terminal. The controller further includes a logic control circuit determining whether a sampling voltage input by the sampling terminal is zero; a driver generating a first driving signal to the power switching transistor; and a bias circuit configured to receive a power supply voltage.

System and method for current control. As an example, the system for current control includes: a transistor including a drain terminal, a gate terminal, and a source terminal, the drain terminal being coupled to one or more light emitting diodes; a resistor coupled to the source terminal of the transistor and configured to generate a resistor voltage related to a current flowing through the one or more emitting diodes; a voltage detector configured to receiver a first input voltage related to a second input voltage received by the one or more light emitting diodes; and a voltage controller coupled to the voltage detector, the resistor, and the gate terminal of the transistor; wherein the voltage detector is further configured to: detect the first input voltage; and generate a control signal based at least in part on the first input voltage.

System and method for current control. As an example, the system for current control includes: a transistor including a drain terminal, a gate terminal, and a source terminal, the drain terminal being coupled to one or more light emitting diodes; a resistor coupled to the source terminal of the transistor and configured to generate a resistor voltage related to a current flowing through the one or more emitting diodes; a voltage detector configured to receiver a first input voltage related to a second input voltage received by the one or more light emitting diodes; and a voltage controller coupled to the voltage detector, the resistor, and the gate terminal of the transistor; wherein the voltage detector is further configured to: detect the first input voltage; and generate a control signal based at least in part on the first input voltage.

System and method for controlling one or more light emitting diodes. For example, the system includes: a power supply controller configured to receive a cathode voltage from a cathode of a diode, the diode including an anode configured to receive a rectified voltage generated by a rectifying bridge, the power supply controller being further configured to generate a first signal based at least in part on the cathode voltage; and a driver configured to receive the first signal and generate a second signal based at least in part on the first signal, the driver being further configured to output the second signal to a gate terminal of a transistor, the transistor including a source terminal coupled to the driver and a first resistor, the transistor further including a drain terminal coupled to the one or more light emitting diodes and an output capacitor connected to the cathode of the diode.

System and method for controlling one or more light emitting diodes. For example, the system includes: a power supply controller configured to receive a cathode voltage from a cathode of a diode, the diode including an anode configured to receive a rectified voltage generated by a rectifying bridge, the power supply controller being further configured to generate a first signal based at least in part on the cathode voltage; and a driver configured to receive the first signal and generate a second signal based at least in part on the first signal, the driver being further configured to output the second signal to a gate terminal of a transistor, the transistor including a source terminal coupled to the driver and a first resistor, the transistor further including a drain terminal coupled to the one or more light emitting diodes and an output capacitor connected to the cathode of the diode.

The invention relates to an incorporation of a current limiting/regulating circuit on a luminaire board for ensuring that the luminaire board will automatically operate at its desired current after a replacement. Since the current control at the luminaire board causes an initial mismatch between the current supply of the driver and the demand of the luminaire board, the driver output voltage will drift towards the maximum output voltage of the driver. When the maximum output voltage is reached, the driver is configured to operate in constant-voltage (CV) mode, sense the output current and reduce its output current to the same value as consumed by current-controlled luminaire board. Alternatively, the driver may gradually reduce the setpoint of the output current until it just leaves the CV mode and stay at that setpoint. In this way, the driver will automatically operate at the correct current of a newly installed luminaire board without any action from the user.

The invention relates to an incorporation of a current limiting/regulating circuit on a luminaire board for ensuring that the luminaire board will automatically operate at its desired current after a replacement. Since the current control at the luminaire board causes an initial mismatch between the current supply of the driver and the demand of the luminaire board, the driver output voltage will drift towards the maximum output voltage of the driver. When the maximum output voltage is reached, the driver is configured to operate in constant-voltage (CV) mode, sense the output current and reduce its output current to the same value as consumed by current-controlled luminaire board. Alternatively, the driver may gradually reduce the setpoint of the output current until it just leaves the CV mode and stay at that setpoint. In this way, the driver will automatically operate at the correct current of a newly installed luminaire board without any action from the user.