Constant-Current Controller with Square-Wave Input Current Shaping

A boost-type switching power converter comprising:

• a rectified voltage source;
• an inductor coupled to the rectified voltage source;
• a rectifier diode coupled to the inductor;
• a smoothing capacitor coupled to the rectifier diode;
• one or more light emitting diodes (LEDs) connected in parallel with the smoothing capacitor;
• a controlled power switch coupled to the rectifier diode and in parallel with the smoothing capacitor;
• a current sense resistor coupled to the controlled power switch;
• and
• an LED driver controller coupled to the controlled power switch and the current sense resistor;
• wherein the LED driver controller outputs a pulse-width modulated control signal to the controlled power switch;
• wherein the current sense resistor develops a current sense voltage representing a current in the inductor;
• wherein an average magnitude of the current in the inductor equals an input current provided by the rectified voltage source;
• and
• wherein the LED driver controller comprises
• a sample and hold circuit that samples a current sense voltage;
• a first multiplier circuit that multiplies an output of the sample and hold circuit;
• an error detector circuit that compares an output of the multiplier circuit with a reference voltage;
• an error amplifier that amplifies an output of the error detector circuit;
• and
• an output circuit that outputs the pulse-width modulated control signal based on an output of the error amplifier.

A buck-boost-type switching power converter comprising:

• a rectified voltage source;
• an inductor coupled to the rectified voltage source;
• a rectifier diode coupled to the inductor;
• a smoothing capacitor coupled to the rectifier diode and the inductor;
• one or more light emitting diodes (LEDs) connected in parallel with the smoothing capacitor;
• a controlled power switch coupled to the rectifier diode and the inductor;
• a current sense resistor coupled to the controlled power switch;
• and
• an LED driver controller coupled to the controlled power switch and the current sense resistor;
• wherein the LED driver controller outputs a pulse-width modulated control signal to the controlled power switch;
• wherein the current sense resistor develops a current sense voltage representing at least a portion of a current in the inductor;
• wherein an average magnitude of the current in the inductor equals an input current provided by the rectified voltage source;
• and
• wherein the LED driver controller comprises:
• a sample and hold circuit that samples a current sense voltage;
• a first multiplier circuit that multiplies an output of the sample and hold circuit;
• an error detector circuit that compares an output of the multiplier circuit with a reference voltage;
• an error amplifier that amplifies an output of the error detector circuit;
• and
• an output circuit that outputs a pulse-width modulated control signal based on an output of the error amplifier.