Patent ID: 8395329

Claim:
A power supply for an LED lamp having a plurality of series-connected high-power light-emitting diodes, comprising: primary-side power circuitry including a converter power switch in series with a primary-side coil for conducting input power based on a converter control signal supplied to the converter power switch; secondary-side power circuitry including a dimming power switch in series with the LED lamp and a secondary-side coil inductively coupled to the primary-side coil for providing output power to the LED lamp based on a dimming control signal supplied to the dimming power switch; and power control circuitry including: (1) converter control circuitry having a normal operation by which it generates the converter control signal to maintain a desired undimmed level of lamp current in the LED lamp at a normal operating value of a lamp voltage of the LED lamp, the normal operation including an automatic increasing of the lamp voltage in response to a decrease in lamp current; and (2) dimming control circuitry operative to generate the dimming control signal to pulse-width modulate the lamp current at a duty cycle corresponding to a desired dimming of the LED lamp, and (a) at on-to-off transitions of the dimming control signal, to modify operation of the converter control circuitry to prevent the automatic increasing of the lamp voltage in response to a decrease in lamp current, and (b) at off-to-on transitions of the dimming control signal, to restore normal operation of the converter control circuitry.