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 (CONV_PWM) 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 (DIM_PWM) supplied to the dimming power switch; and power control circuitry characterised by including: 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 a normal response when maintaining a desired undimmed level of lamp current to automatically increase the lamp voltage in response to a decrease in the level of lamp current; characterised in that the power control circuitry comprises: 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) during an off time of the dimming control signal, the dimming control circuitry operates to maintain the lamp voltage to correspond to a voltage reference signal (Vv_reference), to prevent the normal operation of the converter control circuitry to prevent the automatic increase of the lamp voltage in response to a decrease in lamp current, and (b) during an on time of the dimming control signal, to enable the normal operation of the converter control circuitry. 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 (CONV_PWM) 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 (DIM_PWM) supplied to the dimming power switch; and power control circuitry characterised by including: 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 a normal response when maintaining a desired undimmed level of lamp current to automatically increase the lamp voltage in response to a decrease in the level of lamp current; characterised in that the power control circuitry comprises: 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) during an off time of the dimming control signal, the dimming control circuitry operates to maintain the lamp voltage to correspond to a voltage reference signal (Vv_reference), to prevent the normal operation of the converter control circuitry to prevent the automatic increase of the lamp voltage in response to a decrease in lamp current, and (b) during an on time of the dimming control signal, to enable the normal operation of the converter control circuitry. 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 a normal response when maintaining a desired undimmed level of lamp current to automatically increase the lamp voltage in response to a decrease in the level of lamp current; characterised in that the power control circuitry comprises: 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) during an off time of the dimming control signal, the dimming control circuitry operates to maintain the lamp voltage to correspond to a voltage reference signal (Vv_reference), to prevent the normal operation of the converter control circuitry to prevent the automatic increase of the lamp voltage in response to a decrease in lamp current, and (b) during an on time of the dimming control signal, to enable the normal operation of the converter control circuitry.