Led driver operating from unfiltered mains on a half-cycle by half-cycle basis

An LED driver circuit for powering a string of LEDs directly from mains-level AC voltage comprising:

• a constant current sink circuit, the current regulated through a power transistor to a predetermined current level and where the current can be turned off by grounding a low voltage control point;
• an overtemperature detect circuit configured to turn off the sink current via a coupling to the control point when temperature reaches a predetermined value.

An LED dimmer circuit comprising a constant sink current circuit with a low voltage control point where grounding the low voltage control point turns off LED current and a PWM circuit coupled to the control point as to provide a dimming function;

• the LED dimmer circuit such that the constant current circuit and the PWM circuit are each operative directly from AC mains without requirement for voltage step down or AC-to-DC filtering.

A controlled LED power supply with means for rectification, means for constant sink current provisioning and means for protection from excessive power dissipation, the power supply operable from AC mains with out filtering AC-to-DC or step down voltage circuitry.