Illuminating device

An illuminating device, comprising:

• a circuit board having a first surface and a second surface at an opposite side of the circuit board to the first surface;
• a light source electrically mounted on the first surface of the circuit board;
• a thermoelectric cooler attached on the second surface of the circuit board;
• a heat sink being attached on an opposite side of the thermoelectric cooler to the circuit board;
• a first ceramic board sandwiched between the circuit board and the thermoelectric cooler, and a second ceramic board sandwiched between the thermoelectric cooler and the heat sink;
• a temperature sensor attached to the circuit board adjacent to the light source for detecting heat radiation emitted therefrom;
• and
• a control circuit being electrically connected with the temperature sensor and the thermoelectric cooler;
• wherein the thermoelectric cooler selectively operates in a first working mode or a second working mode, the thermoelectric cooler which operates in the second working mode is capable of absorbing more heat than that operates in the first working mode;
• and
• wherein the control circuit comprises a comparing unit and a control unit, and a predetermined reference value of a temperature stored in the comparing unit, the comparing unit is configured for comparing a value of temperature detected by the temperature sensor with the predetermined reference value and generating a control signal to the control unit, the control unit is configured for supplying a current to the thermoelectric cooler based on the control signal so as to change the working mode of the thermoelectric cooler between the first working mode and the second working mode.