Constant-current and constant-voltage driving circuit of dcbl fan motor with low acoustic noise and controllable speed

A constant-current and constant-voltage driving circuit of a direct-current motor, the direct-current motor comprising a first magnetic coil and a second magnetic coil, wherein the first magnetic coil has a first terminal and a second terminal, the second magnetic coil has a third terminal and a fourth terminal, and the second terminal and the fourth terminal are electrically coupled to a first reference voltage, the constant-current and constant-voltage driving circuit comprising:

• an integrated circuit chip having a first chip output terminal and a second chip output terminal;
• a first switch having a first control terminal, a fifth terminal and a sixth terminal, wherein the first control terminal is electrically coupled to the first chip output terminal of the integrated circuit chip, the fifth terminal is electrically coupled to a second reference voltage, and the sixth terminal is electrically coupled to the first terminal of the first magnetic coil;
• and
• a second switch having a second control terminal, a seventh terminal and an eighth terminal, wherein the second control terminal is electrically coupled to the second chip output terminal of the integrated circuit chip, the seventh terminal is electrically coupled to the second reference voltage, and the eighth terminal is electrically coupled to the third terminal of the second magnetic coil;
• wherein the first switch and the second switch are non-simultaneously turned on according to a first current and a second current respectively flowing through the first chip output terminal and the second chip output terminal, so as to drive the first magnetic coil and the second magnetic coil respectively, wherein the first current or the second current is substantially constant, and the first magnetic coil and the second magnetic coil are non-simultaneously driven according to respective constant voltages generated by the first switch and the second switch.