Patent ID: 7301788

Claim:
A power transform device for reaching low acoustic noise comprising: a power source node; a switch node; a ground node; a transform element electrically coupled between the power source node and the switch node; a first spike noise snubber having a first terminal, which is electrically coupled to the power source node, and a second terminal; a first switch unit electrically coupled between the second terminal of the first spike noise snubber and the switch node; a second spike noise snubber having a first terminal, which is electrically coupled to the power source node, and a second terminal; a second switch unit electrically coupled between the second terminal of the first spike noise snubber and the second terminal of the second spike noise snubber; and a third switch unit electrically coupled between the ground node and the switch node for selectively conducting or cutting off a current flowing between the ground node and the switch node, and spike noise is generated when the third switch unit is switched from conduction to cut off; wherein the first switch unit is conducted when a voltage difference between the second terminal of the first spike noise snubber and the switch node is larger than a first predetermined voltage; wherein the second switch unit is conducted when a voltage difference between the second terminal of the first spike noise snubber and the second terminal of the second spike noise snubber is larger than a second predetermined voltage, which is larger than the first predetermined voltage; wherein the first switch unit is conducted for snubbing the generated spike noise with the first spike noise snubber when the generated spike noise is higher than the first predetermined voltage but lower than the second predetermined voltage; wherein both the first switch unit and the second switch unit are conducted for snubbing the generated spike noise with both the first spike noise snubber and the second spike noise snubber simultaneously when the generated spike noise is higher than the second predetermined voltage.