Patent ID: 8395489
Filing Date: 2013-03-12
Classification: B60R

Abstract:
1. A vehicle burglar alarm circuit comprising: a transformer including an input unit and an output unit, wherein the input unit includes a first tap, a second tap and a center tap, the center tap being connected to a center of a coil between the first tap and the second tap, and the output unit is magnetically coupled to the input unit, the output unit having output taps connected to a sounding body; a first power source, configured to be detachable and attachable, including one electrode connected to the center tap to output a first DC voltage; a second power source including one electrode connected to the center tap to output a second DC voltage that is lower than the first DC voltage; a sounding body driving unit including a first switching element having one end connected to the first tap and another end connected to the other electrode of the first power source, and a second switching element having one end connected to the second tap and another end connected to the other electrode of the second power source; a PWM controller for outputting driving signals by which the first switching element and the second switching element are alternately turned on and off and controlling on-duty ratios of the first switching element and the second switching element; and a power selecting unit for selecting one of the first and the second power source to supply a power to the transformer, wherein the PWM controller generates a first on-duty ratio when the first power source is selected and a second on-duty ratio when the second power source is selected such that the first on-duty ratio is smaller than the second on-duty ratio.