Patent ID: 8502512
Filing Date: 2013-08-06
Classification: H02M,Y02B

Abstract:
1. A direct current (DC) power converting circuit, for generating a predetermined DC voltage, comprising: a DC input end, for receiving a DC input voltage; a DC output end, for providing the predetermined DC voltage; a switch, coupled between the DC input end and the DC output end, for providing a direct path, wherein the switch is an FET having a source coupled to the DC input end and a drain coupled to the DC output end via an inductor; a DC-DC step-down unit, coupled between the DC input end and the DC output end, for providing a step-down voltage path, wherein the DC-DC step-down unit is a DC-DC step-down integrated circuit controlled by a logic level voltage and the DC-DC step-down circuit has a DC-DC step-down circuit input end coupled to the DC input end and a DC-DC step-down circuit output end coupled to the DC output end; and a control unit, coupled to the switch and the DC-DC step-down unit, for detecting the DC input voltage to select either the direct path or the step-down voltage path in order to providing the predetermined DC voltage to the DC output end, wherein the control unit comprises: a sampling circuit, coupled to the DC input end, for obtaining a sampled signal of the DC input voltage, wherein the sampling circuit comprises: a comparing circuit, coupled to the sampling circuit, for receiving the sampled signal and comparing the sampled signal with a reference voltage to generate a comparison result, wherein the comparing circuit comprises: a control signal generating circuit, coupled to the comparing circuit, for generating a control signal for controlling the switch and the DC-DC step-down unit simultaneously, wherein the control signal generating circuit comprises: wherein when DC input voltage is greater than an upper limit of a predetermined operating voltage range, the control unit triggers the switch to open and enable the DC-DC step-down unit to select the step-down voltage path, and when the DC input voltage is within the predetermined operating voltage range, the control unit triggers the switch to close and disables the DC-DC step-down unit to select the direct path.