Patent Application
20060061216
The present invention relates to power supply circuits and more particularly to such a power supply circuit, installed in an electronic device, capable of eliminating a potential electrical interference of one grounded load by grounding the other load independently in which the loads have different operating voltages.
A conventional power supply circuit of an AV (audio video) product such as LCD (liquid crystal display) or LCD TV (television) is shown in
In view of the above, power sources of both the loads are from the same rectifier and the driving loop. Also, both loads are grounded. The first load is required to operate in a low and stable DC voltage. Otherwise, it may be interfered, for example by fluctuation voltage occurred on the second load of high voltage, resulting in nipples and uneven hue on the display, poor speaker output quality, noise, etc. The interference is occurred because the voltage increase of the inverter is achieved by oscillating wave which adversely affects the first load via the common ground. That is, the first load is interfered by the voltage increase in the inverter. Such drawback is even serious in a large screen display of TV. Hence, a need for improvement exists.
It is an object of the present invention to provide a novel power supply circuit having a first load of low voltage grounded and a second load of high voltage grounded independently. Also, the power supply circuit comprises two parallel power paths in which one is coupled to the first load via a first power circuit and the other one is coupled to the second load via a second power circuit. In brief, the grounding of the first load and the grounding of the second load are independent, resulting in the elimination of a potential electrical interference in the first load.
It is another object of the present invention to provide a power supply circuit in which a single switch is provided for turning on or off all components of an electronic device (e.g., AV product) incorporating the power supply circuit of the present invention in one operation without adversely affecting efficiency and quality of the display thereof.
The above and other objects, features and advantages of the present invention will become apparent from the following detailed description taken with the accompanying drawings.
Referring to
The first power circuit 20 comprises a first rectifier 21 coupled to the AC input 10, two parallel default power supply unit 22 and first power supply unit 23, and a switch 24 coupled to both the power supply units 22 and 23. The default power supply unit 22 comprises a first driving loop 221 for receiving rectified DC from the first rectifier 21 and outputting driving signals, and a first transformer 222 for lowering voltage. The first power supply unit 23 comprises a first power factor adjustment unit 231 for filtering the rectified DC, a second driving loop 232 for receiving the filtered DC and outputting driving signals, and a second transformer 233 for lowering voltage.
The second power circuit 30 comprises a second rectifier 31, a second power supply unit 33, and a second power factor adjustment unit 32 interconnected the second rectifier 31 and the second power supply unit 33 for filtering the DC output of the second rectifier 31 to obtain a relatively smooth DC voltage. The second power supply unit 33 is implemented as an inverter and comprises a third driving loop 331 coupled to the second power factor adjustment unit 32 and a third transformer 332 interconnected the third driving loop 331 and the second load 50. Note that the second power factor adjustment unit 32 may be eliminated in another embodiment. That is, the second rectifier 31 is coupled to the third driving loop 331 directly. DC voltage whether smooth (i.e., having second power factor adjustment unit 32) or not (i.e., no second power factor adjustment unit 32) is applied to the inverter (i.e., the second power supply unit 33) for increasing voltage.
As shown in
In view of above, the first load 40 and the second load 50 are activated by the first power supply unit 23 and the second power supply unit 33 respectively. That is, the first load 40 and the second load 50 are activated independently. As such, any fluctuation voltage occurred on the second load 50 of high voltage will not transmit to the first load 40 of low voltage. As a result, the first load 40 still can operate normally in a low operating voltage.
Referring to
While the invention herein disclosed has been described by means of specific embodiments, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope and spirit of the invention set forth in the claims.
