| 摘要 |
PROBLEM TO BE SOLVED: To reduce the power consumption by using a weak electric field reception signal from a tuner and a video input tuner reception switching signal for control signals and using the control signals so as to close/open a switching, thereby switching the capacitance of a pseudo-resonance power supply and hence to reduce a power supply switching loss and to suppress heat generation at a video input or at reception of a usual electric field strength signal, without deteriorating interfere performance upon reception of a weak electric field strength signal. SOLUTION: At the reception of a weak electric field strength signal, a weak electric field signal detection signal 4 is given to a microcomputer 3, which provides a resonance capacitor on/off control signal 4 that activates a switching resonance capacitor 6 to a relay 8 which is a component of a switch. Conversely, at the reception of a normal electric field strength signal, the microcomputer 3 provides the output of a resonance capacitor on/off control signal 4 that inactivates the switch resonance capacitor 6 to the relay 8 which is constitutes a component of the switch. Thus, at reception time of a normal electric field strength signal, the switching resonance capacitor 6 is inactivated, and a switching power supply device is obtained, for which switching loss is reduced. |
