POWER SUPPLY UNIT AND PORTABLE DEVICE
First Claim
1. A power supply unit, comprising:
- a switching power supply circuit that includes a coil, a switch connected in series to said coil for cutting on and off the electric current supplied from a power supply voltage node to said coil, a rectifying and smoothing circuit for rectifying and smoothing the voltage that appears at the serial connection node of said coil and switch and for outputting the rectified and smoothed voltage as said positive output voltage, and a control circuit for controlling on-off operation of said switch so as to bring a detection voltage associated with said positive output voltage to a reference voltage; and
a negative output voltage generation circuit, connected between said serial connection node of said coil and switch and said power supply voltage node, for generating a predetermined negative output voltage based on said positive output voltage and power supply voltage.
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Accused Products
Abstract
A switching type power supply unit adapted to generate a positive output voltages though conversion of a power supply voltage has an negative output voltage generation circuit switchably connected, via a changeover switch, between the first node of a coil and a switch and the second node receiving the power supply voltage or between the first node and the ground. The negative output voltage generation circuit is connected to the second node when the voltage difference between the positive output voltage (Vp) and the power supply voltage (Vbat) is sufficiently large, while the circuit is connected to the ground when the difference voltage is small. Thus, the power supply unit efficiently provides a negative output voltage having a predetermined level along with a positive output voltage (Vn) generated from the power supply voltage through conversion thereof.
19 Citations
12 Claims
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1. A power supply unit, comprising:
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a switching power supply circuit that includes a coil, a switch connected in series to said coil for cutting on and off the electric current supplied from a power supply voltage node to said coil, a rectifying and smoothing circuit for rectifying and smoothing the voltage that appears at the serial connection node of said coil and switch and for outputting the rectified and smoothed voltage as said positive output voltage, and a control circuit for controlling on-off operation of said switch so as to bring a detection voltage associated with said positive output voltage to a reference voltage; and
a negative output voltage generation circuit, connected between said serial connection node of said coil and switch and said power supply voltage node, for generating a predetermined negative output voltage based on said positive output voltage and power supply voltage. - View Dependent Claims (2, 3, 4, 5, 11, 12)
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6. A power supply unit, comprising:
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a switching power supply circuit that includes a coil, a switch connected in series to said coil for cutting on and off the electric current supplied from a power supply voltage node to said coil, a rectifying and smoothing circuit for rectifying and smoothing the voltage that appears at the serial connection node of said coil and switch and for outputting the rectified and smoothed voltage as said positive output voltage, and a control circuit for controlling on-off operation of said switch so as to bring a detection voltage associated with said positive output voltage to a reference voltage; and
a negative output voltage generation circuit, switchably connected, via a change-over switch circuit, between said serial connection node of said coil and switch and either one of said power supply voltage node and a stable voltage node, for generating a predetermined negative output voltage based on said positive output voltage and either one of said power supply voltage and stable voltage. - View Dependent Claims (7, 8, 9, 10)
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Specification