US 7,321,222 B2
Switching regulator with DC offset (bias) in controller
Yoshiyuki Hojo, Kyoto (Japan)
Assigned to Rohm Co., Ltd., Kyoto (Japan)
Appl. No. 10/589,163
PCT Filed Jan. 20, 2005, PCT No. PCT/JP2005/000637
§ 371(c)(1), (2), (4) Date Aug. 10, 2006,
PCT Pub. No. WO2005/078910, PCT Pub. Date Aug. 25, 2005.
Claims priority of application No. 2004-036770 (JP), filed on Feb. 13, 2004.
Prior Publication US 2007/0170904 A1, Jul. 26, 2007
Int. Cl. G05F 1/613 (2006.01); G05F 1/40 (2006.01)
U.S. Cl. 323—224  [323/283; 323/284] 8 Claims
OG exemplary drawing
 
1. A switching power supply apparatus, including:
a switching device for performing an on/off operation;
a control circuit for controlling on/off of the switching device;
a coil, a level of a current flowing therethrough being controlled by the switching device;
a capacitor that is connected to the coil and that performs rectification together with the coil; and
an oscillator for outputting to the control circuit an oscillating signal at intervals of a fixed time period for turning the switching device on,
wherein the switching power supply apparatus outputs an output voltage from a node at which the capacitor and the coil are connected together,
the switching power supply apparatus comprising:
a current detection portion for detecting a current value flowing through the coil, converting the detected current value into a voltage value, and then outputting the voltage value thus obtained as a current detection voltage;
a voltage source for adding an offset voltage to the current detection voltage from the current detection portion; and
a comparator for comparing the current detection voltage to which the offset voltage is added by the voltage source with a voltage commensurate with a difference between a voltage commensurate with the output voltage and a reference voltage,
wherein, if the comparator finds a magnitude of the current detection voltage to which the offset voltage is added to be greater than the voltage commensurate with a difference between the voltage commensurate with the output voltage and the reference voltage, the oscillating signal from the oscillator is masked, and the switching device is turned off.