Title:
OSCILLATION CIRCUIT
Document Type and Number:
Japanese Patent JP3914047
Kind Code:
B2
Abstract:
PROBLEM TO BE SOLVED: To solve the problem wherein the amplitude of a triangular wave signal becomes larger as the frequency of the triangular wave signal increases, resulting in a decrease of a maximum on duty ratio.
SOLUTION: In an oscillation circuit used for PWM (pulse wave modulation) control for outputting an interterminal voltage of a capacitor for charging/ discharging by a constant current as the triangular wave signal, the capacitor comprises a series circuit having a first capacitor 23 via an on/off switch 22 and a second capacitor 24 having a capacity so set that it is smaller than that of the capacitor 23, the interterminal voltage is compared with a third threshold voltage VB (VL<VB<VH, VH-VB≥VB-VL), a control signal of H level is output to the switch 22 until the interterminal voltage is equal to or exceeds the threshold voltage VB, and a control signal of L level is output to the switch 22 when the interterminal voltage is equal to or exceeds the voltage VB. The switch 22 is turned on when the control signal of H level is input, and is turned off when the control signal of L level is input. The maximum on duty ratio of the PWM control is determined by using the triangular wave signal caused by charge/discharge of the capacitor 24 at the time when the switch 22 is off.
Inventors:
Hiroshi Fujiwara
Application Number:
JP2001387087A
Publication Date:
May 16, 2007
Filing Date:
December 20, 2001
Export Citation:
Assignee:
NEC Electronics Corporation
International Classes:
H02M3/155; H03K4/06; H03K3/02; H03K7/08; (IPC1-7): H03K4/06; H02M3/155; H03K3/02; H03K7/08
Domestic Patent References:
| JP570030U | ||||
| JP4737167A |
Attorney, Agent or Firm:
Tatsuo Tokumaru
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