Control circuit having error amplifier for DC-DC converter and control method therefor
a control circuit and error amplifier technology, applied in the direction of dc-dc conversion, power conversion systems, instruments, etc., can solve the problems of destabilizing the operation output voltage vout fluctuating beyond the control range of the dc-dc converter, and the feedback path of the error amplifier cannot be constructed
Active Publication Date: 2007-07-12
CYPRESS SEMICON CORP
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Benefits of technology
The invention is a control circuit and method for DC-DC converters that can detect and prevent unstable operation in which the output voltage fluctuates. The control circuit includes an error amplifier and a detection unit that detects when the error amplifier's output voltage stays at a predetermined level. This allows for the control circuit to prevent the output voltage from fluctuating and ensures stable operation of the DC-DC converter.
Problems solved by technology
That is, in cases where it is dropped when moved or taken out, the resistor R3 or the capacitor C2 comes off due to impact, and the feedback path for the error amplifier ERA1 cannot be constructed.
There are concerns that output voltage VOUT fluctuates beyond the control range of the DC-DC converter and the operation of the DC-DC converter is destabilized.
Method used
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[0027] Description will be given to the control circuit for DC-DC converters and the control method therefor according to the invention with reference to the embodiments illustrated in FIG. 1 to FIG. 6. FIG. 1 is a circuitry diagram of a step-down DC-DC converter 10 in a first embodiment. As illustrated in the drawing, the step-down DC-DC converter 10 includes a main switching transistor FET1, a synchronization switching transistor FET2, a choke coil L1, and a capacitor C1.
[0028] As illustrated in the drawing, the main switching transistor FET1 has a drain to which an input terminal (IN) is connected, and direct-current input voltage VIN is applied to it through the input terminal (IN). The source of the main switching transistor FET1 is connected to the drain of the synchronization switching transistor FET2. The source of the synchronization switching transistor FET2 is connected to ground. The source of the main switching transistor FET1 and the drain of the synchronization switc...
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A control circuit for DC-DC converters and a control method therefor wherein unstable operation in which output voltage fluctuates can be detected and the unstable operation be prevented from continuing are provided. The control circuit includes: an error amplifier ERA1 that has an inverting input terminal to which detecting voltage V1 detected according to output voltage is inputted and a non-inverting input terminal to which reference voltage e1 is inputted, and amplifies the difference voltage of detecting voltage relative to reference voltage e1; and a detection unit 50 that detects that an error output signal VOP of the error amplifier ERA1 stays at a predetermined voltage level. The detection unit 50 includes: a signal determination unit that determines that the predetermined voltage level is out of a normal operating range; and a duration count unit that detects that the predetermined voltage level stays out of the normal operating range for a predetermined time by the signal determination unit.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is based upon and claims the benefit of priority from each of the prior Japanese Patent Application No. 2006-001944 filed on Jan. 9, 2006, the entire contents of which are incorporated herein by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to a control circuit for DC-DC converters and a control method therefor. [0004] 2. Description of Related Art [0005] Portable electronic equipment uses a battery, such as electric cell, as power source. The power of a battery is discharged as time passes after the portable electronic equipment is actuated, and the output voltage of the battery drops with time. DC-DC converters have been used to keep power supply voltage, supplied to portable electronic equipment, constant even after the output voltage of its battery drops. [0006] Portable electronic equipment is connected with various devices. Therefore, it is required to...
Claims
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IPC IPC(8): G05F1/00
CPCH02M1/32H02M3/156H02M1/36H02M3/155
Inventor NATSUME, MASAHIRO
Owner CYPRESS SEMICON CORP