Electric power conversion systems – Current conversion – Including d.c.-a.c.-d.c. converter
Reexamination Certificate
2000-06-08
2001-03-06
Wong, Peter S. (Department: 2838)
Electric power conversion systems
Current conversion
Including d.c.-a.c.-d.c. converter
C363S097000, C323S902000
Reexamination Certificate
active
06198639
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a circuit arrangement for producing a constant voltage in a converter, particularly in the case of a flyback converter operated in a step-up mode. The invention also relates to a method for producing a constant voltage in a converter.
To keep a power that is to be converted and, hence, the thermal loading of the converter at a low level the DC isolation between the primary and the secondary of the transformer in the converter is removed and results in the circuit shown in FIG.
2
. This converter produces a differential voltage between an output voltage that is to be achieved,and an input voltage applied to the input of the converter. In this arrangement, the output voltage of the converter is the result of adding the applied input voltage and the voltage produced by the converter. This converter, operated in step-up mode, is called a step-up converter.
To achieve an output voltage of +/−68 V, for example, with an input voltage applied to the input of +/−37 V, for example, the step-up converter needs to introduce a voltage of +/−31 V.
For an input voltage of +/−67 V, for example, the voltage to be readjusted by the step-up converter's converter's is +/−1 V.
However, step-up converters have the disadvantage that the output voltage cannot be kept constant if the voltage difference between the input voltage applied to its input and the output voltage becomes approximately zero.
SUMMARY OF THE INVENTION
An object of the present invention is to specify a circuit arrangement and a method for producing a constant output voltage from a step-up converter.
According to the present invention, this and other objects are achieved by a circuit arrangement for producing a constant voltage in a converter including an input circuit, the input circuit being connected to an input voltage. In addition, a switching transistor is located within the input circuit. A drive unit is included for producing a drive signal for the switching transistor and a current transformer unit located within the input circuit produces a first control signal with the current transformer unit being connected to a first input of the drive unit. The circuit arrangement further includes an output circuit and a smoothing unit terminating the output circuit with at least one connection of an output of the smoothing unit connected to a first connection of an output of the circuit arrangement. A control unit is disposed between the first connection and the second connection with the output of the circuit arrangement for producing a second control signal that is connected to a second input of the drive unit. Finally, a control signal production unit is disposed between the first input of the drive unit and an output of the current transformer unit for outputting the first control signal with the control signal production unit producing a third control signal that is formed based on a voltage-mode control and is superimposed on the first control signal.
Another aspect of the present invention includes a method for producing a constant voltage having the steps of connecting an input voltage to an input circuit of a converter, producing a first control signal using a current transformer unit disposed in the input circuit of the converter, applying the first control signal to a first input of a drive unit, generating the drive signal and the drive unit for a switching transistor disposed in the input circuit of the converter in response to the first control signal, providing a smoothing unit in an output circuit of the converter with at least one output of the smoothing unit being connected to an output of the converter, connecting a control unit between outputs of the converter with the control unit producing a second control signal, applying the second control signal to a second input of the drive unit, generating a third control signal using a voltage mode control and superimposing the third control signal on the first control signal.
The present invention affords the advantage that no low-frequency voltage fluctuations in the output voltage of the step-up converter occur with small voltage differences between the output voltage that is to be achieved and the predetermined input voltage.
The present invention affords the further advantage that an additional drive voltage for the converter's switching transistor is used such that a ramp-shaped form of the converter's drive voltage brings the converter into operation at reduced speed in line with its drive voltage when a high input voltage is applied to the input.
Additional advantages and novel features of the invention will be set forth, in part, in the description that follows and, in part, will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
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Patent Abstracts of Japan: 07 327 362, Dec. 12, 1995, DC Power Supply, Inventor: Tatsumi Naotake.
Reinhard Bloeckl, Schaltnetzteil: Eingangsspannung (fast) egal, Elekronik, Jul. 1991, pp. 122-126.
Bitenc Bostjan
Eisert Werner
Lochter Werner
Wolfgart Bernd
Schiff & Hardin & Waite
Siemens Aktiengesellschaft
Vu Bao Q.
Wong Peter S.
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