Electricity: power supply or regulation systems – In shunt with source or load – Using a three or more terminal semiconductive device
Patent
1989-10-20
1990-10-30
Beha, Jr., William H.
Electricity: power supply or regulation systems
In shunt with source or load
Using a three or more terminal semiconductive device
323271, 323286, 323299, H02M 3158
Patent
active
049671383
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a secondary switched-mode regulator according to the preamble of patent claim 1.
Secondary switched-mode regulators serve for the generation of a regulated output voltage from an unregulated input voltage, there being no electrical isolation between the input and the output, in contrast to the primary-clocked switched-mode power supplies. Secondary switched-mode regulators may be designed as step-up converters or as step-down converters. In the case of the first, the output voltage is higher, in the case of the step-down converter the output voltage is lower than the respectively applied input voltage. The design and operating principle of secondary switched-mode regulators, in particular of the two embodiments as step-up converter and step-down converter, are described in the book "Halbleiterschaltungstechnik" (Semiconductor circuitry) by Tietze and Schenk, 5th edition, chapter 16.5.1.
If the DC input voltage varies in a wide tolerance zone around the value of the output voltage or if the input voltage is to be converted into a DC output voltage such that the input voltage can have both a higher and a lower value than the output voltage, it is known from German Offenlegungsschrift No. 1,905,369 to combine step-down converters and step-up converters. The control of each of the two semiconductor switches is in this case performed via a dedicated device known per se for a fixed or varyingly adjustable pulse duty factor, so that the attainable magnitude of the output voltage is either greater than, equal to or less than the input voltage.
In this case, a common clock frequency and the keeping of the same turn-on times can be used for both semiconductor switches.
The object of the invention is to specify a circuit arrangement for the conversion of an unregulated DC input voltage into a regulated DC output voltage using a secondary switched-mode regulator designed as a combined step-up/step-down converter, which is cost-effective to produce and the power loss of which is reduced.
This object is achieved according to the invention by the features specified in patent claim 1.
Advantageous configurations and further developments are defined in the subclaims.
Due to a simulation circuit, which simulates the current in the inductance (storage choke) during the charging of the inductance as capacitor voltage, lossy current sensing resistors or complex current transformer circuits (transformers) are avoided.
An input voltage monitoring which switches off the entire transformer when the input voltage is too low offers a reliable protection against the possible dropping of the input voltage to values which are far below the permissible minimum voltage and which would lead to the impermissible increasing of the input current to be connected.
A further advantage is that a common driver circuit is used for both semiconductor switches (switching transistors) and, as a result, a power loss reduction in comparison with conventional driver circuits is achieved.
If a selectable threshold is crossed in the downward direction, the set value of the regulating circuit is reduced and at the same time a so-called soft start is also achieved. Such an output monitoring circuit has the advantage that, as a result, the transformer is absolutely short-circuit-proof and conditionally also overload-proof. Consequently, a lower thermal loading is produced in the event of a short-circuit than in the case of full load. In the case of an overload, the current limitation is generally achieved by the simulation circuit.
The invention is now explained in more detail with reference to the drawing, in which:
FIG. 1 shows a combined secondary switched-mode regulator as step-up/step-down converter,
FIG. 2 shows a block circuit diagram of the regulating circuit used for such a secondary switched-mode regulator,
FIG. 3 shows a driver circuit for the switching transistors,
FIG. 4 shows a circuit for the input voltage monitoring,
FIG. 5 shows a circuit for the output voltage monitoring,
FIG. 6 shows a simulation circuit and
FIG. 7
REFERENCES:
patent: 3641422 (1972-02-01), Fransworth et al.
patent: 4459539 (1984-07-01), Cordy
patent: 4536700 (1985-08-01), Bello et al.
patent: 4591963 (1986-05-01), Retotar
patent: 4618812 (1986-10-01), Kawakami
patent: 4668905 (1987-05-01), Schierjott
patent: 4717994 (1988-01-01), Diaz et al.
Patent Abstracts of Japan, vol. 6, No. 21 (E-93), (899), Feb. 6, 1982.
"Halbleiterschaltungstechnik" (Semiconductor Circuitry), by Tietze and Schnek, 5th Edition, Chapter 16.5.1.
Obergfell Rainer
Panse Hubert
Schlegel Wolfgang
Beha Jr. William H.
Morris Jeffrey P.
Siemens Aktiengesellschaft
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