Hybrid regulator

Details Hybrid regulator Hybrid regulator

1999-02-17

2000-10-10

Han, Jessica

Electricity: power supply or regulation systems

Output level responsive

Using a three or more terminal semiconductive device as the...

323272, 323277, G05F 140

Patent

active

061305251

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a regulator in which a switching regulator and a series regulator are inter-connected, and more particularly to a "hybrid" regulator configured to utilize the advantage of a series regulator, namely, a superior regulation performance having no ripple even when a variation in load occurs, and to utilize the advantage of a switching regulator, namely, high efficiency.
2. Description of the Prior Art
In accordance with the advent of Green Round, many efforts to reduce the absolute quantity of energy used have recently been made in a variety of technical fields. Such efforts have also been made in conjunction with electronic and electrical appliances. In addition to such efforts, another effort has been made to increase the efficiency of energy used, thereby minimizing a loss of energy.
Meanwhile, all electronic appliances, electrical appliances, electric home appliances and a variety of industrial electronic appliances, which are currently used, essentially require a stable power supply, namely, DC--DC converter. Most appliances, in which electronic circuits are included, use a stable DC power such as +5V DC, +12V DC or +15V DC in general.
For electronic devices such as IC's, transistors, lamps, etc., a maximum allowable voltage is set. When an electronic device is supplied with the voltage greater than its maximum allowable voltage, it may be damaged or reduced in use life. Where an operational amplifier or comparator is used to amplify signals having a low amplitude or to compare such signals, a variation in voltage occurring in an external power supply adapted to supply voltage to the circuit may cause the malfunction of the circuit, thereby resulting in a degradation in the accuracy or stability. In addition to developments of electronic devices having high accuracy, therefore, developments of stable power supply devices are also important.
Generally, a regulator is a device for maintaining output voltage or current in a strong and uniform state irrespective of a variation in input or output load. Regulators currently used are mainly classified into switching regulators and series regulators. The series regulator is generally used when the good regulation performance without ripple is needed. On the other hand, the switching regulator is used to obtain high efficiency while reducing in size.
Referring to FIG. 1, an example of a series regulator is illustrated. The series regulator is also called a "linear regulator" or "dropper regulator". This regulator has an advantage of an excellent output-voltage regulation and a disadvantage of a poor power transformation efficiency. In this regard, the series regulator is suitable for the case in which a prominent regulation but low electric power is required. Since such a series regulator is controlled in a voltage series feedback scheme while having no delay element (for example, an inductor connected in series to the regulator, or a capacitor connected in parallel to the regulator) arranged on its main power supply path, it inherently has a superior regulation performance in steady state as well as transient state condition.
In the series regulator shown in FIG. 1, a "differential voltage" between an external supply voltage Vdd and an output voltage Vo observed in load resistor R4 is applied between the collector and emitter of an output transistor Q1. In this state, the same amount of current as that required for the load resistor R4 is supplied to the emitter of the output transistor Q1 via the collector of the output transistor Q1. For this reason, this series regulator exhibits a poor power efficiency.
In this case, the power used in the load resistor R4 is expressed by the following expression (1) whereas the power loss in the output transistor Q1 is expressed by the following expression (2): .times.I.sub.R4[Expression 2]
In order to reduce the power loss in the transistor Q1, expressed by Expression (2), it is required to decrease the voltage V.sub.CE applied between th

REFERENCES:
patent: 4881023 (1989-11-01), Perusse et al.
patent: 5216351 (1993-06-01), Shimoda
patent: 5592072 (1997-01-01), Brown
patent: 5864225 (1999-01-01), Bryson

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