Electricity: power supply or regulation systems – Output level responsive – Using a three or more terminal semiconductive device as the...
Reexamination Certificate
2002-03-28
2003-07-29
Sterrett, Jeffrey (Department: 2838)
Electricity: power supply or regulation systems
Output level responsive
Using a three or more terminal semiconductive device as the...
C323S270000, C323S298000
Reexamination Certificate
active
06600297
ABSTRACT:
This patent application claims priority from a Japanese patent application No. 2001-096414 filed on Mar. 29, 2001, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a power supply unit. More particularly, the present invention relates to a power supply unit with a series regulator (dropper type power supply).
2. Description of the Related Art
A series regulator (dropper type power supply) is known as a power supply unit that changes an input direct current (DC) voltage input from a DC power supply into a stabilized output DC voltage.
This series regulator changes the input DC voltage to the stabilized output DC voltage that is lower than the input DC voltage.
This series regulator, however, converts a power loss generated by voltage drop between an input and an output of a semiconductor device such as a transistor, used as a three-terminal regulator device serving as a main controlling device, into heat. Thus, in a case where the voltage drop is large, the power loss in the semiconductor device also becomes large, thereby reducing the reliability of the entire product.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide a power supply unit, which is capable of overcoming the above drawbacks accompanying the conventional art. The above and other objects can be achieved by combinations described in the independent claims. The dependent claims define further advantageous and exemplary combinations of the present invention.
According to the first aspect of the present invention, a power supply unit having a series regulator that changes an input DC voltage input from a DC power supply into a stabilized output DC voltage lower than the input DC voltage, comprises: a power consuming unit, provided on a direct current path between the DC power supply and an input side of the series regulator, including a parallel circuit formed by a first fixed resistor and a semiconductor device having a current input, a current output and a setting input; and a current setting unit operable to set an amount of a current flowing between the current input and the current output of the semiconductor device, wherein the current input of semiconductor device is arranged on a DC-power-supply side thereof, the current output of the semiconductor device is arranged on a series-regulator side thereof, and the setting input of the semiconductor device is connected to a setting output of the current setting unit.
According to the second aspect of the present invention, a power supply unit having a series regulator that changes an input DC voltage input from a DC power supply into a stabilized output DC voltage lower than the input DC voltage, comprises: a first power consuming unit, provided in parallel to the series regulator, including a parallel circuit formed by a first fixed resistor and a first semiconductor device having a current input, a current output and a setting input; and a first current setting unit operable to set an amount of a current flowing between the current input and the current output of the first semiconductor device, wherein the current input of the first semiconductor device is arranged on a series-regulator-input side thereof, the current output of the first semiconductor device is arranged on a series-regulator-output side thereof, and the setting input of the first semiconductor device is connected to a setting output of the first current setting unit.
The power supply unit may further comprise: a second power consuming unit, provided on a direct current path between the DC power supply and the input of the series regulator, having a parallel circuit formed by a second fixed resistor and a second semiconductor device; and a second current setting unit operable to set an amount of a current flowing between a current input and a current output of the second semiconductor device, wherein the current input of the second semiconductor device is arranged on a DC-power-supply side thereof, the current output of the second semiconductor device is arranged on a series-regulator side thereof, and a setting input of the second semiconductor device is connected to a setting output of the second current setting unit.
In the power supply unit according to the first or second aspect of the present invention, the power consuming unit or the first or second power consuming unit may include the third fixed resistor connected to the semiconductor device in series in the parallel circuit.
In the power supply unit according to the first or second aspect of the present invention, the power consuming unit or the first or second power consuming unit may include the fourth fixed resistor connected to the parallel circuit in series.
In the power supply unit according to the first or second aspect of the present invention, the power consuming unit or the first or second power consuming unit may include a plurality of parallel circuits connected in series. Alternatively, the power consuming unit or the first or second power consuming unit may include a plurality of parallel circuits connected in parallel.
The current setting unit in the power supply unit of the first aspect of the present invention may set the amount of the current flowing through the semiconductor device by regulating a bias of the setting input of the semiconductor device. In this case, the current setting unit may include a changing unit operable to change the bias. Also, in this case, the current setting unit may regulate the bias by using a divided voltage generated by a plurality of resistor devices connected in series between the input DC voltage input from the DC power supply and a predetermined reference voltage.
Moreover, in this case, the current setting unit may use a voltage that regulates the output DC voltage of the series regulator as the predetermined reference voltage. Furthermore, the current setting unit may include a Zener diode that regulates the bias in this case.
The current setting unit may include a feedback circuit connected to the current output of the semiconductor device and an amplifying circuit having an input connected to the feedback circuit, another input to which the predetermined reference voltage is applied and an output connected to the setting input of the semiconductor device.
It is preferable that the current setting unit set the amount of the current flowing through the semiconductor device to make the amount of heat generated in the semiconductor device during an actual operation approximately equal to the amount of heat generated in the series regulator.
The first or second current setting unit in the power supply unit of the second aspect of the present invention may set the amount of the current flowing through the corresponding semiconductor device by regulating a bias of the setting input of the corresponding semiconductor device. In this case, the first or second current setting unit may include a changing unit operable to change the bias. Also, in this case, the first or second current setting unit may regulate the bias by using a divided voltage generated by a plurality of resistor devices connected in series between the input DC voltage input from the DC power supply and a predetermined reference voltage.
Moreover, in this case, the first or second current setting unit may use a voltage that regulates the output DC voltage of the series regulator as the predetermined reference voltage. Furthermore, the first or second current setting unit may include a Zener diode that regulates the bias in this case.
The first or second current setting unit may include a feedback circuit connected to the current output of the corresponding semiconductor device and an amplifying circuit having an input connected to the feedback circuit, another input to which the predetermined reference voltage is applied and an output connected to the setting input of the corresponding semiconductor device.
It is preferable that the first or second current setting unit set the amount of cu
Ito Masayasu
Suzuki Tomokazu
Takeda Hitoshi
Koito Manufacturing Co. Ltd.
Rosenthal & Osha L.L.P.
Sterrett Jeffrey
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