Electricity: power supply or regulation systems – Output level responsive – Using a three or more terminal semiconductive device as the...
Reexamination Certificate
2000-03-09
2001-02-06
Han, Jessica (Department: 2838)
Electricity: power supply or regulation systems
Output level responsive
Using a three or more terminal semiconductive device as the...
C323S286000
Reexamination Certificate
active
06184667
ABSTRACT:
The present invention relates to a means of converting direct current (DC) voltages and to a DC/DC converter for generating non-isolated low voltage, regulated power from a relatively higher voltage source.
The requirement for conversion of DC voltages from a higher voltage to a lower fixed voltage is common in electronic systems. The higher voltage input may be fixed or variable and a DC/DC converter is used to provide a regulated lower voltage output under a variety of load conditions.
Previously known DC/DC converters have employed two main techniques for this conversion. Linear regulation, in which a linear regulator drops the required voltage differential between the input and output across a series element, and switch regulation, where a switching regulator varies the duty cycle of a series switch. A filter circuit to give a regulated output voltage averages the voltage produced by the switching regulator.
The main disadvantage of linear regulation is that the efficiencies are low. For example in a telephone application the source voltage is typically 48V and the corresponding regulated output is 5V. The efficiency here will be just over 10%.
Switch regulation converters are more efficient however, the circuit is generally more complex. Costs are higher and the switching regulator frequently produces unacceptable levels of signal noise. A further problem arises in that conventional switching regulators also present a negative impedance to the source which may cause “latch-up” under certain conditions.
It is an object of the present invention to overcome the above-mentioned disadvantages and to provide an improved DC/DC converter.
Prior art converters such as those shown in U.S. Pat. No. 4,791,350 (Square D), EP 0 496 529 and U.S. Pat. No. 4,929,882 all provide converters which are useful for certain applications. These converters do not however present a positive impedence to the source. The absence of this positive impedence can in many situation cause unacceptable latching of the converter. Additionally the proposed converters are complex and use an excessive number of components significantly improving costs.
Accordingly there is provided a DC/DC converter for converting an unregulated DC signal to a regulated DC signal, the converter including a switching regulator circuit of the type having:
a switching means for switching an unregulated DC signal received at a converter input;
a current sense amplifier for modulating the switching means;
a hysteresis generator for modulating the current sense amplifier; and
an output circuit for controlling delivery of a regulated DC signal to a converter output,
characterised in that the switching means is formed to
deliver a substantially constant signal to the current sense amplifier,
present a positive impedence to the source to prevent latching and the hysteresis generator is formed to provide positive switching of the switching circuit using a current limit transistor.
Preferably the hysteresis generator operates to control a current limit value in response to a variation in the unregulated DC signal.
In a preferred arrangement the output circuit includes an output filter and a shunt regulator.
According to one aspect of the invention there is provided a DC/DC converter for use in a telecommunication system the converter including a switching regulator circuit having:
a switching means formed for connection to a telephone line power feed voltage source;
a switching means formed for connection to a telephone line power feed voltage source;
a current sense amplifier for modulating the switching means;
a hysteresis circuit for modulating the current amplifier; and
an output circuit for controlling regulated voltage supply for telecommunications logic circuitry,
wherein the switching means includes a filter for attenuating switching noise induced on the telephone line.
Preferably the switching regulator circuit incorporates means for presenting a high impedance to the source for reducing line interference.
Preferably the converter is formed for connection to a telecommunications switch.
According to a further aspect of the invention there is provided a DC/DC converter for use with a controller the converter including a switching regulator circuit having:
a switching means for connecting the controller to an unregulated DC voltage source;
a current sense amplifier for modulating the switching means;
a hysteresis generator for modulating the current amplifier; and
an output circuit for controlling a regulated voltage supply for the controller the switching circuit being formed to provide a low voltage output and a high voltage output from an unregulated rectified mains voltage.
In a preferred embodiment of the invention the hysteresis generator includes hysteresis resistors, an output choke providing a switching current source.
According to another aspect of the invention there is provided an improved DC/DC converter having a switching regulator circuit, for converting an unregulated DC voltage to a regulated DC voltage, comprising:
a switching means for switching the unregulated DC voltage;
a current sense amplifier for modulating the switching means;
a hysteresis generator for modulating the current sense amplifier; and
an output circuit for controlling the regulated DC voltage,
in which current passing through the current sense amplifier is kept substantially constant by the modulation of the switching means.
The hysteresis generator is operable to ensure switching occurs and that such switching is positive. The hysteresis generator is further operable to vary a current limit value corresponding to variations in the unregulated voltage. This arrangement provides a positive impedance (resistance) to the unregulated voltage source.
Current passing through the current sense amplifier is fed to the output circuit which comprises an output filter and a shunt regulator. Excess current from the filter is diverted into the shunt regulator to keep the regulated output voltage (substantially) constant.
The present invention further provides a DC/DC converter having a switching regulator circuit for use in a telecommunications or similar device, the circuit comprising:
a switching means for connecting to a telephone line power feed voltage source;
a current sense amplifier for modulating the switching means;
a hysteresis circuit for modulating the current amplifier; and
an output circuit for controlling regulated voltage supply for telecommunications logic circuitry,
in which filter components are connected to the switching means to attenuate switching noise induced on the telephone line and to present a high positive impedance (resistance) to the source to attenuate or eliminate interference on the line.
The above arrangement provides a circuit, which induces less heating in the telecommunications device, such as a peripheral device.
The above arrangement further provides a circuit of enhanced efficiency which draws significantly less power from the telecommunications device thereby decreasing the required power rating of the associated power supply unit.
In such an arrangement, where the telecommunications device is connected to a Private Automatic Branch Exchange (PABX), the power drawn from the PABX power supply unit by the regulator circuit of the present invention may be as little as 25% of power drawn by prior art circuits. Consequently, capital and running costs of the telecommunications device are reduced.
The present invention also provides a DC/DC converter having a switching regulator circuit for use with controller device such as a motor drive controller, the circuit comprising:
a switching means for connecting the controller to an unregulated DC voltage source;
a current sense amplifier for modulating the switching means;
a hysteresis generator for modulating the current amplifier; and
an output circuit for controlling a regulated voltage supply for the controller device.
The circuit provides a first low voltage output and a second high voltage output from an unregulated, rectified mains voltage.
The low voltage output is su
Han Jessica
Hoffman & Baron LLP
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