Title of Invention	ENHANCING THE EFFICIENCY OF AC-DC LOW VOLTAGE POWER SUPPLIES BY TOPOLOGICAL MODIFICATIONS
Abstract	The present invention relates to improvements in or relating to power supplies, and more particularly, although not exclusively, relates to power supplies for utility meters. In order to operate a low voltage source from a mains voltage power supply, such as an electricity meter, the alternating current (AC) mains voltage must first be converted to direct current (DC). In common practice in low cost power supplies make use of a very simple arrangement of components to reduce the high ac voltage to a lower useable dc voltage. Such systems operating in a half wave rectification mode to reduce the circuit component numbers. This makes for inefficient DC voltage supplies. The present invention seeks to address a need to increase an amount of available electrical energy to operate the low voltage circuit requirements of an electricity meter without increasing the energy taken from the mains voltage. The present invention provides a power supply of which both cycles of an input alternating current are employed through the use of an inductor based circuit.

Title of Invention

ENHANCING THE EFFICIENCY OF AC-DC LOW VOLTAGE POWER SUPPLIES BY TOPOLOGICAL MODIFICATIONS

Abstract

The present invention relates to improvements in or relating to power supplies, and more particularly, although not exclusively, relates to power supplies for utility meters. In order to operate a low voltage source from a mains voltage power supply, such as an electricity meter, the alternating current (AC) mains voltage must first be converted to direct current (DC). In common practice in low cost power supplies make use of a very simple arrangement of components to reduce the high ac voltage to a lower useable dc voltage. Such systems operating in a half wave rectification mode to reduce the circuit component numbers. This makes for inefficient DC voltage supplies. The present invention seeks to address a need to increase an amount of available electrical energy to operate the low voltage circuit requirements of an electricity meter without increasing the energy taken from the mains voltage. The present invention provides a power supply of which both cycles of an input alternating current are employed through the use of an inductor based circuit.

Full Text	Field of Invention The present invention relates to improvements in or relating to power supplies, and more particularly, although not exclusively, relates to power supplies for utility meters such as power supplies that are commonly used in electricity meters. Background to the Invention In order to operate a low voltage electrical component from a mains voltage power supply, such as an electricity meter, the alternating current (AC) mains voltages must first be converted to direct current (DC). It is common practice in low cost power supplies to make use of a very simple arrangement of components to reduce the high AC voltage to a lower useable DC voltage, such systems operating in a half wave rectification mode to reduce the circuit component numbers. Figure 1 shows a simple circuit wherein a capacitor is selected such that it has an impedance at the AC voltage frequency that can be used to reduce the AC voltage frequency, whereby the effective AC voltage is reduced. Specifically, a first capacitor C11 has a value chosen such that its impedance at the supply voltage frequency will reduce the supply voltage. During the positive half cycle of the AC waveform, a first diode D11 conducts and allows current to flow to charge up the first capacitor C11. A DC voltage is thereby developed across the first capacitor C11, which can be used for a DC load. During the subsequent negative half cycle, a second diode D12 conducts and removes the charge from the first capacitor C11, so that it can again be used during the next positive half cycle. Whilst this provides the basis for a very simple DC supply, where only a single positive DC voltage rail is provided, it is important to realize that during the negative half cycle, all energy flowing through the second diode D12 is effectively wasted and cannot provide any form of useful energy to enable operation of the electronics of a low voltage circuit. Accordingly, apart from any intrinsic heat wastage through circuit components, there is automatically a sub-50% level of efficiency within the circuitry. It is possible to make use of the power in the negative half cycle and this is commonly demonstrated in circuits that have a 'split' or positive and negative DC power supply rails. Figure 2 shows a simple alternative circuit where two DC voltages are developed; additional to the circuit components of Figure 1 a third capacitor C23 is connected to a second diode D22. During the negative half cycle of the AC supply voltage, the current flow through the second diode D22 removes charge from the third capacitor C23 and causes a negative DC voltage to be developed across the third capacitor, C23. However, if the remainder of the electronic circuitry cannot be configured so that it operates from a split rail DC supply, then the use of this circuit topology is not appropriate. To address such an inherent inefficiency, simple full wave rectification circuits have been developed. This can be conventionally accomplished by passing the mains voltage AC input to a full wave bridge rectifier, smoothing the output with, for example, an electrolytic capacitor, and then regulating the output voltage with, for example, a zener diode. Whilst this technique works reasonably well with a filament transformer and the like, it is either highly inefficient or is incapable of providing adequate power for many low power circuits. Notwithstanding the above, one problem associated with conventional.full wave bridge rectification of incoming alternating current is that considerable amounts of heat can be generated. This extra heat generated flows to the rest of the circuit through conduction within components such as the leads thereof, and, where space permits, through convection. Not only does the heat affect other components, it also indicates that the bridge rectifier is wasting energy. Component, life can also be reduced. Another consideration to be taken into account is the fact that a voltage drop across the diodes of a conventional bridge rectifier also reduces the output voltage available to drive a low voltage circuit such as a utility meter measuring circuit. Utilil y meter measuring circuits are typically situated within the confines of a small enclosure: wherein excess heat generated by a conventional bridge rectifier circuit can also affect normal operation. Utility meter measuring circuits are rated for operation at a specific ambient temperature and current. If they are operated at higher than their typical temperature, the utility meter accuracy may be compromised. Furthermore, operating any equipment at other than its rated temperature will have an effect on it is operating longevity. Object of the Invention It is therefore an object of the present invention to provide an improved DC low voltage power supply. It is also an object of the present invention to provide an increased efficiency DC low voltage power supply. In another aspect, the present invention seeks to address a need to increase an amount of available electrical energy to operate low voltage circuit requirements of an electricity meter without increasing the energy taken from the mains voltage. Statement of Invention In accordance with a first aspect of the invention, there is provided a power supply circuit for the conversion of mains alternating current voltage received at first and second input terminals to provide a direct current voltage at first and second output terminals, the first input terminal having a first capacitor coupled in series with a first diode and connected thereto by an output voltage rail to the first output terminal; the second input terminal being coupled to a common voltage rail, which rail is connected to the second output terminal; wherein an inductor in series with a second diode couples the common voltage rail to a node between the first capacitor and the first diode on the output voltage rail and the inductor couples with an input of a third diode in series, the third diode being connected to an output of the first dioc e; and wherein a second capacitor couples the common voltage rail to an output of the third diode; whereby a DC reduced voltage output is provided between the first output terminal and the second output terminal. A switch can be placed between the inductor and second diode, the switcn being operable to pulse the signal through the inductor from the earth voltage line. This switch is conveniently fabricated as a transistor based switch and can receive DC pulses from a signal generator, whereby truncated pulses can be output from the inductor. The switch transistor can be a FET or BJT transistor. In accordance with a further aspect of the invention, there is provided a method of operating a power supply made in accordance with the invention. In accordance with a still further aspect of the invention, there is provided a utility meter comprising a power supply made in accordance with the invention. In accordance with another aspect of the invention there is provided an electricity meter having a power supply, as described above, and wherein the power supply connects directly to metered mains voltage supply. An advantage arising form the increase in efficiency, as provided by the present invention, is that there is a reduction in the amount of energy taken from the mains AC voltage supply while maintaining the same low DC voltage supply available for use within the meter. A further advantage arises from a reduction in the power consumption of the electronic circuitry within the meter is that there is a cumulative environmental impact given that, whilst only small savings in the power consumption are made per meter this could add up to a large energy saving when viewed over a large installed population. This invention is particularly advantageous to the manufacture of low cost electricity meters where the material cost of the power supplies has to be kept to a minimum. Brief Description of the Figures For a better understanding of the present invention, reference will now be made, by way of example only, to the Figures as shown in the accompanying drawing sheets, wherein:- Figure 1 illustrates a first prior art DC voltage supply; Figure 2 illustrates a second prior art DC voltage supply; Figure 3 illustrates a first power supply, made in accordance with the present invention; Figure 4 represents a second power supply, made in accordance with the present invention; and Figure 5 shows actual values of duty cycle versus AC input voltage obtained for a constant 10mA load DC output. Detailed description of the Preferred Embodiments There will now be described, by way of example only, the best mode contemplated by the inventor for carrying out the present invention. In the following description, numerous specific details are set out in order to provide a complete understanding to the present invention, it will be apparent to those skilled in the art that the present invention may be put into practice with variations of the specific. With reference to Figure 3, there is shown a first embodiment of the invention. In this circuit, a first capacitor C31 is used with a first diode D31 and second capacitor C32 to form a DC voltage supply. Second diode D32 is configured in the circuit so that it will conduct during the negative half-cycle such that the circuit operates in similar fashion to the circuit shown with reference to Figure 1. During the negative half-cycle, current from second diode D32 flows through inductor L31 storing energy, which is released via a third diode D33 when second diode D32 is non-conducting in the positive half-cycle of the AC mains supply. The second capacitor C32 is therefore not only charged during the positive half-cycle from first diode Dl but is additionally charged due to energy being released by inductor L31 via third diode D3. One constraint imposed by the above circuit is that the inductor L31 is a relatively large circuit component in order for the circuit to operate at AC supply frequency (50-60Hz). Furthermore, the expense of such a component may also be viewed as being disproportionate in relation to the circuit as a whole. Referring now to Figure 4, a further embodiment of the invention is shown. The size and cost of a conductor can be considerably reduced if the current is pulsed or "chopped". This may be achieved by a switching device Q1 which is pulsed from an external source. In this circuit as described above, the first capacitor C41 is used with first diode D41 and second capacitor C42 to form a DC voltage. Second diode D42 is configured in the circuit so that it will conduct during the negative half-cycle as discussed above in relation to the circuit of Figure 1. The switching device, in this case a transistor, Q1 is arranged such that it conducts in a normal state. The signal source can be either an oscillator or an output port from the microcontroller with appropriate level-shifting. When the negative half-cycle current from second diode D42 flows through inductor L41 and transistor Q1, initially the circuit functions exactly as Figure 1 with the loss of negative half-cycle of the AC supply, However, when high frequency pulses are then applied to the switching device Q1, the switching device turns off and on and consequently "chops" the current flowing through the inductor L41. The store i energy in inductor L41 is thereby released via third diode D43 when transistor Q1 is in a non-conducting state during the negative half- cycle of the AC mains supply, whereby second capacitor C42 is not only charged during the positive half-cycle of the AC mains supply from first diode D41 but is also additionally charged due to the pulses of energy released by inductor L41 and transistor Q1 via third diode D43 during the negative AC mains supply cycle. Chosen values for experimentation, which have been shown to perform well, are as follows: C41 - 330nF D42, D42-1000PIV, 1A D43 - 100V PIV fast switching diode (e.g. BASI6 etc.) Q1 - BC846NPN bipolar junction transistor L41 - 47mH C42-470uF DC Pulses - 5 kHz'PWM signal (pulse-width varies, dependent upon load current). Figure 5 shows the actual values for duty cycle versus the AC input voltage obtained for a constant 10mA load and 9.2V DC output. Measurements (simulated) have been taken with respect to the standard circuit shown in Figure 1 gave 6mA load current maximum for 230VAC input and 3mA max for 138VAC input for a 10V DC output for both cases. Simulation results indicate that for a 138V AC input without the current boost, the power supply will deliver 3mA at 10V DC and when current boost is enabled, it will deliver 10mA at 10V DC. That is to say a three-fold increase in output power can be realised. It will be appreciated that this has a significant impact upon the overall efficiency of the circuit. Although the specific embodiments above have been described in relation to a power supply for a utility meter, it will be appreciated that the same of circuit is equally applicable to many other low voltage circuits, where the use of electrical cells is inconvenient or that there is a more readily accessible mains electrical supply. WE CLAIM : 1. A power supply circuit for the conversion of mains alternating current voltage received at first and second input terminals (IP1, IP2) to provide a direct current voltage at first and second output terminals (OP1, OP2), whereby a DC voltage s provided between the first output terminal (OP1) and the second output terminal(OP2), the first input terminal (IP1) having a first capacitor (C31) coupled in series with a first diode (D31) and connected thereto by an output voltage rail to the first output terminal (OP1), the second input terminal (IP2) being coupled to a common voltage rail, which rail is connected to the second output terminal (OP2), wherein an inductor (L31) couples in series with a second diode (D32) the common voltage rail to a node between the first capacitor (C31) and the first diode (D31) on the output voltage rail, characterised in that the inductor (L31) couples with an input of a third diode (D33) in series, the third diode (D33) being connected to an output of first the diode (D31); and wherein a second capacitor (C32) couples the common voltage rail to an output of third diode (D33). 2. A power supply according to claim one, wherein a switch (Q1) is placed between the inductor (L41) and second diode (D42), the switch being operable to pulse the signal through the inductor (L41) from the common voltage rail. 3. A power supply according to claim two wherein the switch is a transistor and receives DC pulses from a signal generator, whereby truncated pulses can be output from the inductor (L41). 4. A power supply according to claim three, wherein the switch is a transistor switch selected from a set including BJT and FET transistors. 5. A power supply as claimed in claims 1 to 4 for use in utility meter which is either an electricity meter or a gas meter wherein the power supply connects directly to metered mains voltage supply.and the power supply of the utility meter connects with a mains supply voltage. ABSTRACT TITLE: ENHANCING THE EFFICIENCY OF AC-DC LOW VOLTAGE POWER SUPPLIES BY TOPOLOGICAL MODIFICATIONS The present invention relates to improvements in or relating to power supplies, and more particularly, although not exclusively, relates to power supplies for utility meters. In order to operate a low voltage source from a mains voltage power supply, such as an electricity meter, the alternating current (AC) mains voltage must first be converted to direct current (DC). In common practice in low cost power supplies make use of a very simple arrangement of components to reduce the high ac voltage to a lower useable dc voltage. Such systems operating in a half wave rectification mode to reduce the circuit component numbers. This makes for inefficient DC voltage supplies. The present invention seeks to address a need to increase an amount of available electrical energy to operate the low voltage circuit requirements of an electricity meter without increasing the energy taken from the mains voltage. The present invention provides a power supply of which both cycles of an input alternating current are employed through the use of an inductor based circuit.

Full Text

Field of Invention
The present invention relates to improvements in or relating to power
supplies, and more particularly, although not exclusively, relates to power supplies
for utility meters such as power supplies that are commonly used in electricity meters.
Background to the Invention
In order to operate a low voltage electrical component from a mains voltage
power supply, such as an electricity meter, the alternating current (AC) mains voltages
must first be converted to direct current (DC). It is common practice in low cost power
supplies to make use of a very simple arrangement of components to reduce the high
AC voltage to a lower useable DC voltage, such systems operating in a half wave
rectification mode to reduce the circuit component numbers.
Figure 1 shows a simple circuit wherein a capacitor is selected such that it
has an impedance at the AC voltage frequency that can be used to reduce the AC
voltage frequency, whereby the effective AC voltage is reduced. Specifically, a first
capacitor C11 has a value chosen such that its impedance at the supply voltage
frequency will reduce the supply voltage. During the positive half cycle of the AC
waveform, a first diode D11 conducts and allows current to flow to charge up the first
capacitor C11. A DC voltage is thereby developed across the first capacitor C11,
which can be used for a DC load. During the subsequent negative half cycle, a
second diode D12 conducts and removes the charge from the first capacitor C11, so
that it can again be used during the next positive half cycle. Whilst this provides the
basis for a very simple DC supply, where only a single positive DC voltage rail is
provided, it is important to realize that during the negative half cycle, all energy
flowing through the second diode D12 is effectively wasted and cannot provide any
form of useful energy to enable operation of the electronics of a low voltage circuit.
Accordingly, apart from any intrinsic heat wastage through circuit components, there
is automatically a sub-50% level of efficiency within the circuitry.
It is possible to make use of the power in the negative half cycle and this is
commonly demonstrated in circuits that have a 'split' or positive and negative DC
power supply rails. Figure 2 shows a simple alternative circuit where two DC voltages

are developed; additional to the circuit components of Figure 1 a third capacitor C23
is connected to a second diode D22. During the negative half cycle of the AC supply
voltage, the current flow through the second diode D22 removes charge from the
third capacitor C23 and causes a negative DC voltage to be developed across the
third capacitor, C23. However, if the remainder of the electronic circuitry cannot be
configured so that it operates from a split rail DC supply, then the use of this circuit
topology is not appropriate. To address such an inherent inefficiency, simple full
wave rectification circuits have been developed. This can be conventionally
accomplished by passing the mains voltage AC input to a full wave bridge rectifier,
smoothing the output with, for example, an electrolytic capacitor, and then regulating
the output voltage with, for example, a zener diode. Whilst this technique works
reasonably well with a filament transformer and the like, it is either highly inefficient or
is incapable of providing adequate power for many low power circuits.
Notwithstanding the above, one problem associated with conventional.full
wave bridge rectification of incoming alternating current is that considerable amounts
of heat can be generated. This extra heat generated flows to the rest of the circuit
through conduction within components such as the leads thereof, and, where space
permits, through convection. Not only does the heat affect other components, it also
indicates that the bridge rectifier is wasting energy. Component, life can also be
reduced.
Another consideration to be taken into account is the fact that a voltage drop
across the diodes of a conventional bridge rectifier also reduces the output voltage
available to drive a low voltage circuit such as a utility meter measuring circuit. Utilil y
meter measuring circuits are typically situated within the confines of a small
enclosure: wherein excess heat generated by a conventional bridge rectifier circuit
can also affect normal operation. Utility meter measuring circuits are rated for
operation at a specific ambient temperature and current. If they are operated at
higher than their typical temperature, the utility meter accuracy may be compromised.
Furthermore, operating any equipment at other than its rated temperature will have
an effect on it is operating longevity.

Object of the Invention
It is therefore an object of the present invention to provide an improved DC
low voltage power supply.
It is also an object of the present invention to provide an increased efficiency
DC low voltage power supply.
In another aspect, the present invention seeks to address a need to increase
an amount of available electrical energy to operate low voltage circuit requirements
of an electricity meter without increasing the energy taken from the mains voltage.
Statement of Invention
In accordance with a first aspect of the invention, there is provided a power
supply circuit for the conversion of mains alternating current voltage received at first
and second input terminals to provide a direct current voltage at first and second
output terminals, the first input terminal having a first capacitor coupled in series with
a first diode and connected thereto by an output voltage rail to the first output
terminal; the second input terminal being coupled to a common voltage rail, which rail
is connected to the second output terminal; wherein an inductor in series with a
second diode couples the common voltage rail to a node between the first capacitor
and the first diode on the output voltage rail and the inductor couples with an input of
a third diode in series, the third diode being connected to an output of the first dioc e;
and wherein a second capacitor couples the common voltage rail to an output of the
third diode; whereby a DC reduced voltage output is provided between the first
output terminal and the second output terminal.
A switch can be placed between the inductor and second diode, the switcn
being operable to pulse the signal through the inductor from the earth voltage line.
This switch is conveniently fabricated as a transistor based switch and can receive
DC pulses from a signal generator, whereby truncated pulses can be output from the
inductor. The switch transistor can be a FET or BJT transistor.

In accordance with a further aspect of the invention, there is provided a
method of operating a power supply made in accordance with the invention.
In accordance with a still further aspect of the invention, there is provided a
utility meter comprising a power supply made in accordance with the invention.
In accordance with another aspect of the invention there is provided an
electricity meter having a power supply, as described above, and wherein the power
supply connects directly to metered mains voltage supply.
An advantage arising form the increase in efficiency, as provided by the
present invention, is that there is a reduction in the amount of energy taken from the
mains AC voltage supply while maintaining the same low DC voltage supply available
for use within the meter.
A further advantage arises from a reduction in the power consumption of the
electronic circuitry within the meter is that there is a cumulative environmental impact
given that, whilst only small savings in the power consumption are made per meter
this could add up to a large energy saving when viewed over a large installed
population.
This invention is particularly advantageous to the manufacture of low cost
electricity meters where the material cost of the power supplies has to be kept to a
minimum.
Brief Description of the Figures
For a better understanding of the present invention, reference will now be
made, by way of example only, to the Figures as shown in the accompanying
drawing sheets, wherein:-
Figure 1 illustrates a first prior art DC voltage supply;
Figure 2 illustrates a second prior art DC voltage supply;

Figure 3 illustrates a first power supply, made in accordance with the present
invention;
Figure 4 represents a second power supply, made in accordance with the
present invention; and
Figure 5 shows actual values of duty cycle versus AC input voltage obtained
for a constant 10mA load DC output.
Detailed description of the Preferred Embodiments
There will now be described, by way of example only, the best mode
contemplated by the inventor for carrying out the present invention. In the following
description, numerous specific details are set out in order to provide a complete
understanding to the present invention, it will be apparent to those skilled in the art
that the present invention may be put into practice with variations of the specific.
With reference to Figure 3, there is shown a first embodiment of the
invention. In this circuit, a first capacitor C31 is used with a first diode D31 and
second capacitor C32 to form a DC voltage supply. Second diode D32 is configured
in the circuit so that it will conduct during the negative half-cycle such that the circuit
operates in similar fashion to the circuit shown with reference to Figure 1. During the
negative half-cycle, current from second diode D32 flows through inductor L31
storing energy, which is released via a third diode D33 when second diode D32 is
non-conducting in the positive half-cycle of the AC mains supply. The second
capacitor C32 is therefore not only charged during the positive half-cycle from first
diode Dl but is additionally charged due to energy being released by inductor L31 via
third diode D3.
One constraint imposed by the above circuit is that the inductor L31 is a
relatively large circuit component in order for the circuit to operate at AC supply
frequency (50-60Hz). Furthermore, the expense of such a component may also be
viewed as being disproportionate in relation to the circuit as a whole.

Referring now to Figure 4, a further embodiment of the invention is shown.
The size and cost of a conductor can be considerably reduced if the current is pulsed
or "chopped". This may be achieved by a switching device Q1 which is pulsed from
an external source. In this circuit as described above, the first capacitor C41 is used
with first diode D41 and second capacitor C42 to form a DC voltage. Second diode
D42 is configured in the circuit so that it will conduct during the negative half-cycle as
discussed above in relation to the circuit of Figure 1. The switching device, in this
case a transistor, Q1 is arranged such that it conducts in a normal state. The signal
source can be either an oscillator or an output port from the microcontroller with
appropriate level-shifting.
When the negative half-cycle current from second diode D42 flows through
inductor L41 and transistor Q1, initially the circuit functions exactly as Figure 1 with
the loss of negative half-cycle of the AC supply, However, when high frequency
pulses are then applied to the switching device Q1, the switching device turns off and
on and consequently "chops" the current flowing through the inductor L41. The store i
energy in inductor L41 is thereby released via third diode D43 when transistor Q1 is
in a non-conducting state during the negative half- cycle of the AC mains supply,
whereby second capacitor C42 is not only charged during the positive half-cycle of
the AC mains supply from first diode D41 but is also additionally charged due to the
pulses of energy released by inductor L41 and transistor Q1 via third diode D43
during the negative AC mains supply cycle.
Chosen values for experimentation, which have been shown to perform well,
are as follows:
C41 - 330nF
D42, D42-1000PIV, 1A
D43 - 100V PIV fast switching diode (e.g. BASI6 etc.)
Q1 - BC846NPN bipolar junction transistor
L41 - 47mH
C42-470uF
DC Pulses - 5 kHz'PWM signal (pulse-width varies, dependent upon load current).

Figure 5 shows the actual values for duty cycle versus the AC input voltage
obtained for a constant 10mA load and 9.2V DC output. Measurements (simulated)
have been taken with respect to the standard circuit shown in Figure 1 gave 6mA
load current maximum for 230VAC input and 3mA max for 138VAC input for a 10V
DC output for both cases. Simulation results indicate that for a 138V AC input without
the current boost, the power supply will deliver 3mA at 10V DC and when current
boost is enabled, it will deliver 10mA at 10V DC. That is to say a three-fold increase
in output power can be realised. It will be appreciated that this has a significant
impact upon the overall efficiency of the circuit.
Although the specific embodiments above have been described in relation to
a power supply for a utility meter, it will be appreciated that the same of circuit is
equally applicable to many other low voltage circuits, where the use of electrical cells
is inconvenient or that there is a more readily accessible mains electrical supply.

WE CLAIM :
1. A power supply circuit for the conversion of mains alternating current voltage
received at first and second input terminals (IP1, IP2) to provide a direct current
voltage at first and second output terminals (OP1, OP2), whereby a DC voltage s
provided between the first output terminal (OP1) and the second output
terminal(OP2),
the first input terminal (IP1) having a first capacitor (C31) coupled in series with a first
diode (D31) and connected thereto by an output voltage rail to the first output
terminal (OP1),
the second input terminal (IP2) being coupled to a common voltage rail, which rail is
connected to the second output terminal (OP2),
wherein an inductor (L31) couples in series with a second diode (D32) the common
voltage rail to a node between the first capacitor (C31) and the first diode (D31) on
the output voltage rail,
characterised in that
the inductor (L31) couples with an input of a third diode (D33) in series, the third
diode (D33) being connected to an output of first the diode (D31); and
wherein a second capacitor (C32) couples the common voltage rail to an output of
third diode (D33).
2. A power supply according to claim one, wherein a switch (Q1) is placed
between the inductor (L41) and second diode (D42), the switch being operable to
pulse the signal through the inductor (L41) from the common voltage rail.
3. A power supply according to claim two wherein the switch is a transistor and
receives DC pulses from a signal generator, whereby truncated pulses can be output
from the inductor (L41).

4. A power supply according to claim three, wherein the switch is a transistor
switch selected from a set including BJT and FET transistors.
5. A power supply as claimed in claims 1 to 4 for use in utility meter which is
either an electricity meter or a gas meter wherein the power supply connects directly
to metered mains voltage supply.and the power supply of the utility meter connects
with a mains supply voltage.

ABSTRACT

TITLE: ENHANCING THE EFFICIENCY OF AC-DC LOW VOLTAGE
POWER SUPPLIES BY TOPOLOGICAL MODIFICATIONS
The present invention relates to improvements in or relating to power supplies,
and more particularly, although not exclusively, relates to power supplies for utility
meters. In order to operate a low voltage source from a mains voltage power supply,
such as an electricity meter, the alternating current (AC) mains voltage must first be
converted to direct current (DC). In common practice in low cost power supplies
make use of a very simple arrangement of components to reduce the high ac voltage
to a lower useable dc voltage. Such systems operating in a half wave rectification
mode to reduce the circuit component numbers. This makes for inefficient DC voltage
supplies. The present invention seeks to address a need to increase an amount of
available electrical energy to operate the low voltage circuit requirements of an
electricity meter without increasing the energy taken from the mains voltage. The
present invention provides a power supply of which both cycles of an input
alternating current are employed through the use of an inductor based circuit.

ENHANCING THE EFFICIENCY OF AC-DC LOW VOLTAGE POWER SUPPLIES BY TOPOLOGICAL MODIFICATIONS

Documents:

Inventors:

PCT Conventions: