GB2373933A

GB2373933A - Power regulating apparatus

Info

Publication number: GB2373933A
Application number: GB0107849A
Authority: GB
Inventors: Vincent William Lynch
Original assignee: LOANGUARD Ltd
Current assignee: LOANGUARD Ltd
Priority date: 2001-03-29
Filing date: 2001-03-29
Publication date: 2002-10-02
Also published as: GB0107849D0

Abstract

Power regulating apparatus for regulating supply of power from a power source 2 to a load 5. A processing means 4 determines a demand for power by the load, and a switch means 11 is operative to connect the source to the load. The processing means produces a signal to control the switch means and a filter means 10 is provided to filter out any d.c. component of the signal before it is received by the switch means. The apparatus is used particularly for supplying a charging current to a battery. The filter may be a capacitor. The switch means may be a transistor. The signal to control the switch may be a PWM square wave signal.

Description

Power regulating apparatus

The present invention relates to power regulating apparatus. The apparatus is particularly, although not exclusively, intended for use in charging a battery comprised in a power supply for fire safety apparatus.

Buildings are routinely fitted with actuator operated fire safety apparatus such as ventilators and fire curtains. In the event of fire ventilators are opened to vent smoke from a building and fire curtains closed to restrict movement of fire through a building. Because of the important safety function of such apparatus, where the apparatus requires mains electrical power to operate it is necessary to provide a back-up power supply so that the system can continue to operate in the event of mains electrical power failure. Back-up electrical power is usually provided by a battery.

In one known arrangement each of a number of actuators has its own associated power supply connected to a network. Each power supply comprises an electric battery which is arranged to be charged by electrical power supplied over the network. Each power supply also comprises a control means operative to control its associated actuator in response to signals received over the network.

When a number of batteries are to be charged over a network it is convenient for electrical current to be supplied over the network at a higher voltage than that to which the batteries are to be charged, to allow for loss

of voltage or'power off'over the network. Where this is the case it is necessary for the power supply to include a regulator to control the charging current supplied to the battery. It is also desirable to be able to alter the charging regime of the battery and to monitor the condition of the battery.

It has been proposed that controlling of charging current and battery conditions monitoring be implemented by a single microprocessor, conveniently a programmable microprocessor. There is, however, a drawback with this approach with certain circuit configurations in that failure of the microprocessor, for example due to a software problem or exposure to electromagnetic radiation, could lead to catastrophic failure of the circuit. This is because on failure of a microprocessor its outputs typically become d. c. which may result in the battery and other circuit components being exposed to the full voltage supplied over the network resulting in damage of the battery and circuit components, and possibly causing a fire.

The present invention has been made in consideration of this problem.

According to the present invention there is provided power regulating apparatus for regulating supply of power from a power source to a load comprising a processing means operative to determine a demand for power by the load and a switch means operative to connect the power source to the load to satisfy the demand for power wherein the processing means is

arranged to produce a signal for controlling the switch means and a filter means is provided to filter out any d. c. component of the signal before it is received by the switch means.

Provision of the filter means prevents any d. c. signal that may be produced by the processing means from being received by the switch means, reducing the risk of catastrophic failure of the circuit, for example in the event of failure of the processing means.

Preferably the processing means is a microprocessor, particularly a programmable microprocessor. The switch means is preferably an electrically operable switch means and preferably comprises a transistor. The signal produced by the processing means may be intermittent and/or varying. It is preferably a substantially square wave. A characteristic of the signal preferably varies in dependence upon the demand for power determined by the processing means. Where the signal produced by the processing means comprises a substantially square wave the mark-space ratio of the square wave is preferably varied in dependence upon the demand for power. The filter means preferably comprises a capacitor.

The power regulating apparatus is preferably comprised in apparatus for charging a battery in which case the load comprises a battery to be charged. The apparatus for charging a battery is preferably comprised in a power supply for safety apparatus, particularly fire safety apparatus.

In order that the invention may be more clearly understood

embodiments thereof will now be described by way of example with reference to the accompanying drawings the single figure of which shows a simplified schematic circuit diagram of apparatus according to the invention.

The apparatus, generally 1, is shown connected to a two wire network 2 and to an electric motor 3 which may be arranged to operate a ventilator, fire curtain or the like.

The network 2 comprises two separate wires and is employed to carry a data signal superimposed on a d. c. level in the range 35 to 42v to provide power for the apparatus 1 and motor 3. Providing power over data transmission wires'phantom powering', is of course known.

The apparatus comprises a first programmable microprocessor 4 operative to control charging of and to monitor the condition of a rechargeable battery 5, and a second programmable microprocessor 6 operative to send and receive data over the network and to control operation of the motor 3.

Power for the two microprocessors 4 and 6 is derived from the network 2 via a voltage regulator 7 operative to provide a stable d. c. voltage of around 5v.

Power for charging the battery 5 and or operation of the motor 3 is also derived from the network via a voltage regulator. In this case it is necessary to obtain a stable voltage of around 27v and the voltage regulator

is implemented by the first microprocessor 4.

The first microprocessor 4 is operative to monitor the battery 5 voltage via line 8 and to produce a square wave output at connection 9 the mark-space ratio of which is dependant upon the battery 5 voltage. The lower the voltage the greater proportion of marks. Connection 9 is connected via a capacitor 10 to the base of a transistor 11. The capacitor 10 is operative to decouple any d. c. component of the output from connection 9 of the microprocessor 4 from the transistor 11.

The collector of the transistor 11 is connected to a wire of the network 2 to draw a current therefrom. The emitter of the transistor 11 is connected via a smoothing circuit comprising an inductor 12 in series with the transistor 11, and a capacitor 13 in parallel with the transistor 11, to a terminal of the battery 5. The transistor 11 operates as a switch to connect the network 2 to the battery 5 to charge the battery 5 and/or to meet the power consumption requirements of the motor 3.

The voltage delivered to the battery 5 from the network 2 is regulated by virtue of intermittent operation of the transistor 11 in accordance with the square wave signal output by the microprocessor 4. The smoothing circuit 12,13 operates to smooth the output of the transistor 11 (which will be a square wave similar to that output by the microprocessor 4) so that a substantially d. c. level is supplied to the battery 5.

As the battery 5 voltage monitored by the microprocessor 4 rises

towards a predetermined level the mark-space ratio of the output from the microprocessor is adjusted to reduce the overall proportion of time that the transistor 11 allows current to flow from the network 2 to the battery 5, and vice versa. Since the network voltage is considerably higher than the desired battery 5 and motor 3 operating voltage at no time should the transistor 11 be allowed to remain permanently open. Were it to do so the resulting current flowing from the network 2 would damage the transistor 11 and possibly other components of the circuit. This is, of course, undesirable.

The transistor 11 is, however, protected from being in a permanently open state by the capacitor 10 which decouples the base of the transistor 11 from any permanent d. c. level. This considerably reduces the risk of catastrophic failure of the circuit.

For example, a software problem or the effect of electromagnetic radiation could cause the microprocessor 4 to fail such that the output at connection 4 becomes permanently high. In this situation without the provision of capacitor 10 the circuit would be susceptible to catastrophic failure. The presence of the capacitor 10 ensures that the circuit will fail safe.

The second microprocessor 6 is connected to the network 2 via capacitors 14 operative to decouple the d. c. level from the signal carried by the network so that just the data carrying component of the signal is seen

by the microprocessor 6. Via this connection the microprocessor may send and receive data over the network 2 relating to the condition of the battery 5 and operation and status of the motor 3. The microprocessor 6 is operative to control the motor 3 in accordance with programmed instructions and/or instructions received over the network 2 via a switching circuit 15 which enables the motor 3 to run in both forward and reverse directions.

Power for operation of the motor 3 may be derived form either the battery 5 and/or the network 2. In the event of failure of the supply of power over the network 2 the apparatus may operate from power derived from the battery above.

The apparatus is particularly suited for the operation of fire safety equipment but could be used in any other appropriate applications.

Although the described embodiment is arranged for connection to a two wire network 2 which utilizes phantom powering it could be arranged for connection to other types of networks in particular to a four wire network comprising two wires providing a d. c. power supply and two separate wires carrying data, or a six wire network similar to the four wire network but comprising a further two wires operative to supply power directly to the motor in response to operation of a fireman's switch.

The above embodiments are described by way of example only.

Many variations are possible without departing from the invention.

Claims

1. Power regulating apparatus for regulating supply of power from a power source to a load comprising a processing means operative to determine a demand for power by the load and a switch means operative to connect the power source to the load to satisfy the demand for power wherein the processing means is arranged to produce a signal for controlling the switch means and a filter means is provided to filter out any d. c. component of the signal before it is received by the switch means.

2. Apparatus as claimed in claim 1 wherein the processing means is a programmable microprocessor.

3. Apparatus as claimed in either claim 1 or claim 2 wherein the switch means comprises a transistor.

4. Apparatus as claimed in any preceding claim wherein the signal produced by the processing means comprises a substantially square wave.

5. Apparatus as claimed in any preceding claim wherein a characteristic of the signal produced by the processing means charges in dependence upon the demand for power.

6. Apparatus as claimed in claim 5 when dependent upon claim 4 wherein the mark-space ratio of the signal is varied in dependence upon the demand for power.

7. Apparatus as claimed in any preceding claim wherein the filter means comprises a capacitor.

8. Apparatus for charging a battery comprising power regulating apparatus as claimed in any preceding claim.

9. A power supply for safety apparatus comprising a battery and apparatus for charging the battery as claimed in claim 8.

10. A power supply for safety apparatus substantially as herein described with reference to the accompanying drawing.