Patent Description:
Fire alarm systems typically include fire control panels that operate as system controllers. Fire detection/initiation devices and alarm notification devices are then installed, distributed throughout the buildings and connected to the panels. The distributed devices are typically connected to one or more loops. Some examples of fire detection/initiation devices include smoke detectors, carbon monoxide detectors, flame detectors, temperature sensors, and/or pull stations (also known as manual call points). Some examples of fire notification devices include speakers, horns, bells, chimes, light emitting diode (LED) reader boards, and/or flashing lights (e.g., strobes).

The fire detection devices monitor the buildings for indicators of fire. Upon detection of an indicator of fire such as smoke or heat or flames, the distributed device is activated and a signal is sent from the activated distributed device to the fire control panel. The fire control panel then initiates an alarm condition by activating audio and visible alarms of the fire notification devices of the fire alarm system, which are also distributed around the building. Additionally, the fire control panel will also send an alarm signal to a monitoring station, which will notify the local fire department or fire brigade.

Intrusion systems typically include intrusion panels and their own distributed devices. The distributed monitoring devices detect indications of intrusions, building security breaches and unauthorized access at or within the building and report to the intrusion panels. Examples of monitoring devices include motion sensor devices, door and window relays, thermal sensors, and surveillance camera devices that communicate with the intrusion panel over a security network. Motion sensor devices can detect intrusions and unauthorized access to the premises, and send indications of the intrusions to the security panel. The surveillance camera devices capture video data of monitored areas within the premises, in examples.

Building automation systems will typically include one or more building automation control panels and distributed devices that control and monitor the physical plant aspects of a building and aspects of business-specific electrical, computer, and mechanical systems. The physical plant typically includes heating, ventilation, and air conditioning (HVAC) systems, elevators/escalators, lighting and power systems, refrigeration and coolant systems, and air and/or water purification systems, in examples. HVAC systems typically include air handlers and systems of ducts and vents for circulating air throughout the building. Business-specific systems include computer systems, manufacturing systems that include various types of computer-aided machinery and test equipment, and inventory control and tracking systems, in examples.

The control panels of the building management systems are powered by power supplies. These supplies typically convert an alternating current (AC) power input from an AC mains/line voltage into a direct current (DC) output. The DC output provides power to the control panels. The power supplies can also provide power to the loops and the distributed devices that communicate with the control panels. Types of power supplies include linear power supplies that operate at an AC main line frequency (i.e. <NUM>/<NUM>), and switching power supplies such as "DC to DC power supplies" that operate at a much higher operating frequency (typically <NUM>-<NUM>), in examples.

Power supplies for control panels are designed for high reliability. Many control panels have backup/secondary power supplies that provide power when a primary power supply fails. The life span of power supplies is typically measured in Mean Time Between Failures (MTBF). Power supplies are often designed with a MTBF of <NUM>,<NUM> hours under full load, or possibly more. Factors that influence the MTBF of a power supply (and therefore its expected life span) include whether the power supply is under a full or partial load during its operation, and whether adequate cooling is provided during its operation, in examples.

Recently, it has been proposed to use connected services systems to monitor building management systems. Connected services systems are remote systems that communicate with the building management systems and are sometimes administered by separate business entities than the owners and/or occupants of the buildings, which contain the building managements systems. For example, the connected services system can be administered by a building management system manufacturer and/or an entity providing service on the building management systems.

<CIT> discloses a power converter including a processor and at least one component whose health in the power converter will degrade over time. The processor is configured for monitoring the health of the component over time, and for generating a warning signal when the monitored health of the component reaches a threshold level.

<CIT> discloses a ripple monitoring circuit which generates information about a power supply. At least one input may receive a ripple signal from the power supply that has a ripple component. A ripple measurement circuit may measure a characteristic of the ripple component. A storage circuit may store information about the measurement. A comparison circuit may compare information stored in the storage circuit with a threshold value and indicate when the stored information meets or exceeds this threshold value.

The present invention is directed towards building management systems that can monitor the health of their power supplies. Specifically, the proposed systems monitor the health of power supplies that provide power to control panels of the building management systems. For this purpose, a voltage across one or more capacitors of each power supply might be measured.

The control panels also forward information concerning the health of the power supplies to a connected services system. The connected services system then analyzes the information across multiple power supplies to determine trends, and executes statistical analysis upon the information. A technician can then use the analysis to determine trends across power supplies of multiple building management systems and to predict when power supplies may fail, in examples.

In general, according to one aspect, the invention features a power supply monitoring system as set out in claim <NUM>.

Preferably, the bandpass filter has a center frequency at an operating frequency of the power supply system. The bandpass filter includes a first capacitor that blocks a DC bias of the capacitor voltage and passes an AC ripple voltage component of the capacitor voltage. The bandpass filter can additionally amplify the filtered ripple signal.

Additionally and/or alternatively, the bandpass filter includes a voltage divider and an amplifier. The voltage divider biases an AC ripple voltage component of the capacitor voltage to be at a center of an operating range of the amplifier.

The rectifier and transient filter typically includes two or more diodes. The rectifier and transient filter can additionally include a low pass filter that filters the rectified ripple signal to attenuate transients and/or surges within the rectified ripple signal.

In general, according to another aspect, the invention features a building management system as set out in claim <NUM>.

The system can also include a connected services system that communicates with the system panel over a network. The system panel forwards information concerning health of the power supply system, reported by the power supply health monitoring system, to the connected services system. The connected services system can also combine the information concerning health of the power supply system, with information concerning health of other power supply systems from system panels of other building management systems, and determine trends among the combined information concerning health of the power supply systems.

The information concerning health of the power supply system includes a sampled rectified ripple signal representing a level of ripple associated with the power supply system. Typically, the level of ripple associated with the power supply system is an AC ripple voltage component of a voltage across a capacitor of the power supply system.

Additionally and/or alternatively, the power supply health monitoring system can determine that the power supply system is operating outside an acceptable operational state, when a sampled rectified ripple signal representing a level of ripple associated with the power supply system is lower than a minimum threshold value and/or higher than a maximum threshold value.

In one example, the building management system is a fire alarm system, and the system panel is a fire alarm system control panel.

Additionally and/or alternatively, the system panel reports the information concerning health of the power supply system to a mobile computing device carried by a technician.

In general, according to yet another aspect, the invention features a power supply monitoring method as set out in claim <NUM>.

In general, according to still another aspect, the invention features a method for monitoring a building management system as set out in claim <NUM>.

The above and other features of the invention including various novel details of construction and combinations of parts, and other advantages, will now be more particularly described with reference to the accompanying drawings and pointed out in the claims The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention.

It will be understood that although terms such as "first" and "second" are used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. Thus, an element discussed below could be termed a second element, and similarly, a second element may be termed a first element without departing from the teachings of the present invention.

<FIG> shows two exemplary building management systems installed at a building <NUM>. The building management systems include a fire alarm system and an intrusion system that communicate with a connected services system <NUM> via a public network <NUM>.

In general, the building management systems include control panels <NUM> and distributed devices <NUM>. Each control panel <NUM> is powered by one or more power supplies <NUM> that are preferably dedicated to each control panel <NUM>. Each power supply <NUM> converts an AC input voltage such as an AC mains power input (e.g. 120VAC at <NUM>/<NUM>) into a DC output that is tailored to the power requirements of each control panel <NUM>.

Power supplies in general have limitations. Robust power supply design is difficult. In addition, even the best designed power supplies will degrade in performance over time and eventually fail. As a result, it is common to design power supplies with a rated maximum lifetime/MTBF based on statistical analysis and redundancies.

Power supplies used in building management systems have additional considerations. Fire alarm systems for example, are high availability/reliability systems. The fire alarm system as a whole and its individual components must be monitored for any indications of foreseeable failure and/or degradation in operation. While power supplies are highly reliable components, experience has shown that building managers often use power supplies well past their typical consumer product lifetime/MTBF or beyond when replacement parts are available.

As a result, according to the present invention, these power supplies are monitored for any indications of foreseeable failure and/or degradation in operation.

In the illustrated example, each of the control panels <NUM> receive information concerning health of its power supplies, determined by and sent from its respective power supply <NUM>. In the preferred embodiment, the control panels <NUM> monitor the received information to assess whether the power supply is at risk of imminent failure.

The connected services system <NUM> communicates with building management systems installed within buildings <NUM>. The control panels <NUM> also forward the information concerning health of the power supplies over public network <NUM> to the connected services system <NUM>. This system <NUM> can assess failure across many different panel power supplies based on the information reported from the panels <NUM>. In this way, the connected services system <NUM> can also determine whether or not an individual power supply <NUM> is trending toward a failure, and/or if multiple power supplies are trending toward a failure.

In general, the panels are connected to distributed devices <NUM> via safety and security wired and/or wireless networks <NUM> of the building <NUM>. These networks <NUM> support data and/or analog communication between the distributed devices <NUM> and the respective control panels <NUM>. In some embodiments (not illustrated), the distributed devices <NUM> could all be connected to the same safety and security network <NUM>.

In the illustrated example, distributed devices <NUM> of the fire alarm system are connected to a safety and security network <NUM>-<NUM>. The network <NUM>-<NUM>, in turn, connects to a loop interface <NUM> of a fire alarm system control panel <NUM>-<NUM>. The distributed devices are slave devices of the panel <NUM>-<NUM>. The fire alarm system control panel <NUM>-<NUM> also has a monitoring port <NUM>, a network interface <NUM>, and receives a DC input power signal from power supply <NUM>-<NUM>.

The distributed fire alarm devices <NUM> include alarm initiation devices including smoke detectors <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, heat detectors <NUM>-<NUM> and manually activated devices such as pull stations <NUM>-<NUM>. The alarm initiation devices monitor the buildings for indicators of fire. Upon detection of indicators of fire, device signals are sent from the alarm initiating devices to the control panel <NUM>-<NUM>. The device signals are typically alarm signals and/or analog values. The alarm signals are used to signal the control panel <NUM>-<NUM> that a fire has been detected.

Similar to the fire alarm system, distributed devices <NUM> of the intrusion system are connected to a second network <NUM>-<NUM>. The second network then connects to a loop interface <NUM> of an intrusion system control panel <NUM>-<NUM>. The intrusion panel <NUM>-<NUM> also has a monitoring port <NUM>, a network interface <NUM>, and receives a DC input from power supply <NUM>-<NUM>.

The distributed intrusion devices <NUM> include devices for detecting the presence of unauthorized individuals in the building <NUM>, including motion detectors <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> and other devices (not illustrated) such as security cameras, door and window relays and network video recorders, among other examples. Upon detection of the presence of unauthorized individuals, device signals are sent from the motion detectors <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM>, <NUM>-<NUM> to the intrusion control panel <NUM>-<NUM>.

The present system can be extended to other types of building management systems. For example, in another implementation the panel is a building automation panel such as a panel that might control building climate including HVAC.

A technician <NUM> is carrying a mobile computing device <NUM>. Mobile computing devices <NUM> include smart phones, tablets, and other portable devices, such as devices running the Android or IOS operating systems.

The fire alarm system control panel <NUM>-<NUM> and intrusion system control panel <NUM>-<NUM> are connected to the connected services system <NUM> via a leased data connection, private network and/or public network <NUM>, such as the internet. The mobile computing device <NUM> also connects to the public network <NUM> via a wireless communication link <NUM> to a cellular radio tower <NUM>. The tower <NUM> provides access to a mobile broadband or cellular network or public and/or private wired data networks such as an enterprise network, Wi-Max, or Wi-Fi network, for example.

The control panels <NUM> also report information concerning health of its power supplies <NUM> to the mobile computing devices <NUM> of the technicians <NUM>. In one example, if the information indicates that a power supply <NUM> is at risk of imminent failure, the control panels <NUM> reports this information to the mobile computing devices <NUM>. The control panels <NUM> report this information to the mobile computing devices <NUM> over a communications path that includes the public network, tower <NUM>, and wireless communications link <NUM>, in one example.

The connected services system <NUM> is typically implemented as a cloud system. It can be run on a proprietary cloud system or implemented on one of the popular cloud systems operated by vendors such as Alphabet Inc. , Amazon, Inc. (AWS), or Microsoft Corporation. As a result, the connected services system <NUM> typically operates on a connected services server system <NUM>. In some cases, this server system <NUM> is one or more dedicated servers. In other examples, they are virtual servers.

The connected services server system <NUM> executes modules, including a connected services trend analysis module (trend analysis module) <NUM> and a connected services database <NUM>. Each of these modules is associated with separate tasks. In some cases, these modules are discrete modules or they are combined with other modules into a unified code base. They can be running on the same server or different servers, virtualized server system, or a distributed computing system.

The connected services database <NUM> stores information provided by the control panels <NUM>. The trend analysis module <NUM> accesses and analyzes the information stored to the database <NUM>.

<FIG> shows a power supply <NUM> that provides power to an exemplary control panel <NUM>. The power supply <NUM> includes a power supply ripple detector (ripple detector) <NUM> and a switching system <NUM>. The control panel <NUM> additionally includes a panel controller <NUM> that controls the network interface <NUM>, the monitoring port <NUM>, and the loop interface <NUM>.

There are multiple causes for power supply failure. Power supplies <NUM> most often fail due to improper operating conditions or misapplication of the power supplies <NUM>. The improper operating conditions include overloading and inadequate cooling, in examples. When the power supplies are otherwise applied in a proper fashion, the most common cause of failure is the deterioration of capacitors within the power supply <NUM> at or near the expected lifetime/MTBF of the power supplies.

Capacitors within power supplies <NUM> are relied upon for their ability to alternately store and then provide electricity in quick bursts. Capacitors provide a continuous output voltage in response to a varying (i.e. alternating) input voltage. Capacitors store charge during a positive swing of the voltage input, and discharge during a negative swing of the voltage input. Capacitors continuously alternate between charging and discharging in response to the power grid's AC input voltage, which alternates at a frequency of <NUM>/<NUM>, or in response to the much faster operating frequencies of a switching power supply.

Ripple (also known as ripple voltage) is an AC voltage component of the direct current output/DC bias of a power supply <NUM>. The ripple voltage is typically created by one or more capacitors of the power supply that are connected across the DC output. When capacitors reach the end of their life, they provide less capacity for electricity during charging and also impede the flow of electricity during discharge. Both limitations cause the voltage across the capacitor to oscillate, or ripple, if viewed on an oscilloscope.

Ripple voltage created by capacitors in power supplies <NUM> can have several effects upon the power supplies. At its lowest value, the ripple voltage can cause circuits of the power supply to 'brown out. ' This is because a low ripple voltage value is an indicator that the power supply <NUM> can no longer produce sufficient output voltage. At its highest value, the ripple voltage can cause excessive stress to components of the power supply. Excessive ripple, especially in high frequency switching supplies, can interfere with the operation of both the load on the power supply and surrounding electronics through radiated emissions. Finally, the biggest issue with excessive ripple is that it will cause higher heat in the capacitors of the power supply. Heating of the capacitors causes the capacitors to fail faster, which in turn shortens the expected lifetime of the power supply.

Returning to <FIG>, in more detail, the switching system <NUM> includes a capacitor C0 located at the output of the switching system <NUM>. Capacitor C0 connects to a positive DC output rail, labeled as DC out +, and to a negative DC output rail, labeled as DC out -. The voltage across the capacitor is labeled as Vc(t). The DC out + and DC out - rails connect to the ripple detector <NUM> as indicated by references <NUM> and <NUM>, respectively. The DC out + rail also connects to a positive DC rail of the control panel <NUM>, labeled as DC in +, and the DC out - rail also connects to a negative DC rail of the control panel <NUM>, labeled as DC in -.

The power supply ripple detector <NUM> also provides a sampled rectified ripple signal <NUM> and a health signal <NUM> as output. The monitoring port <NUM> receives the signals <NUM>/<NUM>, and the panel controller <NUM> forwards the signals <NUM>/<NUM> via network interface <NUM> to the public network <NUM>. More information concerning creation and use of the sampled rectified ripple signal <NUM> and the health signal <NUM> is provided in the description of the power supply ripple detector <NUM> that accompanies <FIG>, included herein below.

Within each building management system, the control panel <NUM> operates as a system panel for controlling the building management system. The switching system <NUM> of the power supply <NUM> forms a power supply system, and the power supply system powers the system panel. The power supply ripple detector <NUM> of the power supply, in turn, monitors the health of the power supply system. As a result, the ripple detector <NUM> also operates as a power supply health monitoring system. The power supply health monitoring system obtains information concerning health of the power supply system. The power supply health monitoring system then reports the information concerning health of the power supply system to the system panel/control panel <NUM>.

The system panel/control panel <NUM>, in turn, forwards the information concerning health of the power supply system to the connected services system <NUM>. The connected services system <NUM> combines the information concerning health of the power supply system, with information concerning health of other power supply systems from system panels of other building management systems. The connected services system <NUM> stores the combined information concerning health of the power supply systems to the database <NUM>, and the trend analysis module <NUM> determines trends among the combined information concerning health of the power supply systems.

<FIG> shows more detail for the ripple detector <NUM>. The ripple detector <NUM> has three sequential "stages" of operation: a bandpass filter <NUM>, a rectifier and transient filter <NUM>, and processing executed by a microprocessor <NUM>. The microprocessor <NUM> includes an Analog to Digital (A/D) port <NUM>, a long term trend reporter module <NUM>, a fault threshold detection module <NUM>, and an output port <NUM>.

In more detail, the ripple detector <NUM> receives the capacitor voltage Vc(t) across capacitor C0 as input. The capacitor voltage Vc(t) then enters the first stage (bandpass filter <NUM>). The bandpass filter <NUM> produces a filtered ripple signal <NUM> from the capacitor voltage Vc(t). The bandpass filter <NUM> has a center frequency at an operating frequency of the power supply <NUM>.

The second stage (rectifier and transient filter <NUM>) transforms the oscillating waveform of the filtered ripple signal <NUM> into a slow, measurable output. Specifically, the rectifier and transient filter <NUM> converts the filtered ripple signal <NUM> into a rectified ripple signal <NUM>. The rectified ripple signal <NUM> is an analog DC signal that represents a level of ripple of the capacitor voltage Vc(t), and therefore represents a level of ripple of the power supply <NUM> itself. The rectified ripple signal <NUM> slowly changes with time/age of the power supply <NUM>.

The third stage (processing executed by microprocessor <NUM>) analyzes the rectified ripple signal <NUM> and produces information concerning health of the power supply <NUM>. The information concerning health of the power supply <NUM> is based upon the rectified ripple signal <NUM>.

The A/D port <NUM> of the microprocessor <NUM> receives and then converts the rectified ripple signal <NUM> into a sampled rectified ripple signal <NUM>. The sampled rectified ripple signal <NUM> is then passed to the long term trend reporter <NUM> and fault threshold detection <NUM> modules. In one implementation, the microprocessor <NUM> is an Application Specific Integrated Circuit (ASIC).

The long term trend reporter <NUM> sends the sampled rectified ripple signal <NUM> to the output port <NUM>. Because the rectified ripple signal <NUM> slowly changes with time/age of the power supply <NUM>, the sampled rectified ripple signal <NUM> also changes over time According to the invention, the long term trend reporter <NUM> provides the sampled rectified ripple signal <NUM> to the output port <NUM> on a periodic basis, and/or when the sampled rectified ripple signal <NUM> has changed in value.

The fault threshold detection module <NUM> compares the sampled rectified ripple signal <NUM> to one or more acceptable/allowed threshold values for ripple voltage, and produces a health signal <NUM> in response to the comparison. The health signal <NUM> indicates whether the level of ripple of the capacitor voltage Vc(t) (and therefore whether the level of ripple of the power supply <NUM> itself) meets the one or more acceptable/allowed threshold values.

In one implementation, the fault threshold detection module <NUM> of the microprocessor <NUM> maintains both a minimum and a maximum allowed/acceptable threshold value for the sampled rectified ripple signal <NUM>. When the fault threshold detection module <NUM> determines that the sampled rectified ripple signal <NUM> is within range of the minimum and maximum acceptable values, the fault threshold detection module <NUM> sets the health signal <NUM> value to be TRUE (e.g. equal to <NUM>). This indicates that the power supply <NUM> is healthy/operating normally. When the sampled rectified ripple signal <NUM> is either below the minimum acceptable value or is above the maximum value, however, the fault threshold detection module <NUM> sets the health signal <NUM> value to be FALSE (e.g. equal to <NUM>). This indicates that the power supply <NUM> is operating outside an acceptable operational state, such as when capacitors of the power supply are beginning to fail. The fault threshold detection module <NUM> then sends the health signal <NUM> to the output port <NUM>.

As a result, the microprocessor <NUM> operates as a controller that analyzes the capacitor voltage Vc(t), via the bandpass filter <NUM>, to assess a health of the power supply <NUM>.

The microprocessor <NUM> then transmits information concerning the health of the power supply <NUM> to the control panel <NUM>. The information concerning the health of the power supply <NUM> includes both the health signal <NUM> and the sampled rectified ripple signal <NUM>. The microprocessor <NUM> transmits this information from its output port <NUM> to the monitoring port <NUM> of the control panel <NUM>.

The control panel <NUM> monitors the received information concerning the health of its power supply <NUM> to assess the health of its power supply <NUM>. In one example, upon receiving a health signal <NUM> of the information with a value of FALSE, the control panel <NUM> sends a message to this effect to one or more mobile computing devices <NUM>. Technicians <NUM> carrying the mobile computing devices <NUM> can then execute actions in response, such as replacing the power supply <NUM>.

The control panel <NUM> then forwards the information concerning the health of the power supply <NUM> (i.e. the health signal <NUM> and the sampled rectified ripple signal <NUM>) to the connected services system <NUM> for further reporting and analysis. The connected services system <NUM> receives and stores the information to database <NUM>. The trend analysis module <NUM> then tracks the information concerning the health of each power supply <NUM> over time, and also reports the analysis to mobile computing devices <NUM> carried by technicians <NUM>, in examples.

The connected services system <NUM> also receives, stores, and analyzes information concerning the health of other power supplies <NUM> forwarded by other control panels <NUM>.

<FIG> shows detail for an embodiment of the bandpass filter <NUM>. The bandpass filter <NUM> includes an input capacitor C1, a voltage divider <NUM>, a low pass filter <NUM>-<NUM>, and an amplifier <NUM>. In another embodiment, the bandpass filter <NUM> does not include the amplifier <NUM>. VCC is a filtered version of the DC output of the power supply <NUM> so that it does not impact the performance of the bandpass filter <NUM>. Voltage divider <NUM> includes resistors R1 and R2. Lowpass filter <NUM>-<NUM> includes resistor R3 and capacitor C2.

The amplifier <NUM> may be included to increase the amplitude of the filtered ripple signal <NUM>. This is because the amplitude of the ripple voltage <NUM> (even when it can be a problem) is usually much smaller than the amplitude of the DC bias signal. Amplifier <NUM> includes an op amp <NUM> configured as an inverting amplifier, input resistor R4, and feedback resistor R5.

The bandpass filter <NUM> is tuned to the operating frequency of the power supply <NUM>. The bandpass filter <NUM> passes signals in a narrow band of frequencies that include the target operating frequency (or range of frequencies) of the power supply <NUM>. The bandpass filter <NUM> also attenuates signals having frequencies that are above or below the target operating frequencies of the power supply <NUM>. Because control loops for power converters are usually designed to respond much slower than the operating frequency of the power supplies, it is unlikely that a load will create a sustained ripple and cause a false-positive.

Capacitor C1 blocks a DC bias of the capacitor voltage Vc(t). C1 also passes an AC ripple voltage component of the capacitor voltage Vc(t), also known as the ripple voltage <NUM>. Voltage divider <NUM> biases the ripple voltage <NUM> from VCC to Common to be at the center of an operating range of the amplifier <NUM>. The biasing is required because bandpass filters are typically AC signals centered around 0V and require bipolar supplies (both positive and negative). The biasing centers the ripple voltage <NUM> between the DC out +/DC out - power supply rails.

Lowpass filter <NUM>-<NUM> attenuates transient signals within the ripple voltage <NUM>. Without this filtering, the transient signals could otherwise cause the rectifier and transient filter <NUM> to produce rectified ripple signals <NUM> having an erroneously large amplitude. Finally, the amplifier <NUM> amplifies the difference between a small AC signal on capacitor C2 of lowpass filter <NUM>-<NUM> and a voltage mid-way between VCC and Common, and the bandpass filter <NUM> produces a filtered ripple signal <NUM> as output.

The ability of the bandpass filter <NUM> to pass ripple voltages at the operating frequency of power supply <NUM> while rejecting ripple voltages of other frequencies has an advantage. The bandpass filter <NUM> is sensitive to high frequency power supply ripple while rejecting all external influences on the measurement of the ripple. As a result, the bandpass filter <NUM> is tailored to measure only the contribution of the power supply's capacitors to the ripple, while suppressing all other external sources of influence.

<FIG> illustrates operation of the bandpass filter <NUM> for different capacitor voltages Vc(t). Capacitor voltages Vc(t)_A, Vc(t)_B, and Vc(t)_C are oscillating at frequencies that are below, at, and above a target frequency of the bandpass filter <NUM>, respectively. The target frequency of the filter refers to the expected range of frequencies of the capacitor voltage Vc(t) that the bandpass filter <NUM> was designed to pass.

For capacitor voltages Vc(t)_A and Vc(t)_C, the filtered ripple signals <NUM> produced by the bandpass filter <NUM> are attenuated. These filtered ripple signals <NUM> are attenuated because the oscillating frequencies of the capacitor voltages Vc(t)_A and Vc(t)_C are respectively below and above the target frequency range of the bandpass filter <NUM>. Because capacitor voltage Vc(t)_B has an oscillating frequency that is within the target frequency range of the bandpass filter <NUM>, however, the bandpass filter <NUM> passes the filtered ripple signal <NUM> to the rectifier and transient filter <NUM> for additional processing. Here, the filtered ripple signal <NUM> passed by the bandpass filter <NUM> is also amplified (i.e.. increased in amplitude) by amplifier <NUM>, according to the embodiment of the bandpass filter <NUM> shown in <FIG>.

<FIG> shows more detail for the rectifier and transient filter <NUM>. The rectifier and transient filter <NUM> includes capacitor C3, diodes D1 and D2, lowpass filter <NUM>-<NUM>, and output resistor R7. Lowpass filter <NUM>-<NUM> includes resistor R6 and capacitor C4.

Capacitor C3 removes any DC bias from the input filtered ripple signal <NUM>. Diodes D1 and D2 sample the peaks of each cycle of the filtered ripple signal <NUM> and rectify the filtered ripple signal <NUM> into a rectified ripple signal <NUM>. Though diodes D1 and D2 are shown, it can be appreciated that additional diodes can be included to rectify the filtered ripple signal <NUM> into the rectified ripple signal <NUM>. Lowpass filter <NUM>-<NUM> filters (e.g. attenuates) transients and/or surges in the rectified ripple signal <NUM>. Capacitor C4 of lowpass filter <NUM>-<NUM> also stores a charge between peaks of the rectified ripple signal <NUM>. Finally, the output resistor R7 slowly discharges the rectified ripple signal <NUM> provided by the lowpass filter <NUM>-<NUM> so that the lowpass filter <NUM>-<NUM> does not accumulate/capture false positives such as transient events or external surges over time. The rectifier and transient filter <NUM> then provides the rectified ripple signal <NUM> as output to the microprocessor <NUM>.

<FIG> illustrates operation of the rectifier and transient filter <NUM>. The rectifier and transient filter <NUM> converts an oscillating filtered ripple signal <NUM> as input into a rectified ripple signal <NUM> as output.

Claim 1:
A power supply monitoring system connectable to a power supply system for a system panel for controlling a building management system, the power supply monitoring system comprising:
a bandpass filter (<NUM>) for filtering a voltage across a capacitor of the power supply system (<NUM>), wherein the bandpass filter (<NUM>) produces a filtered ripple signal from the capacitor voltage;
a rectifier and transient filter (<NUM>) that receives the filtered ripple signal and outputs a rectified ripple signal, which is an analog DC signal representing a level of ripple of the voltage across the capacitor; and
a controller configured to perform a comparison of the rectified ripple signal to one or more acceptable threshold values for the rectified ripple voltage and report a health of the power supply system to the system panel responsive to the comparison,
wherein a microprocessor is configured to operate as the controller, wherein the microprocessor;
receives the rectified ripple signal via an Analog to Digital, ADC, port (<NUM>) of the microprocessor,
converts, via the ADC port, the rectified ripple signal into a sampled rectified ripple signal, and
sends, via a long term trend reporter module (<NUM>) included in the microprocessor, the sampled rectified ripple signal to the system panel (<NUM>) on a periodic basis and/or when the sampled rectified ripple signal has changed in value,
compares, via a fault threshold detection module included in the microprocessor, the sampled rectified ripple signal to one or more acceptable/allowed threshold values for ripple voltage, and produces a health signal (<NUM>) in response to the comparison indicating whether the level of ripple of the capacitor voltage meets one or more acceptable/allowed threshold values,
and sends the health signal (<NUM>) to the system panel (<NUM>).