Current Disturbance Detection System

Abstract

The present invention provides a drive circuit and drive arrangement for driving a load between two output terminals. The drive circuit has an input and an output terminal connected to the input. A fault detection inductor is connected in series with the output terminals and configured to modify an electrical parameter through a feedback inductor in response to a change in current between the output terminals. The feedback inductor is galvanically isolated from the fault detection inductor but magnetically coupled to the fault detection inductor. The drive circuit further comprises a first current detection inductor through which a current provided by the converter passes, the feedback inductor also being galvanically isolated from the first current detection inductor but magnetically coupled to the first current detection inductor. Thus, the feedback inductor can be induced with signals from both the current detection inductor and the fault detection inductor, saving components, space and cost.

Description

[Technical Field]

[0001] The present invention relates to the field of drivers, and more particularly to techniques for monitoring the current delivered by a driver to a load. [Background technology]

[0002] In the consumer and industrial appliance sector, there are a wide variety of drive configurations available for driving loads.

[0003] It is common for these drive configurations to have a converter that converts power (e.g. from a battery or mains power supply) and supplies the converted power to a load via output terminals. If the load requires DC current, an output capacitor is usually provided across the output terminals to store and smooth the power supplied by the converter.

[0004] Proper control of the power delivered to a load via the output terminals requires feedback. This is typically accomplished by monitoring the current delivered to the load at the output terminals, optionally with an output capacitor, to ensure that the current matches the desired current to be delivered to the load. A conventional way to measure the current to a load is to have a current-sense resistor in series with the load. A disadvantage of such a solution is that the current-sense resistor always consumes power, resulting in power loss. Summary of the Invention [Problem to be solved by the invention]

[0005] There is a continuing desire to improve the monitoring of current delivered to a load.

[0006] US20040012381A1 discloses an abnormality detection circuit that includes a current detection unit based on magnetic flux. [Means for solving the problem]

[0007] The basic idea of ​​the present invention is to use an inductor, instead of a current-sensing resistor, to sense the current through a load. More specifically, such an inductor is not used to measure the normal operating current to the load, but is sized and / or positioned to respond to relatively more abrupt and / or large changes in the current to the load caused by faults related to the load and / or the load / output terminals. A wide variety of potential faults, such as open circuits, short circuits, and loose connections, can cause very abrupt / large changes in the current through the load and / or between the output terminals, which causes large voltage changes across the inductor. By analyzing this voltage across the inductor, the occurrence of a fault can be determined. The inductor is coupled to a feedback inductor. A further idea of ​​the present invention is that a current-sensing inductor used to sense the normal operating current supplied to the load by, for example, a rectifier, is also coupled to the feedback inductor, so that the feedback inductor can be induced with signals from both the current-sensing inductor and the fault-detecting inductor. This integration of three windings / inductors saves components, space, and cost. Notably, using the same feedback inductor to provide information from both the fault detection inductor and the current detection inductor eliminates the need for multiple feedback inductors.

[0008] The invention is defined by the claims.

[0009] According to an example in accordance with an aspect of the present invention, a drive circuit is provided for supplying power generated by a converter to a load.

[0010] The drive circuit includes an input adapted to receive power from the converter, output terminals adapted to be connected to a load to supply the received power to the load, a fault detection inductor electrically connected in series with the output terminals such that current flowing through the output terminals and the load passes through the fault detection inductor such that a fault across the output terminals causes a change in the current flowing through the fault detection inductor, a first current detection inductor through which current supplied by the converter passes, and a feedback inductor galvanically isolated from the fault detection inductor and magnetically coupled to the fault detection inductor, the feedback inductor adapted to change the current flowing through the fault detection inductor a feedback inductor configured to modify an electrical parameter passing through the feedback inductor, the feedback inductor being galvanically isolated from the first current sensing inductor and magnetically coupled to the first current sensing inductor, the feedback inductor configured to modify the electrical signal in response to a current passing through the first current sensing inductor via the electrical signal; a detector configured to detect a change in the electrical parameter passing through the feedback inductor and generate a fault feedback signal in response to the detected changed electrical parameter; and a current detection circuit configured to sense the current passing through the first current sensing inductor via the electrical signal.

[0011] The proposed approach provides a fast-response solution to sudden changes in current at the load or output terminals, such as those caused by a sudden short circuit, open circuit, or other form of damage or fault. The use of a feedback inductor connected between the output capacitor and the load facilitates detection of sudden / large changes in current through the load, thereby facilitating identification of such faults. The galvanically isolated feedback inductor provides galvanic isolation between the power loop and the control loop. This provides a reliable, fast-response system for identifying fault occurrences. Additionally, a current-sensing inductor is used, for example, to sense the normal operating current supplied to the load. The feedback inductor is also coupled to the current-sensing inductor, so that it can be induced with signals from both the current-sensing inductor and the fault-sensing inductor. This integration of three windings saves components, space, and cost. Notably, using the same feedback inductor to provide information from both the fault-sensing inductor and the current-sensing inductor eliminates the need for multiple feedback inductors.

[0012] A change in the current through the fault detection inductor may indicate a fault between the output terminals and the load, and / or a fault in the load itself.

[0013] The drive circuit may further include an output capacitor connected in parallel with the output terminal and adapted to smooth the received power from the converter, and the fault detection inductor is electrically connected between the output capacitor and the output terminal.

[0014] In this embodiment, the inductor is placed after the output capacitor so that the inductor is more sensitive to fault currents at the load / load terminals, which are not filtered out by the output capacitor. Fault currents are currents (e.g., changes) induced by faults across the output terminals and / or in the load.

[0015] In some examples, the drive circuit further includes a rectifier arrangement configured to rectify power supplied by the converter and supply the rectified power to the output terminals, the rectifier arrangement having a first rectification path, the first current detection inductor being disposed in the first rectification path, and the current detection circuit, which senses the current flowing through the first current detection inductor via the electrical signal, includes a filter configured to generate a filtered signal that is a filtered version of the current flowing through the feedback inductor relative to the current flowing through the first current detection inductor, where the component induced by the fault detection inductor has been filtered or attenuated, and a current detection detector for generating a current feedback signal in response to the filtered signal.

[0016] A filter is used to effectively separate signals related to the current feedback signal from signals related to the fault feedback signal. The filter may include an averaging circuit and / or a frequency selection circuit. The averaging circuit averages any electrical signal fed to the filter (e.g., averaging the voltage using a capacitor), so that large but short fault signals are filtered out and the remaining signal is precisely the rectifier output current. The frequency selection circuit selects specific frequencies and / or frequency ranges and attenuates other frequencies, so that transient fault signals are filtered out and the remaining signal is precisely the rectifier output current.

[0017] The rectifier may be a half-wave rectifier in which case it has only the first rectification path, or in further embodiments, it may be a full-wave rectifier in which it also has a second rectification path. In such embodiments, the drive circuit may further include a second current sensing inductor disposed in the second rectification path, the feedback inductor being galvanically isolated from the second current sensing inductor, magnetically coupled to the second current sensing inductor, and configured to modify the electrical signal passing through the feedback inductor in response to a current flowing through the second current sensing inductor, and the current sensing circuitry also being adapted to sense the current flowing through the second current sensing inductor via the electrical signal. Such embodiments are particularly useful when the rectified currents in the two phases are not systematic and therefore the first and second current sensing inductors are used to measure them, respectively.

[0018] The current sensing circuit may include a rectifier circuit coupled between the feedback inductor and the filter.

[0019] This rectifier circuit provides the filter with a single-phase signal, making it easier for the filter and downstream circuitry to process it.

[0020] In at least one example, the fault comprises any one of a short circuit, an open circuit, or a poor connection of the output terminal and / or the load.

[0021] These faults cause abrupt / large changes in the current through the fault detection inductor, thus changing the electrical parameters in the feedback inductor. Embodiments of the present invention are able to detect these faults, providing reliability to the drive circuit.

[0022] The drive circuit may further comprise a signal processing circuit configured to process the fault feedback signal to determine the presence or absence of the fault.

[0023] In some examples, the feedback inductor is configured to modify the electrical parameter in response to a current through the fault detection inductor being greater than 150% of a rated normal output current of the drive circuit. In particular examples, the feedback inductor may be configured to modify the electrical parameter in response to a change in current through the fault detection inductor.

[0024] The detector may include a resistive element connected between the positive terminal of the feedback inductor and ground or a reference voltage.

[0025] A drive arrangement is also proposed comprising a drive circuit as described herein and said converter arranged to supply power to said drive circuit.

[0026] In at least one example, the transformer is an isolated transformer comprising a primary winding and a secondary winding galvanically isolated from and magnetically coupled to the primary winding, and the drive circuit is connected to the secondary winding. The galvanically isolated drive circuit is well suited to such an isolated transformer configuration, providing inherent isolation between the feedback inductor and the secondary winding.

[0027] In some examples, the converter has an LLC and / or LCC conversion configuration.

[0028] In some examples, the converter includes a controller electrically connected to the primary winding and the feedback winding and configured to control the power supplied to the drive circuit via the secondary winding in response to at least the fault feedback signal.

[0029] In this embodiment, the feedback winding may be electrically connected to the primary side controller to provide the signal thereto that advantageously meets isolation regulations.

[0030] In some examples, the controller is configured to, in response to the fault feedback signal indicating that the fault is present, cause the drive arrangement to enter a protective mode in which power is not supplied to the drive circuitry.

[0031] Optionally, the controller is configured to operate the drive arrangement in a drive mode and adjust the power supplied to the drive circuit in response to the current feedback signal.

[0032] The controller may have several different pins, a fault input pin connected to an unfiltered signal that includes the fault feedback signal, and a normal current sense pin connected to the filtered signal that is the current feedback signal without the fault feedback signal, and the controller operates or acts according to the respective signals received at the respective pins.

[0033] In at least one example, when operating in the drive mode, the controller is configured to adjust the current supplied to the drive circuit to meet a reference current by monitoring the current feedback signal with respect to a target.

[0034] These and other aspects of the invention will be elucidated and elucidated with reference to the following embodiments. [Brief explanation of the drawings]

[0035] For a better understanding of the present invention, and to show more clearly how the same may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which: [Figure 1] 1 illustrates a driving circuit according to an embodiment. [Figure 2] 4 shows waveforms illustrating the operation of the driver circuit. [Figure 3] 1 illustrates a drive arrangement according to an embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0036] The present invention will be described with reference to the drawings.

[0037] It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the devices, systems, and methods, are for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the devices, systems, and methods of the present invention will become better understood from the following description, appended claims, and accompanying drawings. It should be understood that the figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the figures to indicate the same or similar parts.

[0038] The present invention provides a drive circuit and drive configuration for driving a load between two output terminals. The drive circuit has an input and an output terminal connected to the input. A fault detection inductor is connected in series with the output terminal and configured to modify an electrical parameter through a feedback inductor in response to a change in current between the output terminals. The feedback inductor is galvanically isolated from the fault detection inductor but magnetically coupled to it.

[0039] In any of the described embodiments, the term "terminal" is considered interchangeable with the term "node" and refers to a portion of a wire or a point in a circuit. The term "current" refers to an electric current.

[0040] 1 is a circuit diagram illustrating a driver circuit 100 according to an embodiment. The driver circuit 100 is configured to supply power generated by a converter (not shown) to a load 90. In the illustrated example, the load 90 includes a first light-emitting diode D3 and a second light-emitting diode D10 connected in series, but these components can be replaced with any other load suitable for the driver circuit. The capacitor C5 is an EMI capacitor, i.e., it functions to attenuate any current induced by electromagnetic interference (EMI). Note that this capacitor C5 is optional.

[0041] The driver circuit 100 has an input 110 adapted to receive power from a converter, where the input 110 has a first input terminal 111 and a second input terminal 112 configured to connect to the converter.

[0042] The driver circuit also has output terminals 121, 122 adapted to be connected to a load for supplying the received power to the load. Here, the output terminals include a first output terminal 121 connected to receive power from the input 110 and a second output terminal 122 connected to ground or a reference voltage GND. The first output terminal and the second output terminal 122 are connected to either side of the load 90. Thus, current can flow from the input 110 to the first output terminal 121, through the load 90 to the second output terminal 122, and then to ground or a reference voltage.

[0043] Alternative suitable configurations of input 110 and output terminals 121, 122 will be apparent to those skilled in the art. For example, input 110 may include only a single node or terminal, such as terminal 113, for connecting to a transducer.

[0044] The driver circuit 100 also includes a fault detection inductor L8 (or winding) electrically connected in series with the output terminal. In the illustrated example, the fault detection inductor is connected in series between the second output terminal 122 and ground or a reference voltage GND. In an alternative example, the fault detection inductor can be connected between the input 110 and the first output terminal 121.

[0045] In this manner, any current flowing through output terminals 121, 122 and load 90 also passes through fault detection inductor L8. In normal operation, current from the driver circuit to the load is smooth / steady and passes through or is conducted by inductor L8 without causing significant voltage changes. However, a fault between output terminals 121, 122 causes or induces a sudden / large change in current through fault detection inductor L8. Faults between the output terminals include a short or open circuit in load 90 itself or a poor connection at output terminals 121 and 122. For example, when the load or terminals suddenly open, the current through inductor L8 suddenly stops, introducing a negative voltage at the dot / positive terminal at inductor L8; when the load or terminals are shorted, the current through inductor L8 rises (even though inductor L8 prevents the rise), introducing a positive voltage at the dot / positive terminal at inductor L8. Note that if a large output buffer capacitor C1 (described below) is present, a fault will still cause a change in the current through fault detection inductor L9 because the fault detection inductor is after output buffer capacitor C1, but inductors L3 and L6 (described below) will not tolerate such a change in current because buffer capacitor C1 somewhat filters out or attenuates the fault or its effects before inductors L3 and L6.

[0046] The drive circuit 100 also includes a feedback inductor L7 that is galvanically isolated from and magnetically coupled to the fault detection inductor L8. Therefore, an electrical parameter through the feedback inductor changes or is altered in response to the above-mentioned sudden change in the current through the fault detection inductor L8. In particular, a change in the current through the fault detection inductor (e.g., as a result of a fault) results in a change in the current through the feedback inductor L7.

[0047] This is an effect of Faraday's law of electromagnetic induction, as will be readily apparent to those skilled in the art. More specifically, a change in the current through the fault detection inductor changes the magnetic field generated by the fault detection inductor. This change in magnetic field causes a change in the current through the magnetically coupled feedback inductor (e.g., induces a current in the feedback inductor), resulting in a change in an electrical parameter, more specifically, a change in the current, through feedback inductor L7.

[0048] The drive circuit 100 also includes a detector R6 that detects changes in the electrical parameter across the feedback inductor and generates a fault feedback signal S in response to the detected changed electrical parameter. F In the example shown, detector R6 comprises a resistive element (i.e., a resistor) connected between one pole / terminal (or both poles / terminals) of feedback inductor L7 and ground or reference voltage GND. Thus, a change in the current through the feedback inductor causes an abrupt change in the voltage across the detector's resistive element. The voltage V(R6) across the detector's resistive element thereby generates a fault feedback signal S F can play the role of

[0049] Note that detector R6 does not include a capacitor in parallel with the resistive element. This prevents smoothing of the voltage across the resistive element and reduces the magnitude of the fault feedback signal S. Fensures that the resistor element provides a significant spike or response to faults in the load. If such a capacitor is provided, e.g., for EMI attenuation, the capacitance of the capacitor in parallel with the resistive element is preferably very small (e.g., <0.2 μF) to reduce the effect of low frequency filtering.

[0050] Fault feedback signal S F provides useful information about the state of the output terminals and / or load, in particular whether a fault has occurred across the output terminals and / or in the load. This information can be used for various purposes, for example to shut down the drive circuit for improved safety or to otherwise control the current supplied to the drive circuit, for example by a converter.

[0051] For example, a surge current between the output terminals 121, 122 (e.g., due to a short circuit) will cause the current through the fault detection inductor L8 to suddenly rise. A surge current is a sudden change, e.g., an increase, in current between two points in a circuit. For example, a surge current may be caused by, e.g., switching on a load or part of a load, causing the load to suddenly start drawing more power. The surge current may disadvantageously damage the drive circuit. To detect such a fault, a fault feedback signal S F The use of a rectifier is advantageous for responding appropriately to surge currents.

[0052] The proposed approach provides a mechanism for accurately identifying faults between the output terminals while keeping the fault identification mechanism galvanically isolated from the output terminals, which improves the safety of the drive circuit and reduces, for example, stray currents from reaching ground through a load connected between the output terminals, which may be an unintentional human connection.

[0053] 1 also illustrates an optional feature of the driver circuit 100: an output capacitor C1. The output capacitor C1 is connected in parallel with the output terminals 121, 122 and is adapted to smooth the power received from the converter, i.e., the power received at the input 110. The output capacitor C1 thereby acts as an output buffer capacitor. In the particular example shown, the output capacitor is connected between the input 110 and ground or a reference voltage GND. Thus, the driver circuit has an output capacitor for storing the power received from the converter at the input 110, and the output terminals are electrically connected to the output capacitor for supplying the power stored by the output capacitor to a load.

[0054] The use of output capacitor C1 means that a consistent, nearly DC current or voltage can be supplied to output terminals 121, 122 and load 90. The capacitance of capacitor C1 is typically 22 μF, but may be in the range of 5 μF to 50 μF, for example between 10 μF and 40 μF, e.g., 22 μF.

[0055] A fault detection inductor L8 may be electrically connected between the output capacitor C1 and the output terminals 121, 122. Connecting the fault detection inductor L8 between the output capacitor C1 and the output terminals makes the fault detection inductor L8 very sensitive to high frequency (kHz to MHz) current changes that may result from faults such as short circuits or open circuits across the output terminals or in the load.

[0056] If a fault detection inductor is connected before the output capacitor (e.g., between the input 110 and the capacitor), the current smoothing provided by the capacitor will mask or hide the sudden change due to the fault across the output terminals.

[0057] The illustrated drive circuit 100 also includes an optional feature: a diode bridge 130 formed from multiple (e.g., Zener) diodes. This serves to isolate or decouple the feedback inductor L7 from other signals present in circuits connected to or not galvanically isolated from the feedback inductor. The diode bridge 130 also serves to make the fault feedback signal a single polarity signal, improving ease and simplicity of fault identification. Thus, it is not important whether the fault results in a positive or negative change in an electrical parameter (e.g., across the fault detection inductor L8), but rather, only that such a change occurred. In any case, if the drive circuit needs to determine the type of fault from the induced voltage in the fault feedback winding, the rectifier can be omitted and a polarity detection circuit can be added.

[0058] The illustrated driver circuit 100 further includes an optional feature, a filter capacitor C5, which is configured to filter out very high frequency components from passing to the load. The filter capacitor C5 is connected in parallel with the load 90, which is connected to the output terminals 121, 122.

[0059] Further optional features of the drive circuit are described below.

[0060] The driver circuit may include a rectifier arrangement 140, here formed from a diode bridge D1, D2, D4, D5. The rectifier arrangement 140 is configured to rectify the power provided by the converter at the input 110. The rectified power is provided to the output terminals 121, 122. In some examples, if an output capacitor C1 is present, the output capacitor C1 may smooth or store the rectified power provided to the output terminals.

[0061] The rectifier arrangement 140 may be omitted, for example, if a similar or identical circuit is formed in the converter itself, e.g., the converter provides rectified power to the input. In such an example, the input may have a single terminal, e.g., terminal 113, for connection to the converter.

[0062] The rectifier configuration has or defines a first rectification path and a second rectification path. Each rectification path provides a positive voltage / current to the output terminal and / or output capacitor (if present). This is full-wave rectification. Those skilled in the art will understand that half-wave rectification is also possible and / or applicable, in which only one of the first rectification path and the second rectification path is required and the other is not / is removed.

[0063] The drive circuit may include a first current sensing inductor L3 disposed in the first commutation path. A feedback inductor L7 is galvanically isolated from and magnetically coupled to the first current sensing inductor L3. The feedback inductor L7 is configured to modify an electrical parameter, more specifically, to modify the current flowing through the feedback inductor in response to the current flowing through the first current sensing inductor.

[0064] Optionally, magnetically coupled inductor L7 is responsive to current through the first current sensing inductor or the fault sensing inductor changing at a rate of 0.1 A / μs or faster.

[0065] The drive circuit 100 may further include a current sensing circuit 150 for sensing the current through the first current sensing inductor. The current sensing circuit 150 is a filter configured to generate a filtered signal Vsense, which is a filtered version of the current through the feedback inductor relative to the current through the first current sensing inductor. In the filtered signal Vsense, the current component induced in the feedback inductor by the fault sensing inductor has been filtered or attenuated.

[0066] The signal Vsense is the current feedback signal S C can be represented as:

[0067] Because the current component induced by the fault detection inductor when a fault occurs across the output terminals has a much higher amplitude than the signal related to the detected current in the current detection inductor, the averaging circuit as a filter can distinguish or separate the two signals. The illustrated filter 150 is an RC filter formed by a resistor R11 and a capacitor C6 connected in parallel between the node / arm of the feedback inductor L7 and ground or a reference voltage GND. The capacitance of the capacitor C6 may be 4.7 μF to effectively filter out high-frequency noise and transient high signals (including the fault feedback signal). The voltage across the resistor R11 serves as the filtered signal Vsense. The filtered signal Vsense serves as a current feedback signal, providing feedback on the current supplied by the converter to the drive circuit. This information can be used, for example, to control the operation of the converter to ensure that the desired current is supplied to the converter. The signal S, which is not filtered by the RC filter, F The peak amplitude of still carries the information induced by the fault detection inductor and can be detected to determine the fault.

[0068] In another example, the di / dt of the fault current signal is higher than the normal operating current signal, and therefore a frequency selector can be used to distinguish or separate the two signals.

[0069] For example, the detector may generate a fault feedback signal S F The filter 150 may be configured to pass high frequency signals in the feedback inductor and, optionally, attenuate low frequency signals in the feedback inductor, so as to function as a current feedback signal S CThe frequency selector may be configured to attenuate high frequency signals in the feedback inductor and pass low frequency signals in the feedback inductor so as to function as a frequency selector. In this manner, the frequency selector may provide two signals that separately distinguish or represent the (normal) current provided to the output terminal and the occurrence of a fault.

[0070] This approach results in any sudden spikes being filtered from the current feedback signal. Attenuating high frequency signals may include attenuating signals having frequencies greater than 1.5 times, e.g., greater than 2 times, the frequency of the current supplied by the converter to the drive circuit.

[0071] The drive circuit may include a second current sensing inductor L6 disposed in the second commutation path. As with the first current sensing inductor, the feedback inductor is galvanically isolated from the second current sensing inductor, magnetically coupled to the second current sensing inductor, and configured to modify the current through the feedback inductor in response to the current through the second current sensing inductor.

[0072] The current sensing circuit 150 is also adapted to sense the current through the second current sensing inductor L6, which improves the accuracy of the current sensing performed by the filter 150.

[0073] The two currents in the first and second current sensing inductors are rectified and averaged (by an RC filter) to produce a signal S as the total current from the converter through the drive circuit to the load. C In this manner, the current detection circuit 150 can sense the current supplied to the output terminals (and / or the output capacitor C1, if present).

[0074] During normal operation, the current supplied by the converter passes through the first inductor L3 and (if present) the second inductor L6 and is reflected in the feedback inductor L7 via magnetic coupling. This regulates the load current supplied to the converter, thereby producing a filtered signal Vsense that can be detected and used to regulate the load current.

[0075] The use of output capacitor C1 means that the current generated directly by the converter is approximately DC or close to DC when passing through the fault feedback inductor L8, and therefore this has little effect on the fault feedback signal, and therefore the signal in inductor L7 is approximately the current sense signal from inductors L3 and L6.

[0076] FIG. 2 illustrates waveforms at / through various components of the driver circuit to illustrate the advantages of the proposed driver circuit.

[0077] A first waveform 201 illustrates the current -I(L8) through the fault detection inductor, indicating the occurrence of a fault in the load at time T1. When a fault occurs in the load, there is a spike in the current through the fault detection inductor. At other times, the current through the fault detection inductor is approximately constant.

[0078] A second waveform 202 illustrates the voltage −V(R6) across the resistive element of detector R6, which shows the same spike at time T1. The voltage −V(R6) is the voltage across the fault feedback signal S FThis peak amplitude / spike is detected and used for fault feedback as described above. At other times when there is no fault, the voltage at R9 is also smooth. The detection threshold can be set to at least 150% of the DC offset. This is based on the fact that the output capacitor smooths the current from the converter, so the current at the output terminals must not vary by more than 150% of the rated output current, and if said current exceeds 150% of the rated output current, something may be wrong and a fault is considered to have occurred.

[0079] For improved safety margin, the detection threshold may be set to 200% or more of the DC offset. Those skilled in the art may specify other thresholds according to practical case scenarios, such as average output current (DC offset), LED forward voltage, etc.

[0080] The third waveform 203 is the current I passing through the third terminal 113. 113 is shown, representing the current supplied to the output capacitor C1, i.e., the current supplied by the converter (which may be rectified by the drive circuit or the converter itself, as will be explained later). This shows how the effect of the power supplied to the output terminals on the fault feedback signal is small or negligible compared to a fault between the output terminals. Note that the DC offset in V(R6) and the DC offset in V(R11) depend on this current.

[0081] The fourth waveform 204 illustrates the voltage V(R11) across resistor R11 of filter 150. The DC offset in V(R11) is primarily due to the DC offset of the current I 113 This waveform is also used to measure the occurrence of a fault, which can be detected by resistor R11, and therefore the filtered signals Vsense, S CHowever, the variations are much smaller than the response of the voltage -V(R6) across the resistive element of detector R6, e.g. the average current, which does not have a peak variation of more than 50% of the average current, and is therefore not very useful and in fact is not used to indicate any potential fault, but is used for current control in normal operation.

[0082] Note that Figure 2 is only for illustrating the relationship between signals and switching: in a real use case scenario, the moment a spike in -V(R6) is detected at time T1, the drive circuit may signal the converter to stop operation, and there may be no further signals on those components.

[0083] Figure 3 illustrates a drive arrangement 1 comprising the aforementioned drive circuit 100. The drive arrangement 1 itself may form an embodiment.

[0084] The drive arrangement 1 also includes a converter 50 configured to provide power to the drive circuit. The converter 50 converts the power provided by a power source or power supply V1, R1, and C3 to power the drive circuit 100. The power source is modeled by a DC power supply with an output impedance R1. Capacitor C3 is configured to filter out or attenuate any AC components of the DC power supply, thereby acting as a decoupling capacitor. Suitable examples of DC power supplies include a battery, a power cell, or a rectified (and preferably smoothed) and power factor corrected AC power supply, such as a mains power supply.

[0085] The illustrated transformer 50 is an isolated transformer comprising a primary winding 51 and a secondary winding 52 that is galvanically isolated from and magnetically coupled to the primary winding 51. A drive circuit 100, and in particular an input 110 of the drive circuit 100, is connected to the secondary winding.

[0086] The converter 50 may have an LLC and / or LCC converter topology. Here, the converter has an LLC converter topology formed by two inductors L4, L5 and a capacitor C4, and a switch network (half-bridge) formed by a first switch Q1 and a second switch Q2. The first and second switches may be MOSFETs. The topology and operation of LLC converter topology are well known to those skilled in the art and will not be described for the sake of brevity. Generally, LLC converter topology is configured to supply AC power (at the secondary winding) from an AC / DC converter or a DC power source such as a cell or battery.

[0087] The conversion arrangement can be replaced by any other suitable conversion arrangement, which may depend on the nature of the power source. An example is a buck / boost / buck-boost converter for converting an AC power source, such as a mains power source, into an AC current for the first winding. Other examples will be apparent to those skilled in the art.

[0088] The drive arrangement 1 may also comprise a controller 55. The controller receives at least a fault feedback signal S F responsive to the power supplied to the drive circuit via the second winding. More specifically, the controller 55 may control the operation of the switch network, and thereby the operation of the LLC conversion arrangement.

[0089] In some examples, the controller is configured to, in response to the fault feedback signal indicating the fault exists, cause the drive arrangement to enter a protection mode in which power is not supplied to the drive circuit. Protection mode may be implemented, for example, by keeping first switch Q1 open so that no current flows through first winding 51. Other techniques for entering protection mode will be apparent to those skilled in the art.

[0090] The fault feedback signal may indicate the presence of a fault when the voltage of the fault feedback signal exceeds a certain predetermined value, indicating a current spike across the output terminals. The predetermined value may be 150% or more, such as 200% or more, of the value of the fault feedback signal when no fault occurs, e.g., the value of the DC offset of the fault feedback signal.

[0091] In certain examples, the fault feedback signal may indicate the presence of a fault if the voltage of the fault feedback signal indicates that the current through the resistive element of detector R6 exceeds a predetermined number (e.g., 1.5, 2, 5, or 10 times) greater than the peak current when no fault occurs, e.g., during normal operation. Referring to Figure 2, normal operation is represented by a ripple in the voltage across detector R6.

[0092] In another example, the fault feedback signal may indicate the presence of a fault if the slope of the fault feedback signal exceeds a certain predetermined slope value, indicating the occurrence of a current spike across the output terminals. The predetermined slope value may be a value that is 150% or more, such as 200% or more, of the maximum slope of the fault feedback signal when no fault is present, e.g., the slope induced in the fault feedback signal by normal operation of the converter.

[0093] The controller 55 may be configured to process the fault feedback signal to identify the presence or occurrence of a fault. Accordingly, the controller 55 may compare the fault feedback signal to one or more predetermined thresholds or ranges to determine or predict whether the fault feedback signal indicates the presence or absence of a fault.

[0094] In some examples, the controller may be configured to operate the drive arrangement in a drive mode and adjust the power supplied to the drive circuit in response to the current feedback signal. The controller may be configured to operate in the drive mode when no faults have been identified by the fault feedback system (e.g., since start-up), and / or when a predetermined period of time has elapsed since the last fault was identified by the fault feedback, and / or in response to user input.

[0095] Thus, the controller 55 may receive user input, for example from a user interface system such as a button or other communication device, to configure the controller to operate in a drive mode. Of course, the user input may also / otherwise be used to define other characteristics of the controller, such as the reference current, the power supplied to the converter, the operating mode, etc.

[0096] In some examples, when operating in drive mode, the controller is configured to adjust the current supplied to the drive circuit to meet a reference current by monitoring a current feedback signal related to the target. Techniques for defining an appropriate reference current, such as using a voltage divider, will be readily apparent to those skilled in the art.

[0097] The controller 55 may receive the current feedback signal and the fault feedback signal through different input pins, as shown by Figure 3. For example, the fault feedback signal S F may be received at the first input pin 56, and the current feedback signal S C may be received at the second input pin 57.

[0098] The drive arrangement 1 may comprise an amplifier arrangement 80. The amplifier arrangement may be configured to receive a fault feedback signal S F and the current feedback signal S, if present. C The amplifier arrangement 80 is configured to amplify the fault feedback signal S Fa first amplifier 81 for amplifying a current feedback signal S C and a second amplifier 82 for amplifying the

[0099] References to a fault feedback signal and / or a current feedback signal may refer to an amplified version of the respective signal. For example, first input pin 56 may receive a fault feedback signal S F , and a second input pin 56 may receive an amplified or unamplified version of the current feedback signal S C The receiver may receive amplified or unamplified versions of the signal.

[0100] In the above embodiment, the first current sensing inductor is in the rectification path of the rectifier. This embodiment does not limit the scope of the claims. In other embodiments, with or without a rectifier, the first current sensing inductor can be placed anywhere through the operating current supplied to the load such that the first current sensing inductor senses the operating current.

[0101] Those skilled in the art can understand and effect variations to the disclosed embodiments in practicing the claimed invention, from a study of the drawings, the specification and the appended claims. In the claims, the word "comprises" does not exclude other elements or steps, and the singular does not exclude a plurality.

[0102] The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. It should be noted that where the term "adapted to" is used in the claims or the description, the term "adapted to" is intended as equivalent to the term "configured to". It should be noted that where the term "arrangement" is used in the claims or the description, the term "arrangement" is intended as equivalent to the term "system", and vice versa. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. 1. A drive circuit for supplying power generated by a converter to a load, comprising: an input adapted to receive power from the converter; two output terminals adapted to be connected to a load to supply the received power to the load; a fault detection inductor electrically connected in series with the two output terminals such that current flowing through the two output terminals and the load passes through the fault detection inductor, such that a fault between the two output terminals causes a change in current flowing through the fault detection inductor; a first current sensing inductor through which the current supplied by the converter passes; a feedback inductor, the feedback inductor being galvanically isolated from the fault detection inductor and magnetically coupled to the fault detection inductor and configured to modify a fault feedback current through the feedback inductor in response to a change in current through the fault detection inductor, the feedback inductor also being galvanically isolated from the first current detection inductor and magnetically coupled to the first current detection inductor and configured to induce a first feedback current through the feedback inductor in response to a current through the first current detection inductor; a detector configured to detect a change in the fault feedback current through the feedback inductor and to generate a fault feedback signal in response to the detected changed fault feedback current; a current detection circuit that detects a current flowing through the first current detection inductor based on the first feedback current.

2. an output capacitor connected in parallel with the two output terminals and adapted to smooth the received power from the converter; 2. The drive circuit of claim 1, wherein the fault detection inductor is electrically connected between the output capacitor and one of the two output terminals.

3. 2. The drive circuit of claim 1, wherein the fault includes any one of a short circuit, an open circuit, or a poor connection of the two output terminals and / or the load.

4. The drive circuit of claim 1 , further comprising a signal processing circuit configured to process the fault feedback signal to determine the presence or absence of the fault.

5. 5. The drive circuit of claim 4, wherein the signal processing circuit is configured to determine that the fault exists when the current through the fault detection inductor exceeds 150% of the rated normal output current of the drive circuit.

6. 2. The drive circuit of claim 1, wherein the detector comprises a resistive element connected between the positive terminal of the feedback inductor and ground or a reference voltage.

7. A drive circuit according to any one of claims 1 to 6; and the converter configured to supply power to the drive circuit.

8. 8. The drive arrangement of claim 7, wherein the transformer is an isolated transformer comprising a primary winding and a secondary winding galvanically isolated from and magnetically coupled to the primary winding, and the drive circuit is connected to the secondary winding.

9. 8. A driving arrangement according to claim 7, wherein the converter comprises an LLC and / or LCC conversion arrangement.

10. 9. The drive arrangement of claim 8, wherein the converter comprises a controller electrically connected to the primary winding and the feedback inductor and configured to control the power supplied to the drive circuit via the secondary winding in response to at least the fault feedback signal.

11. 11. The drive arrangement of claim 10, wherein the controller is configured to, in response to the fault feedback signal indicating that the fault is present, cause the drive arrangement to enter a protective mode in which power is not supplied to the drive circuit.

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