Output voltage sensing protection device and method

Abstract

The invention relates to an output voltage sensing protection device and method. A control circuit and a corresponding method are presented. The control circuit may be configured to control the power converter. The control circuit may be configured to receive a voltage signal indicative of an output voltage at an output of the power converter. The control circuit may be configured to receive a current signal representative of an output current at an output of the power converter. The control circuit may be configured to determine a fault condition associated with the voltage signal based on the current signal and based on the voltage signal. By determining a fault condition based on an analysis of the sensed output voltage and the sensed output current, the fault condition can be detected in a simple and efficient manner.

Description

Technical Field

[0001] The present invention relates to output voltage sensing protection devices and methods. In particular, the present invention relates to techniques for detecting faulty measurements of the output voltage of a power converter and for protecting a load at the output of the power converter from excessive voltage. Background Art

[0002] Due to assembly issues, the output voltage sense line that reports the output voltage at the output of the power converter can be affected by an open circuit or a short circuit. The controller responsible for controlling the power converter may incorrectly assume that the output voltage is still at a low voltage level. This can be particularly problematic during the startup of the power converter: the controller can continue to increase (a) the pulse width and / or (b) the frequency of the pulses transmitted to the power converter to increase the power flow in the power converter. This can result in an excessively high output voltage, which can damage expensive output loads (such as CPUs, ASICs, FPGA devices, etc.).

[0003] It is therefore an object of the present invention to provide an efficient apparatus and method for detecting an incorrectly sensed value of an output voltage of a power converter. Summary of the Invention

[0004] According to one aspect, a control circuit is provided. The control circuit may be configured to control a power converter. The control circuit may be configured to receive a voltage signal indicating an output voltage at an output of the power converter. The control circuit may be configured to receive a current signal indicating an output current at the output of the power converter. The control circuit may be configured to determine a fault condition associated with the voltage signal based on the current signal and the voltage signal.

[0005] The power converter can be, for example, a switched mode power supply (SMPS). As will be discussed in more detail below, the power converter can be a multiphase power converter, wherein each phase can include a power stage coupled in series with an inductor. The phases can be coupled in parallel, and the output currents of the inductors can be summed at the output of the power converter to form the output current of the power converter. As will be discussed below, the current signal can include multiple phase current signals for each phase of the power converter.

[0006] The control circuit may include one or more processors for implementing or at least initiating the functional features of the control circuit described herein. Specifically, the control circuit may include a microcontroller MCU for performing the functions described.

[0007] The features of the control circuit described herein, and in particular the functional features of the control circuit, may be implemented by corresponding software or hardware units, or by a combination of the two. The hardware units may be implemented using digital circuit elements or analog circuit elements, or by a combination of the two.

[0008] By determining a fault condition based (solely) on an analysis of the sensed output voltage and the sensed output current, a fault condition can be detected in a simple and effective manner. In particular, fault detection can be implemented solely on the control circuit by updating the control circuit firmware, and no additional hardware elements (such as current sources, comparators, or other analog circuit devices) are required.

[0009] If the value of the current signal exceeds the current fault threshold and if the value of the voltage signal is below the voltage fault threshold, the control circuit can be configured to determine a fault condition. More specifically, the control circuit can be configured to determine a fault condition if, at a certain point in time, the value of the current signal exceeds the current fault threshold and if, at approximately the same point in time, the value of the voltage signal is below the voltage fault threshold.

[0010] In this way, it is possible to detect fault conditions in which the output signal may not correctly represent the actual output voltage at the output of the power converter. Conventionally, for example, during startup of the power converter, when the output current increases, the actual output voltage increases. However, if the voltage sensing is not working correctly (e.g., due to a short circuit or an open circuit), the sensed output voltage will erroneously indicate a low output voltage, even though the actual high output voltage could damage the load at the output of the power converter. By detecting the increased output current and the non-increased output voltage, this fault condition can be detected in an efficient manner.

[0011] The control circuit may include a current comparator and a voltage comparator, wherein the current comparator is configured to compare the value of the current signal with a current fault threshold, and the voltage comparator is configured to compare the value of the voltage signal with a voltage fault threshold. Both the current comparator and the voltage comparator may be implemented by software running on a microcontroller of the control unit. Alternatively, the comparator may be implemented using a hardware circuit.

[0012] The control circuit can be configured to synchronize the operation of the current comparator and the voltage comparator so that the two comparisons are performed at approximately the same time point. This time point can be used, for example, during the startup time of the power converter for early detection of a fault voltage signal. The control circuit can further include a logic AND gate, wherein the output of the current comparator is coupled to a first input of the logic AND gate, and wherein the output of the voltage comparator is coupled to a second input of the logic AND gate. The output of the logic AND gate can indicate a fault condition. Similarly, the logic AND gate can be implemented in software or hardware.

[0013] The control circuit can be configured to determine a maximum value of the current signal within a predetermined time interval. The control circuit can be configured to use the maximum value as the value of the current signal for determining a fault condition. For example, the control circuit can include a hardware or software timer for implementing the predetermined time interval.

[0014] The control circuit can be configured to determine a maximum value of the voltage signal within a predetermined time interval. The control circuit can be configured to use the maximum value as the value of the voltage signal for determining a fault condition. Thus, the control circuit can be configured to determine a fault condition if the maximum value of the current signal exceeds a current fault threshold and if the maximum value of the voltage signal is below a voltage fault threshold.

[0015] The control circuit can be configured to start the predetermined time interval when a first pulse width modulation (PWM) pulse is transmitted from the control circuit to the power stage of the power converter. Thus, the predetermined time interval can begin exactly when startup of the power converter begins. In response to receiving the first PWM pulse, a switching element (e.g., a high-side switching element) of the power stage can be turned on to initiate current and power flow with the power converter.

[0016] The control circuit may be configured to compare the maximum value of the current signal with a current fault threshold value just after a predetermined time interval has elapsed.Similarly, the control circuit may be configured to compare the maximum value of the voltage signal with a voltage fault threshold value just after a predetermined time interval has elapsed.

[0017] The control circuit can be configured to receive a voltage signal via an external output voltage sense line. The fault condition associated with the voltage signal can be associated with an open circuit condition or a short circuit condition, wherein the open circuit condition or the short circuit condition is associated with the external output voltage sense line. Due to the fault condition, the voltage signal can indicate an output voltage that is lower than the true / actual output voltage at the output of the power converter. In particular, due to the open circuit or the short circuit, the voltage signal can indicate an output voltage of approximately 0V, while the true output voltage is substantially higher than 0V.

[0018] The control circuitry may be configured to shut down the power converter in response to determining a fault condition. For example, the control circuitry may be configured to send a control signal to the power converter in response to determining the fault condition to shut down one or more switching elements of the power converter. The control circuitry may be configured to transmit a PWM signal to the power converter to drive a switch of the power converter, and in response to determining the fault condition, stop increasing the duty cycle of the PWM signal.

[0019] The power converter may be a multiphase power converter. The control circuit may be configured to receive a plurality of phase current signals indicating currents of different phases of the multiphase power converter. The control circuit may be configured to determine the current signal based on the phase current signals. For example, the control circuit may be configured to determine the current signal based on a linear combination of the phase current signals. In particular, the control circuit may be configured to determine the current signal by summing the phase current signals.

[0020] According to yet another aspect, a method for controlling a power converter is provided. The method may include steps corresponding to the functional features of the control circuit described throughout this document. Specifically, the method may include receiving, by the control circuit, a voltage signal indicating an output voltage at an output of the power converter. The method may include receiving, by the control circuit, a current signal indicating an output current at the output of the power converter. The method may include determining, by the control circuit, a fault condition associated with the voltage signal based on the current signal and based on the voltage signal.

[0021] The determining step may include determining a fault condition if the value of the current signal exceeds a current fault threshold and if the value of the voltage signal is below a voltage fault threshold.

[0022] The method may include determining a maximum value of the current signal within a predetermined time interval and using the maximum value as the value of the current signal for determining the fault condition.

[0023] The method may comprise comparing, by a current comparator, a (maximum) value of the current signal with a current fault threshold.The method may comprise comparing, by a voltage comparator, a value of the voltage signal with a voltage fault threshold.

[0024] The method may include determining, by the control circuit, a maximum value of the voltage signal within the predetermined time interval. The method may include using, by the control circuit, the maximum value as a value of the voltage signal for determining a fault condition. The method may include determining, by the control circuit, a fault condition if the maximum value of the current signal exceeds a current fault threshold and if the maximum value of the voltage signal is below a voltage fault threshold.

[0025] The method may include initiating, by the control circuit, a predetermined time interval when a first pulse width modulated (PWM) pulse is transmitted from the control circuit to a power stage of the power converter.

[0026] The method may include receiving, by the control circuit, a voltage signal via an external output voltage sense line. The fault condition associated with the voltage signal may be associated with an open circuit condition or a short circuit condition associated with the external output voltage sense line. The method may include shutting down, by the control circuit, the power converter in response to determining the fault condition. The method may include transmitting, by the control circuit, a PWM signal to the power converter to drive a switch of the power converter. The method may include stopping, by the control circuit, increasing a duty cycle of the PWM signal in response to determining the fault condition.

[0027] According to a third aspect, a computer program is provided. The computer program may include instructions that, when executed by one or more processors of a control circuit, cause the control circuit to perform the operations described herein.

[0028] The computer program may be, for example, software / firmware loaded into a memory of the control circuit. To this end, the computer program may be transmitted over a network, and the control circuit may include a network interface device for receiving the computer program. Alternatively, the computer program may be distributed on a data carrier and downloaded to the control circuit. Typically, the computer program may be stored on a non-transitory computer-readable medium. Disclosed herein is a non-transitory computer-readable medium storing instructions that, when executed by one or more processors of the control circuit, cause the control circuit to perform the steps described herein.

[0029] It should be noted that the methods and systems, including the preferred embodiments thereof, outlined herein, can be used alone or in combination with other methods and systems disclosed herein. Furthermore, features outlined in the context of a system also apply to the corresponding method. Furthermore, all aspects of the methods and systems outlined herein can be combined in any manner. In particular, features of the claims can be combined with one another in any manner.

[0030] In this document, the terms "couple" or "coupled" refer to elements that are in electrical communication with each other, whether directly, for example, via a wire, or indirectly, via other circuit elements between them. For example, two elements may be said to be coupled even if there is a circuit element, such as a switch (which can be turned on and off), between the two elements. On the other hand, the terms "connect" or "connected" refer to elements that are directly electrically connected to each other, for example, via a wire, and no circuit elements are located between them. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention is illustrated by way of example, and not limitation, in the accompanying figures and in which like references indicate similar or identical elements, and in which:

[0032] Figure 1 shows an exemplary power converter with a control circuit,

[0033] Figure 2 Exemplary signal waveforms of a power converter without the claimed overvoltage sensing protection are shown.

[0034] Figure 3 shows an exemplary functional diagram of a control circuit according to the present invention, and

[0035] Figure 4 Results of experiments with and without OSP controls are shown. DETAILED DESCRIPTION

[0036] Figure 1 An exemplary power converter 2 with a control circuit 1 is shown. The power converter has an input 21 and an output 26. In the example shown, the power converter 2 is a multiphase power converter. Since the power converter is a step-down type, the output voltage is typically lower than the input voltage, and the output current is higher than the input current. This is particularly true because different phase currents are accumulated at the output 26 of the power converter. The multiphase power converter 2 includes a plurality of parallel power stages 221, 222, 223 having corresponding switching elements 231, 232, 233, which are controlled by corresponding control signals (e.g., PWM signals) transmitted by the control circuit 1. Each phase of the power converter includes a corresponding inductor 241, 242, 243 connected in series with the corresponding power stage. The inductor current is sensed via sense lines 251, 252, 253 and reported to the control circuit 1. Depending on the distance between the sensing point and the control circuit 1, the sense lines can be distinguished as local or remote sense lines. The output voltage is also sensed and reported to the control circuit 1 (not shown). The output voltage will be reported via the output voltage sense line.

[0037] Figure 2 Exemplary signal waveforms of a power converter without the claimed overvoltage sensing protection (OSP) are shown. Figure 2 Shown are a driver enable signal 11, a PWM signal 12 for controlling the switching of one or more power stages, a true output voltage Vout 13 at the output 26 of the power converter, and a signal 14 indicating the sensed temperature. In the depicted example, switching of the power stages begins at time 16, and the output voltage begins to increase. As the output voltage sense erroneously reports a low output voltage (e.g., due to an open or short circuit associated with the sense line), the control circuit 1 continues to increase the output voltage, even though the output voltage exceeds the output overvoltage protection level OOVP 15. This behavior results in a dangerously high output voltage that could damage the load.

[0038] Figure 3 An exemplary functional diagram of a control circuit according to the present invention is shown. In particular, Figure 3 An exemplary embodiment of an OSP mechanism within a control circuit is shown. If the value of the current signal (peak Iout) exceeds the current fault threshold (Ipeak threshold at tosp) and if the value of the voltage signal (peak ΔVout) falls below the voltage fault threshold (ΔVout threshold at tosp), the control circuit determines a fault condition (here: open circuit). The current comparison can be performed by comparator 31, while the voltage comparison can be performed by comparator 32. Both comparisons can be performed at the same time tosp, and the outputs can be provided to an AND unit 33.

[0039] For example, the comparison can be based on the current value and the voltage value at time tosp. Alternatively, optional peak detector 34 and peak detector 35 can be used to determine the peak value / maximum value during a predetermined time interval of duration (tosp-t0), assuming that the predetermined time interval begins at time t0 (e.g., when the first switching pulse is transmitted to the power converter) and ends at time tosp. Peak detector 34 determines the maximum current value during the predetermined time interval, and peak detector 35 determines the maximum voltage value during the predetermined time interval. However, since both the voltage value and the current value are primarily increasing constantly, the maximum value is most likely to be found at the end of the predetermined time interval.

[0040] As another optional feature, the control circuit can use a summing unit 36 ​​to sum the values ​​indicating the individual phase currents of the power converter. In addition, to account for the offset voltage at the output of the power converter, an optional ΔVout determination unit 37 can be used. The offset voltage can be generated by various leakage currents at the output of the power converter. The leakage may cause a load, and they may be caused by components of the voltage regulator and from other rails in the system. When the voltage regulator is not regulating, such leakage may cause an offset voltage. As a controller, it is desirable to pre-set the target output to a ramp starting from the offset voltage rather than 0V to prevent stress on the leakage path.

[0041] By using an appropriate pre-bias Vout voltage, these offset voltages can be canceled. The Vout determination unit 37 can determine the difference between the measured / sensed output voltage Vout and the pre-bias voltage (eg, Vout - pre-bias Vout).

[0042] like Figure 3 As shown, an open circuit condition associated with the sensed voltage can be reported (remote sensing fault reporting), and the control circuit can react accordingly. For example, to avoid overvoltage at the output of the power converter, the power converter can be completely shut down.

[0043] The proposed output voltage sensing protection (OSP) offers the following advantages: it reliably protects the output load and can report remote sensing faults, which clearly indicate to the user where the problem lies. Furthermore, no additional analog changes are required, thus eliminating the need for controller re-spins. This feature can be implemented via a firmware patch, and customers only need to update the firmware for their field control circuits to implement it. Consequently, the present invention can increase the reliability and robustness of power converter control, particularly in the field of multiphase controller products.

[0044] Figure 4 Results of experiments with and without OSP controls are shown. Figure 4 In the left figure, OSP according to the present invention is enabled and a short circuit condition occurs across the remote voltage sense line. The duration of the predetermined time interval is tosp = 50µs. The current fault threshold (Ipeak threshold at tOSP) is 29A, and the voltage fault threshold (ΔVout threshold at tOSP) is set to 200mV. Therefore, since the (maximum) output current has reached 60A at the end of the predetermined time interval, the voltage regulator VR (also denoted as the power converter) is shut down.

[0045] exist Figure 4 In the right figure, the OSP according to the present invention is disabled. The control circuit is unable to discern this and mistakenly believes that the output voltage Vout is not gradually rising. In this case, the output current rises to 120A and is only stopped by the conventional overcurrent protection (OCP) mechanism that shuts down the voltage regulator. However, at the time of shutdown, the output voltage is already 400mV above the conventional startup level of 1.2V.

[0046] It should be noted that the description and drawings merely illustrate the principles of the proposed method and system. Those skilled in the art will be able to implement various arrangements that, although not explicitly described or shown herein, embody the principles of the present invention and are included within the spirit and scope of the present invention. In addition, all examples and embodiments outlined herein are, in principle, explicitly intended to be used for illustrative purposes only to help the reader understand the principles of the proposed method and system. In addition, all statements of principles, aspects, and embodiments of the present invention and their specific examples provided herein are intended to encompass their equivalents.

Claims

1. A control circuit configured to control a power converter, wherein the control circuit is configured to: receive a voltage signal indicating an output voltage at an output of the power converter; receive a current signal indicating an output current at the output of the power converter; and determine a fault condition associated with the voltage signal based on the current signal and based on the voltage signal. 2 . The control circuit of claim 1 , wherein the control circuit is configured to determine the fault condition if the value of the current signal exceeds a current fault threshold and if the value of the voltage signal is below a voltage fault threshold.

3. The control circuit according to claim 2, wherein the control circuit comprises: a current comparator configured to compare a value of the current signal with the current fault threshold; and a voltage comparator configured to compare a value of the voltage signal with the voltage fault threshold.

4. A control circuit according to any one of the preceding claims, wherein the control circuit is configured to determine a maximum value of the current signal within a predetermined time interval, and wherein the control circuit is configured to use this maximum value as the value of the current signal for determining the fault condition.

5. The control circuit of claim 4, wherein the control circuit is configured to determine a maximum value of the voltage signal within the predetermined time interval, and wherein the control circuit is configured to use the maximum value as the value of the voltage signal for determining the fault condition. 6 . The control circuit of claim 5 , wherein the control circuit is configured to determine the fault condition if a maximum value of the current signal exceeds the current fault threshold and if a maximum value of the voltage signal is below the voltage fault threshold.

7. The control circuit according to any one of claims 4 to 6, wherein the control circuit is configured to start the predetermined time interval when a first pulse width modulated (PWM) pulse is transmitted from the control circuit to a power stage of the power converter.

8. The control circuit of any one of the preceding claims, wherein the control circuit is configured to receive the voltage signal via an external output voltage sense line, and wherein the fault condition associated with the voltage signal is associated with an open circuit condition and a short circuit condition, the open circuit condition and the short circuit condition being associated with the external output voltage sense line.

9. A control circuit according to any preceding claim, wherein the control circuit is configured to shut down the power converter in response to determining the fault condition.

10. The control circuit of any preceding claim, wherein the control circuit is configured to transmit a PWM signal to the power converter to drive a switch of the power converter, and in response to determining the fault condition, stop increasing a duty cycle of the PWM signal.

11. The control circuit of any one of the preceding claims, wherein the power converter is a multiphase power converter, wherein the control circuit is configured to receive a plurality of phase current signals indicating currents of different phases of the multiphase power converter, and wherein the control circuit is configured to determine the current signal based on the phase current signals.

12. A method of controlling a power converter, the method comprising: receiving, by a control circuit, a voltage signal indicative of an output voltage at an output of the power converter, receiving, by the control circuit, a current signal indicative of an output current at the output of the power converter, and A fault condition associated with the voltage signal is determined by the control circuit based on the current signal and based on the voltage signal.

13. The method of claim 12, wherein the determining comprises: The fault condition is determined if the value of the current signal exceeds a current fault threshold and if the value of the voltage signal is below a voltage fault threshold.

14. A method according to claim 12 or 13, comprising determining a maximum value of the current signal within a predetermined time interval and using this maximum value as the value of the current signal for determining the fault condition.

15. A computer program comprising instructions which, when executed by one or more processors of a control circuit, cause the control circuit to perform the operations of any one of claims 12 to 14.

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