Power filter circuit, power arrangement, automatic test equipment and method for actively filtering a power supply voltage

Abstract

A power supply filter circuit (100) includes a transistor (120), a control capacitor (130), and a stabilizing capacitor (140). The load path of the transistor is coupled between the input terminal (110) and the output terminal (112) of the power supply filter circuit. The control capacitor is coupled between the control terminal of the transistor and a reference potential conductor (GND). The stabilizing capacitor is coupled between the source terminal of the transistor and the reference potential conductor. The power supply filter circuit is configured to regulate the voltage across the load path of the transistor or the voltage between the input terminal and the output terminal of the power supply filter circuit. A power supply arrangement structure, an automated test apparatus, and a method for actively filtering power supply voltages are also described.

Description

Technical Field

[0001] An embodiment of the present invention relates to a power filter circuit.

[0002] Another embodiment of the present invention relates to a power supply arrangement structure.

[0003] Another embodiment of the present invention relates to an automated testing device.

[0004] According to another embodiment of the present invention, there is a method for actively filtering a power supply voltage containing ripple using a power supply filter circuit.

[0005] According to some embodiments of the present invention, there is an active power supply filter for higher voltages. Background Technology

[0006] In many applications, a low-ripple supply voltage is desirable. However, energy-efficient switching power converters typically introduce significant amounts of ripple noise, partly due to the switching nature of the power conversion.

[0007] For example, in automated test equipment, precise voltage and current measurements are required. There are also specific requirements for the associated power supply. For instance, in some cases, the DC / DC converter needs sufficient filtering to provide a line voltage with very low noise to the measurement circuitry.

[0008] It has been recognized that filter circuits that achieve high current and high voltage via passive components often become too bulky because the density of devices (such as capacitors) decreases as the rated voltage increases.

[0009] Furthermore, it has been recognized that standard linear regulators are not suitable for filtering at higher voltages because their limited voltage accuracy and the voltage tolerance of DC / DC converters require a larger voltage headroom, resulting in higher power consumption within the filter circuitry.

[0010] Accordingly, there is a desire for a concept that offers an improvement over the provided voltage quality, power consumption, and implementation complexity. Summary of the Invention

[0011] An embodiment of the present invention provides a power filter circuit comprising a transistor (e.g., a power MOSFET or a bipolar transistor), a control capacitor, and a stabilizing capacitor. A load path (e.g., a drain-source path or a collector-emitter path) of the transistor is coupled between the input and output terminals of the power filter circuit. The control capacitor is coupled between a control terminal of the transistor (e.g., the gate terminal in the case of a field-effect transistor, or the base terminal in the case of a bipolar transistor) and a reference potential conductor (e.g., ground). For example, the load is coupled (to be coupled) between the output terminal of the power filter circuit and the reference potential conductor, or, for example, the load is coupled (to be coupled) between the source terminal of the transistor and the reference potential conductor. The stabilizing capacitor is coupled between the source terminal of the transistor (e.g., the source terminal in the case of a field-effect transistor, or the emitter terminal in the case of a bipolar transistor) and the reference potential conductor. The power filter circuit is configured to regulate the voltage across the load path of the transistor (e.g., the drain-source voltage in the case of a field-effect transistor, or the collector-emitter voltage in the case of a bipolar transistor) or to regulate the voltage between the input and output terminals of the power filter circuit.

[0012] This embodiment is based on the finding that a good trade-off can be achieved between output voltage quality, power consumption, and implementation complexity through this circuit. Specifically, by placing the transistor's load path between the input and output of the power filter circuit, the effects of voltage fluctuations (e.g., noise) applied to the input of the power filter circuit can be compensated, because the current flowing through the transistor's load path is generally relatively insensitive to voltage fluctuations across the load path (e.g., collector-emitter or drain-source path) (at least when the transistor is at a "reasonable" operating point). However, it has been recognized that by adjusting the voltage across the transistor's load path (typically implying a certain delay and low-pass characteristic), a well-defined voltage can be obtained at the output of the power filter circuit (at least provided the average voltage at the input of the power circuit is well-defined, e.g., explicitly regulated).

[0013] However, it has also been recognized that such power filter circuits can be implemented with a relatively small voltage drop across the load path of the transistor (which means relatively low power consumption).

[0014] Furthermore, it should be noted that both control capacitors and stabilizing capacitors contribute to improving the quality of the output voltage present at the output terminal of the power supply filter circuit. For example, a control capacitor coupled between the control terminal of a transistor and a reference potential conductor (e.g., ground) keeps the potential at the control terminal of the transistor reasonably stable (at least on a short or medium timescale).

[0015] Since in many cases the output voltage at the output terminal of the power filter circuit can be closely related to the voltage at the control terminal of the transistor, stabilizing the voltage at the control terminal of the transistor by controlling the capacitor helps to stabilize the output voltage at the output terminal of the power filter circuit.

[0016] The regulation of the voltage across the load path of the transistor (or the voltage between the input and output of the power filter circuit) can have a limited bandwidth (or a certain regulation time constant), which helps to at least partially suppress noise that may be present in the voltage supplied to the input of the power filter circuit.

[0017] In summary, the power filter circuit allows for the provision of high-quality output voltage, where noise and other distortions that may be present in the input voltage supplied to the power filter circuit can be reduced, attenuated, or even significantly suppressed. Furthermore, this configuration enables a low voltage drop between the input and output of the power filter circuit, where good output voltage accuracy and low power consumption can be achieved by adjusting the voltage across the load path of the transistors (or by adjusting the voltage between the input and output of the power filter circuit, for example, in the case of multiple transistors in series coupling or additional components coupled in series between the transistors and the input and output).

[0018] In a preferred embodiment, the capacitance of the control capacitor is greater than or equal to 10 times the internal capacitance of the transistor between the control terminal (e.g., the gate terminal in the case of a field-effect transistor, or the base terminal in the case of a bipolar transistor) and the source terminal (e.g., the source terminal in the case of a field-effect transistor, or the emitter terminal in the case of a bipolar transistor), for example, greater than or equal to 10 times the gate-source capacitance of the transistor. Alternatively, the capacitance of the control capacitor is greater than or equal to 20 times the internal capacitance of the transistor between the control terminal (e.g., the gate terminal in the case of a field-effect transistor, or the base terminal in the case of a bipolar transistor) and the source terminal (e.g., the source terminal in the case of a field-effect transistor, or the emitter terminal in the case of a bipolar transistor), for example, greater than or equal to 20 times the gate-source capacitance of the transistor. Alternatively, the capacitance of the control capacitor is greater than or equal to 50 times the internal capacitance of the transistor between the control terminal (e.g., the gate terminal in the case of a field-effect transistor, or the base terminal in the case of a bipolar transistor) and the source terminal (e.g., the source terminal in the case of a field-effect transistor, or the emitter terminal in the case of a bipolar transistor), for example, greater than or equal to 50 times the gate-source capacitance of the transistor. Alternatively, the capacitance of the control capacitor is greater than or equal to 100 times the internal capacitance of the transistor between the control terminal (e.g., the gate terminal in the case of a field-effect transistor, or the base terminal in the case of a bipolar transistor) and the source terminal (e.g., the source terminal in the case of a field-effect transistor, or the emitter terminal in the case of a bipolar transistor), for example, greater than or equal to 100 times the gate-source capacitance of the transistor.

[0019] It has been recognized that using a control capacitor of this size can achieve particularly good quality of output voltage at the output of a power filter circuit. In particular, it has been recognized that if the control capacitor is large enough, for example significantly larger than the internal capacitance of the transistor between the control terminal and the source terminal of the transistor, the control capacitor is effective in suppressing distortion on the output voltage of the power filter circuit, where the source terminal of the transistor is typically, but not necessarily, coupled to the output of the power filter circuit.

[0020] In a preferred embodiment, the power filter circuit includes a resistor coupled between the output of a regulator (e.g., the output of an operational amplifier that implements the regulator) and a control terminal of a transistor. The regulator is used to regulate the voltage across the load path of the transistor (e.g., the drain-source voltage in the case of a field-effect transistor, or the collector-emitter voltage in the case of a bipolar transistor) or to regulate the voltage between the input and output of the power filter circuit. The resistor, coupled between the regulator's output and the transistor's control terminal, is configured, together with a control capacitor, to form a low-pass filter (e.g., a low-pass filter having a cutoff frequency less than or equal to 10 kHz).

[0021] Using such a resistor, coupled between the regulator's output and the transistor's control terminal, helps limit the bandwidth of the regulation loop, which in turn allows for the reduction or suppression of noise at frequencies greater than the regulation loop bandwidth. Furthermore, using a resistor between the regulator's output and the transistor's control terminal also limits the current and thus prevents damage to the transistor and / or the regulator.

[0022] In a preferred embodiment, the power supply filter circuit (e.g., a regulator of the power supply filter circuit) is configured to regulate the voltage across the load path of the transistor or the voltage between the input and output terminals of the power supply filter circuit, so that the transistor operates in the saturation region (the saturation region of its output characteristic field).

[0023] By adjusting the voltage across the load path of the transistor, or the voltage between the input and output of the power filter circuit, to make the transistor operate in the saturation region, the current flowing through the transistor's load path becomes relatively insensitive to voltage changes across the load path. Correspondingly, noise or other distortions at the input voltage of the power filter circuit can be decoupled from its output. In other words, by adjusting the voltage across the load path of the transistor to operate in the saturation region, a high output impedance (i.e., essentially operating as a current source) can be ensured. Therefore, the high output impedance of the transistor obtained by operating it in the saturation region has the effect that noise and other distortions at the input voltage of the power filter circuit are not transmitted to the output of the power filter circuit (or are transmitted only in a significantly attenuated form).

[0024] Furthermore, by stabilizing the potential at the control terminal of the transistor using a control capacitor, the distortion of the output voltage of the power filter circuit can be further reduced. In other words, by adjusting the voltage across the load path of the transistor (or the voltage between the input and output terminals of the power filter circuit) to operate the transistor in the saturation region, it is ensured that the voltage across the load path of the transistor does not become too low. This is advantageous because a very small voltage across the load path of the transistor will significantly reduce the suppression of noise and other distortions on the output voltage of the power filter circuit. Accordingly, good quality of the output voltage of the power filter circuit can be ensured.

[0025] In a preferred embodiment, the power filter circuit (e.g., a regulator of the power filter circuit) is configured to regulate the voltage across the load path of the transistor to a target value (e.g., a predetermined or fixed target value) that is less than or equal to 1V.

[0026] Alternatively, the power supply filter circuit (e.g., the regulator of the power supply filter circuit) is configured to regulate the voltage across the load path of the transistor to a target value (e.g., a predetermined or fixed target value) in the range of 0.3V to 0.8V.

[0027] Alternatively, the power supply filter circuit (e.g., the regulator of the power supply filter circuit) is configured to regulate the voltage across the load path of the transistor to a target value (e.g., a predetermined or fixed target value) in the range of 0.4V to 0.6V.

[0028] Alternatively, the power filter circuit (e.g., the regulator of the power filter circuit) is configured to regulate the voltage difference between the input and output of the power filter circuit to a target value (e.g., a predetermined or fixed target value) that is less than or equal to 1V.

[0029] Alternatively, the power filter circuit (e.g., the regulator of the power filter circuit) is configured to regulate the voltage difference between the input and output of the power filter circuit to a target value (e.g., a predetermined or fixed target value) in the range of 0.3V to 0.8V.

[0030] Alternatively, the power filter circuit (e.g., the regulator of the power filter circuit) is configured to regulate the voltage difference between the input and output of the power filter circuit to a target value (e.g., a predetermined or fixed target value) in the range of 0.4V to 0.6V.

[0031] Low power consumption can be achieved by adjusting the voltage across the transistor's load path or the voltage difference between the input and output of the power filter circuit. Furthermore, a particularly good trade-off can be achieved between output voltage quality and power consumption by ensuring the transistor operates in the saturation region while maintaining a relatively low voltage across its load path. For example, by adjusting the voltage across the transistor's load path, the transistor can always operate in the "lower" part of the saturation region, where power consumption is relatively low, but the transistor's output impedance remains sufficiently high to achieve good distortion suppression.

[0032] Furthermore, it should be noted that the same effect can be achieved by adjusting the voltage difference between the input and output terminals of the power filter circuit, which may be reasonable if there is another circuit component in series coupled to the load path of the transistor between the input and output terminals of the power filter circuit.

[0033] In other words, it is generally advantageous to adjust the voltage across the load path of a transistor or the voltage difference between the input and output of a power supply filter circuit in such a way that the transistor operates reliably in the saturation region, but with a reasonably small voltage across its load path.

[0034] However, it has been recognized that the values ​​mentioned above provide good results for many typical types of transistors.

[0035] In a preferred embodiment, the power filter circuit is configured such that the bandwidth of the control loop used to regulate the voltage across the load path of the transistor or to regulate the voltage between the input and output terminals of the power filter circuit is limited to a value not exceeding 10 kHz, or 5 kHz, or 1000 Hz, or 500 Hz, or 200 Hz, or 100 Hz, or 50 Hz.

[0036] By adjusting the power supply filter circuit to limit the bandwidth of the control loop to a certain frequency, it is possible to achieve the following: distortion on the input voltage of the power supply filter circuit with a frequency higher than the bandwidth of the control loop will be attenuated, while the output voltage follows changes in the input voltage with a frequency lower (or significantly lower) than the bandwidth of the control loop. Accordingly, the output voltage can follow the expected (relatively slow) changes in the input voltage, while unexpected (relatively rapid) changes in the input voltage (e.g., due to noise or other distortions) do not significantly affect the output voltage.

[0037] Furthermore, it has been found that, depending on the application, the aforementioned values ​​for limiting the bandwidth of the control loop provide good power filter circuit characteristics, such as in terms of noise and distortion attenuation.

[0038] In a preferred embodiment, the control loop for adjusting the voltage across the load path of the transistor or for adjusting the voltage between the input and output terminals of the power filter circuit (e.g., the control loop described above for adjusting the voltage across the load path of the transistor or for adjusting the voltage between the input and output terminals of the power filter circuit) includes (e.g., in the feedback path between the transistor's terminal and the regulator's input terminal) a low-pass filter, wherein the low-pass filter has a cutoff frequency less than or equal to 10 kHz, or wherein the low-pass filter has a cutoff frequency less than or equal to 5 kHz, or wherein the low-pass filter has a cutoff frequency less than or equal to 1000 Hz, or wherein the low-pass filter has a cutoff frequency less than or equal to 500 Hz, or wherein the low-pass filter has a cutoff frequency less than or equal to 200 Hz, or wherein the low-pass filter has a cutoff frequency less than or equal to 100 Hz. The low-pass filter may, for example, include a low-pass filter resistor and a low-pass filter capacitor. A low-pass filter may include, for example, a bypass arrangement, such as diodes, which are configured to selectively bypass the low-pass filter resistor when the voltage across the low-pass resistor exceeds a threshold or when the magnitude (absolute value) of the voltage across the low-pass resistor exceeds a threshold.

[0039] By introducing a low-pass filter into the control loop, the bandwidth of the control loop can be adjusted in a well-controlled manner. This allows for defining at what frequency the output voltage of the power filter circuit transitions from essentially following changes in the input voltage to a state where changes in the input voltage (e.g., due to noise or other distortions) are attenuated in the output voltage. Accordingly, it is possible to achieve a predetermined and well-controlled relationship between the output voltage and the input voltage of the power filter circuit under static or quasi-static conditions (i.e., for a constant input voltage or for slowly changing input voltages), while for faster changes in the input voltage (e.g., noise-like changes), the output voltage does not (or only attenuates) follow these changes. Therefore, well-defined and well-regulated behavior of the power filter circuit can be achieved.

[0040] In a preferred embodiment, the power supply filter circuit is configured (e.g., using a floating reference voltage source) to provide a floating reference potential that is offset by a predetermined value relative to the potential at the output of the power supply filter circuit, and

[0041] The power filter circuit is configured to perform regulation so that the potential at the transistor's terminal (e.g., at the drain terminal) or the potential at the input of the power filter circuit is aligned with the floating reference potential (e.g., so that the potential at the transistor's terminal (e.g., at the drain terminal) or the potential at the input of the power circuit is at least approximately equal to the floating reference potential).

[0042] Alternatively, the power supply filter circuit can be configured (e.g., using a floating reference voltage source) to provide a floating reference potential offset by a predetermined value relative to the potential at the source terminal of the transistor, and the power supply filter circuit can be configured to perform adjustment so that the potential at the terminal of the transistor (e.g., at the drain terminal in the case of a field-effect transistor, or at the collector terminal in the case of a bipolar transistor) or at the input of the power supply filter circuit is aligned with the floating reference potential (e.g., so that the potential at the terminal of the transistor or at the input of the power supply filter circuit is at least approximately equal to the floating reference potential).

[0043] Alternatively, the power supply filter circuit can be configured (e.g., using a floating reference voltage source) to provide a floating reference potential that is offset by a predetermined value relative to the potential at the input of the power supply filter circuit, and the power supply filter circuit can be configured to perform adjustment so that the potential at the source terminal of the transistor or the potential at the output of the power supply filter circuit is aligned with the floating reference potential (e.g., making the potential at the source terminal of the transistor or the potential at the output of the power supply circuit at least approximately equal to the floating reference potential).

[0044] Alternatively, the power supply filter circuit can be configured (e.g., using a floating reference voltage source) to provide a floating reference potential offset by a predetermined value relative to the potential at the transistor's sink terminal, and the power supply filter circuit can be configured to perform adjustment so that the potential at the transistor's source terminal (e.g., at the source terminal in the case of a field-effect transistor, or at the emitter terminal in the case of a bipolar transistor) or at the output of the power supply filter circuit is aligned with the floating reference potential (e.g., so that the potential at the transistor's source terminal or at the output of the power supply filter circuit is at least approximately equal to the floating reference potential).

[0045] It has been found that using such an arrangement, the voltage difference across the load path of a transistor or the voltage difference between the input and output of a power supply filter circuit can be regulated efficiently. A floating reference potential has been found advantageous in this application because the voltage at the input and output of the power supply filter circuit may vary during circuit operation. Furthermore, it has been recognized that aligning the two potentials (one of which is the floating reference potential) can be efficiently achieved using a regulating circuit, which can be, for example, a differential amplifier (e.g., an operational amplifier).

[0046] Accordingly, it has been recognized that the above implementation provides good accuracy and can be achieved with a moderate amount of work.

[0047] In a preferred embodiment, the power filter circuit includes a bypass path (e.g., composed of CR3 and CR4) connected in parallel with the load path of the transistor, wherein the bypass path is configured to conduct when the voltage across the load path of the transistor exceeds a predetermined threshold voltage (e.g., the threshold voltage of a diode, or the combined threshold voltage of a series circuit of multiple diodes), and otherwise not conduct.

[0048] The bypass path can be configured, for example, to be conductive in a current direction parallel to the current direction through the transistor's load path during the operation of the power supply filter circuit. The bypass path can, for example, include a diode coupled in parallel to the transistor's load path, or it can, for example, include a series connection of multiple diodes coupled in parallel to the transistor's load path.

[0049] The bypass path can be configured, for example, to not conduct when the voltage across the load path of the transistor is less than 1.5 times the regulated target voltage, and the bypass path can be configured, for example, to conduct when the voltage across the load path of the transistor is greater than 6 times the regulated target voltage.

[0050] Alternatively or additionally, the bypass path can be configured to transition from a non-conducting state to a conducting state within a voltage range of 0.6V to 3V or within a voltage range of 1V to 2V.

[0051] It has been recognized that such a bypass path, connected in parallel with the transistor's load path, allows for rapid circuit startup and also allows for rapid changes in the output voltage, which may be desirable, for example, in test applications when the output voltage of a power filter circuit must be changed quickly. Furthermore, it has been recognized that the bypass path helps reduce transistor power dissipation and also protects the transistor to some extent from overvoltages across the load path. Moreover, it has been recognized that such a bypass path is reasonable due to the specific function of the circuit (i.e., designed to regulate the voltage across the transistor's load path to a desired and relatively small value (e.g., to operate the transistor in the saturation region)). Since input voltage fluctuations are relatively small in typical applications, "normal" fluctuations in the input voltage to be attenuated will not be sufficient to cause significant current flow through the bypass path, so that the bypass path does not significantly reduce the effectiveness of the power filter circuit in suppressing input voltage distortion at the output of the power filter circuit. In other words, assuming the bypass path is reasonably sized, for example, such that current flows through the bypass path only when the voltage across the bypass path or the voltage between the input and output terminals of the power filter circuit is greater than the regulation target (i.e., the voltage across the load path of the transistor or the voltage between the input and output terminals of the power filter circuit is regulated to the target value), and such that no current flows through the bypass path when the input voltage fluctuates normally (e.g., due to noise or other distortion), then the bypass path does not degrade the normal operation of the power filter circuit, but is very useful when rapid changes in output voltage are required (e.g., rapid boosts).

[0052] In summary, it has been found that using a bypass path significantly improves some characteristics of the circuit without having a substantial negative impact on suppressing noise and other distortions on the output voltage of the power supply filter circuit.

[0053] In a preferred embodiment, the power supply filter circuit includes a low-pass resistor (e.g., R2), a low-pass capacitor (e.g., C2), an operational amplifier (e.g., U1), an integrating capacitor (e.g., C3), and an output resistor (e.g., R8). The low-pass resistor is coupled between a terminal (e.g., drain terminal) of a transistor (e.g., Q1) and a first terminal (e.g., C2) of the low-pass capacitor. A second terminal of the low-pass capacitor (e.g., C2) is coupled to a reference potential conductor (e.g., ground). A first input terminal (e.g., a non-inverting input terminal; e.g., "+") of the operational amplifier is coupled to the first terminal of the low-pass capacitor (e.g., directly or via one or more resistors, e.g., via R7). The second terminal of the operational amplifier (e.g., the inverting input terminal; as "-") is coupled to the source terminal of the transistor via one or more resistors (e.g., via R5 and R6, or only via resistor R6), wherein, for example, a floating reference voltage source, including R3, R4, R5, and U2, is provided between the source terminal of the transistor and the voltage-to-current conversion resistor R6, or for example, no other circuitry exists between the source terminal of the transistor and the voltage-to-current conversion resistor R6. The second terminal of the operational amplifier is coupled to the output terminal of the operational amplifier via a capacitor (e.g., C3), which serves as an integrating capacitor, for example. The output terminal of the operational amplifier is coupled to the first terminal of a control capacitor (e.g., C1) via an output resistor (e.g., R8). The first terminal of the control capacitor (e.g., C1) is coupled to the control terminal (e.g., the gate terminal) of the transistor (e.g., Q1), either directly coupled or coupled through another resistor (e.g., R9). The second terminal of the control capacitor is coupled to a reference potential conductor (e.g., GND). For example, a series connection of two diodes (e.g., CR3, CR4) is coupled in parallel to the load path of the transistor, for example, in a manner where the anode is on the positive power supply side (positive relative to the reference potential conductor) and coupled to the input of the power supply filter circuit, or the cathode is on the negative power supply side (negative relative to the reference potential conductor) and coupled to the input of the power supply filter circuit. For example, a diode (e.g., CR2) is coupled between the first terminal of the control capacitor and a potential that is a predetermined increase in potential relative to the terminal of the transistor's terminal (e.g., where the anode is coupled to the first terminal of the control capacitor). For example, a diode (e.g., CR2) is coupled between the source terminal of the transistor and the first terminal of the control capacitor (e.g., where the cathode is coupled to the first terminal of the control capacitor). For example, an anti-parallel circuit of two diodes is coupled in parallel with a low-pass resistor. For example, a diode is coupled between the first terminal of the control capacitor and the positive power supply voltage terminal of the operational amplifier (e.g., the anode is coupled to the first terminal of the control capacitor). For example, a diode is coupled between the first terminal of the control capacitor and the negative power supply voltage terminal of the operational amplifier (e.g., the cathode is coupled to the first terminal of the control capacitor). For example, the negative power supply voltage terminal of the operational amplifier is coupled to the source terminal of the transistor.For example, the positive power supply voltage terminal of an operational amplifier is coupled to a potential that, in a static state, is offset by a predetermined value relative to the potential at the drain terminal of a transistor (e.g., in the case of an active power filter circuit for a positive voltage). For example, the negative power supply voltage terminal of an operational amplifier is coupled to a potential that, in a static state, is offset by a predetermined value relative to the potential at the drain terminal of a transistor (and, for example, follows the potential at the drain terminal of the transistor with a predetermined time constant). For example, the positive power supply voltage terminal of an operational amplifier is coupled to a potential that, in a static state, is offset by a predetermined value relative to the potential at the drain terminal of a transistor (and, for example, follows the potential at the drain terminal of the transistor with a predetermined time constant) (e.g., in the case of an active power filter circuit for a negative voltage).

[0054] It has been found that such circuits can achieve the desired results, namely, good attenuation (or suppression) of noise and distortion on the input voltage of the power supply circuit, while keeping the implementation workload reasonably small.

[0055] An embodiment of the present invention provides a power supply arrangement structure comprising a switching power converter (e.g., a DC / DC converter) and a power filter circuit as described above. The output of the switching power converter is coupled to the input of the power filter circuit.

[0056] It has been recognized that power supply filter circuits are well-suited for reducing noise and distortion caused by the operation of switching power converters. Accordingly, high power efficiency can be achieved by using a switching power converter to provide the input voltage to the power supply filter circuit, and the power supply filter circuit is well-suited for reducing noise and distortion caused by the switching power converter. For example, the power supply filter circuit can be designed such that its output voltage can accurately follow slower changes in the input voltage of the power supply filter circuit (i.e., the output voltage of the switching power converter), while relatively fast (undesirable) changes in the input voltage caused by noise and / or other distortions generated by the switching power converter can be efficiently attenuated (or suppressed) (e.g., achieved with low power consumption and smaller circuitry).

[0057] For example, the regulation of a power supply filter circuit can be designed in such a way that the regulation does not follow relatively rapid, noise-like changes in the input voltage, but rather relatively slow changes in the input voltage that may be caused by intentional adjustment or regulation of the input voltage. Therefore, relatively rapid (e.g., noise-like) changes in the input voltage of the power supply filter circuit result in a voltage change across the transistor's load path, but not a significant change in the output voltage of the power supply filter circuit. In contrast, slow changes in the input voltage of the power supply filter circuit, due to regulation, do not result in a significant change in the voltage across the transistor's load path, and thus a corresponding change in the voltage at the output of the power supply filter circuit. This functionality can be achieved by appropriately selecting the regulation time constant (or equivalently, by appropriately selecting the control loop bandwidth used to regulate the voltage across the transistor's load path or to regulate the voltage between the input and output of the power supply filter circuit).

[0058] In summary, by appropriately adjusting the characteristics of the power filter circuit to match the characteristics of the switching power converter (e.g., the noise and distortion characteristics generated by the switching power converter), high-quality voltage (low noise and distortion) can be achieved at the output of the power filter circuit.

[0059] In a preferred embodiment of the power supply arrangement, the adjustment time constant of the adjustment loop used to adjust the voltage across the load path of the transistor (e.g., the drain-source voltage of the transistor in the case of a field-effect transistor, or the collector-emitter voltage in the case of a bipolar transistor) or to adjust the voltage between the input and output of the power supply filter circuit is at least 2, or at least 5, or at least 10, or at least 20, or at least 50, or at least 100, or at least 200, or at least 500, or at least 1000, or at least 500, or at least 1000, or at least 1000, or at least 1000, or at least 1000, or at least 1000, or at least 1000, or at least 1000, or at least 1000, of the period duration of the power supply converter.

[0060] It has been recognized that this selection of the adjustment time constant for the power supply filter circuit can effectively attenuate noise or other distortions in the input voltage caused by the operation of the switching power converter. It has been recognized that, in many cases, distortion has a frequency equal to or a multiple of the switching frequency of the switching power converter. Accordingly, by using the above-described selection of the adjustment time constant, it is possible to achieve that the adjustment of the power supply filter circuit is intentionally too slow to follow the noise or distortion in the input voltage originating from the switching operation of the switching power supply. Consequently, the output voltage does not follow this noise and distortion caused by the switching operation of the switching power supply, which in many cases may be dominant.

[0061] In a preferred embodiment of the power supply arrangement, the regulation of the voltage across the load path of the transistor (e.g., drain-source voltage in the case of a field-effect transistor, or collector-emitter voltage in the case of a bipolar transistor) or the voltage between the input and output terminals of the power filter circuit is configured such that the regulation does not regulate the voltage change across the load path of the transistor caused by the ripple voltage of the switching power converter, or the voltage change between the input and output terminals of the power filter circuit caused by the ripple voltage of the switching power converter, by more than 50% (e.g., such that the voltage across the load path of the transistor follows at least 50% of the ripple voltage), or the voltage change caused by the switching power converter, by more than 50% of the ripple voltage. The voltage change across the transistor's load path caused by the ripple voltage of the power converter or the voltage change between the input and output terminals of the power filter circuit caused by the ripple voltage of the switching power converter shall be regulated by more than 20% (e.g., such that the voltage across the transistor's load path follows at least 80% of the ripple voltage), or the voltage change across the transistor's load path caused by the ripple voltage of the switching power converter or the voltage change between the input and output terminals of the power filter circuit caused by the ripple voltage of the switching power converter shall not be regulated by more than 10% (e.g., such that the voltage across the transistor's load path follows at least 90% of the ripple voltage).

[0062] By determining the dimensions of the power supply filter circuit in such a way that the adjustment does not significantly reduce the voltage variations across the transistor's load path or between the input and output terminals of the power supply filter circuit caused by the ripple voltage of the switching power converter, it is possible to ensure that the ripple voltage of the switching power supply does not significantly affect the output voltage of the power supply filter circuit. Consequently, good quality of the output voltage of the power supply filter circuit can be achieved.

[0063] In other words, the ripple voltage of a switching power converter is largely "absorbed" by the voltage variation across the transistor's load path. As mentioned above, since the transistor operates in the saturation region, this voltage variation across the transistor's load path typically does not result in a significant change in the current flowing through the transistor's load path. Therefore, by combining a power-efficient switching power supply with a power filter circuit, and through proper design of the power filter circuit's regulation, a high-quality output voltage can be obtained using a power-efficient switching power supply.

[0064] An automated test apparatus is created according to embodiments of the present invention, wherein the automated test apparatus includes a power supply arrangement structure as described above (or generally, a power supply device as described herein). The automated test apparatus is configured to programmably (e.g., under the control of a test program) change the voltage supplied by a switching power converter, thereby setting the voltage at the output of a power filter circuit to a desired value. The power filter circuit includes a fast-changing mechanism configured to selectively bypass the load path of a transistor (e.g., using diodes CR3 and CR4), and / or bypass a low-pass filter (e.g., using diode CR1) in a regulating loop used to regulate the voltage across the load path of the transistor or to regulate the voltage between the input and output of the power filter circuit.

[0065] Power supply filter circuits have been found to be highly suitable for automated test equipment because they can provide high-quality (e.g., low noise and / or low ripple) output voltages through a compact and power-efficient circuit. As mentioned above, a power-efficient switching power converter can be used to provide the input voltage to the power supply filter circuit, which can provide a good quality output voltage without requiring space-consuming passive filter components such as large capacitors and / or inductors. However, power supply filter circuits still allow for relatively rapid changes in output voltage, which may be desirable in some cases in automated test equipment used to test the characteristics of a device under test under varying supply voltage conditions. For example, a fast-charging mechanism of the power supply filter circuit can support such functionality. Therefore, the beneficial characteristics of power supply filter circuits have been recognized as making them well-suited for use in automated test equipment, where, for example, the use of a fast-changing mechanism may even enable the power supply filter circuit to have good timing characteristics, thereby allowing for rapid test cycles.

[0066] In conclusion, it has been recognized that power supply filter circuits are a good choice for applications in automated test equipment.

[0067] An embodiment of the present invention provides a method for actively filtering a power supply voltage including (e.g., periodic) ripple using a power supply filter circuit, wherein the power supply filter circuit includes a transistor (e.g., a power MOSFET or a bipolar transistor), a control capacitor, and a stabilizing capacitor, wherein the load path (e.g., a drain-source path or a collector-emitter path) of the transistor is coupled between the input and output of the power supply filter circuit, wherein the control capacitor is coupled between the control terminal of the transistor (e.g., the gate terminal in the case of a field-effect transistor or the base terminal in the case of a bipolar transistor) and a reference potential conductor (e.g., ground), wherein the load is coupled (or to be coupled) between the output of the power supply filter circuit and the reference potential conductor, or wherein the load is coupled (or to be coupled) between the source terminal of the transistor and the reference potential conductor, and wherein the stabilizing capacitor is coupled between the source terminal of the transistor (e.g., the source terminal in the case of a field-effect transistor or the emitter terminal in the case of a bipolar transistor) and the reference potential conductor. The method includes stabilizing the potential difference between the control terminal of a transistor and a reference potential conductor using a control capacitor to suppress (at least partially) the generation of potential fluctuations at the control terminal of the transistor caused by ripple on the power supply voltage applied to the input of a power supply filter circuit. The method includes adjusting the voltage across the load path of the transistor (e.g., drain-source voltage in the case of a field-effect transistor, or collector-emitter voltage in the case of a bipolar transistor) or adjusting the voltage between the input and output of the power supply filter circuit by an adjustment time constant that is at least 10, at least 20, at least 50, or at least 100 times the duration of the period of the ripple of the power supply voltage applied to the input of the power supply filter circuit. An output voltage is obtained at the output of the power supply filter circuit.

[0068] This method is based on the same considerations as the power filter circuit described above. Furthermore, this method may optionally be supplemented by any features, functions, and details disclosed herein, also applicable to the device. Attached Figure Description

[0069] Embodiments of the invention will then be described with reference to the accompanying drawings, in which: Figure 1 A block diagram of a power filter circuit according to an embodiment of the present invention is shown; Figure 2 A block diagram of a power supply arrangement structure according to an embodiment of the present invention is shown; Figure 3 A block diagram of an automated testing apparatus according to an embodiment of the present invention is shown; Figure 4 A block diagram of a power filter circuit according to an embodiment of the present invention is shown; Figure 5a shows a graphical representation of the characteristic curves of a power MOSFET, which can be used in embodiments according to the present invention; Figure 5b shows a graphical representation of the LTSpice simulation model used to plot the characteristic curves; Figure 6a shows a graphical representation of the signal at the input of a power supply filter circuit (e.g., the input of an active filter according to an embodiment of the present invention); Figure 6b shows a graphical representation of the signal at the output of the power supply filter circuit (e.g., the output of an active filter according to an embodiment of the present invention); Figure 7 A block diagram of an active power supply filter for positive voltage according to an embodiment of the present invention is shown; Figure 8 A block diagram of an active power supply filter for negative voltage according to an embodiment of the present invention is shown; Figure 9 A schematic diagram of a power supply filter for positive voltage according to an embodiment of the present invention is shown; and Figure 10 A schematic diagram of an active power supply filter for negative voltage according to an embodiment of the present invention is shown. Detailed Implementation

[0070] 1. According to Figure 1 Power filter circuit

[0071] Figure 1 A block diagram of a power filter circuit 100 according to an embodiment of the present invention is shown. The power filter circuit 100 is configured to receive an input voltage at input terminal 110 and provide an output voltage at output terminal 112. Furthermore, it should be noted that the power filter circuit may be coupled, for example, to a reference potential conductor (e.g., to a ground wire), wherein the input voltage at input terminal 110 and the output voltage at output terminal 112 may be referenced to the potential of the reference potential conductor.

[0072] The power filter circuit 100 includes a transistor 120, which can be, for example, a MOSFET transistor, a bipolar transistor, or any other type of transistor. In many cases, a power MOSFET transistor is a good choice. The power filter circuit 100 also includes a control capacitor 130 and a stabilizing capacitor 140. The load path of the transistor (e.g., the drain-source path in the case of a field-effect transistor, or the collector-emitter path in the case of a bipolar transistor) is coupled between the input terminal 110 and the output terminal 112 of the power filter circuit 100. The control capacitor 130 is coupled between the control terminal of the transistor (e.g., the gate terminal in the case of a field-effect transistor, or the base terminal in the case of a bipolar transistor) and a reference potential conductor 150. For example, the reference potential conductor can be a ground wire. For example, the load (in Figure 1 (Not shown) Coupled between the output terminal 112 of the power filter circuit 110 and the reference potential conductor 150. Alternatively, for example, the load (in Figure 1 (Not shown) Coupled between (or to be coupled to) the source terminal of the transistor and the reference potential conductor 150. The stabilizing capacitor 140 is coupled between the source terminal of the transistor (e.g., the source terminal in the case of a field-effect transistor, or the emitter terminal in the case of a bipolar transistor) and the reference potential conductor 150.

[0073] The power filter circuit is configured to regulate the voltage across the load path of the transistor (e.g., the drain-source voltage in the case of a field-effect transistor, or the collector-emitter voltage in the case of a bipolar transistor), or to regulate the voltage between the input terminal 110 and the output terminal 112 of the power filter circuit. For example, regulation of the voltage across the load path of the transistor or the voltage between the input and output terminals of the power filter circuit can be achieved by adjustment 160, which can be coupled, for example, between the input terminal 110 and the output terminal 112 of the power filter circuit, or between the load path terminals of the transistor 120, and wherein adjustment 160 can, for example, provide a control signal (e.g., a control voltage) applied to the control terminals of the transistor 120.

[0074] Regarding this issue, it should be noted that in many cases, the voltage at the input terminal 110 of the power filter circuit can be the same as the voltage at the first load path terminal of the transistor 120, and the voltage at the output terminal 112 of the power filter circuit can be the same as the voltage at the second load path terminal of the transistor 120. However, in other embodiments, multiple transistors can be coupled in series, or some components (e.g., shunt resistors for current measurement) can be coupled between the input terminal 110 of the power filter circuit and the first load path terminal of the transistor 120, and / or coupled between the second load path terminal of the transistor and the output terminal 112 of the power filter circuit 110.

[0075] Regarding the function of the power filter circuit 100, it should be noted that regulating the voltage across the load path of the transistor or regulating the voltage between the input terminal 110 and the output terminal 112 of the power filter circuit has the following effect: the voltage at the output terminal 112 of the power filter circuit follows at least a sufficiently slow change in the voltage at the input terminal 110 of the power filter circuit. However, the load path of the transistor 120, connected between the input terminal 110 and the output terminal 112 of the power filter circuit, attenuates (or even suppresses) noise and distortion on the input voltage (i.e., the voltage at the input terminal 110 of the power filter circuit 100). Furthermore, the fact that regulation typically includes a regulation time constant has the following advantageous effect: the voltage at the output terminal 112 of the power filter circuit typically does not follow the rapid, noise-like fluctuations in the voltage at the input terminal 110 of the power filter circuit, resulting in a significant reduction in noise and distortion brought about by the power filter circuit.

[0076] Furthermore, it should be noted that the power filter circuit 100 can be designed in a very energy-efficient manner, meaning that the power consumption of the power filter circuit can be kept reasonably low. It has also been found that the component (physical) size of the power filter circuit can remain reasonably small without significantly affecting the quality of the output voltage at the output terminal 110 of the power filter circuit. In other words, the power filter circuit 100 typically does not require excessively large passive components, such as very large capacitors or inductors. However, it has been found that both the control capacitor 130 and the stabilizing capacitor 140 make a significant contribution to the quality of the output voltage at the output terminal of the power filter circuit, with the control capacitor 130 helping to reduce voltage fluctuations at the control terminal of the transistor 120, which in turn results in particularly good voltage quality at the output terminal 112 of the power filter circuit.

[0077] Therefore, it becomes apparent that the power filter circuit 100 offers a particularly good trade-off between the quality of the output voltage at output voltage 112, power consumption, implementation workload, and space consumption.

[0078] The following will describe some optional aspects that are preferably (but not necessarily) considered in the implementation of the power filter circuit.

[0079] For example, preferably, the capacitance of the control capacitor 130 is chosen to be sufficiently large. It has been found advantageous if the capacitance of the control capacitor is greater than or equal to 10 times the internal capacitance of the transistor between the control terminal (e.g., the gate terminal in the case of a field-effect transistor, or the base terminal in the case of a bipolar transistor) and the source terminal (e.g., the source terminal in the case of a field-effect transistor, or the emitter terminal in the case of a bipolar transistor). For example, it has been recognized that it is advantageous if the capacitance of the control capacitor 130 is greater than or equal to ten times the gate-source capacitance of the transistor 120. However, choosing a larger capacitance for the control capacitor 130 can further improve the quality of the output voltage at the output terminal 112 of the power supply filter circuit (where a larger capacitance of the control capacitor 130 results in a slower regulation speed and a higher workload). However, it has been found that choosing a sufficiently large capacitance for the control capacitor 130 is generally advantageous.

[0080] Furthermore, it has been recognized that in some embodiments, it is advantageous to couple a resistor between the output of a regulator (e.g., regulator 160, used to regulate the voltage across the load path of the transistor or to regulate the voltage between the input 110 and the output 120 of the power filter circuit) and the control terminal of the transistor. It has been recognized that such a transistor can help regulate the low-pass characteristics of the circuit and can also help prevent excessive current from flowing through the control terminal of the transistor.

[0081] Furthermore, it has been recognized that it is particularly advantageous to operate transistor 120 in the saturation region, and this can be achieved by appropriately adjusting the voltage across the load path of the transistor or by appropriately adjusting the voltage between the input terminal 110 and the output terminal 112 of the power supply filter circuit. Operating transistor 120 in the saturation region results in transistor 120 having a high output impedance (load path impedance), thereby providing good attenuation (or suppression) of voltage distortion at the output terminal 112 of the power supply filter circuit.

[0082] It has been found advantageous to adjust the voltage across the load path of the transistor, or the voltage difference between the input and output terminals of the power filter circuit, to a target value less than or equal to 1V. Using this adjustment, the power consumption of the power filter circuit can be kept reasonably low. Furthermore, it has been recognized that for many types of transistors, it is particularly advantageous to set the target voltage between 0.3V and 0.8V, or between 0.4V and 0.6V, for the voltage across the load path of the transistor, or the voltage between the input terminal 110 and the output terminal 112 of the power filter circuit. For many types of transistors, such a target value ensures that the transistor operates in the saturation region, and the power consumption of the power filter circuit remains at a very high value. Therefore, selecting such a target value for adjustment provides a particularly good trade-off between the output voltage quality and power consumption at the output terminal 112 of the power filter circuit.

[0083] It has also been recognized that it is advantageous to design power filter circuits in such a way that the bandwidth of the control loop used to regulate the voltage across the load path of the transistor or the voltage between the input and output terminals of the power filter circuit is limited. By limiting the bandwidth of the control loop, the output voltage at output terminal 112 of the power filter circuit 100 can be made to not follow (or only follow, substantially attenuatedly, such changes in the input voltage at input terminal 110) at frequencies higher than the bandwidth of the control loop. Accordingly, the frequency to which the bandwidth of the control loop is limited determines which portion of the noise and distortion on the input voltage at input terminal 110 is attenuated in the voltage at output terminal 112. It has been recognized that, depending on the specific application and also on the quality of the voltage at input terminal 110, it is reasonable to limit the bandwidth of the control loop to a value not exceeding 10 kHz, or not exceeding 5 kHz, or not exceeding 1 kHz, or not exceeding 500 Hz, or not exceeding 200 Hz, or not exceeding 100 Hz, or not exceeding 50 Hz.

[0084] Furthermore, it has been recognized that using a low-pass filter to limit the bandwidth of the control loop is advantageous because a well-defined bandwidth limitation can be achieved. For example, it has been recognized that, depending on the application and the characteristics of the input voltage at input 110, it is appropriate to use a low-pass filter with a cutoff frequency of less than or equal to 10 kHz, or less than or equal to 5 kHz, or less than or equal to 1 kHz, or less than or equal to 500 Hz, or less than or equal to 200 Hz, or less than or equal to 100 Hz.

[0085] By using a dedicated low-pass filter, well-defined characteristics of the control loop (used to regulate the voltage across the load path of the transistor or to regulate the voltage between the input 110 and the output 112 of the power filter circuit 100) can be achieved, thereby reducing well-defined characteristics of noise and distortion in the voltage at the output 112 of the power filter circuit.

[0086] However, it should be noted that, according to Figure 1 The power filter circuit 100 may optionally be supplemented by any features, functions and details discussed herein, which may be used individually or in combination.

[0087] 2. According to Figure 2 Power supply layout structure

[0088] Figure 2 A block diagram of a power supply arrangement structure 200 according to an embodiment of the present invention is shown.

[0089] The power supply arrangement 200 includes a switching power converter 210 and a power filter circuit 220. For example, the output 212 of the switching power converter 210 can be coupled to the input 222 of the power filter circuit 220. The output 224 of the power filter circuit 220 can, for example, be coupled to the output 214 of the power supply arrangement, and thus can provide an output voltage for the power supply arrangement. For example, the reference potential conductor of the power filter circuit 220 can be coupled to the reference potential conductor of the switching power converter 210, and can also be coupled to the reference potential conductor 216 of the power supply arrangement 200.

[0090] In particular, it should be noted that the power supply filter circuit 220 can, for example, correspond to the following: Figure 1 The power filter circuit 100.

[0091] Furthermore, it should be noted that the power filter circuit 220 may be adapted, for example, to the characteristics of the switching power converter 210, and also to the characteristics of the load, which may be coupled, for example, between the output terminal 214 of the power arrangement structure and the reference potential conductor 216 of the power arrangement structure 200.

[0092] For example, the power filter circuit 220 can be adapted to attenuate or suppress noise and distortion present in the output voltage of the switching power converter 210, such that the voltage at the output terminal 224 of the power filter circuit 220 has reduced noise and distortion compared to the voltage at the input terminal 222 of the power filter circuit. Accordingly, the power supply arrangement 200 allows the use of a highly efficient switching power converter 210, wherein noise and / or distortion in the output voltage of the switching power converter 210 (present at the output terminal 212 of the switching power converter 210) are attenuated or even suppressed by the power filter circuit 220, thereby providing a high-quality output voltage at the output terminal 214 of the power supply arrangement.

[0093] The use of active power filter circuit 220 reduces the quality requirements of the output voltage of switching power converter 210, enabling the switching power converter 210 to be implemented with lower implementation effort and higher efficiency, wherein the required space (or volume) of the switching power converter 210 can be kept at a reasonably low level. Furthermore, the power filter circuit 220, corresponding to power filter circuit 100, allows for response to noise and / or distortion with low power consumption and typically also with low implementation effort and small space (or volume) consumption.

[0094] Specifically, the power filter circuit 220 can be designed in such a way that it attenuates or suppresses the most relevant noise and distortion components provided by the switching power converter 210, while still allowing the output voltage 214 of the power supply arrangement to follow changes in the output voltage at the output terminal 212 of the switching power converter 210. Accordingly, through the combination of the switching power converter 210 and the power filter circuit 220, a good quality output voltage can be achieved at the output terminal 214 of the power supply arrangement 200, which simultaneously provides high efficiency, low power consumption, and low implementation effort.

[0095] As an example, the graphical representation of the output voltage of the switching power converter is shown at reference numeral 270, and the graphical representation of the output voltage of the power supply filter circuit is shown at reference numeral 272. In both cases, the horizontal axis describes time, and the vertical axis describes voltage. It can be seen that the output voltage of the switching power converter has a large amount of distortion, while the output voltage of the power supply filter circuit has only a small amount of distortion, the magnitude of which is significantly smaller than the magnitude of the distortion on the output voltage of the switching power converter.

[0096] Furthermore, it should be noted that it is advantageous to select the adjustment time constant within the power filter circuit 220 in a manner suitable to the characteristics of the switching power converter 210 and / or suitable to the characteristics of the output voltage at the output terminal 212 of the switching power converter 210. For example, it may be advantageous to adjust the adjustment time constant of the adjustment loop used to adjust the voltage across the load path of the transistor in the power filter circuit or the voltage between the input and output terminals of the power filter circuit to be greater than the cycle duration of the switching power converter. For example, it may be advantageous if the adjustment time constant is at least 2 times, or at least 5 times, or at least 10 times, or at least 20 times, or at least 50 times, or at least 100 times, or at least 200 times, or at least 500 times, or at least 1000 times the cycle duration of the switching power converter. For example, since some distortion at the output 212 of the switching power converter 210 is caused by switching in many cases and may have a periodicity related to the duration of the switching cycle of the switching power converter 210, it is advantageous to select the adjustment time constant within the power supply filter circuit to be related to the said duration of the switching cycle. By selecting the adjustment time constant of the power supply filter circuit 220 to be significantly greater than the duration of the switching cycle of the switching power converter 210, distortion with a periodicity related to the duration of the switching cycle can be well attenuated (or even suppressed) by the power supply filter circuit.

[0097] In summary, the good fit between the power filter circuit and the characteristics of the switching power converter allows for a good quality output voltage at the output terminal 214 of the power supply layout.

[0098] Furthermore, it should be noted that the power supply arrangement structure 200 may optionally be supplemented by any features, functions and details disclosed herein, which may be used individually or in combination.

[0099] 3. According to Figure 3 Automated testing equipment

[0100] Figure 3 A block diagram of an automated test apparatus 300 according to an embodiment of the present invention is shown. The automated test apparatus 300 includes a power supply arrangement structure 310, which may, for example, correspond to the power supply arrangement structure according to the present invention. Figure 2The power supply arrangement 200. For example, the power supply arrangement 300 can receive control signals for a switching power converter, wherein the control signals can define a desired voltage setting and / or a defined voltage variation, and can originate, for example, from a test processor of an automated test apparatus or from any other control unit of the automated test apparatus. Furthermore, the output voltage at the output terminal 312 of the power supply arrangement can be provided, for example, at the output port 320 of the automated test apparatus. The output voltage at the output port 320 of the automated test apparatus can be routed, for example, to the device under test, such as on a load board attached to the automated test apparatus.

[0101] For example, the automated test equipment is configured to programmably set or change the voltage provided by the switching power converter of the power supply arrangement 310, thereby setting the voltage at the output of the power filter circuit to a desired value. This voltage at the output of the power filter circuit can then be forwarded to the output port 320 of the automated test equipment and can constitute the power supply voltage for the device under test.

[0102] The power supply filter circuit may, for example, include a rapid-change mechanism configured to selectively bypass the load path of the transistor and / or bypass a low-pass filter in a regulating loop used to regulate the voltage across the load path of the transistor or to regulate the voltage between the input and output of the power supply filter circuit. Accordingly, even if the power supply filter circuit "normally" resists rapid changes in the output voltage at output port 320, the desired voltage can be quickly reached at the output port 320 of the automated test equipment. Therefore, a high-quality output voltage can be provided at the output port of the automated test equipment while achieving a fast (short) test cycle.

[0103] Furthermore, it should be noted that the automated test equipment 300 may optionally be supplemented by any features, functions, and details disclosed herein, which may be used individually or in combination.

[0104] 4. According to Figure 4 Power filter circuit

[0105] Figure 4 A block diagram of a power filter circuit according to an embodiment of the present invention is shown. The power filter circuit is designated by 400 and includes an input terminal (or voltage input terminal) 410 and an output terminal (or voltage output terminal) 412. Figure 4 As an example, a high-current, high-voltage source 480 is shown, wherein the output 482 of the high-current, high-voltage source 480 is coupled to the input 410 of a power supply filter circuit 400. For example, the high-current, high-voltage source may be a DC / DC converter, or may include a DC / DC converter. It can be assumed that the high-current, high-voltage source 480 provides a DC power supply voltage V. DCNoise voltage V 噪声 Superimposed on top of it. Accordingly, it can be assumed that the voltage at the input terminal 410 of the power supply filter circuit 400 can be, for example, a high-noise power supply voltage.

[0106] Furthermore, it can be assumed that the load 490 is coupled to the output terminal 412 of the power filter circuit 400, for example, between the output terminal 412 of the power filter circuit 400 and the reference potential conductor.

[0107] The power filter circuit 400 includes a MOSFET 420, wherein the drain terminal of the MOSFET 420 is coupled to the input terminal 410 of the power filter circuit, and the source terminal of the MOSFET 420 is coupled to the output terminal 412 of the power filter circuit 400. Accordingly, the load path (drain-source path) of the MOSFET is located between the input terminal 410 and the output terminal 412 of the power filter circuit 400. It should be noted that in this embodiment, the MOSFET 420 is an N-channel MOSFET.

[0108] The power filter circuit 400 further includes a control capacitor 430, wherein a first terminal of the control capacitor 430 is coupled to the gate terminal of the MOSFET 420, and wherein a second terminal of the control capacitor 430 is coupled to a reference potential conductor (e.g., ground conductor GND). The power filter circuit 400 further includes a stabilizing capacitor 440, wherein a first terminal of the stabilizing capacitor 440 is coupled to the source terminal of the MOSFET 420, and wherein a second terminal of the stabilizing capacitor is coupled to a reference potential conductor (e.g., ground conductor GND).

[0109] The power filter circuit 400 also includes a regulator 460, which is configured to regulate the difference between a low-pass filtered version 470 of the input voltage at input 410 (or the voltage at the drain terminal of MOSFET 420) and a reference voltage 472. For example, the regulator 460 may be configured to perform regulation so that the difference between the low-pass filtered version 470 of the input voltage and the reference voltage 472 tends to zero (or is zero). For example, the low-pass filtered version 470 of the input voltage is derived from the input voltage at input 410 of the power filter circuit 400 or from the voltage at the drain terminal of MOSFET 420 using a low-pass filter 474, which may, for example, include a low-pass filter resistor 474a and a low-pass filter capacitor 474b. For example, the low-pass filter resistor 474a may be coupled in series between the input terminal 474c and the output terminal 474d of the low-pass filter. Low-pass filter capacitor 474b may, for example, be coupled between the output terminal 474d of low-pass filter 474 and ground conductor GND. For example, reference voltage 472 can be derived from the output voltage at output terminal 412 of power filter circuit 420 or from the voltage at the source terminal of MOSFET 420 using a potential offset, which may be achieved, for example, by a floating voltage reference 476. For example, floating voltage reference 476 may function as a voltage source, coupled between the output terminal 412 of power filter circuit (or the source terminal of MOSFET 420) and the input terminal of regulator 460. Power filter circuit 400 may have a subtraction function 478 that allows adjustment of the difference between the low-pass filtered version 470 of the input voltage and reference voltage 472 to a desired target value (e.g., tending towards zero) or to a desired target value (e.g., zero). The output terminal of regulator 460 is coupled to the gate terminal of MOSFET 420.

[0110] The function of power supply circuit 400 will be described below. This power supply circuit can be considered as an active power filter. However, it should be noted that MOSFET 420 can correspond to transistor 120, control capacitor 430 can correspond to control capacitor 130, stabilizing capacitor 440 can correspond to stabilizing capacitor 140, and regulator 460, low-pass filter 474, floating voltage reference 476, and (optionally) subtraction function 478 can correspond to regulator 160.

[0111] from Figure 4As can be seen, the output voltage of the high-current, high-voltage source 480 is applied to the input terminal 410 of the power filter circuit 400, and the load 490 is coupled to the output terminal 412 of the power filter circuit 400. The power supply current provided by the high-current, high-voltage source 480 flows to the load 490 through the drain-source path of the MOSFET 420. Furthermore, it should be noted that the current flowing through the drain-source path of the MOSFET 420 is generally relatively insensitive to changes in the drain-source voltage of the MOSFET 420, provided that the MOSFET 420 operates in the active region of its output characteristic field. Due to the influence of the control capacitor 430 and the stabilizing capacitor 440, and also due to the limited bandwidth of the regulation loop, relatively rapid fluctuations in the voltage at the input terminal 410 of the power filter circuit 400 (which may be caused by noise and / or distortion of the power supply voltage provided by the high-current, high-voltage source 480) do not significantly affect the voltage at the output terminal 412 of the power filter circuit, but only cause changes in the drain-source voltage of the MOSFET 420. In other words, the high output impedance of MOSFET 420 causes noise and distortion present at the input voltage of power filter circuit 400 to be decoupled from the output 412 of power filter circuit. Control capacitor 430 and stabilizing capacitor 440 help maintain a substantially constant gate-source voltage of MOSFET 420 in the presence of such noise and / or distortion at the input 410 of power filter circuit, which helps to provide a low-noise / low-distortion voltage at the output 412 of power filter circuit.

[0112] However, it should also be noted that the (average) drain-source voltage of MOSFET 420 is regulated using regulator 460, where the target drain-source voltage is determined, for example, by a floating voltage reference 476. Accordingly, regulator 460 can actually provide the gate voltage of MOSFET 420 to make the (average) drain-source voltage of MOSFET 420 tend toward the target drain-source voltage. The target drain-source voltage is typically chosen such that MOSFET 420 operates in the active region of its output characteristic field and that the voltage drop across the drain-source path of MOSFET 420 is reasonably low. Therefore, the voltage at the output terminal 412 of power filter 400 follows the (average) voltage at the input terminal 410 of the power filter circuit (e.g., with good steady-state accuracy). However, due to the limited bandwidth of the regulation loop used to regulate the drain-source voltage of MOSFET 420 (which is determined, for example, primarily by low-pass filter 474), the drain-source voltage of MOSFET 420 is intentionally not kept constant in the event of rapid voltage fluctuations at the input terminal 410 of the power supply filter circuit (where such rapid fluctuations may be caused, for example, by noise and distortion).

[0113] In other words, the adjustment of the drain-source voltage of MOSFET 420 to the desired value is intentionally too slow to follow the rapid fluctuations of the input voltage at the input terminal 410 of the power filter circuit. As a result, such rapid fluctuations of the input voltage at the input terminal 410 of the power filter circuit only cause changes in the drain-source voltage of MOSFET 420 without significantly affecting the voltage at the output terminal 412 of the power filter circuit.

[0114] The function of the circuit will be further explained below with reference to Figures 5a, 5b, 6a, and 6b. For example, Figure 5a shows a graphical representation of the characteristic curves of a power MOSFET (e.g., type BSC320N20NS3) generated by LTSpice simulation.

[0115] The characteristic curves of a power MOSFET (e.g., power MOSFET 420) are graphically represented by 500. The horizontal axis 510 describes the drain-source voltage, and the vertical axis 512 describes the drain current. Graphical representation 500 shows the output curves 520, 522, and 524 at different gate-source voltages. It can be seen that for a drain-source voltage of 0.5 volts, the power MOSFET operates in the saturation region (with high output impedance) over a wide range of gate-source voltages.

[0116] For example, a drain-source voltage of 0.5 volts can be chosen as the regulation target (e.g., for regulator 460), where such regulation of the (average) drain-source voltage has the effect that the power MOSFET operates in the saturation region over a wide range of gate-source voltages (and therefore a wide range of gate-source currents). Furthermore, it can be assumed that the drain-source voltage of MOSFET 420 varies around an average value of 0.5 volts as defined by the regulation target due to fluctuations in the input voltage at input terminal 410 of the power filter circuit caused by noise or other distortions. However, the regulation target (e.g., 0.5V) is preferably chosen such that, for any "normal" fluctuations in the input voltage at input terminal 410 of the power filter circuit, transistor 420 remains in the saturation region with high output impedance (i.e., a small slope of drain current with respect to drain-source voltage). The result of this design is that rapid (high-frequency) fluctuations in the input voltage do not significantly affect the output voltage at output terminal 412 of the power filter circuit, but only cause fluctuations in the drain-source voltage of MOSFET 420.

[0117] Therefore, good attenuation of noise and distortion on the input voltage of the power supply filter circuit can be achieved, especially for noise and distortion at frequencies higher than the bandwidth of the regulation loop. In contrast, the relatively slow changes in the average input voltage of the power supply filter circuit will have the effect that the output voltage of the power supply filter circuit follows these slow changes in the average input voltage, with a voltage offset, for example, defined by the floating voltage reference 476. Therefore, the operating point (especially the average drain-source voltage of the MOSFET) will remain constant in this case.

[0118] As an additional note, it should be observed that the characteristic curve of the power MOSFET shown in Figure 5a has been determined using the LTSpice simulation model shown in Figure 5b with reference numeral 550. In other words, the output characteristic curve of the power MOSFET shown in Figure 5a has been created by varying the drain-source voltage of the power MOSFET, where the gate-source voltage is set to multiple discrete values, such as three discrete values.

[0119] However, it should be noted that different power MOSFETs have similar characteristics, although some details may vary.

[0120] The effectiveness of the power supply filter circuit 400 will be explained below with reference to Figures 6a and 6b. For example, Figures 6a and 6b show graphical representations of the noise at the input voltage (Figure 6a) and output voltage (Figure 6b) of the power supply filter circuit 400, respectively. The noise was measured by an oscilloscope with a resolution of 5 mV / division and a time resolution of 500 microseconds / division. A filter bandwidth of 20 MHz was used.

[0121] For example, Figure 6a shows a graphical representation of the noise at the input of the active filter. The horizontal axis 610 describes time, and the vertical axis 612 describes voltage. It can be seen that the peak-to-peak voltage of the distortion at the input of the active filter is approximately 32 mV. Figure 6b shows a graphical representation of the noise measured at the output of the active filter. The horizontal axis 620 describes time, and the vertical axis 622 describes voltage. It can be seen from Figure 6b that the peak-to-peak voltage of the noise is approximately 6 mV. Therefore, it can be recognized that when compared with the noise at the input of the active filter, the power supply filter circuit 400 is able to attenuate the noise (measured as peak-to-peak voltage) at the output of the active filter to approximately one-fifth.

[0122] However, it is evident that different effects (and effectiveness) can be achieved by designing the power filter circuit with different dimensions. Furthermore, the attenuation of noise and / or other distortions naturally depends on the frequency content of the noise and / or distortion.

[0123] In addition, it should be noted that, according to Figure 4 The power filter circuit 400 can be optionally modified in different ways.

[0124] For example, a MOSFET can optionally be replaced by a bipolar transistor. Furthermore, the voltage polarity can be naturally reversed, where the transistor type can be changed from an n-channel transistor to a p-channel transistor. Additionally, the regulator structure can be modified, where it should be noted that... Figure 4 The structures shown should be considered as abstract examples only.

[0125] Furthermore, any features, functions, and details described herein may optionally be incorporated into [the application / system]. Figure 4 In the power supply filter circuit 400.

[0126] Furthermore, the features discussed regarding the power filter circuit 400 can optionally be incorporated into any other embodiment, and these features, functions, and details can be used individually or in combination.

[0127] 5. According to Figure 7 Power filter circuit

[0128] Figure 7 A block diagram of a power filter circuit according to another embodiment of the present invention is shown. The power filter circuit 700 is designated as 700.

[0129] The power filter circuit 700 is similar to the power filter circuit 400. For example, the power filter circuit 700 includes an input terminal 710 corresponding to input terminal 410 and an output terminal 712 corresponding to output terminal 412. The power filter circuit 700 also includes a MOSFET 720 corresponding to MOSFET 420. The power filter circuit 700 further includes a control capacitor 730 corresponding to control capacitor 430 and a stabilizing capacitor 740 corresponding to stabilizing capacitor 440.

[0130] It should be noted that the input voltage at input terminal 710 of the power filter circuit 700 is assumed to be positive relative to the reference potential at the reference potential conductor (or ground conductor) GND. Accordingly, MOSFET 720 is preferably an N-channel MOSFET (NMOS).

[0131] Furthermore, it should be noted that the actual implementation of the regulator 760, which provides the gate voltage of the MOSFET 720, differs slightly from that of regulator 460, although the basic function remains the same. This regulation (providing the gate voltage to the MOSFET 720) includes, for example, an integral regulator formed using a differential amplifier (e.g., an operational amplifier) ​​762, an integrating capacitor 764, and a resistor 766. For example, a reference voltage 772 is set that is offset by a predetermined value, such as V, relative to the source voltage at the source terminal of the MOSFET 720 (or equivalently, relative to the voltage at the output 712 of the power supply filter circuit).REF For example, a floating voltage reference 776 can be used, wherein a first terminal (e.g., the positive terminal) of the floating voltage reference 776 can be coupled to an input terminal (e.g., the inverting input terminal) of a differential amplifier 762 via a resistor 766. A second terminal (e.g., the negative terminal) of the floating voltage reference 776 can be coupled, for example, to the source terminal of a MOSFET 720 (or equivalently, to the output terminal 712 of a power supply filter circuit 700). An integrating capacitor 762 can be coupled, for example, between the second input terminal (e.g., the inverting input terminal) of the differential amplifier 762 and the output terminal of the differential amplifier 762, wherein the output terminal of the differential amplifier 762 is also coupled to the gate terminal of the MOSFET 720.

[0132] A low-pass filter 774 may, for example, be coupled between the drain terminal of the MOSFET 720 (or equivalently, the input 710 of the power supply filter circuit 700) and the first input terminal (e.g., the non-inverting input terminal) of the differential amplifier 762. The low-pass filter 774 may, for example, include a low-pass filter resistor 774a and a low-pass filter capacitor 774b. For example, the low-pass filter resistor 774a is coupled between the drain terminal of the MOSFET 720 and the first input terminal (e.g., the non-inverting input terminal) of the differential amplifier 762, and the low-pass filter capacitor 774b is coupled between the first input terminal (e.g., the non-inverting input terminal) of the differential amplifier 762 and the reference potential conductor (or ground conductor) GND.

[0133] Accordingly, the voltage at the first input terminal (e.g., the non-inverting input terminal) of the differential amplifier 762 is a low-pass filtered version of the voltage at the input terminal of the power supply filter circuit 700 (or equivalently, the voltage at the drain terminal of the MOSFET), and the voltage at the first terminal of the resistor 766 is a voltage offset version of the voltage at the output terminal 712 of the power supply filter circuit 700 (or equivalently, the voltage at the source terminal of the MOSFET 720). Accordingly, the adjustment performed using the differential amplifier 762 (and supported by the integrating capacitor 764) enables the potential at the drain terminal of the MOSFET 720 to be aligned with the voltage offset potential at the first terminal of the floating voltage reference 776. Accordingly, the result is that the adjustment is used to align the voltage between the drain terminal and the source terminal of the MOSFET 720 with the voltage of the floating voltage reference 776. Therefore, the effect is that, at least under steady-state conditions, the drain-source voltage is adjusted to be equal to the reference voltage V. REF The low-pass filter 774 is intentionally designed to prevent rapid adjustment, which helps suppress noise in the power supply voltage applied to the input 710 of the power supply filter circuit.

[0134] However, it should be noted that, according to Figure 7The power filter circuit 700 may optionally be supplemented by any features, functions and details disclosed herein, which may be used individually or in combination.

[0135] 6. According to Figure 8 Power filter circuit

[0136] Figure 8 A block diagram of a power filter circuit 800 according to an embodiment of the present invention is shown. Figure 8 The power filter circuit 800 is similar to that based on Figure 7 The power filter circuit 700 includes an input terminal 810 corresponding to input terminal 710 and an output terminal 812 corresponding to output terminal 712. Furthermore, the power filter circuit 800 includes a MOSFET 820, which has a similar function to MOSFET 720 but is of the opposite type (P-channel MOSFET or "PMOS"). The power filter circuit 800 also includes a control capacitor 830 corresponding to control capacitor 730 and a stabilizing capacitor 840 corresponding to stabilizing capacitor 740. The power filter circuit 800 also includes a regulator 860, which is similar to regulator 760 but includes a different circuit structure.

[0137] It should be noted that the power supply filter circuit 800 is configured to filter input voltages that are negative relative to the reference potential at the reference potential conductor (or ground conductor) GND. Accordingly, a P-channel MOSFET 820 is used instead of an N-channel MOSFET.

[0138] The regulation includes a differential amplifier (e.g., an operational amplifier) ​​862, the output of which is coupled to the gate of a MOSFET 820. An integrating capacitor 864 is coupled between the second (e.g., inverting) input of the differential amplifier 862 and its output. Furthermore, it should be noted that the source terminal of the MOSFET 820 is coupled to the second input (e.g., inverting) terminal of the differential amplifier 862 via a resistor 866, which converts the voltage difference between the source terminal of the MOSFET 820 and the second input (e.g., inverting) terminal of the differential amplifier 862 into a current that is integrated across the integrating capacitor 864.

[0139] The voltage at the drain terminal of MOSFET 820 is offset, for example, in the positive direction using a floating voltage reference 876. Correspondingly, an offset version of the voltage at the drain terminal of MOSFET 820 exists at the first terminal 872 of the floating voltage reference 876. The first terminal of the floating voltage reference 876 is coupled to the first input terminal (e.g., non-inverting input) of the differential amplifier 862 via a low-pass filter 874, wherein a low-pass filter resistor 874a is coupled between the first terminal of the floating voltage reference 876 and the first input terminal (e.g., non-inverting input) of the differential amplifier 862. A low-pass filter capacitor 874b is coupled between the first input terminal (e.g., non-inverting input) of the differential amplifier 862 and a reference potential conductor or ground conductor GND. The second terminal of the floating voltage reference 876 is coupled to the drain terminal of MOSFET 820 (or equivalently, the input terminal 810 of the power supply filter circuit). Accordingly, a voltage offset and a low-pass filtered version of the MOSFET 820 at its drain terminal are applied to the first input of the differential amplifier 862.

[0140] The differential amplifier and integrating capacitor 864 work together to perform a regulation function. This regulation function makes the potential at the first input terminal of the differential amplifier 862 equal to the potential at the second input terminal of the differential amplifier. This effectively means that the regulation makes the gate-source voltage of the MOSFET 820 tend to be (or equal to) the voltage defined by the floating voltage reference 876. Accordingly, a basic function similar to that of the power supply filter circuit 700 is achieved.

[0141] However, it should be noted that the power supply filter circuit 800 may optionally be supplemented by any features, functions and details disclosed herein, which may be used individually or in combination.

[0142] 7. According to Figure 9 Power filter circuit

[0143] Figure 9 A schematic diagram of a power filter circuit according to an embodiment of the present invention is shown. Figure 9 The power filter circuit 900 includes an input terminal 910, which may correspond to input terminals 410, 710, and 810. The power filter circuit 900 also includes an output terminal 912, which may correspond to output terminals 412, 712, and 812.

[0144] For example, output terminal 910 is intended to apply a positive voltage (positive relative to the reference potential at the reference potential conductor or ground conductor GND), which can be provided, for example, by a DC / DC converter. A load is coupled between output terminal 912 and the reference potential conductor or ground conductor GND. An N-channel MOSFET 920 is coupled between input terminal 910 and output terminal 912, wherein the drain terminal of MOSFET 920 is coupled to the input terminal, and the source terminal of MOSFET 920 is coupled to output terminal 912. A bypass circuit 922 is coupled in parallel to the drain-source path of MOSFET 920, wherein the bypass circuit 920 can, for example, include a series circuit of two (or more) diodes. For example, the anode of the first diode 922a is coupled to the drain terminal of MOSFET 920, the cathode of the first diode 922a is coupled to the anode of the second diode 922b, and the cathode of the second diode 922b is coupled to the source terminal of MOSFET 920. Accordingly, these diodes are directed to conduct in the "normal" current flow direction in the drain-source path of MOSFET 920 (from the drain terminal to the source terminal). Therefore, the bypass circuit 922 becomes active when the drain-source voltage of MOSFET 920 exceeds the sum of the threshold voltages of diodes 922a and 922b. In other words, when the voltage at input 910 of the power filter circuit exceeds the voltage at output 912 of the power filter circuit 900 by a value exceeding the sum of the threshold voltages of diodes 922a and 922b, current will flow through the bypass circuit 922, bypassing the drain-source path of MOSFET 920. Therefore, the drain-source voltage of MOSFET 920 typically does not significantly exceed the sum of the threshold voltages of diodes 922a and 922b in the bypass circuit 922. However, it should be noted that the bypass circuit may, for example, consist of only a single diode, or may include a series circuit of more than two diodes.

[0145] The power filter circuit 900 also includes a control capacitor 930 and a stabilizing capacitor 940, wherein the control capacitor 930 corresponds to control capacitors 430, 730, and 830, and wherein the stabilizing capacitor 940 corresponds to stabilizing capacitors 440, 740, and 840. However, it should be noted that a gate resistor 932 is coupled between the first terminal of the control capacitor 930 and the gate terminal of the MOSFET 920. The power filter circuit 900 also includes a regulator 960, which, as a core component, includes a differential amplifier or operational amplifier 962. An integrating capacitor 964 is coupled between the second inverting input terminal of the differential amplifier 972 and the output terminal of the differential amplifier 972. An additional resistor 965 is coupled between the output terminal of the differential amplifier 962 and the first terminal of the control capacitor 930 (wherein the second terminal of the control capacitor 930 is coupled to a reference potential conductor or a ground conductor (GND)).

[0146] The power supply filter circuit 900 includes a low-pass filter 974, wherein the input of the low-pass filter is coupled to the drain terminal of a MOSFET 920, and the output of the low-pass filter is coupled to the first (non-inverting) input of a differential amplifier 962 via a resistor 975. The low-pass filter includes a low-pass filter resistor 974a coupled between the drain terminal of the MOSFET 920 and the output of the low-pass filter. The low-pass filter 974 further includes a low-pass filter capacitor 974b coupled between the output of the low-pass filter 974 and a reference potential conductor or ground conductor GND. Therefore, the low-pass filter 974 is a first-order RC low-pass filter.

[0147] However, the low-pass filter 974 also includes a bypass circuit 974c, which comprises an anti-parallel circuit of two diodes coupled in parallel with the low-pass filter resistor 974a. Accordingly, if the voltage across the low-pass filter resistor 974a becomes greater than the threshold voltage of the corresponding diode, the bypass circuit 974c becomes active and bypasses the low-pass filter resistor 974a. Similarly, if the voltage at the drain terminal of the MOSFET 920 changes rapidly beyond the threshold voltage of the corresponding diode in the bypass circuit 974c, the low-pass filter capacitor 974 is rapidly reloaded. However, when the difference between the voltage at the drain terminal of the MOSFET 920 and the voltage at the first terminal of the low-pass filter capacitor 974 becomes less than the threshold voltage of the corresponding diode in the bypass circuit 974c, the bypass circuit 974c becomes substantially inactive, and the low-pass filter resistor 974a becomes active again. Accordingly, for cases of large and rapid changes in the drain voltage of MOSFET 920, the bypass circuit 974c significantly reduces the reload time constant for reloading the low-pass filter capacitor 974b. However, once the voltage at the first terminal of the low-pass filter capacitor 974b is sufficiently close to the voltage at the drain terminal of MOSFET 920, the low-pass filter becomes active with a time constant defined by the resistance of the low-pass filter resistor 974a and the capacitance of the low-pass filter capacitor 974b. In other words, the bypass circuit 974c only functions when the voltage at the drain terminal of MOSFET 920 changes rapidly and significantly (greater than the threshold voltage of the diode in the bypass circuit 974c).

[0148] The power filter circuit 900 further includes a floating voltage reference 976. The floating voltage reference 976 includes a Zener diode 976a and a bias resistor 976b, wherein the bias resistor 976b is coupled in series with the Zener diode 976a between the positive power supply voltage of the differential amplifier 962a and the source terminal of the MOSFET 920 (wherein the source terminal of the MOSFET 920 is coupled to the (negative) power supply voltage terminal of the differential amplifier 962a and the anode of the Zener diode 976a). Accordingly, the potential of the first terminal (e.g., cathode) of the Zener diode 976a relative to the potential at the source terminal of the MOSFET 920 (e.g., in the positive direction) is deflected by the Zener voltage of the Zener diode. A series circuit of two resistors 976c and 976d is coupled in parallel with the Zener diode 976a, and a tap between the resistors 976c and 976d is coupled to the second (inverting) input of the differential amplifier 962 via a resistor 964. Accordingly, the voltage at the tap between resistors 976c and 976d is offset relative to the voltage at the source terminal of MOSFET 920 by a portion of the Zener voltage of Zener diode 976a, which is (primarily) defined by the values ​​of resistors 976c and 976d.

[0149] Accordingly, the adjustment operation is performed to make the voltage at the tap between resistors 976c and 976d match the voltage at the output of the low-pass filter 974. Consequently, in steady state, the drain-source voltage of transistor 920 is adjusted to a value determined by the Zener voltage of Zener diode 976a and the values ​​of resistors 976c and 976d.

[0150] As a further note, it should be observed that the power supply filter circuit 900 includes a voltage source 990 that provides a power supply voltage to the differential amplifier 962, which is greater than the voltage at the drain terminal of the MOSFET 920. The power supply filter circuit 900 also includes a capacitor 992 coupled between the positive and negative power supply voltage terminals of the differential amplifier 962, and helps stabilize the power supply voltage of the differential amplifier 962. Furthermore, diodes 994 and 996 are present, which limit the voltage at the first terminal of the control capacitor 930 to approximately a range between the negative and positive power supply voltages of the differential amplifier 962.

[0151] In short, according to Figure 9The power supply filter circuit 900 has similar functionality to other power supply voltage filter circuits disclosed herein, but additionally includes bypass circuits 922 and 974c. Therefore, the circuit starts up faster, and the voltage change at the output terminal 912 of the power supply filter circuit is also faster (e.g., through the bypass low-pass filter resistor 974a).

[0152] Furthermore, it should be noted that the power supply filter circuit 900 may optionally be supplemented by any features, functions, and details disclosed herein, which may be used individually or in combination.

[0153] 8. According to Figure 10 Power filter circuit

[0154] Figure 10 A schematic diagram of a power filter circuit 1000 according to an embodiment of the present invention is shown.

[0155] The power filter circuit 1000 is similar to other power filter circuits disclosed herein and includes an input terminal 1010 and an output terminal 1012. The power filter circuit 1000 is intended to apply a negative voltage (e.g., negative relative to a reference potential conductor or ground conductor GND) at the input terminal 1010. For this purpose, the power filter circuit 1000 includes a P-channel MOSFET 1020, wherein the source terminal of the MOSFET 1020 is coupled to the output terminal 1012, and wherein the drain terminal of the MOSFET 1020 is coupled to the input terminal 1010.

[0156] The power filter circuit 1000 also includes a bypass circuit 1022, which comprises two diodes 1022a and 1022b connected in series. For example, the cathode of the first diode 1022a can be coupled to the drain terminal of the MOSFET, the anode of the first diode 1022a can be coupled to the cathode of the second diode 1022b, and the anode of the second diode 1022b can be coupled to the source terminal of the MOSFET 1020. Accordingly, the current direction through the bypass circuit 1022 can be the same as the "normal" current direction through the drain-source path of the MOSFET 1020. Accordingly, the bypass circuit 1022 can substantially limit the source-drain voltage of the MOSFET 1020 to the sum of the threshold voltages of the diodes 1022a and 1022b.

[0157] The power filter circuit 1000 also includes a control capacitor 1030 and a stabilizing capacitor 1040, wherein the control capacitor 1030 corresponds to the control capacitor 930, and wherein the stabilizing capacitor 1040 corresponds to the stabilizing capacitor 940. Furthermore, the power filter circuit 1000 includes a resistor 1032 corresponding to resistor 932. The power filter circuit 1000 also includes a regulator 1060, which includes a differential amplifier 1062. An integrating capacitor 1064 is coupled between the second (inverting) input terminal of the differential amplifier (e.g., an operational amplifier) ​​1062 and the output terminal of the differential amplifier 1062. Furthermore, a resistor 1065 is coupled between the output terminal of the differential amplifier 1062 and the first terminal of the control capacitor 1030, wherein resistor 1065 may correspond to resistor 965.

[0158] A floating voltage reference 1076 is coupled between the drain terminal of MOSFET 1020 and the input of low-pass filter 1074. For example, the floating voltage reference 1076 comprises two resistors connected in series, coupled between the drain terminal of MOSFET 1020 and a potential that is increased by a predetermined value (e.g., 10V) relative to the drain terminal potential of MOSFET 1020 (e.g., through a floating voltage source). Accordingly, the voltage at the tap between resistors 1076a and 1076b is offset by a predetermined voltage (at least in steady state) (e.g., in the positive direction) compared to the voltage at the drain terminal of MOSFET 1020. The tap between resistors 1076a and 1076b is coupled to a first terminal of low-pass filter resistor 1074a, wherein a second terminal of low-pass filter resistor 1074a is coupled to a first terminal of low-pass filter capacitor 1074b. The second terminal of low-pass filter capacitor is coupled to a reference potential conductor or ground conductor GND. The first terminal of the low-pass filter capacitor also serves as the output terminal of the low-pass filter and is coupled to the first (non-inverting) input terminal of the differential amplifier 1062.

[0159] The second input terminal (e.g., the inverting input terminal) of the differential amplifier 1062 is coupled to the source terminal of the MOSFET via a resistor. Furthermore, it should be noted that an anti-parallel diode circuit is coupled between the source terminal of the MOSFET 1020 and the first (non-inverting) input terminal of the differential amplifier 1062, which substantially limits the deviation between the voltage at the first (non-inverting) input terminal of the differential amplifier 1062 and the voltage at the source terminal of the MOSFET 1020 within the threshold voltage range of the diodes 1074c and 1074d.

[0160] As an additional note, it should be observed that capacitors 1092 and 1093 stabilize the power supply voltage of differential amplifier 1062, and diodes 1094 and 1096 substantially limit the voltage at the first terminal of control capacitor 1030 to the range between the negative power supply voltage and the positive power supply voltage of differential amplifier 1062.

[0161] The voltage at the input of low-pass filter 1074 is offset by a predetermined value, approximately 0.5V, relative to the voltage at the drain terminal of MOSFET 1020. Low-pass filter 1074 is coupled between this offset voltage tap and the first input terminal (the non-inverting input terminal of differential amplifier 1062). The voltage at the first input terminal (non-inverting input terminal) of differential amplifier 1062 is limited to a range near the voltage at the source terminal of MOSFET 1020. Accordingly, regulation is performed to adjust the drain-source voltage of the MOSFET to a value defined by the offset between the voltage at the drain terminal of the MOSFET and the voltage at the input of low-pass filter 1074 (at least in steady state).

[0162] Regarding the function of the power filter circuit 1000, the discussion of the power filter circuit disclosed in this article is also referenced.

[0163] Furthermore, it should be noted that the power filter circuit 1000 may optionally be supplemented by any features, functions, and details disclosed herein.

[0164] 9. Conclusion

[0165] An active power supply filter for higher voltages is created according to embodiments of the present invention. In other words, an active filter circuit for high-voltage power supply applications is created according to embodiments of the present invention, where very low noise is required and standard passive filtering methods require too much board space.

[0166] Alternatively, this invention describes an alternative method for active filtering noise DC power supply voltage, which is of interest for high-voltage applications that desire or require high circuit density on printed circuit boards (PCBs).

[0167] The block diagram of the circuit can be, for example, in Figure 4 I saw it in the middle.

[0168] The following section will provide a description of the features. Figure 4 The block diagram provides a general overview of the power supply filter and load circuit. The filtering itself is mainly accomplished by three components: a power MOSFET (e.g., an N-MOS for positive supply voltage, or a P-MOS for negative supply voltage) located between IN and OUT, and two capacitors C. CTRL and CSTAB .

[0169] MOSFETs are preferably operated in the saturation region at a certain V DS Operation. The characteristic curve of a power MOSFET (as shown in Figure 5a, for example) illustrates the typical behavior of a MOSFET. The typical operating region of an active filter is marked by box 530. Within this region, the MOSFET behaves almost as expected at a certain V. GS The current source below (V) DS A change of approximately 10mV will cause I DS or V GS (where V) GS Let V be the gate-source voltage, and where V is the gate-source voltage. DS Let I be the drain-source voltage, and where I is the drain-source voltage. DS (This refers to the drain current).

[0170] V DS (Drain-source voltage) is determined, for example, by a floating reference (V) DS equals V REF Furthermore, the value should be chosen as low as possible to minimize the MOSFET's power consumption, but high enough to filter out noise. V GS Equal to 0.5V (or V) DS A voltage of 0.5V is a good starting point.

[0171] Gate to GND voltage V CTRL It should preferably be made of C CTRL It must remain very stable (or, in some cases, must remain very stable). From a filtering perspective, this voltage can be considered, for example, static (e.g., adjusted very slowly by a regulating circuit). A C of a few microfarads is preferred. CTRL (Or even necessary in some embodiments) to stabilize the output voltage.

[0172] V DS The adjustment is done by the regulator. V IN and V OUT (For example, input voltage and output voltage) Both should be monitored (or required to be monitored in some embodiments), as V DS (Drain-source voltage) regulated input. V IN It should preferably be filtered (or in some embodiments requires filtering), for example by a low-pass filter with the lowest possible bandwidth (preferably less than 100 Hz) to obtain a very clean reference signal.

[0173] As a regulator, an OpAmp (e.g., an operational amplifier) ​​is typically used, which can be extremely simple in terms of bandwidth and power consumption.

[0174] Typical applications will be described below. The filtering method described above was tested on a DC / DC converter test board in the project. The DC / DC converter generates -65V and -2A, and the V in the filter circuit... DS The voltage was adjusted to 0.5V. Figure 6a shows the voltage at the input of the active filter. Figure 6b shows the voltage at the output of the active filter. In both cases, noise was measured with an oscilloscope at a resolution of 5 mV / division, a time resolution of 500 ms / division, and a filter bandwidth of 20 MHz.

[0175] Figure 7 and Figure 8 A more detailed block diagram is shown, in which Figure 7 A block diagram of an active power supply filter for positive voltage is shown, and in which... Figure 8 A block diagram of an active power supply filter for negative voltages is shown. Figure 9 and Figure 10 Further implementation details are shown. In particular, Figure 9 A schematic diagram of an active power supply filter for positive voltage is shown, and Figure 10 A schematic diagram of an active power supply filter for negative voltages is shown.

[0176] In summary, a concept has been presented that offers a good trade-off between voltage quality, implementation workload, and power consumption.

Claims

1. A power supply filter circuit (100; 220; 400; 700; 800; 900; 1000). The power filter circuit includes transistors (120; 420; 720; 820; 920; 1020), control capacitors (130; 430; 730; 830; 930; 1030), and stabilizing capacitors (140; 440; 740; 840; 940; 1040). The load path of the transistor is coupled between the input terminal (110; 410; 710; 810; 910; 1010) and the output terminal (112; 412; 712; 812; 912; 1012) of the power filter circuit. The control capacitor is coupled between the control terminal of the transistor and the reference potential conductor (GND); The stabilizing capacitor is coupled between the source terminal of the transistor and the reference potential conductor. The power filter circuit is configured to regulate the voltage across the load path of the transistor or the voltage between the input and output terminals of the power filter circuit.

2. The power filter circuit (100; 220; 400; 700; 800; 900; 1000) according to claim 1. The capacitance of the control capacitor (130; 430; 730; 830; 930; 1030) is greater than or equal to 10 times the internal capacitance of the transistor between the control terminal and the source terminal of the transistor (120; 420; 720; 820; 920; 1020), or... The capacitance of the control capacitor is greater than or equal to 20 times the internal capacitance of the transistor between the control terminal and the source terminal, or The capacitance of the control capacitor is greater than or equal to 50 times the internal capacitance of the transistor between the control terminal and the source terminal, or The capacitance of the control capacitor is greater than or equal to 100 times the internal capacitance of the transistor between the control terminal and the source terminal of the transistor.

3. The power filter circuit (100; 220; 400; 700; 800; 900; 1000) according to claim 1 or 2. The power filter circuit includes resistors (932, 965; 1032, 1065) coupled between the output of a regulator (960; 1060) and the control terminal of the transistor. The regulator is used to adjust the voltage across the load path of the transistor or to adjust the voltage between the input and output terminals of the power filter circuit. The resistor coupled between the output terminal of the regulator and the control terminal of the transistor is configured to form a low-pass filter together with the control capacitor.

4. The power filter circuit according to any one of claims 1 to 3 (100; 220; 400; 700; 800; 900; 1000). The power filter circuit is configured to adjust the voltage across the load path of the transistor (120; 420; 720; 820; 920; 1020) or the voltage between the input terminal (110; 410; 710; 810; 910; 1010) and the output terminal (112; 412; 712; 812; 912; 1012) of the power filter circuit, so that the transistor operates in the saturation region.

5. The power filter circuit according to any one of claims 1 to 4 (100; 220; 400; 700; 800; 900; 1000). The power filter circuit is configured to regulate the voltage across the load path of the transistors (120; 420; 720; 820; 920; 1020) to a target value less than or equal to 1V, or The power filter circuit is configured to regulate the voltage across the load path of the transistor to a target value within the range of 0.3V to 0.8V, or The power filter circuit is configured to regulate the voltage across the load path of the transistor to a target value within the range of 0.4V to 0.6V, or The power filter circuit is configured to adjust the voltage difference between the input terminal (110; 410; 710; 810; 910; 1010) and the output terminal (112; 412; 712; 812; 912; 1012) of the power filter circuit to a target value less than or equal to 1V, or The power filter circuit is configured to adjust the voltage difference between its input terminal and its output terminal to a target value within the range of 0.3V to 0.8V, or The power filter circuit is configured to adjust the voltage difference between the input terminal and the output terminal of the power filter circuit to a target value within the range of 0.4V to 0.6V.

6. The power filter circuit according to any one of claims 1 to 5 (100; 220; 400; 700; 800; 900; 1000). The power filter circuit is configured such that the voltage across the load path of the transistors (120; 420; 720; 820; 920; 1020) or the voltage between the input (110; 410; 710; 810; 910; 1010) and the output (112; 412; 712; 812; 912; 1012) of the power filter circuit is controlled by a control loop (474, 476, 478, 460; 774, 776, 762, 764, 766; 876, 874, 862, 864, 866; 974, 976, 962, 964, 966, 975). The bandwidth of 1074, 1076, 1062, 1064, 1066 is limited to a value not exceeding 10 kHz, or not exceeding 5 kHz, or not exceeding 1000 Hz, or not exceeding 500 Hz, or not exceeding 200 Hz, or not exceeding 100 Hz, or not exceeding 50 Hz.

7. The power filter circuit according to any one of claims 1 to 6 (100; 220; 400; 700; 800; 900; 1000). The control loops (474, 476, 478, 460; 774, 776, 762, 764, 766; 876, 874, 862, 864, 866; 974, 976, 962, 964, 966; 975; 1074, 1076) used to adjust the voltage across the load path of the transistors (120; 420; 720; 820; 920; 1020) or the voltage between the input terminal (110; 410; 710; 810; 910; 1010) and the output terminal (112; 412; 712; 812; 912; 1012) of the power filter circuit, are used to adjust the voltage between the input terminal (110; 410; 710; 810; 910; 1010) and the output terminal (112; 412; 712; 812; 912; 1012) of the power filter circuit. 1062, 1064, 1066) include low-pass filters (474; 774; 874; 974; 1074). The low-pass filter mentioned above has a cutoff frequency of less than or equal to 10 kHz, or The low-pass filter described therein has a cutoff frequency of less than or equal to 5 kHz, or The low-pass filter mentioned above has a cutoff frequency of less than or equal to 1000 Hz, or The low-pass filter described therein has a cutoff frequency of less than or equal to 500 Hz, or The low-pass filter mentioned above has a cutoff frequency of less than or equal to 200Hz, or The low-pass filter described therein has a cutoff frequency of less than or equal to 100 Hz.

8. The power filter circuit according to any one of claims 1 to 7 (100; 220; 400; 700; 800; 900; 1000). The power filter circuit is configured to provide a floating reference potential that is offset by a predetermined value relative to the output terminals (112; 412; 712; 812; 912; 1012) of the power filter circuit. The power filter circuit is configured to perform adjustment so that the potential at the terminal of the transistor (120; 420; 720; 820; 920; 1020) or the potential at the input terminal (110; 410; 710; 810; 910; 1010) of the power filter circuit is consistent with the floating reference potential; or The power filter circuit is configured to provide a floating reference potential that is offset by a predetermined value relative to the potential at the source terminal of the transistor (120; 420; 720; 820; 920; 1020), and The power filter circuit is configured to perform adjustment so that the potential at the terminal of the transistor or the potential at the input terminals (110; 410; 710; 810; 910; 1010) of the power filter circuit is consistent with the floating reference potential; or The power filter circuit is configured to provide a floating reference potential that is offset by a predetermined value relative to the potential at the input terminals (110; 410; 710; 810; 910; 1010) of the power filter circuit. The power filter circuit is configured to perform adjustment so that the potential at the source terminal of the transistor or the potential at the output terminal (112; 412; 712; 812; 912; 1012) of the power filter circuit is consistent with the floating reference potential; or The power supply filter circuit is configured to provide a floating reference potential that is offset by a predetermined value relative to the potential at the terminal of the transistor. The power filter circuit is configured to perform adjustment so that the potential at the source terminal of the transistor or the potential at the output terminal (112; 412; 712; 812; 912; 1012) of the power filter circuit is aligned with the floating reference potential.

9. The power filter circuit according to any one of claims 1 to 8 (100; 220; 400; 700; 800; 900; 1000). The power filter circuit includes a bypass path (922, 1022) connected in parallel with the load path of the transistors (120; 420; 720; 820; 920; 1020). The bypass path is configured to conduct when the voltage across the load path of the transistor exceeds a predetermined threshold voltage, and otherwise not conduct.

10. The power filter circuit according to any one of claims 1 to 9 (100; 220; 400; 700; 800; 900; 1000). The power filter circuit mentioned therein includes a low-pass resistor (974a), a low-pass capacitor (974b), an operational amplifier (962), an integrating capacitor (964), and an output resistor (965). The low-pass resistor is coupled between the terminal of the transistor (920) and the first terminal of the low-pass capacitor (974b). The second terminal of the low-pass capacitor (974b) is coupled to the reference potential conductor (GND). The first input terminal of the operational amplifier is coupled to the first terminal of the low-pass capacitor. The second terminal of the operational amplifier is coupled to the source terminal of the transistor via one or more resistors (966, 976d); The second terminal of the operational amplifier is coupled to the output terminal of the operational amplifier via a capacitor (964); The output terminal of the operational amplifier is coupled to the first terminal of the control capacitor (930) via the output resistor (965). The first terminal of the control capacitor (930) is coupled to the control terminal of the transistor (920). The second terminal of the control capacitor (930) is coupled to the reference potential conductor.

11. A power supply arrangement structure (200). The power supply arrangement includes a switching power converter (210), and The power supply arrangement structure includes a power filter circuit (100; 220; 400; 700; 800; 900; 1000) according to any one of claims 1 to 10. The output terminal (212) of the switching power converter (210) is coupled to the input terminal (222) of the power filter circuit.

12. The power supply arrangement structure (200) according to claim 11. The adjustment time constant of the adjustment loop used to adjust the voltage across the load path of the transistor or the voltage between the input terminal and the output terminal of the power filter circuit is at least 20 times, or at least 50 times, or at least 100 times, or at least 200 times, or at least 500 times, or at least 1000 times the cycle duration of the switching power converter.

13. The power supply arrangement structure (200) according to claim 11 or 12. The adjustment of the voltage across the load path of the transistor or the voltage between the input and output terminals of the power filter circuit is configured such that the adjustment does not adjust the change in the voltage across the load path of the transistor or the change in the voltage between the input and output terminals of the power filter circuit caused by the ripple voltage of the switching power converter by more than 50% [e.g., such that the voltage across the load path of the transistor follows the ripple voltage by at least 50%], or not more than 20% [e.g., such that the voltage across the load path of the transistor follows the ripple voltage by at least 80%], or not more than 10% [e.g., such that the voltage across the load path of the transistor follows the ripple voltage by at least 90%].

14. An automatic testing device (300). The automated test equipment includes a power supply arrangement (200) according to any one of claims 11 to 13. The automatic test equipment is configured to programmably change the voltage supplied by the switching power converter (210) to set the voltage at the output terminal (224) of the power filter circuit (220) to a desired value. The power filter circuit includes a fast-changing mechanism (922, 974c; 1022, 1074c, 1074d) configured to selectively bypass the load path of the transistor (920; 1020) and / or bypass the low-pass filter (974; 1074) in the regulation circuit (974, 976, 962, 964, 966, 975; 1074, 1076, 1062, 1064, 1066), the regulation circuit being used to regulate the voltage across the load path of the transistor (920; 1020) or to regulate the voltage between the input terminal (910; 1010) and the output terminal (912; 1012) of the power filter circuit.

15. A method for actively filtering a power supply voltage containing ripple using a power supply filter circuit. The power filter circuit mentioned above includes transistors, control capacitors, and stabilizing capacitors. The load path of the transistor is coupled between the input and output terminals of the power filter circuit. The control capacitor is coupled between the control terminal of the transistor and the reference potential conductor. The stabilizing capacitor is coupled between the source terminal of the transistor and the reference potential conductor. The method includes using the control capacitor to stabilize the potential difference between the control terminal of the transistor and the reference potential conductor, in order to suppress the generation of potential fluctuations at the control terminal of the transistor caused by the ripple on the power supply voltage applied at the input terminal of the power supply filter circuit; and The method includes adjusting the voltage across the load path of the transistor or the voltage between the input and output terminals of the power filter circuit using an adjustment time constant, wherein the time constant is at least 2, at least 5, at least 10, at least 20, at least 50, or at least 100 times the duration of the period of the ripple on the power supply voltage applied at the input terminal of the power filter circuit; and The output voltage is obtained at the output terminal of the power filter circuit.

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