Current sensor circuit with differential amplifier

Abstract

A current sensor circuit (100) includes a sense resistor (138) having a first node (143) adapted to be coupled to a high-side terminal (142) of a voltage supply and a second node (144) adapted to be coupled to a high-side terminal of a DUT (104) (device under test). A low-side terminal of the DUT (104) is coupled to a first ground node (154). The current sensor circuit (100) includes a differential amplifier (108) coupled to the first node (143) and the second node (144) of the sense resistor (138). A low-side supply terminal (130) of the differential amplifier (108) is coupled to a second ground node (134), and the second ground node (134) is coupled to the high-side terminal of the DUT (104). The current sensor circuit (100) also includes an isolated DC-DC converter (110) having an output coupled to a high-side supply terminal (126) of the differential amplifier (108).

Description

[0001] This specification relates to a circuit for sensing current, the circuit comprising a differential amplifier. Background Technology

[0002] A differential amplifier, also known as a differential voltage amplifier, is an electronic device that amplifies the difference between two input voltages while suppressing the common-mode voltage shared by the two inputs. A differential amplifier is used when the signal of interest is the voltage difference between two points, which can be superimposed on an uninterested common-mode voltage and should be reduced.

[0003] An operational amplifier (often called an op-amp) is a type of voltage amplifier designed to amplify the difference between two input voltage levels. Operational amplifiers typically have very high gain and are used in a variety of configurations depending on the application.

[0004] Connecting a sensing resistor in series with the circuit under test provides a direct method for measuring current using the basic principles of Ohm's Law. In this setup, the sensing resistor is directly inserted into the current path of the circuit under test. When current flows through this sensing resistor, due to the relationship defined by Ohm's Law (V=IR, where V is the voltage across the resistor, I is the current through the resistor, and R is the resistance), the voltage drop across the sensing resistor is proportional to the amount of current across the resistor and the current supplied to the circuit under test. By measuring this voltage drop and knowing the resistance of the sensing resistor, the current flowing through the circuit can be accurately calculated. Summary of the Invention

[0005] The first example relates to a current sensor circuit comprising a sensing resistor having a first node adapted to be coupled to a high-side terminal of a voltage power supply and a second node adapted to be coupled to a high-side terminal of a device under test (DUT). A low-side terminal of the DUT is coupled to a first ground node. The current sensor circuit includes a differential amplifier coupled to the first and second nodes of the sensing resistor. A low-side power supply terminal of the differential amplifier is coupled to a second ground node, and the second ground node is coupled to a high-side terminal of the DUT. The current sensor circuit also includes an isolated DC-DC converter having an output coupled to the high-side power supply terminal of the differential amplifier.

[0006] The second example relates to a current sensing circuit comprising a sensing resistor having a first node adapted to be coupled to a high-side terminal of a voltage supply and a second node adapted to be coupled to a high-side terminal of a device under test (DUT). A low-side terminal of the DUT is coupled to a first ground node. The current sensing circuit includes a differential amplifier coupled to the first and second nodes of the sensing resistor. A low-side power supply terminal of the differential amplifier is coupled to a second ground node that is current-isolated from the first ground node, and the second ground node is coupled to a high-side terminal of the DUT. The differential amplifier is configured to output a sense voltage that varies with the current across the sensing resistor. The current sensing circuit also includes an isolated DC-DC converter configured to provide an isolated voltage to the high-side power supply terminal of the differential amplifier.

[0007] A third example relates to a method for sensing current. The method includes sensing a voltage drop across a sense resistor by a differential amplifier. The sense resistor has a first node adapted to be coupled to a high-side terminal of a voltage power supply and a second node adapted to be coupled to a high-side terminal of a device under test (DUT). The low-side terminal of the DUT is coupled to a first ground node, the differential amplifier is coupled to the first and second nodes of the sense resistor, and the low-side power supply terminal of the differential amplifier is coupled to the second ground node. The second ground node is coupled to the high-side terminal of the DUT. The method further includes outputting a sense voltage by the differential amplifier in response to receiving an isolation voltage from an isolated DC-DC converter at the high-side power supply terminal of the differential amplifier. The sense voltage varies with the current across the sense resistor. Attached Figure Description

[0008] Figure 1 An example of a current sensor circuit for sensing the current supplied to the DUT (Device Under Test) is shown.

[0009] Figure 2 An example of a circuit including a current sensor circuit is shown, which measures the current supplied to the DUT based on a voltage provided by a high-voltage power supply.

[0010] Figure 3 It shows what can be used for implementation Figure 2 The IC (integrated circuit) package level circuit of the circuit.

[0011] Figure 4 A graph showing the measurement results from the implemented circuit is presented.

[0012] Figure 5 This is a flowchart of an example method for sensing current. Detailed Implementation

[0013] This specification relates to a circuit for measuring current by measuring the voltage drop across a sensing resistor connected to a DUT (Device Under Test). Conventional methods for measuring current present significant challenges when the common-mode voltage between resistor terminals is high, particularly in applications exceeding 400 volts (V). Standard circuit components such as transistors and operational amplifiers (OPAs) are not designed to handle such high common-mode voltages.

[0014] This specification provides a current sensor circuit capable of accurately measuring current at virtually any voltage, including high-voltage applications potentially reaching and exceeding 2000 volts. The current sensor circuit employs an isolated power supply for differential amplifiers implemented with operational amplifiers, allowing the operational amplifier to operate without exposure to high common-mode voltages. The current sensor circuit features separate ground references for the DUT and the differential amplifier, effectively isolating the differential amplifier components from high common-mode voltages.

[0015] The current sensor circuit includes a sensing resistor, a differential amplifier, and an isolated DC-DC converter. The sensing resistor is connected in series with the DUT (device under test), and the differential amplifier is configured to measure the voltage drop across this resistor. The isolated DC-DC converter provides an isolation voltage to the high-side power supply terminal of the differential amplifier, ensuring that the differential amplifier operates within common-mode voltage limits.

[0016] Additionally, in some examples, the current sensor circuitry includes an isolated ADC (analog-to-digital converter) to digitize the sensed voltage, allowing for digital processing and readout. In some examples, the isolated ADC and differential amplifier are implemented on a first IC (integrated circuit) package, and the isolated DC-DC converter may be implemented on a second IC package, further enhancing the isolation between the high-voltage and low-voltage sides of the circuitry. The current sensor circuitry measures current at high voltages without the limitations of conventional methods, making this approach suitable for applications such as high-voltage electric vehicles and other high-voltage systems requiring precise current measurement.

[0017] Figure 1 An example of a current sensor circuit 100 for sensing the current supplied to a DUT 104 is shown. The DUT 104 represents a load having an on-state and an off-state. For simplicity, it is assumed that in the on-state, the DUT current I supplied to the DUT 104 is... DUT At its maximum level. Conversely, in the off state, the DUT current I supplied to DUT 104 is... DUT Limit the leakage current I of DUT 104 LEAK Typically, leakage current should be reduced. However, for high-voltage applications, due to the high common-mode voltage Vo of conventional current measuring devices... CM It may be difficult to accurately measure the leakage current I of the DUT 104.LEAK However, the current sensor circuit 100 is configured to ensure the common-mode voltage V CM The voltage is approximately 5 volts (V) or less, making standard and accurate circuitry available for measuring the DUT current I supplied to the DUT 104 in both on and off states. DUT .

[0018] The current sensor circuit 100 includes a differential amplifier 108 and an isolated DC-DC converter 110 (labeled ISO DC-DC). In some examples, the differential amplifier 108 is implemented using an operational amplifier configured for differential amplification. The differential amplifier 108 includes a non-inverting input 112 (e.g., a first input) and an inverting input 116 (e.g., a second input). The non-inverting input 112 is coupled to a first node 120, and the inverting input 116 is coupled to a second node 124. The high-side power supply terminal 126 of the differential amplifier 108 is coupled to the output of the isolated DC-DC converter 110. The isolated DC-DC converter 110 is also coupled to a first ground node 128, GND1. The low-side power supply terminal 130 of the differential amplifier 108 is coupled to a second ground node 134, GND2. The inverting input 116 of the differential amplifier 108 and the isolated DC-DC converter 110 are also coupled to the second ground node 134. The first ground node 128 and the second ground node 134 are electrically isolated from each other.

[0019] The current sensor circuit 100 includes a sensing resistor 138, R I-SNS The sensing resistor 138 has a relatively small resistance, for example, about 10 milliohms (mΩ) or less. The sensing resistor 138 is coupled to a first node 120 and a second node 124. Additionally, the high-side terminal of the DUT 104 is coupled to the second node 124. The second node 124 is adapted to be coupled to the high-side terminal 142 (e.g., an output terminal) of a voltage supply (not shown), such that the sensing resistor 138 is adapted to be coupled to the high-side terminal 142 of the voltage supply. More specifically, the sensing resistor 138 has a first node 143 coupled to the first node 120, and the first node 143 is adapted to be coupled to the high-side terminal 142. The sensing resistor 138 also has a second node 144 coupled to the second node 124, and the second node 144 is adapted to be coupled to the high-side terminal of the DUT 104. In this way, the sensing resistor 138 is connected in series with the DUT 104 due to the high input impedance of the non-inverting input 112 and the inverting input 116 of the differential amplifier 108.

[0020] The low-side terminal of DUT 104 is coupled to the third ground node 154, GND3. The third ground node 154 is current-isolated from the second ground node 134 and the first ground node 128. In addition, as shown, the high-side terminal of DUT 104 is coupled to the second ground node 134 (and the second node 124).

[0021] During operation, the voltage supply outputs a voltage at the high-side terminal 142. Additionally, the isolated DC-DC converter 110 outputs an isolated voltage V. SIO The output is to the high-side power supply terminal 126 of the differential amplifier 108. The voltage supplied at the high-side terminal 142 can be virtually any voltage. Specifically, the voltage at the high-side terminal 142 is a DC voltage and can be a high voltage ranging from approximately 400 volts (V) to approximately 2000 V (or even exceeding 2000 V in some examples). The voltage at the high-side terminal 142 induces a DUT current I. DUT Differential amplifier 108 is configured to measure the voltage drop across sensing resistor 138 and output the sensed voltage V. SNS The sensing voltage V SNS The current across the sensing resistor 138 varies, and this current corresponds to the DUT current I. DUT .

[0022] As mentioned above, the DUT current I DUT The current flows to the third ground node 154. Additionally, because the inverting input 116 is coupled to the second ground node 134, and the second and third ground nodes 154 are individually grounded (current isolated), the common-mode voltage between the non-inverting input 112 and the inverting input 116 is approximately 5 V or less relative to the differential amplifier 108 and the second ground node 134, making it possible to use standard components such as operational amplifiers to implement the differential amplifier 108.

[0023] By using the current sensor circuit 100, the DUT current I DUT It is accurately measured, especially for voltages of 400 V or higher, without requiring high-voltage components for the differential amplifier 108. Furthermore, the current sensor circuit 100 measures the leakage current supplied to the DUT 104 in both on and off states.

[0024] Figure 2 An example of circuit 200 is shown, which includes a current sensor circuit 204 that measures the current supplied to DUT 208 based on a voltage provided by a high-voltage power supply 210. DUT 208 may represent a load, such as a test circuit or test IC package driven by the high-voltage power supply 210. DUT 208 has an on state and an off state. For simplicity, it is assumed that in the on state, the DUT current I supplied to DUT 208 is... DUTAt its maximum level. Conversely, in the off state, the DUT current I supplied to DUT 208 is... DUT Limit the leakage current I of DUT 208 LEAK Typically, leakage current should be reduced. However, for high-voltage applications, due to the high common-mode voltage Vo of conventional current measuring devices... CM It may be difficult to accurately measure the leakage current I of the DUT 208. LEAK However, the current sensor circuit 204 is configured to ensure the common-mode voltage V CM The components of the current sensor circuit 204 are approximately 5 volts (V) or less, making standard and accurate circuit components available for measuring the DUT current I supplied to the DUT 208 in both on and off states. DUT .

[0025] The current sensor circuit 204 can be used to implement Figure 1 The current sensor circuit 100. The current sensor circuit 204 includes components that can be used to implement... Figure 1 The differential amplifier 108 includes a differential amplifier 212. The current sensor circuit 204 also includes components that can be used to implement... Figure 1 The isolated DC-DC converter 110 and the isolated DC-DC converter 216 (marked as ISO DC-DC) are included. The current sensor circuit 204 also includes an isolated ADC 220 (analog-to-digital converter, marked as ISO ADC).

[0026] The current sensor circuit 100 includes dashed lines 224 to indicate the tester side and the high-voltage side. In the example shown, the voltage input and output on the tester side are less than approximately 20 V. Additionally, the voltage input and output on the high-voltage side can be any voltage, including at least approximately 400 V or higher (including 2000 V or higher). Components such as the isolated DC-DC converter 216, the isolated ADC 220, and the high-voltage power supply 210 provide the interface between the tester side and the high-voltage side.

[0027] The isolated DC-DC converter 216 is coupled to a first ground node 232 GND1 and a second ground node 236 GND2. In some examples, the high-voltage power supply 210 is coupled to the first ground node 232 and a third ground node 240 GND3. In other examples, the high-voltage power supply 210 is not coupled to the first ground node 232 and is coupled to the third ground node 240 (e.g., the high-voltage power supply 210 is not an isolated voltage supply). The first ground node 232, the second ground node 236, and the third ground node 240 are current-isolated from each other.

[0028] High-voltage power supply 210 is coupled to a first input voltage V supplied from a DC power supply (not shown). IN1 In some examples, the first input voltage VIN1 The voltage is approximately 12 V or less. The isolated DC-DC converter 216 and the isolated ADC 220 are coupled to a second input voltage V supplied from a DC power supply (not shown). IN2 Second input voltage V IN2 The voltage ranges from approximately 3 V to approximately 12 V (e.g., approximately 5 V in some examples). The isolated DC-DC converter 216 outputs an isolation voltage V that is approximately 5 V higher than the second ground node 236. ISO This results in an output isolation voltage V relative to the second ground node 236. ISO Isolation voltage V ISO The output is fed to differential amplifier 212 and isolated ADC 220.

[0029] High-voltage power supply 210 outputs high voltage (V) OUT-HV The output is sent to the high-side terminal 244 of the current sensor circuit 204. The high-side terminal 244 of the current sensor circuit 204 is coupled to the first node 248 of the current sensor circuit 204. The first node 248 of the current sensor circuit 204 is coupled to the sensing resistor 252, R. I-SNS The sensing resistor 252 has a resistance of approximately 10 mΩ or less. The sensing resistor 252 is also coupled to a second node 256 of the current sensor circuit 204. The second node 256 is coupled to a second ground node 236 via a low-side terminal 246 of the current sensor circuit 204 and to a high-side terminal of the DUT 208. The low-side terminal of the DUT 208 is coupled to a third ground node 240.

[0030] The differential amplifier 212 has a first input 260 (e.g., a non-inverting input) coupled to a first node 248 and a second input 264 (e.g., an inverting input) coupled to a second node 256. The first input 260 can be used to implement... Figure 1 The non-inverting input 112 of the differential amplifier 108. Similarly, the second input 264 can be used to implement... Figure 1 The inverting input 116 of the differential amplifier 108. The differential amplifier 212 is implemented using an operational amplifier 268 arranged in a differential configuration. The high-side power supply terminal of the operational amplifier 268 receives an isolation voltage V from the isolated DC-DC converter 216. ISO The low-side power supply terminal of operational amplifier 268 is coupled to the second ground node 236. Due to the high input impedance of the non-inverting and inverting inputs of operational amplifier 268, sense resistor 252 is connected in series with DUT 208.

[0031] The first input 260 of differential amplifier 212 is coupled to the second resistor 272, R2. The second resistor 272 is also coupled to the non-inverting input of operational amplifier 268. The non-inverting input of operational amplifier 268 is also coupled to the third resistor 276, R3. The third resistor 276 is also coupled to the second ground node 236, GND2. The second resistor 272 and the third resistor 276 have a resistance of approximately 1 kiloohm (kΩ).

[0032] The second input 264 of differential amplifier 212 is coupled to a fourth resistor 280, R4, and a second ground node 236. The fourth resistor 280 is also coupled to the inverting input of operational amplifier 268 and to a fifth resistor 282, R5. The fifth resistor 282 is also coupled to the output of operational amplifier 268, making it a feedback resistor for operational amplifier 268. The fourth resistor 280 and the fifth resistor 282 have a resistance of approximately 1 kΩ. That is, the second resistor 272, the third resistor 276, the fourth resistor 280, and the fifth resistor 282 have the same resistance.

[0033] During operation, the high-voltage power supply 210 outputs a high-voltage output V at the high-side terminal 244 of the current sensor circuit 204. OUT-HV V OUT-HV It is DC voltage. High voltage output V OUT-HV It is a voltage greater than approximately 400 V. In some examples, V OUT-HV This is approximately 2000 V or higher. This high-voltage output V OUT-HV The DUT current I supplied to DUT 208 is induced. DUT Differential amplifier 212 is configured to measure the voltage drop across sensing resistor 252, the voltage drop corresponding to the DUT current I. DUT And output sensing voltage V SNS The sensing voltage V SNS It varies with the current across the sensing resistor 252 and corresponds to the DUT current I. DUT The isolated ADC 220 receives the sensed voltage V. SNS And output the encoded digital signal ADC on the tester side. OUT The value on, the value representing the sensed voltage V SNS The voltage. Digital signal ADC OUT It is provided to external systems.

[0034] Because the operational amplifier 268 is isolated by the voltage V output from the isolated DC-DC converter 216. ISOPower is supplied so that operational amplifier 268 floats relative to the ground point of DUT 208, i.e., relative to the third ground node 240. This indicates that the ground point of operational amplifier 268, i.e., the second ground node 236, is not directly connected to the ground reference of DUT 208 (third ground node 240). Instead, operational amplifier 268 operates with an independent or isolated ground reference, the second ground node 236, which may be at a different potential than the third ground node 240. This configuration allows operational amplifier 268 to operate normally in environments with high common-mode voltages because it prevents the high voltage present at DUT 208 from affecting the operation of operational amplifier 268.

[0035] More specifically, as shown in current sensor circuit 100, sensing resistor 252 is coupled to a second node 256 of current sensor circuit 204, which is coupled to the high-side terminal of DUT 208 and a second ground node 236. In other words, the DUT side of sensing resistor 252 is shorted to the second ground node 236, GND2.

[0036] The current sensor circuit 204 is configured such that the voltage at the first node 248 of the current sensor circuit 204 is relative to the third ground node 240. equal And the voltage at the second node 256 of the current sensor circuit 204 Determine using Equation 1:

[0037] Equation 1:

[0038] in:

[0039] It is the resistance of the sensing resistor (e.g., about 10 mΩ in some examples).

[0040] It is the leakage current of the DUT, which is limited to the current to the DUT during the time interval when the DUT is in the off state.

[0041] Therefore, relative to the third ground node 240, the differential voltage V across the sensing resistor 252 DIFF-GND3 Defined by Equation 2, and the common-mode voltage V CM-GND3 Defined by Equation 3.

[0042] Equation 2:

[0043] Equation 3:

[0044] However, as described above, the differential amplifier 212 avoids a relatively high common-mode voltage by shorting the DUT side (e.g., second node 256) of the sensing resistor 252 to the high-side terminal of the DUT 208. This creates two separate grounds: a second ground node 236 and a third ground node 240. Therefore, the voltage difference across the sensing resistor 252 relative to the second ground node 236 and the operational amplifier 268... Defined by Equation 4, and the common-mode voltage Defined by Equation 5.

[0045] Equation 4:

[0046] Equation 5:

[0047] Therefore, although the common-mode voltage relative to the third ground node 240 is approximately equal to the voltage at the high-side terminal 244. However, the operational amplifier 268 can be measured relative to the second ground node 236, so that the common-mode voltage of the operational amplifier 268 is... Less than approximately 5 V. This avoids the need for relatively high common-mode rejection errors in the components of differential amplifier 212 (including operational amplifier 268). Therefore, current sensor circuit 204 provides an isolated current sensing solution that can be safely used with other low-voltage circuits, such as other circuits on the tester side.

[0048] Figure 3 It shows what can be used for implementation Figure 1 The IC package-level circuit 300 of circuit 200 includes a high-voltage power supply 304, which can be used to implement... Figure 2 The high-voltage power supply 210. The IC package-level circuit 300 includes a current sensor circuit 308. The current sensor circuit 308 measures the DUT current I supplied to the DUT 310. DUT .

[0049] In some examples, the high-voltage power supply 304 is implemented on an IC package. Similarly, in some examples, the DUT 310 is implemented on an IC package. The DUT 310 has an on state and an off state; in the on state, the DUT current I... DUT At its peak, in the off state, the DUT current I supplied to DUT 310 is DUT It is the leakage current I LEAK .

[0050] The current sensor circuit 308 comprises two IC packages: a first IC package 312 and a second IC package 316. The first IC package 312 includes a differential amplifier 320 and an isolated ADC 324 (labeled ISO ADC). The differential amplifier 320 can be used to implement... Figure 2 Differential amplifier 212 and / or Figure 1 The differential amplifier 108. Therefore, the differential amplifier 320 includes operational amplifiers (e.g., ) configured in a differential configuration. Figure 2 The operational amplifier 268). The second IC package 316 contains components that can be used to implement... Figure 2 The isolated ADC 220 is an isolated DC-DC converter 328 (marked as ISO DC-DC). The current sensor circuit 308 also includes a sensing resistor 332, R I-SNS It can be used for implementation Figure 2 The sensing resistor 252 makes the sensing resistor 332 have a resistance of about 10 mΩ.

[0051] The IC package-level circuit 300 includes a dashed line 336, the dashed line being aligned with... Figure 2 The dashed line 224 represents the test side and high voltage side of the IC package-level circuit 300 in the same way.

[0052] In some examples, the high-voltage power supply 304 is adapted to couple to the first input voltage V. IN1 And the first ground node 340. In some examples, the first input voltage V IN1 It is approximately 12 V or less of DC voltage. The isolated ADC 324 and isolated DC-DC converter 328 are adapted to couple to a second input voltage V. IN2 And the first ground node 340. In some examples, the second input voltage V IN2 It is a DC voltage of approximately 3V to approximately 12V (e.g., approximately 5V).

[0053] In response to the second input voltage V IN2 The isolated DC-DC converter 328 outputs an isolation voltage V that is approximately 5 V higher than the voltage GND2 at the second ground node 344. ISO Isolation voltage V ISO The output is given to the high-voltage terminals of differential amplifier 320 and isolated ADC 324. The low-voltage terminals of differential amplifier 320 and isolated ADC 324 are coupled to the second ground node 344. Similarly, in response to the first input voltage V... IN1 The high-voltage power supply 304 will output high voltage V. OUT-HV The output is sent to the high-side terminal 348 of the current sensor circuit 308. High-voltage output V OUT-HVThis is a DC voltage of approximately 400 V to approximately 2000 V or higher relative to the third ground node 350 GND3. Furthermore, in some examples, such as when the high-voltage power supply 304 is not an isolated voltage power supply, the high-voltage power supply 304 is not coupled to the first ground node 340 but is coupled to the third ground node 350.

[0054] The low-side terminal 352 of the current sensor circuit 308 is coupled to the high-side terminal of the DUT 310. The DUT 310 is also coupled to the third ground node 350. The first ground node 340, the second ground node 344, and the third ground node 350 are current-isolated from each other. Due to the high input impedance of the first input 356 and the second input 362 of the differential amplifier 320, the sensing resistor 332 is connected in series with the DUT 310.

[0055] The high-side terminal 348 is also coupled to a first node 354 of the current sensor circuit 308. The first node 354 of the sensor circuit is coupled to a first input 356 (e.g., a non-inverting input) of the differential amplifier 320 and a sensing resistor 332. The low-side terminal 352 is coupled to a second node 358 of the current sensor circuit 308. This second node 358 is also coupled to a second ground node 344, the sensing resistor 332, and a second input 362 (e.g., an inverting input) of the differential amplifier 320. The first input 356 of the differential amplifier 320 can be used to implement... Figure 2 The first input 260 of the differential amplifier 212, and the second input 362, can be used to implement... Figure 2 The second input 264 of the differential amplifier 212.

[0056] IC package-level circuitry 300 and Figure 2 The circuit 200 operates in the same manner. Therefore, the high-voltage power supply 304 will output voltage V. OUT-HV An application is made to the high-side terminal 348 of the current sensor circuit 308, which senses the DUT current I for the DUT 310. DUT Differential amplifier 320 measures the voltage drop across sensing resistor 332 and outputs the sensed voltage V. SNS The sensing voltage V SNS It varies with the current across the first ground node 232 and corresponds to the DUT current I. DUT (And it varies with the voltage drop across the sensing resistor 332). Sensing voltage V SNS The output is sent to an isolated ADC 324, which in turn outputs a signal characterizing the sensed voltage V. SNS Digital signal ADC OUT The encoded digital value. Therefore, in ADC OUT The coded digital value also represents the current reaching the DUT 310.

[0057] As described above, DUT 310 has an ON state, where it is assumed that the DUT current I DUT It is at its maximum value. Furthermore, DUT310 has an off state, where the DUT current I supplied to DUT310 is at its maximum value. DUT Equal to leakage current I LEAK Furthermore, as mentioned above, the output voltage It is a DC voltage of approximately 400 V to 2000 V or higher, including the output voltage. For example, the common-mode voltage is approximately 1500 V. Therefore, relative to the third ground node 350, the common-mode voltage V is... CM-GND3 For the agreement As shown in Equation 3. However, because the differential amplifier 320 uses the second ground node 344 as a reference and the differential amplifier 320 is isolated by voltage V... ISO The power supply is used to measure the common-mode voltage for the differential amplifier 320 relative to the voltage at the second ground node 344. Therefore, as characterized in Equation 5, the common-mode voltage V relative to the second ground node 344 is... CM-GND2 The voltage is approximately 5 V or less. Therefore, the differential amplifier 320 can be implemented using a standard operational amplifier arranged in a differential configuration, such as... Figure 2 As shown.

[0058] Figure 4 It shows that it has from, for example Figure 2 Circuit 200 and / or Figure 3 A graph 400 shows the measurement results of the implemented circuitry of the IC package-level circuitry 300. Graph 400 includes the ratio of the high-voltage output (VHV) and common-mode voltage (VCM) for the third ground node (GND3). This value may correspond, for example, to... Figure 2 High voltage power supply 210 and / or Figure 3 The output voltage of the high-voltage power supply 304. Figure 400 also plots the voltage reaching, for example... Figure 2 DUT 208 and / or Figure 1 The measured current (in microamps (μA)) of the DUT 310. The graphs include, for example... Figure 1 Current sensor circuit 100 Figure 2 The current sensor circuit 204 and / or Figure 3 The current sensor circuit 308 measures the current in μA. Figure 400 also includes the current measurement error of the current sensor circuit in μA. As shown, the current measurement error for each recorded output voltage is less than 0.9 μA. Therefore, Figure 400 illustrates the measurement error of the current sensor circuit 100. Figure 2 The current sensor circuit 204 and / or Figure 3The current sensor circuit 308 can be used in situations where there is a high common-mode voltage.

[0059] Figure 5 This is a flowchart of an example method 500 for sensing current. In some examples, method 500 utilizes... Figure 1 The current sensor circuit 100 and / or Figure 2 The current sensor circuit 204 is used for implementation. At block 510, a differential amplifier (e.g., Figure 1 The differential amplifier 108) senses the sensing resistor (e.g., Figure 1 The voltage drop across the sensing resistor 138, which has a high-side terminal suitable for coupling to a voltage power supply (e.g., Figure 1 The first node of the high-side terminal 142) (e.g., Figure 1 The first node 143) and suitable for coupling to the DUT (e.g., Figure 1 The second node of the high-side terminal of the DUT 104 (e.g., Figure 1 The second node 144). The low-side terminal of the DUT is coupled to the first ground node (e.g., Figure 1 The third ground node 154), and the differential amplifier is coupled to the first and second nodes of the sensing resistor. The low-side power supply terminal of the differential amplifier is coupled to the second ground node (e.g., Figure 1 The second ground node (134) is coupled to the high-side terminal of the DUT. The first ground node and the second ground node are current isolated.

[0060] At box 515, the differential amplifier responds to the high-side power supply terminal of the differential amplifier (e.g., Figure 1 The high-side power supply terminal 126 receives power from an isolated DC-DC converter (e.g., Figure 1 The isolated DC-DC converter 110 provides an isolation voltage to output a sense voltage, which varies with the current across the sense resistor.

[0061] At box 520, the ADC (e.g., Figure 2 The isolated ADC 220 receives the sensed voltage from the differential amplifier. At box 525, the isolated ADC outputs a digital value characterizing the current across the sense resistor.

[0062] In this specification, unless otherwise stated, "about" preceding a parameter means within + / - 10% of said parameter. Modifications to the described embodiments are possible within the scope of the claims, and other embodiments are also possible.

Claims

1. A current sensor circuit, comprising: A sensing resistor having a first node adapted to be coupled to a high-side terminal of a voltage power supply and a second node adapted to be coupled to a high-side terminal of a DUT (device under test), wherein the low-side terminal of the DUT is coupled to a first ground node; A differential amplifier coupled to the first and second nodes of the sensing resistor, wherein the low-side power supply terminal of the differential amplifier is coupled to the second ground node, and the second ground node is coupled to the high-side terminal of the DUT; as well as An isolated DC-DC converter having an output coupled to the high-side power supply terminal of the differential amplifier.

2. The current sensor circuit according to claim 1, wherein the first ground node and the second ground node are current isolated.

3. The current sensor circuit of claim 1, wherein the isolated DC-DC converter is coupled to a third ground node that is current-isolated from the first ground node and the second ground node.

4. The current sensor circuit according to claim 3 further includes an isolated ADC (analog-to-digital converter) coupled to the output of the differential amplifier.

5. The current sensor circuit of claim 4, wherein the isolated ADC and the differential amplifier are implemented on a first IC (integrated circuit) package, and the isolated DC-DC converter is implemented on a second IC package.

6. The current sensor circuit of claim 5, wherein the differential amplifier is configured to provide a sensing voltage at the output of the differential amplifier, the sensing voltage varying with the current across the sensing resistor.

7. The current sensor circuit of claim 6, wherein the isolated ADC is configured to output a digital value characterizing the current across the sensing resistor.

8. The current sensor circuit of claim 4, wherein the isolated ADC is coupled to the third ground node.

9. The current sensor circuit of claim 2, wherein the differential amplifier is configured to output a sense voltage that varies with the current across the sense resistor.

10. The current sensor circuit of claim 2, wherein the voltage power supply is configured to supply a voltage of at least 400 volts on the high-side terminal of the voltage power supply.

11. The current sensor circuit of claim 10, wherein there is a voltage drop of about 5 volts or less between the first node and the second node.

12. The current sensor circuit of claim 2, wherein the voltage power supply is configured to supply a voltage of at least 1500 volts on the high-side terminal of the voltage power supply.

13. A current sensor circuit, comprising: A sensing resistor having a first node adapted to be coupled to a high-side terminal of a voltage power supply and a second node adapted to be coupled to a high-side terminal of a DUT (device under test), wherein the low-side terminal of the DUT is coupled to a first ground node; A differential amplifier coupled to the first and second nodes of the sensing resistor, wherein the low-side power supply terminal of the differential amplifier is coupled to a second ground node that is current-isolated from the first ground node, and the second ground node is coupled to the high-side terminal of the DUT, the differential amplifier being configured to output a sense voltage that varies with the current across the sensing resistor; as well as An isolated DC-DC converter configured to provide an isolation voltage to the high-side power supply terminal of the differential amplifier.

14. The current sensor circuit according to claim 13, wherein the first ground node and the second ground node have a potential difference.

15. The current sensor circuit of claim 14, wherein the isolated DC-DC converter is coupled to a third ground node that is current-isolated from the first ground node and the second ground node.

16. The current sensor circuit of claim 14, further comprising an isolated ADC (analog-to-digital converter) configured to receive the sensed voltage from the differential amplifier and output a digital value characterizing the current across the sense resistor.

17. The current sensor circuit of claim 14, wherein the voltage power supply is configured to supply at least 400 volts on the high-side terminal of the voltage power supply, and there is a voltage drop of about 5 volts or less between the first node and the second node.

18. A method for sensing current, the method comprising: A differential amplifier senses the voltage drop across a sensing resistor, the sensing resistor having a first node adapted to be coupled to a high-side terminal of a voltage power supply and a second node adapted to be coupled to a high-side terminal of a DUT (Device Under Test), wherein the low-side terminal of the DUT is coupled to a first ground node, the differential amplifier is coupled to the first and second nodes of the sensing resistor, and the low-side power supply terminal of the differential amplifier is coupled to a second ground node, and the second ground node is coupled to the high-side terminal of the DUT; as well as In response to receiving an isolation voltage from an isolated DC-DC converter at the high-side power supply terminal of the differential amplifier, the differential amplifier outputs a sense voltage that varies with the current across the sense resistor.

19. The method of claim 18, wherein the first ground node and the second ground node are electrically isolated.

20. The method of claim 19, further comprising: The sensed voltage is received from the differential amplifier at the isolated ADC (analog-to-digital converter); as well as The isolated ADC outputs a digital value representing the current across the sensing resistor.

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