Bidirectional high-speed current tracking and draining system

Abstract

Current tracking sensing system (300; 400; 500), which includes the following: a first current tracking system configured to replicate a first current flowing through a first switch (132; 402); a second current tracking system configured to replicate a second current flowing through a second switch (134; 430); and a preloading device comprising at least one comparator (306; 406), wherein the preloading device is configured as follows: to bias the second current tracking system based on initial information detected by the first current tracking system, which indicates the initial current; and The first current tracking system is biased based on second information detected at the second current tracking system, which indicates the second current.

Description

[0001] This disclosure generally relates to current sense techniques in electronic circuit arrangements.

[0002] A tracking current sense circuit typically provides a tracking current and can be used in applications such as DC-DC converters for use in servers and mobile computers. Conventional tracking current sense circuits often include an operational amplifier, which, due to capacitances introduced for stability, has a limited slew rate and bandwidth. The use of an operational amplifier results in the tracking current sense circuit having a low threshold speed and thus may not be able to act as a sink or source of current at the speeds sometimes required by modern technologies / systems. An objective of the present invention is to provide an improved current sense technique and system.This objective is achieved by the system according to claims 1 and 20 and the method according to claim 11. Various embodiments and further developments are covered by the dependent claims.

[0003] Publication US 6,642,752 B1 discloses a sample-and-hold circuit with a first current source that interacts with a first current mirror to supply current to a sampling capacitor, and with a second current source that interacts with a second current mirror to draw current from the sampling capacitor. Publication US 2014 / 0266,832 A1 discloses a DC converter.

[0004] In general, this disclosure describes techniques and circuits for improving the speed, bandwidth, and stability of tracking current sense systems. Some of the techniques and circuits described here enable a tracking current sense system to bias the current of an inactive side of a half-bridge so that the level of the current at the inactive side is at or near the level of an operating current of the half-bridge when the inactive side of the half-bridge subsequently becomes active. In this way, biasing the inactive side of a half-bridge can reduce the amount of settling time that occurs when one side of the half-bridge is activated.

[0005] Some of the techniques and circuits described here can enable a current tracking sensing system to track both positive and negative currents. This can be achieved, for example, by using a current zero-crossing comparator to detect a change in the polarity of a current, or by using an offset current generator set to supply the maximum negative current that might be required.

[0006] Some of the techniques and circuits described here allow a current tracking sensing system to track positive and negative currents regardless of which side of the half-bridge is active. As such, the current tracking system can track positive and negative currents in both the high-side and low-side switches of the half-bridge.

[0007] In some examples, the techniques described in this disclosure are directed to a current tracking system comprising: a first current tracking system configured to replicate a first current flowing through a first switch; a second current tracking system configured to replicate a second current flowing through a second switch; and a biasing device. The biasing device has at least one comparator and is configured to: bias the second current tracking system based on first information detected at the first current tracking system indicating the first current; and bias the first current tracking system based on second information detected at the second current tracking system indicating the second current.

[0008] In some examples, the techniques of disclosure are directed to a method that includes receiving at a biasing device information detected by a first current tracking system, indicating a first current flowing through a first switch. The biasing device includes at least one comparator. The method further includes biasing by the biasing device, based on information from a second current tracking system configured to replicate a second current flowing through a second switch.

[0009] In some examples, the techniques of revelation are directed toward a current-tracking sensing system that includes means for replicating a first current flowing through a first switch and means for replicating a second current flowing through a second switch. The current-tracking sensing system further includes means for biasing the second current-tracking system based on first information received from the first current-tracking system specifying the first current, and means for biasing the first current-tracking system based on second information received from the second current-tracking system specifying the second current.

[0010] The details of one or more examples and techniques of this disclosure are set forth in the accompanying drawings and the description below. Other features, objectives, and advantages of the disclosure will become apparent from the description, the drawings, and the claims. The means for biasing the first current tracking system and the means for biasing the second current tracking system comprise means for comparing two voltages. Fig. Figure 1 is a schematic diagram representing an example current tracking sensing system in accordance with one or more techniques described in this disclosure. Fig. 2 is a time diagram showing an example of the behavior of the feedback current in the current tracking system of Fig. 1 in accordance with one or more techniques described in this disclosure. Fig. Figure 3 is a graphical representation showing an example difference between gain-bandwidth products of an operational amplifier and a comparator in a closed-loop current sense system in accordance with one or more techniques described in this disclosure. Fig. Figure 4 is a schematic diagram showing an example implementation of the current tracking sensing system of Fig. 1 in accordance with one or more techniques described in this disclosure. Fig. Figure 5 is a schematic diagram illustrating an example current follower used in an example current tracking sensing system configured to track positive current in accordance with one or more techniques described in this disclosure. Fig. Figure 6 is a schematic diagram illustrating an example current tracking sensing system for use with a half-bridge in accordance with one or more techniques described in this disclosure. Fig. Figures 7A-7C are timing diagrams that represent example currents in different current tracking sensing systems in accordance with one or more techniques described in this disclosure. Fig. Figure 8 is a schematic diagram illustrating an alternative example current tracking sensing system configured to track positive and negative currents flowing in both sides of a half-bridge in accordance with one or more techniques described in this disclosure. Fig. Figure 9 is a flowchart that presents an example process for operating a current tracking sensing system configured to track positive and negative currents flowing in both sides of a half-bridge in accordance with one or more techniques described in this disclosure. Fig. Figure 10 is a schematic diagram illustrating an example current tracking sensing system configured to detect zero crossings of current in a half-bridge in accordance with one or more techniques described in this disclosure. Fig. 11A and Fig. Figure 11B are schematic diagrams that represent active current mirrors for use in an example current tracking sensing system in accordance with one or more techniques described in this disclosure. Fig. 12 is a flowchart that presents an example process for operating a current tracking sensing system that has bidirectional sensing in accordance with one or more techniques described in this disclosure.

[0011] The drawings are not necessarily drawn to scale. The same reference symbols indicate the same features, although variations between the same features may exist in the different examples.

[0012] Some power supply systems rely on linear sense amplifier (LSA)-based current sensing systems to perform current tracking techniques. A disadvantage of LSA-based current sensing systems is that an LSA can be unsuitable for high-speed power supply systems. That is, some LSA-based current sensing systems may exhibit a "residual offset" (e.g., a period of time after sensing operations that requires the entire system to wait before proceeding with other non-sensing operations) and / or large settling times. Some power supply systems (e.g., buck converters) perform rapid switching and / or high / low power duty cycle operations and have very little time for an LSA-based current sensing system to perform current tracking techniques.Accordingly, LSA-based current sensing systems exhibiting residual offset and / or large settling times may fail to settle and / or complete sensing operations within the allotted time available to the power supply system. Even if an LSA-based current sensing system does settle or complete sensing operations within the allotted time, it may still be inadequate for power supply systems for other reasons (e.g., when using an average current value). Techniques and circuits are described to improve the speed of the current tracking sensing system in a power supply system (e.g., a DC-DC converter, etc.).This means that the techniques and circuits described here can reduce the overall time that a power supply system must allocate to a current tracking sensing system to perform current tracking operations. In some examples, the techniques and circuits can enable a current tracking sensing system to track both positive and negative currents, and in some examples, the techniques and circuits can enable the current tracking sensing system to track positive and negative currents regardless of the location of the current (e.g., high side or low side) within the power supply system.

[0013] Fig. Figure 1 is a schematic diagram illustrating an example current tracking system 10 in accordance with one or more techniques described in this disclosure. The current tracking system 10 is a nonlinear system that relies on the comparator 12 to ensure that the two "tuned" transistors 18-2 and 18-3 of the current switch 18-0 conduct simultaneously with the same current density.

[0014] In general, to cause the sensing transistor 18-3 and the power transistor 18-2 to detect the current I feedback or the current I powerTo ensure that transistors 18-2 and 18-3 are conducting with the same current density, comparator 12 first compares the respective voltage drops across the tuned transistors 18-2 and 18-3. Based on the difference in the respective voltage drops across transistors 18-2 and 18-3, comparator 12 controls switches 14-1 and 14-2 (collectively referred to here as "switch 14") to vary the amount of load current at the output of transistor 18-3 (e.g., the amount of load current assigned to transistor 18-1). As described in more detail below, comparator 12 varies the amount of load current at the output of transistor 18-3 until the amount of load current is sufficient to cause the current density in transistor 18-3 to vary when transistor 18-1 conducts the current I. feedback generated to match the current density in transistor 18-2, while transistor 18-2 supplies the current I power leads.

[0015] The 18-0 current switch is a transistor-based high-side switch of a half-bridge. Although shown as a high-side switch of a half-bridge, the principles and techniques described here can also be applied to the 18-0 current switch if it operates as a low-side switch of the half-bridge. When the 18-0 current switch is turned on, the voltage V IN applied to the output of system 10 (e.g., a switching node).

[0016] The power switch 18-0 contains transistor 18-2 (e.g., a large power transistor) and transistor 18-3 (e.g., a smaller sensing transistor that acts as a current mirror of transistor 18-2). Transistors 18-2 and 18-3 can each be a field-effect transistor (FET). In this example, the drains of transistors 18-2 and 18-3 are both connected to V INconnected. In some examples, transistor 18-3 is smaller than transistor 18-2 by a factor of N. Transistors 18-2 and 18-3 are controlled by the same gate signal. When transistor 18-2 is switched on, transistor 18-3 is also switched on. Transistor 18-2 conducts the current I. power . Transistor 18-3 conducts I feedback .

[0017] The system relies on transistor 18-2 to connect the output of system 10 (e.g., labeled "OUT") to the voltage source V. IN to couple, while system 10 relies on transistor 18-3 to perform current sensing techniques to determine I feedback to conduct (i.e., a copy or a “tracking” current) from which system 10 determines the level of current I power , which is assigned to transistor 18-2, can sense the level of I. feedback The voltage from transistor 18-3 can be smaller than the level of I by a factor N. powerfrom transistor 18-2 (e.g., as long as the drain-source voltage and gate-source voltage of transistors 18-2 and 18-3 are equal). As used throughout this disclosure, the terms "feedback current", I feedback The terms tracking current and copy current are all used interchangeably to generally describe a current that proportionally reflects the level of the current flowing from a power transistor. In general, the term "feedback current" refers to I feedback Used for the current flowing in a sensing transistor (e.g., in transistor 18-3). feedback is equal to I power / N, when the current tracking system 10 has reached steady state. The terms "copy current" or "mirror current" generally describe a current that is a "copy" or a "mirror" of the feedback current I. feedback is. In other words, if the current tracking system 10 were to output a current equal to I feedbackis (e.g., similar to the output of System 400, which in Fig. (as shown in Figure 6), this current would be called a "mirror current".

[0018] Although shown as a high-side switch of a half-bridge, switch 18-0 can also be configured similarly to be a low-side switch of a half-bridge. Switch 18-0 can be used to energize a load (e.g., an inductive load) coupled to a switching node of a half-bridge (e.g., node OUT). The system can turn transistor 18-2 on and off from transistor 18-0 to control the voltage (or, in some examples, the current) at node OUT. For example, system 10 can rely on controlling switching transistor 18-2 to produce a PWM output signal at node OUT. Since system 10 relies on a gate signal (e.g., derived from a pulse-width modulation signal received from a control unit located in Fig. (1 not shown for simplification) supports, to cause transistor 18-2 to switch on and off, system 10 can simultaneously control transistor 18-3 to the same operating state (e.g., switched on or off) as transistor 18-2, in order to I feedback to direct. System 10 can rely on I feedback support to increase the amount of current I power , which comes from transistor 18-2, to sense or determine in some other way.

[0019] In an LSA-based current-tracking system, the LSA of other systems can draw a current through a mirror transistor, such as transistor 18-3, to match the voltage across the mirror transistor with the voltage drop across a corresponding power transistor, such as transistor 18-2, in order to generate a simulated current from the mirror transistor that is smaller (e.g., by a factor of N) than the current from the power transistor. However, there may be a significant delay in the rise of the current level through the mirror transistor to reach the correct level. Thus, other systems that incorporate LSAs may consequently exhibit a residual offset and / or unsuitable settling time with integrated / mean error.

[0020] Unlike LSA-based current tracking systems, System 10 is nonlinear and includes the comparator 12 to drive the switches 14, to control variable current generators 16-1 and 16-2 (collectively referred to here as "current generators 16"), and to charge and discharge the capacitor 20 to vary the amount of load current assigned to transistor 18-1 and the amount of current diverted through transistor 18-1. Current tracking system 10 can have a lower settling time and therefore track currents faster (i.e., in a shorter time interval) than other current tracking sensing systems.

[0021] For example, the current tracking system 10 includes a capacitor 20 arranged in parallel with transistor 18-1 (here also referred to as "transistor M1"). Transistor 18-1 can be a metal-oxide-semiconductor field-effect transistor ("MOSFET"), for example, an N-type MOSFET. Transistor 18-1 is configured to operate similarly to an output stage of an operational amplifier in an LSA-based current tracking system. However, as described here, current tracking system 10 does not include any operational amplifiers. Instead, current tracking system 10 relies on the comparator 12 to drive the switches 14, which control the charging and discharging of capacitor 20 to regulate the amount of load current assigned to transistor 18-1 and a feedback current I. feedbackto regulate the current tracking system 10. That is, the comparator 12 can control the switch 14-1 to cause current to flow from the current generator 16-1 to the capacitor 20. The comparator 12 can control the switch 14-2 to cause current to flow away from the capacitor 20 and be diverted to the current generator 16-2.

[0022] The 16-1 power generator is equipped with a high reference voltage V IN_3 connected. The current generator 16-2 is connected to a low reference voltage 22. The low reference voltage 22 is in Fig. 1 is shown as a voltage to ground, which in the example of system 10 is at the same potential as the source of transistor 18-1. In other examples, the low reference voltage may be at a different potential than the source of transistor 18-1. In this way, by controlling the switches 14, the comparator 12 can control the current generators 16 to charge and discharge the capacitor 20, so that the voltage across the capacitor 20 remains within the range of the high supply voltage V. IN_3 and the low voltage supply 22 remains.

[0023] The current generators 16 can be directly connected to a control terminal of transistor 18-1. Transistor 18-1 diverts current at a current level consistent with a current operating point of system 10. In other words, the tracking current I feedbackIn the current tracking system 10, the current oscillates around a current operating point required by transistor 18-1 to derive the desired tracking current level. The tracking current I feedback In the current tracking system 10, oscillation can occur due to a lag or delay associated with the time required to charge and discharge the capacitor 20. The magnitude of the oscillation in the tracking current I feedback may be negligible for some applications as long as the oscillation has a higher frequency and smaller amplitude relative to the frequency and magnitude of the current tracked by the current tracking system 10 (e.g., I power ).

[0024] As in Fig. As shown in Figure 1, one input to comparator 12 (e.g., a positive "plus" terminal) is coupled to the source of transistor 18-3, and the other input of comparator 12 (e.g., a negative "minus" terminal) is coupled to the source of transistor 18-2. When the voltage at the plus terminal of comparator 12 is higher than the voltage at the minus terminal, comparator 12 can charge capacitor 20 by causing switch 14-1 ("S") to close or otherwise operate in an "on" state to conduct current flowing from current generator 16-1, and further by causing switch 14-2 ("S") to open or otherwise operate in an "off" state to prevent current from flowing to current generator 16-2. Charging capacitor 20 in this way can cause the amount of current diverted into transistor 18-1 to increase.In this way, transistor 18-1 acts as a current source to generate a feedback or tracking current drawn from transistor 18-3.

[0025] If the voltage at the positive terminal of comparator 12 is lower than the voltage at the negative terminal, comparator 12 can discharge capacitor 20 by causing switch 14-1 to open and, further, by causing switch 14-2 to close. In this way, current generator 16-2 can draw current from capacitor 20 to discharge it and reduce the current-dissipation capability of transistor 18-1. An example behavior of the tracking current I feedback is in Fig. Figure 2 is shown and discussed below. The comparator 12 may exhibit a small hysteresis and / or delay in the control of the switches 14.

[0026] Accordingly, the system can enable the sensing transistor 18-3 and the power transistor 18-2 to detect the current I feedback or the current I power to conduct with the same current density, by supporting the comparator 12. The comparator 12 compares the voltage drop across the tuned transistors 18-2 and 18-3, and based on the comparison controls the switches 14-1 and 14-2 to vary the amount of load current at the output of transistor 18-3 until the amount of load current is sufficient to match the current density of transistor 18-3 to the current density of transistor 18-2.

[0027] The level of current handled by the current generators 16 can be selected according to the desired dynamics or speed capability of the current tracking system 10. For example, if the current generators 16 can handle a larger amount of current, the capacitor 20 can be charged and discharged more quickly, causing the current tracking system 10 to operate faster. In some examples, parameters of the current tracking system 10 are selected such that the current in the transistor being measured does not ramp up faster than the current in transistor 18-1. Furthermore, a limit can also be placed on how quickly the current rises from the beginning to the end of the transistor. ON -Cycle of transistors 18-2 and 18-3 increases.

[0028] As is consistently used for revelation, a T ON-Cycle of a transistor generally defined as a period of time when the transistor is closed, conducting current through its conduction channel, or otherwise operating in an on-state, other than the T OFF -Cycle of the transistor, representing the time the transistor is open, not conducting through its channel, or otherwise operating in an off-state. For example, T represents ON The time interval of transistors 18-2 and 18-3 is the period during which transistors 18-2 and 18-3 are closed or otherwise operating in an on-state, instead of being open or otherwise operating in an on-state. With reference to a half-bridge configuration, the term T ONThe half-bridge cycle is generally used to describe the time interval when the high-side switch of the half-bridge is closed or otherwise operating in an on-state, and the low-side switch of the half-bridge is open or otherwise operating in an off-state. Further referring to a half-bridge configuration, the term T OFF -Cycle of a half-bridge generally used to describe the time span when the high-side switch of the half-bridge is open or otherwise operating in an off-state, and the low-side switch of the half-bridge is closed or otherwise operating in an on-state.

[0029] In some examples, one or more current generators 16 can be selected such that they are capable of generating a large current, so that the charging and discharging of the capacitor 20 occurs within a specific time period suitable for the application to which the current tracking system 10 is to be applied. Thus, different components of the current tracking system 10 can be selected for configurations that allow specific speeds in the tracking current to be achieved.

[0030] Fig. 2 is a time diagram 40, which shows an example behavior of tracking current, I feedback , in the current tracking system 10 of Fig. 1 in accordance with one or more techniques described in this disclosure. The timing diagram 40 represents a real example behavior of the tracking current of system 10 (I feedback ), which is represented by line 42, over a time period T ONLine 44 shows an ideal output current (I). power / N) for I feedback About T ON The capacitor is charged and discharged faster with a current represented by line 46 (“I cap “).

[0031] Line 42 shows waves, oscillations, or spikes that can originate from various factors, including the speed of comparator 12, the transconductance of comparator 12, the current ("I") used to charge / discharge capacitor 20, and the value of capacitor 20 itself. In some examples, these parameters are chosen to control the amount of waves, oscillations, and spikes of I. feedbackto reduce or minimize the effects shown in line 42. In one example, the period of the first sawtooth may be approximately 2.5 nanoseconds (“ns”). In some examples, several trade-offs are balanced when the amount of waves, oscillations, or spikes is reduced. For example, while accelerating comparator 12 may result in a shorter response time and therefore a higher wave oscillation frequency and also a smaller wave amplitude, accelerating comparator 12 may also result in maintaining a maximum tracking speed or tracking slope. Whereas, while decreasing the charging current of power sources 16 may result in a lower wave oscillation frequency and also a smaller wave amplitude, decreasing the charging current of power sources 16 may also result in the maximum tracking speed or tracking slope being reduced.In addition, although increasing the size of capacitor 20 can lead to a lower oscillation frequency of the wave and also to a smaller amplitude of the wave, increasing the size of comparator 20 can also lead to a reduction in the maximum tracking speed or tracking slope.

[0032] One point I ini on the ideal I feedback -Line 44 represents a starting current level ("I ini “), and a point I fin Line 44 represents a final current level ("I") fin “). To determine the starting current level I ini To achieve the desired current as quickly as possible, the current tracking system 10 includes the variable current generator 16-1. The variable current generator 16-1 can change the current by following a rule defined according to the desired parameters for the current tracking system 10, for example, using the positive and negative transitions of the comparator 12. In the example of Fig. 2. The current I cap , which is represented by line 46, is reduced when the second positive transition of comparator 12 occurs.

[0033] Fig. Figure 3 is a graphical representation 60 that illustrates an example difference between the gain-bandwidth products of an operational amplifier and a comparator in a closed-loop current sense system in accordance with one or more techniques described in this disclosure. That is, the graphical representation 60 compares a gain-bandwidth product of the operational amplifier 66, which can be used to track the current, and a gain-bandwidth product of the comparator 62.

[0034] Conventional current tracking circuits can use operational amplifiers to control current sources 16 in a linear manner, which has a limited slew rate (e.g., the maximum possible rate of change of the signal at any point in the circuit) and limited bandwidth due to capacitors introduced for stability. Because of these limitations, conventional current tracking circuits cannot divert or supply current at a sufficient rate (e.g., at a frequency higher than 1 megahertz (“MHz”) with a duty cycle less than 15%), which is sometimes required in modern DC-DC converters (such as a step-down converter) for applications such as servers and notebooks (e.g., laptop computers and other mobile computing devices).Failure to divert or supply current at sufficient speed can introduce a systematic offset in the tracking current. In some scenarios, the tracking current does not reach the tracking state because of T. ON The signal is too short. One or more capacitors are included within the operational amplifier to stabilize the control loop. These capacitors must be charged and discharged, which can introduce a time delay.

[0035] Unlike other linear-type systems, such as LSA-based current-tracking systems that rely on operational amplifiers (also known as "op-amps"), the nonlinear systems described here, such as System 10, rely on one or more comparators to control the current flow into or out of one or more current generators. These generators charge and discharge a capacitor used to speed up the current-tracking process. The nonlinear systems in this disclosure include a comparator that is faster than the current-sensing system containing the operational amplifier because it does not include the stabilizing capacitor. Some of the example devices described here can be ten to twenty times faster than conventional LSA-based current-tracking systems.

[0036] Fig. Figure 4 is a schematic diagram showing an example implementation of the current tracking sensing system 10. Fig. 1 in accordance with one or more techniques described in this disclosure. System 80 is an implementation of current tracking sensing system 10, which includes optional features that determine the settling time and the associated amount of waves, oscillations, or spikes in the tracking current I. feedback , which above refers to Fig. 1 and Fig. 2 are described, can be reduced.

[0037] Some differences between the current sensing system 10 of Fig. 1 and System 80 from Fig. 4 are that the system 80 contains the counter 82 and the variable current generators 16 of Fig. 1 have been replaced by power generators 84-1 and 84-2. Two additional "boost" power generators, 84-3 and 84-4, and some additional digital logic have also been added to System 80.

[0038] In the operation of System 80, switch 14-1 starts operation in an off or open state, and switches 14-2, 14-3, and 14-4 start operation in an on or closed state. When a load is coupled to node OUT and transistor 18-2 is switched on, the current I begins to flow. power to flow through transistor 18-2. If the positive terminal of comparator 12 is coupled to the source of transistor 18-3 and the negative terminal of comparator 12 is coupled to the source of transistor 18-2, when the current I powerWhen current begins to flow through transistor 18-2, the positive terminal of comparator 12 can be at a higher potential than the negative terminal of comparator 12 because, unlike the load current that loads node OUT, there is no load current that loads transistor 18-3, causing the comparator output to go high.

[0039] When the output of comparator 12 goes high, switch 14-1 switches to an on or closed state, and switch 14-2 switches off or opens. Capacitor 20 will begin to be charged from current generators 84-1 and 84-3, and the gate-source voltage of transistor 18-1 will increase. When the gate-source voltage of transistor 18-1 reaches a gate threshold voltage level, the drain current of transistor 18-1 will begin to flow. The drain current will increase as long as the gate-source voltage at transistor 18-1 increases (e.g., as capacitor 20 is charged). If the gate-source voltage at transistor 18-1 becomes too high, the drain current may become larger than desired (e.g., exceed a maximum drain current level) and may cause the voltage at the positive terminal of comparator 12 to drop below the voltage level at the negative terminal of comparator 12.When the voltage level at the positive terminal of comparator 12 falls below the voltage level at the negative terminal of comparator 12, comparator 12 can change its output from high to low. In response to the output of comparator 12 going low, switch 14-1 can turn off or open, and switch 14-2 can turn on or close, and capacitor 20 can begin to discharge, with current being drawn from capacitor 20 to current generator 82-4 and current generator 84-4.

[0040] System 80 can continue to operate, with capacitor 20 charging and discharging in this manner, so that the tracking current I feedback can oscillate at or approximately close to an ideal current value (e.g., as in line 44 of Fig. (as shown in Figure 2). Counter 82 can count the number of positive transitions of comparator 12 (e.g., how many times the output of comparator 12 transitions from a low output, where capacitor 20 is discharging, to a high output, where capacitor 20 is charging). At point 50, which is shown in Figure 2, the counter 82 can count the number of positive transitions of comparator 12 (e.g., how many times the output of comparator 12 transitions from a low output, where capacitor 20 is discharging, to a high output, where capacitor 20 is discharging ... Fig. As shown in Figure 2, one or more switches (e.g., switches 14-3 and 14-4) of the boost power generators 84-3 and 84-4 will be open.

[0041] Fig. Figure 4 shows that when switch 14-3 is on or off, the sum of the respective currents I1 from current sources 84-1 and 84-3 is equal to I1 + I1 = I2. In other words, both current generators 84-1 and 84-3 contribute I1 to the total current I2. When switch 14-3 is off, generator 84-3 provides no current, and the current from generator 84-1 remains I1, so the current contributing to I2 is equal to I1. Similarly, Figure 4 shows that... Fig. 4, that when switch 14-4 is closed, the sum of the respective currents I1 from current sources 84-2 and 84-4 is equal to I1 + I1 = I2. In other words, both current generators 84-2 and 84-4 contribute I1 to the total current I2. When switch 14-4 is open, generator 84-4 provides no current, and the current from current generator 84-2 is I1 = I2.

[0042] In this way, the settling speed at the beginning / run-up can be doubled when I1 + I1 = I2, and transistor 18-1 can reach an ideal drain current more quickly. However, because the charging current I2 can be high when I1 + I1 = I2, the ripple associated with the charging current can be large due to a limit on the velocity / propagation delay of comparator 12. To reduce the ripple and improve the accuracy of the tracking current I feedbackTo increase the tracking current so that it better matches the ideal current of transistor 18-1, the charging boost current of the boost current generators 84-3 and 84-4 is removed, so that the charging current drops from 2*I1 to I1.

[0043] To prevent the current generator 84-1 and 84-2 from entering a triode region (also known as the ohmic region) when not in use, the current generator 84-1 or 84-2 that is not connected to the capacitor 20 is connected to a "voltage copy" of the voltage across the capacitor 20 (which can be achieved, for example, with a buffer). This allows the unused current generator 84-1 or 84-2 to be reconnected to the capacitor 20 without introducing an additional charge, which would otherwise be introduced due to the voltage difference between the output of the previously unused current generator 84-1 or 84-2 and the capacitor 20.

[0044] In some examples, a higher charging current (e.g., 2*I1) is used at the beginning of operations of System 80 to charge capacitor 20. For example, boost current generators 84-3 and 84-4 can only be used at the beginning of T ON They can be used to charge and discharge capacitor 20. The boost current generators 84-3 and 84-4 can be connected in such a way as to cause I2 to be supplied by the introduction of T ON The current is approximately ten microamperes (µA) up to the second positive transition of comparator 12. Capacitor 20 can have a value of six hundred and fifty femtofarads (fF) and, if I2 is equal to five µA, can be charged and discharged after the second positive transition of comparator 12.

[0045] During a T OFFDuring the -phase of the switch, the current-sensing circuit can maintain the gate bias, which opens all switches 14 and leaves capacitor 20 charged at its current value. To shorten the settling time for the next T ON To reduce the -phase, the boost current generators 84-3 and 84-4 can be used until the second positive transition of the output of comparator 12. Even if transistor 18-1 is switched off during the T OFF When the -phase is switched on, transistor 18-1 can operate in the triode region, where the voltage across the drain and source terminals of transistor 18-1 is smaller than the saturation voltage (e.g. V). DS < V DS_SAT It is pointed out, as will be described later in the description of Fig. 4. It becomes clear that the maximum current that can flow through transistor 18-1 is I MAX_NEGATIVE is.

[0046] Thus, the tracking current I feedbackSystem 80 can oscillate around a specific value (e.g., the ideal current of transistor 18-1) and does not need to be stable to function as an adequate current tracking system for some applications. Additionally, comparator 12 does not need to be clipped to slow it down, as is necessary for LSA-type current tracking systems. The fact that comparator 12 can operate without clipping can lead to an increase in the bandwidth of System 80 compared to other LSA-type current tracking systems. Furthermore, because the comparator is not clipped, System 80 can maintain a higher gain across a wider bandwidth, achieving greater bandwidth and potentially higher overall speed.

[0047] System 80 is configured to track both positive and negative currents. As used here, current leaving or flowing out of a transistor represents a "positive current," and current entering or flowing into a transistor represents a "negative current." For example, the current I POWER in Fig. 4 shown with a directional arrow pointing away from or leaving a source terminal of transistor 18-2, and thus represents I power a positive current. The tracking current I feedbackThis is shown to indicate that it exits a source terminal of transistor 18-3 and is also a positive, not a negative, current. Referring to a half-bridge configuration where node OUT represents a switching node between a high-side switch and a low-side switch, a positive current refers to a current entering the switching node from a switch of the half-bridge and exiting the switching node into a load. A negative current refers to a current exiting a load, entering the switching node, exiting the switching node, and entering a switch.

[0048] In order to be able to track both positive and negative current flowing through transistor 18-2, system 80 adds a current offset I MAX_NEGATIVE to the source node of transistor 18-3 and the positive "plus" input of comparator 12. The introduction of the current offset I MAX_NEGATIVEThis ensures that System 80 functions similarly to the output stage of a Class A operational amplifier in an LSA-type current-tracking system. For example, when zero current flows through transistor 18-2, comparator 12 is configured to ensure that zero current flows through transistor 18-3, causing 18-1 to receive a current equal to I. MAX_NEGATIVE allows current to flow out. When a positive current flows through transistor 18-2, transistor 18-1 allows a current greater than I to flow out. MAX_NEGATIVE , which results in a positive tracking current I feedback through transistor 18-3. Conversely, if a negative current flows through transistor 18-2, transistor 18-1 allows a current to flow that is less than I. MAX_NEGATIVE , which results in a negative tracking current I feedback through transistor 18-3.

[0049] Fig. Figure 5 is a schematic diagram representing an example biasing circuit 100 configured to bias a low-side copy current generator / source of a current tracking sensing system in accordance with one or more techniques described in this disclosure. For example, Fig. 5 represents an example (application) current follower, which is part of system 10 of Fig. 1 or part of System 80 of Fig. 4 is used. In the example of Fig. 5 is transistor M1 from Fig. 4 the same as transistor M1 from Fig. 5. As such, for the sake of simplicity, System 100 is made up of Fig. 5 below in the context of System 80 from Fig. 4 described. The current I SENSE_LS_COPY follows the current I SENSE_HS_COPY The follower is used in the current tracking system to create a current copy of the tracking current in transistor 18-2. Fig. 4 flows as ISENSE_HS_COPY an OUT CURRENT_SENSE (i.e., connection 120) to provide or output.

[0050] The following description of Fig. Section 5 serves to provide a brief introduction to the similar bias circuitry and techniques used in Fig. 6 are shown to provide. As such, any reference to the direction of a current flow is described with reference to the direction arrow that is at the output terminal (e.g., the switching node) of the Fig. Figure 6 shows the half-bridge configuration. A positive current refers to a current flowing from the high-side and low-side switches of the half-bridge to the switching node and a load. A negative current refers to a current flowing from the load to the switching node and back to the high-side and low-side switches of the half-bridge.

[0051] The bias circuit 100 reduces the speed requirement of a current tracking system because, if one side (e.g., the high side) of the current tracking system can be switched on, the bias circuit 100 can maintain the bias of the side (e.g., the low side) that is switched off. Thus, the current tracking circuit that is currently switched off can be "ready for use" as soon as it is switched back on and can have an initial operating state (e.g., operating bias) that corresponds to the state present in the current tracking circuit that is currently switched on.Accordingly, in cases where an inductive load is coupled to the half-bridge and the load current alternates between being supplied from the high side and the low side, the circuit 100 can reduce the speed requirement of the sensing loop while providing a seamless transition from sensing the current on the high side to sensing the current on the low side and vice versa.

[0052] The bias circuit 100 is configured to couple to a source terminal (e.g., a current output) of its sense FET of a high-side current-sensing circuit (HS current-sensing circuit) at point A and to a source terminal (e.g., a current output) of a sense FET of a low-side current-sensing circuit (LS current-sensing circuit) at point B. In this example, the current flowing into transistor M2 is copied to transistors 108-1 and 108-2. Transistor 108-3 is turned on, but no current flows through it because its load (e.g., the low-side sense FET) is turned off when the high-side sense FET is turned on. In some examples, if system 100 has one or more I MAX_NEGATIVE -Power generators included (not shown in Fig. 5, however, with reference to the additional figures such as e.g. Fig. (as described in section 4), the transistor 108-3 can handle a maximum current of IMAX_NEGATIVE supply.

[0053] The bias circuit 100 contains a comparator 102, which compares the current in the low-side copy current generator / source (I SENSE_LS_copy ) maintains at approximately the same current level as the current in the high-page copy power generator / source (I SENSE_HS_copy The output of comparator 102 controls switches 110-1 and 110-2, which control current generators 112-1 and 112-2. The bias circuit 100 contains three transistors 108-1, 108-2, and 108-3 (collectively referred to as "transistors 108") and capacitors 104-1 and 104-2. The bias circuit 100 also contains transistor M2 and transistor M1. One or more of transistors 108, M1, and M2 may be MOSFETs.

[0054] Some current tracking systems that use operational amplifiers and current mirrors to track the positive current in the half-bridge loaded by an inductive load have limited speeds that prevent them from handling a transition from a high-side switch being on and a low-side switch being off, to the high-side switch being off and the low-side switch being off, and vice versa. The operational amplifiers have limited slew rates. Furthermore, due to the capacitances introduced to stabilize the control loop, the operational amplifiers, with their limited bandwidth, cannot divert or supply the current at the speed sometimes required by the system.In the best case, this problem introduces a systematic offset into the tracking stream, or in the worst case, the tracking condition is not met in time because the time is too short.

[0055] In contrast, systems using circuits described here, such as the bias circuit 100, can track the positive and negative current flowing in both the high-side and low-side switches of the half-bridge, and track the transition from the high-side switch being on and the low-side switch being off to the high-side switch being off and the low-side switch being on (and vice versa), providing a proportional current as output. The settling time due to switching between the high-side and low-side switches is reduced to almost zero. Although boost techniques discussed above with reference to Fig. As described in section 4, prestressing techniques that can accelerate the transfer between the high and low sides can be used. Fig. The techniques described in section 5 are more efficient. These biasing techniques can also improve the performance of both nonlinear systems and systems that rely on linear sensing amplifiers.

[0056] When a half-bridge is coupled to an inductive load, and to minimize the settling time required to reach the operating current of the half-bridge's low-side power transistor during turn-on or "restart" (e.g., transitions from off-state operation to on-state operation), the biasing circuit 100 can bias the current source 108-3 so that it is ready to act as a source for the same amount of current flowing through the conduction channel of the high-side power transistor (e.g., the power transistor operating in the on-state). In other words, when the half-bridge's low-side power and sensing transistors are off, the current source 108-3 can maintain a gate-source voltage bias equal to the operating current flowing in the high-side power transistor.This allows the power source 108-3 to be ready to provide the correct operating current required by the low-side sensing transistor when the low-side power and sensing transistor restarts.

[0057] Specific advantages of the bias circuit 100 are described in the following text. Fig. As can be seen in Figure 6. In short, the biasing circuit 100 can reduce the settling time of a current-tracking sensing circuit (e.g., the time a current-tracking sensing circuit takes before settling on the current through the conduction channel of a current-tracking switch) of a half-bridge while such a half-bridge is supplying current to an inductive load. In particular, when a transition from an off-state to an on-state occurs, the biasing circuit 100 can allow the current source associated with the sensing FET of the current-tracking switch being turned off to maintain a bias and "standby" readiness, waiting to dissipate or supply current as required by the current-tracking switch when the switch returns to the on-state, in order to ensure that there is little difference in the voltage drop between the sensing FET and the current-tracking switch.

[0058] Fig. Figure 6 is a schematic diagram representing the current-tracking system 400 for a half-bridge circuit, in which the high-side switch 402 is coupled to the low-side switch 430 at the switching node 410 (OUT). The current-tracking system 400 is configured to track positive and negative currents flowing in both the high-side switch 402 and the low-side switch 403 in accordance with one or more techniques described herein. The current-tracking system 400 can track positive and negative currents without discontinuities. Various examples of the current-tracking system 400 may include aspects or features that are described here with reference to other example circuits, such as the bias circuit 100 of [reference missing]. Fig. 5 are described.

[0059] As described throughout this disclosure, for example, for current tracking systems that rely on both a high-side power transistor and a high-side sensing transistor, and a low-side power transistor and a low-side sensing transistor, it is understood that these current tracking systems can use monolithic or separate transistor solutions. For example, in instances where a system uses a high-side power transistor and a high-side sensing transistor, the system can use a single monolithic high-side transistor component or two separate high-side transistor components to perform the functionality of the high-side power transistor and the high-side sensing transistor.

[0060] In instances where a system uses a low-side power transistor and a low-side sensing transistor, the system can use a single monolithic low-side transistor component or two separate low-side transistor components to perform the functionality of the low-side power transistor and the low-side sensing transistor. In other words, the high-side switch 402, which is in Fig. Figure 6 shows the power transistor 136-1 and the sensing transistor 136-2, comprising a single monolithic high-side transistor component or two separate high-side transistor components. The low-side switch 430, which is shown in Fig. As shown in Figure 6, the power transistor 136-3 and the sensing transistor 136-4 can comprise a single monolithic low-side transistor component or two separate low-side transistor components.

[0061] Additionally, transistors 136-1 and 136-2, and transistors 136-3 and 136-4, can comprise a single monolithic high-side and low-side transistor component, or two to four separate high-side and low-side transistor components. In general, for each of the current switches described here (e.g., current switches 18-0, 402, 430, etc.), the current switch power transistor and the current switch sensing transistor, along with their respective current-tracking sensing systems, can be monolithically integrated onto a single chip (e.g., a single silicon wafer). In other words, each of the systems 10, 80, 100, 400, etc., can be formed on a single silicon wafer.

[0062] The current tracking sensing system 400 includes the high-side switch 402, which contains the power FET 136-1 and the sensing FET 136-2, the sources of which are coupled to the high-side comparator 140-1. The low-side switch 430 contains the power FET 136-3 and a sensing FET 136-4, which is coupled to the comparator 140-2. The switching node (OUT) HALF_BRIDGE ) is an output for the half-bridge, where an inductive load can be connected. The current tracking sensing system 400 includes the current sources 420-1 to 420-7 inclusive (collectively referred to here as "current sources 420").

[0063] The current tracking system 400 further includes transistors M1 through M5, some of which can operate as current mirrors, as described above. Current mirror 502 is a first current mirror of system 400 and is coupled between the high-side switch 402 and the auxiliary comparator 406. The first current mirror 502 contains two transistors, M1 and M2. Similarly, current mirror 504 is a second current mirror of system 400 and is coupled between the low-side switch 430 and the auxiliary comparator 406. The second current mirror 504 contains three transistors, M3, M4, and M5. The current tracking system 400 also includes two buffers 404-1 and 404-2 (collectively referred to here as "buffer 404").

[0064] The current tracking system 400 further incorporates comparators 140-1, 140-2, and 406 instead of operational amplifiers (i.e., transconductances) to control the output of the current mirrors 502 and 504. The comparators 140-1, 140-2, and 406 allow the current tracking system 400 to utilize the maximum speed offered by other components within the system because there are no bandwidth-limiting stabilizing capacitors that need to be charged and discharged. The outputs of comparators 140-1, 140-2 and 406 control the gates of switches 414 and the collectors of switches 432, which control the current sources 420-2, 420-3, 420-5 and 420-6, which charge or discharge the capacitors 413-1 and 413-2, which are connected to the gates (bases) of transistors M1-M5 in current mirrors 502 and 504 through buffers 404.The current output capabilities of the controlled current sources 420-2, 420-3, 420-5, and 420-6, and the capacitance characteristics of capacitors 413-1 and 413-2, can be selected to meet the speed requirements of the current tracking sensing system 400. The output of comparator 140-2 controls switches 432-1 through 432-4 (collectively referred to as "switch 432"), which are coupled to current sources 420-5 and 420-6. The output of comparator 140-1 controls switches 414-1 through 414-4 (collectively referred to as "switch 414"), which are coupled to current sources 420-2 and 420-3.

[0065] Buffer 404-2 is coupled between capacitor 413-2 and the gates of transistors M3, M4, and M5, as well as other components of System 400. Buffer 404-1 is coupled between capacitor 413-1 and the gates of transistors M1 and M2, as well as other components of System 400.

[0066] The current tracking sensing system 400 also includes two multiplexers (“MUX”) 440-1 and 440-2 (collectively referred to here as “MUXs 440”). MUX 440-1 receives as input a pulse-width modulation (PWM) signal and outputs from comparators 140-1 and 406. MUX 440-1 multiplexes these signals together to control switches 414. Similarly, MUX 440-2 receives as input the same PWM signal and the outputs from comparators 140-2 and 406. MUX 440-2 multiplexes these signals together to control switches 432. Thus, the digital PWM signal controls MUXs 440 to connect comparators 140-1 and 140-2, or the auxiliary comparator 406, to switches 414 and 436.

[0067] During operation, when the high-side switch 402 is turned on, the low-side switch 430 is turned off. When the PWM is high, the high-side switch 402 is turned on, and the load current flows through the power FET 136-1. Consequently, the output of comparator 140-1 controls the switches 414. For example, comparator 140-1 controls switches 414, which control M1 and M2, and auxiliary comparator 406 controls switches 432 to control M3, M4, and M5. The auxiliary comparator 406 and M3, M4, and M5 operate as a current follower. During this time, the low-side switch 430 is turned off, and therefore no current flows through the power FET 136-3 or the sensing FET 136-4 of the low-side switch 430.

[0068] When the PWM is low, the low-side switch 430 is turned on, and the high-side switch 402 is turned off. Current flows through the power FET 136-3, and thus the output of comparator 140-2 controls switches 432. For example, comparator 140-2 controls switches 432 to control M3, M4, and M5, and auxiliary comparator 406 controls switches 414 to control M1 and M2. Auxiliary comparator 406 and M1 and M2 operate as a current follower. During this time, the high-side switch 402 is turned off, and thus no current flows through either the power FET 136-1 or the sensing FET 136-2 of the high-side switch 402.

[0069] The 400 current tracking system can track positive and negative currents without any discontinuities. This functionality is guaranteed by the 420-1 and 420-4 current generators, which provide the maximum negative current I MAX_NEGATIVEProvide current. The current tracking sensing system 400 can track the current at either switch 402 or 430, even when the switching frequency is high and / or the current waveform of the load current flowing through switches 402 and 430 is very high, because it is based on nonlinear circuitry and uses the bias circuit. The settling times when the half-bridge transitions between the output of current from the high-side switch 402 and the low-side switch 430 are reduced due to the bias circuit.

[0070] The comparator 406 is configured, V feedback within a differential level threshold of V ref to hold. For example, the comparator can hold 406 V feedback approximately equal to V ref hold. This implies that the current I SENSE_HS_COPY from transistor M3 approximately with current I SENSE_LS_COPY matches, which goes into transistor M2.

[0071] The current tracking sensing system 400 can operate as follows. The M1 transistor conducts a current I. M1 = I MAX NEGATIVE + I feedback The transistor M1 can only conduct positive currents, and therefore the above expression is only true as long as I M1 The system remains positive. This means that the system has a functional limit for tracking negative load currents (e.g., current flowing into half-bridge output 410). However, theoretically, infinitely high positive currents (e.g., current flowing out of half-bridge output 410) can be tracked.

[0072] Since the auxiliary comparator 406 works in such a way that it V FEEDBACK = V ref This indicates that I M1 / M = I M2 = I M3 = I M4 is, and that it exhibits such a current that comes from or into I OUTCURRENT_SENSE = I feedback / M flows, with the offset current I MAX_NEGATIVE_CURRENTThe current added by power sources 420-1 and 420-4 must ultimately be subtracted by power source 420-7. This applies to both positive and negative load currents. OUTCURRENT_ SENSE -Electricity can be the following: IOUTCURRENT_SENSE=IM1M−IMAXNEGATIVECURRENTM =IMAXNEGATIVECURRENT+IfeedbackM−IMAX_NEGATIVE_CURRENTM=IfeedbackM

[0073] The low-side switch 430 of the current tracking sensing system 400 conducts I OUTCURRENT_SENSE directly to. As described above, I applies. OUTCURRENT_ SENSE = IfeedbackM for both positive and negative current. In some examples, the accuracy required for the low-side switch 430 is higher than the accuracy required for the high-side switch 402. While T OFF, while the low-side switch 430 is switched on, the auxiliary comparator 406 controls the switch 414, which controls the current mirror 502 to follow the current flowing in the low-side switch 430.

[0074] The comparator 406 controls the tracking current generator, which is connected to the part of the half-bridge that is switched off, thus maintaining the bias of the current mirror 502 or 504 that is not currently used to provide a feedback signal, so that it is at the same bias as the other current mirror 502 or 504 that is used to provide a feedback signal. In this way, the oscillations and the settling time after the switching operations from the low-side switch 430 to the high-side switch 402 and vice versa are reduced.

[0075] Fig. Figures 7A-7C are timing diagrams that represent example currents in different current tracking sensing systems in accordance with one or more techniques described in this disclosure. Fig. 7A represents a systematic offset that can occur in a current tracking sensing system that uses a linear amplifier and no bias circuit such as the bias circuit 100 from Fig. 5 contains. Curve 160 shows an idealized tracking current in the current tracking sensing system, and curve 162 shows an actual tracking current in the current tracking sensing system. As in Fig. As shown in Figure 7A, there is a systematic offset between the idealized current in curve 160 and the actual current in curve 162.

[0076] Fig. Figure 7B illustrates how a tracking state in a current tracking sensing system that uses a linear amplifier and no bias circuit such as the bias circuit 100 of Fig. 5 contains, cannot be achieved. Curve 160 represents an idealized tracking current in the current tracking sensing system. Curve 166 represents an actual tracking current in the current tracking sensing system. In the example of Fig. 7B, the actual tracking current, shown as curve 166, does not reach the tracking state because the time between T ON and T OFF is too short.

[0077] Fig. Figure 7C shows a time diagram 170, which shows an example behavior of the tracking current in a current tracking sensing system that uses a comparator and has a bias voltage, such as the current tracking sensing system 400 from Fig. 6. Time diagram 170 represents ideal behavior of the tracking current I. feedback , represented by curve 172, compared with a real-world example behavior (i.e., less ideal) of the tracking current I feedback , which is represented by curve 174, over a time interval T ON and T OFF In this example, during T ON the high-side transistor 402 of Fig. 6 switched on, and the low-side transistor 430 of Fig. 6 is switched off. During T OFF The opposite is true, and the low-side transistor 430 is switched on while the high-side transistor 402 is switched off. In this example, a PWM signal is input into MUX 440-1 and MUX 440-2 while T ON high and during T OFF deep.

[0078] Curve 174 shows waves, oscillations, or spikes that can be caused by several factors, including the velocity and transductance of comparators 140-1, 140-2, and 406, and the current used to charge a capacitor. In some examples, the parameters are chosen to control the amount of waves, oscillations, and spikes of I feedback to reduce or minimize the effects shown in curve 174. In some examples, several trade-offs are balanced when the amount of waves, oscillations, or spikes is reduced. In one example, the period of the first sawtooth wave can be approximately 5 nanoseconds (ns).

[0079] Settling times can occur during each transition between T ON and T OFF be present. During T ON A low-side mirror follows the current flowing in a high-side mirror. A low-side mirror can supply the output current. During T OFFThe high-side mirror can follow the current flowing in the low-side mirror. The low-side mirror supplies the output current. In this example, a low-side capacitor has been charged so that the low-side mirror has approximately the same current that flowed in the high-side mirror while the PWM was high (e.g., the low-side mirror was biased). When the low-side comparator 140-2 begins driving the low-side mirror, the current flowing in the low-side mirror has the correct value. This functionality eliminates or reduces the settling time each time the PWM goes from high to low (e.g., in the transition from T ON to T OFF ). When the half-bridge is subjected to an inductive load.

[0080] Example parameters for the current tracking sensing system 400, which correspond to the time diagram shown. Fig. 7C can be as follows. One PWM frequency is 1 megahertz (MHz) with a 10% duty cycle. T ON is approximately 100 nanoseconds (“ns”) and T OFF is approximately 900 ns. In another example, the PWM frequency is 2 MHz, T ON is approximately 50 nanoseconds (“ns”) and T OFF is approximately 450 ns. These parameters can be higher or lower, depending on the requirements of the Half-Bridge Current Tracking Sensing System 400 and any other system in which the half-bridge is used.

[0081] Fig. Figure 8 is a schematic diagram illustrating an example current tracking sensing system 500 configured to track positive and negative currents flowing in both sides of a half-bridge in accordance with one or more techniques described in this disclosure. Similar to the current tracking sensing system 400 of Fig. The 500 current tracking system can track both positive and negative current. The 500 current tracking system can follow changes in current direction without any discontinuity.

[0082] The current tracking sensing system is a half-bridge comprising the high-side switch 402 and the low-side switch 430. The high-side switch 402 contains a high-side power transistor 136-1 and a high-side sensing transistor 136-2. Similarly, the low-side switch 430 contains a low-side power transistor 136-3 and a low-side sensing transistor 136-4. An auxiliary comparator 406 is coupled between the high-side switch 402 and the low-side switch 430. The auxiliary comparator 406 is configured to drive the second current mirror 504 while the high-side switch 402 is active and to drive the first current mirror 502 while the low-side switch 430 is active.This means that the auxiliary comparator 406 is configured, by at least one of the current sources 508-1 and 508-2 driven by the auxiliary comparator 406, to bias a first capacitor 510-1 while the high-side switch 402 is inactive, such that the current level in the high-side current mirror 502 is within an operating level threshold of the current in the low-side switch 430, which is active. In other words, the auxiliary comparator 406 operates to bias the current mirror 502, which is part of the sensing circuit for the switch 402, while it is inactive.Furthermore, the additional comparator 406 biases a second capacitor 510-2 by at least one of the current sources 508-3 and 508-4, which are driven by the additional comparator 406, while the low-side switch 430 is inactive, so that a current level in the low-side current mirror 504 is within a working level threshold of a working current in the high-side sensing transistor 136-2 when the high-side switch 402 is active.

[0083] For example, the auxiliary comparator 406 works to bias the capacitor 510-1 and the current flowing in M2 and M1. If the gate-source voltage is such that the current in M1 can be higher than I MAX_NEGATIVE_CURRENT , it will enter the triode region if M1 is a MOS device (M1 will saturate if it is a bipolar junction transistor). The current flowing into it will be equal to I MAX_NEGATIVE_CURRENT be, but V GS will be set to divert the correct current as soon as it is requested (TOFF goes, for example, to T ON over). On the other hand, if the current that can flow in M1 is lower than I MAX_NEGATIVE_CURRENT If so, the device M1 will determine the current flow, and I MAX_NEGATIVE_CURRENT will move into the triode range.

[0084] An example operation of the current tracking sensing system 500 is as follows. While the high-side switch 402 is active (e.g., the power transistor 136-1 and the sensing transistor 136-2 are active), M2 contains a copy of the current in M1. The comparator 406 operates to charge and discharge the gate voltage of the transistors in the second current mirror 504, which contains M3, M4, and M5. When M2 discharges more current than M3 supplies, the feedback voltage of the auxiliary comparator 406 is lower than V1. refIncreasing the charge in capacitors 510-2 increases the voltage drop between the sources and gates of M3, M4, and M5. This means that comparator 406 works to cause the current in M3 to follow the current in M2 (a copy of the current in M1). M3 is a mirror, and M4 contains a copy of the current in M3. The offset current I max_negative_current , which is connected to the high-side sensing FET 136-2, is a fixed reference current that is subtracted from the current sensing output 412 (scaled by a factor M, I). max_negative_current / M). In this way, the current flowing from the current sense 412 is exactly a copy of the current flowing in the high-side sense FET 136-2 and a copy of the current flowing in the OUT HALF_BRIDGE (at the exit of bridge 410) flows, regardless of whether the load current is positive or negative.

[0085] In some examples, a reference voltage, V, is used. ref, which is input into the comparator 406, is fixed. In other examples, the reference voltage is a variable reference voltage that can be set, together with the 502 mirror ratio, to compensate for any difference in a current ratio between N1, the associated current ratio of the high-side switch 402, and N2, the associated current ratio of the low-side switch 430. For example, the associated current ratio N1 of the high-side switch 402 corresponds to a ratio between the current level of the power transistor 136-1 and a current level of the sensing transistor 136-2. An associated current ratio N2 of the low-side switch 430 corresponds to a ratio between the current level of the power transistor 136-3 and the current level of the sensing transistor 136-4. In some examples, the reference voltage (e.g.,M2-M1 ratio) must be set to compensate for any differences between the associated current ratios N1 and N2 of the high-side switch 402 and the low-side switch 430.

[0086] As in Fig. As shown in Figure 8, the current tracking sensing system 500 includes a resistor network 520 coupled to the comparator 406. The resistor network 520 contains a variable resistor 522 configured to adjust a reference voltage coupled to an input of the comparator 406. The resistor network 520 can be used to adjust the amplitude of the triangular current waveform at output 412 OUT. CUREENT_SENSE during the T ON -phase to reduce. Because the current coming from the OUT connection CURRENT_SENSEDuring this phase, the current flow in circuit 412 is caused by the current follower, which is implemented with the additional comparator 406. This introduces some delays that increase the magnitude of the triangular oscillation. This delay is also due to a low-pass filter located at node V. FEEDBACK A 590 transistor exists. To increase the cutoff frequency of this filter, a 520 resistor network is included because its impedance is much lower than that of transistors M2 and M3. Thus, the size of the triangle wave is reduced.

[0087] The current tracking sensing system 500 can fine-tune differences between the current ratio of the high-side switch 402 and the current ratio of the low-side switch 430, so that the high-side switch 402 and the low-side switch 430 have approximately the same current values ​​when the low-side switch 430 stops operating and the high-side switch 402 starts operating, and vice versa. To fine-tune the mirror ratio between the sensing FET 136-2 and the power FET 136-1 of the high-side switch 402, the mirror ratio between transistors M1 and M2 can be fine-tuned by changing the size or "width" of either transistor M1 or M2. In this way, the mirror ratio of the high-side switch 402 and the mirror ratio of the low-side switch 430 can be fine-tuned so that they match.To fine-tune any possible residual offset or the offset caused by changing the mirror ratio between transistors M1 and M2, the reference voltage V can be adjusted. REF The current tracking system 500 can also fine-tune the system in this way to correct any differences due to temperature and / or currents flowing in the power FETs 136-1 and 136-3. The current tracking system 500 provides a practical solution because adjustments can be made to compensate for differences in the mirror ratio. The resistor network 520 can also improve the performance of the current tracking system 500.

[0088] In some examples, the current tracking sensing system 500 is part of a DC-DC converter that relies on the operation of the high-side switch 402 and the low-side switch 430 to produce a power-amplified PWM signal at node 410. A control unit of the DC-DC converter can provide a gate signal for the respective gates of the high-side switch 402 and the low-side switch 430 via drive circuits. The current tracking sensing system 500 includes the current sense output 412, which is connected to the second current mirror 504, configured to provide an output current OUT. CURRENT_SENSE to provide the current at the half-bridge output node 410. That is, the current tracking sensing system 500 can be used to track the load / inductor current of a DC-DC converter to which it is coupled.

[0089] Fig. Figure 9 is a flowchart illustrating an example process 560 for operating a current tracking sensing system configured to track positive and negative currents flowing in both sides of a half-bridge, in accordance with one or more techniques described in this disclosure. Example process 560 can be used to operate devices and techniques described in this disclosure, such as the current tracking sensing systems 400 and 500.

[0090] Process 560 involves operating a half-bridge containing a high-side switch and a low-side switch (562). For example, the current tracking sensing system 400 can rely on the high-side switch 402 and the low-side switch 430 to produce a power-amplified PWM signal at the output node 410.

[0091] Process 560 further includes the control, by means of a comparator, of a first current mirror coupled to the high-side switch and a second current mirror coupled to the low-side switch (564). For example, comparator 406 can produce an output that drives current mirror 504 while high-side switch 402 is turned on and low-side switch 430 is turned off. Alternatively, comparator 406 can drive current mirror 502 while low-side switch 430 is turned on and high-side switch 402 is turned off.

[0092] Fig. Figure 10 is a schematic diagram illustrating an example current tracking sensing system 300 configured to detect zero crossings of the current in a half-bridge in accordance with one or more techniques described in this disclosure. The current tracking sensing system 300 is configured to track the positive and negative currents flowing in both a high-side switch 132 and a low-side switch 1134 of a half-bridge circuit and to provide a proportional output current according to the direction, e.g., positive current flow or negative current flow, of the current at the half-bridge.

[0093] The current tracking sensing system 300 can track the current even when the switching frequency of the half-bridge driver is very high or with very short T ON - or T OFF-times is operated because it is based on nonlinear circuits and bias circuits. The settling time is reduced when the current direction changes and when the half-bridge switches from operating the high-side switch 132 to operating the low-side switch, and vice versa.

[0094] The current tracking system 300 contains two current switches, the high-side switch 132 and the low-side switch 134, and two main current mirrors, the positive-side tracking current mirror 302 and the negative-side tracking current mirror 304. The current tracking system 300 contains three comparators that drive several switches, which control the charging and discharging of two capacitors using current sources. The current tracking system 300 contains the high-side comparator 140-1, the low-side comparator 140-2, and the zero-crossing comparator 306. The positive-side tracking main current mirror 302 contains five transistors, MP1 through MP5 inclusive. Similarly, the negative-side tracking main current mirror 304 contains five transistors, MN1 through MN5 inclusive.

[0095] An example operation of the current tracking sensing system 300 is as follows. When the low-side switch 134 is turned on (signal “GL” is high), the low-side comparator 140-2 controls one of the main current mirrors, depending on the zero-crossing comparator 306. If the current direction is positive, MN5 will be connected as a diode to ensure that the negative main current mirror 304 is biased in a sleep state. The active current mirror in this example, the positive main current mirror 302, can compensate for the offset that the negative main current mirror 304 adds to three summing nodes. One summing node contains MN1 and MP1 and is connected to the sensing transistor 136-4 in the low-side switch 134. The second summing node contains MN2 and MP2 and is connected to a replica current, I out_replicaA third summing node, which can be the output of the current tracking sensing system, contains MN4 and MP4 and is connected to the input of a zero-crossing current comparator. Similarly, the same will be done for the negative current direction: MP5 will be connected as a diode, and MN5 will no longer be, and the negative main current mirror 304 will be actively controlled by the low-side comparator 140-2. Transistors MP4 and MN4 operate as mirrors of the current MP1 and MN1.

[0096] The zero-crossing comparator 306 measures the voltage at a summing node connected to a current source transistor from each of the two main current mirrors 302 and 304. In the example of Fig. At 10, the zero-crossing comparator 306 is connected to MN4 and MP4. When a load current at switching node 390 approaches zero and eventually changes direction, a voltage potential at the summing node between MN4 and MP4 changes. If the change in current direction is from positive to negative, the zero-crossing comparator 306 detects the change and directs control from the positive main current mirror 302 to the negative main current mirror 304. Similarly, if the change in current direction is from negative to positive, the zero-crossing comparator 306 detects the change and directs control from the negative main current mirror 304 to the positive main current mirror 302.

[0097] When the half-bridge switches from operating the low-side switch 134 to operating the high-side switch 132, or vice versa, the current sensor uses the same main current source to track current through both the low-side switch 134 and the high-side switch 132, provided the load current direction in the inductive load is the same. Only the control comparator, 140-1 or 140-2, is changed depending on which switch (high-side switch 132 or low-side switch 134) is being sensed. Whichever main current mirror of the current tracking sensing system 300 is currently inactive is biased and provides a fixed base / offset current for the three summing nodes between current mirrors 302 and 304 and a fourth summing node between high-side current mirrors 308 and 310.Thus, the inactive main current mirror with reduced settling time is ready to operate as soon as the zero-crossing comparator 306 detects a zero current crossing.

[0098] If the current in the load connected to node 390 changes direction, a second complementary main current source is activated, and the first current source is parked in a kind of sleep mode. Again, the same main current source is used for both the high-side switch 132 and the low-side switch 134. The outputs of the two main current sources are summed at the sensing transistors 136-4 and 136-2, the current copy output and the current zero-crossing comparator input, respectively. While one main current source is active, the other is in a kind of sleep mode. During this sleep mode, the current source is biased to supply a small base / offset current. This base / offset current ensures that current source activation will be fast to minimize oscillation / overshoot at the transition between the two current sources.This offset current is compensated by the active current source and therefore will not affect the static accuracy of the copy current. Since the transfer between the two main current sources is performed at near zero load current, and the second main current source is biased and supplies current to the sensing transistors and copy output current, any hysteresis in the zero-crossing comparator 306 can be handled and is useful for minimizing switching.

[0099] When a transition occurs from the low-side switch 134 to the high-side switch 132, the GL signal goes low, followed by a GH signal going high. To ensure a smooth transition from the low-side switch 134 to the high-side switch 132, the same main current mirror is used; only the control of the current mirror is changed from the low-side comparator 140-2 to the high-side switch 140-1. The summing node, which is used to bias the source of the sensing FET 136-2, has a mirror of the current from the negative main current mirror 304 and the positive main current mirror 302. The current tracking sensing system 300 further includes two additional current mirrors, the high-side current mirror for positive currents 308 and the high-side current mirror for negative currents 310. The high-side current mirror for positive currents 308 contains the transistors MN6 and MN7.The high-side current mirror for negative currents 310 contains transistors MP6 and MP7. Both current mirrors MN6 and MN7, as well as MP6 and MP7, are in . Fig. Figure 10 is shown as a classic current mirror. These current mirrors may have some bandwidth limitations. In some examples, additional techniques and circuits described here, such as those from Fig. 11A and Fig. 11B, are applied to speed up the current mirrors. Since these additional high-side current mirrors, 308 and 310, are active even when the low-side switch 134 is turned on and the same main current mirror is used, all transfers between the low-side switch 134 and the high-side current mirror 132, and vice versa, can be seamless.

[0100] When the low-side switch 134 and the high-side switch 132 are both switched off (that is, when transistors 136 are switched off) and the current is zero, both main current mirrors 302 and 304 can be put into a "sleep" mode by connecting both MN5 and MP5 as diodes. This can allow for a fast start-up when the current tracking system 300 becomes active again.

[0101] The value of the controlled current sources and the capacitor size can be chosen by the designer to meet the system's speed requirements. In some examples, the techniques and circuits described here for positive and negative current tracking can be used with linear current tracking systems. Furthermore, all the devices and circuits described here can be used in combination.

[0102] In summary, one difference between the current sensing system 400 from Fig. 6 and the current sensing system 300 from Fig. 10. The current sensing system 400 is a Class A current sensing system and therefore uses a simple offset current generator for the negative current, which is set to supply the maximum negative current that might be required. Thus, when a positive current is required, the system must supply a compensating current for the offset current generator plus the current representing the required / sensed positive current. The current sensing system 300 is a Class AB current sensing system, and it supplies either a negative current or a positive current, depending on the direction of the sensed current, with only a small current offset in each direction to smooth the transition between the negative and positive current directions. To accomplish this, the current sensing system 300 requires the ability to detect when the polarity of the current changes.

[0103] Fig. 11A and Fig. Figure 11B are schematic diagrams illustrating active current mirrors 1308 and 1310 for use in an example current tracking sensing system in accordance with one or more techniques described in this disclosure. For the sake of simplicity, the Fig. 11A and Fig. 11B in the context of System 300 Fig. 10 described.

[0104] The current mirrors 308 and 310 of Fig. The 10 current mirrors are conventional current mirrors. These current mirrors can have a limited bandwidth and may not be fast enough to track changes in the current flowing through sensing FETs 136-2 and 136-4. Active current mirrors 1308 and 1310 can be used to overcome the limitations of the conventional current mirrors 308 and 310.

[0105] Active current mirrors 1308 and 1310 from 12A and 12B contain circuits 1322 and 1320, respectively. The current mirror 308 from Fig. 10 can be replaced by the current mirror 1308, and the current mirror 310 from Fig. Transistor 10 can be replaced by the current mirror 1310. The transistors MP3, MP6, MP7, MN3, MN6 and MN7, which are in the Fig. 11A and Fig. The transistors shown in 11B are the same as transistors MP3, MP6, MP7, MN3, MN6 and MN7 which are in Fig. Figures 10 are shown. Although not shown, the active current mirrors 1308 and 1310 could also form a resistance network similar to the resistance network 520 of Fig. 8 included, which has an input for each of the in Fig. 11A and Fig. The respective comparators shown in 11B are coupled.

[0106] If the voltage V ref When the voltage is stable, the comparators of circuit 1322 control the switches of circuit 1322 to ensure that the current flowing through transistors MN7 is at the same level as the current flowing through MP3. Similarly, when the voltage V refOnce stable, the comparators of circuit 1320 control the switches of circuit 1320 to ensure that the current flowing through transistor MP7 is at the same level as the current flowing through MN3. In this way, the active current mirrors 1308 and 1310 can be used to overcome the disadvantages of the classic current mirrors 308 and 310, as they can be fast enough to track changes in the current flowing through the sensing FETs 136-2 and 136-4.

[0107] The examples described here can be used in a wide range of applications. Such applications may include, for example, DC-DC converters, which may include step-down converters, such as the core voltage (“Vcore”) of a central processing unit (“CPU”) for a desktop or server, and non-Vcore step-down converters, single-phase load point (“POL”) applications, multi-phase POL applications, and high-power-density voltage regulator modules (“VRM”). Furthermore, some of the examples described here may be used in CPU or graphics processing unit (“GPU”) regulation in notebooks, desktop graphics cards, double-rate memory (“DDR” memory), or graphics memory. Additionally, the devices and techniques described here may be used in any application that employs half-bridges or full-bridges.

[0108] Fig.Figure 12 is a flowchart that presents an example process 360 for operating a current tracking sensing system having bidirectional sensing, in accordance with one or more techniques described in this disclosure. Example process 360 can be used to operate devices and techniques presented in this disclosure, such as the current tracking sensing system 300.

[0109] Process 360 includes operating a half-bridge comprising a high-side switch and a low-side switch (362). For example, the current tracking sensing system is a half-bridge comprising the high-side switch 132 and the low-side switch 134. Process 360 further comprises detecting, by means of a current zero-crossing comparator, a zero crossing of a current in the half-bridge at a node between a main current mirror for positive currents and a main current mirror for negative currents, wherein one of the main current mirrors for positive currents or a main current mirror for negative currents is an active current mirror and the other is an inactive current mirror (364). For example, the current zero-crossing comparator 306 detects a zero crossing of a current in the current tracking sensing system 300 between the main current mirror for positive currents 302 and the main current mirror for negative currents 304.

[0110] Process 360 further includes, in response to the detection of the current's zero crossing, switching the active current mirror to inactive and the inactive current mirror to active (366). While the current is negative, the main current mirror for negative currents 304 is active and the main current mirror for positive currents 302 is inactive. Similarly, while the current is positive, the main current mirror for positive currents 302 is active and the main current mirror for negative currents 304 is inactive. For example, in response to the current zero-crossing comparator 306 detecting a current zero crossing from a negative current to a positive current, the current tracking sensing system 300 activates the main current mirror for positive currents 302 and deactivates the main current mirror for negative currents 304.Similarly, in response to the current zero-crossing comparator 306 detecting a zero crossing of the current from a positive current to a negative current, the current tracking sensing system 300 activates the main current mirror for negative currents 304 and deactivates the main current mirror for positive currents 302.

[0111] In another example, process 360 involves detecting either a positive or a negative current (e.g., whether a current is positive or negative) at an output of the half-bridge. In some examples, if both the high-side switch and the low-side switch of the half-bridge are off, then, in response to the fact that both the high-side and low-side switches are off, the logic can put both the main current mirror for positive currents 302 and the main current mirror for negative currents 304 into a sleep state. In other examples, if either the high-side switch 132 or the low-side switch 134 is on and the current is zero, then the current tracking system 300 can switch back and forth between the positive current mirror 302, which is active, and the negative current mirror 304, which is inactive.

[0112] Term 1. Current tracking sensing system comprising: a first current tracking system configured to replicate a first current flowing through a first switch; a second current tracking system configured to replicate a second current flowing through a second switch; and a biasing device configured to: bias the second current tracking system based on first information detected at the first current tracking system indicating the first current; and bias the first current tracking system based on second information detected at the second current tracking system indicating the second current.

[0113] Term 2. Current tracking sensing system according to Term 1, wherein the second information specifies a respective level of the second current and / or a respective polarity of the second current and the first information specifies a respective level of the first current and / or a respective polarity of the first current.

[0114] Term 3. Current tracking sensing system according to any one of terms 1-2, wherein the biasing device is further configured to: receive the first information from the first current tracking system while the first current tracking system replicates the first current; and receive the second information from the second current tracking system while the second current tracking system replicates the second current.

[0115] Term 4. Current tracking sensing system according to any one of terms 1-3, wherein the biasing device is further configured: to receive the first information from the first current tracking system while the second current tracking system refrains from replicating the second current; and to receive the second information from the second current tracking system while the first current tracking system refrains from replicating the second current.

[0116] Term 5. Current tracking sensing system according to any one of terms 1-4, wherein the biasing device is further configured to: bias the second current tracking system at a first current level corresponding to a respective level of the first current; and bias the first current tracking system at a second current level corresponding to a respective level of the second current.

[0117] Term 6. Current tracking sensing system according to any of terms 1-5, wherein the biasing device is further configured to: bias the second current tracking system based on the first information in response to the first current flowing in any direction; and bias the first current tracking system based on the second information in response to the second current flowing in any direction.

[0118] Term 7. Current tracking sensing system according to any of terms 1-6, wherein the biasing device is further configured to: bias the second current tracking system based on the first information in response to the fact that the first current flows in only one direction; and bias the first current tracking system based on the second information in response to the fact that the second current flows in only one direction.

[0119] Term 8. Current tracking sensing system according to any of terms 1-7, wherein: the first current tracking system is configured to replicate the first current flowing through the first switch, while the second current is a first forward current or a first reverse current; and / or the second current tracking system is configured to replicate the second current flowing through the second switch, while the second current is a second forward current or a second reverse current.

[0120] Term 9. Current tracking sensing system according to any of terms 1-8, wherein the first switch is a high-side switch of a half-bridge and the second switch is a low-side switch of the half-bridge.

[0121] Term 10. Current tracking sensing system according to Term 9, wherein the half-bridge is assigned to a switching power converter which outputs power to an inductive load.

[0122] Term 11. Method comprising: receiving at a biasing device of information detected by a first current tracking sensing system indicating a first current flowing through a first switch; and biasing by the biasing device based on the information from a second current tracking sensing system configured to replicate a second current flowing through a second switch.

[0123] Term 12. Method according to Term 11, wherein the information specifies a respective level of the first current and / or a respective polarity of the first current.

[0124] Term 13. Method according to any of terms 11-12, wherein the information is first information and the method further comprises: receiving at the biasing device of second information detected by the second current tracking sensing system and indicating the second current flowing through the second switch; and biasing by the biasing device based on the second information from the first current tracking sensing system.

[0125] Term 14. Method according to any of terms 11-13, wherein the information is received from the first current tracking system while the first current tracking system replicates the first current.

[0126] Term 15. Method according to Term 14, wherein the information is received from the first current tracking system, while the second current tracking system refrains from replicating the second current.

[0127] Term 16. Method according to any of terms 11-15, wherein the biasing of the second current tracking system comprises biasing the second current tracking system at a current level corresponding to a level of the first current.

[0128] Term 17. Current tracking sensing system according to any of terms 11-16, wherein the biasing of the second current tracking sensing system comprises biasing the second current tracking sensing system in response to the first current flowing in any direction.

[0129] Term 18. Current tracking sensing system according to any of terms 11-17, wherein the current tracking system is configured to replicate the second current flowing through the second switch, where the second current is a forward current or a reverse current.

[0130] Term 19. Current tracking sensing system according to any of terms 11-18, wherein the first switch is a high-side switch of a half-bridge and the second switch is a low-side switch of the half-bridge, the half-bridge being associated with a switching power transformer which outputs power to an inductive load.

[0131] Term 20. Current tracking sensing system comprising: means for replicating a first current flowing through a first switch; means for replicating a second current flowing through a second switch; and means for biasing the second current tracking system based on first information received from the first current tracking system specifying the first current; and means for biasing the first current tracking system based on second information received from the second current tracking system specifying the second current.

Claims

[1] Current tracking sensing system (300; 400; 500) comprising the following: a first current tracking system configured to replicate a first current flowing through a first switch (132; 402); a second current tracking system configured to replicate a second current flowing through a second switch (134; 430); and a preloading device comprising at least one comparator (306; 406), wherein the preloading device is configured as follows: to bias the second current tracking system based on initial information detected by the first current tracking system, which indicates the initial current; and The first current tracking system is biased based on second information detected at the second current tracking system, which indicates the second current. [2] Current tracking sensing system (300; 400; 500) according to claim 1, wherein the second information specifies a respective level of the second current and / or a respective polarity of the second current and the first information specifies a respective level of the first current and / or a respective polarity of the first current. [3] Current tracking sensing system (300; 400; 500) according to claim 1 or 2, wherein the biasing device is further configured as follows: to receive the first information from the first current tracking system while the first current tracking system replicates the first current; and to receive the second set of information from the second current tracking system, while the second current tracking system replicates the second current. [4] Current tracking sensing system (300; 400; 500) according to one of claims 1 to 3, wherein the biasing device is further configured: to receive the first information from the first current tracking system, while the second current tracking system refrains from replicating the second current; and to receive the second set of information from the second current tracking system, while the first current tracking system refrains from replicating the first current. [5] Current tracking sensing system (300; 400; 500) according to any one of claims 1 to 4, wherein the biasing device is further configured: to bias the second current tracking system at a first current level corresponding to a respective level of the first current; and to bias the first current tracking system at a second current level, which corresponds to a respective level of the second current. [6] Current tracking sensing system (300; 400; 500) according to any one of claims 1 to 5, wherein the biasing device is further configured: to bias the second current tracking system based on the first information in response to the fact that the first current flows in any direction; and to bias the first current tracking system based on the second information in response to the fact that the second current flows in any direction. [7] Current tracking sensing system (300; 400; 500) according to any one of claims 1 to 6, wherein the biasing device is further configured: to bias the second current tracking system based on the first information in response to the fact that the first current flows in only one direction; and to pre-tension the first current tracking system based on the second information in response to the fact that the second current flows in only one direction. [8] Current tracking sensing system (300; 400; 500) according to any one of claims 1 to 7, wherein: the first current tracking system is configured to replicate the first current flowing through the first switch (132; 402), where the first current is either a first forward current or a first reverse current; and / or the second current tracking system is configured to replicate the second current flowing through the second switch (134; 430), where the second current is either a second forward current or a second reverse current. [9] Current tracking sensing system (300; 400; 500) according to any one of claims 1 to 8, wherein the first switch (132; 402) is a high-side switch of a half-bridge and the second switch (134; 430) is a low-side switch of the half-bridge. [10] Current tracking sensing system (300; 400; 500) according to claim 9, wherein the half-bridge is associated with a switching power converter which outputs power to an inductive load. [11] Procedure comprising the following: Receiving at a biasing device of information detected by a first current tracking sensing system, indicating a first current flowing through a first switch (132; 402); and Pre-tensioning by the pre-tensioning device based on information from a second current tracking sensing system configured to replicate a second current flowing through a second switch (134; 430), wherein the pre-tensioning device includes at least one comparator (306; 406). [12] Method according to claim 11, wherein the information specifies a respective level of the first current and / or a respective polarity of the first current. [13] Method according to claim 11 or 12, wherein the information is first information and the method further comprises: Receiving at the biasing device second information, detected by the second current tracking sensing system, indicating the second current flowing through the second switch (134; 430); and Pre-tensioning by the pre-tensioning device based on the second set of information from the first current tracking sensing system. [14] Method according to any one of claims 11 to 13, wherein the information is received from the first current tracking system while the first current tracking system replicates the first current. [15] Method according to claim 14, wherein the information is received from the first current tracking system, while the second current tracking system refrains from replicating the second current. [16] Method according to any one of claims 11 to 15, wherein the biasing of the second current tracking sensing system comprises biasing the second current tracking sensing system at a current level corresponding to a level of the first current. [17] Method according to any one of claims 11 to 16, wherein the biasing of the second current tracking sensing system comprises biasing the second current tracking sensing system in response to the first current flowing in any direction. [18] Method according to any one of claims 11 to 16, wherein the current tracking system is configured to replicate the second current flowing through the second switch (134; 430), where the second current is a forward current or a reverse current. [19] Method according to any one of claims 11 to 16, wherein the first switch (132; 402) is a high-side switch of a half-bridge and the second switch (134; 430) is a low-side switch of the half-bridge, wherein the half-bridge is associated with a switching power converter which outputs power to an inductive load. [20] Current tracking sensing system (300; 400; 500) comprising the following: Means for replicating a first current flowing through a first switch (132; 402); Means for replicating a second current flowing through a second switch (134; 430); and Means for biasing the second current tracking system based on initial information received from the first current tracking system, indicating the first current; and Means for biasing the first current tracking system based on second information received from the second current tracking system, which specifies the second current; wherein the means for biasing the first current tracking system and the means for biasing the second current tracking system comprise means for comparing two voltages. [21] Current tracking sensing system (300; 400; 500) according to any one of claims 1 to 9, wherein the biasing device further comprises a first current mirror (302, 502) and a second current mirror (304, 504), wherein the biasing device is further configured: to control the second current mirror (304; 504) by the comparator (306; 406) such that the second current tracking system is biased based on initial information detected at the first system, which indicates the first current; and to control the first current mirror (302; 502) by the comparator (306; 406) so that the first current tracking system is biased based on second information detected at the second system and indicating the second current. [22] Method according to any one of claims 11 to 19, wherein the pre-tensioning comprises: Control by the comparator (306; 406) of a current mirror (302, 502) of the biasing device, so that the second system is biased based on the information. [23] Current tracking sensing system (300; 400; 500) according to claim 20, wherein the means for biasing the second current tracking system comprises means for controlling a second current mirror, such that the second current tracking system is biased based on the first information; wherein the means for biasing the first current tracking system comprises means for controlling a first current mirror, such that the first current tracking system is biased based on the second information.

Images