Adaptive threshold control system for detecting and adjusting the duration of the operating region during transistor turn-on and turn-off

Abstract

An adaptive threshold control system for detecting and adjusting the duration of the operating regions during transistor turn-on and turn-off is disclosed. A system includes a buffer circuit (310) coupled to a comparator (320) and an adaptive threshold control circuit (350) coupled to a timer (355) and the comparator. The buffer circuit receives a first voltage across a control terminal and a first current terminal of a transistor and a second voltage across a second current terminal and the first current terminal of the transistor. The comparator compares the first voltage to a first threshold, generating a first trigger signal (325) when it crosses the first threshold, and compares the second voltage to a second threshold, generating a second trigger signal (330) when it crosses the second threshold. The timer determines the length of time between the trigger signals. The adaptive threshold control circuit generates a first control signal (360) for the first trigger signal and a second control signal for the second trigger signal, and provides a control signal (365) to the comparator indicating whether the length of time is greater than or less than a user programmed value, causing the comparator to adjust the first threshold.

Description

Background Technology

[0001] An H-bridge driver comprises two high-side transistors and two low-side transistors, configured such that each high-side transistor is connected in series with a corresponding low-side transistor, and a load is coupled to a node between the high-side and low-side transistor pairs. Each pair of high-side and low-side transistors is called a half-bridge. Gate driver circuitry converts a control signal into a power signal that can efficiently turn each transistor in the H-bridge driver on and off. To prevent shoot-through conditions within the half-bridge during high-to-low or low-to-high transitions, a dead time is inserted between the off state of one transistor and the on state of the other. The length of the dead time is typically equal to the time required to turn the transistors in the half-bridge driver on or off. However, the dead time limits the operating frequency of the H-bridge driver and allows for power dissipation through the transistors in the H-bridge driver.

[0002] Some gate driver circuits reduce power dissipation during dead time by turning transistors on and off faster. This can increase the efficiency of H-bridge drivers, but at the cost of generating electromagnetic interference (EMI) in the integrated circuit (IC), which can disrupt the operation of other circuitry within the IC. Some gate driver circuits balance the need for fast turn-on and turn-off times with controlled EMI by implementing comparators to detect different operating regions of each transistor during turn-on and turn-off, accelerating only the regions less likely to cause EMI. However, these comparators must be tuned for each transistor, system voltage, motor type, board parasitic capacitance, etc., and often experience performance degradation over time as system parameters change (e.g., with variations in temperature or supply voltage). Summary of the Invention

[0003] An adaptive threshold control system includes a buffer circuit, a comparator circuit, a timer circuit, and an adaptive threshold control circuit. The buffer circuit is configured to be coupled to a transistor such that it receives a first voltage across a control terminal and a first current terminal of the transistor, and a second voltage across a second current terminal and the first current terminal. The comparator circuit is coupled to the buffer circuit and configured to compare the first voltage with a first threshold and generate a first trigger signal in response to the first voltage crossing the first threshold. The comparator circuit is also configured to compare a second voltage with a second threshold and generate a second trigger signal in response to the second voltage crossing the second threshold. The timer circuit is configured to determine a time length between the first and second trigger signals. The adaptive threshold control circuit is coupled to the comparator circuit and the timer circuit. The adaptive threshold control circuit is configured to generate a first control signal in response to the first trigger signal and a second control signal in response to the second trigger signal. The adaptive threshold control circuit is also configured to provide a third control signal to the comparator circuit. The third control signal indicates whether the time length is greater than or less than a user-programmed value and causes the comparator circuit to adjust the first threshold. In some implementations, the first control signal and the second control signal cause the gate driver circuit of the transistor to adjust the drive current.

[0004] When the transistor is turned on, the comparator circuit is configured to increase a first threshold in response to a third control signal indicating a time length greater than a user-programmed value, and to decrease the first threshold in response to a third control signal indicating a time length less than a user-programmed value. When the transistor is turned on, the comparator circuit is configured to generate a first trigger signal in response to a first voltage increasing above the first threshold. In some embodiments, the transistor is a low-side transistor in a half-bridge circuit, and the comparator circuit is configured to generate a second trigger signal in response to a second voltage decreasing below a second threshold. In other embodiments, the transistor is a high-side transistor in a half-bridge circuit, and the comparator circuit is configured to generate a second trigger signal in response to a second voltage increasing above the second threshold.

[0005] When the transistor is off, the comparator circuit is configured to decrease the first threshold in response to a third control signal indicating a time length greater than a user-programmed value, and to increase the first threshold in response to a third control signal indicating a time length less than a user-programmed value. When the transistor is off, the comparator circuit is configured to generate a first trigger signal in response to a first voltage decreasing to below the first threshold. In some embodiments, the transistor is a low-side transistor in a half-bridge circuit, and the comparator circuit is configured to generate a second trigger signal in response to a second voltage increasing to above a second threshold. In other embodiments, the transistor is a high-side transistor in a half-bridge circuit, and the comparator circuit is configured to generate a second trigger signal in response to a second voltage decreasing to below a second threshold. Attached Figure Description

[0006] For a detailed description of the various examples, reference will now be made to the accompanying drawings, in which:

[0007] Figure 1 An example H-bridge motor driver is shown.

[0008] Figure 2 The diagram illustrates the change in gate-to-source voltage over time for the high-side and low-side transistors in an example H-bridge motor driver.

[0009] Figure 3 An example adaptive threshold control system is shown.

[0010] Figure 4 The diagram illustrates the drain-to-source voltage of the low-side transistor in an example H-bridge motor driver during transistor conduction, the drain current through the low-side transistor, the gate-to-source voltage of the low-side transistor, and the drive current applied to the gate of the low-side transistor.

[0011] Figure 5 The diagram illustrates the drain-to-source voltage of the high-side transistor in an example H-bridge motor driver during transistor conduction, the drain current through the high-side transistor, the gate-to-source voltage of the high-side transistor, and the drive current applied to the gate of the high-side transistor.

[0012] Figure 6 The diagram illustrates the drain-to-source voltage of the low-side transistor in an example H-bridge motor driver during transistor cutoff, the drain current through the low-side transistor, the gate-to-source voltage of the low-side transistor, and the drive current applied to the gate of the low-side transistor.

[0013] Figure 7 The diagram illustrates the drain-to-source voltage of the high-side transistor in an example H-bridge motor driver during transistor cutoff, the drain current through the high-side transistor, the gate-to-source voltage of the high-side transistor, and the drive current applied to the gate of the high-side transistor. Detailed Implementation

[0014] As described above, as system parameters change, such as temperature or supply voltage, gate driver circuitry implementing comparators to detect different operating regions of the transistor during turn-on and turn-off experiences performance degradation over time. The disclosed circuitry detects different operating regions of the transistor during turn-on and turn-off based on an adjustable threshold that can change in response to variations in system parameters (e.g., temperature or supply voltage). The adjustable threshold is adjusted to maintain the user-programmed duration for applying a user-programmed drive current. This allows the user to customize the operation of the H-bridge driver based on the specific EMI requirements of the implementation without compromising efficiency.

[0015] The disclosed example adjustable threshold control system includes a buffer circuit coupled to a transistor in an H-bridge driver, such that the buffer circuit receives the gate-to-source voltage (Vgs) and drain-to-source voltage (Vds) of the transistor. A comparator circuit coupled to the buffer circuit is configured to compare Vgs with a first threshold and generate a first trigger signal in response to Vgs crossing the first threshold. The comparator circuit is also configured to compare Vds with a second threshold and generate a second trigger signal in response to Vds crossing the second threshold. An adaptive threshold control circuit coupled to the comparator circuit generates a first control signal for a gate driver circuit in response to the first trigger signal and a second control signal for the gate driver circuit in response to the second trigger signal. The gate driver circuit adjusts the drive current based on the first and second control signals.

[0016] The adaptive threshold control circuit is also coupled to a timer circuit that determines the duration between the first and second trigger signals. The adaptive threshold control signal compares the duration with a user-programmed value and provides a third control signal to the comparator circuit in response to the duration being greater than the user-programmed value, and a fourth control signal to the comparator circuit in response to the duration being less than the user-programmed value. The comparator circuit adjusts the first threshold based on the third and fourth control signals.

[0017] When the transistor is turned on, the comparator circuit increases a first threshold in response to a time duration greater than the user-programmed value, and decreases the first threshold in response to a time duration less than the user-programmed value. The comparator circuit generates a first trigger signal in response to Vgs increasing above the first threshold. If the transistor is a low-side transistor in the H-bridge driver, the comparator circuit generates a second trigger signal in response to Vds decreasing below a second threshold. If the transistor is a high-side transistor in the H-bridge driver, the comparator circuit generates a second trigger signal in response to Vds increasing above the second threshold.

[0018] When the transistor is off, the comparator circuit decreases the first threshold in response to a time duration greater than the user-programmed value, and increases the first threshold in response to a time duration less than the user-programmed value. The comparator circuit generates a first trigger signal in response to Vgs decreasing below the first threshold. If the transistor is a low-side transistor in the H-bridge driver, the comparator circuit generates a second trigger signal in response to Vds increasing above a second threshold. If the transistor is a high-side transistor in the H-bridge driver, the comparator circuit generates a second trigger signal in response to Vds decreasing below the second threshold.

[0019] Figure 1 An example H-bridge motor driver 100 is shown. Although Figure 1An H-bridge implemented as a motor driver is shown, but the H-bridge and gate driver circuitry described herein can be used in a variety of applications, including other types of power electronics. An example H-bridge motor driver 100 includes high-side power field-effect transistors (FETs) M_HS1 and M_HS2 and low-side power FETs M_LS1 and M_LS2. The source terminal of M_HS1 is coupled to the drain terminal of M_LS1 at node 115, forming a half-bridge configuration. The source terminal of M_HS2 is coupled to the drain terminal of M_LS2 at node 135, forming another half-bridge configuration. The drain terminals of M_HS1 and M_HS2 are coupled to receive the supply voltage Vmotor at node 105. The source terminals of M_LS1 and M_LS2 are coupled to receive a common-mode voltage at node 160. In some examples, the common-mode voltage at node 160 is ground. Nodes 115 and 135 form the output nodes of the H-bridge motor driver 100, and load 150 is coupled to nodes 115 and 135.

[0020] The gate terminal of each of M_HS1, M_LS1, M_HS2, and M_LS2 is coupled to a corresponding gate driver circuit. The gate terminal of M_HS1 is coupled to receive gate drive current from gate driver circuit 110. The gate terminal of M_LS1 is coupled to receive gate drive current from gate driver circuit 120. The gate terminal of M_HS2 is coupled to receive gate drive current from gate driver circuit 130. The gate terminal of M_LS2 is coupled to receive gate drive current from gate driver circuit 140.

[0021] The H-bridge motor driver 100 includes metal-oxide-semiconductor field-effect transistors (MOSFETs). In this example, M_HS1, M_LS1, M_HS2, and M_LS2 are n-type MOSFETs (NMOS). In other examples, one or more of M_HS1, M_LS1, M_HS2, and M_LS2 are p-type MOSFETs (PMOS) or bipolar junction transistors (BJTs). A BJT includes a base, a collector, and an emitter. The base of the BJT and the gate of the MOSFET are also referred to as control inputs or control terminals. The collector and emitter of the BJT, as well as the drain and source of the MOSFET, are also referred to as current terminals.

[0022] Figure 2The diagram illustrates the time-varying gate-to-source voltages Vgs_HS 210 and Vgs_LS 220 of M_HS1 and M_LS1 in an example H-bridge motor driver 100. To prevent shoot-through current, the switching scheme controlling M_HS1 and M_LS1 includes a dead time 250, during which neither the high-side transistor M_HS1 nor the low-side transistor M_LS1 is turned on. This ensures that M_HS1 is completely turned off before M_LS1 turns on. As previously mentioned, the dead time 250 slows down the achievable switching frequency of the H-bridge motor driver 100 and increases the power dissipated through the H-bridge motor driver 100. To address this issue, some motor drivers increase the slew rate, i.e., the speed at which the transistor turns on and off, thereby reducing propagation delay. An increase in slew rate can also increase EMI and generate noise that interferes with the operation of other circuitry within the IC. Because EMI affects the operation of other circuitry, some gate driver circuits prioritize the IC's slew rate and EMI requirements over the switching frequency.

[0023] Figure 3 An example adaptive threshold control system 300 is shown, which is used to identify, for example, in... Figure 1 The H-bridge motor driver 100 controls the transition between the on and off operating regions of the transistors. An adaptive threshold control system 300 is shown in combination with M_HS1 and M_LS1 and gate driver circuits 110 and 120, but can also be used in combination with M_HS2 and M_LS2 and gate driver circuits 130 and 140. The adaptive threshold control system 300 includes a buffer 310, a comparator 320, and an adaptive threshold control sub-circuit 350. The buffer 310 is coupled to various points in the H-bridge motor driver 100 such that the gate-to-source voltage (Vgs) and drain-to-source voltage (Vds) of both M_HS1 and M_LS1 can be determined. The buffer 310 is coupled to the drain of M_HS1 at node 105, coupled to the gate of M_HS1, coupled to the source of M_HS1 and the drain of M_LS1 at node 115, coupled to the gate of M_LS1, and coupled to the source of M_LS1 at node 160. The buffer is used to ensure that the adaptive threshold control system 300 does not contribute load to the H-bridge motor driver 100.

[0024] Comparator 320 is coupled to buffer 310 and receives Vgs and Vds from M_HS1 and M_LS1. Comparator 320 compares Vgs with an adaptive threshold voltage Vth and Vds with a cross threshold Vcrossing. The value of Vth can be adjusted based on a control signal from adaptive threshold control subcircuit 350. The value of cross threshold Vcrossing represents the voltage change in Vds, indicating that the transistor has transitioned from one operating region to another during turn-on and turn-off. Adaptive threshold control subcircuit 350 is coupled to comparator 320 and receives the comparison results between Vgs and Vth, and between Vds and Vcrossing. Adaptive threshold control subcircuit 350 includes a timer 355 that determines the length of time between Vgs crossing Vth and Vds crossing Vcrossing.

[0025] The adaptive threshold control subcircuit 350 compares a determined time length with a user-programmed value indicating the duration for which a specific gate current should be applied. If the determined time length is greater than or less than the programmed value, the adaptive threshold control subcircuit 350 generates a control signal and sends it to comparator 320, indicating an adjustment to the adaptive threshold voltage Vth. This allows the adaptive threshold control system 300 to adjust to changes in system parameters over time, such as as the FET temperature increases. The adaptive threshold control subcircuit 350 also generates control signals for gate drivers 110 and 120, indicating the drive current to be applied to the gates of M_HS1 and M_LS1. (See previous reference...) Figure 2 As discussed, M_HS1 and M_LS1 are not turned on at the same time; therefore, the adaptive threshold control system 300 receives only the value for one of M_HS1 and M_LS1 at a time. This allows the adaptive threshold control system 300 to implement unique comparison and control signals for each of M_HS1 and M_LS1, and for turning on and off, which will refer to... Figures 4 to 7 Further discussion.

[0026] Figure 4 This shows the transistor during conduction. Figure 1The example H-bridge motor driver 100 shows the drain-to-source voltage (Vds) of the low-side transistor M_LS1, the drain current (Idrain) through M_LS1, the gate-to-source voltage (Vgs) of M_LS1, and the drive current (Idrive) applied to the gate of M_LS1. Region 405 is the transistor conduction region, where the gate-to-source capacitance Cgs of M_LS1 is charged to the threshold voltage Vth. When Vgs 450 is greater than Vth, the transistor conducts current and Idrain 440 begins to increase. The length of region 405 depends on the drive current Idrive and the threshold voltage Vth, which can vary based on system parameters such as temperature, battery supply voltage, etc.

[0027] Region 410 is the dIdt region, where Idrain 440 increases and Vgs 450 increases to the Miller voltage (Vmiller). The duration of time in the dIdt region 410 depends on the drive current Idrive and the load 150 on the H-bridge motor driver 100. Variations in Idrain 440 in region 410 can cause EMI or ringing in other circuitry on the IC, including the H-bridge driver. Therefore, the values ​​of Idrive, the rate of increase of Vgs 450, and the rate of increase of Idrain 440 are chosen to keep any EMI or ringing generated in region 410 within acceptable limits for a particular implementation. Region 415 is referred to as the Miller region, where Vgs 450 remains constant and Vds 430 decreases as Cgd charges. Once Cgd is charged, the conduction channel of M_LS1 is fully enhanced by increasing Vgs 450 to the transistor's turn-on voltage in region 420 (referred to as the RDSON enhancement region). Once Vgs 450 reaches the transistor's turn-on voltage and enters region 425, M_LS1 is in the turn-on state.

[0028] Because gate drivers must balance system efficiency with the IC's EMI and ringing limitations, it is helpful to vary the drive current Idrive based on the operating region where M_LS1 is located. For example, decreasing Idrive during region 410 reduces EMI, while increasing Idrive during regions 415 and 420 speeds up transistor turn-on and improves efficiency. This requires determining which operating region M_LS1 is in and what EMI and ringing limitations exist in the IC. The adaptive threshold control system 300 allows the user to program the value of the drive current Idrive 460 in region 410 based on the IC's EMI and ringing requirements, and to program the duration for which the user-programmed value of Idrive 460 is applied.

[0029] Based on the threshold voltage published by the transistor, the user-programmed value of Idrive 460, and the duration for which it is to be applied, the adaptive threshold control system 300 estimates an initial value for the adaptive threshold voltage Vth. Comparator 320 then compares the value of Vgs 450 from buffer 310 with the initial value of the adaptive threshold voltage Vth, and in response to Vgs 450 increasing above the value of Vth, provides a first trigger signal 325 to the adaptive threshold control subcircuit 350. In response to receiving the trigger signal 325, the adaptive threshold control subcircuit 350 generates a control signal 360 and provides it to the gate driver 120, indicating that the drive current generated by the gate driver 120 for M_LS1 during region 410 should be changed to the user-programmed value of Idrive 460.

[0030] Comparator 320 also compares the value of Vds 430 from buffer 310 with Vcrossing, which represents the transition point between regions 410 and 415 for M_LS1 to be on, during which Vds 430 decreases. In response to Vds 430 decreasing below Vcrossing, comparator 320 provides a second trigger signal 330 to adaptive threshold control subcircuit 350. In response to receiving the trigger signal 330, adaptive threshold control subcircuit 350 generates a control signal 360 and provides it to gate driver 120, indicating that the drive current generated by gate driver 120 for M_LS1 during regions 415 and 420 should change to the new value of Idrive 460.

[0031] The adaptive threshold control subcircuit 350 also causes timer 355 to determine the time between receiving the first trigger signal 325 and receiving the second trigger signal 330. In response to the determined time between the first trigger 325 and the second trigger 330 being greater than a user-programmed time length, the adaptive threshold control subcircuit 350 generates a control signal 365 for comparator 320 to increase the adaptive threshold voltage Vth. This allows the higher drive current Idrive 460 during the on-region 405 to be maintained for a longer period before transitioning to the lower Idrive 460 for the dIdt region 410. In response to the determined time between the first trigger 325 and the second trigger 330 being less than a user-programmed time length, the adaptive threshold control subcircuit 350 generates a control signal 365 for comparator 320 to decrease the adaptive threshold voltage Vth. This reduces the time period for the higher Idrive 460 during region 405 and accelerates the transition to the lower Idrive 460 for the dIdt region 410. In this way, the adaptive threshold control system 300 adapts to changes in system parameters (such as temperature and power supply voltage) without manual adjustment.

[0032] Figure 5 This shows the transistor during conduction. Figure 1 The example H-bridge motor driver 100 shows the drain-to-source voltage (Vds), drain current (Idrain), gate-to-source voltage (Vgs), and drive current (Idrive) applied to the gate of the high-side transistor M_HS1. The conduction periods 505-525 of M_HS1 are similar to those of M_LS1 (405-425); however, Vds 530 for M_HS1 increases during transistor conduction and decreases during transistor turn-on. Because the gate driver must balance system efficiency with IC EMI and ringing limitations, it is helpful to vary the drive current Idrive based on the operating region of M_HS1. Just as with M_LS1 conduction, the adaptive threshold control system 300 allows the user to program the value of the drive current Idrive560 of region 510 based on the IC's EMI and ringing requirements, and to program the duration for which the user-programmed value of Idrive560 will be applied.

[0033] Based on the published threshold voltage of the transistor, the user-programmed value of Idrive 560, and the duration for which it is to be applied, the adaptive threshold control system 300 estimates the initial value of the adaptive threshold voltage Vth. Vcrossing for M_HS1 conduction represents the transition point between regions 510 and 515, during which Vds 530 increases. The adaptive threshold control system 300 then, as referenced herein... Figure 4 The operation involves comparing the values ​​of Vgs 550 and Vds 530 with the initial value of the adaptive threshold voltage Vth and Vcrossing, and generating a control signal 360 for the gate driver 110, which indicates a change in Idrive 560 based on the operating region during transistor conduction.

[0034] The adaptive threshold control subcircuit 350 also causes timer 355 to determine the time between receiving the first trigger signal 325 and receiving the second trigger signal 330. In response to the determined time between the first trigger 325 and the second trigger 330 being greater than a user-programmed time length, the adaptive threshold control subcircuit 350 generates a control signal 365 for comparator 320 to increase the adaptive threshold voltage Vth. This allows the higher drive current Idrive 560 during the on-region 505 to be maintained for a longer period before transitioning to the lower Idrive 560 for the dIdt region 510. In response to the determined time between the first trigger 325 and the second trigger 330 being less than a user-programmed time length, the adaptive threshold control subcircuit 350 generates a control signal 365 for comparator 320 to decrease the adaptive threshold voltage Vth. This reduces the time period for the higher Idrive 560 during region 505 and accelerates the transition to the lower Idrive 560 for the dIdt region 510. In this way, the adaptive threshold control system 300 adapts to changes in system parameters (such as temperature and power supply voltage) without manual adjustment.

[0035] Figure 6 This shows the transistor's off period. Figure 1 The example H-bridge motor driver 100 shown illustrates the drain-to-source voltage (Vds) of the low-side transistor M_LS1, the drain current (Idrain) through M_LS1, the gate-to-source voltage (Vgs) of M_LS1, and the drive current (Idrive) applied to the gate of M_LS1. Region 605 is the gate discharge region, during which Vgs 450 decreases as the gate capacitance of M_LS1 discharges to a Miller steady-state level. The gate discharge region is divided into a fast discharge region 610 and a slow discharge region 615. Once the gate voltage reaches a Miller steady-state level, Vds 430 increases as Cgd further discharges. As in region 415, region 620 and the increased Vds 430 can cause EMI and noise in other circuitry on the IC. In region 625 (i.e., the dIdt region), Idrain 440 decreases. In region 630, both Cgs and Cgd are discharged to zero volts, thereby reducing Vgs 450 to zero volts and turning off the transistor. In region 635, M_LS1 is in the off state.

[0036] Because the gate driver must balance system efficiency with the IC's EMI and ringing limitations, it is helpful to vary the drive current Idrive based on the operating region where M_LS1 is located. For example, increasing Idrive during region 605 speeds up transistor turn-off and improves efficiency, while decreasing Idrive during region 620 reduces EMI. This requires determining which operating region M_LS1 is in and what EMI and ringing limitations exist in the IC. The system's detection of a transition to Miller region 620 and the delay in adjusting Idrive 460 in response to the transition can cause system overshoot transitions and EMI in region 620 before Idrive 460 can be reduced for region 620. The adaptive threshold control system 300 allows the user to divide the gate discharge region 605 into a fast discharge region 610 and a slow discharge region 615, thereby slowing the approach to region 620 and providing the system with time to detect the transition point and adjust Idrive 460.

[0037] The adaptive threshold control system 300 allows the user to program the value of the drive current Idrive 460 in region 615 based on the IC's EMI and ringing requirements, and to program the duration for which the user-programmed value of Idrive 460 will be applied. Based on the user-programmed value of Idrive 460 and its duration, the adaptive threshold control system 300 estimates an initial value for the adaptive transition threshold voltage Vtransition. Comparator 320 then compares the value of Vgs 450 from buffer 310 with the initial value of the adaptive transition threshold voltage Vtransition, and in response to Vgs 450 decreasing below the value of Vtransition, provides a first trigger signal 325 to the adaptive threshold control subcircuit 350. In response to receiving the trigger signal 325, the adaptive threshold control subcircuit 350 generates a control signal 360 and provides it to the gate driver 120, indicating that the drive current generated by the gate driver 120 for M_LS1 during region 615 should change to the user-programmed value of Idrive 460.

[0038] Comparator 320 also compares the value of Vds 430 from buffer 310 with Vcrossing, which represents the transition point between regions 615 and 620 for M_LS1 cutoff, during which Vds 430 increases. In response to Vds 430 increasing above Vcrossing, comparator 320 provides a second trigger signal 330 to adaptive threshold control subcircuit 350. In response to receiving the trigger signal 330, adaptive threshold control subcircuit 350 generates a control signal 360 and provides it to gate driver 120, indicating that the drive current generated by gate driver 120 for M_LS1 during regions 620-630 should change to the new value of Idrive 460.

[0039] The adaptive threshold control subcircuit 350 also causes timer 355 to determine the time between receiving the first trigger signal 325 and receiving the second trigger signal 330. In response to the determined time between the first trigger 325 and the second trigger 330 being greater than a user-programmed time length, the adaptive threshold control subcircuit 350 generates a control signal 365 for comparator 320 to decrease the adaptive transition threshold voltage Vtransition. This allows the higher Idrive 460 for the fast discharge region 610 to be maintained for a longer period before transitioning to the lower Idrive 460 for the slow discharge region 615. In response to the determined time between the first trigger 325 and the second trigger 330 being less than a user-programmed time length, the adaptive threshold control subcircuit 350 generates a control signal 365 for comparator 320 to increase the adaptive transition threshold voltage Vtransition. This reduces the time period for the higher Idrive 460 during the fast discharge region 610 and accelerates the transition to the lower Idrive 460 for the slow discharge region 615. In this way, the adaptive threshold control system 300 adapts to changes in system parameters (such as temperature and power supply voltage) without manual adjustment.

[0040] Figure 7 This shows the transistor's off period. Figure 1The example H-bridge motor driver 100 shown illustrates the drain-to-source voltage (Vds) of the high-side transistor M_HS1, the drain current (Idrain) through M_HS1, the gate-to-source voltage (Vgs) of M_HS1, and the drive current (Idrive) applied to the gate of M_HS1. The cutoff and regions 705-730 of M_HS1 are similar to those of M_LS1, however, Vds 530 for M_HS1 decreases during transistor cutoff, while Vds 430 for M_HS1 decreases during transistor cutoff. Because the gate driver must balance system efficiency with EMI and ringing limitations of the IC, it is helpful to vary the drive current Idrive based on the operating region where M_HS1 is located. Delays in detecting the transition to Miller region 720 and adjusting Idrive 560 in response to the transition can cause system overshoot transitions and lead to EMI in region 720 before Idrive 560 for region 720 can be reduced. The adaptive threshold control system 300 allows the user to divide the gate discharge region 705 into a fast discharge region 710 and a slow discharge region 715, thereby slowing down the approach to region 720 and providing the system with time to detect the transition point and adjust Idrive 560.

[0041] The adaptive threshold control system 300 allows the user to program the value of the drive current Idrive 560 in region 715 based on the IC's EMI and ringing requirements, and to program the duration for which the user-programmed value of Idrive 560 will be applied. Based on the user-programmed value of Idrive 560 and its duration of application, the adaptive threshold control system 300 estimates an initial value for the adaptive transition threshold voltage Vtransition. Comparator 320 then compares the value of Vgs 550 from buffer 310 with the initial value of the adaptive transition threshold voltage Vtransition, and in response to Vgs 550 decreasing below the value of Vtransition, provides a first trigger signal 325 to the adaptive threshold control subcircuit 350. In response to receiving the trigger signal 325, the adaptive threshold control subcircuit 350 generates a control signal 360 and provides it to the gate driver 110, indicating that the drive current generated by the gate driver 110 for M_HS1 during region 715 should change to the user-programmed value of Idrive 560.

[0042] Comparator 320 also compares the value of Vds 430 from buffer 310 with Vcrossing, which represents the transition point between regions 715 and 720 for M_HS1 cutoff, during which Vds 530 increases. In response to Vds 530 decreasing below Vcrossing, comparator 320 provides a second trigger signal 330 to adaptive threshold control subcircuit 350. In response to receiving the trigger signal 330, adaptive threshold control subcircuit 350 generates a control signal 360 and provides it to gate driver 110, indicating that the drive current generated by gate driver 110 for M_HS1 during regions 720-630 should change to the new value of Idrive 560.

[0043] The adaptive threshold control subcircuit 350 also causes timer 355 to determine the time between receiving the first trigger signal 325 and receiving the second trigger signal 330. In response to the determined time between the first trigger 325 and the second trigger 330 being greater than a user-programmed time length, the adaptive threshold control subcircuit 350 generates a control signal 365 for comparator 320 to decrease the adaptive transition threshold voltage Vtransition. This allows the higher Idrive 560 for the fast discharge region 710 to be maintained for a longer period before transitioning to the lower Idrive 560 for the slow discharge region 715. In response to the determined time between the first trigger 325 and the second trigger 330 being less than a user-programmed time length, the adaptive threshold control subcircuit 350 generates a control signal 365 for comparator 320 to increase the adaptive transition threshold voltage Vtransition. This reduces the time period for the higher Idrive 560 during the fast discharge region 710 and accelerates the transition to the lower Idrive 560 for the slow discharge region 715. In this way, the adaptive threshold control system 300 adapts to changes in system parameters (such as temperature and power supply voltage) without manual adjustment.

[0044] In this specification, the term "coupled" refers to an indirect or direct wired or wireless connection. Therefore, if a first device is coupled to a second device, the connection can be either a direct connection or an indirect connection via other devices and connections. The term "based on" means "at least partially based on". Therefore, if X is based on Y, then X can be a function of Y and any number of other factors.

[0045] Within the scope of the claims, modifications may be made to the described embodiments, and other embodiments are also possible.

Claims

1. An adaptive threshold control system, comprising: A buffer circuit is configured to be coupled to a transistor such that the buffer circuit receives a first voltage across a control terminal and a first current terminal of the transistor and a second voltage across a second current terminal and the first current terminal of the transistor. The comparator circuit, coupled to the buffer circuit, is configured as follows: The first voltage is compared with the first threshold. A first trigger signal is generated in response to the first voltage crossing the first threshold. Compare the second voltage with the second threshold, and A second trigger signal is generated in response to the second voltage crossing the second threshold; A timer circuit configured to determine the duration of time between the first trigger signal and the second trigger signal; as well as An adaptive threshold control circuit, coupled to the comparator circuit and the timer circuit, wherein the adaptive threshold control circuit is configured to: A first control signal is generated in response to the first trigger signal, and a second control signal is generated in response to the second trigger signal. A third control signal is provided to the comparator circuit to indicate whether the time length is greater than or less than a user-programmed value, wherein the third control signal causes the comparator circuit to adjust the first threshold.

2. The adaptive threshold control system according to claim 1, wherein the first control signal and the second control signal cause the driver circuit of the transistor to adjust the drive current.

3. The adaptive threshold control system according to claim 1, wherein for the transistor to be turned on, the comparator circuit is further configured as follows: In response to the third control signal indicating that the time length is greater than the user-programmed value, the first threshold is increased, and In response to the third control signal indicating that the time length is less than the user-programmed value, the first threshold is reduced.

4. The adaptive threshold control system of claim 1, wherein, for the transistor to be turned on, the comparator circuit is configured to generate the first trigger signal in response to the first voltage increasing above the first threshold.

5. The adaptive threshold control system of claim 4, wherein the transistor is a low-side transistor in a half-bridge circuit, and wherein the comparator circuit is configured to generate the second trigger signal in response to the second voltage decreasing below the second threshold.

6. The adaptive threshold control system of claim 4, wherein the transistor is a high-side transistor in a half-bridge circuit, and wherein the comparator circuit is configured to generate the second trigger signal in response to the second voltage increasing above the second threshold.

7. The adaptive threshold control system of claim 1, wherein when the transistor is off, the comparator circuit is further configured to: In response to the third control signal indicating that the time length is greater than the user-programmed value, the first threshold is reduced; and In response to the third control signal indicating that the time length is less than the user-programmed value, the first threshold is increased.

8. The adaptive threshold control system of claim 1, wherein, for the transistor to be off, the comparator circuit is configured to generate the first trigger signal in response to the first voltage decreasing below the first threshold.

9. The adaptive threshold control system of claim 8, wherein the transistor is a low-side transistor in a half-bridge circuit, and wherein the comparator circuit is configured to generate the second trigger signal in response to the second voltage increasing above the second threshold.

10. The adaptive threshold control system of claim 8, wherein the transistor is a high-side transistor in a half-bridge circuit, and wherein the comparator circuit is configured to generate the second trigger signal in response to the second voltage decreasing below the second threshold.

11. An adaptive threshold control method, comprising: Determine a first voltage across the control terminal and the first current terminal of the transistor, and a second voltage across the second current terminal and the first current terminal of the transistor; It is determined that the first voltage crosses the first threshold; A first control signal is generated in response to determining that the first voltage crosses the first threshold. Determine that the second voltage crosses the second threshold; A second control signal is generated in response to determining that the second voltage crosses the second threshold. Determine the length of time between determining that the first voltage crosses the first threshold and determining that the second voltage crosses the second threshold; Compare the time length with the user-programmed value; and The first threshold is adjusted based on the comparison.

12. The adaptive threshold control method according to claim 11, wherein the first control signal and the second control signal cause the driver circuit of the transistor to adjust the drive current generated by the driver circuit.

13. The adaptive threshold control method of claim 11, wherein adjusting the first threshold based on the comparison for transistor conduction comprises: In response to the time length being greater than the user-programmed value, the first threshold is increased; as well as In response to the time length being less than the user-programmed value, the first threshold is reduced.

14. The adaptive threshold control method according to claim 11, wherein determining that the first voltage crosses the first threshold for the transistor to be turned on includes: It is determined that the first voltage increases to above the first threshold.

15. The adaptive threshold control method of claim 11, wherein adjusting the first threshold based on the comparison for transistor cutoff comprises: In response to the time length being greater than the user-programmed value, the first threshold is reduced; as well as In response to the time length being less than the user-programmed value, the first threshold is increased.

16. The adaptive threshold control method of claim 11, wherein determining that the first voltage crosses the first threshold for the transistor to be off includes: It is determined that the first voltage has decreased to below the first threshold.

17. An adaptive threshold control device, comprising: A half-bridge circuit includes a transistor, wherein the transistor includes a control terminal, a first current terminal, and a second current terminal; A driver circuit, coupled to the control terminal of the transistor and configured to generate a drive current; A buffer circuit coupled to the transistor, such that the buffer circuit receives a first voltage across the control terminal and the first current terminal of the transistor and a second voltage across the second current terminal and the first current terminal of the transistor; The comparator circuit, coupled to the buffer circuit, is configured as follows: The first voltage is compared with the first threshold. A first trigger signal is generated in response to the comparison between the first voltage and the first threshold. Compare the second voltage with the second threshold, and A second trigger signal is generated in response to the comparison between the second voltage and the second threshold. A timer circuit configured to determine the duration of time between the first trigger signal and the second trigger signal; as well as An adaptive threshold control circuit, coupled to the comparator circuit and the timer circuit, wherein the adaptive threshold control circuit is configured to: A first control signal is provided to the driver circuit in response to the first trigger signal, and a second control signal is provided to the driver circuit in response to the second trigger signal. A third control signal is provided to the comparator circuit to indicate whether the time length is greater than or less than a user-programmed value, wherein the third control signal causes the comparator circuit to adjust the first threshold.

18. The adaptive threshold control device of claim 17, wherein the driver circuit is configured to adjust the drive current in response to the first control signal and the second control signal.

19. The adaptive threshold control device of claim 17, wherein the comparator circuit is further configured to: The first trigger signal is generated in response to the first voltage crossing the first threshold. The second trigger signal is generated in response to the second voltage crossing the second threshold.

20. The adaptive threshold control device of claim 19, wherein for transistor turn-on, the comparator circuit is configured to generate the first trigger signal in response to the first voltage increasing above the first threshold, and wherein the comparator circuit is further configured to: In response to the third control signal indicating that the time length is greater than the user-programmed value, the first threshold is increased; and In response to the third control signal indicating that the time length is less than the user-programmed value, the first threshold is reduced.

21. The adaptive threshold control device of claim 19, wherein, for transistor cutoff, the comparator circuit is configured to generate the first trigger signal in response to the first voltage decreasing below the first threshold, and wherein the comparator circuit is further configured to: In response to the third control signal indicating that the time length is greater than the user-programmed value, the first threshold is reduced; and In response to the third control signal indicating that the time length is less than the user-programmed value, the first threshold is increased.

Images