Dead zone real-time detection and regulation system

Abstract

The application discloses a dead zone real-time detection and adjustment system, and introduces a series feedback loop connected with a dead zone generator of a pre-driver / inverter and a PWM module of an MCU, wherein the dead zone generator outputs a series feedback signal to the MCU, the series feedback signal is detected by the PWM module of the MCU and the original PWM signal is adjusted according to the detection result, and the adjusted PWM signal is sent to the pre-driver / inverter. The application introduces the series feedback loop, feeds back the dead zone signal from the dead zone generator embedded in the pre-driver / inverter chip to the MCU, adjusts the original PWM signal after detection and processing by the MCU, and then feeds the adjusted PWM signal to the pre-driver / inverter, so that the closed-loop control of software and hardware is achieved.

Description

Technical Field

[0001] This invention belongs to the field of motor control and power inverter technology, specifically relating to a dead zone real-time detection and adjustment system. Background Technology

[0002] Dead time is a forced delay time inserted into power electronic converters (such as inverters, H-bridges, and three-phase bridges). Its core function is to prevent two switching devices (such as IGBTs or MOSFETs) on the same bridge arm from simultaneously conducting, thus preventing shoot-through short circuits. This is a crucial mechanism for ensuring the safe operation of power electronic systems. If the dead time is too short, shoot-through may occur between the upper and lower transistors due to changes in the system environment, affecting system reliability. If the dead time is set too long, a brief period of uncontrolled circuit flow may occur during transistor switching. During this period, voltage and power are not applied to the load, resulting in power loss, reduced circuit efficiency, lower output waveform quality, and potential damage to the transistor, affecting circuit stability. Therefore, selecting an appropriate dead time based on the actual power MOSFETs and system links is crucial.

[0003] Traditional dead-time anti-coherence control technologies all use pure hardware to control the dead time, claiming to prevent crosstalk between the upper and lower transistors at the output. Examples include Chinese patents published on June 16, 2020, "A High-Reliability Adaptive Dead-Time Gate Drive Circuit"; January 11, 2022, "A Drive Signal Processing Device and Motor System"; December 29, 2023, "A Gate Drive Circuit"; July 3, 2018, "An Anti-Shot-Pass Protection Adaptive Dead-Time Circuit and Drive Circuit Including the Circuit"; and February 9, 2024, "A Motor Drive H-Bridge Dead-Time Adaptive Adjustment Method and Adjustment Circuit". However, because the relationship between the original PWM excitation at the bridge input and the actual PWM output excitation in practical applications is not obtained, the input excitation waveform cannot be optimized. That is, crosstalk between the upper and lower transistors cannot be avoided at the source. Once the hardware fails, crosstalk between the upper and lower transistors will reappear, and engineers will most likely only discover it after the MOS is damaged.

[0004] In practical applications, existing dead-time control technologies cannot completely reassure engineers, so a fixed dead time is usually set, and multiple methods are used to avoid crosstalk between the upper and lower transistors. Since the turn-on and turn-off times of power transistors vary with input voltage, temperature, and load current, and different batches of MOSFETs cannot achieve strong consistency, the fixed dead time setting is based on worst-case shoot-through and often allows for a sufficiently long margin. Summary of the Invention

[0005] To address the problems of traditional bridge applications using hardware dead-time anti-contact and fixed dead-time, this invention provides a real-time dead-time detection and adjustment system. By introducing a contact feedback loop, the dead-time generator embedded in the pre-drive / inverter chip feeds the dead-time signal back to the MCU. The MCU then detects and processes the signal, adjusts the original PWM signal, and sends it back to the pre-drive / inverter, thereby achieving closed-loop control of both software and hardware.

[0006] According to one aspect of the present invention, a real-time dead-zone detection and adjustment system is provided, which introduces a series feedback loop. The series feedback loop connects the dead-zone generator of the pre-drive / inverter and the PWM module of the MCU. The dead-zone generator outputs a series feedback signal to the MCU. The PWM module of the MCU detects the series feedback signal and adjusts the original PWM signal according to the detection result. The adjusted PWM signal is then sent to the pre-drive / inverter.

[0007] As a further technical solution, the dead-time generator includes a logic gate circuit and a pulse width multiplier circuit; the logic gate circuit is used to detect whether the upper and lower in-phase switching transistors are turned on simultaneously, and outputs different pulse signals to the pulse width multiplier circuit according to the detection result; the pulse width multiplier circuit multiplies the pulse signal and outputs it as a series feedback signal to the PWM module of the MCU.

[0008] As a further technical solution, when the logic gate circuit detects that the upper and lower switching transistors are turned on at the same time, it outputs a high pulse signal to the pulse width multiplier circuit.

[0009] As a further technical solution, the PWM module detects the pulse width of the high pulse signal in the series feedback signal, obtains the duration of the simultaneous on-state of the upper and lower switching transistors, and maps the duration to the delay of the original PWM pulse signal to obtain the adjusted PWM signal.

[0010] According to one aspect of the present invention, a method for real-time detection and adjustment of dead zones is provided, implemented using the aforementioned system, the method comprising: Obtain the series feedback signal output from the pre-drive / inverter; The serial feedback signal is detected to obtain the duration of the high pulse in the serial feedback signal; Determine whether the high pulse duration within a single cycle is less than the expected value A; If so, then further determine whether the cumulative time of high pulses within multiple cycles is less than the expected value B; If yes, then decrease the current dead time; otherwise, increase the current dead time. The adjusted dead time PWM signal is output to the pre-drive / inverter.

[0011] As a further technical solution, when the high pulse time within a single cycle is detected to be greater than or equal to the expected value A, the current dead time is increased.

[0012] As a further technical solution, the expected value A is determined by the switching speed of the switching transistor.

[0013] As a further technical solution, the expected value B is set by multiplying the preset proportional margin of the expected value A by the number of cycles.

[0014] As a further technical solution, the method also includes: continuously recording the serial feedback signal by the MCU, and reducing the delay time of the original PWM signal when there is no serial feedback signal or no drastic dead-zone pulse within a set time period.

[0015] As a further technical solution, the method also includes: when a dead-time pulse with a sharp jump occurs, increasing the delay time of the original PWM signal according to the maximum dead-time pulse.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: Compared with traditional bridge applications that use hardware dead-time anti-counterfeiting and fixed dead-time, the dead-time detection and control system described in this invention, through a combination of hardware and software, can flexibly control the dead time in real time to achieve the shortest and most reliable dead time. This ensures system safety and stability while also guaranteeing high efficiency, waveform distortion-free waveforms, and low EMI radiation. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a topology diagram of the real-time dead zone detection and adjustment system provided in an embodiment of the present invention.

[0019] Figure 2 A schematic diagram of the circuit principle of the dead zone real-time detection and adjustment system provided in an embodiment of the present invention.

[0020] Figure 3 This is a schematic diagram of PWM signal adjustment provided in an embodiment of the present invention.

[0021] Figure 4 This is a flowchart illustrating the real-time dead zone detection and adjustment method provided in an embodiment of the present invention. Detailed Implementation

[0022] Traditional dead-time control techniques typically employ pure hardware anti-contact measures combined with a fixed dead time. In applications where reducing system power loss and improving output waveform quality is desired, traditional dead-time anti-contact techniques should be combined to minimize the dead time. However, because the relationship between the original PWM input and actual PWM output excitation of the bridge in practical applications is not readily available, it's impossible to continuously monitor the output waveform under varying environmental conditions such as temperature, load, and voltage. If the hardware anti-contact measures fail, the possibility of crosstalk between the upper and lower transistors still exists, which engineers will likely only discover after the MOSFET fails. Therefore, engineers generally set a large and fixed dead time, sacrificing bridge control efficiency and output waveform distortion to ensure bridge stability.

[0023] For example, in motor applications, when the back-end bridge is a power MOSFET, the dead time is generally set to 2µs. If the back-end bridge is an IGBT, the dead time is generally set to 5µs. For low-speed bridge applications at 20kHz, the dead time will cause 4% to 10% of the power wastage to be lost per unit cycle. The output waveform distortion will also cause sampling distortion, and will seriously aggravate EMI radiation and degrade the motor control effect, not to mention higher-speed motor applications.

[0024] In addition, in inverter applications such as BUCK, the control frequency of the upper and lower MOSFETs is generally 500kHz, and the dead time is generally set to about 100ns, which accounts for 5% of the unit time. If the inverter output voltage is 1V, then the power loss of the 0.8V differential diode per unit time can reach 0.8*0.05 / 1=4%, which is a lot of room for improvement for inverters known for their high efficiency.

[0025] Therefore, minimizing dead time while ensuring system security is the direction that needs to be addressed.

[0026] Therefore, compared to the common bridge control loop, this invention introduces a series feedback loop, which connects the dead-time generator of the pre-drive / inverter and the PWM module of the MCU. The dead-time generator converts the PWM excitation signal related to the pre-drive output into a pulse signal that is connected in series with the upper and lower transistors and sends it to the MCU. After the MCU completes its detection, it can adjust the original PWM excitation signal, thus avoiding the series connection between the upper and lower transistors from the source and achieving the best application effect in terms of efficiency.

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. In addition, the technical features of the various embodiments or individual embodiments provided by the present invention can be arbitrarily combined to form new technical solutions. Such combinations are not bound by the order of steps and / or structural composition patterns, but must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0028] like Figure 1 As shown, this embodiment of the invention provides a real-time dead-zone detection and adjustment system, which introduces a series feedback loop. The series feedback loop connects the dead-zone generator of the pre-drive / inverter and the PWM module of the MCU. The dead-zone generator outputs a series feedback signal to the MCU. The PWM module of the MCU detects the series feedback signal and adjusts the original PWM signal according to the detection result. The adjusted PWM signal is then sent to the pre-drive / inverter.

[0029] The key to this invention lies in the serial feedback, where the dead-time generator embedded in the pre-drive / inverter chip feeds the dead-time signal back to the MCU, and the MCU detects and processes the signal to adjust the original PWM signal before sending it to the pre-drive / inverter, thereby achieving closed-loop control of both software and hardware.

[0030] like Figure 2 As shown, the dead-time generator mainly consists of logic gate circuits and pulse width multiplier circuits. The logic gate circuits primarily detect whether the upper and lower MOSFETs of the non-inverting circuit are simultaneously turned on, i.e., both upper and lower drives output high simultaneously. Since the gate-source turn-on voltage of the power MOSFETs is 2V~5V, the high-level threshold is set to 1.5V to ensure absolute safety. When both upper and lower pre-drive outputs are greater than 1.5V, the logic gate circuit outputs 1; otherwise, it outputs 0. Under normal circumstances, the output of the logic gate circuit should remain low. When crosstalk occurs between the upper and lower drives, the logic gate circuit outputs a high pulse, the pulse width of which is the duration of the crosstalk. The pulse width multiplier circuit mainly multiplies the extremely narrow logic gate output by 20 times, such as from 20ns to 400ns, for detection by the downstream MCU.

[0031] The MCU uses the PWM module to detect the pulse width of the feedback signal generated by the dead-time generator, obtains the duration of the upper and lower edge continuation, and then maps the duration to the delay of the original PWM pulse signal, such as... Figure 3 As shown, t1 / t2 is approximately 20 times.

[0032] The aforementioned t1 / t2 ratio is approximately 20 times because the series feedback signal is amplified by 20 times during pre-drive output. In normal applications, the system's operating voltage and ambient temperature will cause slight variations in the duration of the series connection between the upper and lower sides. Therefore, the time t2 will be continuously fine-tuned in a closed loop based on subsequent series feedback until the series feedback pulse is lower than the expected value. This expected value can be flexibly set in the application code after engineers have fully evaluated efficiency and reliability.

[0033] Furthermore, since the MCU can continuously record the serial feedback pulse, when there is no serial feedback pulse for a long time or no dead pulse with a sharp jump, it means that the current environment is stable and the time t2 can be appropriately reduced to achieve higher working efficiency; however, when a dead pulse with a sharp jump occurs, it means that the current environment is unstable and the time t2 can be increased according to the maximum dead pulse to achieve a safer op-amp effect.

[0034] Based on the real-time dead zone detection and adjustment system described in any of the foregoing embodiments, this invention also provides a real-time dead zone detection and adjustment method, such as... Figure 4 As shown, its workflow includes: Step 1: The MCU outputs PWM excitation with an initial dead time of T. In practice, the initial dead time T is usually set large to avoid series connection between the upper and lower transistors during initial operation.

[0035] Step 2: The pre-drive / inverter outputs a series feedback signal to the MCU through the embedded dead-time generator.

[0036] Step 3: The MCU detects and stores the serial feedback signal through its PWM module to obtain the duration of the high pulse in the serial feedback signal.

[0037] Step 4: The MCU determines whether the high pulse time within a single cycle is less than the expected value A.

[0038] If the high pulse time within a single cycle is less than the expected value A, proceed to step 5.

[0039] If the high pulse time within a single cycle is greater than or equal to the expected value A, then increase the current dead time and return to step 1.

[0040] Step 5: Determine whether the cumulative time of high pulses within multiple cycles is less than the expected value B.

[0041] If the cumulative time of high pulses over multiple cycles is less than the expected value B, then reduce the current dead time and return to step 1.

[0042] If the cumulative time of high pulses over multiple cycles is greater than or equal to the expected value B, then increase the current dead time and return to step 1.

[0043] Step 6: Output the adjusted dead time PWM signal to the pre-drive / inverter.

[0044] In the method described in this embodiment of the invention, the MCU continuously detects and records the high pulse of the pre-drive feedback. Under normal circumstances, it should not be detected, indicating that no high-voltage or low-voltage interconnection has occurred. When the high pulse duration is detected to be higher than the expected value A in a single cycle, the current dead time is immediately increased; when the cumulative high pulse duration is detected to be higher than the expected value B in multiple cycles, the current dead time can be increased appropriately; when the cumulative high pulse duration is detected to be lower than the expected value B in multiple cycles, the current dead time can be decreased appropriately.

[0045] The expected value A is generally determined by the turn-on and turn-off speed of the MOSFET. If it is set to 400ns, it means that the pre-drive may have a series connection time of about 20ns. However, since the MOSFET gate threshold is 1.5V, which is relatively safe, the actual series connection time of the upper and lower MOSFETs will be even lower, possibly only 10ns. During this time, it can be ensured that the MOSFET will not be damaged by series connection. The expected value B can be set according to 50% margin of the expected value A × number of cycles. It should be noted that the current expected values ​​A and B are only examples. In actual applications, they need to be adjusted according to the working environment, MOSFET selection, and actual operation and debugging effects.

[0046] In summary, the key points of the present invention are as follows: 1. The pre-drive / inverter has an embedded dead-time generator, which can generate a high pulse when the upper and lower MOSFETs are turned on at the same time. After pulse width multiplication, the continuous series signal between the upper and lower sides is transmitted to the MCU in real time.

[0047] 2. The MCU detects the series feedback pulse through PWM and records the pulse width of single and multiple cycles. It flexibly adjusts the output delay of PWM and the safe pulse width range of series feedback pulse in real time, forming a closed loop with point 1. This achieves maximum efficiency, ensures waveform distortion-free waveform, better control effect, and reduced EMI radiation while ensuring the safe and stable application of the bridge.

[0048] Any points not elaborated above are common knowledge in this field.

[0049] The terms “comprising” and “having”, and any variations thereof, in the specification, claims, and accompanying drawings of this invention are intended to cover a non-exclusive inclusion, such as a process, method, system, product, or apparatus that includes a series of steps or units, not necessarily limited to those explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the technical solutions of the embodiments of the present invention.

Claims

1. A real-time dead zone detection and adjustment system, characterized in that, A series feedback loop is introduced, which connects the dead-time generator of the pre-drive / inverter and the PWM module of the MCU. The dead-time generator outputs a series feedback signal to the MCU, and the PWM module of the MCU detects the series feedback signal and adjusts the original PWM signal according to the detection result. The adjusted PWM signal is then sent to the pre-drive / inverter.

2. The dead zone real-time detection and adjustment system according to claim 1, characterized in that, The dead-time generator includes a logic gate circuit and a pulse width multiplier circuit. The logic gate circuit is used to detect whether the upper and lower in-phase switches are turned on simultaneously, and outputs different pulse signals to the pulse width multiplier circuit according to the detection result. The pulse width multiplier circuit multiplies the pulse signal and outputs it as a series feedback signal to the PWM module of the MCU.

3. The dead zone real-time detection and adjustment system according to claim 2, characterized in that, When the logic gate circuit detects that the upper and lower switching transistors are turned on simultaneously, it outputs a high pulse signal to the pulse width multiplier circuit.

4. The dead zone real-time detection and adjustment system according to claim 3, characterized in that, The PWM module detects the pulse width of the high pulse signal in the series feedback signal, obtains the duration of the simultaneous on-state of the upper and lower switching transistors, and maps the duration to the delay of the original PWM pulse signal to obtain the adjusted PWM signal.

5. A method for real-time detection and adjustment of dead zones, implemented using the system described in any one of claims 1-4, characterized in that, The method includes: Obtain the series feedback signal output from the pre-drive / inverter; The serial feedback signal is detected to obtain the duration of the high pulse in the serial feedback signal; Determine whether the high pulse duration within a single cycle is less than the expected value A; If so, then further determine whether the cumulative time of high pulses within multiple cycles is less than the expected value B; If yes, then decrease the current dead time; otherwise, increase the current dead time. The adjusted dead time PWM signal is output to the pre-drive / inverter.

6. The method for real-time detection and adjustment of dead zone according to claim 5, characterized in that, When a high pulse duration within a single cycle is detected to be greater than or equal to the expected value A, the current dead time is increased.

7. The method for real-time detection and adjustment of dead zone according to claim 5, characterized in that, The expected value A is determined by the switching speed of the switching transistor.

8. The method for real-time detection and adjustment of dead zone according to claim 7, characterized in that, The expected value B is set by multiplying the preset proportional margin of the expected value A by the number of cycles.

9. The method for real-time detection and adjustment of dead zone according to claim 5, characterized in that, The method further includes: continuously recording the serial feedback signal by the MCU, and reducing the delay time of the original PWM signal when there is no serial feedback signal or no drastic dead-zone pulse within a set time period.

10. The method for real-time detection and adjustment of dead zone according to claim 9, characterized in that, The method further includes: when a dead-time pulse with a sharp jump occurs, increasing the delay time of the original PWM signal according to the maximum dead-time pulse.

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