Current limit protection system and method for a motor pre-driver

Abstract

A current limit protection system and method for a motor pre-driver are disclosed. A current limit circuit detects a current of a resistor connected to a motor, and then compares the current of the resistor with a current threshold to output a current comparison signal. When a control circuit determines that the current of the resistor is greater than the current threshold according to the current comparison signal, and a duty cycle of a first signal of a first node or a second signal of a second node of the motor reaches a default value, the first upper bridge switch and the second upper bridge switch are turned off, and the first lower bridge switch and the second lower bridge switch are turned on alternately, so that the temperature of the motor is gradually reduced.

Description

TECHNICAL FIELD

[0001] The present invention relates to a current limiting protection system and method, and in particular, to a current limiting protection system and method for a motor pre-driver of a bridge drive circuit for protecting a single phase motor. BACKGROUND

[0002] In many electronic products, circuit components generate heat during operation. In particular, in a sealed enclosure of a server, the heat generated by each circuit component during operation circulates within the sealed enclosure and heats other circuit components, causing the circuit components to overheat and burn out. Therefore, in electronic products, a fan must be provided to cool the circuit components within the electronic products.

[0003] However, during operation of the fan, the heat air circulating within the sealed enclosure heats the transistors of the motor drive circuit. In addition, during switching of the transistors by the control circuit, the transistors receiving the shared voltage can burn out due to excessive current. Therefore, the current flowing through the transistors must be limited at appropriate times. SUMMARY

[0004] The present application provides a current limit protection system for a motor pre-driver, which is suitable for a bridge drive circuit of a single-phase motor. The bridge drive circuit comprises a plurality of switching components. The plurality of switching components comprises a first upper bridge switch, a first lower bridge switch, a second upper bridge switch and a second lower bridge switch. A first end of the first upper bridge switch and a first end of the second upper bridge switch are coupled to a shared voltage. A first node between a second end of the first upper bridge switch and a first end of the first lower bridge switch is connected to a first end of the single-phase motor. A second node between a second end of the second upper bridge switch and a first end of the second lower bridge switch is connected to a second end of the single-phase motor. A second end of the second upper bridge switch and a second end of the second lower bridge switch are connected to a first end of a sensing resistor. A second end of the sensing resistor is grounded. The current limit protection system for the motor pre-driver comprises a current limit circuit and a control circuit. The current limit circuit is connected to the first end of the sensing resistor. The current limit circuit is configured to detect a current of the sensing resistor, and then compare the current of the sensing resistor with a current threshold to output a current comparison signal. The control circuit is connected to control terminals of the plurality of switching components and the current limit circuit. The control circuit is configured to output a plurality of control signals to the plurality of switching components according to the current comparison signal, so as to turn on or turn off the plurality of switching components. When the control circuit determines that the current of the sensing resistor is greater than the current threshold according to the current comparison signal, and a current time reaches a maximum duty cycle interval of a first signal or a second signal, the control circuit executes a rest protection procedure to maintain turning off the first upper bridge switch and the second upper bridge switch, and turn on the first lower bridge switch and the second lower bridge switch alternately for a fixed time.

[0005] In an embodiment, in the maximum duty cycle interval of the first signal in which the current of the sensing resistor is greater than the current threshold, the current flows from the first upper bridge switch to the single-phase motor, and then flows to the sensing resistor through the second lower bridge switch. In the maximum duty cycle interval of the second signal in which the current of the sensing resistor is greater than the current threshold, the current flows from the second upper bridge switch to the single-phase motor, and then flows to the sensing resistor through the first lower bridge switch.

[0006] In an embodiment, in the maximum duty cycle interval, the control circuit counts the number of times that the current limit circuit compares the current of the sensing resistor to be greater than the current threshold according to the level of the current comparison signal, and executes the rest protection procedure when the number of times reaches a number threshold.

[0007] In an embodiment, each of the first signal and the second signal has a plurality of maximum duty cycle intervals. The control circuit counts the number of consecutive maximum duty cycle intervals in which the current of the sensing resistor is greater than the current threshold according to the level of the current comparison signal, and executes the rest protection procedure when the number of consecutive maximum duty cycle intervals is greater than a number threshold.

[0008] In one embodiment, each of the first signal and the second signal has a plurality of maximum duty cycle intervals, the control circuit determines, according to the current comparison signal, whether the number of times that the current of the sensing resistor is greater than the current threshold in each maximum duty cycle interval reaches a number threshold, and when the number of consecutive maximum duty cycle intervals that the current of the sensing resistor is greater than the current threshold reaches a quantity threshold, executes a rest protection procedure.

[0009] In addition, the present application provides a current limiting protection method for a motor pre-driver, which is suitable for a bridge driving circuit of a single-phase motor. The bridge driving circuit comprises a plurality of switching components. The plurality of switching components comprises a first upper bridge switch, a first lower bridge switch, a second upper bridge switch, and a second lower bridge switch. A first end of the first upper bridge switch and a first end of the second upper bridge switch are coupled to a shared voltage. A first node between a second end of the first upper bridge switch and a first end of the first lower bridge switch is connected to a first end of the single-phase motor. A second node between a second end of the second upper bridge switch and a first end of the second lower bridge switch is connected to a second end of the single-phase motor. The second end of the second upper bridge switch and the second end of the second lower bridge switch are connected to a first end of a sensing resistor. A second end of the sensing resistor is grounded. The current limiting protection method for the motor pre-driver comprises the following steps: detecting a current of the sensing resistor; determining whether the current of the sensing resistor is greater than a current threshold, if not, returning to the previous step, if yes, executing the following step; determining whether a current time reaches a maximum duty cycle interval of a first signal of the first node or a second signal of the second node and a duty cycle of the first signal or the second signal is equal to a default cycle, if not, switching the plurality of switching components, adjusting the duty cycle of the first signal or the second signal to limit the current flowing through each switching component, and controlling the single-phase motor to operate stably, and then returning to the previous step, if yes, executing the following step; turning off the first upper bridge switch and the second upper bridge switch for a fixed time, and turning on the first lower bridge switch and the second lower bridge switch alternately; and automatically turning on the first upper bridge switch or the second upper bridge switch again at the end of the fixed time, and controlling the single-phase motor to operate stably.

[0010] In one embodiment, the current limiting protection method for the motor pre-driver further comprises the following steps: in the maximum duty cycle interval of the first signal, allowing the current to flow from the first upper bridge switch to the single-phase motor, and then to the sensing resistor through the second lower bridge switch, and in the maximum duty cycle interval of the second signal, allowing the current to flow from the second upper bridge switch to the single-phase motor, and then to the sensing resistor through the first lower bridge switch.

[0011] In one embodiment, the current limiting protection method for the motor pre-driver further comprises the following steps: counting a number of times that the current of the sensing resistor is greater than the current threshold in the maximum duty cycle interval; and determining whether the number of times reaches a number threshold, if not, returning to the previous step, if yes, executing a rest protection procedure.

[0012] In one embodiment, the current limit protection method of the motor pre-driver further comprises the steps of: detecting the current of the sense resistor multiple times; comparing the current of the sense resistor with the current threshold multiple times to output multiple waveforms of the current comparison signal; counting how many maximum duty cycle intervals in the first signal or the second signal the current of the sense resistor is greater than the current threshold to obtain a number; and determining whether the number is greater than a number threshold, if not, returning to the previous step, and if yes, executing the rest protection procedure.

[0013] As described above, the present application provides a current limit protection system and method of a motor pre-driver, which has the following main features:

[0014] detecting a sense resistor connected to the motor to detect the current of the motor;

[0015] comparing the current of the sense resistor with a current threshold through the motor pre-driver circuit to determine whether a current limit occurs in the maximum duty cycle interval of the signal of the motor;

[0016] if the current limit occurs at a time outside the maximum duty cycle interval, only executing the current limit procedure, and if the current limit occurs in the maximum duty cycle interval, forcibly executing the rest protection procedure to prevent the operating temperature of the multiple switch components, such as transistors, of the bridge drive circuit from being too high.

[0017] For further understanding of the features and technical contents of the present application, please refer to the following detailed description and drawings of the present application. However, the drawings provided are only used for reference and illustration, and not used to limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 a block diagram of the current limit protection system of the motor pre-driver of an embodiment of the present application.

[0019] Figure 2 a flowchart of the steps of the current limit protection method of the motor pre-driver of an embodiment of the present application.

[0020] Figure 3 signal waveform diagrams of the Hall signal, the commutation signal, the first signal, and the second signal of a single-phase motor detected by the current limit protection system and method of the motor pre-driver of an embodiment of the present application.

[0021] Figure 4 signal waveform diagrams of the Hall signal, the commutation signal, the first signal, the second signal, and the current limit signal of a single-phase motor detected by the current limit protection system and method of the motor pre-driver of an embodiment of the present application.

[0022] Figure 5The switching diagram of the bridge drive circuit of the single-phase motor operated in the steady-state mode by the current limit protection system and method of the motor pre-driver embodiment of the present application.

[0023] Figure 6 The switching diagram of the bridge drive circuit of the single-phase motor when performing the rest protection procedure by the current limit protection system and method of the motor pre-driver embodiment of the present application.

[0024] Figure 7 The first diagram of comparing the current with the current threshold value in each of the plurality of maximum duty cycle intervals of the first signal and the second signal by the current limit protection system and method of the motor pre-driver embodiment of the present application.

[0025] Figure 8 The second diagram of comparing the current with the current threshold value in each of the plurality of maximum duty cycle intervals of the first signal and the second signal by the current limit protection system and method of the motor pre-driver embodiment of the present application. DETAILED DESCRIPTION

[0026] The following embodiments of the present application are disclosed by way of illustration and not limitation. The advantages and effects of the present application can be understood by the contents disclosed in the specification. The present application can be implemented or applied by other different embodiments, and the details in the specification can be modified and changed in various ways based on different views and applications without departing from the spirit of the present application. In addition, the drawings of the present application are simple schematic illustrations and not actual size depictions, which is declared in advance. The following embodiments will further illustrate the related technical contents of the present application in detail, but the disclosed contents are not used to limit the protection scope of the present application. In addition, the term "or" used herein can include any one or more combinations of the associated listed items as possible.

[0027] Referring to Figure 1 , which is a block diagram of the current limit protection system of the motor pre-driver embodiment of the present application.

[0028] As shown in Figure 1 , the current limit protection system of the present embodiment can include a current limit circuit 10 and a control circuit 20, which can be disposed in a motor pre-driver 100. The control circuit 20 is connected to the current limit circuit 10 and a bridge drive circuit HBDV. The current limit circuit 10 is connected to a sensing resistor RS. A single-phase motor MT is connected to the bridge drive circuit HBDV and the sensing resistor RS.

[0029] The bridge drive circuit HBDV may include multiple switching components. These switching components may include a first upper bridge switch H1, a first lower bridge switch L1, a second upper bridge switch H2, and a second lower bridge switch L2. The control terminal of each is connected to the control circuit 20, so that the control circuit 20 outputs multiple control signals M1P, M1N, M2P, and M2N to control the operation of the first upper bridge switch H1, the first lower bridge switch L1, the second upper bridge switch H2, and the second lower bridge switch L2, respectively.

[0030] For example, such as Figure 1 As shown, the first upper bridge switch H1 and the second upper bridge switch H2 are PMOS (P-type metal-oxide-semiconductor) transistors, while the first lower bridge switch L1 and the second lower bridge switch L2 are NMOS transistors. This is only an example and is not intended to limit the invention.

[0031] The first terminal of the first upper bridge switch H1 and the first terminal of the second upper bridge switch H2 are coupled to a shared voltage VCC. The second terminal of the first upper bridge switch H1 is connected to the first terminal of the first lower bridge switch L1. The first node OUT1 between the second terminal of the first upper bridge switch H1 and the first terminal of the first lower bridge switch L1 is connected to the first terminal of the single-phase motor MT, i.e., the first terminal of the inductor L of the single-phase motor MT. The second terminal of the inductor L is connected to the first terminal of the resistor R of the single-phase motor MT.

[0032] The second terminal of the second upper bridge switch H2 is connected to the first terminal of the second lower bridge switch L2. The second node OUT2 between the second terminal of the second upper bridge switch H2 and the first terminal of the second lower bridge switch L2 is connected to the second terminal of the single-phase motor MT, i.e., the second terminal of the resistor R of the single-phase motor MT. The second terminals of the first lower bridge switch L1 and the second lower bridge switch L2 are connected to the first terminal of the sensing resistor RS. The second terminal of the sensing resistor RS is grounded.

[0033] Please refer to the following: Figures 1 to 6 ,in Figure 2 This is a flowchart illustrating the steps of a current limiting protection method for a motor pre-driver according to an embodiment of the present invention.

[0034] like Figure 2 As shown, the current limiting protection method for the motor pre-drive in this embodiment of the invention may include steps S101 to S115, which may be performed by, for example... Figure 1 The current limiting circuit 10 and control circuit 20 shown operate on the single-phase motor MT, as detailed below.

[0035] In step S101, the control circuit 20 controls the bridge drive circuit HBDV to drive the single-phase motor MT to operate stably in steady-state mode.

[0036] like Figure 3 and Figure 4The commutation signal PHS shown indicates that the single-phase motor MT commutates based on the transition states of the Hall signals H+ and H- sensed by the Hall sensor. In this paper, the upper and lower edges of the commutation signal PHS are both taken as the commutation time points. Figure 4 During the time before the rest protection time TCLF of the commutation signal PHS shown, the bridge drive circuit HBDV is controlled by the control circuit 20 to drive the single-phase motor MT to operate in steady state mode.

[0037] For example, such as Figure 4 and Figure 5 As shown, during the non-working cycle time t02, t04, t06, and t08 of the commutation signal PHS, i.e. when the commutation signal PHS is at the first reference level, for example, a low level (actually, it can be a high level), the control circuit 20 closes the first upper bridge switch H1 and the second lower bridge switch L2, and opens the second upper bridge switch H2 and the first lower bridge switch L1 to realize the first commutation operation, so that the current I1 flows from the second upper bridge switch H2 through the single-phase motor MT to the first lower bridge switch L1, and then flows to the sensing resistor RS.

[0038] Next, when the current time reaches a commutation point of the commutation signal PHS, for example, when the commutation signal PHS changes from low level to high level at the positive edge (actually, it can be the negative edge), a second commutation operation is performed. Specifically, during the working cycle time t01, t03, t05 of the commutation signal PHS and the time interval between time points t07A and t07B, i.e., when the commutation signal PHS is at the second reference level, for example, high level (actually, it can be low level), the control circuit 20 closes the second upper bridge switch H2 and the first lower bridge switch L1, and opens the first upper bridge switch H1 and the second lower bridge switch L2 to realize the second commutation operation. As a result, the current I2 flows from the first upper bridge switch H1 through the single-phase motor MT to the second lower bridge switch L2, and then to the sensing resistor RS.

[0039] In other words, in steady-state mode, the control circuit 20 can repeatedly switch the bridge drive circuit HBDV to repeatedly perform the first commutation operation and the second commutation operation, thereby controlling the single-phase motor MT to operate stably in steady-state mode.

[0040] In step S103, the current IS of the sensing resistor RS of the single-phase motor MT is detected by the current limiting circuit 10.

[0041] In step S105, the current limiting circuit 10 compares the current IS of the sensing resistor RS with the current threshold to output a current comparison signal, and the control circuit 20 determines whether the current IS of the sensing resistor RS is greater than the current threshold according to the level of the current comparison signal. If the current IS of the sensing resistor RS is not greater than the current threshold, for example, the current comparison signal is low, step S103 is performed again. Conversely, if the current IS of the sensing resistor RS is greater than the current threshold, for example, the current comparison signal is high, step S107 is performed next.

[0042] In step S107, the control circuit 20 determines whether the current time reaches the maximum duty interval MDUTY of the first signal OT1S of the first node OUT1 or the second signal OT2S of the second node OUT2. In the maximum duty interval MDUTY, the duty cycle of the first signal OT1S or the second signal OT2S is equal to the default period, for example, 50%. If not, step S103 is performed again. If yes, the rest protection procedure of steps S109 to S115 is performed in sequence next.

[0043] In detail, as shown in Figure 3 , each of the first signal OT1S and the second signal OT2S can have the maximum duty interval MDUTY, the first soft switching interval TS1, the first off time interval TF1, the second soft switching interval TS2, and the second off time interval TF2.

[0044] The duty cycle of the first signal OT1S and the second signal OT2S is zero in the first off time interval TF1, then reaches the first soft switching interval TS1, slowly increases by the soft switching of the bridge drive circuit HBDV by the control circuit 20, until it increases to the default period, for example, 50% when entering the maximum duty interval MDUTY. After the maximum duty interval MDUTY ends, it reaches the second soft switching interval TS2, slowly decreases the duty cycle of the first signal OT1S and the second signal OT2S by the soft switching of the bridge drive circuit HBDV by the control circuit 20, until it decreases in the second off time interval TF2.

[0045] As shown in Figure 4 , the high level of the current limiting signal CL1 represents that the current IS of the sensing resistor RS is greater than the current threshold, and the current limiting procedure is performed. In the current limiting procedure, one or more of the first upper bridge switch H1, the first lower bridge switch L1, the second upper bridge switch H2, and the second lower bridge switch L2 can be switched by the control circuit 20 to limit the current flowing through each switch component when the single-phase motor MT operates in the steady state mode.

[0046] In the steady time TCL, the current IS of the sensing resistor RS greater than the current threshold value all occurs in the time outside the maximum duty interval MDUTY, such as the first soft switching interval TS1, the first off time interval TF1, the second soft switching interval TS2 or the second off time interval TF2. In this case, the current limiting procedure performed is considered as a normal procedure.

[0047] However, it is worth noting that in any maximum duty interval MDUTY of the first signal OT1S and the second signal OT2S, the current limiting procedure is not allowed to be performed. As shown in the portion enclosed by the dashed circle, in the maximum duty interval MDUTY of the fourth waveform of the first signal OT1S, the current limiting procedure performed is considered as an abnormal procedure. Figure 4

[0048] Therefore, when the current IS of the sensing resistor RS greater than the current threshold value in the maximum duty interval MDUTY is judged by the current limiting circuit 10, the rest protection procedure of steps S109 to S115 is sequentially performed from the time point t07B by the control circuit 20. Figure 5 The current comparison signal CL1 is outputted as high level at the time point t07B as shown. The control circuit 20 starts to sequentially perform the rest protection procedure of steps S109 to S115 from the time point t07B according to the current comparison signal CL1 as high level.

[0049] In step S109, the first upper bridge switch H1 and the second upper bridge switch H2 are turned off by the control circuit 20 in the time interval from the time point t07B to the time point TRP1 in the rest protection time TCL when the phase change signal PHS is high level (actually can be replaced by low level). As a result, the single-phase motor MT runs by inertia.

[0050] In step S111, it is judged by the control circuit 20 whether the next phase change time point TRP1 of the phase change signal PHS is reached to decide whether to start to alternately switch the first lower bridge switch L1 and the second lower bridge switch L2. If not, it returns to perform step S109. If yes, it proceeds to perform step S113.

[0051] In step S113, the first upper bridge switch H1 and the second upper bridge switch H2 are maintained to be turned off by the control circuit 20, and the first lower bridge switch L1 and the second lower bridge switch L2 are alternately switched according to the level of the phase change signal PHS to gradually reduce the rotation speed of the single-phase motor MT until the fan is stopped, and then it proceeds to perform step S115.

[0052] In detail, the first lower bridge switch L1 and the second lower bridge switch L2 are alternately switched by the control circuit 20 as shown in the following table. Figure 6 ​As shown, during the time t12 between the start of the next commutation time point TRP1 and the next commutation time point TRP2 of the commutation signal PHS, that is, when the commutation signal PHS is at a low level (which can actually be replaced by a high level), the first lower bridge switch L1 is turned on and the second lower bridge switch L2 is turned off, while the first upper bridge switch H1 and the second upper bridge switch H2 remain closed.

[0053] Using control circuit 20, etc. Figure 6 As shown, during the time t23 between the next commutation time point TRP2 of the commutation signal PHS and the next commutation time point TRP3, that is, when the commutation signal PHS is at a high level (which can actually be replaced by a low level), the first lower bridge switch L1 is closed and the second lower bridge switch L2 is opened, while the first upper bridge switch H1 and the second upper bridge switch H2 remain closed.

[0054] Next, when the current time reaches the next commutation time point TRP3 of the commutation signal PHS, that is, the positive edge of the commutation signal PHS (which may actually be replaced by the negative edge of the commutation signal PHS), the control circuit 20 closes the second lower bridge switch L2 and opens the first lower bridge switch L1, while the first upper bridge switch H1 and the second upper bridge switch H2 remain closed for a period of time t34.

[0055] In other words, such as Figure 6 As shown, during the rest protection time TCLF, the first upper bridge switch H1 and the second upper bridge switch H2 remain closed, while the first lower bridge switch L1 and the second lower bridge switch L2 are alternately opened to implement the rest protection procedure. In this embodiment, for example, when the commutation signal PHS is at a low level, i.e., during the non-working cycle time of the commutation signal PHS, such as t12 or t34, the first lower bridge switch L1 is opened and the second lower bridge switch L2 is closed. Conversely, when the commutation signal PHS is at a high level, i.e., during the working cycle time of the commutation signal PHS, such as t13, the second lower bridge switch L2 is opened and the first lower bridge switch L1 is closed.

[0056] However, if the current limiting procedure is executed within the maximum duty cycle interval MDUTY, the commutation time point that arrives first is the positive edge of the commutation signal PHS, instead of... Figure 6 The time point shown represents the negative edge, which means the first lower bridge switch L1 is closed and the second lower bridge switch L2 is opened. Then, when the current time reaches the next commutation time point (positive edge time point) of the commutation signal PHS, the second lower bridge switch L2 is closed and the first lower bridge switch L1 is opened.

[0057] It should be understood that the present application is not limited to the level of the phase signal PHS. In fact, the switching operation described herein that triggers the execution of the bridge drive circuit HBDV when the phase signal PHS reaches the high level or the low level can be appropriately set according to the actual application requirements.

[0058] In step S115, the fan is maintained at a standstill for a fixed time, and then returns to step S101 to switch the bridge drive circuit HBDV by the control circuit 20 to restart the single-phase motor MT to operate in the steady-state mode described above.

[0059] Referring to Figure 7 , which is a first schematic diagram showing the comparison of the current and the current threshold value by the current limiting protection system and method of the motor pre-driver according to the embodiment of the present application in each of the maximum duty cycle intervals of the first signal and the second signal.

[0060] For the convenience of description, in Figure 7 , the maximum duty cycle interval MDUTY of the first signal OT1S and the second signal OT2S as shown in Figure 3 is aligned and overlapped with the phase signal PHS as shown in Figure 6 , in which the maximum duty cycle interval MDUTY of the second signal OT2S is aligned with the low level of the phase signal PHS, and the maximum duty cycle interval MDUTY of the first signal OT1S is aligned with the high level of the phase signal PHS.

[0061] As described above, the rest protection procedure is executed whenever the control circuit 20 determines that the current IS of the sensing resistor RS is greater than the current threshold value in the maximum duty cycle interval MDUTY of the first signal OT1S or the second signal OT2S. That is, the detected current IS of the sensing resistor RS is compared with the current threshold value only once in each of the maximum duty cycle intervals MDUTY of the first signal OT1S and the second signal OT2S.

[0062] However, as shown in Figure 7 , the current limiting circuit 10 continuously detects the current of the current limiting circuit 10 to detect a plurality of currents at different time points in the maximum duty cycle interval MDUTY, respectively, and compare each current with the current threshold value to output the current comparison signal. That is, the detected current IS of the sensing resistor RS is compared with the current threshold value multiple times in each of the maximum duty cycle intervals MDUTY of the first signal OT1S and the second signal OT2S.

[0063] Then, the control circuit 20 counts the number of times that the current IS of the sensing resistor RS is greater than the current threshold value in each of the maximum duty cycle intervals MDUTY according to the level of the current comparison signal, for example, the high level, that is, the number of the waveforms of the current comparison signal, and determines the number of times (for example, the number of the waveforms of the current comparison signal) (for example, the number of times that the current IS of the sensing resistor RS is greater than the current threshold value in each of the maximum duty cycle intervals MDUTY) to determine whether the current limiting protection system and method of the motor pre-driver according to the embodiment of the present application is in the normal state or the abnormal state. Figure 7When the number of times reaches the threshold (as shown in the example of 2 times), a rest protection procedure is executed.

[0064] Alternatively, the control circuit 20 counts how many consecutive first signals OT1S and second signals OT2S have a current IS greater than a current threshold within the maximum operating cycle interval MDUTY. When the control circuit 20 determines that the number of counted maximum operating cycle intervals MDUTY is greater than a certain threshold, it executes a rest protection procedure.

[0065] Alternatively, as in this embodiment, both of the aforementioned conditions can be used as conditions for executing the rest protection procedure. That is, the control circuit 20 determines, based on the current comparison signal, that the number of times the current IS of the sensing resistor RS exceeds the current threshold (first count value) within each maximum operating cycle interval MDUTY reaches a threshold value of one, for example, 2 times, and the number of consecutive maximum operating cycle intervals MDUTY in which the current IS of the sensing resistor RS exceeds the current threshold (second count value) reaches a threshold value of four times, and then executes the rest protection procedure.

[0066] For example, in this embodiment, such as Figure 7 As shown, within each maximum operating cycle interval MDUTY of the second signal OT2S, when the current IS of the sensing resistor RS detected at two different time points is greater than the current threshold, the first count value is 2, and the start counting signal CCT1 changes from low level to high level, indicating that the control circuit 20 starts counting the second count value according to the current comparison signal.

[0067] Next, as Figure 7 As shown, when the consecutive number threshold of the second signal OT2S, for example, within each of the four maximum operating cycle intervals MDUTY, occurs at two different time points, the current IS of the sense resistor RS detected is greater than the current threshold, the second count value is 4. In this case, as... Figure 7 The rest protection program start signal CLN1 changes from low to high, indicating that the rest protection program has started.

[0068] Please see Figure 8 This is a second schematic diagram of the current limiting protection system and method for the motor front driver according to an embodiment of the present invention, which compares the current with the current threshold multiple times in each of the multiple maximum working cycle intervals of the first signal and the second signal.

[0069] The control circuit 20 judges whether the number of times (first count value) that the current IS of the sensing resistor RS is greater than the current threshold value within each maximum duty interval MDUTY reaches the number threshold value of 3 (number threshold value) indicated by the start count signal CCT2 and the number of consecutive maximum duty intervals MDUTY (second count value) that the current IS of the sensing resistor RS is greater than the current threshold value reaches the number threshold value of 8 (number threshold value) indicated by the rest protection program start signal CLN2 based on the current comparison signal, and turns from low to high as shown in FIG. 8 when the number threshold value is reached. At this time, the rest protection program is started to turn off the first upper bridge switch Hl and the second upper bridge switch H2, and the first lower bridge switch LI and the second lower bridge switch L2 are turned on alternately based on the level of the phase change signal PHS. Figure 8 As shown in FIG. 8, the rest protection program is started when the number threshold value is reached. At this time, the rest protection program is started to turn off the first upper bridge switch Hl and the second upper bridge switch H2, and the first lower bridge switch LI and the second lower bridge switch L2 are turned on alternately based on the level of the phase change signal PHS.

[0070] In the embodiment, the number threshold value is 3 and the number threshold value is 8, which are only examples. In fact, the number threshold value and the number threshold value can be set according to actual needs.

[0071] During the execution of the rest protection program, the rotation speed of the single-phase motor MT gradually decreases until the control circuit 20 judges that the rotation speed of the single-phase motor MT decreases to stop the fan, and the execution of the rest protection program is stopped as shown in FIG. 8 when the rotation speed of the single-phase motor MT decreases to stop the fan. At this time, the rest protection program is started to turn off the first upper bridge switch Hl and the second upper bridge switch H2, and the first lower bridge switch LI and the second lower bridge switch L2 are turned on alternately based on the level of the phase change signal PHS. Figure 8 As shown in FIG. 8, the rest protection program is started when the number threshold value is reached. At this time, the rest protection program is started to turn off the first upper bridge switch Hl and the second upper bridge switch H2, and the first lower bridge switch LI and the second lower bridge switch L2 are turned on alternately based on the level of the phase change signal PHS. Figure 8 As shown in FIG. 8, the rest protection program is started when the number threshold value is reached. At this time, the rest protection program is started to turn off the first upper bridge switch Hl and the second upper bridge switch H2, and the first lower bridge switch LI and the second lower bridge switch L2 are turned on alternately based on the level of the phase change signal PHS.

[0072] In summary, the application provides a current limiting protection system and method for a motor pre-driver, which has the following main features:

[0073] Detecting a sensing resistor connected to the motor to detect the current of the motor;

[0074] Comparing the current of the sensing resistor with a current threshold value through the motor pre-driver circuit to judge whether current limiting occurs within the maximum duty interval of the signal of the motor;

[0075] If the current limiting occurs at a time outside the maximum duty interval, only the current limiting program is executed, and if the current limiting occurs within the maximum duty interval, the rest protection program is forced to be executed to prevent the temperature of the multiple switch components such as transistors of the bridge drive circuit from being too high.

[0076] The above disclosure is only a preferred and feasible embodiment of the application, and does not limit the scope of claims of the application, so any equivalent technical changes made according to the content of the specification and drawings of the application are included in the scope of claims of the application.

Claims

1. A current limit protection system for a motor pre-driver, the current limit protection system being adapted for use with a bridge drive circuit for a single phase motor, the bridge drive circuit comprising a plurality of switching components, the plurality of switching components comprising a first upper bridge switch, a first lower bridge switch, a second upper bridge switch, and a second lower bridge switch, a first terminal of the first upper bridge switch and a first terminal of the second upper bridge switch being coupled to a shared voltage, a first node between a second terminal of the first upper bridge switch and a first terminal of the first lower bridge switch connecting a first terminal of the single phase motor, a second node between a second terminal of the second upper bridge switch and a first terminal of the second lower bridge switch connecting a second terminal of the single phase motor, a second terminal of the second upper bridge switch and a second terminal of the second lower bridge switch connecting a first terminal of a sense resistor, a second terminal of the sense resistor being connected to ground, characterized by, The current limit protection system of the motor pre-driver comprises: a current limit circuit connected to a first end of the sense resistor, the current limit circuit configured to detect a current of the sense resistor, and then compare the current of the sense resistor with a current threshold to output a current comparison signal; and a control circuit connected to control terminals of the switch components and the current limit circuit, the control circuit configured to output a plurality of control signals to the switch components according to the current comparison signal to turn on or turn off the switch components; wherein, when the control circuit determines that the current of the sense resistor is greater than the current threshold according to the current comparison signal, and the current time reaches a maximum duty cycle interval of a first signal of the first node or a second signal of the second node, the control circuit executes a rest protection procedure in a fixed time to maintain turning off the first upper bridge switch and the second upper bridge switch, and turn on the first lower bridge switch and the second lower bridge switch alternately in the fixed time; wherein, in the maximum duty cycle interval but before reaching the fixed time, the control circuit counts the number of times that the current limit circuit compares the current of the sense resistor to be greater than the current threshold according to the level of the current comparison signal, and executes the rest protection procedure in the fixed time when determining that the number of times reaches a number threshold.

2. The current limit protection system for a motor pre-drive of claim 1, wherein, In the maximum duty cycle interval of the first signal when the current of the sense resistor is greater than the current threshold but before reaching the fixed time, current flows from the first upper bridge switch to the single-phase motor, and then flows to the sense resistor through the second lower bridge switch, and in the maximum duty cycle interval of the second signal when the current of the sense resistor is greater than the current threshold but before reaching the fixed time, current flows from the second upper bridge switch to the single-phase motor, and then flows to the sense resistor through the first lower bridge switch.

3. The current limit protection system for a motor pre-drive of claim 1, wherein, Each of the first signal and the second signal has a plurality of the maximum duty cycle intervals, the control circuit counts the number of consecutive maximum duty cycle intervals in which the current of the sense resistor is greater than the current threshold according to the level of the current comparison signal, and executes the rest protection procedure when determining that the number is greater than a number threshold.

4. The current limit protection system for a motor pre-drive of claim 1, wherein, Each of the first signal and the second signal has a plurality of the maximum duty cycle intervals, the control circuit determines that the number of times that the current of the sense resistor is greater than the current threshold in each of the maximum duty cycle intervals reaches a number threshold according to the current comparison signal, and executes the rest protection procedure when the number of consecutive maximum duty cycle intervals in which the current of the sense resistor is greater than the current threshold reaches a number threshold.

5. A current limit protection method for a motor pre-driver, the current limit protection method is applicable to a bridge drive circuit of a single-phase motor, the bridge drive circuit comprises a plurality of switching components, the plurality of switching components comprises a first upper bridge switch, a first lower bridge switch, a second upper bridge switch and a second lower bridge switch, a first end of the first upper bridge switch and a first end of the second upper bridge switch are coupled to a shared voltage, a first node between a second end of the first upper bridge switch and a first end of the first lower bridge switch is connected to a first end of the single-phase motor, a second node between a second end of the second upper bridge switch and a first end of the second lower bridge switch is connected to a second end of the single-phase motor, a second end of the second upper bridge switch and a second end of the second lower bridge switch are connected to a first end of a sense resistor, a second end of the sense resistor is grounded, characterized in that, The current limit protection method of the motor pre-driver comprises the following steps: (a) detecting a current of the sense resistor; (b) determining whether the current of the sensing resistor is greater than a current threshold, if not, returning to step (a), if yes, performing step (c); (c) determining whether the current time reaches a maximum duty cycle interval of the first signal of the first node or the second signal of the second node and a duty cycle of the first signal or the second signal is equal to a default cycle, if not, switching the plurality of switching components, adjusting the duty cycle of the first signal or the second signal to limit the current flowing through each of the switching components, controlling the single-phase motor to operate stably, and then returning to step (a), if yes, performing step (d); (d) turning off the first upper bridge switch and the second upper bridge switch for a fixed time, and turning on the first lower bridge switch and the second lower bridge switch alternately; and (e) automatically turning on the first upper bridge switch or the second upper bridge switch again at the end of the fixed time, and controlling the single-phase motor to operate stably.

6. The motor pre-driver current limit protection method of claim 5, wherein, The current limiting protection method of the motor pre-driver further comprises the following steps: when the current time is within the maximum duty cycle interval of the first signal but has not reached the fixed time, allowing the current to flow from the first upper bridge switch to the single-phase motor, and then to the sensing resistor through the second lower bridge switch, and when the current time is within the maximum duty cycle interval of the second signal but has not reached the fixed time, allowing the current to flow from the second upper bridge switch to the single-phase motor, and then to the sensing resistor through the first lower bridge switch.

7. The motor pre-driver current limit protection method of claim 5, wherein, The current limiting protection method of the motor pre-driver further comprises the following steps: counting the number of times that the current of the sensing resistor is greater than the current threshold within the maximum duty cycle interval; and determining whether the number of times reaches a number of times threshold, if not, returning to the previous step, if yes, performing a rest protection program.

8. The motor pre-driver current limit protection method according to claim 5 or 7, wherein, The current limiting protection method of the motor pre-driver further comprises the following steps: detecting the current of the sensing resistor multiple times; comparing the current of the sensing resistor with the current threshold multiple times to output multiple waveforms of a current comparison signal; counting how many consecutive maximum duty cycle intervals in the first signal or the second signal the current of the sensing resistor is greater than the current threshold to obtain a number of maximum duty cycle intervals; and determining whether the number of maximum duty cycle intervals is greater than a number threshold, if not, returning to the previous step, if yes, performing a rest protection program.

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