Current monitoring method of PTC (Positive Temperature Coefficient) circuit and PTC circuit

Abstract

The invention discloses a current monitoring method and circuit of a PTC (Positive Temperature Coefficient) circuit. The PTC circuit comprises a control module, at least two PTC branches and a current sampling module. The at least two PTC branches are connected between the control module and the power supply, and the current sampling module is respectively connected with the at least two PTC branches. The method comprises the following steps: inputting control signals to at least two PTC branches; acquiring sampling current at a plurality of sampling moments through a current sampling module; according to the control signal, determining effective sampling current of the effective sampling moments corresponding to the at least two PTC branches; the effective sampling current comprises the current of a single PTC branch; and determining currents corresponding to the at least two PTC branches according to the plurality of effective sampling currents. According to the technical scheme provided by the embodiment of the invention, the current of a plurality of PTC branches can be obtained through one current acquisition module, so that the circuit cost is effectively reduced, the interface resource of the control module is saved, and the accuracy of the monitored current of the PTC branches is improved.

Description

Technical Field

[0001] The present invention relates to the field of heating technology, and in particular to a current monitoring method of a PTC circuit and a PTC circuit. Background Art

[0002] PTC (Positive Temperature Coefficient) heaters have advantages that conventional heating components cannot match, such as constant temperature heating, no open flame, high heat conversion efficiency, little influence from power supply voltage, long natural life, energy saving, no oxygen consumption, and easy adjustment of heating value. They can be used in air conditioning heaters, dryers, heaters, and small household appliances. Especially with the popularization of new energy vehicles and the increasing market share year by year, PTC has become an indispensable component in the vehicle heating system.

[0003] In the vehicle heating system, PTC heater plays an important role. Most of the intelligent PTC heaters on the market can achieve the effect of infinite power change by adjusting the power. During use, the controller needs to monitor the open circuit and short circuit fault characteristics of the PTC, and the current of the PTC must be monitored to adjust the PTC power. The existing PTC circuit requires the use of a multi-channel current acquisition device to monitor the current of the PTC on each branch, but this increases the cost, wastes the interface resources of the controller, and the monitored current value has a large deviation. Summary of the invention

[0004] The present invention provides a current monitoring method for a PTC circuit and a PTC circuit, which monitor multiple PTC branches through a current acquisition module, reduce circuit cost, and improve the accuracy of PTC current monitoring.

[0005] According to one aspect of the present invention, a current monitoring method for a PTC circuit is provided, characterized in that the PTC circuit comprises: a control module, at least two PTC branches and a current sampling module; at least two of the PTC branches are connected between the control module and a power supply, and the current sampling module is respectively connected to the at least two PTC branches;

[0006] Current monitoring methods for PTC circuits include:

[0007] Inputting a control signal to at least two of the PTC branches;

[0008] Acquiring sampling currents at multiple sampling moments through the current sampling module;

[0009] Determine, according to the control signal, effective sampling currents at effective sampling moments corresponding to at least two of the PTC branches; the effective sampling currents include currents of a single PTC branch;

[0010] Determine the currents corresponding to at least two of the PTC branches according to the multiple effective sampling currents.

[0011] Optionally, inputting control signals to at least two of the PTC branches includes:

[0012] Input PWM signals with a preset duty cycle to at least two of the PTC branches respectively according to a preset time interval;

[0013] When the preset duty cycle a is greater than 0 and less than 1, and the number n of the PTC branches is greater than 2, the preset time interval satisfies Ta < Δt < T / n; where T is the time period of the PWM signal.

[0014] Optionally, the time intervals between the multiple sampling moments are the same.

[0015] Optionally, determining the effective sampling currents at the effective sampling moments corresponding to at least two of the PTC branches according to the control signals includes:

[0016] Determine the number of the effective sampling moments of each of the PTC branches according to the preset duty cycle;

[0017] Determine the multiple effective sampling currents corresponding to at least two of the PTC branches according to the number of the effective sampling moments.

[0018] Optionally, determining the number of the effective sampling moments of each of the PTC branches according to the preset duty cycle includes:

[0019] When 0 < a ≤ 50%, determine the number of the effective sampling moments according to the following formula:

[0020] N = a × M,

[0021] When 50% < a < 1, determine the number of the effective sampling moments according to the following formula:

[0022] N = M - (a × M),

[0023] where N is the number of the effective sampling moments, N is rounded down, a is the preset duty cycle, and M is the total number of the sampling moments.

[0024] Optionally, determining the multiple effective sampling currents corresponding to at least two of the PTC branches according to the number of the effective sampling moments and the switching states of at least two of the PTC branches includes:

[0025] During the conduction time of a single PTC branch, determine the sampling currents at N sampling moments as the effective sampling currents corresponding to the PTC branch.

[0026] Optionally, determining the currents corresponding to at least two of the PTC branches according to the multiple effective sampled currents includes:

[0027] The currents corresponding to at least two of the PTC branches are determined according to an average value of the plurality of effective sampled currents.

[0028] Optionally, after determining the currents corresponding to at least two of the PTC branches according to the multiple effective sampled currents, the method further includes:

[0029] An open circuit fault diagnosis and / or a short circuit fault diagnosis is performed according to the current corresponding to the PTC branch and the switch state of the PTC branch.

[0030] Optionally, performing short circuit fault diagnosis according to the current corresponding to the PTC branch and the sum of currents corresponding to at least two of the PTC branches includes:

[0031] Input a PWM signal with a fixed duty cycle to the PTC circuit to obtain the total current of the PTC circuit;

[0032] A PWM signal with a fixed duty cycle is inputted to a preset PTC branch alone. If the current corresponding to the preset PTC branch is less than the total current, a short circuit fault is diagnosed in the preset PTC branch.

[0033] According to another aspect of the present invention, a PTC circuit is provided, which is used to perform the current monitoring method of the PTC circuit provided in any embodiment of the present invention, and the PTC circuit includes:

[0034] Control module, at least two PTC branches and current sampling module

[0035] The first end of the PTC branch is connected to the control module, the second end of the PTC branch is connected to the power supply, and the third end of the PTC branch is connected to the first end of the current sampling module;

[0036] The second end of the current sampling module is connected to the control module, the third end of the current sampling module is grounded, and the current sampling module is used to obtain sampling currents of at least two of the PTC branches.

[0037] The technical solution provided by the embodiment of the present invention controls the on or off of multiple PTC branches by sending a control signal through a control module, and obtains the current of multiple PTC branches at multiple sampling moments through a current acquisition module; the control module selects the effective sampling current when each PTC branch is turned on alone from the sampling currents obtained at multiple sampling moments according to the on and off states of the PTC branch, and calculates the current corresponding to each PTC branch according to the multiple effective sampling currents. The technical solution provided by the embodiment of the present invention can obtain the current of multiple PTC branches through a current acquisition module, effectively reducing the circuit cost and saving the interface resources of the control module, and the current corresponding to each PTC branch is calculated through multiple effective sampling currents to improve the accuracy of the calculated current of each PTC branch.

[0038] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0040] Figure 1 A schematic diagram of the structure of a PTC circuit provided by an embodiment of the present invention;

[0041] Figure 2 A flow chart of a current monitoring method for a PTC circuit provided by an embodiment of the present invention;

[0042] Figure 3 A flow chart of another current monitoring method for a PTC circuit provided by an embodiment of the present invention;

[0043] Figure 4 A current timing diagram of a PTC circuit when a PWM signal duty cycle is 25% provided in an embodiment of the present invention;

[0044] Figure 5 A current timing diagram of a PTC circuit when the duty cycle of a PWM signal is 20% provided in another embodiment of the present invention;

[0045] Figure 6 A flow chart of another current monitoring method for a PTC circuit provided by an embodiment of the present invention;

[0046] Figure 7A flow chart of another current monitoring method for a PTC circuit provided by an embodiment of the present invention;

[0047] Figure 8 A current timing diagram of a PTC circuit when a PWM signal duty cycle is 50% provided in an embodiment of the present invention;

[0048] Fig. 9 A current timing diagram of a PTC circuit when a PWM signal duty cycle is 75% provided in an embodiment of the present invention;

[0049] Fig.10 A flow chart of another current monitoring method for a PTC circuit provided by an embodiment of the present invention;

[0050] Fig.11 A flow chart of another current monitoring method for a PTC circuit provided by an embodiment of the present invention;

[0051] Fig.12 A schematic structural diagram of another PTC circuit provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0052] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0053] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0054] Figure 1 A structural schematic diagram of a PTC circuit provided by an embodiment of the present invention. Figure 2The present invention provides a flow chart of a method for monitoring the current of a PTC circuit. This embodiment is applicable to monitoring the current of a PTC circuit. The method can be executed by a control module in the PTC circuit. The control module can be implemented in the form of hardware and / or software. Figure 1 and Figure 2 The PTC circuit includes: a control module 10, at least two PTC branches 20 and a current sampling module 30; at least two PTC branches 20 are connected between the control module 10 and the power supply HV+, and the current sampling module 30 is connected to the at least two PTC branches 20 respectively.

[0055] Specifically, the PTC circuit may be provided with a plurality of PTC branches 20. For example, Figure 1 As shown, the PTC circuit in the embodiment of the present invention is provided with two PTC branches 20, namely PTC branch 201 and PTC branch 202. The control module 10 is respectively connected to one end of the plurality of PTC branches 20, and the other end of the plurality of PTC branches 20 is connected to the power supply HV+. The control module 10 can control the on and off of the plurality of PTC branches 20. The current sampling module 30 is respectively connected to the plurality of PTC branches 20 to sample the current of the plurality of PTC branches 20, and transmits the obtained sampled current to the control module 10. The control module 10 calculates the current of the plurality of PTC branches 20 according to the sampled current obtained by the current sampling module 30, and performs current monitoring on the plurality of PTC branches 20.

[0056] Current monitoring methods for PTC circuits include:

[0057] S110, inputting a control signal to at least two PTC branches;

[0058] Specifically, the control module 10 can send control signals to multiple PTC branches 20 to control the multiple PTC branches 20 to be turned on or off. Multiple PTC branches 20 can be turned on at the same time, and multiple PTC branches 20 can be turned off at the same time. The control module 10 can adjust the power of the PTC circuit by controlling the number of PTC branches 20 turned on and the number of PTC branches 20 turned off, so as to achieve the effect of infinite power change.

[0059] S120, obtaining sampling currents at multiple sampling moments through a current sampling module;

[0060] Specifically, when the control module 10 controls multiple PTC branches 20 to turn on or off, the current sampling module 30 can sample the current of the PTC branches 20 at different times, thereby obtaining multiple sampled currents, which are the total currents of the multiple PTC branches 20. At different sampling times, the switch states of the various PTC branches 20 may be partially the same or different. Figure 1Taking the PTC circuit shown as an example, at one sampling moment, the PTC branch 201 can be in an on state, and the PTC branch 202 can be in an off state; at another sampling moment, the PTC branch 201 and the PTC branch 202 can both be in an off state, or both can be in an on state. The current sampling module 30 can be a current acquisition sensor, and the current sensor can use Hall current sensing to perform current sampling on multiple PTC branches 20.

[0061] S130, determining effective sampling currents at effective sampling moments corresponding to at least two PTC branches according to the control signal; the effective sampling currents include the current of a single PTC branch;

[0062] Specifically, the effective sampling moment may be the sampling moment when only one PTC branch 20 in the PTC circuit is in the on state, while the other PTC branches 20 are in the off state. Correspondingly, the sampling current obtained by sampling by the current sampling module 30 at the effective sampling moment is the effective sampling current. The effective sampling current is the current of the PTC branch 20 that is in the on state alone. For example, Figure 1 Taking the PTC circuit shown as an example, if at a sampling moment, the PTC branch 201 is in the on state and the PTC branch 202 is in the off state, and only the PTC branch 201 is turned on alone, then the sampling moment is the effective sampling moment, and the sampling current obtained at the sampling moment is the effective sampling current.

[0063] S140: Determine currents corresponding to at least two PTC branches according to a plurality of valid sampled currents.

[0064] Specifically, there may be multiple sampling moments in a time period of the control signal, and some of the multiple sampling moments are confirmed as valid sampling moments. The valid sampling current corresponding to the valid sampling moment when the same PTC branch is turned on alone is screened out, so as to calculate the current corresponding to the PTC branch. Figure 1 Taking the PTC circuit shown as an example, effective sampling moments can be screened out from multiple sampling moments, each effective sampling moment corresponds to an effective sampling current, and the current corresponding to the PTC branch 201 is calculated based on the screened multiple effective sampling currents.

[0065] The technical solution provided by the embodiment of the present invention controls the on or off of multiple PTC branches by sending a control signal through a control module, and obtains the current of multiple PTC branches at multiple sampling moments through a current acquisition module; the control module selects the effective sampling current when each PTC branch is turned on alone from the sampling currents obtained at multiple sampling moments according to the on and off states of the PTC branch, and calculates the current corresponding to each PTC branch according to the multiple effective sampling currents. The technical solution provided by the embodiment of the present invention can obtain the current of multiple PTC branches through a current acquisition module, effectively reducing the circuit cost and saving the interface resources of the control module, and the current corresponding to each PTC branch is calculated through multiple effective sampling currents to improve the accuracy of the calculated current of each PTC branch.

[0066] Optionally, Figure 3 A flow chart of another current monitoring method for a PTC circuit provided by an embodiment of the present invention. Figure 4 A current timing diagram of a PTC circuit when a PWM signal duty cycle is 25% is provided in an embodiment of the present invention. Figure 5 Another current timing diagram of a PTC circuit when the duty cycle of a PWM signal is 20% is provided in an embodiment of the present invention. Figure 1 , Figure 3 , Figure 4 and Figure 5 Inputting control signals to at least two PTC branches includes:

[0067] S210, inputting PWM signals with preset duty cycles to at least two PTC branches respectively according to preset time intervals;

[0068] Specifically, the control signal sent by the control module 10 may be a PWM (Pulse-Width Modulation) signal with a certain duty cycle. The duty cycles of the PWM signals of the multiple PTC branches 20 may all be a preset duty cycle a. The PTC branch 20 may be in an on state when the PWM signal is at a high level. The control module 10 may send PWM signals with a preset duty cycle a to the multiple PTC branches 20 at preset time intervals, respectively, so that there is a turn-on time difference between the multiple PTC branches 20. Wherein, when the preset duty cycle a is greater than 0 and less than 1, and the number of PTC branches n>2, the preset time interval satisfies the relationship Ta<Δt<T / n; wherein T is the time period of the PWM signal.

[0069] For example, Figure 1 The PTC circuit shown is provided with two PTC branches, where PTC branch 201 includes PTC1 and PTC branch 202 includes PTC2. Figure 4As shown, the time period T of the PWM signal is 50ms, the preset duty cycle a is 25%, and I is the total current of the PTC circuit. In one time period, the duration of the PWM signal at a high level is 50ms×25%=12.5ms. When the preset time interval Δt is 25ms, within 0-12.5ms, the PWM signal of the PTC branch 201 is at a high level, and the PTC branch 201 is in a conducting state during this time period; within 25-27.5ms, the PWM signal of the PTC branch 202 is at a high level, and the PTC branch 202 is in a conducting state during this time period.

[0070] It should be noted that, when the PTC circuit includes only two PTC branches, the preset time interval Δt can be greater than 0. When the number of PTC branches included in the PTC circuit is n>2, the preset time interval and the preset duty cycle and the time period need to satisfy the relationship Ta<Δt<T / n. The reason for this setting is that it is necessary to ensure that when the PTC circuit includes multiple PTC branches, there is a state in which one PTC branch is turned on alone within a time period. In one embodiment, the PTC circuit may include three PTC branches, the first PTC branch includes PTC1, the second PTC branch includes PTC2, and the third PTC branch includes PTC3. For example, Figure 5 As shown, the time period T of the PWM signal is 50ms, the preset duty cycle a is 20%, and I is the total current of the PTC circuit. In a time period, the duration of the PWM signal at a high level is 50ms×20%=10ms. When the preset time interval Δt is 15ms, within 0-10ms, the PWM signal of the first PTC branch 201 is at a high level, and the PTC branch 201 is in the on state during this time period; within 15-25ms, the PWM signal of the PTC branch 202 is at a high level, and the PTC branch 202 is in the on state during this time period; within 30-40ms, the PWM signal of the PTC branch 203 is at a high level, and the PTC branch 203 is in the on state during this time period.

[0071] S220, obtaining sampling currents at multiple sampling moments through a current sampling module;

[0072] S230, determining effective sampling currents at effective sampling moments corresponding to at least two PTC branches according to the control signal; the effective sampling currents include currents of a single PTC branch;

[0073] S240: Determine currents corresponding to at least two PTC branches according to a plurality of valid sampled currents.

[0074] Optionally, based on the above embodiment, continue to refer to Figure 4 The time intervals between multiple sampling moments are the same.

[0075] Specifically, Figure 1 The PTC circuit shown includes two PTC branches. Figure 4 As shown, the time interval can be set to 1ms. If the time corresponding to the first sampling moment is 1ms, the time corresponding to the second sampling moment is 2ms, the time corresponding to the third sampling moment is 3ms, and so on. The same time interval between multiple sampling moments can avoid the acquisition moments being too concentrated or dispersed, reduce the impact of different sampling moments on the acquired sampling current, and improve the accuracy of current monitoring.

[0076] Optionally, Figure 6 A flow chart of another current monitoring method for a PTC circuit provided by an embodiment of the present invention. Figure 6 According to the control signal, determining the effective sampling current at the effective sampling time corresponding to at least two PTC branches includes:

[0077] S310, inputting PWM signals with preset duty cycles to at least two PTC branches respectively according to preset time intervals;

[0078] S320, obtaining sampling currents at multiple sampling moments through a current sampling module;

[0079] S330, determining the number of effective sampling moments of each PTC branch according to a preset duty cycle;

[0080] Specifically, the effective sampling moments may be part of the sampling moments in the time period when the PWM control signal of the PTC branch is at a high level. There are multiple sampling moments in a time period, and the corresponding PTC branch is in the on state only when the PWM control signal is at a high level. Therefore, the number of effective sampling moments when the PTC branch is on can be calculated based on the preset duty cycle and the total number of sampling moments in a period.

[0081] S340, determining a plurality of valid sampling currents corresponding to at least two PTC branches according to the number of valid sampling moments;

[0082] Specifically, after the number of effective sampling moments of a PTC branch is determined, the sampling current corresponding to each effective sampling moment is the current sampled and obtained when the PTC branch is turned on alone.

[0083] S350: Determine currents corresponding to at least two PTC branches according to a plurality of valid sampled currents.

[0084] Optionally, Figure 7 A flow chart of another current monitoring method for a PTC circuit provided by an embodiment of the present invention. Figure 8The current timing diagram of the PTC circuit when the duty cycle of the PWM signal is 50% provided by the embodiment of the present invention. Fig. 9 The current timing diagram of the PTC circuit when the duty cycle of the PWM signal is 75% provided by the embodiment of the present invention. On the basis of the above embodiment, refer to Figure 7 , Figure 8 and Fig. 9 . Determining the number of effective sampling moments of each PTC branch according to the preset duty cycle includes:

[0085] S410. Input PWM signals with a preset duty cycle to at least two PTC branches respectively according to a preset time interval;

[0086] S420. Obtain the sampled current at multiple sampling moments through the current sampling module;

[0087] S430. When 0 < a ≤ 50%, determine the number of effective sampling moments according to the following formula:

[0088] N = a × M, Formula (1)

[0089] Wherein, N is the number of effective sampling moments, N is rounded down, a is the preset duty cycle, and M is the total number of sampling moments.

[0090] Specifically, taking the PTC circuit shown in Figure 1 including two PTC branches as an example for illustration. As shown in Figure 8 , the time period T of the PWM signal is 50 ms, the preset duty cycle a is 50%, and the total number of sampling moments M is 50. Then the number of effective sampling moments N of PTC branch 201 and PTC branch 202 = 50 × 50% = 25, and N is rounded down to 25. That is, within one time period, there are 25 sampling moments corresponding to PTC branch 201 as effective sampling moments; there are 25 sampling moments corresponding to PTC branch 202 as effective sampling moments.

[0091] S440. When 50% < a < 1, determine the number of effective sampling moments according to the following formula:

[0092] N = M - (a × M), Formula (2)

[0093] Wherein, N is the number of effective sampling moments, N is rounded down, a is the preset duty cycle, and M is the total number of sampling moments.

[0094] Specifically, taking the PTC circuit shown in Figure 1 including two PTC branches as an example for illustration. As shown in Fig. 9As shown, the time period T of the PWM signal is 50ms, the preset duty cycle a is 75%, and the total number of sampling moments M is 50. Then the effective sampling moments N of the PTC branch 201 and the PTC branch 202 are 50-(50×75%)=12.5, and N is rounded down to 12. That is, in one time period, the PTC branch 201 has 12 sampling moments corresponding to it as effective sampling moments; and the PTC branch 202 has 12 sampling moments corresponding to it as effective sampling moments.

[0095] S450, during the time when a single PTC branch is turned on, determining that the sampling currents at N sampling moments are effective sampling currents corresponding to the PTC branch;

[0096] Specifically, Figure 1 The PTC circuit shown includes two PTC branches for illustration.

[0097] When (1-a)T≥Δt, the PTC branch 201 can determine the effective sampling time by the following formula:

[0098] t=pb+kT, Formula (3)

[0099] Wherein, b is the time interval between sampling moments, 0<p≤N, k≥0, p and k are both integers, and the effective sampling moment t is rounded down. When (1-a)T≥Δt, the duration of the low level of the PWM signal is greater than the preset time interval Δt, and from the start moment to the first preset time interval, there is no time period in which the two PTC branches are turned on at the same time. The effective sampling moment when the PTC branch 201 is turned on alone can be calculated from the start moment. For example, Figure 4 As shown, when the preset duty cycle a is 25%, the time interval b between sampling moments is 1ms, the preset time interval Δt is 25ms, and the time period T is 50ms, the number N of effective sampling moments of the PTC branch is 12. According to formula (3), in the first time period, the effective sampling moments of the PTC branch 201 are 1ms, 2ms, 3ms, 4ms, 5ms...11ms, 12ms. Correspondingly, the effective sampling moments of the PTC branch 202 are 26ms, 27ms, 28ms, 29ms, 30ms, 31ms...36ms, 37ms after the preset time interval is increased by 25ms. In the next time period, the effective sampling moments of the PTC branch 201 are 51ms, 52ms, 53ms, 54ms, 55ms...61ms, 62ms. Correspondingly, after the preset time interval of 25 ms is increased, the effective sampling moments of the PTC branch 202 are 76 ms, 77 ms, 78 ms, 79 ms, 80 ms, 81 ms ... 86 ms, 87 ms, and so on.

[0100] like Figure 8 As shown, when the preset duty cycle a is 50%, the time interval b between sampling moments is 1ms, the preset time interval Δt is 25ms, and the time period T is 50ms, the number N of effective sampling moments of the PTC branch is 25. According to formula (3), in the first time period, the effective sampling moments of the PTC branch 201 are 1ms, 2ms, 3ms, 4ms, 5ms...24ms, 25ms. Correspondingly, the effective sampling moments of the PTC branch 202 are 26ms, 27ms, 28ms, 29ms, 30ms, 31ms...49ms, 50ms after the preset time interval is increased by 25ms. In the next time period, the effective sampling moments of the PTC branch 201 are 51ms, 52ms, 53ms, 54ms, 55ms...74ms, 75ms. Correspondingly, after the preset time interval of 25 ms is increased, the effective sampling moments of the PTC branch 202 are 76 ms, 77 ms, 78 ms, 79 ms, 80 ms, 81 ms, ... 99 ms, 100 ms, and so on.

[0101] When (1-a)T<Δt, the PTC branch 201 can determine the effective sampling time by the following formula:

[0102] t=Δt-(1-a)T+pb+kT, Formula (4)

[0103] Wherein, b is the time interval between sampling moments, 0<p≤N, k≥0, p and k are both integers, and the effective sampling moment t is rounded down. When (1-a)T<Δt, the duration of the low level of the PWM signal is less than the preset time interval Δt, and from the start moment to the first preset time interval, there is a time period when the two PTC branches are turned on at the same time. The effective sampling moment when the PTC branch 201 is turned on alone needs to be calculated from the moment Δt-(1-a)T. For example, Fig. 9As shown, when the preset duty cycle a is 75%, the time interval b between sampling moments is 1ms, the preset time interval Δt is 25ms, and the time period T is 50ms, the number N of effective sampling moments of the PTC branch is 12. According to formula (4), in the first time period, the effective sampling moments of the PTC branch 201 are 13ms, 14ms, 15ms, 16ms, 17ms...24ms. Correspondingly, the effective sampling moments of the PTC branch 202 are 38ms, 39ms, 40ms, 41ms, 42ms, 43ms...49ms after the preset time interval is increased by 25ms. In the next time period, the effective sampling moments of the PTC branch 201 are 63ms, 64ms, 65ms, 66ms, 67ms...74ms. Correspondingly, after the preset time interval of 25 ms is increased, the effective sampling moments of the PTC branch 202 are 88 ms, 89 ms, 90 ms, 91 ms, 92 ms, 93 ms, ... 99 ms, and so on.

[0104] S460: Determine currents corresponding to at least two PTC branches according to an average value of multiple valid sampled currents.

[0105] Specifically, when the PTC branch is turned on alone, there are N valid sampling moments, and the N valid sampling moments correspond to N valid sampling currents. The current of the PTC branch is calculated by averaging the N valid sampling currents, thereby realizing the monitoring of the current conditions of multiple PTC branches through one current acquisition module.

[0106] Optionally, Fig.10 A flow chart of another current monitoring method for a PTC circuit provided by an embodiment of the present invention. After determining the currents corresponding to at least two PTC branches according to the average value of multiple valid sampled currents, the method further includes:

[0107] S510: Perform open circuit fault diagnosis and / or short circuit fault diagnosis according to the current corresponding to the PTC branch and the switch state of the PTC branch.

[0108] Specifically, when one PTC branch is turned on, if the corresponding current of the monitored PTC branch is zero, an open circuit fault is diagnosed in the PTC branch. When both PTC branches are turned off, if the monitored PTC circuit has a current I, a short circuit fault is diagnosed in the PTC circuit.

[0109] Optionally, Fig.11 A flow chart of another current monitoring method for a PTC circuit provided by an embodiment of the present invention. Performing short circuit fault diagnosis based on the current corresponding to the PTC branch and the sum of the currents corresponding to at least two PTC branches includes:

[0110] S610, inputting a PWM signal with a fixed duty cycle into the PTC circuit to obtain a total current I of the PTC circuit;

[0111] Specifically, the fixed duty cycle may be 100%. Inputting a PWM signal with a fixed duty cycle to all PTC branches in the PTC circuit may make all PTC branches in the on state, thereby calculating the total current I when all PTC branches are in the on state.

[0112] S620: Input a PWM signal with a fixed duty cycle to the preset PTC branch alone. If the current I0 corresponding to the preset PTC branch is less than the total current I, diagnose that a short circuit fault occurs in the preset PTC branch.

[0113] Specifically, the preset PTC branch is a PTC branch that needs to be diagnosed whether a short circuit fault occurs. A PWM signal with a fixed duty cycle is input to the preset PTC branch alone, so as to calculate the current I0 when the preset PTC branch is always in the on state. If the current I0 corresponding to the preset PTC branch is less than the total current I, it is diagnosed that the preset PTC branch has a short circuit fault.

[0114] Fig.12 FIG. 1 is a schematic diagram of a structure of another PTC circuit provided by an embodiment of the present invention. Fig.12 As shown, the PTC circuit provided in the embodiment of the present invention can be used to execute the current monitoring method of the PTC circuit provided in any embodiment of the present invention, and the PTC circuit includes:

[0115] A control module 10, at least two PTC branches 20 and a current sampling module 30;

[0116] A first end of the PTC branch 20 is connected to the control module 10, a second end of the PTC branch 20 is connected to the power source HV+, and a third end of the PTC branch 20 is connected to a first end of the current sampling module 30;

[0117] The second end of the current sampling module 30 is connected to the control module 10, and the third end of the current sampling module 30 is grounded. The current sampling module 30 is used to obtain the sampling current of at least two PTC branches.

[0118] Specifically, the PTC branch 20 may include a driving unit 21, a switch unit 22 and a PTC 23. The first end of the driving unit 21 is connected to the control module 10, and the second end of the driving unit 21 is connected to the control end of the switch unit 22. The driving unit 21 can drive the switch unit 22 to turn on or off according to the control information sent by the control module 10, thereby controlling the PTC branch 20 where the PTC 23 is located to turn on or off. The switch unit 22 may be an IGBT. The gate of the IGBT is connected to the driving unit 21, the emitter of the IGBT is connected to the power supply HV+ through the PTC 23, and the collector of the IGBT is connected to the first end of the current sampling module 30 and then grounded through the current sampling module 30. The control module 10 may be an MCU (MicroController Unit). The second end of the current sampling module 30 is connected to the control module 10, and the current sampling module 30 transmits the collected current to the control module 10, and the current value of each PTC branch 20 can be calculated through the control module 10.

[0119] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0120] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A current monitoring method for a PTC circuit, characterized in that: The PTC circuit includes: a control module, at least two PTC branches, and a current sampling module; at least two of the PTC branches are connected between the control module and a power supply, and the current sampling module is respectively connected to at least two of the PTC branches; The method for monitoring the current of the PTC circuit includes: Inputting a control signal to at least two of the PTC branches; Obtaining sampled currents at a plurality of sampling moments through the current sampling module; Determining the effective sampled currents at the effective sampling moments corresponding to at least two of the PTC branches according to the control signal; the effective sampled currents include the currents of individual PTC branches; Determining the currents corresponding to at least two of the PTC branches according to a plurality of the effective sampled currents.

2. The current monitoring method of the PTC circuit according to claim 1, characterized in that: Inputting a control signal to at least two of the PTC branches includes: According to a preset time interval, respectively inputting PWM signals with a preset duty cycle to at least two of the PTC branches; When the preset duty cycle a is greater than 0 and less than 1, and the number of PTC branches n > 2, the preset time interval Δt satisfies T·a < Δt < T / n; where T is the time period of the PWM signal.

3. The current monitoring method of the PTC circuit according to claim 1, characterized in that: The time intervals between the plurality of sampling moments are the same.

4. The current monitoring method of the PTC circuit according to claim 2, characterized in that: Determining the effective sampled currents at the effective sampling moments corresponding to at least two of the PTC branches according to the control signal includes: Determining the number of the effective sampling moments of each of the PTC branches according to the preset duty cycle; Determining a plurality of the effective sampled currents corresponding to at least two of the PTC branches according to the number of the effective sampling moments.

5. The current monitoring method of a PTC circuit according to claim 4, characterized in that: Determining the number of the effective sampling moments of each of the PTC branches according to the preset duty cycle includes: When 0 < a ≤ 50%, determining the number of the effective sampling moments according to the following formula: N = a×M, When 50% < a < 1, determining the number of the effective sampling moments according to the following formula: N = M-(a×M), where N is the number of the effective sampling moments, N is rounded down, a is the preset duty cycle, and M is the total number of the sampling moments.

6. The current monitoring method of a PTC circuit according to claim 5, characterized in that: Determining a plurality of the effective sampled currents corresponding to at least two of the PTC branches according to the number of the effective sampling moments and the switching states of at least two of the PTC branches includes: During the time when a single PTC branch is conducting, determining the sampled currents at N sampling moments as the effective sampled currents corresponding to the PTC branch.

7. The current monitoring method of a PTC circuit according to claim 1, characterized in that: Determining the currents corresponding to at least two of the PTC branches according to a plurality of the effective sampled currents includes: Determining the currents corresponding to at least two of the PTC branches according to the average value of a plurality of the effective sampled currents.

8. The current monitoring method of a PTC circuit according to claim 1, characterized in that: After determining the currents corresponding to at least two of the PTC branches according to a plurality of the effective sampled currents, it further includes: Performing open-circuit fault diagnosis and / or short-circuit fault diagnosis according to the current corresponding to the PTC branch and the switching state of the PTC branch.

9. The current monitoring method of a PTC circuit according to claim 8, characterized in that: Performing short-circuit fault diagnosis according to the current corresponding to the PTC branch and the sum of the currents corresponding to at least two of the PTC branches includes: Inputting a PWM signal with a fixed duty cycle to the PTC circuit and obtaining the total current of the PTC circuit; A PWM signal with a fixed duty cycle is inputted into a preset PTC branch alone. If the current corresponding to the preset PTC branch is less than the total current, a short circuit fault is diagnosed in the preset PTC branch.

10. A PTC circuit, characterized in that: A method for monitoring a current of a PTC circuit according to any one of claims 1 to 9, wherein the PTC circuit comprises: Control module, at least two PTC branches and current sampling module The first end of the PTC branch is connected to the control module, the second end of the PTC branch is connected to the power supply, and the third end of the PTC branch is connected to the first end of the current sampling module; The second end of the current sampling module is connected to the control module, the third end of the current sampling module is grounded, and the current sampling module is used to obtain sampling currents of at least two of the PTC branches.

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