Excitation inrush current suppression circuit

Abstract

The invention provides an excitation inrush current suppression circuit, which relates to the technical field of power electronics and comprises a main control unit, a PTC (Positive Temperature Coefficient) thermistor, a first relay circuit, a mains supply connecting end and a power supply interface, the PTC thermistor and the first relay circuit are connected in series between the commercial power connecting end and the power supply interface, the commercial power connecting end is used for being connected with commercial power, and the power supply interface is used for being connected with an alternating-current adapter; the first control end of the main control unit is connected with the first controlled end of the first relay circuit; the main control unit is used for controlling the first relay circuit to be switched on under the condition that a first instruction for switching on the alternating current adapter is received, so that the PTC thermistor is switched on. According to the technical scheme provided by the invention, excitation inrush current suppression can be realized when the alternating-current adapter is switched on, and the problem that a distribution box control system is restarted due to excitation inrush current generated at the moment that the alternating-current adapter is switched on is avoided.

Description

Technical Field

[0001] The present invention relates to the field of power electronics technology, and particularly to an inrush current suppression circuit. Background Art

[0002] The intelligent distribution box can be connected to an AC adapter through a controllable mains power external power supply interface, and the AC adapter is used to convert the mains voltage into a voltage suitable for the load. When the AC adapter is connected, the intelligent distribution box can control the connection or disconnection of the AC adapter.

[0003] The AC adapter belongs to a power frequency transformer. At the moment when the intelligent distribution box controls the AC adapter to be turned on, especially for an unloaded AC adapter, the AC adapter will generate a transient current. The total magnetic flux between the magnetic flux corresponding to the transient current and the residual magnetism of the AC adapter far exceeds the saturation magnetic flux of the iron core, causing the iron core to be saturated instantaneously, and then generating a large impact excitation current, that is, the inrush current. The inrush current will form a high-frequency harmonic oscillation voltage on the inductive load, and this part of the energy will be fed back to the intelligent distribution box through the line, interfering with the intelligent distribution box control system and causing the system to restart.

[0004] Therefore, in the circuit for the intelligent distribution box to control the AC adapter, suppressing the inrush current is particularly important and is a technical problem that needs to be solved urgently at present. Summary of the Invention

[0005] The present invention provides an inrush current suppression circuit to solve the problem that the inrush current generated when the intelligent distribution box controls the AC adapter to be turned on in the prior art will cause the intelligent distribution box control system to restart, and realizes the suppression of the inrush current when the AC adapter is turned on.

[0006] The present invention provides an inrush current suppression circuit, including a main control unit, a PTC thermistor, a first relay circuit, a mains connection end, and a power supply interface;

[0007] The PTC thermistor and the first relay circuit are connected in series between the mains connection end and the power supply interface. The mains connection end is used to connect to the mains, and the power supply interface is used to connect to the AC adapter;

[0008] The first control end of the main control unit is connected to the first controlled end of the first relay circuit; the main control unit is used to control the first relay circuit to conduct to connect the PTC thermistor when receiving a first instruction to turn on the AC adapter.

[0009] According to an inrush current suppression circuit provided by the present invention, the main control unit is specifically used for:

[0010] Upon receiving the first instruction, determine the delay duration for sending the closing control instruction to the first relay circuit based on the relay delay operation duration of the first relay circuit and the cycle of the mains power;

[0011] Start timing with the first zero-crossing of the mains power after receiving the first instruction as a reference. When the timing duration is equal to the delay duration, send the closing control instruction to the first relay circuit to control the first relay circuit to conduct when the mains power reaches the target voltage phase angle; wherein, the target voltage phase angle is 90° or 270°.

[0012] According to an inrush current suppression circuit provided by the present invention, when the main control unit determines the delay duration for sending the closing control instruction to the first relay circuit based on the relay delay operation duration of the first relay circuit and the cycle of the mains power, it specifically is used for:

[0013] Determine the remainder of dividing the relay delay operation duration by the first duration;

[0014] When the remainder is greater than the second duration, determine the difference between the third duration and the remainder as the delay duration;

[0015] When the remainder is less than or equal to the second duration, determine the difference between the second duration and the remainder as the delay duration;

[0016] Wherein, the first duration is half a cycle of the mains power, the second duration is 0.25 cycles of the mains power, and the third duration is 0.75 cycles of the mains power.

[0017] According to an inrush current suppression circuit provided by the present invention, the inrush current suppression circuit further includes a zero-crossing detection circuit;

[0018] The input end of the zero-crossing detection circuit is connected to the mains power connection end, and the output end of the zero-crossing detection circuit is connected to the zero-crossing detection end of the main control unit;

[0019] The zero-crossing detection circuit is used to detect the zero-crossing of the mains power.

[0020] According to an inrush current suppression circuit provided by the present invention, the first relay circuit includes a first relay, a first switching tube, and a first diode;

[0021] The contact switch of the first relay is connected in series with the PTC thermistor, and the first coil of the first relay is connected between the DC voltage source and the first end of the first switching tube;

[0022] The cathode of the first diode is connected to the DC voltage source, and the anode of the first diode is connected to the first end of the first switching tube;

[0023] The second end of the first switching tube serves as the first controlled end and is connected to the first control end of the main control unit, and the third end of the first switching tube is grounded; the first switching tube conducts when receiving the closing control instruction sent by the first control end to control the conduction of the first relay circuit.

[0024] According to an inrush current suppression circuit provided by the present invention, the first relay circuit further includes a first filter circuit, and the first filter circuit is connected in parallel with the first relay.

[0025] According to an inrush current suppression circuit provided by the present invention, the inrush current suppression circuit further includes a second relay circuit connected in parallel with the PTC thermistor;

[0026] The second control end of the main control unit is connected to the second controlled end of the second relay circuit; the main control unit is further configured to control the conduction of the second relay circuit to short-circuit the PTC thermistor when it is determined that the AC adapter reaches the magnetic balance state.

[0027] According to an inrush current suppression circuit provided by the present invention, the main control unit is further configured to control the second relay circuit to disconnect when the mains reaches the target voltage phase angle when receiving the second instruction to disconnect the AC adapter, and after controlling the disconnection of the second relay circuit, control the first relay circuit to disconnect when it is determined that the AC adapter reaches the magnetic balance state.

[0028] According to an inrush current suppression circuit provided by the present invention, the main control unit is specifically configured to control the first relay circuit to disconnect when the mains reaches the zero-crossing point when it is determined that the AC adapter reaches the magnetic balance state.

[0029] According to an inrush current suppression circuit provided by the present invention, the second relay circuit includes a second relay and a second filter circuit, and the second filter circuit is connected in parallel with the second relay.

[0030] The inrush current suppression circuit provided by the present invention includes a main control unit, a PTC thermistor, a first relay circuit, a mains connection terminal, and a power supply interface. The mains connection terminal is used to connect to the mains, and the power supply interface is used to connect to an AC adapter. The PTC thermistor and the first relay circuit are connected in series between the mains connection terminal and the power supply interface. When the main control unit receives a first instruction to turn on the AC adapter, it controls the first relay circuit to conduct through a first control terminal. At this time, the temperature of the PTC thermistor will increase with the increase of the current, and the resistance value will also increase accordingly, so as to effectively suppress the inrush current in the circuit when the AC adapter is turned on. Description of the Drawings

[0031] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0032] Figure 1 It is a schematic diagram of the corresponding relationship between the magnetic flux and the inrush current of the transformer in the embodiment of the present invention;

[0033] Figure 2 It is one of the structural schematic diagrams of the inrush current suppression circuit provided by the embodiment of the present invention;

[0034] Figure 3 It is a schematic diagram of the corresponding relationship between the magnetic flux of the transformer and the initial phase angle of the voltage in the embodiment of the present invention;

[0035] Figure 4 It is another structural schematic diagram of the inrush current suppression circuit provided by the embodiment of the present invention;

[0036] Figure 5 It is a structural schematic diagram of the zero-crossing detection circuit in the inrush current suppression circuit provided by the embodiment of the present invention;

[0037] Figure 6 It is a structural schematic diagram of the first relay circuit in the inrush current suppression circuit provided by the embodiment of the present invention;

[0038] Figure 7 It is a third structural schematic diagram of the inrush current suppression circuit provided by the embodiment of the present invention;

[0039] Figure 8 It is a fourth structural schematic diagram of the inrush current suppression circuit provided by the embodiment of the present invention;

[0040] Figure 9 It is a schematic diagram of the relay closing control timing in the scenario of turning on the AC adapter in the embodiment of the present invention;

[0041] Figure 10 It is a schematic diagram of the relay closing control timing in the scenario of disconnecting the AC adapter in the embodiments of the present invention. Detailed implementation manners

[0042] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below with reference to the accompanying drawings in the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0043] It should be noted that the serial numbers assigned to the objects described in the present invention itself, such as "first", "second", etc., are only used to distinguish the described objects and do not have any sequential or technical meanings.

[0044] An AC adapter is a power frequency transformer. A transient current will be generated at the moment when the switch is closed. Especially for a power frequency transformer without load, the total magnetic flux between the generated magnetic flux and the residual magnetic flux of the transformer far exceeds the saturation magnetic flux of the iron core, causing the iron core to be saturated instantaneously, and thus a large impact excitation current, that is, inrush current, will be generated. For example, Figure 1 shows a schematic diagram of the corresponding relationship between the magnetic flux of the transformer and the inrush current, taking the voltage phase angle (i.e., closing angle) at the moment when the AC adapter is turned on as 0° as an example, referring to Figure 1 As shown, the change of the magnetic flux will generate a corresponding inrush current. The inrush current will form a high-frequency harmonic oscillation voltage on the inductive load, and this part of the energy will be fed back to the distribution box through the line, interfering with the control system of the distribution box and causing the system to restart.

[0045] To solve the problem that the inrush current will cause the system to restart, the embodiments of the present invention provide an inrush current suppression circuit. A positive temperature coefficient (PTC) thermistor and a first relay circuit are connected in series between the mains connection end for connecting to the mains and the power supply interface for connecting to the AC adapter. The first relay circuit is controlled by the main control unit to conduct, so that the PTC thermistor works to realize the suppression of the inrush current.

[0046] The following will be combined with Figures 2 - 10 to describe the inrush current suppression circuit of the present invention.

[0047] Figure 2 Exemplarily shows one of the schematic diagrams of the structure of the inrush current suppression circuit provided by the embodiments of the present invention, referring to Figure 2As shown, the inrush current suppression circuit includes a main control unit 210, a PTC thermistor RT, a first relay circuit 220, a mains connection terminal S, and a power supply interface P. Among them, the PTC thermistor RT and the first relay circuit 220 are connected in series between the mains connection terminal S and the power supply interface P. The mains connection terminal S is used to connect to the mains AC220V, and the power supply interface P is used to connect to the AC adapter T. The first control terminal CL1 of the main control unit 210 is connected to the first controlled terminal of the first relay circuit 220; the main control unit 210 is configured to control the first relay circuit 220 to conduct when receiving a first instruction to turn on the AC adapter, so as to connect the PTC thermistor RT.

[0048] Exemplarily, the main control unit 210 can be a processor, a microcontroller unit (MCU), or a hardware control circuit, etc. Among them, the processor can include a central processing unit (CPU), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The hardware control circuit can be implemented based on a timer circuit, for example.

[0049] Exemplarily, the main control unit 210 can receive a first instruction to turn on the AC adapter sent by the user through a physical button, a touch button, a remote control, etc., or the main control unit 210 can receive a first instruction for turning on the AC adapter triggered by program timing.

[0050] According to Figure 2 For the inrush current suppression circuit shown, after the main control unit 210 receives the first instruction to turn on the AC adapter, it can control the first relay circuit 220 to conduct through the first control terminal CL1, so as to connect the PTC thermistor RT. At this time, the temperature of the PTC thermistor RT will increase with the increase of the current in the circuit, and the resistance value will also increase accordingly, thereby effectively suppressing the inrush current generated when the AC adapter is turned on and avoiding the influence of the inrush current on the system.

[0051] The inrush current suppression circuit provided by the embodiment of the present invention includes a main control unit, a PTC thermistor, a first relay circuit, a mains connection end, and a power supply interface. The mains connection end is used to connect to the mains, and the power supply interface is used to connect to an AC adapter. The PTC thermistor and the first relay circuit are connected in series between the mains connection end and the power supply interface. When the main control unit receives a first instruction to turn on the AC adapter, it controls the first relay circuit to conduct through the first control end. At this time, the temperature of the PTC thermistor will increase with the increase of the current, and the resistance value will also increase accordingly, so as to effectively suppress the inrush current in the circuit when the AC adapter is turned on.

[0052] For a lossless transformer, its magnetic flux can be expressed by the following formula (1):

[0053] Φ = Φ m [cosα - cos(ωt + α)] = Φ m cosα - Φ m cos(ωt + α) (1)

[0054] Wherein, α is the voltage initial phase angle, ω represents the angular frequency, t represents time, Φ m cos(ωt + α) represents the steady-state magnetic flux, Φ m cosα represents the bias magnetic flux, and in the embodiment of the present invention, it can be represented by Φ p to represent the bias magnetic flux.

[0055] Based on the above formula (1), Figure 3 shows a schematic diagram of the correspondence between the transformer magnetic flux and the voltage initial phase angle. By Figure 3 analyzing, the change relationship shown in Table 1 can be obtained among the residual magnetic flux, the bias magnetic flux, and the voltage phase angle when the AC adapter is turned on or off:

[0056] Table 1

[0057] Initial voltage phase angle α 0～π / 2 π / 2～π π～3π / 2 3π / 2～2π <![CDATA[Residual magnetism Φ Res > Negative maximum to 0 0 to positive maximum Positive maximum to 0 0 to negative maximum <![CDATA[Biased magnetic flux Φ p > Positive maximum to 0 0 to negative maximum Negative maximum to 0 0 to positive maximum

[0058] Combined with Figure 2 、 Figure 3As can be seen from Table 1, the bias magnetic flux is the largest when the initial voltage phase angle α (i.e., the voltage phase angle when the AC adapter is connected or disconnected) is 0° or 180°, and the bias magnetic flux is the smallest when the initial voltage phase angle is 90° or 270°. This is because the magnetic flux Φ always lags the voltage by 90° in phase angle. If the voltage of the distribution box just reaches the maximum value at the moment when the AC adapter is connected, the instantaneous value of the magnetic flux is exactly 0, that is, a steady-state magnetic flux is established in the iron core at the beginning. In this case, no exciting inrush current will be generated in the transformer. If the voltage of the distribution box is exactly 0 at the moment when the AC adapter is connected, the magnetic flux established in the iron core is the negative maximum value (i.e., -Φm). Since the magnetic flux in the iron core cannot change suddenly and there is no magnetic flux in the iron core before the AC adapter is connected, the magnetic flux still needs to be kept at 0 at the moment of connection. Therefore, a non-periodic component of magnetic flux appears in the iron core, and its amplitude is Φm. At this time, the total magnetic flux Φ in the iron core should be regarded as the sum of two magnetic fluxes. The magnetic flux in the iron core at the moment when the AC adapter is connected is 2Φm. If there is still residual magnetic flux Φ Res in the iron core at the moment when the AC adapter is connected, the total magnetic flux Φ will be even larger. Therefore, the exciting inrush current generated when the AC adapter is connected at the moment when the instantaneous value of the distribution box voltage is 0 is the most serious.

[0059] Based on this, in an exemplary embodiment of the present invention, the main control unit 210 can control the first relay circuit 220 to conduct when the mains voltage reaches the target voltage phase angle, so that the PTC thermistor RT works to suppress the exciting inrush current. Wherein, the target voltage phase angle is 90° or 270°. In this way, the AC adapter can be connected when the exciting inrush current is the smallest, and the PTC thermistor can effectively suppress the exciting inrush current following the change law of the exciting inrush current.

[0060] Considering that the relay has a certain action delay, in order to ensure that the first relay circuit 220 can conduct at the moment when the mains voltage reaches the target voltage phase angle, in an exemplary embodiment of the present invention, the moment when the main control unit 210 sends the first instruction to the first relay circuit 220 can be determined according to the relay delay action duration of the first relay circuit 220 and the cycle of the mains voltage, so that when the first relay circuit 220 performs the closing action at this moment, the mains voltage just reaches the target voltage phase angle, improving the suppression effect of the exciting inrush current.

[0061] Specifically, according to Figure 2For the exciting inrush current suppression circuit shown, the main control unit 210 can be specifically configured to: when receiving a first instruction, determine the delay duration for sending a closing control instruction to the first relay circuit 220 based on the relay delay operation duration of the first relay circuit 220 and the cycle of the mains power; start timing with the first zero-crossing point of the mains power after receiving the first instruction, and send a closing control instruction to the first relay circuit 220 when the timing duration is equal to the delay duration, so as to control the first relay circuit 220 to conduct when the mains power reaches the target voltage phase angle; where the target voltage phase angle is 90° or 270°.

[0062] Among them, the relay delay operation duration refers to the operation time required for the first relay circuit 220 to completely close and conduct from receiving the first instruction. The cycle of the mains power is 20 ms. The zero-crossing point is the moment when the mains power voltage is 0, and at this time the voltage phase angle is 0° or 180°. The calculated delay duration can ensure that the first relay circuit 220 just closes and conducts at the moment when the mains power reaches the target voltage phase angle.

[0063] Exemplarily, when the main control unit 210 determines the delay duration for sending a closing control instruction to the first relay circuit 220 based on the relay delay operation duration of the first relay circuit 220 and the cycle of the mains power, it is specifically configured to: determine the remainder of the relay delay operation duration divided by the first duration; when the remainder is greater than the second duration, determine the difference between the third duration and the remainder as the delay duration; when the remainder is less than or equal to the second duration, determine the difference between the second duration and the remainder as the delay duration; where the first duration is half of the cycle of the mains power, the second duration is 0.25 of the cycle of the mains power, and the third duration is 0.75 of the cycle of the mains power.

[0064] Specifically, the delay duration Ts for sending a closing control instruction to the first relay circuit 220 can be determined according to the following formula (2):

[0065]

[0066] Among them, T 0 represents the relay delay operation duration, T 1 represents the first duration, T 2 represents the second duration, T 3 represents the third duration, and % represents the remainder operation.

[0067] Exemplarily, the mains power is industrial frequency alternating current with a cycle of 20 ms, then the first duration T 1 = 10 ms, the second duration T 2 = 5 ms, and the third duration T 3 = 15 ms.

[0068] For example, assume that the relay delay action duration is 20 ms, which is the same as one cycle of the mains power. At this time, the mains voltage is at the positive zero-crossing point. Then, in order to ensure that the first relay circuit closes and conducts exactly when the voltage phase angle of the mains power reaches 90° or 270°, the main control unit can delay for 5 ms based on this zero-crossing point and send a closing control instruction to the first relay circuit. In this way, 25 ms after the mains voltage starts from the zero-crossing point, it exactly reaches the 90° phase angle. At this time, the first relay circuit also just closes and conducts, ensuring that the first relay circuit conducts when the mains power reaches the target voltage phase angle.

[0069] For another example, assume that the relay delay action duration is 25 ms. Then, the main control unit can send a closing control instruction to the first relay circuit immediately after the zero-crossing point of the mains power. In this way, 25 ms after the mains voltage starts from the zero-crossing point, it exactly reaches the 90° phase angle. At this time, the first relay circuit also just closes and conducts.

[0070] In one exemplary embodiment, the zero-crossing point of the mains voltage can be detected by a zero-crossing detection circuit. Specifically, Figure 4 Exemplarily shows the second structural schematic diagram of the inrush current suppression circuit provided by the embodiment of the present invention. Refer to Figure 4 As shown, the inrush current suppression circuit further includes a zero-crossing detection circuit 410. The input end (including the first input end A1 and the second input end A2) of the zero-crossing detection circuit 410 is connected to the mains connection end S, and the output end of the zero-crossing detection circuit 410 is connected to the zero-crossing detection end G of the main control unit 210. The zero-crossing detection circuit 410 is used to detect the zero-crossing point of the mains AC220V.

[0071] Among them, the zero-crossing detection circuit 410 includes a zero-crossing detection circuit based on a comparator, a zero-crossing detection circuit based on a triode, or a zero-crossing detection circuit based on analog-to-digital converter (ADC) sampling, etc.

[0072] Exemplarily, taking the zero-crossing detection circuit 410 as a zero-crossing detection circuit based on a comparator as an example, Figure 5 Exemplarily shows the structural schematic diagram of the zero-crossing detection circuit. Refer to Figure 5As shown, the zero-crossing detection circuit 410 may include a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a first capacitor C1, and a comparator 411. Among them, the first input terminal A1 of the zero-crossing detection circuit 410 is connected to the non-inverting input terminal of the comparator 411 through the first resistor R1, and the second input terminal A2 of the zero-crossing detection circuit 410 is connected to the inverting input terminal of the comparator 411 through the second resistor R2. The non-inverting input terminal and the inverting input terminal of the comparator 411 are connected through the first capacitor C1. The non-inverting input terminal of the comparator 411 is connected to the ground GND through the third resistor R3, and the inverting input terminal of the comparator 411 is connected to the ground GND through the fourth resistor R4. The ground terminal of the comparator 411 is connected to the ground GND, and the power supply terminal of the comparator 411 is connected to the DC voltage source DC1, and this DC voltage source DC1 can be, for example, a 5V voltage source. The output terminal of the comparator 411 is used as the output terminal of the zero-crossing detection circuit 410 and is connected to the zero-crossing detection terminal G of the main control unit 210.

[0073] Exemplarily, the resistance values of the first resistor R1 and the second resistor R2 are equal, and the resistance values of the third resistor R3 and the fourth resistor R4 are equal.

[0074] According to Figure 5 the zero-crossing detection circuit 410 shown, it can detect the mains AC220V through the first input terminal A1 and the second input terminal A2, and output a square wave signal consistent with the mains frequency. Each rising edge or falling edge of this square wave signal represents a zero-crossing point. The main control unit 210 can determine the voltage phase angle of the mains through the edges of the square wave signal output by the zero-crossing detection circuit 410 and can trigger an external interrupt according to the edges of this square wave signal. According to the relay delay action duration of the first relay circuit and the AC power frequency period, determine the moment to send a closing control instruction to the first relay circuit, so as to realize the first relay circuit conducting or turning off at the zero-crossing point, or conducting or turning off at a specific voltage phase angle.

[0075] It can be understood that the square wave signal output by the zero-crossing detection circuit 410 includes a rising edge and a falling edge. The main control unit 210 can determine whether the zero-crossing point of the mains is a positive zero-crossing or a negative zero-crossing according to the rising edge or the falling edge. That is, the rising edge corresponds to a positive zero-crossing, and the falling edge corresponds to a negative zero-crossing.

[0076] Based on Figure 2 the corresponding embodiment of the inrush current suppression circuit, in an exemplary embodiment, Figure 6 an exemplary structural schematic diagram of the first relay circuit is shown. Refer to Figure 6As shown, the first relay circuit 220 may include a first relay 61, a first switching transistor Q1, and a first diode D1. Among them, the contact switch K1 of the first relay 61 is connected in series with the PTC thermistor RT, and the first coil L1 of the first relay 61 is connected between the DC voltage source DC2 and the first end c1 of the first switching transistor Q1; the cathode of the first diode D1 is connected to the DC voltage source DC2, and the anode of the first diode D1 is connected to the first end c1 of the first switching transistor Q1; the second end b1 of the first switching transistor Q1 serves as a first controlled end and is connected to the first control end CL1 of the main control unit 210, and the third end e1 of the first switching transistor Q1 is grounded; the first switching transistor Q1 conducts when receiving the closing control instruction sent by the first control end CL1 to control the conduction of the first relay 61 circuit. Among them, the voltage of the DC voltage source DC2 is, for example, 12V.

[0077] Exemplarily, the first switching transistor Q1 may be a triode. Correspondingly, the first end c1 may be the collector of the triode, the second end b1 may be the base of the triode, and the third end e1 may be the emitter of the triode. The triode Q1 may conduct when the first control end CL1 is at a high level and turn off when the first control end CL1 is at a low level.

[0078] Exemplarily, the first relay circuit 220 may further include a first filter circuit 62, and the first filter circuit 62 is connected in parallel with the first relay 61.

[0079] Specifically, the first filter circuit 62 is connected in parallel with the contact switch K1 of the first relay 61.

[0080] Exemplarily, the first filter circuit 62 may be an RC filter circuit. Specifically, the first filter circuit 62 may include a first filter resistor R5 and a first filter capacitor C2, and the first filter resistor R5 and the first filter capacitor C2 are connected in series and then connected in parallel with the contact switch K1 of the first relay 61.

[0081] Exemplarily, the time constant of the first filter resistor R5 and the first filter capacitor C2 is much smaller than 0.1 times the mains cycle.

[0082] In this way, by connecting the first filter circuit 62 in parallel with the first relay 61, the switching spike voltage generated by the contact switch K1 in the first relay 61 can be effectively absorbed, avoiding interference to the circuit caused by the switching spike voltage.

[0083] Based on Figure 2 the exciting inrush current suppression circuit of the corresponding embodiment, in an exemplary embodiment, Figure 7 Exemplarily shows the third structural schematic diagram of the exciting inrush current suppression circuit provided by the embodiment of the present invention. Refer to Figure 7As shown, the inrush current suppression circuit further includes a second relay circuit 710 connected in parallel with the PTC thermistor RT. Among them, the second control terminal CL2 of the main control unit 210 is connected to the second controlled terminal of the second relay circuit 710, and the main control unit 210 is further configured to control the second relay circuit 710 to conduct in the case of determining that the AC adapter reaches the magnetic balance state, so as to short-circuit the PTC thermistor RT.

[0084] In this way, by short-circuiting the PTC thermistor in the case of the AC adapter reaching the magnetic balance state, the system loss caused by the PTC thermistor connected in series in the circuit can be avoided.

[0085] Exemplarily, the main control unit 210 can monitor the voltage across the PTC thermistor or the current passing through the PTC thermistor. When it is monitored that the voltage across the PTC thermistor or the current passing through the PTC thermistor reaches a stable state, that is, remains at a constant value, it can be determined that the AC adapter reaches the magnetic balance state.

[0086] Alternatively, according to the characteristics of the AC adapter, the magnetic flux of the AC adapter usually reaches the balance state after 3 to 5 mains cycles. Based on this, it can be considered that the AC adapter reaches the magnetic balance state after the inrush current lasts for 3 to 5 mains cycles. Exemplarily, the duration of the inrush current can be monitored by detecting the zero-crossing points of the mains. For example, taking 3 cycles as an example, 6 zero-crossing points can be detected after the first relay circuit 220 conducts. When the 6th zero-crossing point is reached, it is determined that the AC adapter reaches the magnetic balance state.

[0087] Exemplarily, the structure of the second relay circuit 710 can be the same as that of the first relay circuit 220. For example, the second relay circuit can include a second relay and a second filter circuit, and the second filter circuit is connected in parallel with the second relay.

[0088] Exemplarily, the second filter circuit can include an RC filter circuit.

[0089] Based on Figure 7 For the inrush current suppression circuit corresponding to the embodiment, in an exemplary embodiment, the main control unit 210 is further configured to control the second relay circuit 710 to disconnect when the mains reaches the target voltage phase angle in the case of receiving the second instruction to disconnect the AC adapter, and after controlling the second relay circuit 710 to disconnect, in the case of determining that the AC adapter reaches the magnetic balance state, control the first relay circuit 220 to disconnect.

[0090] Specifically, after the main control unit 210 controls the second relay circuit 710 to disconnect, the PTC thermistor RT is reconnected to the circuit. The connection of the PTC thermistor RT will gradually reduce the current and voltage output by the power supply interface P, minimizing the residual magnetism of the transformer T of the AC adapter. After that, when the AC adapter reaches the magnetic balance state, disconnecting the first relay circuit 220 can reduce the influence of the residual magnetism.

[0091] Exemplarily, when the main control unit 210 receives the first instruction to turn on the AC adapter, if it controls the first relay circuit 220 to conduct when the mains power reaches the 90° voltage phase angle, then when it receives the second instruction to turn off the AC adapter, it can control the second relay circuit 710 to disconnect when the mains power reaches the 90° voltage phase angle. When the main control unit 210 receives the first instruction to turn on the AC adapter, if it controls the first relay circuit 220 to conduct when the mains power reaches the 270° voltage phase angle, then when it receives the second instruction to turn off the AC adapter, it can control the second relay circuit 710 to disconnect when the mains power reaches the 270° voltage phase angle.

[0092] Exemplarily, the main control unit 210 can determine the delay duration for sending the disconnection control instruction to the second relay circuit 710 based on the relay delay action duration of the second relay circuit 710 and the cycle of the mains power; starting from the first zero-crossing point of the mains power after receiving the second instruction, when the timing duration is equal to this delay duration, send the disconnection control instruction to the second relay circuit 710 to ensure that the second relay circuit 710 disconnects when the mains power reaches the target voltage phase angle. Among them, the principle of determining the delay duration for sending the disconnection control instruction to the second relay circuit 710 can refer to the principle of determining the delay duration for sending the closing control instruction to the first relay circuit 220, which will not be elaborated here.

[0093] Based on Figure 7 For the inrush current suppression circuit of the corresponding embodiment, considering that the inrush current is the largest when the voltage phase angle of the mains power is 0° or 180°, and the smallest when it is 90° or 270°, in an exemplary embodiment of the present invention, the main control unit 210 can specifically be used to control the first relay circuit 220 to disconnect when the mains power reaches the zero-crossing point when it is determined that the AC adapter reaches the magnetic balance state. In this way, the interference caused by the sudden change of the AC adapter current can be reduced.

[0094] Exemplarily, the zero-crossing point of the mains voltage can be detected by the zero-crossing detection circuit 410 as described above.

[0095] Based on the inrush current suppression circuits of the above embodiments, Figure 8 Exemplarily shows the fourth structural schematic diagram of the inrush current suppression circuit provided by the embodiment of the present invention. Refer to Figure 8As shown, the inrush current suppression circuit includes a main control unit 210, a first relay circuit 220, a second relay circuit 710, a PTC thermistor RT, a zero-crossing detection circuit 410, a mains connection terminal S, and a power supply interface P. Among them, the second relay circuit 710 may include a second relay 81, a second switching tube Q2, and a second diode D2. Among them, the contact switch K2 of the second relay 81 is connected in parallel with the PTC thermistor RT, and the second coil L2 of the second relay 81 is connected between the DC voltage source DC2 and the first end c2 of the second switching tube Q2; the cathode of the second diode D2 is connected to the DC voltage source DC2, and the anode of the second diode D2 is connected to the first end c2 of the second switching tube Q2; the second end b2 of the second switching tube Q2 serves as the second controlled end of the second relay circuit 710 and is connected to the second control end CL2 of the main control unit 210, and the third end e2 of the second switching tube Q2 is grounded.

[0096] When the second switching tube Q2 receives the closing control instruction sent by the second control end CL2, it conducts to control the second relay 81 to close. After the second relay 81 closes, it will short-circuit the PTC thermistor RT. When the second switching tube Q2 receives the opening control instruction sent by the second control end CL2, it opens to control the second relay 81 to open. At this time, the PTC thermistor RT is connected to the circuit.

[0097] Exemplarily, the second switching tube Q2 may be a triode. Correspondingly, the first end c2 may be the collector of the triode, the second end b2 may be the base of the triode, and the third end e2 may be the emitter of the triode. The triode Q2 may conduct when the second control end CL2 is at a high level and open when the second control end CL2 is at a low level.

[0098] Exemplarily, the second relay circuit 710 may further include a second filter circuit 82, and the second filter circuit 82 is connected in parallel with the contact switch K2 of the second relay 81.

[0099] Exemplarily, the second filter circuit 82 may be an RC filter circuit. Specifically, the second filter circuit 82 may include a second filter resistor R6 and a second filter capacitor C3. The second filter resistor R6 and the second filter capacitor C3 are connected in series and then connected in parallel with the contact switch K2 of the second relay 81.

[0100] Exemplarily, the time constant of the second filter resistor R6 and the second filter capacitor C3 is less than 0.1 times the mains cycle.

[0101] In this way, by connecting the second filter circuit 82 in parallel with the second relay 81, the switching spike voltage generated by the contact switch K2 in the second relay 81 can be effectively absorbed, avoiding interference to the circuit caused by the switching spike voltage.

[0102] According toFigure 8 The excitation inrush current suppression circuit shown Figure 9 shows a schematic diagram of the relay closing control timing in the scenario of turning on the AC adapter. Refer to Figure 8 and Figure 9 , after the main control unit 210 receives the first instruction to turn on the AC adapter, it performs a closing operation, that is, controls the contact switch K1 of the first relay 61 to close when the voltage phase angle of the commercial power is 90° or 270° through the first control terminal CL1. After the contact switch K1 closes, the PTC thermistor RT is connected to the circuit, and the current of the commercial power will be limited by the PTC thermistor RT. Since the temperature of the PTC thermistor RT will increase with the increase of the current and the resistance value will also increase, the excitation inrush current can be effectively suppressed. After a period of time, the AC adapter reaches the magnetic balance state. At this time, the main control unit 210 controls the contact switch K1 of the first relay 61 to close through the second control terminal CL2. At this time, the PTC thermistor RT is short-circuited and no longer consumes current, which can avoid the system loss caused by the PTC thermistor RT continuing to be connected in series in the circuit.

[0103] In this process, when the main control unit 210 receives the first instruction to turn on the AC adapter, it can obtain the zero-crossing information of the commercial power from the zero-crossing detection circuit 410, and determine the delay time for sending the closing control instruction to the first relay 61 according to the relay delay action duration of the first relay 61 and the cycle of the commercial power. Then, starting from the first zero-crossing of the commercial power after receiving the first instruction, timing is started. When the timing duration is equal to the delay time for sending the closing control instruction to the first relay 61, a closing control instruction is sent to the first relay 61 through the first control terminal CL1 to control the contact switch K1 of the first relay 61 to conduct when the commercial power reaches the 90° or 270° phase angle.

[0104] The magnetic flux of the AC adapter usually reaches the balance state after 3 to 5 commercial power cycles. Based on this, taking 3 cycles as an example, refer to Figure 9 , the main control unit 210 can detect 6 zero-crossings through the zero-crossing detection circuit 410 after the contact switch K1 closes, and then control the contact switch K2 of the second relay 81 to close at the zero-crossing of the commercial power through the second control terminal CL2 after 6 zero-crossings.

[0105] Figure 10 shows a schematic diagram of the relay closing control timing in the scenario of turning off the AC adapter. Refer to Figure 8 and Figure 10, after the main control unit 210 receives the second instruction to disconnect the AC adapter, it performs the removal operation of the AC adapter, that is, controls the contact switch K2 of the second relay 81 to disconnect when the voltage phase angle of the mains electricity is 90° or 270° through the second control terminal CL2. After the contact switch K2 is disconnected, the PTC thermistor RT is reconnected to the circuit, and the connection of the PTC thermistor RT will gradually reduce the current and voltage output by the power supply interface P, minimizing the residual magnetism of the AC adapter T. After a period of time, the AC adapter reaches the magnetic balance state. At this time, the main control unit 210 controls the contact switch K1 of the first relay 61 to disconnect when the mains electricity reaches the zero-crossing point through the first control terminal CL1. In this way, the interference caused by the sudden change of the AC adapter current can be reduced.

[0106] During this process, when the main control unit 210 receives the first instruction to disconnect the AC adapter, it can obtain the zero-crossing information of the mains electricity from the zero-crossing detection circuit 410, and determine the delay time for sending the disconnection control instruction to the second relay 81 according to the relay delay action duration of the second relay 81 and the cycle of the mains electricity. Then, starting from the first zero-crossing point of the mains electricity after receiving the first instruction, it starts timing. When the timing duration is equal to the delay time for sending the disconnection control instruction to the second relay 81, it sends the disconnection control instruction to the second relay 81 through the second control terminal CL2 to control the contact switch K2 of the second relay 81 to disconnect when the mains electricity reaches the 90° or 270° phase angle.

[0107] The magnetic flux of the AC adapter usually reaches the balance state after 3 to 5 mains electricity cycles. Based on this, taking 3 cycles as an example, referring to Figure 10 , the main control unit 210 can detect 6 zero-crossing points through the zero-crossing detection circuit 410 after the contact switch K2 is disconnected, and then control the contact switch K1 of the first relay 61 to disconnect at the zero-crossing point of the mains electricity through the first control terminal CL1 after 6 zero-crossing points.

[0108] The inrush current suppression circuit provided by the embodiment of the present invention, on the one hand, can connect or disconnect the AC adapter when the inrush current is the smallest, and use the PTC thermistor to suppress the inrush current when the AC adapter is connected or disconnected, avoiding the problem that the inrush current of the AC adapter causes interference to the distribution box system and leads to the restart of the distribution box when the AC adapter is connected or disconnected. On the other hand, by connecting a filter circuit in parallel at both ends of the contact switch of the relay, the spike voltage during the closing and opening processes of the relay can be effectively reduced, avoiding the interference of the spike voltage to the circuit.

[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. An inrush current suppression circuit, characterized in that, it includes a main control unit, a PTC thermistor, a first relay circuit, a mains connection terminal and a power supply interface; the PTC thermistor and the first relay circuit are connected in series between the mains connection terminal and the power supply interface, the mains connection terminal is used to connect to the mains, and the power supply interface is used to connect to an AC adapter; the first control end of the main control unit is connected to the first controlled end of the first relay circuit; the main control unit is used to control the first relay circuit to conduct in the case of receiving a first instruction to turn on the AC adapter, so as to connect the PTC thermistor.

2. The inrush current suppression circuit according to claim 1, characterized in that, the main control unit is specifically used for: in the case of receiving the first instruction, determining the delay time for sending a closing control instruction to the first relay circuit based on the relay delay action time of the first relay circuit and the cycle of the mains; starting timing with the first zero-crossing of the mains after receiving the first instruction, and sending the closing control instruction to the first relay circuit when the timing duration is equal to the delay time, so as to control the first relay circuit to conduct when the mains reaches the target voltage phase angle; wherein, the target voltage phase angle is 90° or 270°.

3. The inrush current suppression circuit according to claim 2, characterized in that, when the main control unit determines the delay time for sending a closing control instruction to the first relay circuit based on the relay delay action time of the first relay circuit and the cycle of the mains, it is specifically used for: determining the remainder of the relay delay action time divided by the first time; in the case where the remainder is greater than the second time, determining the difference between the third time and the remainder as the delay time; in the case where the remainder is less than or equal to the second time, determining the difference between the second time and the remainder as the delay time; wherein, the first time is half a cycle of the mains, the second time is 0.25 cycle of the mains, and the third time is 0.75 cycle of the mains.

4. The inrush current suppression circuit according to claim 2, characterized in that, the inrush current suppression circuit further includes a zero-crossing detection circuit; the input end of the zero-crossing detection circuit is connected to the mains connection terminal, and the output end of the zero-crossing detection circuit is connected to the zero-crossing detection end of the main control unit; the zero-crossing detection circuit is used to detect the zero-crossing of the mains.

5. The inrush current suppression circuit according to claim 1, characterized in that, the first relay circuit includes a first relay, a first switching tube and a first diode; the contact switch of the first relay is connected in series with the PTC thermistor, and the first coil of the first relay is connected between the DC voltage source and the first end of the first switching tube; the cathode of the first diode is connected to the DC voltage source, and the anode of the first diode is connected to the first end of the first switching tube; The second terminal of the first switching tube serves as the first controlled terminal and is connected to the first control terminal of the main control unit, and the third terminal of the first switching tube is grounded; the first switching tube conducts when receiving the closing control instruction sent by the first control terminal to control the conduction of the first relay circuit.

6. The inrush current suppression circuit according to claim 5, wherein, the first relay circuit further includes a first filter circuit, and the first filter circuit is connected in parallel with the first relay.

7. The inrush current suppression circuit according to any one of claims 1 to 6, wherein, the inrush current suppression circuit further includes a second relay circuit connected in parallel with the PTC thermistor; the second control terminal of the main control unit is connected to the second controlled terminal of the second relay circuit; the main control unit is further configured to control the second relay circuit to conduct to short-circuit the PTC thermistor when it is determined that the AC adapter reaches the magnetic balance state.

8. The inrush current suppression circuit according to claim 7, wherein, the main control unit is further configured to control the second relay circuit to disconnect when the mains power reaches the target voltage phase angle when receiving the second instruction to disconnect the AC adapter, and after controlling the second relay circuit to disconnect, control the first relay circuit to disconnect when it is determined that the AC adapter reaches the magnetic balance state.

9. The inrush current suppression circuit according to claim 8, wherein, the main control unit is specifically configured to control the first relay circuit to disconnect when the mains power reaches the zero crossing point when it is determined that the AC adapter reaches the magnetic balance state.

10. The inrush current suppression circuit according to claim 7, wherein, the second relay circuit includes a second relay and a second filter circuit, and the second filter circuit is connected in parallel with the second relay.

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