A transient starting current suppression circuit, suppression method and application

Abstract

The invention discloses a transient starting current suppression circuit, suppression method and application, comprising a fixed resistor R1, a fixed resistor R2, a negative temperature coefficient NTC resistor R3, a fixed resistor R4, a capacitor C1 and an insulated gate field effect transistor Q1, which can reliably suppress a large transient current when power is on in a DC link of an inverter circuit having a large-capacity capacitor; solve the difficulty that when a single negative temperature coefficient NTC resistor is used, low impedance caused by frequent startup cannot achieve a current limiting effect, and solve the problem that the negative temperature coefficient NTC resistor cannot reach a target temperature as soon as possible, that is, the impedance cannot be reduced as soon as possible, which affects unnecessary power consumption of the equipment under normal working conditions; and at the same time alleviate the shortcomings of complex circuits, complex controls and high costs.

Description

Technical Field

[0001] The present invention relates to the field of electronic circuits, and in particular to a transient starting current suppression circuit, suppression method and application. Background Art

[0002] The DC link support capacitor has the typical characteristic of large capacity and is widely used in the DC link circuit of the converter type power electronic equipment with inverter circuit. It plays the role of smoothing the rectifier output voltage and keeping the voltage fluctuation on the DC bus within the allowable range, such as Figure 1 C1 capacitor. However, due to its large capacity, if there is no corresponding circuit design, it is inevitable that this type of capacitor will be similar to a short circuit in the power supply circuit from a microscopic perspective at the moment of power-on. The transient current value is determined by the voltage across the capacitor and its "internal resistance", and the impedance of the "internal resistance" is very small, which is equivalent to the equivalent series resistance R of the capacitor. ESR (ESR Equivalent Series Resistance) is closely related. Through investigation, the R ESR It is about 0.02Ω (tested at 100Hz, 1V), and the RESR of a certain type of 560uF capacitor is about 0.16Ω (tested at 100Hz, 1V). According to Ohm's law, if the working voltage is known, the transient starting current can be known. Therefore, in a large-capacity capacitor circuit without relevant suppression measures, during the power-on transient, the power electronic equipment will generate a short-term current that exceeds the rated working current by dozens or even hundreds of times due to the capacitor. After normal operation, due to the "DC isolation and AC passing" characteristics of the capacitor, the current in the DC circuit where the capacitor works is negligible, and will no longer cause current shock to the power supply end.

[0003] In order to suppress the high current problem generated by large-capacity capacitors in the DC power supply circuit during power supply transients, there are generally several conventional methods in the practical application of existing design theory and product development:

[0004] (1) Connect a resistor in series on the main line of the power rectifier output end, such as Figure 2 As shown, this resistor can be a fixed resistance power resistor, which reduces the current value during power-on transient and normal operating conditions. The disadvantage is that the load power is increased. To reduce the impact of fixed resistance on power, Figure 2R1 can also be a temperature coefficient resistor (positive temperature coefficient PTC resistor, negative temperature coefficient NTC resistor). As the temperature changes, the impedance of R1 will change accordingly. For example, when using NTC resistor, if it reaches a sufficient temperature, the resistance will drop to tens of milliohms, which will not cause a large power increase to the circuit under normal working conditions. The disadvantage is that if the machine is turned on frequently, the NTC resistor will always be in a high temperature state, and the impedance will be very small, which will not achieve the purpose of suppressing the transient starting current when powered on. If the NTC resistor does not reach a certain temperature state during normal operation, it will still have a certain large impedance, which will still cause unnecessary power increase.

[0005] (2) Use a control scheme to bypass the current limiting resistor when the equipment is working normally, such as Figure 3 As shown, R1 is a current limiting resistor connected in series in the main circuit on the load side. It is generally a fixed resistor with high power and high impedance. When the device is powered on, the large-capacity capacitor C1 is slowly charged through this resistor. After the charging reaches the required voltage, the control relay J1 or similar components are activated (closed) to bypass R1. This solution is widely used and is generally confirmed and implemented in the design stage. The disadvantages are high cost, low integration, and difficulty in implementation at the PCB board level; the control is also relatively complex and requires software control measures; it is not easy to use for production rectification with only minor changes.

[0006] (3) Connect an inductor in series on the main line of the power rectifier output end, such as Figure 4 As shown, the characteristic that current cannot change suddenly in the inductor is used to suppress the transient current. The disadvantage is that the inductor has a relatively large inductance, resulting in a large volume and heat generation problem, which is not easy to implement in specific production and manufacturing.

[0007] In order to achieve the purpose of suppressing transient starting current, on the basis of ensuring product reliability, reducing costs and facilitating implementation, in recent years, scholars and engineers have proposed a variety of solutions. Most of these solutions are based on hardware circuit optimization and use software and hardware detection and control. They are not cost-effective in low-cost product projects, especially the current suppression circuit is a renovation from scratch, which is difficult to implement.

[0008] Therefore, this patent application is specially proposed. Summary of the invention

[0009] In view of the shortcomings of the prior art, the present invention provides a transient starting current suppression circuit, suppression method and application to solve the problem of large transient starting current, aiming to propose a circuit scheme and implementation method with high reliability, simple structure, low cost and easy to "create from scratch".

[0010] To achieve the above object, the present invention provides the following technical solution: a transient starting current suppression circuit, further comprising a fixed resistor R1, a fixed resistor R2, a negative temperature coefficient NTC resistor R3, a fixed resistor R4, a DC support capacitor C1 and an insulated gate field effect transistor Q1;

[0011] The negative electrode of the DC support capacitor C1 is connected to the negative line of the power supply circuit, and a first branch and a second branch are set between the positive electrode of the DC support capacitor C1 and the positive electrode of the power supply circuit. The first branch includes a fixed resistor R1 and a fixed resistor R2. The positive electrode of the DC support capacitor C1 is connected in series with the fixed resistors R1 and R2 and then connected to the positive electrode of the power supply circuit;

[0012] The second branch includes an insulated gate field effect transistor Q1, a negative temperature coefficient NTC resistor R3 and a fixed resistor R4; the drain of the insulated gate field effect transistor Q1 is connected to the positive electrode of the DC support capacitor C1, the gate of the insulated gate field effect transistor Q1 is connected between the fixed resistor R1 and the fixed resistor R2, the source of the insulated gate field effect transistor Q1 is connected in series with the negative temperature coefficient NTC resistor R3 and connected to the positive line of the power supply circuit, and the fixed resistor R4 is connected between the drain and source of the insulated gate field effect transistor Q1.

[0013] Preferably, the fixed resistors R1, R2 and R4 are installed in the charging and discharging branches of the DC support capacitor C1, and are not installed in the load working main circuit.

[0014] Preferably, the resistance value of the fixed resistor R1 is a ohm, the resistance value of the fixed resistor R2 is b ohm, and the resistance value of the negative temperature coefficient NTC resistor R3 at room temperature is R 常温 The resistance value of the negative temperature coefficient NTC resistor R3 at the maximum current is d ohms, and the resistance value of the fixed resistor R4 is b ohms, wherein b>c>a>d.

[0015] Preferably, the resistance d of the negative temperature coefficient NTC resistor R3 and the equivalent series resistance R of the DC support capacitor C1 are ESR1 Similar or of the same order of magnitude.

[0016] Preferably, when the insulated gate field effect transistor Q1 is turned on, the resistance of the negative temperature coefficient NTC resistor R3 should be as small as possible, and the first-order RC low-pass filter component formed should be mainly based on the capacitance characteristics.

[0017] Preferably, the insulated gate field effect transistor Q1 is a p-channel MOS transistor.

[0018] A method for suppressing transient startup current, through the temperature-impedance characteristics of negative temperature coefficient NTC resistor R3, the gate voltage of insulated gate field effect transistor Q1 is less than the source voltage (U G <US ) When conducting, the performance parameter characteristics and the voltage division characteristics of the resistor are used for circuit control design; before the insulated gate field effect transistor Q1 conducts, U G = U×R2 / (R1 + R2), U S = U×R4 / (R3 + R4), R2 = R4, the resistance value of resistor R1 affects U G , and the resistance value of resistor R3 affects U s of the principle; when the negative temperature coefficient NTC resistor R3 is at room temperature, U G = U×R2 / (R1 + R2) = U×b / (a + b), U S = U×R4 / (R3 + R4) = U×b / (c + b), c > a, making U G > U S , the PMOS insulated gate field effect transistor Q1 does not conduct; when the NTC resistor R3 is at the impedance near the maximum current, U G remains unchanged, U S = U×b / (d + b), d < a, making U G < U S , and the insulated gate field effect transistor Q1 conducts.

[0019] Preferably, when the negative temperature coefficient NTC resistor R3 is powered on transiently at room temperature, the voltage value U G of the gate of the insulated gate field effect transistor Q1 is greater than the voltage value U S of the source of the insulated gate field effect transistor Q1, making the source and drain of Q1 not conduct. The fixed resistor R1 and the fixed resistor R2 are in series, and then in parallel with the series-connected negative temperature coefficient NTC resistor R3 and the fixed resistor R4, suppressing the transient power-on current of the DC support capacitor C1.

[0020] Preferably, at the impedance of the negative temperature coefficient NTC resistor R3 near the maximum operating current, the voltage value U G of the gate of the insulated gate field effect transistor Q1 is less than the voltage value U S of the source, making the source and drain of Q1 conduct, bypassing the fixed resistor R1, the fixed resistor R2, and the fixed resistor R4. The negative temperature coefficient NTC resistor R3, the insulated gate field effect transistor Q1, and the capacitor C1 are connected in series between the positive and negative lines of the power supply circuit, forming a first-order RC low-pass filter component, and the capacitor C1 is used as a DC support capacitor.

[0021] Preferably, the parameters of the first-order RC low-pass filter component composed of the negative temperature coefficient NTC resistor R3 and the capacitor C1 do not cause and are not responsible for the resonance of the working circuit.

[0022] Preferably, when not working or not frequently turned on, the resistance of the negative temperature coefficient NTC resistor R3 is greater than the resistance of the fixed resistor R1, ensuring that the insulated gate field effect transistor Q1 is not turned on; when working in a steady state, the resistance of the negative temperature coefficient NTC resistor R3 is less than the resistance of the fixed resistor R1, ensuring that the insulated gate field effect transistor Q1 is turned on.

[0023] Preferably, in order to make the negative temperature coefficient NTC resistor R3 reach the low impedance at the maximum operating current as soon as possible, it is installed close to the heat source. In order to make the negative temperature coefficient NTC resistor R3 increase the impedance as soon as possible, the external surface heat dissipation method is adopted.

[0024] Preferably, in order to make the negative temperature coefficient NTC resistor R3 heat up as quickly as possible before the insulated gate field effect transistor Q1 is turned on, a heat conductive material is installed between R3 and the heat source.

[0025] Preferably, in order to make the negative temperature coefficient NTC resistor R3 heat up as quickly as possible before the insulated gate field effect transistor Q1 is turned on, if the heat source of R3 is in the form of a resistor, the power selection margin multiple of this heating resistor is reduced to increase the heating rate of the heat source and enhance the heating effect.

[0026] Preferably, in order to solve the problem that the negative temperature coefficient NTC resistor R3 is less than the resistance of the fixed resistor R1 when the power is frequently turned on, in addition to adopting a heat dissipation design outside R3, the NTC resistor R3 can adopt a fast heat dissipation packaging method to ensure that when the circuit is powered off, combined with the heat dissipation design, the temperature is quickly reduced and the impedance is increased.

[0027] Preferably, the NTC resistor R3 is selected to have a design concept and purpose that its impedance is less than the impedance of the fixed resistor R1 under specific conditions. The specific conditions can be at least when the maximum current working condition is approaching and the heat source temperature reaches a certain value, the NTC resistor R3 is less than the impedance of the fixed resistor R1.

[0028] The invention discloses an application of a transient starting current suppression circuit, which is connected after the output circuit of a rectifier circuit.

[0029] Compared with the prior art, it has the following beneficial effects:

[0030] 1. Reliably suppress the transient high current phenomenon of power-on in the DC link of the inverter circuit with large-capacity capacitors; solve the difficulty of using only NTC resistors, where the low impedance caused by frequent startup cannot achieve the current limiting effect; and solve the problem that the NTC resistor cannot reach the target temperature as soon as possible, that is, it cannot reduce the impedance as soon as possible, affecting the unnecessary power consumption of the equipment under normal working conditions. At the same time, it alleviates the shortcomings of complex circuits, complex controls, and high costs.

[0031] 2. The present invention is a method of assembling an actual circuit by considering and utilizing heat source design. The existing heat source in the circuit or environment is used to place the negative temperature coefficient NTC resistor close to it, so as to quickly and as much as possible reduce the resistance value of the NTC resistor R3. The heat dissipation design and selection design of the negative temperature coefficient NTC resistor are also carried out to quickly cool down the circuit without electricity, so as to quickly and as much as possible increase the resistance value of the NTC resistor R3. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1-Figure 4 All of them are current stabilization circuit diagrams of conventional methods in the prior art;

[0033] Figure 5 It is an application principle diagram of the transient starting current suppression circuit of the present invention;

[0034] Figure 6 The circuit diagram of the transient starting current suppression after adding heat-conducting and heat-dissipating materials of the present invention; DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions 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 are within the scope of protection of the present invention.

[0036] Example

[0037] See also Figure 5-Figure 6 , the present invention provides the following technical solutions:

[0038] The dotted box represents the rectifier circuit, which generates a pulsating high-voltage DC with a "steamed bun wave" shape, with a pulsating period of f1 and a rated voltage of U1. This embodiment is closely followed by the output circuit of the rectifier circuit represented by the dotted box. Specifically, the supporting capacitor C1 is the supporting capacitor of this DC circuit, with a large capacity, and is welded on the PCB board. The capacitor Cn represents the EMI filter capacitor of the subsequent circuit, and the resistor Rn represents the load of the subsequent circuit. The equivalent series resistance of the supporting capacitor C1 under the frequency f1 condition is R ESR1 , much less than 1 ohm.

[0039] The present embodiment provides a transient starting current suppression circuit, comprising a fixed resistor R1, a fixed resistor R2, a negative temperature coefficient NTC resistor R3, a fixed resistor R4, a DC support capacitor C1 and an insulated gate field effect transistor Q1; the surface temperature of the fixed resistor R2 is greater than 70°C when working; when the temperature of the negative temperature coefficient NTC resistor R3 is about 70°C, the impedance size thereof is similar to that of working under the condition of maximum current.

[0040] Specifically, fixed resistor R1, fixed resistor R2, negative temperature coefficient NTC resistor R3, fixed resistor R4, DC support capacitor C1 and insulated gate field effect transistor Q1 are all soldered on the PCB board; resistor R2 is a typical heat source, and negative temperature coefficient NTC resistor R3 is placed close to resistor R2 during PCB layout, with thermal grease between the two. When resistor R2 is working, NTC resistor R3 can be quickly heated to 70°C. Heat dissipation material is designed on the outside of NTC resistor R3, and the surface temperature of NTC resistor R3 can be quickly reduced to below 70°C when the entire circuit is without power.

[0041] The negative electrode of the DC support capacitor C1 is connected to the negative line of the power supply circuit, and a first branch and a second branch are set between the positive electrode of the DC support capacitor C1 and the positive electrode of the power supply circuit. The first branch includes a fixed resistor R1 and a fixed resistor R2. The positive electrode of the DC support capacitor C1 is connected in series with the fixed resistor R1 and the fixed resistor R2 and then connected to the positive electrode of the power supply circuit;

[0042] The second branch includes an insulated gate field effect transistor Q1, a negative temperature coefficient NTC resistor R3 and a fixed resistor R4; the drain of the insulated gate field effect transistor Q1 is connected to the positive electrode of the DC support capacitor C1, the gate of the insulated gate field effect transistor Q1 is connected between the fixed resistor R1 and the fixed resistor R2, the source of the insulated gate field effect transistor Q1 is connected in series with the negative temperature coefficient NTC resistor R3 and connected to the positive line of the power supply circuit, and the fixed resistor R4 is connected between the drain and source of the insulated gate field effect transistor Q1.

[0043] The resistance value of the fixed resistor R1 is a ohm, the resistance value of the fixed resistor R2 is b ohm, and the resistance value of the negative temperature coefficient NTC resistor R3 at room temperature is R 常温 The resistance value of the negative temperature coefficient NTC resistor R3 at the maximum current is d ohms, and the resistance value of the fixed resistor R4 is b ohms, wherein b>c>a>d.

[0044] Specifically, although the fixed resistors R2 and R4 have equal resistance values, R2 is used as a heat source, and its power selection margin is the calculated power (P = I 2 R) is about twice as large as that of R, thus improving its heat generation capacity; R4 is not used as a heat source, and its power selection margin is the calculated power (P = I 2 R) by 4 to 5 times.

[0045] Specifically, the resistance value b of the fixed resistor R2 and the fixed resistor R4 is much larger than the equivalent series resistance R of the DC support capacitor C1. ESR1 , starting the main current limiting function.

[0046] Specifically, since the DC support capacitor C1 operates in a pulsating DC circuit, when the circuit is operating normally, the DC support capacitor C1 will not fully discharge to zero charge, but only smooth the pulsating voltage. The charge and discharge time constant τ of the negative temperature coefficient NTC resistor R3 and the DC support capacitor C1 is τ = k*(d + R ESR1 )*C, where k is the pulsating discharge coefficient, 0 < k < 1, which is determined by the discharge ratio characteristic of the pulsating DC circuit, and C is the capacitance of the capacitor C1. The corresponding frequency f2 of its derivative is f2 = 1 / τ, making f2 > f1. Ensure that the capacitor C1 is used as a DC circuit support capacitor when the rectifier circuit is operating.

[0047] The insulated gate field effect transistor Q1 is a p-channel MOS transistor.

[0048] Utilize the performance parameter characteristics of the conductor when the gate voltage of the PMOS insulated gate field effect transistor Q1 is less than the source voltage (U G <U S ), as well as the voltage division characteristic of the resistor. Before the PMOS insulated gate field effect transistor is turned on, U G = U×R2 / (R1 + R2), U S = U×R4 / (R3 + R4), R2 = R4, and utilize the principle that the resistance value of the resistor R1 affects U G , and the resistance value of the resistor R3 affects U s . When the negative temperature coefficient NTC resistor R3 is at normal temperature, U G = U×R2 / (R1 + R2) = U×b / (a + b), U S = U×R4 / (R3 + R4) = U×b / (c + b), c > a, making U G > U S , and the PMOS insulated gate field effect transistor Q1 is not turned on; when the NTC resistor R3 is at the impedance close to the maximum current, U G remains unchanged, U S = U×b / (d + b), d < a making U G < U S , and the PMOS insulated gate field effect transistor Q1 is turned on.

[0049] As another implementation manner, the negative temperature coefficient NTC resistor R3 can be composed of multiple or multiple groups of negative temperature coefficient NTC resistors connected in series and parallel, meeting the effect of the overall negative temperature coefficient NTC resistor R3. When a single body of any negative temperature coefficient NTC resistor component fails, it does not affect the overall function of the circuit.

[0050] As another implementation manner, the DC support capacitor C1 can be composed of multiple or multiple groups of capacitors connected in series and parallel, serving as an overall "capacitor C1", and the other capacitors in the parallel branches can also be designed with the functions of the above circuit.

[0051] Such as Figure 6 As shown, as another implementation, the negative temperature coefficient NTC resistor R3 is adjacent to the heating element fixed resistor R2, and a heat conductive material can be used in between. The above electronic components R1, R2, R3, R4, and Q1 are all installed in the capacitor charging and discharging branch, not in the load working main circuit.

[0052] A method for suppressing transient starting current uses the temperature-impedance characteristic of a negative temperature coefficient NTC resistor R3 as a control signal for the on and off states of an insulated gate field effect transistor Q1.

[0053] When the negative temperature coefficient NTC resistor R3 is powered on transiently at a low temperature, the voltage value U G Less than the source voltage U s , so that the source and drain of Q1 are not conducting, the fixed resistors R1 and R2 are connected in series, and then connected in parallel with the negative temperature coefficient NTC resistor R3 and the fixed resistor R4 in a series state, so as to suppress the transient power-on current of the DC support capacitor C1.

[0054] When the negative temperature coefficient NTC resistor R3 is working normally in a steady state at a high temperature, the voltage value U of the gate of the insulated gate field effect transistor Q1 is G Greater than the source voltage U s , making the source and drain of Q1 conductive, bypassing the fixed resistors R1, R2, and R4, and the negative temperature coefficient NTC resistor R3, the insulated gate field effect transistor Q1, and the capacitor C1 are connected in series between the positive and negative lines of the power supply circuit to form a first-order RC low-pass filter component, and the capacitor C1 is used as a DC support capacitor.

[0055] When not working or not frequently turned on, the resistance of the fixed resistor R1 is smaller than the resistance of the negative temperature coefficient NTC resistor R3, ensuring that the insulated gate field effect transistor Q1 is not turned on; when working in a steady state, the resistance of the fixed resistor R1 is larger than the resistance of the negative temperature coefficient NTC resistor R3, ensuring that the insulated gate field effect transistor Q1 is turned on.

[0056] In order to make the impedance of the negative temperature coefficient NTC resistor R3 greater than that of the fixed resistor R1 when there is no electricity, the selection of the NTC resistor should consider that when Q1 is turned on, the NTC resistor should work approximately at the maximum current state, and the temperature at the maximum current state is relatively high, which means that the heating temperature requirement for the heat source (fixed resistor R2) is relatively high, and this temperature should be much higher than the ambient temperature of the installation space when there is no electricity. In other words, from a design perspective, the selection of the negative temperature coefficient NTC resistor R3 is designed to meet specific conditions so that its impedance satisfies the impedance of the fixed resistor R1. This specific condition can be "NTC resistor working at maximum current", "the impedance of the NTC resistor when the heat source is transferring heat is equal to the impedance at maximum current" and other conditions.

[0057] As a selected implementation method, the negative temperature coefficient NTC resistor R3 can be a sheet packaging structure with a large surface area, which can effectively absorb the heat from the heat source through the heat absorbing material, and quickly reduce the impedance before Q1 is turned on. When the circuit is without power, the heat dissipation design can effectively reduce the temperature rise and quickly increase the impedance.

[0058] As another implementation method, the negative temperature coefficient NTC resistor R3 can be a SMD package structure with a smaller surface area, which can be installed closer to the heat source, and quickly reduce the impedance before Q1 is turned on. When the circuit is without power, the large-area heat dissipation design can effectively reduce the temperature rise and quickly increase the impedance.

[0059] Working principle:

[0060] (1) In the normal working condition, according to the principle of resistor voltage division, since the fixed resistors R2 and R4 have equal resistance values, the resistance value of the fixed resistor R1 is smaller than the resistance value of the negative temperature coefficient NTC resistor R3 at room temperature, so U G >U S , the source and drain of the insulated gate field effect transistor Q1 are not conducting, and the DC support capacitor C1 is slowly charged through the fixed resistors R1 and R2 in series, and then connected in parallel with the negative temperature coefficient NTC resistors R3 and R4 in series. The fixed resistors R1, R2, and R4 act as pre-charging resistors to suppress transient startup current;

[0061] The negative temperature coefficient NTC resistor R3 is affected by the temperature rise of the heat source (the heat source in this example is the fixed resistor R2), and its resistance value decreases rapidly. When the resistance value of the fixed resistor R1 is greater than that of the NTC resistor R3, according to the principle of resistor voltage division, U G S , the source (S pole) and drain (D pole) of the PMOS insulated gate field effect transistor Q1 are turned on, the fixed resistors R1, R2 and R4 are bypassed, and the negative temperature coefficient NTC resistor R3 and the DC support capacitor C1 are connected in series to form a first-order RC low-pass filter component R3C1, which plays a role in filtering the DC circuit.

[0062] Since the heat source (in this example, the heat source is the fixed resistor R2) is bypassed after normal operation, the heat source will not be cooled electrically. The temperature rise of the negative temperature coefficient NTC resistor R3 is mainly determined by the heat generated by the current passing through it, creating conditions for the negative temperature coefficient NTC resistor R3 to cool down quickly after the circuit is powered off.

[0063] ​(2) In order to make the negative temperature coefficient NTC resistor greater than the impedance of the fixed resistor R1 when the circuit is without power, the NTC resistor selection considers the design concept of low impedance only under specific conditions. Under the premise that the normal working heat source is bypassed for cooling, the negative temperature coefficient NTC resistor is also heat-dissipated to ensure that the NTC resistor quickly increases its impedance after power failure, making it greater than the resistance of the fixed resistor R1. This solves the problem that frequent power-on easily produces unexpected insulated gate field effect transistor conduction and fails to achieve current limiting effect.

[0064] The invention discloses an application of a transient starting current suppression circuit, which is connected after the output circuit of a rectifier circuit.

[0065] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A transient starting current suppression circuit, characterized in that: It includes a fixed resistor R1, a fixed resistor R2, a negative temperature coefficient NTC resistor R3, a fixed resistor R4, a DC support capacitor C1 and an insulated gate field effect transistor Q1; The negative electrode of the DC support capacitor C1 is connected to the negative line of the power supply circuit, and a first branch and a second branch are set between the positive electrode of the DC support capacitor C1 and the positive electrode of the power supply circuit. The first branch includes a fixed resistor R1 and a fixed resistor R2. The positive electrode of the DC support capacitor C1 is connected in series with the fixed resistors R1 and R2 and then connected to the positive electrode of the power supply circuit; The second branch includes an insulated gate field effect transistor Q1, a negative temperature coefficient NTC resistor R3 and a fixed resistor R4; the drain of the insulated gate field effect transistor Q1 is connected to the positive electrode of the DC support capacitor C1, the gate of the insulated gate field effect transistor Q1 is connected between the fixed resistor R1 and the fixed resistor R2, the source of the insulated gate field effect transistor Q1 is connected in series with the negative temperature coefficient NTC resistor R3 and connected to the positive line of the power supply circuit, and the fixed resistor R4 is connected between the drain and source of the insulated gate field effect transistor Q1.

2. The suppression circuit according to claim 1, characterized in that The resistance value of the fixed resistor R1 is a ohm, the resistance value of the fixed resistor R2 is b ohm, and the resistance value of the negative temperature coefficient NTC resistor R3 at room temperature is R 常温 The resistance value of the negative temperature coefficient NTC resistor R3 at the maximum current is d ohms, and the resistance value of the fixed resistor R4 is b ohms, wherein b>c>a>d.

3. The suppression circuit according to claim 2, characterized in that The resistance d of the negative temperature coefficient NTC resistor R3 and the equivalent series resistance R of the DC support capacitor C1 ESR1 The same order of magnitude.

4. The suppression circuit according to claim 1, characterized in that The insulated gate field effect transistor Q1 is a p-channel MOS transistor.

5. A method for suppressing transient starting current, using the circuit as described in any one of claims 1 to 4, characterized in that: Based on the temperature-impedance characteristics of the negative temperature coefficient NTC resistor R3, the performance parameter characteristics of the insulated gate field effect transistor Q1 that conducts when the gate voltage is less than the source voltage (U G <U S ), and the voltage division characteristics of the resistors, circuit control design is carried out; before the insulated gate field effect transistor Q1 conducts, U G =U×R2 / (R1 + R2), U S =U×R4 / (R3 + R4), R2 = R4, the resistance value of resistor R1 affects U G , and the resistance value of resistor R3 affects U s ; when the negative temperature coefficient NTC resistor R3 is at room temperature, U G =U×R2 / (R1 + R2)=U×b / (a + b), U S =U×R4 / (R3 + R4)=U×b / (c + b), c > a, making U G >U S , and the PMOS insulated gate field effect transistor Q1 does not conduct; when the NTC resistor R3 is at the impedance near the maximum current, U G remains unchanged, U S =U×b / (d + b), d < a, making U G <U S , and the PMOS insulated gate field effect transistor Q1 conducts.

6. The method of claim 5, wherein: When the negative temperature coefficient NTC resistor R3 is powered on transiently at room temperature, the voltage value U on the gate of the insulated gate field effect transistor Q1 is G Greater than the voltage U at the source of the insulated gate field effect transistor Q1 S , so that the source and drain of Q1 are not conducting, the fixed resistors R1 and R2 are connected in series, and then connected in parallel with the negative temperature coefficient NTC resistor R3 and the fixed resistor R4 in a series state, so as to suppress the transient power-on current of the DC support capacitor C1.

7. The method of claim 6, wherein: The impedance of the negative temperature coefficient NTC resistor R3 when it is close to the maximum operating current makes the voltage value U G Less than the voltage U at the source of the insulated gate field effect transistor Q1 S , making the source and drain of Q1 conductive, bypassing the fixed resistors R1, R2, and R4, and the negative temperature coefficient NTC resistor R3, the insulated gate field effect transistor Q1, and the capacitor C1 are connected in series between the positive and negative lines of the power supply circuit to form a first-order RC low-pass filter component. At the same time, the capacitor C1 is used as a DC support capacitor.

8. The method of claim 6, wherein: When not working or not frequently turned on, the resistance of the negative temperature coefficient NTC resistor R3 is greater than the resistance of the fixed resistor R1, ensuring that the insulated gate field effect transistor Q1 is not turned on; when working in a steady state, the resistance of the negative temperature coefficient NTC resistor R3 is less than the resistance of the fixed resistor R1, ensuring that the insulated gate field effect transistor Q1 is turned on.

9. An application of the transient starting current suppression circuit as claimed in claim 1, characterized in that: Connect after the output circuit of the rectifier circuit.

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