High-power dual-coupling detection amplitude limiting circuit

Abstract

The invention relates to a high-power dual-coupling detection amplitude limiting circuit, which belongs to the field of microwave amplitude limiters and comprises a pre-stage amplitude limiting circuit, an auxiliary detection network and a post-stage amplitude limiting circuit which are sequentially connected along a main signal path, and the auxiliary detection network is used for reducing the power input to the post-stage amplitude limiting circuit by coupling input power before the detector tube D1 of the pre-stage amplitude limiting circuit is not fully conducted, and assisting the conduction of the PIN tube in the pre-stage amplitude limiting circuit. According to the high-power dual-coupling detection amplitude limiting circuit, the auxiliary detection network is added on the basis of a traditional semi-active circuit structure, and excessive radio-frequency power leaked into the rear-stage amplitude limiting circuit is coupled out from a main signal path through the auxiliary detection network before a detector tube of the front-stage amplitude limiting circuit is not fully conducted; therefore, the input power of the PIN tube in the post-stage amplitude limiting circuit is reduced, and the PIN tube is not burnt down; and meanwhile, the part of power can be used for assisting the conduction of a PIN tube in preceding stage amplitude limiting.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of microwave limiters, and particularly relates to a large-power double-coupling detection limiting circuit. BACKGROUND

[0002] A microwave limiter is an important front-end protection device in the field of radio frequency, and is used for protecting sensitive radio frequency key components such as low-noise amplifiers. The core function thereof is to automatically attenuate an excessively large radio frequency power injection, and when a small power is injected, the limiter keeps a low insertion loss to enable the signal to pass normally. In the design of the limiting circuit, the design of the front-stage coupler is crucial, and an insufficient design or excessively large coupling degree of the front-stage coupler is easy to burn the limiter die, thereby damaging the entire limiting circuit.

[0003] The existing large-power limiting technology mainly adopts a semi-active PIN limiting form of coupling detection, and the coupling detection network mainly provides direct current for the first-stage PIN. The first-stage coupler plays a key role, and if the coupling degree is excessively large, the detection tube is slow to open or even cannot be opened, so that the first-stage PIN tube cannot be fully turned on, and thus more power falls on the second-stage PIN diode, which leads to the second-stage PIN being easily burned. If the coupling degree is small, although the energy coupled to the detection tube is large enough to enable the detection tube to be opened and detected, the small coupling degree will make the size of the coupler excessively large.

[0004] Therefore, in order to solve the problem that the second-stage limiting tube is easily burned and reduce the size of the circuit, the structure of the coupling detection circuit needs to be redesigned. SUMMARY

[0005] In order to solve the above problems in the prior art, the application provides a large-power double-coupling detection limiting circuit. The technical problem to be solved by the application is solved by the following technical scheme. The application provides a large-power double-coupling detection limiting circuit, which comprises a front-stage limiting circuit, an auxiliary detection network and a rear-stage limiting circuit connected in sequence along a main signal path. The auxiliary detection network is used for coupling input power to reduce the power input to the rear-stage limiting circuit and assist the PIN tube in the front-stage limiting circuit to be turned on before the detection tube D1 in the front-stage limiting circuit is not fully turned on.

[0006] In an embodiment of the application, a capacitor C1 is arranged in front of the front-stage limiting circuit, and the capacitor C1 is used for inputting direct-current isolation and connecting a radio frequency signal input end.

[0007] In one embodiment of the present application, the pre-stage limiting circuit comprises a pre-stage detection network and a first PIN tube group, the pre-stage detection network is connected with the capacitor C1 and the first PIN tube group respectively; the first PIN tube group comprises PIN tubes P1, P2 and P3 connected in parallel, wherein the anodes of the PIN tubes P1, P2 and P3 are connected to the main signal path, and the cathodes are grounded.

[0008] In one embodiment of the present application, the pre-stage detection network comprises a coupler A1, a detection tube D1, a capacitor C2, a feed inductance L1 and an RC integration circuit, wherein the through end of the coupler A1 is connected in series between the capacitor C1 and the first PIN tube group; the coupling end of the coupler A1 is connected to the anode of the detection tube D1, the cathode of the detection tube D1 is connected to the main signal path through the feed inductance L1; the isolation end of the coupler A1 is connected to the first plate of the capacitor C2, and the second plate is grounded.

[0009] In one embodiment of the present application, the cathode of the detection tube D1 is connected to an RC integration circuit, the RC integration circuit comprises resistors R1 and capacitors C3 connected in parallel, wherein the first ends of the resistors R1 and the capacitors C3 are connected to the cathode of the detection tube D1, and the second ends are grounded.

[0010] In one embodiment of the present application, the auxiliary detection network comprises a coupler A2, a detection tube D2, an inter-stage blocking capacitor C4, a capacitor C6 and a feed inductance L2, wherein the through end of the coupler A2 is connected in series between the second end of the inter-stage blocking capacitor C4 and the post-stage limiting circuit; the coupling end of the coupler A2 is connected in parallel with the detection tube D2, the cathode of the detection tube D2 is connected to the coupling end of the coupler A2, the anode of the detection tube D2 is grounded, and the coupling end of the coupler A2 is connected to the main signal path through the feed inductance L2; the isolation end of the coupler A2 is connected to the capacitor C6, and the second end of the capacitor C6 is grounded.

[0011] In one embodiment of the present application, the post-stage limiting circuit comprises PIN tubes P4 and P5 connected in parallel, and a choke inductance L3, wherein the anodes of the PIN tubes P4 and P5 are connected to the main signal path, and the cathodes are grounded; the first end of the choke inductance L3 is connected to the main signal path, and the second end is grounded.

[0012] In one embodiment of the present application, the post-stage limiting circuit is provided with a capacitor C5, and the capacitor C5 is used for outputting a direct-current blocking and radio frequency signal output end.

[0013] In one embodiment of the present application, the capacitance of the capacitor C2 and the capacitor C6 is greater than or equal to 100 pF.

[0014] In one embodiment of the present application, when the input power exceeds the threshold value, the auxiliary detection network couples the input power to the detector tube D2, the detector tube D2 detects the direct current detection signal, and the direct current detection signal assists the PIN tube P1 to turn on through the feed inductance L2.

[0015] Compared with the prior art, the present application has the following beneficial effects: The high-power double-coupling detection limiting amplifier circuit of the present application adds an auxiliary detection network to the traditional semi-active circuit structure, and couples the excessive radio frequency power leaking into the subsequent stage limiting amplifier circuit from the main signal path before the detector tube of the previous stage limiting amplifier circuit is fully turned on, so as to reduce the input power of the PIN tube in the subsequent stage limiting amplifier circuit and prevent it from being burned out. Meanwhile, this part of power can be used to assist the PIN tube in the previous stage limiting amplifier to turn on.

[0016] In the present application, the isolation end of the coupler in the previous stage limiting amplifier circuit and the auxiliary detection network is connected to a large-capacitance capacitor. Compared with the scheme of connecting a resistor to the isolation end, the same coupler size can provide smaller coupling degree, so that more power can be coupled to make the detector tube turn on, and the size of the coupler and the volume of the circuit are reduced.

[0017] The above description is only a summary of the technical solutions of the present application. In order to more clearly understand the technical means of the present application, the content of the specification can be implemented, and in order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the following preferred embodiments are described in detail below, and the accompanying drawings are described as follows. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a schematic diagram of a high-power double-coupling detection limiting amplifier circuit provided by an embodiment of the present application; Figure 2a is a schematic diagram of a capacitor connected to the isolation end of the coupler A1 provided by an embodiment of the present application; Figure 2b is a coupling degree schematic diagram when the isolation end of the coupler A1 is connected to a capacitor and a resistor respectively provided by an embodiment of the present application; Figure 3a is a schematic diagram of the detector tube D2 connected in parallel to the coupling branch provided by an embodiment of the present application; Figure 3b is a detection current schematic diagram of the detector tube D2 connected in parallel or in series to the coupling branch provided by an embodiment of the present application; Figure 4Schematic diagram of output power when the auxiliary detection network provided by the embodiment of the present invention is adopted and not adopted. DETAILED DESCRIPTION

[0019] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, a high-power dual-coupled detection and limiting circuit proposed in accordance with the present invention is described in detail below with reference to the accompanying drawings and specific implementation methods.

[0020] The aforementioned and other technical contents, features, and effects of the present invention are clearly presented in the following detailed description of the specific embodiments in conjunction with the accompanying drawings. Through the description of the specific embodiments, a deeper and more specific understanding of the technical means and effects adopted by the present invention to achieve the intended purpose can be obtained. However, the accompanying drawings are provided for reference and illustration purposes only and are not intended to limit the technical solutions of the present invention.

[0021] Example 1 like Figure 1 As shown, Figure 1 The diagram is a schematic diagram of a high-power dual-coupled detection and limiting circuit provided by an embodiment of the present invention.

[0022] In this embodiment, a high-power dual-coupled detection and limiting circuit includes: a pre-stage limiting circuit, an auxiliary detection network, and a post-stage limiting circuit connected in sequence along a main signal path; the auxiliary detection network is used to reduce the power input to the post-stage limiting circuit by coupling input power before the detection tube D1 of the pre-stage limiting circuit is fully turned on, and to assist the PIN tube in the pre-stage limiting circuit in turning on.

[0023] In an optional embodiment, a capacitor C1 is provided before the pre-stage limiter circuit, and is used for input DC isolation and connected to the RF signal input terminal. A capacitor C5 is provided after the post-stage limiter circuit, and is used for output DC isolation and connected to the RF signal output terminal.

[0024] In this embodiment, the pre-stage limiting circuit includes a pre-stage detection network and a first-stage PIN transistor group. The pre-stage detection network is connected to capacitor C1 and the first-stage PIN transistor group, respectively. The first-stage PIN transistor group includes PIN transistors P1, P2, and P3 connected in parallel. The anodes of PIN transistors P1, P2, and P3 are all connected to the main signal path, and the cathodes are all grounded.

[0025] In an optional embodiment, the pre-detection network comprises: a coupler A1, a detection tube D1 (GaN SBD, gallium nitride Schottky diode), a capacitor C2, a feed inductance L1 and an RC integration circuit, wherein the through end of the coupler A1 is connected in series between the capacitor C1 and the first-stage PIN tube group; the coupling end of the coupler A1 is connected to the anode of the detection tube D1, the cathode of the detection tube D1 is connected to the main signal path through the feed inductance L1; and the isolation end of the coupler A1 is connected to the first plate of the capacitor C2, and the second plate of the capacitor C2 is grounded.

[0026] Further, the cathode of the detection tube D1 is connected to the RC integration circuit, and the RC integration circuit comprises: a resistor R1 and a capacitor C3 connected in parallel, wherein the first ends of the resistor R1 and the capacitor C3 are both connected to the cathode of the detection tube D1, and the second ends thereof are both grounded.

[0027] Preferably, the isolation end of the coupler A1 is connected to the large-capacitance capacitor C2, and the capacitance of the capacitor C2 is greater than or equal to 100 pF. By connecting the capacitor to the isolation end, a smaller coupling degree can be achieved in a smaller coupler size, so that more power is coupled to the detection tube D1, and the detection tube D1 is more likely to be turned on.

[0028] As shown in FIGS. 1, 2 and 3, Figure 2a and Figure 2b , the isolation end of the coupler A1 is connected to the capacitor C2. Figure 2a is a schematic diagram of the isolation end of the coupler A1 connected to the capacitor provided by the embodiment of the application; Figure 2b is a coupling degree diagram of the isolation end of the coupler A1 connected to the capacitor and the resistor respectively, wherein, Figure 2b indicates the change of the coupling degree with the frequency when the isolation end is connected to the capacitor and the resistor respectively.

[0029] Taking the parallel microstrip coupler as an example, in the same size, the S31 of the coupler whose isolation end is connected to the capacitor is larger than that of the coupler whose isolation end is connected to the resistor, so that more power is coupled to the detection network after the capacitor is connected. Therefore, by connecting the isolation end of the coupler in the pre-stage limiting circuit and the auxiliary detection network to the large-capacitance capacitor, compared with the scheme in which the isolation end is connected to the resistor, a smaller coupling degree can be provided in the same coupler size, so that more power can be coupled to make the detection tube conductive, and the size of the coupler and the volume of the circuit are reduced. It can be understood that the coupling degree is the absolute value of S31, and in the case of S31 being negative, the absolute value is taken, so that S31 becomes larger and the coupling degree becomes smaller.

[0030] The amplitude limiting principle of the pre-stage amplitude limiting circuit of the embodiment is as follows: the coupler A1 couples part of the input radio frequency power to the detector tube D1, so that the detector tube D1 is turned on to rectify the alternating current energy into direct current energy, and then the direct current energy acts on the PIN tubes P1, P2 and P3 through the feed inductor L1. After the PIN tubes are turned on, the impedance of the PIN tubes P1, P2 and P3 rapidly changes from high impedance to low impedance, which causes the circuit impedance to be mismatched, and most of the power is reflected back to achieve the effect of amplitude limiting. The RC integrating circuit composed of the resistor R1 and the capacitor C3 mainly filters the high frequency interference of the input signal, so that the output signal is smoother.

[0031] In the embodiment, the auxiliary detection network comprises the coupler A2, the detector tube D2, the inter-stage blocking capacitor C4, the capacitor C6 and the feed inductor L2. The through end of the coupler A2 is connected in series between the second end of the inter-stage blocking capacitor C4 and the post-stage amplitude limiting circuit. The coupling end of the coupler A2 is connected in parallel with the detector tube D2, the cathode of the detector tube D2 is connected to the coupling end of the coupler A2, the anode of the detector tube D2 is grounded, and the coupling end of the coupler A2 is connected to the main signal path through the feed inductor L2. The isolation end of the coupler A2 is connected to the capacitor C6, and the second end of the capacitor C6 is grounded.

[0032] Preferably, similar to the coupler A1, the isolation end of the coupler A2 is connected to the capacitor C6 with a large capacitance, and the capacitance of the capacitor C6 is greater than or equal to 100 pF.

[0033] The working principle of the auxiliary detection network of the embodiment is as follows: before the PIN tubes P1, P2 and P3 of the pre-stage amplitude limiting circuit are all turned on, the excessive radio frequency power leaking into the post-stage amplitude limiting circuit is coupled out of the main signal path, so as to reduce the input power of the PIN tubes in the post-stage amplitude limiting circuit and prevent the PIN tubes from being burned out. At the same time, the coupled-out power also causes the detector tube D2 to be turned on to detect a direct current signal. The direct current signal also acts on the PIN tube P1 of the pre-stage amplitude limiting circuit through the feed inductor L2 after passing through the post-stage amplitude limiting circuit, and the auxiliary PIN tube P1 is turned on. The inter-stage blocking capacitor C4 is used to block the direct current signal of the auxiliary detection network from flowing into the post-stage, so as to ensure that the feedback signal only acts on the PIN tubes of the pre-stage. In other words, it is ensured that the direct current signal detected by the detector tube D2 does not pass through the post-stage, but only acts on the PIN tube P1.

[0034] Since the input radio frequency power received by the auxiliary detection network is smaller than that of the pre-stage amplitude limiting circuit, the connection mode of the detector tube D2 in parallel with the coupling branch is different from that of the detector tube D1 in the pre-stage amplitude limiting circuit, and the detector tube D2 in parallel with the coupling branch can obtain a better detection effect. Figure 3a and Figure 3b As shown in Figure 3a is a schematic diagram of the detector tube D2 in parallel with the coupling branch provided by the embodiment of the present application; Figure 3bis a detection tube D2 provided by the embodiment of the present application and connected in parallel or series to a coupling branch, wherein, Figure 3b represents the change of the detection current with the input power when the detection tube is connected in parallel or series to the coupling end.

[0035] From the image of the change of the detection current with the input power, it can be seen that when the detection tube D2 is connected in parallel to the coupling branch, wherein the coupling branch is the circuit path extended from the coupling end of the coupler A2, the detection current is larger than the scheme that the detection tube D2 is connected in series to the coupling branch under the same input power, thereby a better detection effect can be obtained.

[0036] In the embodiment, the auxiliary detection network is connected to the post-stage limiting circuit, and the post-stage limiting circuit comprises a PIN tube P4, a choke inductance L3 and a PIN tube P5 connected in parallel, wherein the anodes of the PIN tube P4 and the PIN tube P5 are connected to the main signal path, and the cathodes are grounded; the first end of the choke inductance L3 is connected to the main signal path, and the second end is grounded. In the post-stage limiting circuit, the choke inductance L3 provides DC bias for the PIN tube P4 and the PIN tube P5 at the same time, thereby the PIN tube P4 and the PIN tube P5 are turned on, and the circuit size is effectively saved.

[0037] As shown in Figure 4 , the output power when the auxiliary detection network is used and not used is shown in Figure 4 , which represents the change of the output power with the input power when the auxiliary detection network is used and not used.

[0038] When the PIN tube of the pre-stage limiting circuit is successfully turned on, the output power decreases with the increase of the input power, and then increases with the increase of the input power. Under the action of the auxiliary detection network, the degree of the decrease of the output power is deeper than that without the auxiliary detection network, that is, the output power is lower. In other words, the auxiliary detection network can protect the PIN tube of the post-stage limiting circuit from being burned by the power leaked from the pre-stage limiting circuit, and at the same time, the power can be used to assist the turn-on of the PIN tube of the pre-stage limiting circuit, thereby the size of the coupler of the pre-stage limiting circuit can be reduced to a certain extent, and the circuit area is further reduced.

[0039] The working principle of the high-power double-coupling detection limiting amplifier circuit in the embodiment is that the front-stage limiting amplifier circuit is composed of a front-stage detection network and a first-stage PIN tube group in parallel, the anodes of the PIN tubes in the first-stage PIN tube group are connected to the main signal path, and the cathodes are grounded; wherein the front-stage detection network is mainly composed of a coupler A1, the through end of the coupler A1 is connected to the second end of a capacitor C1 and the anode of a PIN tube P1 respectively, the coupling end is connected to the anode of a detection tube D1 in series, the cathode of the detection tube D1 is connected to the detection tube D1 and a capacitor C3, and is connected to the main signal path through a feed inductance L1, and the isolation end is connected to a capacitor C2. The auxiliary detection network is mainly composed of a coupler A2, the through end of the coupler A2 is connected to the second end of an inter-stage separation capacitor C4 and the anode respectively, the coupling end is connected to the cathode of a detection tube D2, and is connected to the main signal path through a choke inductance L3, and the isolation end is connected to a capacitor C6. The rear-stage limiting amplifier circuit is composed of a PIN tube P4, a choke inductance L3 and a PIN tube P5 connected in parallel, the anode of the PIN tube P5 is connected to the first end C5 of the capacitor, and the second end of the capacitor C5 is connected to the RF signal output end for output.

[0040] When the input power exceeds the threshold value, and before the detection tube D1 is fully turned on, the auxiliary detection network reduces the input power of the rear-stage PIN tube through coupling, and at the same time, the input power is coupled to the detection tube D2 through the auxiliary detection network, and a DC detection signal is detected through the detection tube D2, so that the DC detection signal passes through the feed inductance L2 to assist the PIN tube P1 to be turned on.

[0041] It is worth noting that the present application opens up a new way of thinking for the design of the limiting amplifier circuit. In a multi-stage limiting amplifier circuit, the rear-stage limiting amplifier tube core is more likely to be burned out than the front-stage limiting amplifier tube core. Through the high-power double-coupling detection limiting amplifier circuit, the rear-stage limiting amplifier circuit can be protected during the operation of the limiter, and the circuit area is reduced while ensuring the safety of the rear-stage limiting amplifier circuit, which has great application value in the scene of miniaturization and high power.

[0042] The high-power double-coupling detection limiting amplifier circuit adds an auxiliary detection network to the traditional semi-active circuit structure, and couples the excessive RF power leaking into the rear-stage limiting amplifier circuit from the main signal path before the detection tube of the front-stage limiting amplifier circuit is fully turned on, so as to reduce the input power of the PIN tube in the rear-stage limiting amplifier circuit and prevent it from being burned out. At the same time, this part of power can also be used to assist the PIN tube in the front-stage limiting amplifier to be turned on.

[0043] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting; thus, unless specifically defined in this specification, all terms are to be given their broadest interpretation. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety for the teachings relevant to the sentence and / or paragraph in which the reference is presented.

[0044] The foregoing is considered as illustrative only of the principles of the application. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the application to the exact construction and operation described. Accordingly, all such variations are intended to be included within the scope of the present application as defined in the claims.

Claims

1. A high-power dual-coupled detection and limiting circuit, characterized in that: include: A front-stage limiting circuit, an auxiliary detection network and a rear-stage limiting circuit are sequentially connected along the main signal path; The auxiliary detection network is used to reduce the power input to the post-stage limiting circuit by coupling input power before the detection tube D1 of the pre-stage limiting circuit is fully turned on, and to assist the PIN tube in the pre-stage limiting circuit to turn on.

2. The high-power dual-coupled detection and limiting circuit according to claim 1, characterized in that: A capacitor C1 is provided before the pre-stage limiting circuit, and the capacitor C1 is used for input DC isolation and is connected to the radio frequency signal input terminal.

3. The high-power dual-coupled detection and limiting circuit according to claim 2, characterized in that: The pre-stage limiting circuit includes a pre-stage detection network and a first-stage PIN transistor group. The pre-stage detection network is respectively connected to the capacitor C1 and the first-stage PIN transistor group. The first-stage PIN transistor group includes a PIN transistor P1, a PIN transistor P2, and a PIN transistor P3 connected in parallel. The anodes of the PIN transistors P1, P2, and P3 are all connected to the main signal path, and the cathodes are all grounded.

4. The high-power dual-coupled detection and limiting circuit according to claim 3, characterized in that: The pre-stage detection network includes: a coupler A1, a detector tube D1, a capacitor C2, a feed inductor L1, and an RC integration circuit, wherein the through-end of the coupler A1 is connected in series between the capacitor C1 and the first-stage PIN tube group; the coupling end of the coupler A1 is connected to the anode of the detector tube D1, and the cathode of the detector tube D1 is connected to the main signal path through the feed inductor L1; the isolation end of the coupler A1 is connected to the first plate of the capacitor C2, and the second plate of the capacitor C2 is grounded.

5. The high-power dual-coupled detection and limiting circuit according to claim 4, characterized in that: The cathode of the detector tube D1 is connected to an RC integration circuit, which includes: a resistor R1 and a capacitor C3 connected in parallel, wherein the first ends of the resistor R1 and the capacitor C3 are both connected to the cathode of the detector tube D1, and the second ends are both grounded.

6. The high-power dual-coupled detection and limiting circuit according to claim 4, characterized in that: The auxiliary detection network includes: a coupler A2, a detection tube D2, a stage-to-stage DC capacitor C4, a capacitor C6, and a feed inductor L2, wherein the through end of the coupler A2 is connected in series between the second end of the stage-to-stage DC capacitor C4 and the post-stage limiting circuit; the coupling end of the coupler A2 is connected in parallel with the detection tube D2, the cathode of the detection tube D2 is connected to the coupling end of the coupler A2, the anode of the detection tube D2 is grounded, and the coupling end of the coupler A2 is connected to the main signal path through the feed inductor L2; the isolation end of the coupler A2 is connected to the capacitor C6, and the second end of the capacitor C6 is grounded.

7. The high-power dual-coupled detection and limiting circuit according to claim 1, characterized in that: The post-stage limiting circuit includes: a PIN transistor P4, a choke inductor L3 and a PIN transistor P5 connected in parallel, wherein the anodes of the PIN transistors P4 and P5 are both connected to the main signal path, and the cathodes are both grounded; the first end of the choke inductor L3 is connected to the main signal path, and the second end is grounded.

8. The high-power dual-coupled detection and limiting circuit according to claim 1, characterized in that: A capacitor C5 is provided after the post-stage amplitude limiting circuit, and the capacitor C5 is used for outputting DC isolation and is connected to the RF signal output terminal.

9. The high-power dual-coupled detection and limiting circuit according to claim 6, characterized in that: The capacitance of the capacitor C2 and the capacitor C6 are both greater than or equal to 100 pF.

10. The high-power dual-coupled detection and limiting circuit according to claim 6, characterized in that: When the input power exceeds the threshold, the auxiliary detection network couples the input power to the detection tube D2, and the detection tube D2 detects a DC detection signal. The DC detection signal passes through the feeding inductor L2 to assist the PIN tube P1 to turn on.

Images