RU2780661C1 - Class d amplifier for excitation of a low-frequency hydroacoustic transducer - Google Patents

Abstract

FIELD: hydroacuostics.

SUBSTANCE: invention relates to the field of amplifying and generator technology and can be used in hydroacoustic broadband amplifiers of low-frequency hydroacoustic communication (HC) and hydroacoustic echo ranging (HAR) modes. The result is achieved by matching the channel outputs of key power amplifiers (KPA) with two-channel PWM through low-pass filters with a hydroacoustic converter in the conditions of power supply of the terminal stages of the KPA with a high-voltage voltage generated by a high-frequency inverter, a high-frequency transformer and a rectifier device with a common-mode interference filter.

EFFECT: reduction in the volume and mass of transmitting equipment while expanding the frequency range of signals.

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Description

The invention relates to the field of amplifying and generator technology and can be used in hydroacoustic broadband power amplifiers for low-frequency hydroacoustic communication (HS) and sonar (HL) modes.

Low-frequency (LF) hydroacoustic transmission paths (HAPT) of the GS and GL modes are characterized by a high excitation power of hydroacoustic emitters (GAI), reaching units and tens of kVA [Aleksandrov V.A. and others. Transmitting paths of low-frequency sonar / Marine radio electronics N1 (67) 2019. P. 10-14]. The voltage of the LF GAI excitation signals, as a rule, reaches 700 V in the frequency range from hundreds of Hz to units of kHz. At the same time, the actual direction in the development of LF GS and GL is a further decrease in the frequencies of emitted signals and an increase in the power of excitation of the traffic police to increase the distance of detection and transmission of messages. As an effective direction for the implementation of low-frequency amplifiers (ULF) as part of the HAPT, one should single out key power amplifiers (KPA) with pulse-width modulation (PWM), defined according to the accepted classification as class D amplifiers [Artym A.D. Class D amplifiers and key generators in radio communications and broadcasting. M.: Communication. 1980. p. 207].

In such devices, the amplified signal is converted into a sequence of width-modulated pulses, amplified in power and fed to the load through a low-pass filter. In general, class D amplifiers contain a pulse-width converter (PWM), a key power amplifier (KPA) and a low-pass filter (LPF). When used as part of the GAPT, a key ULF of this type contains an output low-frequency transformer that provides galvanic isolation of the load and the corresponding level of the nominal excitation voltage of the low-frequency GAI.

To improve the quality of the excitation signals, hydroacoustic power amplifiers can use two-channel schemes for constructing class D amplifiers [RF Patent No. 2188498 Two-channel class D amplifier. Publ. 08/27/2002 BI No. 24]. Such an implementation provides a twofold increase in the resulting switching frequency, thereby expanding the dynamic and frequency range of the amplified signals. Known technical solution is the closest to the proposed one, and can be taken as a prototype of the present invention [RF Patent No. 2188498]. The prototype device (Fig. 1) contains a two-channel pulse-width converter SHIP 1, key power amplifiers KUM 2 and KUM 3, two low-pass filters LPF 4 and LPF 5, hydroacoustic emitter GAI 6 and two low-frequency transformers LF TP 7 and LF TP eight.

The power supply of KUM 2 and KUM 3 is carried out from the voltage E ₀ (+E ₀ , - E ₀ ), as a rule, galvanically connected to the object network. For example, for the object DC network, the power supply terminals of the KUM are directly connected to the mains voltage buses, and for the object AC network, the power supply voltage can be formed by a low-frequency power rectifier. The final stages of KUM 2 and KUM 3 are implemented on the basis of half-bridge transistor circuits adapted to the voltage E ₀ , equipped with pulse signal drivers with galvanic isolation. As a result of the amplification of the PWM signals at the outputs of the KUM, pulsed voltages V ₁ and V ₂ are formed, the total amplitude of which is determined by the voltage V _M =E ₀ . Accordingly, between the outputs of the low-frequency filter 4 and low-frequency filter 5, a low-frequency voltage U is allocated, the relative amplitude of which is determined by the modulation index t: m=U _m /E ₀ .

In this case, a voltage UH is formed on the load, the amplitude of which is set by the transmission coefficient of low-frequency transformers K _LF :

соответствующая требуемой максимальной мощности тонального сигнала возбуждения гидроакустического излучателя на заданной частоте Ω при импедансе нагрузки Z(Ω):In the rated output power mode at m=1, the maximum voltage amplitude is reached on the load

corresponding to the required maximum power of the hydroacoustic emitter excitation tone signal at a given frequency Ω with load impedance Z(Ω):

Thus, in the prototype device, low-frequency transformers 7 and 8 provide both galvanic isolation of the load and the required maximum output voltage to achieve the mode of maximum excitation power of the GAI.

At the same time, with a decrease in the frequency of the amplified signal, the mass, dimensions and energy losses in low-frequency transformers sharply increase. So, for example, at the lower frequency of the operating range F _n \u003d 1 kHz and a rated power of 1 kW, the dimensions of the low-frequency transformers exceed the total dimensions of the remaining ULF nodes with comparable energy losses.

With a further decrease in frequency to F _n \u003d 0.3 kHz, the volume and mass of ULF by more than 70-80% are determined only by the weight and size indicators of low-frequency transformers.

Along with the unacceptable deterioration in the weight and size parameters of the prototype device with a decrease in the lower frequency of the operating range, the use of low-frequency transformers is associated with a significant leakage inductance L _s , the value of which may exceed the minimum allowable inductance L _f LPF, determined from the condition of providing the upper frequency F _{in the} operating range.

It should be noted here that the load of traffic police, made on active piezomaterials, has a pronounced capacitive character with a capacitance value C _n corresponding to the active power factor of the load cosϕ(F _in ) no more than 0.1. Under these conditions, the low-pass filter cutoff frequency F _c for the required frequency response uniformity must be selected from the condition:

where L is the resulting filter inductance, reduced to the load.

Taking into account the components of the resulting inductance: L _f is the inductance of the filters LPF 4 and LPF 5; L _s - leakage inductance from the side of the primary windings LF TP 7 AND LF TP 8; taking into account the transformation ratio K _TNP we get:

The assessment shows that for LF TP with a lower frequency of 0.3 kHz, the presence of L _s limits the operating frequency band of the GAI excitation in the range of 2 octaves, which does not meet modern requirements for expanding the frequency range with a ratio of F _in / F _n more than 10.

The identified shortcomings significantly limit the use of the prototype device for the implementation of the transmitting equipment of small-sized broadband HAPTs that provide excitation of the LF GAI.

The objective of the present invention is to improve the weight, size and energy performance of power amplifiers while expanding the frequency range of the excitation signals of low-frequency hydroacoustic transducers.

To solve this problem, in a known class D amplifier for excitation of low-frequency hydroacoustic transducers, containing a two-channel pulse-width converter connected by an input to the input signal bus, and the first and second outputs of which are connected, respectively, to the inputs of the first and second key power amplifiers, the inputs whose power supplies are connected to the power supply buses, and the outputs are connected to the inputs of the first and second low-pass filters, it is proposed to introduce the following new features, namely: a high-frequency inverter, a high-frequency transformer and a rectifier device, the outputs of which are connected to the power supply buses through a common-mode noise filter, and the inputs through a high-frequency transformer and a high-frequency inverter are connected to the voltage buses of the object network, in turn, the outputs of the first and second low-pass filters are connected, respectively, to the first and second outputs of the low-frequency hydroacoustic radiation chatter.

The technical result from the use of a combination of new features makes it possible to reduce the volume and multiple reduction in the mass of the power amplifier while expanding the frequency range of signals due to the elimination of a bulky low-frequency transformer with significant leakage inductance under conditions of direct matching of the terminal stages of the CCM with the load on the traffic police at a power supply voltage of a given level, galvanically isolated from the object network.

The essence of the invention is illustrated in Fig. 1, fig. 2 and FIG. 3, which shows block diagrams of the prototype device (Fig. 1) and the proposed device (Fig. 2), as well as timing diagrams of signals (Fig. 3), explaining the features of the proposed technical solution.

In FIG. 3 adopted the following designations:

- in Fig 3a): U - voltage in the input signal bus, U _p1 , U _p2 - sawtooth antiphase voltages with a half-cycle T _to formed in PWM 1 to generate PWM signals PWM 1, PWM 2, PWM 1, PWM 2 - sequences pulses at the outputs of PWM 1, generated by comparing the input signal U, respectively, with sawtooth voltages U _p1 , U _p2 ;

- in Fig 3b): V _r - high-frequency pulsed voltage with a period of T ₀ generated in the RFID 9 by key conversion of the power supply voltage E ₀ object DC network;

- in Fig 3c): V _HF - the voltage of the secondary winding of the RF TP 10, the primary winding of which is supplied with a pulsed voltage V _r through additional filter elements as part of the RF 9;

- in Fig 3d, e): V1, V2 - pulse voltage at the outputs of KUM 2, KUM 3 with amplitude E, formed by key amplification in terms of power of PWM 1 and PWM 2 signals, ± E - output voltage generated at the output of VU 11 by means of rectification and voltage filtering V _HF ;

- in Fig 3f): V is the total pulse voltage coming from the outputs of the KUM 2 and KUM 3 to the inputs of the low-pass filter 4 and low-pass filter 5, V _n , U _n - respectively, the low-frequency component of the impulse voltage V and the low-frequency voltage at the load GAI 6.

The proposed class D amplifier for excitation of low-frequency hydroacoustic transducers (Fig. 2) contains a two-channel pulse-width converter SHIP 1, key power amplifiers KUM 2, KUM 3, low-pass filters LPF 4, LPF 5, hydroacoustic emitter GAI 6, high-frequency RF inverter 9 , high-frequency transformer VChTR 10, rectifier VU 11, common mode filter FSP 12.

The composition of the proposed device includes blocks made according to known rules in accordance with the declared implementation features, the combined use of which ensures the achievement of a technical result.

The pulse-width converter PWM 1 is performed in the same way as in the known device according to patent No. 2188498 in a two-channel scheme and may contain a paraphase generator of reference sawtooth voltages U _p1 , U _p2 and two comparators with output drivers that control the switching amplification circuits.

Accordingly, the key power amplifiers KUM 2 and KUM 3 are implemented in the same way as in the prototype device, according to half-bridge circuits on high-voltage transistors, the joint inclusion of which forms a bridge circuit of the key amplification. The choice of transistors must comply with the requirements of the specified voltage level E of the power supply, which determines the amplitude of the pulsed voltage V and, accordingly, the maximum amplitude of the low-frequency voltage U _n of excitation of the traffic police 6. Moreover, for low-frequency hydroacoustic emitters, the value of U _n must be at least 1000 V, at rated excitation power up to Рnm=10 kVA, which determines the required value of allowable voltages and currents of powerful transistors:

respectively, with safety factors for reliable operation K _U =1.2 and K _I =2.0.

The transistors of the terminal stages of the KUM must be designed for permissible parameters U _add ≥1.2 kV, I _add = 40A. At the same time, for use as part of powerful key ULF with PWM at switching frequencies of 50-100 kHz, high speed with a switching inertia of no more than 0.1-0.2 μs should be ensured with a very small internal accompaniment in the open state of not more than 0.1- 0.2 ohm.

Until now, the combination of these requirements has practically excluded the possibility of implementing high-voltage terminal stages of the CCM with acceptable parameters of energy efficiency and the quality of amplification of pulsed signals with PWM. With the advent of a new class of field-effect transistors, created using silicon carbide technology, the required combination of parameters becomes achievable. So CREE transistors, for example, type C2M0025120D, meet the requirements of U _add 1200 V I _add 60 A with a channel resistance of 0.025 Ohm and a maximum turn-off delay of not more than 0.15 μs.

Low-pass filters (LPF 4 and LPF 5) are designed to suppress the high-frequency components of the impulse voltage V and isolate the low-frequency component V _n at the load. In the simplest case, low-pass filter 4, low-pass filter 5 are performed on chokes, the total inductance L of which is determined from relation (3), taking into account the load capacitance C _n and the specified upper limit F _{in the} frequency range.

The high-frequency inverter VFI 9 is designed for highly efficient conversion of DC voltage E ₀ into high-frequency voltage V _r with a period of T ₀ for power transmission of power supply KUM 2 and KUM 3 through a high-frequency transformer (HF TP 10). As part of the RFI 9, an RF pulse shaper with a control driver and a final stage on powerful field-effect transistors are implemented, made on a half-bridge or bridge circuit. The output power of the final stage RFID 9 must correspond to the active component of the maximum load power Max|P _n |. Taking into account the active power factor of the traffic police 6 cosϕ=0.2-0.5, for maximum power P _n =10 kVA, the output power of the RFID 9 should reach 5 kW.

With a power supply voltage from the object DC network E ₀ ≅220 V, MOSFET transistors of the IPW60R017C7 type with a permissible power supply voltage of 600 V and a maximum current of up to 100 A, included in a half-bridge circuit, can be used to implement the final stage of the RFI 9. The high speed of such field-effect transistors makes it possible on their basis to implement a high-frequency inverter in the key mode with soft switching paths at a frequency of about 100 kHz with a relative energy loss of no more than 2%, which corresponds to the condition of high energy efficiency of the high-frequency voltage transformation path of the power supply of high-voltage CCM using RF TP 10 and VU 11.

The high-frequency transformer HF TP 10 must provide galvanic isolation and voltage matching E of the power supply of KUM 2 and KUM 3 from the voltage E ₀ of the facility network under the conditions of the required level of maximum excitation voltage GAI 6:

where K _tvch is the transformation ratio of the HF TR.

To implement RF TP, a high-frequency magnetic core, for example, ferrite type N87, can be used, which makes it possible at a frequency of 100 kHz to provide a specific transformer power of more than 2 kW/kg with a relative energy loss of less than 1%. The given parameters are fundamentally different from the LF TP indicators, which provide, for example, for a lower frequency of 300 Hz, a specific power of 0.2 kW/kg and a loss of more than 2%.

The rectifying device VU 11 must ensure the conversion of the RF voltage V _HF amplitude E into a constant voltage of a given level. Taking into account the high conversion frequency of 100 kHz and the high level of power supply E = 1000 V, it is advisable to implement the rectifier device in a bridge circuit on high-voltage pulsed diodes with a permissible voltage of more than 1200 V and a maximum current of 10 A. The relative energy losses in such a high-voltage VU, as a rule, do not exceed 0.5%.

A feature of the implementation of the proposed solution is the presence of a significant level of common-mode interference due to the galvanic binding of the outputs of the final stages of the KUM 2 and KUM 3 directly to the outputs of the GIA 6, which can cause high-frequency common-mode currents through parasitic capacitances of the elements of the key amplification circuit to the housing and then to the common voltage bus of the object networks. The suppression of this type of common-mode interference is ensured by using a symmetrical FSP 12, which includes input and output capacitors C1 and C2, as well as a symmetrical choke on a high-frequency magnetic circuit with back-to-back windings. The inductance of a separate winding is set to about 0.5-2.0 mH, which provides effective suppression of common mode noise with frequencies well above 100 kHz. The introduction of this type of FSP 12 into the composition of the proposed device is a necessary condition for ensuring the stable operation of the CCM without low-frequency transformer isolation from the load.

The proposed class D amplifier for excitation of a low-frequency hydroacoustic transducer operates as follows.

The voltage E ₀ of the power supply from the object network is converted by the RFID 9 into a high-frequency pulse voltage V _r (Fig. 3b), which, through the RF TP 10, is transformed into a voltage V _RF (Fig. 3c) of a given amplitude E ₀ . As a result, at the output of VU 11, a power supply voltage E of a given level is formed, which, through the FSP 12, is supplied to the power supply buses of the terminal stages of KUM 2 and KUM 3.

In turn, the input signal voltage U is fed to the input of SHIP 1, where, as a result of comparison with antiphase sawtooth voltages U _p1 , U _p2 , it provides the formation of PWM 1 and PWM 2 signals (Fig. 3a), which are fed to the control inputs of KUM 2 and KUM 3 As a result of the key power amplification of the PWM 1 and PWM 2 signals, voltages V1 and V2 are formed at the outputs of the PWM 2 and PWM 3 (Fig. 3d, e), which through the LPF 4 m LPF 5 enter the load of the traffic police 6.

At the same time, at the inputs of LPF 4 and LPF 5, the resulting pulse voltage V with amplitude E (Fig. 3f) is formed, the low-frequency component of which VH has an amplitude proportional to the modulation index m:

where U _pm is the amplitude of the reference sawtooth voltage.

Accordingly, at the outputs of LPF 4, LPF 5, connected to the load, a low-frequency voltage UH is allocated, the amplitude and phase of which practically (up to the transfer characteristics of the LPF) coincides with the parameters of the low-frequency component VH of the resulting impulse voltage. Under the conditions of fulfilling the recommendations for choosing the resulting filter inductance in accordance with expression (3), the LPF transfer coefficient in the operating frequency band is close to K _f =1 with a very small phase shift (no more than 5-10 deg). Therefore, the maximum voltage Max|U _n |, supplied to the traffic police 6 is determined by the expression (6).

Thus, in the claimed device, a transformerless matching of the output of the key ULF with a low-frequency GAI is achieved with the corresponding formation of a high-voltage power supply for the terminal stages of the KUM 2 and KUM 3 channels. bulky low-frequency transformers with a decrease in relative energy losses (from 15% to 10%) in the conditions of expanding the operating frequency band (from 2 octaves to 3-4 octaves).

It should be noted the complexity of the electromagnetic compatibility (EMC) of the proposed technical solution, which requires the use of additional technical means of common-mode filtering of the high-voltage galvanically isolated voltage of the power supply of the KUM. The solution of these issues is achieved by using a special common-mode noise filter FSP 12, the introduction of which practically eliminates the influence of pulsed RF noise on EMC conditions. At the same time, the dimensions and energy losses in FSP 12 are very small and practically do not affect the characteristics of the device as a whole.

The enterprise manufactured an experimental sample of the proposed class D amplifier for excitation of a low-frequency hydroacoustic transducer, the test results of which as part of the radiating path channel confirmed the achievement of the claimed effect with an output voltage amplitude at a load of up to 1 kV and a rated output power of 5 kVA. It is proposed to implement the present invention in a number of priority developments of the transmission paths of the modes of low-frequency hydroacoustic communication and sonar.

Claims (1)

A class D amplifier containing a two-channel pulse-width converter connected by its input to the input signal bus, and its first and second outputs are connected, respectively, to the inputs of the first and second key power amplifiers, the power supply inputs of which are connected to the power supply buses, and the outputs, respectively , with the inputs of the first and second low-pass filters, characterized in that it includes a high-frequency inverter, a high-frequency transformer and a rectifier, the outputs of which are connected to the power supply buses through a common-mode noise filter, and the inputs are connected to the buses through a high-frequency transformer and a high-frequency inverter object network voltage, while the outputs of the first and second low-pass filters are connected, respectively, to the first and second outputs of the low-frequency hydroacoustic radiator.

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