RU2398347C1 - Shaper of energy pulses with controlled shape - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: energy discharge is provided at high permissible voltages of high-frequency switch or high-voltage pillar on its basis. Such possibility is provided through installation of protective circuit with properties of voltage limiter in special mode of application, introduction of low frequency switch and quick-acting mode of pulse shaper current stabilisation. As maximum permissible voltage of capacitance energy accumulator grows, it becomes possible to increase energy of controlled pulses, range of pulse parametres control and/or reduce dimensions of capacitance energy accumulator. Possibility to increase working frequency of HF switch assists in accuracy of setting shape of controlled pulse. Excessively high voltage of energy accumulator charge results in fast conversion of excessive energy into thermal energy released in protective circuit. At the same time dynamic losses at each switching of HF-switch are reduced, as well as frequency of its switchovers at critical part of discharge. Energy of pulse may grow, collapse in one or several stages, change direction, oscillate relative to specified levels independently on change in load resistance. Generated distribution of energy in pulse may be pre-determined or adaptable to process load.

EFFECT: improved main parametres of pulse shaper with adjustable shape.

6 cl, 8 dwg, 5 ex

Description

FIELD OF THE INVENTION

It can be used in electric pulse shapers for electrical technologies for various purposes, using the discharge of a capacitive energy storage device. For example, in medical devices, in pulse generators for plasma and electrochemical technologies, in electrical installations, in measuring and testing equipment, in radiation generators, in an electric drive. The invention is useful when exposed to technological loads with a non-linear effect, when an exposure with an optimal energy distribution is more desirable.

State of the art

A high-voltage pulse modulator is known which forms a discharge of a capacitive energy storage device for a process load (RF Patent for utility model 69685 dated 12/27/2007, HIGH VOLTAGE PULSE MODULATOR). High-voltage transistors are connected to a high-voltage pole and shunt by pulse diode voltage limiters. A high-voltage pole of twelve cells (n = 12) with IRFPG50 transistors was tested at a voltage of 9000 V. Disadvantages of a pulse modulator: the shape of the generated pulse depends entirely on the voltage drop of the capacitive energy storage device and load parameters; a pulse modulator cannot operate at a supply voltage exceeding the breakdown voltage of pulse diode limiters.

Known generator ANP-3122, which is a source of arbitrary waveforms, set by the user using mathematical expressions, by template or graphically. The maximum range of the output voltage of the device is not more than ± 10 V at a load of 50 ohms. The device is registered in the State register of measuring instruments No. 27123-04. The disadvantage of this device is the lack of control over the generated signal and the low power of the arbitrary signal source.

A known bipolar pulse shaper, in which two keys in the shoulders of the bridge work at a high frequency, and two keys work at a low frequency (combined bridge circuit). A pulse shaper is known in which instead of a bridge two capacitive energy storage devices and two keys are used. Known pulse shaper using cells with a voltage divider on the capacitors of a capacitive energy storage.

EP 0813892 A2, 12.29.1997, DEFIBRILLATOR WITH WAVEFORM SELECTION CIRCUITRY.

US Patent No. 6,493,580 B1, 12/10/2002, IMPULSES OR A SERIES OF IMPULSES FOR DEFIBRILLATION AND DEVICE TO GENERATE THEM.

PCT / EP2003 / 012857, 11/17/2003, DEFIBRILLATOR WITH IMPROVED OUTPUT STAGE.

RF patent 2345475 dated 01/27/2009, DEVICE FOR FORMING BIPOLAR AND MULTI-PHASE SIGNALS.

The use of two or more isolated converters causes the complication and cost of the pulse shaper.

The description of a device synthesizing an output signal of short duration, which is generated by a number of short pulse generators, is known. The generated pulses are adjustable in amplitude, duration, width and polarity. US Patent 7,545,304 B1, 06/09/2009, DISTRIBUTED ARBITRARY WAVEFORM GENERATOR. The disadvantage is that a large number of keys with control loops are required.

A description is known of a high-power pulse shaper using several cells of step-down converters operating in the pulsed modulation mode with voltage separation across the capacitor bank of a capacitive energy storage device. Four keys of the LF switch are used to switch the polarity of the pulses and two keys to break the high voltage circuit (See FIG. 2, US Patent No. 6,546,287 B1, 04/08/2003, CONTROLLED-POWER DEFIBRILLATOR AND METHOD OF DEFIBRILLATION). The use of several successive converter cells is due to technological limitations imposed on the maximum permissible reverse voltage of mass-produced transistors, mainly up to 1200 V. Disadvantages - additional keys with control loops and increased dimensions of capacitive and inductive energy storage devices are required.

The closest in technical essence and the achieved positive effect and adopted as a prototype is a controlled-energy pulse shaper containing a down-converter (See Fig. 7, US Patent No. 7,200,434, 04/03/2007, CONTROL OF ARBITRARY WAVEFORMS FOR CONSTANT DELIVERED ENERGY). High-speed switching (up to 500 kHz) is used to generate controlled-mode pulses of up to 3 kW and voltage at a load of up to 1000 V. The shape of the pulses is controlled by a pulse modulator with a feedback loop on the voltage in the load. Use four fully controllable keys in the low-frequency switch to switch the current direction in the process load. The disadvantage is the low energy of the pulses.

The use of voltage separation of a capacitive energy storage device, the use of several converters in various schemes for their connection do not solve the problem of generating pulsed thermal switching losses in high-frequency switches and powerful overvoltages at their terminals.

Disclosure of invention

The invention is aimed at increasing the energy of the generated pulses, increasing accuracy and expanding the range of regulation of their parameters, reducing the size, increasing the reliability of the driver.

The technical result is achieved due to the fact that the converter of the pulse shaper contains one or more series-connected high-frequency keys, forming sections of a high-frequency column (high-frequency column) with constant reverse conductivity.

Management of the RF key (sections of the RF column) is provided from a galvanically isolated pulse modulator through isolators of logical signals through high-frequency drivers. The pulse modulator controls the switching of the RF key (sections of the RF column) at a high frequency and contains at least a current feedback loop in the process load circuit with the possibility of continuing the operation of the converter in a short circuit mode in the process load circuit.

A protective circuit with the properties of a voltage limiter is installed in parallel with the HF key or each section of the HF column so that the voltage on the HF key (sections of the HF column) is limited to a level that does not exceed the maximum voltage at which the HF key or sections The HF pillar retains its blocking ability.

At least one low-frequency switch (low-frequency switch) with a control circuit is installed in the circuit of the generated current pulse. The low-frequency key retains blocking properties at a voltage exceeding the maximum allowable charge voltage of a capacitive energy storage device.

The low-frequency key is turned on only for the duration of the current generation phase and at the same time the high-frequency switching of the high-frequency key (high-frequency column) begins. When you turn on the RF key (RF column), the current of its inclusion is limited by means of an inductive energy storage device. When it is turned off, as the discharge current decreases and the voltage on the HF key (sections of the HF column) increases, the mode of automatic switching of the switched-off current into the protective circuit is provided. The LF key is turned off and the uncontrolled current of the protective circuit is interrupted in the process load after the HF key (HF column) is stationary turned off and the pulse formation phase is completed.

The current is generated through a bridge polarity switch (bridge) with four low-frequency switches forming the shoulders of the bridge. A technological load is installed between the shoulders of the bridge.

The bridge is based on single-operation triode thyristors (OTTs). An additional low-frequency switch is installed in the action circuit of the generated current. Unregulated current is disconnected or sharply reduced by an additional low-frequency switch.

The pulse modulator is galvanically isolated, except for the connection area of its measuring circuits to the current sensor.

To generate pulses using: two or more converters with low-frequency keys; a combined bridge circuit containing at least one converter and low-frequency keys; converters with low-frequency switches when discharging separate and / or common capacitive energy storage devices, simultaneously or in different phases.

Description of drawings

Figure 1 shows a diagram of a pulse shaper of energy.

Figure 2 shows a diagram of a three-phase two-section column.

Figure 3 shows the pulses of the discharge current and the current of the reverse diode.

Figure 4 shows a diagram of an energy pulse shaper with a bridge.

Figure 5 shows a diagram with two shapers of energy pulses.

Figure 6 shows a diagram with a bridge on the OTT and an additional low-frequency key.

Figure 7 shows the generated pulse with a power of 40 kW.

Fig. 8 shows examples of energy distribution.

The implementation of the invention

Example 1. In the circuit of FIG. 1, an adjustable-form energy pulse generator comprises a high voltage source 1 with a maximum voltage Uc_max, in parallel with which a capacitive energy storage device 2 with a capacitance Sn is connected. Converter 3 (implemented according to the step-down pulse converter circuit) contains two series-connected RF switches 4 with constant reverse conductivity. The positive potential of the high voltage source 1 (point A) is connected to the positive terminal of the first RF key 4. A protective circuit with the properties of a voltage limiter 5 is connected to the terminals of each RF key 4. The negative terminal of the second RF key 4 is connected to the junction point of the reverse diode 6 and the first output of the inductive energy storage device 7 (point B) with inductance Lн. The anode of the reverse diode 6 is connected to the negative potential point of the high voltage source 1 (point G). Between the second terminal of the inductive energy storage device 7 (point C) and the upper terminal of the external process load 9 (point D), a low-frequency switch 8 (low-frequency switch) is installed. The lower terminal of the process load 9 (point E) is connected via a current sensor 10 to the negative potential point of high voltage source 1 (point G). To the control inputs of the RF keys 4 are connected RF drivers 11 operating under the control of the logical signals of the pulse modulator 12 (the drivers form the switching paths of the RF keys). The isolators of the control signals 13 isolate the potentials of the RF drivers 11 and the pulse modulator 12, ensuring the passage of logical signals with a minimum delay.

The reference signal driver 14 is connected to the pulse modulator 12, which comprises a reference waveform adjuster and a reference signal scale adjuster (not shown in FIG. 1). The pulse modulator 12 contains a driver of the mismatch signal, a driver of the frequency and duration of the pulse control RF switches 4 (not shown in figure 1). Pulse modulator 12 provides a control mode by methods of pulse width modulation or pulse frequency modulation. When forming control pulses of the pulse modulator 12, it is possible to take into account other parameters of the process. Additional feedback loops and controller circuits are not shown in FIG. 1 to simplify the circuit. Capacitive energy storage 2 is implemented as a capacitor bank. Inductive energy storage 7 is implemented as a linear choke. Line choke 7 smoothes current ripples due to energy storage, maintains current during periods of interruption and is simultaneously an element of the low-frequency RL filter with inductance, for example, from 1 to 10 mH and active resistance of the line choke to 5 Ohms.

The low-frequency switch 8 provides the termination of the current in the technological load 9 and is implemented on devices capable of switching the maximum charge voltage Uc_max, with Ublock_nch> Uc_max, where Ublock_nch is the voltage at which the low-frequency switch 8 retains its blocking ability.

Reverse diode 6 must have a short reverse recovery time, and its blocking ability must be maintained at a voltage exceeding Uc_max.

To increase the limit switching frequency in the converter 3 (see Fig. 1), the RF switches 4 can be implemented in parallel. Figure 2 shows an example of the connection of the RF keys 4 in a three-phase high-frequency pole containing two sections. Serially connected RF keys 4 are switched synchronously. In parallel, the included RF keys 4 are switched in different phases.

As the RF keys 4, bipolar insulated gate transistors (IGBTs), high-power field effect transistors, or other fully controllable semiconductor switches are used. The blocking ability of the RF keys 4 is determined by the maximum allowable voltage Ublock_vch.

When the RF keys 4 are operated at a high frequency, powerful overvoltage surges with steep edges are generated, limiting the use of RF keys at high voltage. When an overvoltage pulse occurs, the protective circuit 5 sharply decreases its dynamic resistance Rd = f (Uogr) and shunts the RF key 4, dissipating the absorbed energy in the form of heat, limiting the voltage to

Uogr≤Uvch_vch block,

where Uogr is the limiting voltage at the discharge current Irazr_ogr through the protective circuit.

As a voltage limiter for the protective circuit 5, diode voltage limiters, varistors, or a combination of circuits operating on various physical effects are used. The combination of protective circuits provides the specified limiting voltage, maximum limiting current, maximum energy, response time, through-flow capacitance. Known technical solutions can protect the RF keys 4 in the circuit of figure 1, but with insufficient use of RF keys on voltage. Voltage limiters with a sharp transition from the current blocking state to the state of low dynamic resistance Rd = f (Uogr) have not yet been created, and their use in the circuit of Fig. 1 would not solve the problem of allocating huge active peak power during high-frequency switching of the RF key at the limit voltages. A feature of the use of the protective circuit 5 in the circuit of FIG. 1 is that it operates in areas of low dynamic resistance when a relatively low voltage is applied to the RF switches 4. Between the maximum voltage Uc_max, the voltage Ublock_hf_i of the HF column section, the limiting voltage Uog_i of the section of the protective circuit 5, the relations:

and

where n is the number of sections of the HF column.

The value of the coefficient kzap can be from 1 to 1.2. The charge voltage of the capacitive storage device is allowed to exceed the maximum permissible voltage of the RF key (RF column), i.e., when kap <1, but provided that the protective circuit 5 strictly provides for each section of the RF column the ratio Uogr≤Ublock_vch.

When the points C and F are closed (Fig. 1), the current Irazr_gr flows through the protective circuit 5 when the capacitive energy storage device 2 is charged and unwanted thermal energy is released in the protective circuit 5, which can damage it. To avoid undesirable discharge current, it is provided that the low-frequency switch 8 is turned on only in the phase of formation of the adjustable current pulse.

With the beginning of the discharge of energy at a high charge voltage of the capacitive energy storage device 2, a passive high-frequency switching mode of the RF switches 4 is provided. The growth of their switching current is limited by a series choke 7. When turned off, the protective circuit 5 receives part of the interrupted discharge current Iraz_vch. In other words, the passive switching mode of the RF keys 4 provides a reduction in the share of energy change in the switched circuit during the on and off phases of the RF keys. Switching losses in RF switches 4 are reduced when they are turned on or off under the action of the current of the protective circuit 5. For example, in a situation where the protective circuit 5 provides a continuous discharge current, at least with a low process load resistance and a maximum charge voltage Uc_max capacitive energy storage 2. Figure 3 shows the current pulses Isr_hv through the RF key 4 and Isr_gr through the protective circuit 5 and the current pulses Iobr through the return diode 6 (at Uc = 2200 V and a short circuit between points D and E). When the voltage Uc increases, the current Iraz_ogr increases through the protective circuit 5 and the number of switching of the RF key 4 with the generation of thermal energy in the protective circuit 5 decreases significantly. The protective circuit 5 dynamically balances the voltage on the RF keys 4 during non-synchronous switching of the series-connected RF keys 4 The maximum power of the protective circuit 5 must not be exceeded in case of a short circuit between points D and E.

The use of current feedback is able to ensure the safe operation of the RF key 4 and the RF key 8 during a short circuit in the generated current circuit and reduce the number of switching of the RF key 4 under the action of the protective circuit current 5. For this, the turn-off delay time t back of the RF key 4 when the desired current value specified by the pulse modulator is exceeded, set:

where Rx = Uc_max / Irazr_max - characteristic resistance;

Irazr_max - maximum permissible discharge current.

In this case, the excess energy of the energy storage is converted into thermal energy, which is generated and dissipated by the protective circuit.

The pulse modulator 12 is galvanically isolated from the shaper circuits, except for the connection to the current sensor, which eliminates the need for optoelectronic isolators of analog signals and reduces the delay time t-control of the RF key.

The generated energy distribution in the pulse can be either predetermined or adaptable to the technological load. To form a pulse in the process load 9, the capacitive storage 2 is pre-charged from the high voltage source 1 to the voltage Uc. Undervoltage on the capacitive energy storage 2 does not allow to obtain the required energy distribution in the generated pulse. In this situation, the pulse modulator 12 controls the RF key 4 with a minimum duty cycle of the control pulses. Before generating a pulse, it is desirable to measure the resistance of the process load 9 to determine the optimal charge voltage of the capacitive energy storage 2. Turn on the pulse modulator 12 and the low-frequency switch 8. Form the reference signal in the former 14 in an analog and / or digital manner. At the same time, the duration of the generated pulse begins to be counted, and the pulse modulator 12 provides control of the time of the open and / or closed state of the RF key 4 in the current feedback loop. After completion of the countdown, the pulse modulator 12 is turned off. The switching of the RF key 4 is interrupted. LF-key 8 break the unregulated current circuit. LF key 8 is set to a stationary closed state.

Example 2. Figure 4 shows an example of a functional diagram of a bipolar pulse shaper with an adjustable shape. Between points C and F, the upper (Z) and lower (S) terminals of the bridge 15 are installed. Four low-frequency keys 8 form the shoulders of the bridge 15. Between the shoulders of the bridge 15 (points X and Y) the technological load is set 9. When switching the low-frequency keys 8 provide: a change in the current direction of the generated pulse; open circuit; shunting the technological load with 9 shoulders of the bridge 15. In parallel with the technological load 9 at the points X and Y, a low-pass filter capacitor 16 is installed.

Example 3. Perhaps the embodiment of the invention in circuits containing several pulse shapers. In the circuit of Fig. 5, separate shapers of positive and negative polarity are used with operation in different phases, which makes it possible to form a bipolar controlled pulse. A change in the direction of the current at the process load 9 is provided with a corresponding switch from one converter 3 and the low-frequency switch 8 to another converter 3 and the low-frequency switch 8.

Example 4. Figure 6 shows an example of a controlled-shape bipolar pulse shaper circuit with a bridge 15 containing low-frequency keys 8 based on OTT and an additional low-frequency key 17 with constant reverse conductivity. The low-frequency switch 17 is installed between the linear inductor 7 (at point C) and the upper point of the thyristor bridge 15 (at point Z). The RF keys 4 are turned on when the LF-key 17 is turned on first. The LF-key 17 is turned off after the HF-keys are turned off 4. A protective circuit 5 is installed in parallel with the LF-key 5. A current sensor 10 is installed between points F and G 10. Between points F and Z voltage sensor 18 is installed.

The control device 19 receives information about the charge voltage of the capacitive storage 2 from the current sensor 10 and from the voltage sensor 18. The control device 19 provides the charge adjustment of the capacitive energy storage 2 and controls the operation of the RF keys 4, the LF key 17, the LF keys 8. Figure 7 shows the discharge pulse of a capacitive energy storage device 2 with a pulse power of 40 kW.

To generate a pulse of energy of an adjustable shape, for example, positive polarity, turn on the low-frequency key 17, then turn on the high-frequency keys 4 and low-frequency keys 8 (OTT VS1 and VS4). To complete the pulse formation, the HF keys 4 are transferred to a stationary closed state and the LF key 17 is closed. In this case, the discharge current circuit Ires breaks. The energy stored in the linear inductor 7 causes a negative current to flow through the diodes of the RF keys 4, the capacitive energy storage 2 and the lock-out OTT VS1 and VS4, closing the circuit through the diode of the low-frequency switch 17.

Example 5. When calculating the basic elements of the transducer 3 (circuit of FIG. 1, FIG. 4, FIG. 5, FIG. 6 or other embodiments of the invention), the forms of the desired energy distribution are taken into account.

On Fig shows examples of the distribution of energy in pulses of an adjustable shape, which can be implemented using the invention.

Figure 20 - increase in energy from a certain initial level with areas of zero energy.

Figure 21 - uniform distribution of energy.

Figure 22 - energy distribution with a given slew rate.

Figure 23 is a sequence of pulses of increasing amplitude of a sinusoidal shape.

Figure 24 - the growth of energy to a given level, its stabilization at this level for a given time and the transition to another level of stabilization.

The authors made the working models of the pulse shapers of the defibrillator according to the scheme of Fig.6. The following results were obtained:

- the formation of pulses in the form of a reference signal with a smooth increase in current to a level of 20 A at a load of 100 Ohms (see Fig.7);

- tested the possibility of implementing repetitive short circuit modes with a maximum voltage of 2400 V;

- achieved stabilization of the generated current in the range from 0.5 A to 30 A;

- the time to establish current stabilization after an abrupt decrease in load resistance from 100 to 50 Ohms was not more than 20 μs;

- the maximum error of setting the energy of 260 J in the technological load when bipolar pulses are generated at a load of 50 Ohms at a voltage on a capacitive energy storage device of 2000 - 2400 V was not more than ± 4% when carrying out more than 10,000 discharges.

The technical result is achieved due to the fact that they provide the ability to discharge energy at high permissible voltages of the high-frequency switch or high-voltage column based on it. This opportunity is provided by installing a protective circuit with the properties of a voltage limiter in a special application mode, the introduction of a low-frequency switch and a high-speed mode of stabilization of the current of the pulse shaper. With an increase in the maximum allowable charge voltage of the capacitive energy storage device, it becomes possible to increase the energy of the regulated pulses, the range of regulation of the pulse parameters and / or reduce the dimensions of the capacitive energy storage. The ability to increase the working frequency of the RF key at high voltages contributes to the accuracy of setting the shape of the adjustable pulse. An excessively high charge voltage of the energy storage device leads to the rapid conversion of excess energy into thermal energy released in the protective circuit. At the same time, dynamic losses are reduced at each switching of the RF key and the frequency of its switching at the critical section of the discharge. The pulse energy can increase, decrease in one or several stages, change direction, fluctuate relative to predetermined levels regardless of changes in load resistance. The generated energy distribution in the pulse can be predetermined or adaptable to the technological load.

Thus, the goal - increasing the energy of pulses, increasing accuracy and expanding the range of regulation of parameters, reducing dimensions, as well as increasing reliability - has been achieved.

Claims (6)

1. Shaped energy pulse generator for influencing the technological load, comprising at least one capacitive energy storage device and one converter based on an inductive energy storage device and a key, the key passing or blocking the discharge current of a capacitive energy storage device with a high switching frequency with control from a pulse modulator, characterized in that the converter contains one or more series-connected keys with constant reverse conductivity (RF keys ), forming sections of the high-frequency column (HF column), a protective circuit is connected parallel to the HF key (each section of the HF column), which limits the voltage on the HF key (on each section of the HF column), the protective circuit has appropriately selected parameters and passes the discharge current of the capacitive energy storage device, exhibiting restrictive properties, at a voltage that does not exceed the maximum charge voltage of the capacitive energy storage device, and at which the RF key or sections of the RF column retain their blocking ability, and at least one switch is installed in the action circuit of the process load current, capable of blocking the discharge current of a capacitive energy storage device at a low frequency. 2. The shaper according to claim 1, characterized in that at least the feedback loop for the current of the process load, which is regulated by the current level of the reference signal, is used in the circuits of the pulse modulator. 3. The shaper according to claim 1, characterized in that at least one bridge polarity current switch in the process load is installed in the circuit of the generated energy pulses, containing keys capable of blocking the discharge current of the capacitive energy storage. 4. The shaper according to claim 3, characterized in that the bridge current polarity switch in the process load is based on single-operation triode thyristors (OTTs). 5. The shaper according to claim 1 or 3, characterized in that it comprises a combined bridge circuit for switching polarity, using at least one RF switch switching at high frequency as part of the bridge. 6. The shaper according to claim 1, characterized in that it is formed by converters with low-frequency keys, which discharge separated and / or electrically connected capacitive energy storage devices, simultaneously or in different phases.

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