An rTMS pulse generation circuit and control method

Abstract

The application discloses an rTMS pulse generating circuit and a control method, and belongs to the field of transcranial magnetic stimulation or pulse generating circuit. The rTMS pulse generating circuit comprises two parts of a charging circuit and a discharging circuit. The charging circuit adopts a series resonant converter topology, which is composed of a full-bridge inverter circuit, a resonant inductor, a resonant capacitor, a high-frequency transformer, a secondary side rectifier diode and an energy storage capacitor; and the discharging circuit is an inductance connection type discharging circuit, which is composed of two unidirectional diodes, a freewheeling inductor, an LC parallel resonant unit and a discharging switch tube. The application defines the ratio of the product of three key indicators of the pulse width, the discharging frequency and the magnetic induction intensity of the rTMS device to the input voltage as the required gain of the rTMS device, and directly proves that the rTMS device of different application scenarios can be individually designed by reasonably selecting the range of the switching frequency.

Description

Technical Field

[0001] The present invention relates to the field of transcranial magnetic stimulation or pulse generating circuits, and in particular to an rTMS pulse generating circuit and a control method. Background Art

[0002] Repetitive Transcranial Magnetic Stimulation (rTMS) has been widely used in clinical research and treatment of neuropsychiatric diseases due to its advantages of being non-invasive, easy to operate, and non-invasive. Figure 2 Before the output pulse, the thyristor Q1 is turned on and Q2 is turned off, and the charging circuit raises the rectified DC voltage to the required voltage level; when the output pulse is turned off, Q1 is turned off and Q2 is turned on, and the capacitor C o To coil L o Rapid discharge forms a pulse AC current. The main problem of this circuit is that the thyristor Q1 o During the resonance process, the device will be subjected to a high voltage stress resulting from the sum of the DC voltage and the capacitor discharge voltage. At the same time, the circuit adds a current-limiting resistor to prevent excessive charging current, thereby exacerbating the energy loss of the rTMS device. Summary of the Invention

[0003] In response to the shortcomings of the existing technology, the present invention proposes an rTMS pulse generation circuit and control method to solve the problem that the magnetic field and frequency of current rTMS devices cannot be adjusted over a wide range as needed and the problem that the voltage stress of the thyristor branch of traditional rTMS devices is too large.

[0004] The purpose of the present invention can be achieved through the following technical solutions:

[0005] An rTMS pulse generating circuit includes an SRC circuit and an inductively connected discharge circuit;

[0006] The SRC circuit consists of a first switch tube Q1, a second switch tube Q2, a third switch tube Q3, a fourth switch tube Q4, a resonant inductor L r , resonant capacitor C r , transformer T, first rectifier diode D1, second rectifier diode D2, third rectifier diode D3, fourth rectifier diode D4, and energy storage capacitor C; on the primary side of the SRC circuit, the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, and the fourth switch tube Q4 form a full-bridge inverter circuit, the first switch tube Q1 and the second switch tube Q2 are in the same phase bridge arm, the third switch tube Q3 and the fourth switch tube Q4 are in the same phase bridge arm, and a resonant inductor L is connected in series between the two bridge arms. r , resonant capacitor C rThe primary side winding of the transformer T; the secondary side of the SRC circuit, the first rectifier diode D1, the second rectifier diode D2, the third rectifier diode D3 and the fourth rectifier diode D4 form a diode bridge, the first rectifier diode D1 and the second rectifier diode D2 are in the same phase bridge arm, the third rectifier diode D3 and the fourth rectifier diode D4 are in the same phase bridge arm, the input ends of the two bridge arms are connected with the connection terminals of the secondary side winding of the transformer T, and the positive and negative buses at the output end of the rectifier bridge formed by the first rectifier diode D1, the second rectifier diode D2, the third rectifier diode D3 and the fourth rectifier diode D4 are connected with the positive and negative terminals of the energy storage capacitor C respectively.

[0007] The inductive connection type discharge circuit is composed of the energy storage capacitor C, the freewheeling inductor L, the fifth diode D5, the sixth diode D6, the output capacitor C o , the output inductor L o , the discharge switch tube Q5, the output inductor L o and the collector of the discharge switch tube Q5, and a series circuit formed by the output capacitor C o , the output inductor L o and the discharge switch tube Q5 is connected in parallel to form a discharge unit, one end of the discharge unit connected with the output inductor L o is connected with the freewheeling inductor L, the other end of the discharge unit is connected with the anode of the sixth diode D6, the other end of the freewheeling inductor L is connected with the cathode of the fifth diode D5, the anode of the fifth diode D5 is connected with the positive electrode of the energy storage capacitor C, and the cathode of the sixth diode D6 is connected with the negative electrode of the energy storage capacitor C.

[0008] Further, the switch tubes of the SRC circuit are controlled by fixed pulse width variable frequency control, the pulse width of the switch tubes of the SRC circuit is greater than half of the resonance period of the resonance inductor L r and half of the resonance period of the resonance capacitor C r , and the pulse width of the switch tubes of the SRC circuit is less than one resonance period of the resonance inductor L r and one resonance period of the resonance capacitor C r .

[0009] The first switch tube Q1, the second switch tube Q2, the third switch tube Q3 and the fourth switch tube Q4 have the same switching period and duty cycle; wherein the drive waveforms of the first switch tube Q1 and the second switch tube Q2 are the same, the drive waveforms of the third switch tube Q3 and the fourth switch tube Q4 are the same, and the drive waveforms of the third switch tube Q3 and the fourth switch tube Q4 lag the drive waveforms of the first switch tube Q1 and the second switch tube Q2 by half a switching period.

[0010] The pulse width of the discharge switch tube Q5 is greater than half of the resonance period of the output inductor L o and half of the resonance period of the output capacitor C ohalf of a resonance period, the pulse width of the discharge switch Q5 is less than the output inductor L o one resonance period and the output capacitor C o one resonance period.

[0011] Further, the SRC charging circuit has two working modes in the upper half of the switching period [t0, t4]; wherein, the stage [t0, t1] is a forward resonance stage, the stage [t1, t3] is a reverse resonance stage, and the stage [t3, t4] is a zero current stage.

[0012] The resonance current i Lr in the forward resonance stage and the reverse resonance stage is expressed as:

[0013]

[0014] wherein, V in is the input voltage of the circuit, V C (0) is the DC component of the energy storage capacitor voltage, Z r = (L r / C r ) 1 / 2 is the resonance impedance of the SRC circuit, ω r = (L r C r ) 1 / 2 is the resonance angular frequency of the SRC circuit, and n is the turns ratio of the secondary winding to the primary winding of the transformer.

[0015] Further, the inductance connection type discharge circuit has three stages in a discharge period [t'0, t'5]: a parallel resonance stage [t'0, t'3], an inductance freewheeling stage [t'3, t'4], and a zero current stage [t'4, t'5].

[0016] Parallel resonance stage [t'0, t'3]: in the stage [t'0, t'1], the output capacitor voltage v Co (t) is greater than the DC component of the energy storage capacitor voltage V C (0), and no current flows through the freewheeling inductor L; in the stage [t'1, t'3], the energy storage capacitor C charges the parallel resonance branch of the output inductor L o and the output capacitor C o , and the output capacitor voltage v Co (t) and the output inductor current i Lo (t) satisfy:

[0017]

[0018] wherein, V Co (0) is the discharge voltage of the rTMS device, R emsis the output inductor L o , output capacitor C o , the equivalent series resistance of the discharge unit composed of the discharge switch Q5, Z o =(L o / C o ) 1 / 2 is the resonant impedance of the inductively connected discharge circuit, ω o =(L o C o ) 1 / 2 is the resonant angular frequency of the inductively connected discharge circuit;

[0019] At t'3, the output inductor current i Lo (t) drops to zero, and the parallel resonance stage [t'0, t'3] ends;

[0020] Inductor freewheeling stage [t'3, t'4]: freewheeling inductor L, energy storage capacitor C and output capacitor C o Resonance; at t'4, the freewheeling inductor current i L (t) drops to 0, the output capacitor voltage v Co (t) rises to the discharge voltage V Co (0) are equal, the inductor freewheeling phase [t'3, t'4] ends;

[0021] Zero current stage [t'4, t'5]; freewheeling inductor current i L (t), output inductor current i Lo (t) are all zero, the output capacitor voltage v Co (t) is clamped to the discharge voltage V Co (0), waiting for the next turn-on signal of the discharge switch tube Q5 to arrive.

[0022] Furthermore, the switching frequency f of the SRC circuit s satisfy:

[0023] Where, M is the demand gain; f g is the discharge frequency of the rTMS device; T o is the pulse width of the rTMS device; f o =1 / T o is the resonant frequency of the inductively connected discharge circuit; f r =ω r / (2π) is the resonant frequency of the SRC circuit; δ is the output capacitor voltage v Co (t) After a pulse width T o The decay coefficient of duration; is the switching frequency f s About the resonant frequency f of the SRC circuit rThe switching frequency per unit value; is the discharge frequency f g Regarding the resonant frequency f of the inductively connected discharge circuit o The discharge frequency per unit value; k is the required gain M and the switching frequency The slope of the per-unit linear relationship.

[0024] Furthermore, the output inductor L o and output capacitor C o satisfy

[0025] Furthermore, the value of the freewheeling inductor L is much larger than the output inductor L o , freewheeling inductor current i L (t) and the peak value of the output inductor current i Lo The peak value of (t) satisfies:

[0026] The voltage v of the energy storage capacitor C C (t) is determined by the ripple voltage Δv of the energy storage capacitor C (t) and the DC component of the energy storage capacitor voltage V C (0), the capacitance of the energy storage capacitor C can be adjusted so that the ripple voltage of the energy storage capacitor Δv C (t) is less than the DC component of the energy storage capacitor voltage V C (0) is selected, and the capacitance of the energy storage capacitor C satisfies the inequality:

[0027] Furthermore, the resonant inductor L r and resonant capacitor C r Satisfies the inequality:

[0028] Among them, f s_ceil is the switching frequency f of the SRC charging circuit s The upper limit switching frequency, The upper limit switching frequency f of the SRC circuit s_ceil About the resonant frequency f of the SRC circuit r The per-unit value, is the maximum switching frequency f at the maximum required gain s_max About the resonant frequency f of the SRC circuit r Per unit value, T c The time required to charge the energy storage voltage to the maximum discharge voltage, V Co (0) _max is the maximum discharge voltage.

[0029] Furthermore, the sampling control level d is synchronized with the drive signal of the switch tube Q5, and the pulse width of the sampling control level T d for:

[0030]

[0031] On the other hand, the present invention further provides a method for controlling the rTMS pulse generating circuit as described in any one of the above, comprising the following steps:

[0032] The discharge voltage V Co (0) and the reference voltage V Co (0) ref After the difference is made, it is input into the PI controller and the output switching frequency change Δf s ; Change the switching frequency Δf s and the switching frequency reference value f s_ref Add up to get the final switching frequency f s ; Among them, the switching frequency reference value f s_ref As a feedforward quantity, it is determined by the demand gain M;

[0033] When the charging speed needs to be accelerated, the discharge voltage V Co (0) Charge to reference voltage V Co (0) ref Previously, the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, and the fourth switch tube Q4 all used the upper limit switching frequency f s_ceil ; Discharge voltage V Co (0) Reach the reference voltage V Co (0) ref After that, the unidirectional switch switches to the switching frequency f obtained by PI compensation s After the amplitude limiting link, a PWM waveform is output to realize variable frequency and constant pulse width control of the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, and the fourth switch tube Q4.

[0034] Beneficial effects of the present invention:

[0035] Compared with bidirectional pulse generating circuits on the market, the rTMS pulse generating circuit provided by the present invention replaces the thyristor branch and related driving circuit that withstand high voltage stress with a freewheeling inductor. This reduces equipment costs while eliminating the current-limiting resistor, thereby improving system operating efficiency.

[0036] The present invention uses the charge conservation principle of the energy storage capacitor C within a discharge cycle to calculate the gain expression of the pulse generating circuit. Combined with the charging speed of the SRC, this paper provides a parameter design basis that can meet the design requirements of the rTMS device, such as pulse width, discharge frequency range, and magnetic induction intensity range. This provides a reference standard for the personalized and demand-based design of weak magnetic field rTMS devices.

[0037] The present invention provides a constant voltage closed-loop frequency conversion control method for the rTMS pulse generating circuit, which ensures the stimulation intensity of the pulse while outputting pulses at a high frequency.

[0038] In addition to being used in conjunction with SPIO nanoparticles for biological experiments and clinical research, the present invention also has certain reference significance for the application design of portable magnetic stimulation devices or extremely low frequency magnetic stimulation devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The present invention will be further described below with reference to the accompanying drawings.

[0040] Figure 1 This is a main circuit topology diagram of an rTMS pulse generating circuit of the present invention;

[0041] Figure 2 This is the basic principle diagram of the conventional rTMS biphasic pulse circuit on the market;

[0042] Figure 3 1 is a working mode diagram of the SRC charging circuit of the present invention;

[0043] Figure 4 It is the main waveform diagram of the SRC charging circuit of the present invention;

[0044] Figure 5 is a working mode diagram of the inductive connection type discharge circuit of the present invention;

[0045] Figure 6 1 is a main waveform diagram of the inductively connected discharge circuit of the present invention;

[0046] Figure 7 Schematic diagram of the parameter selection of resonant inductor and resonant capacitor in the parameter design method proposed in the present invention;

[0047] Figure 8 This is a block diagram of the constant voltage closed-loop variable frequency control strategy proposed by the present invention to match the pulse generating circuit;

[0048] Figure 9 This is the main waveform diagram of the embodiment of the present invention under the conditions of a discharge frequency of 100 Hz and a magnetic induction intensity of 100 mT;

[0049] Figure 10 Detailed diagram of the main waveforms of the embodiment of the present invention under the conditions of a discharge frequency of 100 Hz and a magnetic induction intensity of 100 mT;

[0050] Figure 11 This is the main waveform diagram of the embodiment of the present invention under the conditions of a discharge frequency of 5 Hz and a magnetic induction intensity of 5 mT;

[0051] Figure 12Detailed diagram of the main waveforms of an embodiment of the present invention under the conditions of a discharge frequency of 5 Hz and a magnetic induction intensity of 5 mT. DETAILED DESCRIPTION

[0052] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making any creative efforts shall fall within the scope of protection of the present invention.

[0053] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0054] The present invention provides a weak magnetic field rTMS pulse generating circuit with widely adjustable frequency and field strength, such as Figure 1 As shown, specifically:

[0055] One part is composed of four IGBT switches Q1~Q4, resonant inductor L r , resonant capacitor C r The series resonant converter charging circuit (SRC) consists of a transformer T, rectifier diodes D1 to D4, and energy storage capacitor C. Among them, the switch tubes Q1 to Q4 adopt fixed pulse width variable frequency control, and the pulse width is greater than the resonant inductor L r , resonant capacitor C r The half resonant period is less than the entire resonant period, and the switch tubes Q1 / Q4 and Q 2 / Q3 has the same driving waveform, except that Q2 / Q3 lags Q1 / Q4 by half a switching cycle.

[0056] The other part is composed of energy storage capacitor C, freewheeling inductor L, diodes D5, D6, output capacitor C o , output inductor L o , and the discharge switch tube Q5 constitutes an inductive connection type discharge circuit. Among them, the switching frequency of the switch tube Q5 is the discharge frequency required by the rTMS device, and its pulse width is greater than the output inductor L o , output capacitor C o half of the resonant period and less than the entire resonant period.

[0057] from Figure 3 、 Figure 4It can be seen that the SRC charging circuit has two working modes in the upper half of the switching cycle [t0, t4]. Among them, the [t0, t1] stage is a forward resonance stage, the [t1, t3] stage is a reverse resonance stage, and the [t3, t4] stage is a zero current stage. The resonance current i Lr The expression is:

[0058]

[0059] In the formula, V in is the input voltage of the circuit, V C (0) is the DC component of the energy storage capacitor voltage, Z r =(L r / C r ) 1 / 2 is the resonance impedance of the SRC circuit, ω r =(L r C r ) 1 / 2 is the resonance angular frequency of the SRC circuit, and n is the turns ratio of the secondary winding to the primary winding of the transformer.

[0060] From Figure 5 , Figure 6 It can be seen that the working mode of the inductance connection type discharge circuit in a discharge cycle [t'0, t'5] can be divided into three stages: parallel resonance stage [t'0, t'3], inductance freewheeling stage [t'3, t'4], and zero current stage [t'4, t'5].

[0061] Mode 1: Parallel resonance stage [t'0, t'3]. In the [t'0, t'1] stage, the output capacitor voltage v Co (t) is greater than the DC component of the energy storage capacitor voltage V C (0), and no current flows through the inductor L; at t'1, the output capacitor voltage v Co (t) starts to be less than the DC component of the energy storage capacitor voltage V C (0), so in the [t'1, t'3] stage, the energy storage capacitor C charges the output inductor L o , the output capacitor C o parallel resonance branch. The output capacitor voltage v Co (t) and the output inductor current i Lo (t) are:

[0062]

[0063] In the formula, V Co (0) is the discharge voltage of the rTMS device, R ems is the output inductor L o , the output capacitor C o, the equivalent series resistance of the discharge unit composed of the discharge switch Q5, Z o = (L o C o ) 1 / 2 is the resonant impedance of the inductively connected discharge circuit, ω o = (L o C o ) 1 / 2 is the resonant angular frequency of the inductively connected discharge circuit;

[0064] At the moment t'3, the output inductor current i Lo (t) drops to zero, and the mode 1 ends.

[0065] Mode 2: inductor freewheeling phase [t'3, t'4]. The freewheeling inductor L resonates with the energy storage capacitor C and the output capacitor C o At the moment t'4, the output inductor current i L (t) drops to 0, and the output capacitor voltage v Co (t) rises to be equal to the discharge voltage V Co (0), and the mode ends.

[0066] Mode 3: zero-current phase [t'4, t'5]. In the phase [t'4, t'5], the freewheeling inductor current i L (t) and the output inductor current i Lo (t) are both zero, and the output capacitor voltage v Co (t) is clamped to the discharge voltage V Co (0), waiting for the next conduction signal of the discharge switch Q5.

[0067] The product of the key indicators of the rTMS device, the discharge frequency f g , the discharge voltage V Co (0), and the pulse width T o , and the ratio of the input voltage V in is defined as the required gain M, which can be calculated by the charge-discharge balance of the energy storage capacitor C in one discharge period T g The expression of the required gain M is as follows:

[0068]

[0069] In the formula, M is the required gain; f g is the discharge frequency of the rTMS device; T o is the pulse width of the rTMS device; f o = 1 / T o is the resonant frequency of the inductively connected discharge circuit; f r = ω r / (2π) is the resonant frequency of the SRC circuit; and δ is the output capacitor voltage vCo (t) is a pulse width T o The attenuation coefficient of the time length; The switching frequency f s The switching frequency unit of the SRC circuit resonance frequency f r The switching frequency unit of the SRC circuit resonance frequency f The discharge frequency f g The discharge frequency unit of the inductive connection type discharge circuit resonance frequency f o The discharge frequency unit of the inductive connection type discharge circuit resonance frequency f The slope of the linear relationship between the required gain M and the switching frequency

[0070] Obviously, the required gain M and f s * The range [M min , M max ] of the required gain M can be met by adjusting the switching frequency f s .

[0071] Based on the known required gain range [M min , M max ], the parameters of the pulse generating circuit meet the following conditions:

[0072] 1. The output inductance L o , the output capacitance C o

[0073] The output inductance L o , the output capacitance C o determine the output pulse width of the rTMS device, so only the inductance L o , the capacitance C o need to be selected to meet .

[0074] 2. The value of the freewheeling inductance L and the energy storage capacitance C

[0075] In order to not affect the waveform of the output inductance current i Lo (t), the freewheeling inductance current i L (t) should be much smaller than the output inductance current i Lo (t), and the ratio of the peak value of the current i L (t) to the peak value of i Lo (t) is

[0076] The voltage v C (t) of the energy storage capacitor C is composed of the energy storage capacitor ripple voltage Δv C (t) and the energy storage capacitor voltage DC component V C (0), and the capacitance of the energy storage capacitor C can be determined by making the energy storage capacitor ripple voltage Δv C(t) is less than the DC component of the energy storage capacitor voltage V C (0) is selected, and the capacitance of the energy storage capacitor C satisfies the inequality:

[0077]

[0078] 3. Resonant inductor L r , resonant capacitor C r Selection

[0079] Taking into account the frequency division function of the control chip, the rapidity of charging the energy storage capacitor, and the required gain range [M min , M max ], to ensure that the switches Q1 to Q4 achieve soft switching and other factors, the above variables should satisfy the following inequalities:

[0080]

[0081] Among them, f s_ceil is the switching frequency f of the SRC charging circuit s The upper limit switching frequency, The upper limit switching frequency f of the SRC circuit s_ceil About the resonant frequency f of the SRC circuit r The per-unit value, is the maximum switching frequency f at the maximum required gain s_max About the resonant frequency f of the SRC circuit r Per unit value, T c The time required to charge the energy storage voltage to the maximum discharge voltage, V Co (0) _max is the maximum discharge voltage;

[0082] According to the above inequality, the resonant inductance L can be obtained r The selection range of the resonant capacitor Cr is as follows: Figure 7 shown.

[0083] This application proposes a constant voltage closed loop variable frequency control strategy for an rTMS pulse generating circuit. The control block diagram is as follows: Figure 8 shown.

[0084] Combined with the sampling control level d, the output capacitance C can be extracted o Voltage v Co (t) discharge voltage V Co (0), the sampling control level d is synchronized with the drive signal of the switch tube Q5, and its pulse width T d for:

[0085]

[0086] The discharge voltage VCo (0) and the reference voltage V Co (0) ref The difference is input to the PI controller, and the output is the change amount of the switching frequency Δf s ; the change amount of the switching frequency Δf s is added to the switching frequency reference value f s_ref to obtain the final switching frequency f s ; wherein the switching frequency reference value f s_ref is determined by the demand gain M as a feedforward amount.

[0087] When the charging speed needs to be accelerated, the first switch Q1, the second switch Q2, the third switch Q3 and the fourth switch Q4 all use the upper limit switching frequency f s_ceil before the charging voltage V Co (0) is charged to the reference voltage V Co (0) ref ; after the discharge voltage V Co (0) reaches the reference voltage V Co (0) ref , the one-way switch switches to the switching frequency f s obtained by PI compensation, and the PWM waveform is output after the limiting link to realize the variable-frequency fixed-pulse width control of the first switch Q1, the second switch Q2, the third switch Q3 and the fourth switch Q4.

[0088] The technical solutions of the present application will be described clearly and in detail below with reference to the accompanying drawings. The described embodiments are part of the embodiments of the present application, but not all of the embodiments.

[0089] In this example, according to the above parameter design principle and closed-loop control strategy, a rTMS pulse generation circuit platform capable of generating a 5-100mT magnetic field, a pulse width of 200μs and a frequency of 5-100Hz adjustable is built. The main experimental parameters are shown in Table 1.

[0090] Table 1 Experimental parameters of Example 1

[0091] Parameter Value <![CDATA[输入电压V in / V]]> 311 Discharge voltage V Co (0) / V]]> 19.25～385 Discharge frequency / Hz 5～100 Resonant inductance L r / μH 300 Resonant capacitor C r / nF]]> 50 Transformer primary to secondary turns ratio 1:2 Free-wheeling inductance L / mH 7 Energy storage capacitor C / μF 1500 Output inductance L o / μH 15.3 Output capacitor C o / μF 66

[0092] In this example, through finite element simulation analysis, the current required to generate a 5-100mT magnetic induction intensity is 40-800A, and under the current selection, the discharge voltage V Co (0) can be calculated as 19.25-385V.

[0093] Figure 9 , Figure 10 are the main waveforms under the working condition of a discharge frequency of 100Hz and a magnetic induction intensity of 100mT; Figure 11 , Figure 12The main waveforms are shown in the figure under the working condition of 5Hz discharge frequency and 5mT magnetic induction intensity. The original side SRC charging current i Lr The density of the waveforms can be seen, and the requirements of different working conditions can be met by changing the switching frequency of Q1-Q4, which is consistent with the previous analysis; at the same time, the constant voltage closed-loop variable frequency control strategy ensures that the pulse current i Lo can reach the set stimulation intensity under different discharge frequency requirements.

[0094] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above examples, and the above examples and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application.

Claims

1. An rTMS pulse generating circuit, characterized in that: Including SRC circuit and inductive connection type discharge circuit; The SRC circuit consists of a first switch tube Q1, a second switch tube Q2, a third switch tube Q3, a fourth switch tube Q4, a resonant inductor L r , resonant capacitor C r , transformer T, first rectifier diode D1, second rectifier diode D2, third rectifier diode D3, fourth rectifier diode D4, and energy storage capacitor C; on the primary side of the SRC circuit, the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, and the fourth switch tube Q4 form a full-bridge inverter circuit, the first switch tube Q1 and the second switch tube Q2 are in the same phase bridge arm, the third switch tube Q3 and the fourth switch tube Q4 are in the same phase bridge arm, and a resonant inductor L is connected in series between the two bridge arms. r , resonant capacitor C r , the primary winding of the transformer T; on the secondary side of the SRC circuit, the first rectifier diode D1, the second rectifier diode D2, the third rectifier diode D3, and the fourth rectifier diode D4 form a diode rectifier bridge, the first rectifier diode D1 and the second rectifier diode D2 are the same phase bridge arm, the third rectifier diode D3 and the fourth rectifier diode D4 are the same phase bridge arm, the input ends of the two bridge arms are respectively connected to the connection terminals of the secondary winding of the transformer T, and the positive and negative busbars of the output end of the rectifier bridge composed of the first rectifier diode D1, the second rectifier diode D2, the third rectifier diode D3, and the fourth rectifier diode D4 are respectively connected to the positive and negative ends of the energy storage capacitor C; The inductive connection type discharge circuit consists of energy storage capacitor C, freewheeling inductor L, fifth diode D5, sixth diode D6, output capacitor C o , output inductor L o , discharge switch tube Q5; output inductor L o It is connected to the collector of the discharge switch tube Q5, and the series circuit formed by the two and the output capacitor C o The output capacitor C o and output inductor L o One end is connected to the freewheeling inductor L, and the other end of the discharge unit is connected to the anode of the sixth diode D6; the other end of the freewheeling inductor L is connected to the cathode of the fifth diode D5, the anode of the fifth diode D5 is connected to the positive electrode of the energy storage capacitor C, and the cathode of the sixth diode D6 is connected to the negative electrode of the energy storage capacitor C.

2. The rTMS pulse generating circuit according to claim 1, wherein: The switching tubes of the SRC circuit all adopt constant pulse width variable frequency control. The pulse width of the switching tubes of the SRC circuit is greater than the resonant inductor L r Half resonant cycle and resonant capacitance C r During the half resonant cycle, the pulse width of the switch tube of the SRC circuit is smaller than the resonant inductor L r One resonant cycle and resonant capacitance C r A resonant cycle of The first switch Q1, the second switch Q2, the third switch Q3, and the fourth switch Q4 have the same switching period and duty cycle. The driving waveforms of the first switch Q1 and the second switch Q2 are the same, and the driving waveforms of the third switch Q3 and the fourth switch Q4 are the same. Furthermore, the driving waveforms of the third switch Q3 and the fourth switch Q4 lag behind the driving waveforms of the first switch Q1 and the second switch Q2 by half a switching period. The pulse width of the discharge switch tube Q5 is greater than the output inductor L o half resonant cycle and output capacitance C o During the half resonant cycle, the pulse width of the discharge switch Q5 is smaller than the output inductor L o One resonant cycle and the output capacitor C o A resonant cycle.

3. The rTMS pulse generating circuit according to claim 2, characterized in that: The SRC charging circuit has two operating modes in the first half of the switching cycle [t0, t4]. Among them, the [t0, t1] stage is the forward resonance stage, the [t1, t3] stage is the reverse resonance stage, and the [t3, t4] stage is the zero current stage. The resonant current i in the forward resonance stage and the reverse resonance stage Lr The expression is: Where V in is the input voltage of the circuit, V C (0) is the DC component of the energy storage capacitor voltage, Z r =(L r / C r ) 1 / 2 is the resonant impedance of the SRC circuit, ω r =(L r C r ) 1 / 2 is the resonant angular frequency of the SRC circuit, and n is the turns ratio of the secondary winding to the primary winding of the transformer.

4. The rTMS pulse generating circuit according to claim 3, characterized in that: The operating mode of the inductive connection type discharge circuit in a discharge cycle [t'0, t'5] includes three stages: parallel resonance stage [t'0, t'3], inductive freewheeling stage [t'3, t'4], and zero current stage [t'4, t'5]. Parallel resonance stage [t'0, t'3]: At [t'0, t'1], the output capacitor voltage v Co (t) is greater than the DC component of the energy storage capacitor voltage V C (0), no current flows through the freewheeling inductor L; in the [t'1, t'3] stage, the energy storage capacitor C is the output inductor L through the freewheeling inductor L. o and output capacitor C o The parallel resonant branch is charged, and the output capacitor voltage v Co (t) and the output inductor current i Lo (t) Satisfy: Where V Co (0) is the discharge voltage of the rTMS device, R ems is the output inductor L o , output capacitor C o , the equivalent series resistance of the discharge unit composed of the discharge switch Q5, Z o =(L o / C o ) 1 / 2 is the resonant impedance of the inductively connected discharge circuit, ω o =(L o C o ) 1 / 2 is the resonant angular frequency of the inductively connected discharge circuit; At t'3, the output inductor current i Lo (t) drops to zero, and the parallel resonance stage [t'0, t'3] ends; Inductor freewheeling stage [t'3, t'4]: freewheeling inductor L, energy storage capacitor C and output capacitor C o Resonance; at t'4, the freewheeling inductor current i L (t) drops to 0, the output capacitor voltage v Co (t) rises to the discharge voltage V Co (0) are equal, the inductor freewheeling phase [t'3, t'4] ends; Zero current stage [t'4, t'5]; freewheeling inductor current i L (t), output inductor current i Lo (t) are all zero, the output capacitor voltage v Co (t) is clamped to the discharge voltage V Co (0), waiting for the next turn-on signal of the discharge switch tube Q5 to arrive.

5. The rTMS pulse generating circuit according to claim 1, wherein: The switching frequency f of the SRC circuit s satisfy: Where, M is the demand gain; f g is the discharge frequency of the rTMS device; T o is the pulse width of the rTMS device; f o =1 / T o is the resonant frequency of the inductively connected discharge circuit; f r =ω r / (2π) is the resonant frequency of the SRC circuit; δ is the output capacitor voltage v Co (t) After a pulse width T o The decay coefficient of duration; is the switching frequency f s About the resonant frequency f of the SRC circuit r The switching frequency per unit value; is the discharge frequency f g Regarding the resonant frequency f of the inductively connected discharge circuit o The discharge frequency per unit value; k is the required gain M and the switching frequency The slope of the per-unit linear relationship.

6. The rTMS pulse generating circuit according to claim 5, characterized in that: Output inductor L o and output capacitor C o satisfy 7. The rTMS pulse generating circuit according to claim 5, characterized in that: The value of the freewheeling inductor L is much larger than the output inductor L o , freewheeling inductor current i L (t) and the peak value of the output inductor current i Lo The peak value of (t) satisfies: The voltage v of the energy storage capacitor C C (t) is determined by the ripple voltage Δv of the energy storage capacitor C (t) and the DC component of the energy storage capacitor voltage V C (0), the capacitance of the energy storage capacitor C can be adjusted so that the ripple voltage of the energy storage capacitor Δv C (t) is less than the DC component of the energy storage capacitor voltage V C (0) is selected, and the capacitance of the energy storage capacitor C satisfies the inequality:

8. The rTMS pulse generating circuit according to claim 1, characterized in that , resonant inductor L r and resonant capacitor C r Satisfies the inequality: Among them, f s_ceil is the switching frequency f of the SRC charging circuit s The upper limit switching frequency, The upper limit switching frequency f of the SRC circuit s_ceil About the resonant frequency f of the SRC circuit r The per-unit value, is the maximum switching frequency f at the maximum required gain s_max About the resonant frequency f of the SRC circuit r Per unit value, T c The time required to charge the energy storage voltage to the maximum discharge voltage, V Co (0) _max is the maximum discharge voltage.

9. The rTMS pulse generating circuit according to claim 1, characterized in that , the sampling control level d is synchronized with the drive signal of the switch tube Q5, and the pulse width of the sampling control level is T d for:

10. A method for controlling an rTMS pulse generating circuit according to any one of claims 1 to 9, characterized in that , including the following steps The discharge voltage V Co (0) and the reference voltage V Co (0) ref After the difference is made, it is input into the PI controller and the output switching frequency change Δf s ; Change the switching frequency Δf s and the switching frequency reference value f s_ref Add up to get the final switching frequency f s ; Among them, the switching frequency reference value f s_ref As a feedforward quantity, it is determined by the demand gain M; When the charging speed needs to be accelerated, the discharge voltage V Co (0) Charge to reference voltage V Co (0) ref Previously, the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, and the fourth switch tube Q4 all used the upper limit switching frequency f s_ceil ; Discharge voltage V Co (0) Reach the reference voltage V Co (0) ref After that, the unidirectional switch switches to the switching frequency f obtained by PI compensation s After the amplitude limiting link, a PWM waveform is output to realize variable frequency and constant pulse width control of the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, and the fourth switch tube Q4.

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