A fast-front large-current pulse modulator and control method

Abstract

The present invention discloses a fast-front large-current pulse modulator and a control method. The large-current pulse modulator includes a DC voltage source unit, an inductor unit, a switch unit, an energy storage unit, and a load unit. The switch unit is composed of one or more groups of semiconductor switches to form a half-bridge structure. The inductor unit includes PCB trace inductance, device package inductance, and externally matched equivalent inductance, etc. The present invention proposes a control method for the fast-front large-current pulse modulator. The switches SW1 and SW2 do not conduct alternately. Instead, when the switch tube SW1 conducts, the switch SW2 still conducts for a period of time. At this time, the inductor current in the inductor unit gradually increases. When SW2 is turned off, the large pulse current generated by the inductor unit is used to charge the load, thereby obtaining a fast-front pulse. By using this method, by controlling the common conduction time of the switches, a pulse front far less than 30 ns can be obtained at both ends of the load, and arbitrary adjustment of the rising edge can be achieved simultaneously.

Description

Technical Field

[0001] The present invention belongs to the technical field of pulse power, and particularly relates to a fast-front large-current pulse modulator and a control method. Background Art

[0002] A pulse modulator can convert an input low-level pulse signal into a high-voltage, large-current pulse signal with a certain frequency, pulse width, and amplitude corresponding thereto.

[0003] In recent years, with the development of semiconductor technology, semiconductor laser diodes and gallium nitride high electron mobility transistors (GaN HEMTs) have been widely used in fields such as radar and microwave. For semiconductor lasers, parameters such as their detection range, resolution, and stability are related to electrical parameters such as the amplitude, pulse width, and pulse waveform front edge of the pulse waveform output by the pulse modulator. In order to obtain optimal performance, the pulses generated by the current-type pulse modulator for driving semiconductor lasers must meet requirements such as a fast front (<30 ns), large amplitude, narrow pulse width, and small jitter; on the other hand, in the fields of radar and microwave, in order to achieve high efficiency and high power output of solid-state microwave power amplifiers, the front edge (rise time) of the output current waveform of the pulse modulator should be as steep as possible.

[0004] Most traditional current-type pulse modulators adopt a switching structure, and its main components include: a DC voltage source unit, an energy storage unit, a switching unit, a control module, and its load unit, where the load is a semiconductor laser or a GaN HEMT-type solid-state microwave power amplifier. The function of the DC voltage source unit is to convert the primary power supply into a DC voltage source that meets the requirements; the function of the energy storage unit is to store energy in certain components, such as capacitors, inductors, or artificial transmission lines, to reduce the peak power requirement of the power supply part; the control module generates a pulse control signal with a certain repetition frequency and pulse width to control the conduction and cutoff of the semiconductor switch; the switching unit directly determines certain parameters of the final output pulse. By controlling the closing and opening of the switch, the energy storage unit discharges to the load to form an output pulse with certain frequency, voltage, power, pulse width, and pulse waveform parameters.

[0005] The aforementioned capacitor-storage-discharge pulse modulator primarily generates high-current pulses by discharging the energy storage capacitor into the load when the switch is on. The rising edge of the generated pulse is primarily related to the stray inductance, resistance, capacitance, and switching components in the discharge loop. Stray inductance includes the device package inductance, lead inductance, and printed circuit board (PCB) trace inductance; equivalent resistance includes PCB trace resistance, load equivalent resistance, and the equivalent resistance of the switch when it is on. The choking effect of the inductance slows the rate of current rise. For example, in a certain type of pulse modulator, the PCB trace inductance is approximately 18nH, the device package inductance is approximately 5nH, and the lead inductance is approximately 5nH. This results in a stray inductance of approximately 28nH and an equivalent load resistance of approximately 0.5Ω. The leading edge time constant is τ = L / R, which is calculated to be approximately 60ns. The pulse leading edge rise time is generally 3 to 4 times the time constant τ. Therefore, even if the modulator outputs an ideal "square wave," the rising edge of the current pulse at both ends of the load is still over 100ns, which is difficult to meet the application requirements. In particular, as the modulator becomes modular and miniaturized, and the energy storage unit is placed externally, the stray inductance in the above system will also increase, resulting in a longer output pulse rise time, making it impossible to achieve the high efficiency, high power, and high resolution application requirements. Summary of the Invention

[0006] The present invention addresses the problem that the stray inductance in traditional pulse modulators causes the rise time of their output pulse waveform to slow down, and provides a fast-leading large-current pulse modulator and control method. This solves the problem that the stray inductance inside the pulse modulator and the inductance of the transmission line between the modulator and the load (semiconductor laser or microwave power amplifier) deteriorate the modulated pulse leading edge, and can steepen the pulse waveform leading edge to far less than 30ns, which has important practical value.

[0007] The present invention is achieved by adopting the following technical solutions:

[0008] A fast-leading high-current pulse modulator includes a DC voltage source E1, an energy storage unit, a switch unit, an inductor unit, and a load unit. The switch unit includes switches SW1 and SW2, and the switches SW1 and SW2 form a half-bridge structure.

[0009] One end of the inductor unit is connected to one end of the energy storage capacitor Cs in the energy storage unit, and the other end is connected to one end of the switch unit SW1;

[0010] The negative electrode of the DC voltage source E1 is grounded, and the positive electrode is connected to one end of the energy storage unit. The other end of the energy storage unit is connected to one end of the switch SW1 through the inductor unit. The other end of the switch SW1 is connected to one end of the switch SW2. The other end of SW2 is connected to the ground. The middle point between SW1 and SW2 is VHB , V HB is connected to the midpoint of the cascaded diodes D5 and D6. The anode of diode D6 is grounded, and the cathode is connected to the anode of diode D5 and to V HB . The other end of diode D5 is connected to the midpoint of the energy storage unit and the inductor power supply. One end of the load unit and one end of switch SW2 are connected to V HB . The other end of the load unit is grounded.

[0011] A further improvement of the present invention is that the inductor unit is composed of a printed circuit board trace inductor and a device package inductor or an externally connected equivalent inductor.

[0012] A further improvement of the present invention is that the large inductor current generated by the inductor unit during the simultaneous conduction of switches SW1 and SW2 is used to charge the load, thereby obtaining a fast front pulse current.

[0013] A further improvement of the present invention is that, taking advantage of the characteristic that the inductor current cannot change suddenly, before the energy storage unit discharges the load, the inductor current is used to charge the load to obtain a fast front edge.

[0014] A further improvement of the present invention is that the load unit includes an inductor L1. One end of inductor L1 is connected to the load equivalent capacitor C connected in parallel L and the load equivalent resistor R L , and the other end is connected to V HB .

[0015] A further improvement of the present invention is that switches SW1 and SW2 use MOSFETs as switches.

[0016] A control method for a fast front large current pulse modulator, which is based on the above-mentioned fast front large current pulse modulator, includes:

[0017] Switches SW1 and SW2 do not conduct alternately. When SW1 is turned off, SW2 conducts. In the next cycle, when SW1 conducts and the energy storage unit discharges the load, the conduction state of SW2 is maintained for a period of time.

[0018] A further improvement of the present invention is that by controlling the simultaneous conduction time of switches SW1 and SW2, the adjustment of the rising edge of the output pulse can be achieved.

[0019] The present invention has at least the following beneficial technical effects:

[0020] The high-current pulse modulator of the present invention overcomes the adverse effects of stray inductance in traditional pulse modulators. By using the stray inductance already present in the system as an energy storage element, and without adding extra components, only by changing the control method of the pulse modulator, the output of high-current pulses with fast front edges can be achieved.

[0021] The high-current pulse modulator of the present invention uses stray inductance to generate a relatively large pulse current to charge the load, and can quickly raise the pulse front edge to the specified amplitude within 10 ns - 20 ns, thus enabling a smaller pulse width.

[0022] The high-current pulse modulator of the present invention can achieve the adjustment of any pulse front edge only by changing the control method, so the energy storage unit can be placed outside to realize the miniaturization of the modulator.

[0023] The control method described in the present invention is simple and easy to implement. Compared with the control methods of other multi-switch structures, it is easier to realize, and the rising edge of the generated pulse waveform does not change with the frequency and duty cycle. Description of the Drawings

[0024] Figure 1 Schematic diagram of the composition of a traditional pulse modulator;

[0025] Figure 2 Equivalent circuit when the switch of the traditional pulse modulator is turned on;

[0026] Figure 3 In (a) and (b) are the typical structures and control methods of the traditional pulse modulator;

[0027] Figure 4 In (a) and (b) are the output voltage waveforms at both ends of the load of the traditional fast-front high-current pulse modulator;

[0028] Figure 5 Functional schematic diagram of the composition of the fast-front high-current pulse modulator of the present invention;

[0029] Figure 6 Control method of the switch tube of the fast-front high-current pulse modulator;

[0030] Figure 7 Variation trend of the rising edge of the output waveform of the high-current pulse modulator using the control method of the present invention with different stray inductances.

[0031] Reference numerals are as follows: E1 - DC voltage source, R1 - charging resistor, C S —energy storage capacitor, SW1, SW2 - semiconductor switches, L stray —stray inductance (sum of PCB trace inductance and package inductance), R eq —equivalent resistance, L eq— Lead inductance, L1— Inductance, C L — Load equivalent capacitance, R L — Load equivalent resistance;

[0032] 1 - Energy storage unit, 2 - Clamping unit, 3 - Load unit, 4 - Switch unit, 5 - Inductor unit. Detailed implementation manners

[0033] The present invention will be further described below with reference to the accompanying drawings.

[0034] As Figure 1 shown, a traditional pulse modulator generally consists of a DC voltage source unit E1, an energy storage unit 1, a switch unit 4, and a load unit 3. The energy storage unit 1 includes a charging resistor R1 and an energy storage capacitor C S ; The switch unit 4 includes a semiconductor switch SW1 and a switch control module, etc. (omitted here); The load unit includes a packaged lead inductance L eq and the stray inductance L existing in the system stray , a load equivalent capacitance C L and an equivalent resistance R L . R eq is the equivalent resistance, including the PCB trace resistance, the on - resistance of the switch tube, etc. One end of SW1 is connected to the mid - point between the charging resistor R1 and the energy storage capacitor C S , and the other end is connected to the load unit; One end of the energy storage capacitor C S is grounded, and the other end is connected to the positive pole of the DC voltage source E1 through the charging resistor R1; The load equivalent resistance R L is in parallel with the equivalent capacitance C L and then in series with the equivalent inductance L eq , spanning between one end of the switch SW1 and the ground.

[0035] During the off - period of the switch SW1, the DC voltage source E1 charges the energy storage capacitor C S through the charging resistor R1. When the switch tube SW1 conducts, the energy storage capacitor C S discharges to the load resistor R L , and the energy is transferred to the load. As Figure 2 shown, the circuit can be equivalent to an RLC circuit at this time, satisfying the following relationship:

[0036]

[0037]

[0038]

[0039]

[0040] L=L stray +L eq (5)

[0041] Solving the above relationship, we can see that the rate of change of voltage is mainly affected by the loop resistance (R eq and R L The sum of the two values (and the sum of the two values) and the inductance L. When the resistance in the loop increases or the inductance decreases, the front edge of the output pulse waveform changes faster over time.

[0042] Figure 3 The typical structure and control method of the traditional pulse modulator. SW1 and SW2 are switch units 4 composed of N-type semiconductor MOSFETs, where SW2 can be replaced by a diode. D1 and D2 are parasitic diodes of MOSFETs or external parallel diodes. L eq is the lead inductance, L stray is the stray inductance (the sum of the PCB trace inductance and the MOSFET package inductance). SW1 and SW2 are turned on alternately under the action of the input signal. Figure 3 As shown in (b), when SW1 is turned on, the energy storage capacitor Cs discharges to the load and the energy is transferred to the load. After SW1 is turned off, SW2 is turned on, and both ends of the load are clamped to zero level. At the same time, the DC voltage source E1 charges the energy storage capacitor Cs. Under the alternating action of SW1 and SW2, an approximately square wave V is generated at the middle point of their connection. HB , after passing through the lead inductance, an approximately exponentially rising and falling waveform is obtained at both ends of the load.

[0043] Figure 4 The equivalent load resistance R of the traditional pulse modulator is given. L The modulated pulse waveforms at both ends. As can be seen from Figure 4(a), even at the midpoint of the half bridge V HB When the output pulse rising and falling edges are less than 20ns, the load resistance R L The modulated pulse V at both ends RL The leading and trailing edges are also above 200ns, making it difficult to obtain a faster leading edge. At the same time, as the stray inductance increases, such as Figure 4 As shown in (b), when the stray inductance L stray When the load voltage increases from 20nH to 100nH, the pulse rise at the load end gradually slows down. For GaN HEMT solid-state amplifiers, a slower pulse rise means greater loss, resulting in lower modulator drive efficiency.

[0044] Figure 5Schematic diagram of the composition and function of the fast-leading high-current pulse modulator and its control method. Unlike the traditional pulse modulator, the modulator circuit of the present invention adds a first-level inductor unit (5) between the energy storage unit (1) and the switch unit 4, such as Figure 5 shown. Figure 5 The switches SW1 and SW2 use MOSFET as switches, but the present invention is not limited to this. Any device that can be used as a switch, such as BJT, GaN, SiC, SCR, etc., can be applied to this circuit. The inductor unit (5) can use the stray inductance (PCB trace inductance and package inductance, etc.) in the system, or the equivalent inductance connected in parallel externally, and use the energy accumulated by the stray inductance when the switch is turned on to charge the load, thereby achieving a fast front edge. The clamping unit 2 is composed of diodes D5 and D6 in a cascade form to ensure that the potential of the middle point VHB of the switch unit composed of SW1 and SW2 does not exceed the power supply voltage, thereby achieving protection for the switch tube and the load.

[0045] Figure 6 The control method adopted by the present invention is different from the traditional control method in that the switches SW1 and SW2 are not turned on alternately, but the switch SW1 is turned on and the switch SW2 is kept turned on for a period of time. At this time, the current I Lstray Rapidly increases, the inductor accumulates energy, when its peak current reaches a certain value, disconnect SW2 and keep SW1 on, at this time the current on the stray inductor I Lstray The load is charged, energy is converted, the voltage across the load gradually increases, and the stray inductance current gradually decreases. After a period of time, SW1 is disconnected and SW2 is turned on. The load is clamped to zero level to protect the load. Under the action of the above pulse, a periodic pulse will be generated at the middle point HB between SW1 and SW2. When I Lstray When the current is greater than the set current, the rise time of the pulse can be shortened. By controlling the common conduction time of SW1 and SW2, the stray inductance L can be controlled. stray Peak current I Lstray , thereby achieving the adjustment of the pulse leading edge.

[0046] Figure 7 The output waveform rising edge of the high current pulse modulator using the control method of the present invention changes with different stray inductances L stray As can be seen from the figure, as the inductance increases, the rising edge also tends to slow down. This is because the on-time of switches SW1 and SW2 is constant. When the inductance is larger, the peak current is smaller, and the current charging the load is also smaller, resulting in a slower rising edge. However, at the same time, Figure 4(b) Compared with [the traditional method], it can be seen that its rise time is greatly shortened compared with the traditional method. In addition, when the inductance is constant, the peak current of the inductor can be changed by controlling the common conduction time of SW1 and SW2, thereby realizing the adjustment of the pulse front edge.

[0047] It must be noted that the present invention is not limited thereto, and any person with a basic knowledge of electronic circuits can modify the above structure, but any method of using an auxiliary current source to generate a fast-front large-current pulse is within the protection scope of the present invention.

Claims

1. A fast-front high-current pulse modulator, characterized in that: It includes a DC voltage source E1, an energy storage unit (1), a switching unit (4), an inductor unit (5), and a load unit (3). The switching unit (4) includes switches SW1 and SW2, and switches SW1 and SW2 form a half-bridge structure; One end of the inductor unit (5) is connected to one end of the energy storage capacitor Cs in the energy storage unit (1), and the other end is connected to one end of SW1 in the switching unit (4); The negative terminal of the DC voltage source E1 is grounded, and the positive terminal is connected to one end of the energy storage unit (1). The other end of the energy storage unit (1) is connected to one end of the switch SW1 through the inductor unit (5). The other end of the switch SW1 is connected to one end of the switch SW2, and the other end of SW2 is connected to the ground. The midpoint of the connection between SW1 and SW2 is V HB , V HB is connected to the midpoint of the cascaded diodes D5 and D6. The anode of the diode D6 is grounded, and the cathode is connected to the anode of the diode D5 and to V HB . The other end of the diode D5 is connected to the midpoint between the energy storage unit (1) and the inductor power supply (5). One end of the load unit (3) and one end of the switch SW2 are connected to V HB . The other end of the load unit (3) is grounded; Switches SW1 and SW2 are not turned on alternately, but SW2 remains on for a period of time after switch SW1 is turned on. At this time, the current I Lstray Rapidly increases, the inductor accumulates energy, when its peak current reaches the set value, disconnect SW2 and keep SW1 on, at this time the current on the stray inductor I Lstray The load is charged, energy is converted, the voltage across the load gradually increases, and the stray inductance current gradually decreases. After a period of time, SW1 is disconnected and SW2 is turned on. The load is clamped to zero level to protect the load. Under the action of the pulse, a periodic pulse is generated at the middle point HB between SW1 and SW2. When I Lstray When the current is greater than the set current, the rise time of the pulse can be shortened; By controlling the common conduction time of SW1 and SW2, and then controlling the peak current I of the stray inductance L stray to achieve the adjustment of the pulse front edge. Lstray ​ 2. The fast front large current pulse modulator according to claim 1, characterized in that, The inductor unit (5) is composed of an inductor formed by printed circuit board traces, a device package inductor, or an externally connected equivalent inductor.

3. A fast front large current pulse modulator according to claim 1, characterized in that, The large inductor current generated by the inductor unit (5) during the simultaneous conduction of switches SW1 and SW2 is used to charge the load, thereby obtaining a fast front pulse current.

4. The fast-leading high-current pulse modulator according to claim 3, characterized in that: Based on the characteristic that the inductor current cannot change abruptly, this pulse current charges the load with the inductor current before the energy storage unit (1) discharges the load, thereby obtaining a fast front.

5. A fast-front large-current pulse modulator according to claim 1, characterized in that, The load unit (3) includes an inductor L1. One end of the inductor L1 is connected to the load equivalent capacitor C arranged in parallel L and the load equivalent resistor R L and the other end is connected to V HB .

6. The fast-leading high-current pulse modulator according to claim 1, characterized in that: Switches SW1 and SW2 use MOSFETs as switches.

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