High-precision ac switching power supply with parallel ring current suppression

Abstract

The application discloses a kind of high-precision ac switching power supply of realizing parallel loop current suppression;It includes multiple bridge inverter modules in parallel, Delta-Sigma control module, dead zone module and synchronization module;The driving logic output by Delta-Sigma control module is set after dead time, and after synchronization module, corresponding switch tube in parallel bridge inverter circuit is synchronously driven, input DC voltage is converted into square wave, and AC output is obtained after filtering.The application, since the midpoint voltage sampling of each parallel inverter module bridge arm is combined and then fed back, the voltage drop is not completely compensated, so the loop current can effectively balance the voltage of parallel module, so there is a larger loop impedance between parallel modules to suppress loop current, and the noise shaping characteristics of Delta-Sigma control can suppress high-precision error, so high-precision ac switching power supply for suppressing parallel loop current can be realized.

Description

Technical Field

[0001] This invention belongs to the field of switching power supply technology, and more specifically, relates to a high-precision AC switching power supply that achieves parallel circulating current suppression. Background Technology

[0002] High-precision switching AC power supplies for power stages have important applications in precision manufacturing, precision measurement, and medical fields. Delta-sigma modulation control can achieve good accuracy, but due to its excellent error suppression capability, the voltage drop caused by the large output current is also effectively compensated. Therefore, extremely low relative voltage difference must be maintained between parallel modules; otherwise, the relative voltage difference will generate a large loop current. However, due to detection and control reasons, achieving an extremely low relative voltage difference between parallel modules is very difficult in practice.

[0003] Parallel technology in switching power supplies can easily increase power capacity. At the same time, by sharing the load, small-sized, high-efficiency, and low-power switching transistors are suitable for parallel small modules. Compared with a single high-power switching transistor, higher efficiency and smaller size can be achieved, which is very suitable for precision manufacturing fields such as lithography machines, where vacuum limitations and heat dissipation are extremely important.

[0004] Therefore, researching and implementing parallel connection technology for high-precision switching power supplies is of great significance. Summary of the Invention

[0005] To address the shortcomings and improvement needs of existing technologies, this invention provides a high-precision AC switching power supply based on Delta-Sigma modulation to suppress parallel loop current. Its purpose is to increase the parallel loop impedance while ensuring high-precision output, thereby suppressing the parallel loop current and achieving high precision in the power stage.

[0006] To achieve the above objectives, the present invention provides a high-precision AC switching power supply that suppresses parallel circulating current, the specific solution of which is as follows.

[0007] An AC switching power supply based on Delta-Sigma modulation includes a sampling module, multiple inverter modules connected in parallel, a Delta-Sigma control module, a dead-time setting module, and a synchronization module; wherein:

[0008] The sampling module is used to sample the voltage signal at the midpoint of each inverter module bridge arm and convert it into a digital signal;

[0009] The Delta-Sigma control module combines the digital signals of the voltage sampling at the midpoint of the inverter module's bridge arm, integrates the difference between the signal and the given signal, and then compares the result with zero in the comparator to generate the drive signal logic.

[0010] The dead-time setting module is connected between the Delta-Sigma control module and the synchronization module and is used to set the dead time. The synchronization module, based on the drive signal obtained from the Delta-Sigma control module, logically drives the corresponding switch on the bridge inverter circuit where the inverter module is located, converts the input DC signal into a square wave signal, and obtains the AC output after filtering.

[0011] In this invention, there are two or more inverter modules.

[0012] In this invention, the Delta-Sigma control module includes an integrator and a comparator. The integrator integrates the difference between the digital signal sampled from the midpoint voltage of the inverter module bridge arm and a given signal. The comparator compares the integration result with a preset reference voltage to generate drive signal logic.

[0013] In this invention, the output terminal of the inverter module, i.e., the midpoint of the bridge arm, is connected to an LC filter.

[0014] In this invention, the weight of the data signal sampled by the sampling module before merging is inversely proportional to the inductance L of the LC filter. If the inductance is the same, the weight is the same.

[0015] In this invention, the bridge inverter circuit is a half-bridge or full-bridge inverter circuit.

[0016] In this invention, a diode is connected in reverse parallel to the switching transistor, and a dead-time setting module is used to adjust the dead time so that during the dead time, the inductor current in the LC filter circuit continuously decreases through the diode in the upper or lower bridge arm.

[0017] In this invention, the delta-sigma control module can control the switching frequency and duty cycle of the switching transistors in the bridge inverter circuit.

[0018] In this invention, the dead-time setting module is also used to adjust the dead-time. Since the dead-time effect is equivalent to adding a voltage increment after an ideally modulated inverter circuit without a dead-time, it can be considered equivalent to a resistive element in terms of volt-ampere characteristics. Simultaneously, it can integrate various damping effects in the inverter, including the equivalent series resistance of the filter inductor, the on-state resistance of the switching devices, line resistance, etc. The longer the dead-time, the more pronounced this damping effect.

[0019] The AC switching power supply of this invention includes multiple parallel bridge inverter modules, a Delta-Sigma control module, a dead-time module, and a synchronization module. The drive logic output from the Delta-Sigma control module, after being set with a dead time, drives the switching transistors in the parallel bridge inverter circuit via the synchronization module, converting the input DC voltage into a square wave, which is then filtered to obtain the AC output. In this invention, because the voltage drop is not fully compensated due to the combined feedback of the midpoint voltage acquisition of each parallel inverter module's bridge arm, the loop current effectively balances the voltage of the parallel modules. Therefore, there is a large loop impedance between the parallel modules, while the Delta-Sigma control achieves extremely low output impedance by suppressing external high-precision errors, thus realizing a high-precision parallel AC switching power supply. Overall, the above technical solution conceived in this invention can achieve the following beneficial effects:

[0020] (1) By utilizing the noise shaping characteristics of delta-sigma modulation, the voltage drop caused by the current can be compensated very highly, and its output impedance is very low, which can achieve the high precision of AC switching power supply.

[0021] (2) The voltage at the midpoint of the bridge arm of each parallel inverter module is sampled, combined, and then negatively fed into the integrator. The resulting drive signal synchronously drives the corresponding switch of each inverter. Therefore, if the sampling weights are the same, the voltage drop compensation for a single inverter due to the current flowing through it is only 1 / N, not all of it. As a result, the current between the loops will cause a large voltage drop. In addition, the other inverters will also synchronously compensate to increase the voltage and further reduce the loop current. Therefore, there will be a large impedance inside the loop, which makes the circulating current after parallel connection smaller, and parallel connection can be realized.

[0022] (3) At the same switching frequency, the longer the dead time, the greater the loop impedance. However, the loop impedance is also positively correlated with the frequency. An excessively long dead time will prevent the Delta-Sigma ring from changing quickly, thereby reducing the switching frequency. Therefore, it is necessary to select an appropriate dead time to make the loop impedance larger. Attached Figure Description

[0023] Figure 1A A schematic diagram of the circuit structure for delta-sigma control in a single half-bridge topology.

[0024] Figure 1B This is the control block diagram for delta-sigma.

[0025] Figure 1C The input Bode plot and error Bode plot for delta-sigma.

[0026] Figure 1DThis is a schematic diagram of noise shaping in delta-sigma for errors that are equivalent to white noise.

[0027] Figure 2 This is a schematic diagram of the circuit structure of an AC switching power supply that achieves parallel circulating current suppression based on Delta-Sigma modulation in the case of two half-bridges connected in parallel, as provided in an embodiment of the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0029] In this invention, the terms "first," "second," etc. (if present) in the invention and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0030] Figure 1A-1D This is a schematic diagram illustrating the working principle of an AC power supply. Figure 2 This is a schematic diagram of the circuit structure of an AC switching power supply that achieves parallel circulating current suppression based on Delta-Sigma modulation in the case of two half-bridges connected in parallel, as provided in an embodiment of the present invention. (See also...) Figure 1A-1D and Figure 2 This paper provides a detailed description of the AC switching power supply based on Delta-Sigma modulation to suppress parallel circulating current in this embodiment.

[0031] This invention discloses an AC switching power supply for parallel circulating current suppression using Delta-Sigma modulation, comprising multiple bridge inverter modules connected in parallel, a Delta-Sigma control module, a dead-time setting module, and a synchronization module; wherein:

[0032] The Delta-Sigma control module is used to sample and combine the voltage at the midpoint of the inverter module's bridge arm, then integrate and compare the difference between the voltage and the given signal before outputting the drive logic.

[0033] The dead-time setting module is used to set the dead-time.

[0034] The synchronization module is used to synchronize the drive signals of the corresponding switching transistors of the parallel module. After the drive logic output by the Delta-Sigma control module is set with a dead time, it drives the switching transistors in the parallel bridge inverter circuit through the synchronization module, converting the input DC voltage into a square wave, which is then filtered to obtain the AC output.

[0035] Because the voltage drop is not fully compensated due to the combined feedback of the midpoint voltage acquisition of each parallel inverter module bridge arm, the loop current can effectively balance the voltage of the parallel modules. Therefore, there is a large loop impedance between the parallel modules. Delta-Sigma control achieves extremely low output impedance by suppressing external high-precision errors, thus realizing a high-precision parallel AC switching power supply.

[0036] Furthermore, the internal control process includes a sampling module, an integrator, a comparator, a dead-time setting module, a synchronization module, and a drive circuit.

[0037] The sampling module samples the voltage signal at the midpoint of the bridge arm and converts it into a digital signal. The integrator integrates the difference and outputs the integration result to the comparator. The comparator compares the integration result with the preset reference voltage and generates the drive signal logic. The dead-time setting module sets the dead-time duration. The synchronization module converts the drive signal into a drive signal for synchronizing the switching transistors of the parallel inverter. The drive circuit drives the switching transistors of the parallel bridge inverter circuit according to the drive signal.

[0038] Figure 1A In the control block diagram shown, the integrator gain can be set to K. -sT Used in equivalent delay circuits. From a physical perspective, the input x(t) can be approximated as a constant value over several control cycles. The input value is subtracted from the quantized output value, and the integrator integrates the result of the subtraction. By ensuring that the integrated value fluctuates within a small range, the output can be pulse-equivalent to the input. From a mathematical perspective, Figure 1B In the control block diagram shown, the transfer function of the input signal x(t) is:

[0039]

[0040] The transfer function of the error signal e(t) is:

[0041]

[0042] The Bode plot of this structure under suitable parameters is as follows: Figure 1C As shown. See also Figure 1C As can be seen, the transfer function of the input signal exhibits low-pass characteristics, meaning that the input signal attenuates very little after delta-sigma modulation; the error transfer function, on the other hand, exhibits high-pass filtering properties, thus suppressing low-frequency errors; this is known as noise shaping. Figure 1DAs shown, adding a filter afterwards enables error suppression across the entire frequency band, thereby achieving high-performance output. Due to its excellent error suppression capability, the voltage drop caused by the large output current is also effectively compensated. Therefore, an extremely low relative voltage difference must be maintained between the parallel modules; otherwise, the relative voltage difference will generate a large loop current. However, due to detection and control reasons, achieving an extremely low relative voltage difference between parallel modules is very difficult in practice.

[0043] The voltage at the midpoint of the bridge arm of each parallel inverter module is sampled, combined, and then negatively fed back into the integrator. The resulting drive signal synchronously drives the corresponding switching transistor of each inverter. Therefore, if the sampling weights are the same, the voltage drop compensation for a single inverter due to the current flowing through it is only 1 / N, not all of it. This results in a significant voltage drop between loops. In addition, the other inverters will also synchronously compensate by increasing the voltage to further reduce the loop current. Therefore, there will be a large impedance inside the loop, resulting in a smaller circulating current after parallel connection, thus enabling parallel connection. The key is to increase the parallel loop impedance while ensuring high-precision output, thereby suppressing the parallel loop current and achieving a high-precision parallel switching power supply for the power stage.

[0044] like Figure 2 Taking two inverters connected in parallel as an example, the voltage at the midpoint of each arm of the parallel bridge inverter circuit is sampled and combined before entering the integrator. With equal weights, if the voltage of inverter A drops by ΔU1 at a certain moment, after sampling and Delta-Sigma modulation, the voltage of inverters A and B will rise by ΔU1 / 2. This process repeats until an equilibrium state is reached. However, due to the noise shaping characteristics of Delta-Sigma modulation, the total output will remain essentially unchanged, thus ensuring that the high-precision output is not pulled down by the current.

[0045] Furthermore, regarding the circulating current generated by the two inverters, when the circulating current causes the voltage of inverter A to drop by ΔU... e After compensation, the voltage of inverter A drops by ΔU. e / 2, Inverter B voltage rises by ΔU e / 2, in terms of volt-ampere characteristics, is equivalent to having a large impedance. Therefore, this scheme can suppress the parallel loop current, thereby realizing a high-precision parallel switching power supply for the power stage.

[0046] In this embodiment, due to the noise shaping characteristics of delta-sigma modulation, various errors such as bridge arm midpoint quantization and dead-time effects can be effectively suppressed, thereby achieving a high-precision inverter power supply on the output side. Simultaneously, within the loop, the voltage at the bridge arm midpoint of each parallel inverter module is sampled, first combined, and then negatively fed back into the integrator. The resulting drive signal synchronously drives the corresponding switching transistor of each inverter. Therefore, if the sampling weights are the same, from a single perspective, the voltage drop compensation increase for a single inverter due to the flowing current is only 1 / N, not all of it. This results in a significant voltage drop between loops. Furthermore, the other inverters also synchronously compensate by increasing the voltage to further reduce the loop current. From the perspective of volt-ampere characteristics, this is equivalent to a large impedance. Therefore, there is a large impedance within the loop, resulting in a smaller circulating current after parallel connection, thus enabling parallel connection.

[0047] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-precision AC switching power supply for achieving parallel circulating current suppression, characterized in that, It includes a sampling module, Multiple inverter modules, Delta-Sigma control module, dead-time setting module, and synchronization module connected in parallel; among which: The sampling module is used to sample the voltage signal at the midpoint of each inverter module bridge arm and convert it into a digital signal; The Delta-Sigma control module combines the digital signals of the voltage sampling at the midpoint of the inverter module's bridge arm, integrates the difference between the signal and the given signal, and then compares the result with zero in the comparator to generate the drive signal logic. A dead-time setting module, connected between the Delta-Sigma control module and the synchronization module, is used to set the dead time. The synchronization module, based on the drive signal obtained from the Delta-Sigma control module, logically synchronizes the drive signal to the corresponding switch on the bridge inverter circuit where the inverter module is located, converting the input DC signal into a square wave signal, which is then filtered to obtain the AC output. Wherein: There are two or more inverter modules; The Delta-Sigma control module includes an integrator and a comparator. The integrator integrates the difference between the digital signal sampled at the midpoint voltage of the inverter module's bridge arm and the given signal. The comparator compares the integration result with a preset reference voltage to generate drive signal logic. A diode is connected in reverse parallel to the switching transistor. The dead time setting module is used to adjust the dead time so that the inductor current in the LC filter circuit continuously decreases through the diode in the upper or lower bridge arm during the dead time.

2. The AC switching power supply according to claim 1, characterized in that, The output of the inverter module is connected to the LC filter at the midpoint of the bridge arm.

3. The AC switching power supply according to claim 1, characterized in that, The weight of the data signals sampled by the sampling module before merging is inversely proportional to the inductance L of the LC filter. If the inductance is the same, the weights are the same.

4. The AC switching power supply according to claim 1, characterized in that, A bridge inverter circuit can be either a half-bridge or a full-bridge inverter circuit.

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