Transformer secondary winding grouping winding series output voltage boosting circuit

Abstract

This invention discloses a transformer secondary winding grouped and series-connected output boost circuit, including a transformer, transformer equivalent leakage inductance, compensation capacitor, and rectifier circuit. The transformer secondary winding has a large number of turns, divided into n windings. Each winding is rectified individually and then connected in series to obtain the final high-voltage output. This method can reduce transformer leakage inductance and parasitic capacitance, and reduce voltage stress on the rectifier circuit. However, due to inconsistent coupling degrees between the multiple secondary windings and the primary winding, current imbalance in the windings will occur, affecting the soft switching of devices in the rectifier circuit, increasing losses, and even causing device failure. This invention proposes a series winding current balancing design method, in which a compensation capacitor is connected in series with each secondary winding. By changing the output impedance of the secondary winding through the compensation capacitor, a balanced winding current is obtained.

Description

Technical Field

[0001] This invention belongs to the field of switching power supply technology, and in particular, it is a design method for compensating parasitic leakage inductance of high-frequency transformers. Background Technology

[0002] Switching power supplies are widely used in electronic equipment. In special applications such as medical, radio frequency, electrostatic, and ionization circuits, voltages of several thousand volts or even tens of kilovolts are required. High-frequency transformers, as key components for isolation between stages and energy transfer, are crucial in low-input, high-output applications. The secondary winding of the transformer has a large number of turns. If the output winding uses a single winding with layered windings, the large voltage difference between the starting and ending points of each layer easily leads to significant inter-line coupling capacitance. To avoid this large coupling capacitance, a return line is required, resulting in poorer inter-layer coupling and significant leakage inductance. Both coupling capacitance and leakage inductance cause high voltage spikes during switching, easily damaging the switching transistors. Furthermore, the presence of coupling capacitance or leakage inductance lowers the transformer's conversion efficiency, leading to high heat loss and overall low conversion efficiency. Additionally, the rectifier circuit components will be subjected to significant voltage stress, making selection difficult. Summary of the Invention

[0003] The purpose of this invention is to address the problems existing in the prior art by proposing a transformer secondary winding grouped and series-connected output boost circuit. The transformer's secondary coil is divided into multiple windings, each winding's output connected to a rectifier circuit. The rectified voltages are then connected in series to obtain the final high-voltage output. However, inconsistencies in the coupling degree between the multiple secondary windings and the primary winding can lead to current imbalance in the windings, affecting the soft switching of devices in the rectifier circuit, increasing losses, and even causing device failure. Therefore, this invention proposes a series winding current balancing design method. A compensation capacitor is connected in series with each secondary winding. By changing the output impedance of the secondary winding through the compensation capacitor, a balanced winding current is obtained.

[0004] The technical solution to achieve the objective of this invention is: a multi-winding transformer series output boost circuit, comprising an excitation source, a transformer, the transformer's equivalent leakage inductance and compensation capacitor, and a rectifier circuit. The excitation source current i r The waveform is a sine wave with a frequency of f. r The secondary winding of the transformer is split into multiple windings, and each winding is connected to a rectifier circuit. The output voltages of the rectifier circuits are connected in series to obtain the final high output voltage. The purpose of boosting voltage is achieved by connecting multiple circuits in series.

[0005] Because the secondary winding of a transformer has multiple windings, layered and wound on the central column of the magnetic core, with the primary winding wrapped around the innermost secondary winding, the further the secondary winding is from the primary winding, the lower its coupling degree, meaning its equivalent leakage inductance is larger, essentially equivalent to an inductor connected in series with the secondary winding. Due to this leakage inductance, the transformer secondary current will be distorted, no longer a sine wave. This will prevent the devices in the rectifier circuit from achieving zero-current switching, increasing losses and even causing device failure, and also generating significant electromagnetic interference. Connecting a compensation capacitor in series with each secondary winding to counteract the effect of leakage inductance on the current will effectively solve this problem.

[0006] Specifically, a transformer secondary winding grouped and series-wound output boost circuit includes an excitation source, a transformer, a transformer equivalent compensation module, and a rectifier circuit; the transformer includes a primary winding P and n secondary windings S1, S2, ..., S... n The rectifier circuit includes rectifier circuit 1, rectifier circuit 2, ..., rectifier circuit n; the primary winding P of the transformer is connected to both ends of the excitation source; the transformer equivalent compensation module includes the transformer's equivalent leakage inductance L. k1 L k2 ... L kn and compensation capacitor C k2 C k3 ..., C kn The secondary winding S of the transformer i Connection equivalent leakage inductance L ki One end, equivalent leakage inductance L ki The other end is connected to the input terminal of rectifier circuit i, i = 1, 2, ..., n; the other end of the secondary winding S1 is connected to the other input terminal of rectifier circuit 1; the secondary winding S j The other end is connected to a compensation capacitor C kj One end, compensation capacitor C kj The other end is connected to the other input terminal of rectifier circuit j, j = 2, 3, ..., n; the negative output terminal of rectifier circuit q is connected to the positive output terminal of rectifier circuit i+1, q = 1, 2, ..., n-1.

[0007] Compared with the prior art, the significant advantages of this invention are:

[0008] 1) The secondary winding of the transformer is divided into multiple windings, which can reduce the leakage inductance and parasitic capacitance of the transformer.

[0009] 2) Achieve symmetrical design of secondary winding current to solve the problem of transformer secondary winding current distortion caused by leakage inductance.

[0010] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0011] Figure 1 This is a diagram of a transformer secondary winding grouped and connected in series for output boost circuit.

[0012] Figure 2 This is a schematic diagram of the transformer winding method.

[0013] Figure 3 A schematic diagram of the secondary winding current of the transformer used for compensation.

[0014] Figure 4 A schematic diagram of the secondary winding current of the transformer after compensation.

[0015] Figure 5 The circuit diagram is for a specific embodiment.

[0016] Figure 6 This is a schematic diagram of the secondary winding current of the transformer in an embodiment without a compensation capacitor.

[0017] Figure 7 This is a schematic diagram of the secondary winding current of a circuit transformer in an embodiment with a compensation capacitor. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0019] In one embodiment, such as Figure 1 As shown, the transformer secondary winding grouped series output boost circuit of the present invention includes an excitation source 1, a transformer 2, a transformer equivalent leakage inductance and a compensation capacitor 3, and a rectifier circuit 4.

[0020] Specifically, the excitation source 1 can be any one of a full-bridge LLC circuit, a symmetrical half-bridge LLC circuit, or an asymmetrical half-bridge LLC circuit; the transformer 2 includes a primary winding P and secondary windings S1, S2, ..., S... n The primary winding P of the transformer 2 is connected to both ends of the excitation source 1; the equivalent leakage inductance and compensation capacitor 3 of the transformer include the equivalent leakage inductance L of the transformer 2. k1 L k2 ... L kn and compensation capacitor C k2 C k3 ..., C kn The rectifier circuit 4 includes rectifier circuit 1, rectifier circuit 2, ..., rectifier circuit n, and the rectifier circuit can be either a full-bridge rectifier or a bridge voltage multiplier rectifier. The secondary winding S of the transformer (2) i Connection equivalent leakage inductance L ki One end, equivalent leakage inductance Lki The other end is connected to the input terminal of rectifier circuit i, i = 1, 2, ..., n; the other end of the secondary winding S1 is connected to the other input terminal of rectifier circuit 1; the secondary winding S j The other end is connected to a compensation capacitor C kj One end, compensation capacitor C kj The other end is connected to the other input terminal of rectifier circuit j, j = 2, 3, ..., n; the negative output terminal of rectifier circuit q is connected to the positive output terminal of rectifier circuit i+1, q = 1, 2, ..., n-1.

[0021] In one embodiment, such as Figure 2 As shown, the primary winding P of transformer 2 is on the innermost side, and the secondary winding S... i (i = 1, 2, ..., n) are wound outwards in layers. The secondary winding, which is farther away from the primary winding, has a lower coupling degree with the primary winding and a larger equivalent leakage inductance, i.e., L k1 <L k2 <···<L kn The consequence is that the secondary current of the transformer will be distorted. Figure 3 As shown, it is no longer a sine wave, which will cause the devices in the rectifier circuit to be unable to achieve zero-current switching, resulting in increased losses, or even device failure, and will also generate serious electromagnetic interference.

[0022] A compensation capacitor is connected in series with each secondary winding to counteract the effect of leakage inductance on the current, so that the secondary winding S i Having equal output impedances for all (i = 1, 2, ..., n) will effectively solve this problem. That is:

[0023]

[0024] The compensated transformer secondary current is as follows Figure 4 As shown.

[0025] The circuit simulation of one embodiment of the present invention is given below.

[0026] Application example circuit diagrams are as follows Figure 5 As shown, the excitation source is a full-bridge LLC circuit, and the rectifier circuit is a bridge voltage multiplier rectifier. The specific simulation parameters are as follows:

[0027] Input voltage Vin = 29V;

[0028] Output voltage Vo = 6000V;

[0029] Output current Io = 50mA;

[0030] Switching frequency fs = 55kHz;

[0031] The series resonant inductance Ls = 2.8 μH;

[0032] Series resonant capacitor Cs = 2μF;

[0033] Transformer turns ratio P:S1:S2:S3 = 4:143:143:143;

[0034] Magnetizing inductance Lm = 56 μH;

[0035] Leakage inductance Lk1 = 10μH, Lk2 = 15μH, Lk3 = 20μH;

[0036] The compensation capacitors are Ck2 = 0.56μF and Ck3 = 1.12μF.

[0037] Figure 6 The example circuit without compensation capacitors is given, showing the secondary winding current of the transformer. Figure 7 An example circuit with added compensation capacitors is given. The secondary winding current of the transformer is shown. The simulation waveforms show that after adding compensation capacitors, the current distortion caused by leakage inductance is canceled out, and the current waveforms on the three windings are consistent.

[0038] The technical solutions of the present invention are not limited to the above embodiments. All technical solutions obtained by equivalent substitution fall within the scope of protection claimed by the present invention.

Claims

1. A transformer secondary winding grouping winding series output boost circuit, characterized in that, The circuit includes an excitation source (1), a transformer (2), a transformer equivalent compensation module (3), and a rectifier circuit (4); the transformer (2) includes a primary winding P and n secondary windings S1, S2, ..., S... n The rectifier circuit (4) includes rectifier circuit 1, rectifier circuit 2, ..., rectifier circuit n; the primary winding P of the transformer (2) is connected to the two ends of the excitation source (1); the transformer equivalent compensation module (3) includes the equivalent leakage inductance L of the transformer (2). k1 L k2 ... L kn and compensation capacitor C k2 C k3 ..., C kn The secondary winding S of the transformer (2) i Connection equivalent leakage inductance L ki One end, equivalent leakage inductance L ki The other end is connected to the input terminal of rectifier circuit i, i = 1, 2, ..., n; the other end of the secondary winding S1 is connected to the other input terminal of rectifier circuit 1; the secondary winding S j The other end is connected to a compensation capacitor C kj One end, compensation capacitor C kj The other end is connected to the other input terminal of rectifier circuit j, j = 2, 3, ..., n; the negative output terminal of rectifier circuit q is connected to the positive output terminal of rectifier circuit i+1, q = 1, 2, ..., n-1; Equivalent leakage inductance L k1 <L k2 <···<L kn ; n secondary side windings S i the output impedances are equal, i.e.

2. The transformer secondary winding grouping and winding series output voltage boosting circuit according to claim 1, characterized in that, The excitation source (1) outputs a current which is a sinusoidal wave with a frequency f r , i.e. the frequency of the excitation source current i r .

3. The transformer secondary winding grouping and winding series output voltage boosting circuit according to claim 1, characterized in that, The excitation source (1) is any one of a full-bridge LLC circuit, a symmetric half-bridge LLC circuit and an asymmetric half-bridge LLC circuit.

4. The transformer secondary winding grouping and winding series output voltage boosting circuit according to claim 1, characterized in that, The rectifier circuit is any one of a full-bridge rectifier and a bridge voltage doubler rectifier.

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