A test power supply and a control method thereof

Abstract

The application discloses a kind of test power supply and its control method, power supply includes LLC full-bridge resonant circuit, the output end of LLC full-bridge resonant circuit is accessed to several roads full-bridge rectifier circuit in parallel, the output end of each road full-bridge rectifier circuit is connected linear filter circuit and full-bridge inverter circuit in turn, the output end of all full-bridge inverter circuit is connected in series and forms output, LLC full-bridge resonant circuit and each rectifier circuit are constituted a switching power supply, each linear filter circuit is a linear power supply.The LLC full-bridge resonant circuit and rectifier circuit of the application constitute switching power supply, linear filter circuit is linear power supply, realizes switching power supply+linear power supply combination output mode, combines the advantages of wide voltage regulating range of switching power supply and high dynamic response of linear power supply, improves output voltage amplitude precision and dynamic load response capability, and reduces voltage ripple.

Description

TECHNICAL FIELD

[0001] The present application relates to a test power supply and a control method thereof, and belongs to the technical field of test power supply. BACKGROUND

[0002] High-voltage test power supplies have been widely used in the test field. When a device is tested for performance and aging, the test power supply needs to provide various forms of voltage and current waveforms, and needs to ensure the stability and precision of the power supply to the greatest extent. In some test scenarios of precision instruments and electronic devices, the power supply needs to output high-amplitude and high-precision voltage, and needs to have certain load stability. However, the existing high-voltage test power supply is limited by the voltage resistance of devices, and usually adopts a resonant type voltage doubling rectifier circuit to output high-voltage direct current. However, the existing high-voltage test power supply has problems such as large output voltage ripple and low voltage amplitude precision. SUMMARY

[0003] The present application provides a test power supply and a control method thereof, which solves the problems disclosed in the background art.

[0004] According to one aspect of the present application, a test power supply is provided, comprising an LLC full-bridge resonant circuit, the output end of the LLC full-bridge resonant circuit being connected to a plurality of parallel full-bridge rectifier circuits, the output end of each full-bridge rectifier circuit being connected to a linear filter circuit and a full-bridge inverter circuit in turn, and the output ends of all full-bridge inverter circuits being connected in series to form an output; wherein the LLC full-bridge resonant circuit and each full-bridge rectifier circuit form a switching power supply, and each linear filter circuit is a linear power supply.

[0005] In some embodiments of the present application, the transformer of the LLC full-bridge resonant circuit is a multi-winding isolation transformer, and each secondary winding of the multi-winding isolation transformer is connected to a full-bridge rectifier circuit.

[0006] In some embodiments of the present application, the output end of the full-bridge rectifier circuit is connected in parallel with a support capacitor.

[0007] In some embodiments of the present application, the linear filter circuit is a linear filter amplifier tube.

[0008] In some embodiments of the present application, the input end of the full-bridge inverter circuit is connected in parallel with a filter capacitor.

[0009] According to another aspect of the present application, a control method of a test power supply is provided, comprising:

[0010] The switching power supplies are controlled by using a closed-loop feedback control method, and the remaining switching power supplies are controlled by using an open-loop control method.

[0011] The linear power supplies are controlled by using a closed-loop feedback control method.

[0012] In some embodiments of the present disclosure, a closed-loop feedback control method is adopted to control each linear power supply, comprising:

[0013] According to the preset total output voltage of the test power supply and the distribution rule, a target value A of the output voltage of each linear power supply is determined; wherein the distribution rule defines the proportion of the output voltage of each linear power supply in the total output voltage;

[0014] For each linear power supply, a control signal of the linear power supply is generated according to the actual output voltage of the linear power supply and the target value A; wherein the control signal of the linear power supply is used to control the linear power supply to take the target value A as the output target.

[0015] In some embodiments of the present disclosure, the control signal of the linear power supply is generated according to the actual output voltage of the linear power supply and the target value, comprising:

[0016] The difference between the actual output voltage of the linear power supply and the target value is calculated, and the amplified difference is taken as the control signal of the linear power supply.

[0017] In some embodiments of the present disclosure, a closed-loop feedback control method is adopted to control any one switching power supply, comprising:

[0018] According to the target value A of the output voltage of the same linear power supply and the preset voltage deviation, a target value B of the output voltage of the switching power supply is determined;

[0019] According to the actual output voltage of the switching power supply and the target value B, a control signal of the switching power supply is generated; wherein the control signal of the switching power supply is used to control the switching power supply to take the target value B as the output target.

[0020] In some embodiments of the present disclosure, the method of generating the control signal of the switching power supply is determined according to the voltage gain between the input and the output of the switching power supply; as the voltage gain increases, the control signal of the switching power supply is generated by using the intermittent control method, the PWM pulse width control method and the PFM frequency control method in turn.

[0021] The beneficial effects achieved by the present application are: 1. The LLC full-bridge resonant circuit and the rectifier circuit of the present application constitute a switching power supply, and the linear filter circuit is a linear power supply, which realizes a switching power supply + linear power supply combined output mode, combines the advantages of wide voltage regulation range of the switching power supply and high dynamic response of the linear power supply, improves the output voltage amplitude precision and dynamic load response capability, and reduces the voltage ripple; 2. The switching power supply proposed by the present application uses the superposition of multiple control methods, obtains the direct current voltage gain according to the input voltage and output voltage of the switching power supply, and converts the control method according to the process from low to high voltage gain, which is intermittent control method, PWM pulse width control method and PFM frequency control method in turn, to adapt to wider voltage output range and wider voltage gain regulation; 3. Any one of the switching power supplies of the present application adopts closed-loop feedback control, and the rest of the switching power supplies adopts open-loop control, which utilizes the linear power supply for voltage stabilizing output, solves the problem of cross regulation of secondary voltage of multi-winding transformer, and realizes decoupling control of front and rear stages, while the switching power supply + linear power supply only provides stable direct current voltage for the rear full-bridge inverter circuit; 4. The output ends of all the full-bridge inverter circuits of the present application are connected in series to form an output, and the high-voltage multi-level output can be formed by superimposing multiple independent levels, and each full-bridge inverter circuit can adjust the width and frequency of the level by changing the conduction time and direction of the switching tube, and the output of the series connection can realize the demand of the switching tube outputting high voltage with low voltage resistance, and can output high amplitude direct current, impact, fast edge, square wave, trapezoidal wave and other voltage waveforms through digital setting. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The principle block diagram of the test power supply is shown in the figure;

[0023] Figure 2 The circuit diagram of the test power supply is shown in the figure;

[0024] Figure 3 The rear output topology structure diagram is shown in the figure;

[0025] Figure 4 The control principle diagram of the test power supply is shown in the figure;

[0026] Figure 5 The control flow chart of the test power supply is shown in the figure. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative, but not as any limitation on the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0028] Unless otherwise indicated, the relative arrangement of components and steps, numerical expressions, and values exemplified in the examples set forth herein are not intended to limit the scope of the disclosure.

[0029] It should be understood that the sizes of the various components shown in the drawings are chosen for convenience only, and do not bear any relationship to actual size or actual proportions.

[0030] Techniques, methods, and apparatus known to those of ordinary skill in the relevant art can not be discussed in detail, but should be considered part of the specification.

[0031] In all of the examples shown and discussed herein, any specific values should be interpreted as merely exemplary and not limiting. Thus, other examples of the exemplary embodiments can have different values.

[0032] It should be noted that like symbols and letters designate like items in the several figures, and that any reference to a particular item in one figure should be understood to refer to the same item in the other figures, unless otherwise stated.

[0033] In order to solve the problems existing in the prior test power supply, the disclosure provides a test power supply and a control method thereof. The test power supply realizes a combination output mode of switching power supply + linear power supply in structure, and forms a high-voltage output after superposition of several independent levels. In control, any one switching power supply adopts closed-loop feedback control, and the rest switching power supplies adopt open-loop control. The test power supply can output high-voltage direct current, impact, fast edge, square wave, trapezoidal wave and other waveforms, and can guarantee the dynamic characteristics and steady-state characteristics of the system, and can realize the working requirements of wide-range output voltage digital adjustment, ultra-low output voltage ripple and dynamic load fast response.

[0034] Referring to Figure 1 For an embodiment of the test power supply of the disclosure, the test power supply in the figure adopts a three-stage cascade scheme, specifically including an LLC full-bridge resonant circuit of a front stage, a full-bridge rectifier circuit and a linear filter circuit of an intermediate stage, and a full-bridge inverter circuit of a rear stage. The output end of the LLC full-bridge resonant circuit is connected to a plurality of parallel full-bridge rectifier circuits, the output end of each full-bridge rectifier circuit is connected to a linear filter circuit and a full-bridge inverter circuit in turn, and the output ends of all full-bridge inverter circuits are connected in series to form a multi-level output. The LLC full-bridge resonant circuit and each rectifier circuit form a switching power supply, and each linear filter circuit is a linear power supply.

[0035] It should be noted that the LLC full-bridge resonant circuit is a prior art circuit, which is a circuit for improving the efficiency and power density of the converter by using the resonance principle, and its working principle is based on the resonant converter, and high-efficiency energy conversion is realized by controlling the switching frequency. The circuit mainly includes a full-bridge structure, a resonant circuit and a transformer. In the embodiment, in order to facilitate the realization of a plurality of independent structures, the transformer of the LLC full-bridge resonant circuit adopts a multi-winding isolation transformer, and each secondary winding of the multi-winding isolation transformer is connected with a full-bridge rectifier circuit.

[0036] Referring to Figure 2 , the LLC full-bridge resonant circuit includes four switching tubes S1-S4, a resonant inductor Lr, a resonant capacitor Cr and a multi-winding isolation transformer T; wherein the switching tubes S1-S4 are specifically MOS tubes, the gate is used as the control end of the LLC full-bridge resonant circuit and the switching power supply, the switching tubes S1-S4 form a full-bridge structure, the input end of the full-bridge structure is connected with a direct current power supply, that is, Vin in the figure, the positive output end and the negative output end of the full-bridge structure are respectively connected with the resonant inductor Lr and the resonant capacitor Cr, the resonant inductor Lr, the resonant capacitor Cr and the primary winding of the multi-winding isolation transformer T are connected in series, and the two ends of each secondary winding are respectively connected with the input end of the full-bridge rectifier circuit.

[0037] The LLC full-bridge resonant conversion circuit can realize zero-voltage turn-on (ZVS) of the primary side switching tube of the multi-winding isolation transformer T and zero-current turn-off (ZCS) of the secondary side of the multi-winding isolation transformer T, the input direct current voltage is converted into an alternating current by the turn-on and turn-off of the four switching tubes S1-S4, the energy is transmitted in the resonant network composed of the resonant inductor Lr, the resonant capacitor Cr and the multi-winding isolation transformer T in a resonant manner, and the direct current gain is converted in the resonant cavity, and finally the output is obtained from the secondary side of the multi-winding isolation transformer T.

[0038] It should be noted that each independent structure is consistent, and taking the four paths in Figure 2 as an example, the full-bridge rectifier circuit includes four rectifier diodes Dn1-Dn4, n=1, 2, 3, 4, and the output end of the full-bridge rectifier circuit is connected with a support capacitor Cn1. The high-frequency resonant alternating voltage output from the secondary side of the multi-winding isolation transformer T is filtered by the full-bridge rectification and the support capacitor Cn1 to form the direct current voltage output from the switching power supply, but a certain ripple voltage is superimposed due to the repeated charging and discharging of the switching elements.

[0039] Referring to Figure 2In the embodiment, the linear filter circuit adopts a linear filter amplifier tube, the drain and source of the MOS tube in the linear filter amplifier tube are connected to the positive output end of the full-bridge rectifier circuit and the positive input end of the full-bridge inverter circuit respectively, and the gate of the MOS tube in the linear filter amplifier tube is used as the control end, i.e. the control end of the linear power supply. By dynamically adjusting the gate-source voltage of the MOS tube, the MOS tube works in the linear region, and the drain-source impedance changes with the gate-source voltage to filter out the voltage ripple of the output of the switching power supply, thereby further improving the output precision of the direct current voltage.

[0040] The test power supply realizes the combined output mode of the switching power supply and the linear power supply, combines the advantages of the wide voltage regulation range of the switching power supply and the high dynamic response of the linear power supply, improves the output voltage amplitude precision and the dynamic load response capability, and reduces the voltage ripple.

[0041] The structure of the full-bridge inverter circuit is similar to that of the full-bridge structure in the LLC full-bridge resonant circuit, and the full-bridge inverter circuit is shown in Figure 2 The full-bridge inverter circuit includes four switching tubes Sn1-Sn4, the switching tubes Sn1-Sn4 form the full-bridge inverter circuit, the input end is connected to the filter capacitor Cn2 in parallel, and the output end is connected in series to form an output loop. The filter capacitor Cn2 provides high-precision and stable direct current voltage for the inverter circuit, and through the combination of the turn-on and turn-off of the switching tubes Sn1-Sn4, positive, negative and zero level waveforms can be generated according to the output requirements of the test power supply.

[0042] The high-voltage multi-level output by the test power supply can be stacked by multiple independent levels (i.e. the level of each output), and each full-bridge inverter circuit can adjust the width and frequency of the level by changing the conduction time and direction of the switching tubes, and the output in series can realize the demand of the switching tube outputting high voltage with low voltage resistance, and can output high-amplitude direct current, impact, fast edge, square wave, trapezoidal wave and other voltage waveforms through digital setting.

[0043] In order to realize the precise and stable output of the test power supply, the control method of the test power supply is also disclosed, and there are mainly three controls in the test power supply, i.e. the switching power supply control, the linear power supply control and the control of the full-bridge inverter circuit.

[0044] The high-voltage level output by the test power supply is stacked by multiple independent levels, and each full-bridge inverter circuit adjusts the width and frequency of the level by changing the conduction time and direction of the switching tubes Sn1-Sn4, and the output in series realizes the demand of the switching tube outputting high voltage with low voltage resistance, and the voltage amplitude range can be -n×Vref to n×Vref, and high-amplitude direct current, impact, fast edge, square wave, trapezoidal wave and other voltage waveforms can be output through digital setting; wherein Vref is the target value A of the output voltage of the linear power supply.

[0045] The control of the full-bridge inverter circuit is a conventional control mode, so in this example, the control of the switching power supply and the linear power supply is mainly described as follows:

[0046] 1) A closed-loop feedback control mode is adopted to control any one switching power supply, and an open-loop control mode is adopted to control the remaining switching power supplies.

[0047] The switching power supplies and the linear power supply of the front stage and the intermediate stage are collectively defined as isolation power supplies, as shown in Figure 3 The output circuit of the rear stage of the test power supply is a series multi-level converter, which is used to output the output ends of multiple full-bridge inverters in series. Since the test power supply adopts a multi-winding isolation transformer to complete the primary loop isolation and power transmission function, if each switching power supply is controlled individually, there will inevitably be a problem of cross regulation of the multi-winding isolation transformer. Therefore, under the limitation of the secondary voltage sampling of the multi-winding isolation transformer and the multi-level output voltage sampling of the rear stage, any switching power supply voltage is selected for closed-loop feedback control, the remaining switching power supplies are controlled in an open-loop mode, and the linear power supply is used for stable voltage output, thereby solving the problem of cross regulation of the secondary voltage, and realizing decoupling control of the front and rear stages.

[0048] It should be noted that the closed-loop feedback control of the switching power supply is a digital closed-loop feedback control, as shown in Figure 4 , i.e., signal loop 1, and the specific control process is as follows:

[0049] 11) According to the target value A (i.e., Vref) of the output voltage of the same linear power supply and the preset voltage deviation (i.e., Vδ, which is preset according to the ripple amplitude of the output voltage of the switching power supply to be filtered out, and is generally within tens of volts), the target value B of the output voltage of the switching power supply is determined; wherein the target value B of the output voltage of the switching power supply can be generally set as Vref+Vδ.

[0050] 12) According to the actual output voltage of the switching power supply and the target value B, the control signal of the switching power supply is generated; wherein the control signal of the switching power supply is used to control the switching power supply to take the target value B as the output target.

[0051] Figure 4 , V1 is the actual output voltage of the switching power supply, since the feedback V1 is an analog quantity, it is necessary to convert V1 into a digital quantity, i.e., to convert it through an ADC, and then according to Vref+Vδ and the converted V1, the control signal of the switching power supply is obtained by using a corresponding method; the purpose of the control signal of the switching power supply is to make the output voltage of the switching power supply Vref+Vδ.

[0052] It should be noted that the control signal of the switching power supply can be generated by using an intermittent control method, a PWM pulse width control method or a PFM frequency control method. Which one to use needs to be determined according to the voltage gain between the input and output of the switching power supply.

[0053] The intermittent control method is fixed switching frequency, fixed small duty cycle, and pulse number adjustment in a period. The PWM pulse width control method is fixed switching frequency and duty cycle adjustment (the maximum duty cycle is 50%). The PFM frequency control method is fixed 50% duty cycle and switching frequency adjustment. The three methods are used together to adapt to a wider voltage variation range of the input and output DC voltages.

[0054] The use of specific control strategies is mainly determined according to the DC voltage gain. The DC voltage gain of the switching power supply is obtained according to the input voltage and the output voltage. The control method is converted according to the order from low to high voltage gain. The intermittent control method is used under the condition of low voltage gain. With the rise of the voltage gain, the pulse number in the adjustment period is adjusted under the intermittent control method to adapt to the change of the voltage gain. Until the switching point is adjusted to the set point, the PWM pulse width control method is switched. The duty cycle adjustment is carried out under the PWM pulse width control method to adapt to the voltage gain change in this stage. When the set point is reached, the switching is converted to the PFM frequency control method. The working frequency of the LLC full-bridge resonant circuit is adjusted under this method to adapt to the remaining voltage gain range, and the target voltage of the switching power supply is realized.

[0055] 2) Use a closed-loop feedback control method to control each linear power supply.

[0056] It should be noted that the closed-loop feedback control of the linear power supply is an analog closed-loop feedback control. See Figure 4 , that is, signal loop 2. The specific control process is as follows:

[0057] 21) According to the total output voltage (i.e. Vout in Figure 2 ) of the test power supply and the distribution rule, the target value A of the output voltage of each linear power supply is determined; wherein the distribution rule defines the proportion of the output voltage of each linear power supply in the total output voltage.

[0058] Assuming that the total output voltage is n x Vref, if the distribution rule is average distribution, the target value A of the output voltage of the linear power supply is Vref. Of course, according to different distribution rules, it can also be 2Vref, 3Vref, etc. The specific value can be set according to the actual situation.

[0059] 22) For each linear power supply, generate a control signal for the linear power supply according to the actual output voltage of the linear power supply and the target value A; wherein the control signal of the linear power supply is used to control the linear power supply to take the target value A as the output target.

[0060] Figure 4 In the formula, V2 is the actual output voltage of the linear power supply, since Vref is a digital quantity, it is necessary to convert Vref into an analog quantity, i.e. to convert it through a DAC, and then to further calculate the difference between the actual output voltage of the linear power supply and the target value, and to take the difference as the control signal of the linear power supply after amplification by an operational amplifier, the purpose of the control signal of the linear power supply being to make the output voltage of the linear power supply Vref.

[0061] Referring to Figure 5 , the specific control method of the test power supply can be as follows:

[0062] S1. According to the given total output voltage, the target value A (i.e. Vref) of the output voltage of each linear power supply is calculated, and the target value B (i.e. Vref+Vδ) of the output voltage of the switching power supply is calculated;

[0063] S2. The switching power supply formulates and switches the switching power supply control according to the voltage gain, and performs first-stage voltage stabilization output, the output voltage amplitude being Vref+Vδ;

[0064] S3. The linear power supply performs second-stage voltage stabilization and filtering, the output voltage amplitude being Vref;

[0065] S4. The series full-bridge inverter circuit performs inverter multi-level conversion according to the output voltage waveform, and realizes DC, impulse, fast edge, square wave, trapezoidal wave and other outputs.

[0066] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, without departing from the technical principles of the present application, a number of improvements and modifications can be made, and these improvements and modifications should also be considered as falling within the protection scope of the present application.

Claims

1. A control method for testing a power supply, characterized in that: The test power supply includes an LLC full-bridge resonant circuit, the output end of the LLC full-bridge resonant circuit is connected to a plurality of full-bridge rectifier circuits connected in parallel, the output end of each full-bridge rectifier circuit is connected in sequence to a linear filter circuit and a full-bridge inverter circuit, and the output ends of all full-bridge inverter circuits are connected in series to form an output; wherein the LLC full-bridge resonant circuit and each rectifier circuit constitute a switching power supply, and each linear filter circuit is a linear power supply; The method comprises: Use closed-loop feedback control to control any one switching power supply, and use open-loop control to control the remaining switching power supplies; Adopt closed-loop feedback control method to control the linear power supply of each channel; The above adopts closed-loop feedback control method to control any switching power supply, including: Based on the target value A of the output voltage of the same linear power supply and the preset voltage deviation, the target value B of the output voltage of the switching power supply is determined; based on the actual output voltage of the switching power supply and the target value B, a control signal of the switching power supply is generated; wherein, the control signal of the switching power supply is used to control the switching power supply to use the target value B as the output target; the method for generating the control signal of the switching power supply is determined according to the voltage gain between the input and output of the switching power supply; as the voltage gain increases, the intermittent control method, the PWM pulse width control method and the PFM frequency control method are used in turn to generate the control signal of the switching power supply; the PFM frequency control method is a fixed 50% duty cycle and switching frequency adjustment.

2. The method according to claim 1, characterized in that Adopt closed-loop feedback control to control each linear power supply, including: Determine the target value A of each linear power supply output voltage based on the preset total output voltage of the test power supply and the allocation rule, wherein the allocation rule defines the proportion of each linear power supply output voltage in the total output voltage; For each linear power supply, a control signal of the linear power supply is generated according to the actual output voltage of the linear power supply and the target value A; wherein the control signal of the linear power supply is used to control the linear power supply to use the target value A as the output target.

3. The method according to claim 2, characterized in that Generate the control signal of the linear power supply according to the actual output voltage and target value of the linear power supply, including: The difference between the actual output voltage of the linear power supply and the target value is calculated, and the difference is amplified and used as the control signal of the linear power supply.

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