Test power supply and control method thereof

Abstract

The invention discloses a test power supply and a control method thereof, and the power supply comprises an LLC full-bridge resonant circuit, the output end of the LLC full-bridge resonant circuit is connected with a plurality of full-bridge rectification circuits which are connected in parallel, and the output end of each full-bridge rectification circuit is sequentially connected with a linear filter circuit and a full-bridge inverter circuit. The output ends of all the full-bridge inverter circuits are connected in series to form output, the LLC full-bridge resonant circuit and each rectifying circuit form a switching power supply, and each linear filter circuit is a linear power supply. The LLC full-bridge resonant circuit and the rectifying circuit form a switching power supply, and the linear filter circuit is a linear power supply, so that a switching power supply and linear power supply combined output mode is realized, the advantages of wide voltage regulation range of the switching power supply and high dynamic response of the linear power supply are combined, and the amplitude precision of output voltage and dynamic load response capability are improved; and the voltage ripple is reduced.

Description

Technical Field

[0001] The invention relates to a test power supply and a control method thereof, belonging to the technical field of test power supplies. Background Art

[0002] High-voltage test power supplies have been widely used in the testing field. When the equipment is subjected to performance testing and aging testing, the test power supply needs to provide various forms of voltage and current waveforms, and the stability and accuracy of the power supply must be ensured to the greatest extent. In the testing scenarios of some precision instruments and electronic devices, the power supply needs to output high-amplitude and high-precision voltages, and at the same time requires a certain load stability capability. However, the existing high-voltage test power supplies are subject to limitations such as device withstand voltage, and most of them use resonant voltage doubler rectifier circuits to output high-voltage DC voltages, which have problems such as large output voltage ripple and low voltage amplitude accuracy. Summary of the invention

[0003] The invention provides a test power supply and a control method thereof, which solve the problems disclosed in the background technology.

[0004] According to one aspect of the present disclosure, a test power supply is provided, including an LLC full-bridge resonant circuit, wherein 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.

[0005] In some embodiments of the present disclosure, 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 disclosure, a support capacitor is connected in parallel to the output end of the full-bridge rectifier circuit.

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

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

[0009] According to another aspect of the present disclosure, a control method for testing a power supply is provided, comprising: Adopt closed-loop feedback control to control any one switching power supply, and adopt open-loop control to control the remaining switching power supplies; A closed-loop feedback control method is used to control the linear power supply of each channel.

[0010] In some embodiments of the present disclosure, a closed-loop feedback control method is used to control each linear power supply, including: According to the preset total output voltage of the test power supply and the allocation rule, the target value A of the output voltage of each linear power supply is determined; wherein the allocation rule defines the proportion of the output voltage of each linear power supply 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.

[0011] In some embodiments of the present disclosure, generating a control signal of the linear power supply according to the actual output voltage and the target value of the linear power supply includes: 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.

[0012] In some embodiments of the present disclosure, a closed-loop feedback control method is used to control any switching power supply, including: Determine a target value B of the output voltage of the switching power supply according to a target value A of the output voltage of the same linear power supply and a preset voltage deviation; A control signal of the switching power supply is generated according to the actual output voltage of the switching power supply and the target value B; 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.

[0013] In some embodiments of the present disclosure, a method for generating a control signal for a switching power supply is determined based on a voltage gain between an input and an output of the switching power supply; as the voltage gain increases, an intermittent control method, a PWM pulse width control method, and a PMF frequency control method are sequentially used to generate a control signal for the switching power supply.

[0014] The beneficial effects achieved by the present invention are as follows: 1. The LLC full-bridge resonant circuit and the rectifier circuit of the present invention constitute a switching power supply, and the linear filter circuit is a linear power supply, realizing a switching power supply + linear power supply combined output mode, combining the advantages of a wide voltage regulation range of the switching power supply and a high dynamic response of the linear power supply, improving the output voltage amplitude accuracy and dynamic load response capability, and reducing voltage ripple; 2. The switching power supply proposed by the present invention adopts the superposition of multiple control methods, obtains a DC voltage gain according to the input voltage and output voltage of the switching power supply, and converts the control method according to the process of voltage gain from low to high, which are intermittent control method, PWM pulse width control method and PMF frequency control method in turn, so as to adapt to a wider voltage output range and a wider voltage gain adjustment; 3. 1. Any one of the switching power supplies of the present invention adopts closed-loop feedback control, and the other switching power supplies adopt open-loop control. A linear power supply is used for voltage stabilization output to solve the problem of cross-regulation rate of secondary voltage of multi-winding transformer. At the same time, the switching power supply + linear power supply only provides a stable DC voltage for the rear-stage full-bridge inverter circuit, realizing the decoupling control of the front and rear stages; 2. The output ends of all the full-bridge inverter circuits of the present invention are connected in series to form an output. The output high-voltage multi-level can be composed of multiple independent levels superimposed. Each full-bridge inverter circuit can adjust the width and frequency of the level by changing the conduction time and direction of the switch tube. After the output is connected in series, the demand for high voltage output of the switch tube with lower withstand voltage is realized, and high-amplitude DC, impact, fast edge, square wave, trapezoidal wave and other voltage waveforms can be output through digital settings. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 To test the principle block diagram of the power supply; Figure 2 Circuit diagram for testing power supply; Figure 3 This is the topological structure diagram of the subsequent output; Figure 4 To test the control schematic diagram of the power supply; Figure 5 Control flow chart for testing power supply. DETAILED DESCRIPTION

[0016] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. It is obvious that the described embodiments are only part of the embodiments of the present disclosure, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present disclosure and its application or use. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present disclosure.

[0017] Unless otherwise specified, the relative arrangement of components and steps, the numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present disclosure.

[0018] At the same time, it should be understood that for the convenience of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship.

[0019] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered as part of the specification.

[0020] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0021] It should be noted that similar symbols and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it does not require further discussion in subsequent figures.

[0022] In order to solve the problems existing in the existing test power supply, the present invention proposes a test power supply and a control method thereof, which realizes the combined output mode of switching power supply + linear power supply in structure, and forms a high voltage output after superposition of several independent levels, and adopts closed-loop feedback control for any one switching power supply in control, and open-loop control for the other switching power supplies. The test power supply disclosed in the present invention can output waveforms such as high voltage DC, impulse, fast edge, square wave, trapezoidal wave, etc., and can ensure the dynamic characteristics and steady-state characteristics of the system, and can realize the working requirements of digital adjustment of output voltage in a wide range, ultra-low output voltage ripple, and fast response with dynamic load.

[0023] See also Figure 1 , is an embodiment of the test power supply disclosed in the present invention. The test power supply in the figure adopts a three-stage cascade scheme, specifically including an LLC full-bridge resonant circuit at the front stage, a full-bridge rectifier circuit and a linear filter circuit at the middle stage, and a full-bridge inverter circuit at the rear stage. The output end of the LLC full-bridge resonant circuit is connected to a plurality of full-bridge rectifier circuits connected in parallel, and 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 a multi-level 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.

[0024] It should be noted that the LLC full-bridge resonant circuit is an existing circuit, which is a circuit that uses the resonance principle to improve the efficiency and power density of the converter. Its working principle is based on the resonant converter, and efficient energy conversion is achieved 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 multi-way independent structure, 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 to a full-bridge rectifier circuit.

[0025] See also Figure 2 The LLC full-bridge resonant circuit includes four switch tubes S1~S4, a resonant inductor Lr, a resonant capacitor Cr, and a multi-winding isolation transformer T; wherein the switch tubes S1~S4 are specifically MOS tubes, and the gate serves as the control end of the LLC full-bridge resonant circuit and the switching power supply. The switch tubes S1~S4 form a full-bridge structure, and the input end of the full-bridge structure is connected to the DC 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 to 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 to the input end of the full-bridge rectifier circuit.

[0026] The LLC full-bridge resonant conversion circuit can realize the zero voltage switching (ZVS) of the primary-side switch tube of the multi-winding isolation transformer T, and the zero current switching (ZCS) of the secondary-side of the multi-winding isolation transformer T. Its input DC voltage is turned on and off by four switch tubes S1~S4 to form an AC quantity input into the resonant network composed of the resonant inductor Lr, the resonant capacitor Cr and the multi-winding isolation transformer T. Energy is transmitted in a resonant manner, and the DC gain conversion is realized in the resonant cavity, and finally output through the secondary side of the multi-winding isolation transformer T.

[0027] It should be noted that the independent structure of each channel is consistent. Figure 2 Taking the four paths in the figure 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 in parallel with the support capacitor Cn1. The high-frequency resonant AC voltage output from the secondary side of the multi-winding isolation transformer T is filtered through the full-bridge rectification and the support capacitor Cn1 to form the DC voltage output by the switching power supply, but a certain ripple voltage is superimposed due to the repeated charging and discharging of the switching element.

[0028] See also 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 respectively connected to the positive output end of the full-bridge rectifier circuit and the positive input end of the full-bridge inverter circuit, and the gate of the MOS tube in the linear filter amplifier tube serves as the control end, that is, the control end of the linear power supply. By dynamically adjusting the gate-source voltage of the MOS tube, the MOS tube is made to work in the linear region, and the drain-source impedance is changed with the gate-source voltage to filter out the voltage ripple output by the switching power supply, thereby further improving the DC voltage output accuracy.

[0029] The test power supply realizes a switching power supply + linear power supply combined output mode, combining the advantages of the switching power supply's wide voltage regulation range and the linear power supply's high dynamic response, improving the output voltage amplitude accuracy and dynamic load response capability, and reducing voltage ripple.

[0030] The structure of the full-bridge inverter circuit is similar to the full-bridge structure in the LLC full-bridge resonant circuit, see Figure 2 The full-bridge inverter circuit includes four switch tubes Sn1~Sn4, which form a full-bridge inverter circuit. The input end is connected in parallel to the filter capacitor Cn2, and the output end is connected in series to form an output loop. The filter capacitor Cn2 provides a high-precision and stable DC voltage for the inverter circuit. Through the combination of the on and off of the switch tubes Sn1~Sn4, positive, negative and zero-level waveforms can be generated according to the output requirements of the test power supply.

[0031] The high-voltage multi-level output of the test power supply can be composed of multiple independent levels (i.e. the level of each output). Each full-bridge inverter circuit can adjust the width and frequency of the level by changing the conduction time and direction of the switch tube. After the output is connected in series, the demand for high voltage output of the switch tube with lower withstand voltage is realized, and high-amplitude DC, impact, fast edge, square wave, trapezoidal wave and other voltage waveforms can be output through digital settings.

[0032] In order to achieve accurate and stable output of the above-mentioned test power supply, the present disclosure also discloses a control method for the above-mentioned test power supply. There are mainly three controls in the test power supply, namely, switching power supply control, linear power supply control and full-bridge inverter circuit control.

[0033] The high voltage level output by the test power supply is composed of the superposition of multiple independent levels. Each full-bridge inverter circuit adjusts the width and frequency of the level by changing the conduction time and direction of the switch tubes Sn1~Sn4. After the output is connected in series, the demand for the switch tube with lower withstand voltage to output high voltage is realized. The voltage amplitude range can be -n×Vref to n×Vref, and it can output high-amplitude DC, impact, fast edge, square wave, trapezoidal wave and other voltage waveforms through digital settings; among which, Vref is the target value A of the linear power supply output voltage.

[0034] The control of the full-bridge inverter circuit is a conventional control method, so in this example, it is mainly for switching power supply control and linear power supply control, which can be specifically as follows: 1) Use closed-loop feedback control to control any one switching power supply, and use open-loop control to control the remaining switching power supplies.

[0035] The switching power supply and linear power supply of the front and middle stages are uniformly defined as isolated power supplies, see Figure 3 The output circuit of the test power supply is a series multi-level converter, which connects the output ends of multiple full-bridge inverters in series for output. Since the test power supply uses a multi-winding isolation transformer to complete the primary circuit isolation and power transmission functions, if each switching power supply is controlled separately, there will inevitably be a problem of cross-regulation rate of the multi-winding isolation transformer. Therefore, due to the sampling limit of the secondary side voltage of the multi-winding isolation transformer and the sampling limit of the multi-level output voltage of the post-stage, one switching power supply voltage is arbitrarily selected for closed-loop feedback control, and the remaining switching power supplies adopt open-loop control mode, using linear power supplies for voltage stabilization output to solve the problem of cross-regulation rate of secondary voltage. At the same time, the isolated power supply only provides a stable DC voltage for the post-stage full-bridge inverter circuit, realizing the decoupling control of the front and rear stages.

[0036] It should be noted that the closed-loop feedback control of the switching power supply is a digital closed-loop feedback control, see Figure 4 , that is, signal loop 1, the specific control process is as follows: 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 output voltage ripple amplitude of the switching power supply to be filtered, generally within tens of volts), determine the target value B of the output voltage of the switching power supply; wherein, the target value B of the output voltage of the switching power supply can generally be set to Vref+Vδ.

[0037] 12) Generate a control signal of the switching power supply according to the actual output voltage of the switching power supply and the target value B; 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.

[0038] Figure 4 In the figure, V1 is the actual output voltage of the switching power supply. Since the feedback V1 is an analog quantity, V1 needs to be converted into a digital value, that is, converted by ADC. Then, according to Vref+Vδ and the converted V1, a corresponding method is used to obtain the control signal of the switching power supply. The purpose of the control signal of the switching power supply is to make the output voltage of the switching power supply Vref+Vδ.

[0039] It should be noted that the control signal of the switching power supply can be generated by an intermittent control method, a PWM pulse width control method or a PMF frequency control method. The specific method to be used needs to be determined based on the voltage gain between the input and output of the switching power supply.

[0040] The intermittent control method is fixed switching frequency, fixed small duty cycle, and pulse number adjustment within the cycle. The PWM pulse width control method is fixed switching frequency and duty cycle adjustment (the maximum duty cycle is 50%). The PMF frequency control method is fixed 50% duty cycle and switching frequency adjustment. The three methods are used in combination to adapt to a wider voltage variation range of input and output DC voltages.

[0041] The use of specific control strategies is mainly determined based on the DC voltage gain. The DC voltage gain of the switching power supply is obtained based on the input voltage and the output voltage. The control method is switched in order from low to high according to the voltage gain. An intermittent control method is used under low voltage gain conditions. As the voltage gain increases, the number of pulses in the cycle is adjusted under the intermittent control method to adapt to the change in voltage gain until it is adjusted to the set switching point. The method is switched to the PWM pulse width control method. The duty cycle is adjusted under the PWM pulse width control method to adapt to the voltage gain change at this stage. When the set point is reached, the method is switched again to the PFM frequency control method. Under this method, the operating frequency of the LLC full-bridge resonant circuit is adjusted to adapt to the remaining voltage gain range to achieve the target voltage output of the switching power supply.

[0042] 2) Use closed-loop feedback control to control each linear power supply.

[0043] 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: 21) According to the preset total output voltage of the test power supply (i.e. Figure 2 Vout in ) and the allocation rule are used to determine the target value A of the output voltage of each linear power supply; wherein the allocation rule defines the proportion of the output voltage of each linear power supply in the total output voltage.

[0044] Assuming that the total output voltage is n×Vref, if the allocation rule is average allocation, then the target value A of the linear power supply output voltage is recorded as Vref. Of course, according to different allocation rules, it can also be 2Vref, 3Vref, etc., which can be set according to actual conditions.

[0045] 22) 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.

[0046] Figure 4 In the figure, V2 is the actual output voltage of the linear power supply. Since Vref is a digital quantity, Vref needs to be converted from digital to analog, that is, converted through DAC. Then the difference between the actual output voltage of the linear power supply and the target value can be further calculated. The difference is amplified by an operational amplifier as the control signal of the linear power supply. The purpose of the control signal of the linear power supply is to make the output voltage of the linear power supply Vref.

[0047] See also Figure 5 , the specific control method of the test power supply can be as follows: 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; S2, the switching power supply is formulated and switched according to the voltage gain to control the switching power supply, and the first-level voltage stabilization output is performed, and the output voltage amplitude is Vref+Vδ; S3, the linear power supply performs the second stage voltage stabilization and filtering, and the output voltage amplitude is Vref; S4, the series full-bridge inverter circuit performs inverter multi-level conversion according to the output voltage waveform to achieve DC, impulse, fast edge, square wave, trapezoidal wave and other outputs.

[0048] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A test power supply, characterized in that: It 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 to a linear filter circuit and a full-bridge inverter circuit in sequence, 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.

2. The test power supply according to claim 1, characterized in that: 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.

3. The test power supply according to claim 1, characterized in that: The output end of the full-bridge rectifier circuit is connected in parallel with a supporting capacitor.

4. The test power supply according to claim 1, characterized in that: The linear filter circuit is a linear filter amplifier tube.

5. The test power supply according to claim 1, characterized in that: The input end of the full-bridge inverter circuit is connected in parallel with a filter capacitor.

6. A control method for testing a power supply, characterized in that: The test power supply is the test power supply according to any one of claims 1 to 5, and the method comprises: Adopt closed-loop feedback control to control any one switching power supply, and adopt open-loop control to control the remaining switching power supplies; A closed-loop feedback control method is used to control the linear power supply of each channel.

7. The method according to claim 6, characterized in that Adopt closed-loop feedback control to control each linear power supply, including: According to the preset total output voltage of the test power supply and the allocation rule, the target value A of the output voltage of each linear power supply is determined; wherein the allocation rule defines the proportion of the output voltage of each linear power supply 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.

8. The method according to claim 7, characterized in that According to the actual output voltage and target value of the linear power supply, a control signal of the linear power supply is generated, 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.

9. The method according to claim 6, characterized in that Adopt closed-loop feedback control to control any switching power supply, including: Determine a target value B of the output voltage of the switching power supply according to a target value A of the output voltage of the same linear power supply and a preset voltage deviation; A control signal of the switching power supply is generated according to the actual output voltage of the switching power supply and the target value B; 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.

10. The method according to claim 9, characterized in that The method of 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 PMF frequency control method are used in turn to generate the control signal of the switching power supply.

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