All-digital control switching power supply

Abstract

The invention discloses an all-digital control switching power supply, and belongs to the technical field of switching power supplies. The switching power supply comprises a main power circuit, a control circuit and an auxiliary power supply circuit. The main power circuit comprises an EMI filter circuit, a full-bridge rectification circuit, a PFC circuit and a full-bridge LLC circuit. The PFC circuit comprises a PFC main power circuit, a bias voltage circuit and an MOS current sampling circuit. The PFC main power circuit comprises a rectifier bridge and a BOOST circuit; the bias voltage circuit adopts two resistors to perform voltage division to obtain bias voltage, and the bias voltage is subjected to noise reduction through an operational amplifier; the MOS current sampling circuit is used for sampling the current of an MOS tube by using a sampling resistor, the differential amplification circuit is used for carrying out differential amplification on the voltage of the sampling resistor, and the amplified voltage passes through the RC filter circuit to obtain an output voltage. By directly measuring the MOS tube current of the PFC circuit, the problem that the inductive current cannot be directly measured and needs an additional sensor for indirect measurement is solved, full-digital control is adopted, and the dynamic response is rapid.

Description

Technical Field

[0001] The present invention belongs to the technical field of switching power supplies, and specifically relates to a switching power supply with all-digital control. Background Art

[0002] With the rapid development of power electronics technology, switching power supplies are widely used in industrial, communication, and consumer electronics fields due to their advantages such as high efficiency and high power density. As a key module at the front end of a switching power supply, the power factor correction (PFC) circuit directly affects the power quality of the power grid and the energy efficiency of the system. Traditional analog-controlled PFC circuits are implemented using dedicated control chips (such as UC3854). Although they have the characteristic of fast response speed, in practical applications, the inductor current cannot be directly measured and requires additional sensors for indirect measurement, which increases additional costs and circuit losses, and the measurement accuracy of the current is not high.

[0003] For the control of switching power supplies, traditional methods mainly use relatively mature analog control technologies, which can ensure the stability of output parameters to a certain extent, but there are also some problems. First, during the power supply debugging stage, analog adjustment circuits often need to replace analog devices; second, the consistency of device parameters cannot be guaranteed, and some analog computing devices are easily affected by environmental factors such as temperature and humidity; third, some advanced control algorithms cannot be implemented. With the development of industrial technology, the performance requirements for power supply systems of power supply equipment are also continuously increasing, and higher requirements are placed on the efficiency, stability, and intelligence of switching power supplies. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the technical problem to be solved by the present invention is to provide a switching power supply with all-digital control. It overcomes the shortcomings of the traditional technology for the control method of the PFC circuit, solves the problem that the inductor current cannot be directly measured in practical applications and requires additional sensors for indirect measurement, directly measures the MOS tube current of the PFC circuit, reduces the measurement difficulty and cost, and can improve the power factor of the power supply and reduce the total input current harmonics. The entire power supply adopts all-digital control and has the advantages of rapid dynamic response, complete protection functions, and higher working stability.

[0005] The present invention adopts the following technical solutions to solve the above technical problems:

[0006] A fully digital controlled switching power supply includes a main power circuit, a control circuit and an auxiliary power supply circuit; the main power circuit includes an EMI filter circuit, a full-bridge rectifier circuit, a PFC circuit and a full-bridge LLC circuit; the PFC circuit includes a PFC main power circuit, a bias voltage circuit and a MOS current sampling circuit; the PFC main power circuit includes a rectifier bridge and a BOOST boost circuit; the bias voltage circuit uses two resistors to divide the voltage to obtain a bias voltage, and the bias voltage is denoised by an operational amplifier; the MOS current sampling circuit uses a sampling resistor to sample the MOS tube current, and a differential amplifier circuit is used to differentially amplify the voltage of the sampling resistor, and the amplified voltage passes through an RC filter circuit to obtain an output voltage.

[0007] Further, the control circuit includes a PFC control circuit and an LLC control circuit. The PFC control circuit controls the PFC circuit, and the LLC control circuit controls the full-bridge LLC circuit; the PFC control circuit includes a processing chip, a controller, a voltage and current detection circuit and an isolation drive circuit; the voltage and current detection circuit is used to detect the input voltage, MOS tube current and output voltage. The processing chip processes the signals detected by the voltage and current detection circuit to make the controller output a PWM signal, and the PWM signal drives the isolation drive circuit to control the MOS tube of the PFC circuit; the LLC control circuit includes a processing chip, a controller, a voltage and current detection circuit and an isolation drive circuit. The voltage and current detection circuit is used to detect the output voltage and output current. The processing chip processes the signals detected by the voltage and current detection circuit to make the controller output a PWM signal, and the PWM signal drives the isolation drive circuit to control the four MOS tubes of the full-bridge LLC circuit.

[0008] Further, in the main power circuit, the input current is filtered by the EMI filter circuit, the filtered current is rectified by the full-bridge rectifier circuit, the rectified current is corrected by the PFC circuit, and the corrected current undergoes inversion and secondary rectification in the full-bridge LLC circuit to make the output voltage reach the set value.

[0009] Compared with the prior art, the beneficial effects of the present invention are:

[0010] First, by sampling the MOS current instead of the inductor current, it solves the disadvantages that the inductor current needs to be sampled by a sensor and the inductor current sampling is inaccurate, improves the current sampling accuracy and the sampling is relatively easy, can obtain a higher power factor, lower harmonic distortion, and reduces the impact on the power grid.

[0011] Second, the present invention adopts a modular design, and the power supply adopts fully digital control, reducing the influence of the parameter drift of analog devices on the power supply, achieving a high power factor, high efficiency and rapid dynamic response, and the later maintenance is also relatively simple. Description of the Drawings

[0012] Figure 1 It is the structural diagram of the switching power supply;

[0013] Figure 2 It is the structural diagram of the PFC circuit;

[0014] Figure 3 It is the working state conversion diagram of the switching power supply;

[0015] Figure 4 It is the control framework diagram of the PFC circuit;

[0016] Figure 5 It is the input AC source display interface;

[0017] Figure 6 It is the input voltage and input current waveforms;

[0018] Figure 7 It is the output voltage waveform when the rated load suddenly drops to no load. Detailed Embodiment

[0019] The following provides specific embodiments in conjunction with the drawings. The specific embodiments are only used to introduce the technical solutions of the present invention in detail and do not limit the protection scope of this application.

[0020] The present invention provides a switching power supply with all-digital control, including a main power circuit, a control circuit, and an auxiliary power supply circuit; the main power circuit serves as the main circuit for energy conversion from input to output, the control circuit is used to control the PFC circuit and the full-bridge LLC circuit of the main power circuit, and the auxiliary power supply circuit supplies power to the remaining circuits.

[0021] The main power circuit includes an EMI filter circuit, a full-bridge rectifier circuit, a PFC circuit, and a full-bridge LLC circuit; the input current passes through the EMI filter circuit to filter out differential-mode and common-mode interferences on the grid side; the filtered current is rectified by the full-bridge rectifier circuit, and the rectified current is corrected by the PFC circuit to ensure that the input current does not distort, and the bus voltage output by the PFC circuit is stabilized at about 380V to supply power to the full-bridge LLC circuit; the corrected current is inverted and secondarily rectified in the full-bridge LLC circuit and then output, and the output voltage reaches the set value to complete efficient energy conversion.

[0022] The EMI filter circuit includes a fuse, an X capacitor, a Y capacitor, a common-mode inductor, and an NTC thermistor; the fuse is a fast-blowing fuse. When the current increases to the set value, the fuse melts and disconnects from the subsequent circuit to prevent further expansion of circuit faults; the X capacitor, Y capacitor, and common-mode inductor are used to suppress the differential-mode or common-mode interference on the grid side from entering the power supply, or the differential-mode or common-mode interference of the power supply from entering the grid; the NTC thermistor is a resistor with a negative temperature coefficient to prevent the impact of large current on the power supply during cold start of the power supply.

[0023] The PFC circuit includes a PFC main power circuit, a bias voltage circuit, and a MOS current sampling circuit; the input of the rectifier bridge of the PFC main power circuit is the output after the alternating current passes through the EMI circuit to filter out interference. The rectifier bridge selects the GBU810 with a breakdown voltage of 800V and a rectified current of 8A according to the circuit parameters; after passing through the rectifier bridge, it enters the BOOST boost circuit. The BOOST boost circuit consists of a boost inductor L, a MOS transistor Q1, a MOS transistor current sampling resistor, a diode D2, and bus capacitors C1 and C2. The boost inductor L is 1.2mH. The gate G of the MOS transistor is connected to the control signal PWM_PFC, and the control signal is provided by the control circuit to control the on and off of the MOS transistor to adjust the output voltage of the BOOST boost circuit. The source S of the MOS transistor is connected to a high-precision sampling resistor RS of 10mΩ / 0.1% to sample the MOS transistor current to obtain a sampling voltage, avoiding the problem of difficult sampling of the inductor current. The diode D2 is a diode with a rated current of 20A and a breakdown voltage of 800V, and the bus capacitors are two 100uF / 1kV capacitors, so as to output a stable bus voltage to stably supply power to the subsequent full-bridge LLC circuit; the bias voltage circuit uses resistors R1 and R2 to divide the 5V voltage to obtain a bias voltage. The bias voltage passes through a voltage follower composed of an operational amplifier U1A for noise reduction, thus avoiding the zero-offset of the operational amplifier and the distortion problem caused by small current conversion, improving the accuracy and stability of the operational amplifier, and ensuring more accurate and stable MOS current acquisition; the MOS current sampling circuit samples the current of the MOS transistor using the sampling resistor RS, and uses a differential amplifier circuit to differentially amplify the voltage of the sampling resistor RS. The amplified voltage passes through an RC filter circuit composed of a resistor R7 and a capacitor C5 to obtain an output voltage; the output voltage is sent to the DSP for subsequent arithmetic control to ensure a high power factor. Using the sampling resistor to sample the current of the MOS transistor instead of sampling the inductor current solves the problem of difficult sampling of the inductor current and the need for an additional sensor during the control of the PFC circuit in traditional switching power supplies, and reduces costs and circuit losses and reduces the control difficulty.

[0024] The full-bridge LLC circuit includes four full-bridge MOS transistors S1 to S4, a resonant inductor Lr, a transformer Tr, and diodes D2 and D3; the bus voltage output by the PFC circuit is inverted and rectified twice to output a voltage of a set magnitude.

[0025] The control circuit includes a PFC control circuit and an LLC control circuit, which independently control the PFC circuit and the full-bridge LLC circuit respectively using TMS320F28034 chips. Isolated communication is set between the two chips to ensure that they do not interfere with each other and can know the working status of each other; two digital signal processing chips TMS320F28034 independently control the PFC circuit and the full-bridge LLC circuit respectively, replacing the traditional analog control, avoiding the problems of inconsistent parameters and parameter drift of analog devices, and achieving more precise control and faster dynamic response.

[0026] The PFC control circuit is equipped with a voltage and current detection circuit, which can collect signals such as input voltage, MOS transistor current, and output voltage into the control chip and convert them into voltage signals that the control chip can recognize. Through a control algorithm, it is output to the isolated drive circuit through the PWM of the controller, and the MOS transistors of the PFC circuit are controlled through the isolated drive circuit.

[0027] The LLC control circuit is also equipped with a voltage and current detection circuit, which collects signals such as output voltage and output current into the chip and converts them into voltage signals that the controller can recognize. And through a double-loop control algorithm, it is output to the isolated drive circuit through the PWM of the controller, and the four MOS transistors of the full-bridge LLC circuit are controlled through the isolated drive circuit. At the same time, it will also judge the power supply status according to the collected signals and indicate it through the working status indication module.

[0028] Although the PFC control circuit and the LLC control circuit work independently, necessary data transmission is required between them to ensure that the working status of the two circuits can be known to each other, or to prohibit the full-bridge LLC circuit from starting when the PFC circuit fails, etc. Therefore, an isolated communication circuit is used to enable data transmission between the PFC controller and the full-bridge LLC controller. The power supply adopts all-digital control, greatly reducing the number of devices and avoiding problems such as inconsistent parameters and temperature drift of analog devices. The high power factor, low total harmonic distortion, and high efficiency of the switching power supply are achieved. The power supply status is set to a total of five working states: initialization state, waiting state, startup state, normal operation state, and fault state. See Figure 3 。

[0029] The auxiliary power supply circuit obtains voltage from the bus voltage output by the PFC circuit and converts it into the voltage corresponding to the corresponding circuit, and then supplies power to the control circuit, voltage and current detection circuit, isolated drive circuit, and communication circuit, etc.

[0030] For the software design of the PFC circuit, in order to increase the portability of the software system, the overall PFC software system is designed based on the idea of interrupt event triggering. The architecture diagram of the system is as shown in Figure 4 ; The software main body consists of four interrupt contents, namely ADC interrupt, 1KHz interrupt, 200Hz interrupt, and communication interrupt. Their priority order from high to low is as shown in Figure 4 ; During the operation of each interrupt, the interrupt nesting function is used. An interrupt with a higher priority can interrupt an interrupt with a lower priority at any time, and each interrupt has its corresponding processing event content.

[0031] The parameters of the present invention are tested. The prototype of the present invention is a power supply with an input of 220V / 50Hz and an output of 24V / 5A. Its power factor (PF), input voltage and current waveforms, efficiency, and dynamic response are tested. The test results are as follows:

[0032] Figure 5 For the input AC source interface information, the input voltage is 220V, the input current is 0.602A, the input power is 130.1W, the frequency is 50Hz, and the power factor (PF) is 0.982; Figure 6 For the waveforms of the input voltage and input current, Channel 1 is the input voltage waveform and Channel 2 is the input current waveform. From Figure 5 and Figure 6 The test results, it can be seen that the PFC circuit and its control method of the present invention have achieved good effects. The power factor (PF) is as high as 0.982, the phase of the input current waveform is basically the same as that of the input voltage waveform, and the distortion of the input current waveform is very small, indicating that the control method of the PFC circuit of the present invention for MOS current sampling has achieved the expected effect.

[0033] Figure 7 For the output voltage waveform when the power supply load suddenly drops from the rated load to no load, from Figure 7 it can be seen that the output voltage fluctuation is very small and the duration is extremely short, indicating that the output voltage of the power supply of the present invention is stable and the dynamic response is rapid. Figure 7 It can be seen from that when the rated load is 5A, the output voltage is 24V, Figure 5 the input power is the input power under the rated load, which is 130.1W. The efficiency can be calculated as 92.24%. It can be seen that the all-digital control method of the present invention has achieved good effects, with a rapid dynamic response and a full-load efficiency of over 92%, realizing efficient energy conversion.

[0034] Matters not described in the present invention are applicable to the prior art.

Claims

1. A fully digital controlled switching power supply, comprising a main power circuit, a control circuit and an auxiliary power supply circuit; the main power circuit includes an EMI filtering circuit, a full-bridge rectifier circuit, a PFC circuit and a full-bridge LLC circuit; characterized in that, The PFC circuit includes a PFC main power circuit, a bias voltage circuit, and a MOS current sampling circuit; the PFC main power circuit includes a rectifier bridge and a BOOST boost circuit; the bias voltage circuit uses two resistors to divide the voltage to obtain a bias voltage, and the bias voltage is denoised through an operational amplifier; The MOS current sampling circuit samples the MOS tube current using a sampling resistor, and uses a differential amplifier circuit to differentially amplify the voltage of the sampling resistor. The amplified voltage passes through an RC filter circuit to obtain an output voltage.

2. The switched-mode power supply with all-digital control according to claim 1, wherein The control circuit includes a PFC control circuit and an LLC control circuit. The PFC control circuit controls the PFC circuit, and the LLC control circuit controls the full-bridge LLC circuit; the PFC control circuit includes a processing chip, a controller, a voltage and current detection circuit, and an isolation drive circuit; the voltage and current detection circuit is used to detect the input voltage, MOS tube current, and output voltage. The processing chip processes the signals detected by the voltage and current detection circuit, enabling the controller to output a PWM signal, and the PWM signal drives the isolation drive circuit to control the MOS tube of the PFC circuit; the LLC control circuit includes a processing chip, a controller, a voltage and current detection circuit, and an isolation drive circuit. The voltage and current detection circuit is used to detect the output voltage and output current. The processing chip processes the signals detected by the voltage and current detection circuit, enabling the controller to output a PWM signal, and the PWM signal drives the isolation drive circuit to control the four MOS tubes of the full-bridge LLC circuit.

3. The switched-mode power supply with all-digital control according to claim 1, characterized in that, In the main power circuit, the input current is filtered by the EMI filter circuit, the filtered current is rectified by the full-bridge rectifier circuit, the rectified current is corrected by the PFC circuit, and the corrected current undergoes inversion and secondary rectification in the full-bridge LLC circuit to make the output voltage reach the set value.

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