A cascade current-limiting loop control method and device

Abstract

The application relates to a cascade current-limiting loop control method and device. A direct-current converter collects output voltage and output current and sends the same to a controller, the controller performs loop calculation on the sampling signals, compares the current-limiting loop calculation result with an initial set value of the output voltage, assigns the comparison result to an output voltage reference value, and then performs output slow-start boosting, the controller synchronously completes voltage inner loop and current outer loop closed-loop control, and guarantees the stability of the output voltage. When overcurrent or short circuit occurs in the load, the application executes the current-limiting loop and the main control loop (voltage inner loop and current outer loop) in cascade, so that the direct-current conversion timely responds to abnormal working conditions of the load current, and protects the power supply product from being damaged. According to the control method provided by the application, the output overcurrent and output short circuit occurring when the direct-current converter starts can be effectively controlled, and the converter can work in current-limiting mode or be protected from being damaged when the output is current-limited or short-circuited.

Description

Technical Field

[0001] This invention relates to the field of DC / DC converter power supply technology, specifically to a cascaded current limiting loop control method and device. Background Technology

[0002] As the power density of power supply products continues to increase, the output current of power supply products is becoming increasingly larger in order to meet user needs. If the power supply product cannot perform current limiting or short circuit protection in time under output overcurrent or output short circuit conditions, it will cause irreversible damage to downstream loads. Therefore, the high-current output current limiting and short circuit protection functions of power supply products are becoming increasingly important.

[0003] The current-limiting function of power supply products is mainly achieved by changing the reference value of the output voltage when the output current exceeds the current limit, thereby reducing the output voltage and ensuring that the output power does not exceed the rated output power. Traditional current limiting is generally implemented using hardware circuits. However, due to the current requirements for the localization of power supply products, it is difficult to find domestic alternatives to imported control components. Therefore, digital control effectively compensates for this deficiency. Using digital control methods can save on the number of components and improve product space utilization. In addition, digital controllers generally implement current limiting by collecting the output current value, comparing it with the reference value, calculating a new output voltage reference value, and then changing the output voltage. This method is simple to implement, but it is limited by the control precision of digital control and cannot achieve real-time adjustment of the output voltage. There is a certain delay, which can lead to control failure and the inability to achieve output current limiting and short-circuit protection functions.

[0004] Therefore, there is an urgent need to realize a cascaded current-limiting loop control method and device. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a cascaded current-limiting loop control method and apparatus.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A cascaded current-limiting loop control method, comprising the following steps:

[0008] S1. After the controller system is initialized, the AD sampling interrupt program is executed to sample the input voltage signal, output voltage signal, output current signal, operating environment temperature signal and hardware protection signal.

[0009] S2. The sampled signal is conditioned using a filtering algorithm. Based on the conditioned sampled signal, it is determined whether the power supply product has malfunctioned. The malfunctions include input overvoltage, input undervoltage, output overvoltage, output overcurrent, output short circuit, overtemperature, or hardware protection. If the power supply product malfunctions, the controller shuts down the PWM drive signal after detecting the fault signal, thereby shutting down the power supply product. If the power supply product malfunction disappears or no fault occurs, the controller enters the current limiting loop adjustment, performs current limiting loop PID loop calculation, and enters the output soft start control program. After the soft start is completed, voltage loop PID control and current loop PID control are then performed.

[0010] S3. When the load experiences overcurrent or short circuit, the controller collects the output current signal and inputs it into the current limiting loop for PID calculation. The controller then outputs a control signal as the input to the voltage loop, which performs PID control and outputs the control signal as the input to the current loop. The current loop then performs PID control and outputs the control signal as the input to the PWM module. The PWM module outputs a PWM drive signal and adjusts the width of the PWM drive signal output by the controller in real time to control the turn-on time of the power switching transistor and protect the power supply product.

[0011] As a further improvement to the above technical solution, the current-limiting loop PID loop calculation in steps S2 and S3 includes:

[0012] The reference setpoint Io_ref and the output current sample value Io_samp of the current limiting loop are used as the input of the current limiting loop. After the two are processed by the current limiting loop PID calculation, the current limiting loop PID loop calculation value Vo_cal is obtained.

[0013] The calculated value Vo_cal of the current limiting loop is compared with the initial set value Vo_target of the output voltage, and the comparison result is used as the reference value Vo_set of the output voltage.

[0014] As a further improvement to the above technical solution, the voltage loop PID control in steps S2 and S3 includes:

[0015] The output voltage reference value Vo_set and the output voltage sample value Vo_samp are used as inputs to the voltage loop. After being processed by the voltage loop PID, the voltage loop calculation output value Io_cal is obtained, which is used as the output of the voltage loop calculation.

[0016] As a further improvement to the above technical solution, the current loop PID control in steps S2 and S3 includes:

[0017] The voltage loop calculation output value Io_cal and the output current sampling value Io_samp are used as inputs to the current loop, and the result obtained after the current loop PID calculation is used as the output of the current loop calculation.

[0018] As a further improvement to the above technical solution, the PWM drive signal output in step S2 or the PWM module outputting the PWM drive signal in step S3 includes:

[0019] The output of the current loop calculation is used as the input of the PWM module. After converting the input signal, the PWM module outputs six PWM drive signals: PWMA, PWMB, PWMC, PWMD, PWME, and PWMF. The PWMA, PWMB, PWMC, and PWMD drive signals are used to drive the four main power transistors of the primary-side full-bridge circuit, respectively. The PWME and PWMF drive signals are used to drive the four power transistors of the secondary-side synchronous rectifier circuit.

[0020] The present invention also includes a cascaded current-limiting loop control device for implementing the above control method.

[0021] The control device includes: an input filter circuit, an input voltage sampling circuit, a power conversion circuit, a drive circuit, an output backflow prevention circuit, an operating temperature sampling circuit, a hardware protection sampling circuit, an output current sampling circuit, an output voltage sampling circuit, an output filter circuit, and a controller.

[0022] The output terminal of the input filter circuit is connected to the input terminal of the power conversion circuit; the output terminal of the power conversion circuit is connected to the input terminal of the output backflow prevention circuit and the input terminal of the output current sampling circuit, respectively; the output terminal of the output backflow prevention circuit is connected to the input terminal of the output filter circuit and the input terminal of the output voltage sampling circuit, respectively; the output terminals of the input voltage sampling circuit, the output current sampling circuit, the output voltage sampling circuit, the operating temperature sampling circuit, and the hardware protection sampling circuit are all connected to the input terminal of the controller; the output terminal of the controller is connected to the input terminal of the drive circuit, and the output terminal of the drive circuit is connected to the input terminal of the power conversion circuit.

[0023] The controller is used to implement output voltage loop control, output current loop control and output current limiting loop control, and at the same time perform input voltage detection, output voltage detection, output current detection, temperature detection and hardware protection detection.

[0024] The controller acquires the input voltage signal collected by the input voltage sampling circuit and compares the acquired input voltage signal with the set value to determine whether the input voltage is working within the normal input voltage range. If it exceeds the upper limit of the normal input voltage, the input overvoltage protection program is executed, and the controller waits for the input voltage to recover to the normal operating voltage. If it is lower than the lower limit of the normal input voltage, the controller executes the input undervoltage protection program, and the controller waits for the input voltage to recover to the normal operating voltage.

[0025] The controller collects the ambient temperature signal from the operating temperature sampling circuit and compares the collected temperature signal with the set value to determine whether the power supply product is operating within the normal temperature range. If it exceeds the upper limit of the normal operating temperature, the over-temperature protection program is executed, and the system waits for the temperature signal to return to the normal operating temperature. If it is below the lower limit of the normal operating temperature, the over-temperature protection program is executed, and the system waits for the temperature signal to return to the normal operating temperature.

[0026] The controller collects the hardware protection signal from the hardware protection sampling circuit and determines whether the power supply product has experienced hardware protection based on the hardware protection signal. If hardware protection occurs, the power supply product's hardware automatic shutdown module output is activated, and the software locks the protection mode and waits for the hardware protection to disappear. When the hardware protection disappears, the software resets the hardware fault signal, and the power supply product resumes operation.

[0027] The controller acquires the output voltage signal collected by the output voltage sampling circuit and compares the acquired output voltage signal with the set value to determine whether the output voltage is working within the normal output voltage range. If it exceeds the upper limit of the normal output voltage, the controller executes the output overvoltage protection program and waits for the output voltage signal to return to the normal operating voltage.

[0028] The controller collects the output current signal from the output current sampling circuit and compares the collected output current signal with the set value to determine whether the power supply product's output current is operating within the normal output current range. If it exceeds the upper limit of the normal operating current, the overcurrent protection program is executed, and the controller waits for the output current signal to return to normal.

[0029] The controller performs current limiting loop, voltage loop and current loop control based on the collected output voltage signal and output current signal, and performs closed-loop control based on the proportional-integral-derivative algorithm, so that the output voltage is within the normal operating voltage range when the load is dynamic and the input voltage is dynamic.

[0030] As a further improvement to the above technical solution, the input filtering circuit is used to filter out high-frequency interference signals in the input voltage.

[0031] The output filter circuit is used to filter out low-frequency jitter on the output bus so as to keep the output voltage smooth and provide a stable output voltage to the load. The output filter circuit includes an output filter inductor and an output filter capacitor.

[0032] The input voltage sampling circuit is used to collect the input voltage signal and send the collected input voltage signal to the controller. The controller determines whether the input voltage is within the normal operating range based on the collected input voltage signal. If the controller determines that an input overvoltage or input undervoltage has occurred based on the collected input voltage signal, the power supply product triggers protection and prohibits the power supply product from outputting.

[0033] The output current sampling circuit is used to collect the output current signal and send the collected output current signal to the controller. The controller performs hardware protection, output overcurrent judgment and controller current inner loop control based on the output current signal.

[0034] The output voltage sampling circuit is used to collect the output voltage signal and send the collected output voltage signal to the controller. The controller performs output overvoltage judgment and controller loop control based on the output voltage signal.

[0035] The operating temperature sampling circuit is used to collect the ambient temperature when the power supply product is working and send the collected ambient temperature to the controller. The controller determines whether the internal temperature of the power supply product is within the reasonable operating temperature range based on the ambient temperature value. If the ambient temperature exceeds its maximum operating temperature, the power supply product over-temperature protection is triggered.

[0036] The hardware protection sampling circuit is used to collect overcurrent and short-circuit protection signals of the power supply product and send the collected overcurrent and short-circuit protection signals of the power supply product to the controller. The controller determines whether the power supply product has a short circuit or output overcurrent based on the signal. If the power supply product has a short circuit or output overcurrent, the controller outputs a hardware protection signal to trigger the hardware protection shutdown module to shut down the module. At the same time, the controller collects the hardware protection status signal. When the hardware protection disappears, the controller resets the hardware protection signal to restore the power supply product to normal operation.

[0037] As a further improvement to the above technical solution, the power conversion circuit is used to realize energy transfer and the conversion of input voltage to output voltage; the power conversion circuit includes a power switching transistor.

[0038] As a further improvement to the above technical solution, the driving circuit is used to condition the control signal sent by the controller through the isolation driving chip, and send the conditioned signal to the power switching transistor in the power conversion circuit. The signal controls the conduction time of the power switching transistor to control the energy transmission time per unit cycle.

[0039] The controller emits a pulse width modulation wave with a specific duty cycle. After being isolated and driven by the driving circuit, the pulse width modulation wave is sent to the power switch in the power conversion circuit to control the turn-on and turn-off time of the power switch.

[0040] The driving circuit includes an isolation driving chip and an input current limiting resistor, with the primary and secondary sides of the isolation driving chip powered separately.

[0041] As a further improvement to the above technical solution, the output anti-backflow circuit is used to prevent energy from flowing back into the main power circuit when the power supply product is turned off, thus damaging the power supply product; the output anti-backflow circuit includes a switching transistor, a driving resistor, a driving chip, and peripheral resistors and capacitors.

[0042] Compared with the prior art, the advantages of the present invention are:

[0043] This invention enables power supply products to synchronously adjust the output voltage loop and output current loop through a cascaded current limiting loop when current limiting or short circuit conditions occur at the load end. This achieves cycle-by-cycle current limiting control, improves the reliability of the power supply products, and prevents untimely protection due to insufficient control precision, thus protecting the power supply products. Attached Figure Description

[0044] Figure 1 This is a system block diagram of the cascaded current-limiting loop control device in this invention;

[0045] Figure 2 This is a control strategy diagram of the cascaded current-limiting loop control method in this invention;

[0046] Figure 3 This is a flowchart illustrating the implementation of the cascaded current-limiting loop control method in this invention.

[0047] in:

[0048] 1. Input filter circuit; 2. Power conversion circuit; 3. Output backflow prevention circuit; 4. Output filter circuit; 5. Drive circuit; 6. Output current sampling circuit; 7. Input voltage sampling circuit; 8. Controller; 9. Output voltage sampling circuit; 10. Operating temperature sampling circuit; 11. Hardware protection sampling circuit. Detailed Implementation

[0049] The present invention will be further described below with reference to the accompanying drawings:

[0050] like Figure 1The cascaded current limiting loop control device shown includes an input filter circuit 1, an input voltage sampling circuit 7, a power conversion circuit 2, a drive circuit 5, an output backflow prevention circuit 3, an operating temperature sampling circuit 10, a hardware protection sampling circuit 11, an output current sampling circuit 6, an output voltage sampling circuit 9, an output filter circuit 4, and a controller 8.

[0051] The output terminal of the input filter circuit 1 is connected to the input terminal of the power conversion circuit 2; the output terminal of the power conversion circuit 2 is connected to the input terminal of the output backflow prevention circuit 3 and the input terminal of the output current sampling circuit 6, respectively; the output terminal of the output backflow prevention circuit 3 is connected to the input terminal of the output filter circuit 4 and the input terminal of the output voltage sampling circuit 9, respectively; the output terminals of the input voltage sampling circuit 7, the output current sampling circuit 6, the output voltage sampling circuit 9, the operating temperature sampling circuit 10, and the hardware protection sampling circuit 11 are all connected to the input terminal of the controller 8. The output terminal of the controller 8 is connected to the input terminal of the drive circuit 5, and the output terminal of the drive circuit 5 is connected to the input terminal of the power conversion circuit 2.

[0052] The input filter circuit 1 is used to filter out high-frequency interference signals in the input voltage. The input filter circuit 1 adopts the mature inductor + capacitor filtering method in the prior art, which can effectively filter out noise components in the input voltage and provide a clean input voltage for the power conversion circuit 2.

[0053] The input voltage sampling circuit 7 is used to acquire the input voltage signal and send it to the controller, providing data for judging input overvoltage and input undervoltage. The controller determines whether the input voltage is within the normal operating range based on the acquired input voltage signal. If the controller determines that input overvoltage or input undervoltage has occurred, the power supply product triggers protection, prohibiting output to protect the product from damage. The input voltage sampling circuit 7 uses resistors for voltage division, then isolates the output through an isolation chip, and finally processes the signal through an operational amplifier before sending it to the sampling port of the controller 8. Software processing is then used to provide data for input overvoltage and undervoltage detection. The operational amplifier doubles the input voltage sampling value, further improving the input voltage sampling accuracy.

[0054] The power conversion circuit 2 is used to realize energy transfer and the conversion of input voltage to output voltage, so as to ensure stable output voltage within the normal input voltage range. The power conversion circuit 2 adopts the mature phase-shifted full-bridge + synchronous rectification control method in the existing technology to convert the input high voltage into the voltage required for output. The sampling on-resistance of the synchronous rectification power tube is extremely small, and it adopts a double-sided heat dissipation package, which can reduce the conduction loss of the synchronous rectification tube and improve the product's operating efficiency.

[0055] The drive circuit 5 is used to send the control signal from the controller 8, after being conditioned by the isolation drive chip in the drive circuit 5, to the power switch in the power conversion circuit 2. By controlling the conduction time of the power switch, the energy transfer time per unit cycle is controlled. The controller 8 sends a pulse width modulation wave with a specific duty cycle, which is isolated and driven by the drive circuit 5 before being sent to the power switch in the power conversion circuit 2, thereby controlling the turn-on and turn-off time of the power switch. The drive circuit 5 includes an isolation drive chip and an input current-limiting resistor. The primary and secondary sides of the isolation drive chip are powered separately. The drive circuit 5 isolates and transmits the pulse width modulation signal (PWM signal) output by the controller through the drive chip, achieving signal isolation and improving drive capability, and providing switching signals for the primary and secondary main power transistors.

[0056] The output reverse current protection circuit 3 is used to prevent energy from the load end from flowing back into the main power circuit and damaging the power supply product when it is turned off, thus protecting the main power circuit from damage by reverse energy. Since load energy flows back into the power supply product when it is turned off, the reverse current protection circuit of this invention utilizes the unidirectional conduction performance of a diode to block the flow of load energy, thereby protecting the main power circuit from damage by reverse energy. The output reverse current protection circuit 3 includes a power switching transistor, a driving resistor, a driving chip, and its peripheral resistors and capacitors. The driving chip does not require a separate power supply and draws power directly from the output bus, resulting in a simple and reliable circuit structure. The output reverse current protection circuit 3 is implemented using a field-effect transistor (FET). The FET's own anti-parallel diode prevents output energy from flowing back, thus protecting the power supply product. The FET has low on-resistance and will not cause overheating damage.

[0057] The operating temperature sampling circuit 10 is used to collect the ambient temperature during the operation of the power supply product and send the collected ambient temperature to the controller. The controller determines whether the internal temperature of the power supply product is within a reasonable operating temperature range based on the ambient temperature value. If the ambient temperature exceeds its maximum operating temperature, the over-temperature protection of the power supply product is triggered to prevent over-temperature damage. The operating temperature sampling circuit 10 uses a thermistor for voltage division. The resistance of the thermistor changes with temperature, so the voltage division value changes with the operating temperature. The voltage division value is sent to the sampling port of the controller 8 for software processing, providing data for over-temperature protection. Using a thermistor for temperature sampling helps reduce the printed circuit board area.

[0058] The hardware protection sampling circuit 11 is used to collect overcurrent and short-circuit protection signals of the power supply product to ensure the real-time detection of overcurrent and short-circuit fault signals. The hardware protection sampling circuit 11 sends the collected overcurrent and short-circuit protection signals of the power supply product to the controller 8. The controller 8 determines whether a short circuit or output overcurrent has occurred in the power supply product based on this signal. If a short circuit or output overcurrent occurs, the controller 8 outputs a hardware protection signal, triggering hardware protection to directly shut down the module output, causing the module to shut down and cease operation. Simultaneously, the controller 8 collects the hardware protection status signal. When the hardware protection disappears, the controller resets the hardware protection signal, allowing the power supply product to return to normal operation. The hardware protection sampling circuit 11 is implemented using a comparator, comparing the current sample value with a reference voltage value to determine whether a hardware overcurrent has occurred based on the comparison result. Once an overcurrent occurs, the drive signal output is directly disabled to shut down the power supply product and protect it from damage. Compared to software protection mechanisms, this has a faster response speed, protecting the power supply product in the shortest possible time.

[0059] The output current sampling circuit 6 is used to collect the output current signal, providing data for hardware protection circuits and software overcurrent protection, and also providing data for the controller 8 to implement loop control. The output current signal, as the control object of the controller 8's inner current loop, provides a direct data source for achieving timely load dynamic response and stable output voltage. The output current sampling circuit 6 uses a high-precision sampling resistor for acquisition, which is then processed by an operational amplifier before being sent to the controller's sampling port. Software processing is then used to provide data for output overcurrent protection, hardware protection current, and current loop calculations. Compared to sensor sampling, using a high-precision sampling resistor for current sampling has the advantages of simpler circuitry and smaller printed circuit board footprint, which facilitates modular design.

[0060] The output voltage sampling circuit 9 is used to collect the output voltage signal, providing a source for the software to judge output overvoltage and for the controller to perform loop control. It also provides a basis for the software to implement output overvoltage protection and the controller to implement loop control. The output voltage signal collected by the output voltage sampling circuit 9 is sent to the controller 8. The output voltage sampling circuit 9 uses resistors for voltage division, processes the signal through an operational amplifier, and then sends it to the sampling port of the controller. The software performs calculations to provide data for output overvoltage and voltage loop calculations.

[0061] The output filter circuit 4 is used to filter out low-frequency jitter on the output bus, keeping the output voltage smooth and providing a stable output voltage to the load. The output filter circuit 4 includes an output filter inductor and an output filter capacitor. This circuit acts as a storage tank for output energy and also effectively filters out AC ripple on the output bus. The output filter circuit adopts the mature inductor + capacitor filtering method of existing technology, which can effectively filter out low-frequency ripple in the output voltage, making the output voltage more stable and providing a stable input voltage for the downstream load.

[0062] The controller 8, as the core control unit of the power supply product, has the core function of calculating the turn-on and turn-off times of the power switching transistors in the power conversion circuit based on the collected output current and output voltage signals using a software control algorithm, thereby realizing energy transfer. The controller 8 undertakes the main functions of input voltage detection, output voltage detection, output current detection, temperature detection, and loop control. It can not only perform simple sampling and judgment but also implement voltage loop control algorithms, current loop control algorithms, and current limiting loop control algorithms. The controller 8 is mainly used to collect input voltage signals, temperature signals, hardware protection signals, output voltage signals, and output current signals. Simultaneously, it performs current limiting loop, voltage loop, and current loop control based on the collected output voltage and current signals, and calculates closed-loop control using a proportional-integral-derivative (PID) algorithm.

[0063] The functions of controller 8 will be described in detail below.

[0064] The controller 8 is used to implement output voltage loop control, output current loop control and output current limiting loop control, and also undertakes input voltage detection, output voltage detection, output current detection, temperature detection and hardware protection detection functions.

[0065] The controller 8 collects the input voltage signal from the input voltage sampling circuit 7 and compares the collected input voltage signal with a set value to determine whether the input voltage is operating within the normal input voltage range. If it exceeds the upper limit of the normal input voltage, the overvoltage protection program is executed, and the system waits for the input voltage to recover to the normal operating voltage. If it is below the lower limit of the normal input voltage, the undervoltage protection program is executed, and the system waits for the input voltage to recover to the normal operating voltage.

[0066] The controller 8 collects the ambient temperature signal from the operating temperature sampling circuit 10 and compares the collected temperature signal with the set value to determine whether the power supply product is operating within the normal temperature range. If the operating temperature exceeds the upper limit of the normal operating temperature, an over-temperature protection program is executed, and the system waits for the temperature signal to return to the normal operating temperature. If the operating temperature is below the lower limit of the normal operating temperature, an over-temperature protection program is executed, and the system waits for the temperature signal to return to the normal operating temperature.

[0067] The controller 8 collects the hardware protection signal collected by the hardware protection sampling circuit 11, and determines whether the power supply product has experienced hardware protection based on the hardware protection signal. If hardware protection occurs, the power supply product's hardware automatic shutdown module output is activated, and the software locks the protection mode and waits for the hardware protection to disappear. When the hardware protection disappears, the software resets the hardware fault signal, and the power supply product resumes operation.

[0068] The controller 8 acquires the output voltage signal collected by the output voltage sampling circuit 9 and compares the acquired output voltage signal with a set value to determine whether the output voltage is operating within the normal output voltage range. If it exceeds the upper limit of the normal output voltage, the controller executes the output overvoltage protection program and waits for the output voltage signal to return to the normal operating voltage.

[0069] The controller 8 collects the output current signal from the output current sampling circuit 6 and compares the collected output current signal with a set value to determine whether the power supply product's output current is operating within the normal output current range. If it exceeds the upper limit of the normal operating current, an overcurrent protection program is executed, and the system waits for the output current signal to return to normal.

[0070] When controller 8 detects output current limiting or short circuit, the output current sampling value Io_samp will be greater than the current limiting loop reference setpoint Io_ref. Controller 8 performs PID loop calculation through the current limiting loop to obtain the current limiting loop PID loop calculated value Vo_cal. At this time, the current limiting loop PID loop calculated value Vo_cal is much smaller than the output voltage initial setpoint Vo_target. Therefore, the current limiting loop PID loop calculated value Vo_cal is assigned to the output voltage reference value Vo_set, thereby limiting or preventing the output voltage from being soft-started and boosted, thus limiting or shutting down the output voltage to protect the power supply product.

[0071] The cascaded current limiting loop control method described in this invention will not cause power products to fail to protect in a timely manner due to insufficient control accuracy, and will ensure that when the power product experiences current limiting or short circuit protection, it will promptly enter the current limiting output or short circuit protection state.

[0072] like Figure 2 The above describes a cascaded current-limiting loop control method. Figure 2 In this control method, Io_ref is the reference setpoint for the current limiting loop, Io_samp is the sampled output current value, Vo_cal is the calculated value of the PID loop in the current limiting loop (and also the input of the voltage loop), Vo_target is the initial setpoint of the output voltage, Vo_set is the reference value of the output voltage, Vo_samp is the sampled output voltage value, and Io_cal is the calculated output value of the voltage loop (and also the input of the current loop). The control strategy of this method mainly includes current limiting loop, voltage loop, current loop, and PWM (Pulse Width Modulation, hereinafter referred to as PWM) drive control.

[0073] like Figure 3 As shown, the cascaded current-limiting loop control method includes the following steps:

[0074] S1. After the controller system is initialized, the AD sampling interrupt program is executed to sample the input voltage signal, output voltage signal, output current signal, operating environment temperature signal and hardware protection signal.

[0075] S2. The sampled signal is conditioned using a filtering algorithm. Based on the conditioned sampled signal, it is determined whether the power supply product has malfunctioned. The malfunctions include input overvoltage, input undervoltage, output overvoltage, output overcurrent, output short circuit, overtemperature, or hardware protection. If the power supply product malfunctions, the controller shuts down the PWM drive signal after detecting the fault signal, thereby shutting down the power supply product. If the power supply product malfunction disappears or no fault occurs, the controller enters the current limiting loop adjustment after initialization, performs current limiting loop PID loop calculation, and enters the output soft start control program. After the soft start is completed, voltage loop PID control and current loop PID control are then performed. Figure 3 This section mainly introduces the loop control process, namely the current limiting loop regulation, voltage loop regulation, and current loop regulation. The output result of the current loop is the desired control result of this loop control process.

[0076] S3. When an overcurrent or short-circuit condition occurs in the load, the controller collects the output current signal and inputs it to the current-limiting loop for PID calculation. The controller then outputs a control signal as the input to the voltage loop, which performs PID control and outputs the control signal as the input to the current loop. The current loop then performs PID control and outputs the control signal as the input to the PWM module. The PWM module outputs a PWM drive signal, adjusting the width of the PWM drive signal output by the controller in real time to control the turn-on time of the power switching transistors and protect the power supply product. For overcurrent or short-circuit conditions, this invention uses a cascaded execution of the current-limiting loop and the main control loop (inner voltage loop and outer current loop) to ensure timely response of the DC-DC converter to abnormal load current conditions, thus protecting the power supply product from damage.

[0077] As a further improvement to the above technical solution, the current-limiting loop PID loop calculation in steps S2 and S3 includes:

[0078] The reference setpoint Io_ref and the output current sample value Io_samp of the current limiting loop are used as the input of the current limiting loop. After the two are processed by the current limiting loop PID calculation, the current limiting loop PID loop calculation value Vo_cal is obtained.

[0079] The calculated value Vo_cal of the current limiting loop is compared with the initial set value Vo_target of the output voltage, and the comparison result is used as the reference value Vo_set of the output voltage.

[0080] As a further improvement to the above technical solution, the voltage loop PID control in steps S2 and S3 includes:

[0081] The output voltage reference value Vo_set and the output voltage sample value Vo_samp are used as inputs to the voltage loop. After being processed by the voltage loop PID, the voltage loop calculation output value Io_cal is obtained, which is used as the output of the voltage loop calculation.

[0082] As a further improvement to the above technical solution, the current loop PID control in steps S2 and S3 includes:

[0083] The voltage loop calculation output value Io_cal and the output current sampling value Io_samp are used as inputs to the current loop, and the result obtained after the current loop PID calculation is used as the output of the current loop calculation.

[0084] As a further improvement to the above technical solution, the PWM drive signal output in step S2 or the PWM module outputting the PWM drive signal in step S3 includes:

[0085] The output of the current loop calculation is used as the input to the PWM module. After converting the input signal, the PWM module outputs six PWM drive signals: PWMA, PWMB, PWMC, and PWMD. 、 PWME and PWMF; the PWMA, PWMB, PWMC and PWMD drive signals are used to drive the four main power transistors of the primary-side full-bridge circuit, respectively; the PWME and PWMF drive signals are used to drive the four power transistors of the secondary-side synchronous rectifier circuit.

[0086] Compared to traditional voltage and current loop PID control, this invention incorporates a current-limiting loop in series throughout the entire control loop. The voltage loop primarily achieves closed-loop control of the output voltage, while the current loop ensures the power supply product operates normally within its full load range.

[0087] In the cascaded current-limiting loop control method described in this invention, when the load experiences overcurrent or short-circuit conditions, the output current signal collected by the controller 8 is calculated using the PID algorithm of the current-limiting loop, and the control quantity is directly output to the input of the voltage loop. The voltage loop then calculates the output using the PID algorithm and outputs it to the input of the current loop. By adjusting the width of the PWM (Pulse Width Modulation) drive signal output by the controller 8 in real time, the turn-on time of the power switching transistor in the power conversion circuit is controlled, preventing damage to the power supply product during protection. The cascaded current-limiting loop control method described in this invention can adjust the loop in real time according to the magnitude of the load current, offering advantages such as fast response and high reliability.

[0088] like Figure 3 The flowchart of a cascaded current-limiting loop control method is shown below.

[0089] S1. After the controller system is initialized, the AD sampling interrupt program is executed. The input voltage signal, output voltage signal, output current signal, over-temperature signal and hardware protection signal are sampled in the interrupt.

[0090] S2. The sampled signal is conditioned using a software filtering algorithm. Based on the conditioned sampled signal, it is determined whether faults such as input overvoltage, input undervoltage, output overvoltage, output overcurrent, overtemperature, and hardware protection have occurred. If the power supply product malfunctions, the fault restart initialization program is entered, and the system restarts after the fault disappears. If no fault occurs, the current limiting loop PID loop calculation is entered. The calculated value Vo_cal of the current limiting loop is compared with the initial set value Vo_target of the output voltage. The comparison result is used as the output voltage reference value Vo_set. The output soft start control program is then entered. After the soft start is completed, voltage loop PID control and current loop PID control are performed respectively.

[0091] In this embodiment, when no current limiting or short circuit protection occurs, the power product controller system operates normally according to the above-described workflow (steps S1 to S2). When current limiting or short circuit protection occurs, the current limiting loop PID loop calculation is initiated. When an overcurrent or short circuit occurs, the output current sampling value Io_samp will be greater than the current limiting loop reference setpoint Io_ref. After calculation by the current limiting loop, the current limiting loop calculated value Vo_cal is obtained. The current limiting loop calculated value Vo_cal is much smaller than the initial output voltage setpoint Vo_target. Therefore, the current limiting loop calculated value Vo_cal is assigned to the output voltage reference value Vo_set, thereby limiting or preventing the output voltage from being soft-started and boosted, thus limiting or shutting down the output voltage to protect the power product.

[0092] The cascaded current-limiting loop control method described in this invention prevents power supply products from failing to protect themselves due to insufficient control precision. It ensures that when a power supply product experiences current limiting or short-circuit protection, it promptly enters current-limiting output or short-circuit protection mode. This invention enables the power supply product to adjust its output voltage to enter current-limiting output or promptly shut down its output for protection when current limiting or short-circuit conditions occur at the load end, preventing delays in protection due to insufficient control precision and achieving the desired protection effect.

[0093] The above-described embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A cascaded current-limiting loop control method, characterized in that, The method includes the following steps: S1. After the controller system is initialized, the AD sampling interrupt program is executed to sample the input voltage signal, output voltage signal, output current signal, operating environment temperature signal and hardware protection signal. S2. The sampled signal is conditioned using a filtering algorithm. Based on the conditioned sampled signal, it is determined whether the power supply product has malfunctioned. The malfunctions include input overvoltage, input undervoltage, output overvoltage, output overcurrent, output short circuit, overtemperature, or hardware protection. If the power supply product malfunctions, the controller shuts down the PWM drive signal after detecting the fault signal, thereby shutting down the power supply product. If the power supply product malfunction disappears or no fault occurs, the controller enters the current limiting loop adjustment, performs current limiting loop PID loop calculation, and enters the output soft start control program. After the soft start is completed, voltage loop PID control and current loop PID control are then performed. S3. When the load experiences overcurrent or short circuit, the controller collects the output current signal and inputs it into the current limiting loop for PID loop calculation. The controller then outputs a control quantity as the input to the voltage loop, which performs PID control and outputs the control quantity as the input to the current loop. The current loop then performs PID control and outputs the control quantity as the input to the PWM module. The PWM module outputs a PWM drive signal and adjusts the width of the PWM drive signal output by the controller in real time to control the turn-on time of the power switching transistor and protect the power supply product. The current-limiting loop PID loop calculation in steps S2 and S3 includes: The reference setpoint Io_ref and the output current sample value Io_samp of the current limiting loop are used as the input of the current limiting loop. After the two are processed by the current limiting loop PID calculation, the current limiting loop PID loop calculation value Vo_cal is obtained. The calculated value Vo_cal of the current limiting loop is compared with the initial set value Vo_target of the output voltage, and the comparison result is used as the reference value Vo_set of the output voltage. The voltage loop PID control in steps S2 and S3 includes: The output voltage reference value Vo_set and the output voltage sample value Vo_samp are used as inputs to the voltage loop. After being processed by the voltage loop PID, the voltage loop calculation output value Io_cal is obtained, which is used as the output of the voltage loop calculation. The current loop PID control in steps S2 and S3 includes: The voltage loop calculation output value Io_cal and the output current sampling value Io_samp are used as the inputs of the current loop, and the result obtained after the current loop PID calculation is used as the output of the current loop calculation. The PWM drive signal output in step S2 or the PWM module outputting the PWM drive signal in step S3 includes: The output of the current loop calculation is used as the input of the PWM module. After converting the input signal, the PWM module outputs six PWM drive signals: PWMA, PWMB, PWMC, PWMD, PWME, and PWMF. The PWMA, PWMB, PWMC, and PWMD drive signals are used to drive the four main power transistors of the primary-side full-bridge circuit, respectively. The PWME and PWMF drive signals are used to drive the four power transistors of the secondary-side synchronous rectifier circuit.

2. A cascaded current-limiting loop control device, characterized in that, The control device is used to implement the method as described in claim 1, and the control device includes: Input filter circuit (1), input voltage sampling circuit (7), power conversion circuit (2), drive circuit (5), output anti-backflow circuit (3), operating temperature sampling circuit (10), hardware protection sampling circuit (11), output current sampling circuit (6), output voltage sampling circuit (9), output filter circuit (4), and controller (8); The output terminal of the input filter circuit (1) is connected to the input terminal of the power conversion circuit (2); the output terminal of the power conversion circuit (2) is connected to the input terminal of the output anti-backflow circuit (3) and the input terminal of the output current sampling circuit (6); the output terminal of the output anti-backflow circuit (3) is connected to the input terminal of the output filter circuit (4) and the input terminal of the output voltage sampling circuit (9); the output terminals of the input voltage sampling circuit (7), the output terminals of the output current sampling circuit (6), the output voltage sampling circuit (9), the operating temperature sampling circuit (10), and the hardware protection sampling circuit (11) are all connected to the input terminal of the controller (8); the output terminal of the controller (8) is connected to the input terminal of the drive circuit (5), and the output terminal of the drive circuit (5) is connected to the input terminal of the power conversion circuit (2); The controller (8) is used to implement output voltage loop control, output current loop control and output current limiting loop control, and at the same time perform input voltage detection, output voltage detection, output current detection, temperature detection and hardware protection detection. The controller (8) collects the input voltage signal collected by the input voltage sampling circuit (7) and compares the collected input voltage signal with the set value to determine whether the input voltage is working within the normal input voltage range. If it exceeds the upper limit of the normal input voltage, the input overvoltage protection program is executed, and the input voltage is waited to recover to the normal working voltage. If it is lower than the lower limit of the normal input voltage, the input undervoltage protection program is executed, and the input voltage is waited to recover to the normal working voltage. The controller (8) collects the ambient temperature signal collected by the working temperature sampling circuit (10), and compares the collected temperature signal with the set value to determine whether the working temperature of the power supply product is within the normal temperature range; if it exceeds the upper limit of the normal working temperature, it executes the over-temperature protection program and waits for the temperature signal to return to the normal working temperature; if it is below the lower limit of the normal working temperature, it executes the over-temperature protection program and waits for the temperature signal to return to the normal working temperature. The controller (8) collects the hardware protection signal collected by the hardware protection sampling circuit (11) and determines whether the power supply product has experienced hardware protection based on the hardware protection signal. If hardware protection occurs, the power supply product's hardware automatic shutdown module outputs, and the software locks the protection mode and waits for the hardware protection to disappear. When the hardware protection disappears, the software resets the hardware fault signal, and the power supply product resumes operation. The controller (8) collects the output voltage signal collected by the output voltage sampling circuit (9) and compares the collected output voltage signal with the set value to determine whether the output voltage is working within the normal output voltage range; if it exceeds the upper limit of the normal output voltage, the output overvoltage protection program is executed, and the controller waits for the output voltage signal to return to the normal working voltage. The controller (8) collects the output current signal collected by the output current sampling circuit (6) and compares the collected output current signal with the set value to determine whether the output current of the power supply product is working within the normal output current range; if it exceeds the upper limit of the normal operating current, the overcurrent protection program is executed, and the system waits for the output current signal to recover to the normal output current. The controller (8) performs current limiting loop, voltage loop and current loop control based on the collected output voltage signal and output current signal, and performs closed loop control based on the proportional-integral-derivative algorithm, so that the output voltage is within the normal operating voltage range when the load is dynamic and the input voltage is dynamic.

3. The cascaded current-limiting loop control device according to claim 2, characterized in that, The input filter circuit (1) is used to filter out high-frequency interference signals in the input voltage; The output filter circuit (4) is used to filter out low-frequency jitter on the output bus so that the output voltage remains smooth and provides a stable output voltage to the load. The output filter circuit (4) includes an output filter inductor and an output filter capacitor. The input voltage sampling circuit (7) is used to collect the input voltage signal and send the collected input voltage signal to the controller (8). The controller (8) determines whether the input voltage is within the normal operating range based on the collected input voltage signal. If the controller (8) determines that an input overvoltage or input undervoltage has occurred based on the collected input voltage signal, the power supply product triggers protection and prohibits the power supply product from outputting. The output current sampling circuit (6) is used to collect the output current signal and send the collected output current signal to the controller (8). The controller (8) performs hardware protection, output overcurrent judgment and controller current inner loop control based on the output current signal. The output voltage sampling circuit (9) is used to collect the output voltage signal and send the collected output voltage signal to the controller (8). The controller (8) performs output overvoltage judgment and controller loop control based on the output voltage signal. The working temperature sampling circuit (10) is used to collect the ambient temperature when the power supply product is working and send the collected ambient temperature to the controller (8). The controller (8) determines whether the internal temperature of the power supply product is within the reasonable working temperature range based on the ambient temperature value. If the ambient temperature exceeds its maximum working temperature, the power supply product over-temperature protection is triggered. The hardware protection sampling circuit (11) is used to collect the overcurrent and short-circuit protection signals of the power supply product and send the collected overcurrent and short-circuit protection signals of the power supply product to the controller (8). The controller (8) determines whether the power supply product has a short circuit or output overcurrent based on the signal. If the power supply product has a short circuit or output overcurrent, the controller (8) outputs a hardware protection signal to trigger the hardware protection shutdown module output, so that the module is turned off and does not work. At the same time, the controller (8) collects the hardware protection status signal. When the hardware protection disappears, the controller (8) resets the hardware protection signal so that the power supply product returns to normal operation.

4. The cascaded current-limiting loop control device according to claim 2, characterized in that, The power conversion circuit (2) is used to realize energy transfer and the conversion of input voltage to output voltage; the power conversion circuit (2) includes a power switching transistor.

5. The cascaded current-limiting loop control device according to claim 4, characterized in that, The drive circuit (5) is used to condition the control signal sent by the controller (8) through the isolation drive chip, and send the conditioned signal to the power switch in the power conversion circuit (2), and control the conduction time of the power switch through the signal to control the energy transmission time per unit cycle. The controller (8) emits a pulse width modulation wave with a specific duty cycle. After being isolated and driven by the driving circuit (5), the pulse width modulation wave is sent to the power switch in the power conversion circuit (2) to control the turn-on and turn-off time of the power switch. The driving circuit (5) includes an isolation driving chip and an input current limiting resistor, and the primary and secondary sides of the isolation driving chip are powered separately.

6. The cascaded current-limiting loop control device according to claim 2, characterized in that, The output anti-backflow circuit (3) is used to prevent the load end energy from flowing back into the main power circuit and damaging the power supply product when the power supply product is turned off; the output anti-backflow circuit (3) includes a switching transistor, a driving resistor, a driving chip and peripheral resistors and capacitors.

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