A UPS power supply power conversion circuit based on phase pre-synchronization

Abstract

The utility model relates to a UPS power supply conversion circuit based on phase pre -synchronization belongs to power supply conversion circuit technical field. UPS power supply conversion circuit contains zero -crossing detection circuit, inverter output sampling circuit, synchronous controller, PWM modulation unit, composite switch circuit and bypass relay. First through zero -crossing detection circuit real -time acquisition main power grid output's phase signal, inverter output sampling circuit synchronous acquisition inverter output's phase signal, both will signal transmission to synchronous controller, and the controller output signal drives the output voltage phase of adjustment inverter, makes inverter keep with main power grid same commercial power phase, realizes phase pre -synchronous. And utilize synchronous controller drive composite switch circuit and bypass relay, under normal commercial power mode, and the electric energy is directly supplied to the load through the bypass relay, and the power supply conversion is carried out through the composite switch circuit when switching. The utility model can reduce the hardware cost of UPS power supply conversion.

Description

Technical Field

[0001] This utility model relates to the field of power supply conversion circuit technology, and more specifically to a UPS power supply conversion circuit based on phase pre-synchronization. Background Technology

[0002] In the power supply sector, UPS (Uninterruptible Power Supply) is a core device ensuring continuous power supply to critical equipment. The stability and reliability of its power conversion directly affect the safe operation of the load equipment. Currently, existing UPS systems face two major challenges when switching to battery inverter mode in case of mains power failure:

[0003] (1) Switching delay: Traditional relays or static switches need to detect voltage abnormalities (usually 5-10ms) when switching, resulting in millisecond-level interruptions in the output;

[0004] (2) Phase change: If the mains power and the inverter are out of phase at the moment of switching, it will cause a current surge and damage the back-end equipment.

[0005] In existing technologies, most online UPS systems employ double-conversion UPS to ensure normal power supply and power switching, offering advantages such as stable power supply, strong anti-interference capabilities, and zero switching time. However, double-conversion online UPS systems have a more complex circuit structure, requiring the coordinated operation of core components such as rectifiers, inverters, and batteries, and placing higher performance demands on these components, resulting in higher overall equipment manufacturing costs. Furthermore, under normal mains power conditions, the power from a double-conversion online UPS undergoes two conversions: AC→DC→AC, leading to lower operating efficiency compared to online interactive UPS systems. Therefore, a low-cost phase-synchronous UPS power switching circuit is urgently needed for offline / hybrid UPS systems. Utility Model Content

[0006] To address the shortcomings of existing technologies, this utility model provides a UPS power supply switching circuit based on phase pre-synchronization, thereby solving the technical problem of high cost of existing UPS power supply switching equipment.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] This utility model provides a UPS power supply conversion circuit based on phase pre-synchronization, including a zero-crossing detection circuit, an inverter output sampling circuit, a synchronization controller, a PWM modulation unit, a composite switching circuit, and a bypass relay; wherein,

[0009] The output of the main power grid is connected to the user load via a bypass relay; the input of the zero-crossing detection circuit is connected in parallel to the output of the main power grid, and the output of the zero-crossing detection circuit is connected to the first input of the synchronization controller.

[0010] The input terminal of the inverter output sampling circuit is connected to the output terminal of the inverter, and the output terminal of the inverter output sampling circuit is connected to the second input terminal of the synchronous controller; the input terminal of the inverter is connected to the UPS power supply.

[0011] The output terminal of the synchronous controller is connected to the input terminal of the PWM modulation unit, the drive terminal of the composite switching circuit, and the drive terminal of the bypass relay, respectively; the output terminal of the PWM modulation unit is connected to the drive terminal of the inverter.

[0012] The output terminal of the inverter is connected to the input terminal of the composite switching circuit; the output terminal of the composite switching circuit is connected to the user load.

[0013] Preferably, the zero-crossing detection circuit includes a step-down transformer, a first optocoupler isolator, and a Schmitt trigger;

[0014] The input terminal of the step-down transformer is connected in parallel to the output terminal of the main power grid, and the output terminal of the step-down transformer is connected to the input terminal of the first optocoupler isolator.

[0015] The output of the first optocoupler is connected to the input of the Schmitt trigger, and the output of the Schmitt trigger is connected to the first input of the synchronous controller.

[0016] Preferably, the inverter output sampling circuit includes a voltage transformer, a bias circuit, and a comparator;

[0017] The input terminal of the voltage transformer is connected to the output terminal of the inverter, and the output terminal of the voltage transformer is connected to the input terminal of the comparator via a bias circuit; the output terminal of the comparator is connected to the second input terminal of the synchronous controller.

[0018] Preferably, the PWM modulation unit includes a second optocoupler isolator and a PWM signal driver; wherein,

[0019] The input of the second optocoupler is connected to the output of the synchronous controller, the output of the second optocoupler is connected to the input of the PWM signal driver, and the output of the PWM signal driver is connected to the drive of the inverter.

[0020] Preferably, the composite switching circuit includes an IGBT driver, a relay driver, an IGBT module, and a magnetic latching relay; wherein,

[0021] The collector terminals of the IGBT module and the input terminals of the magnetic latching relay are connected to the output terminals of the inverter, respectively. The emitter terminals of the IGBT module are connected to the user load, and the output terminals of the magnetic latching relay are connected to the user load.

[0022] The output of the synchronous controller is connected to the input of the IGBT driver and the input of the relay driver, respectively; the output of the IGBT driver is connected to the driving end of the IGBT module, and the output of the relay driver is connected to the driving end of the magnetic latching relay.

[0023] Preferably, the composite switching circuit further includes an RC snubber circuit, a freewheeling diode, and an overcurrent protection resistor; wherein,

[0024] The two ends of the RC snubber circuit are connected in parallel with the collector and emitter terminals of the IGBT module;

[0025] The anode of the freewheeling diode is connected to the output terminal of the magnetic latching relay, and the cathode of the freewheeling diode is connected to the input terminal of the magnetic latching relay.

[0026] The first end of the overcurrent protection resistor is connected to the emitter terminal of the IGBT module, and the second end of the overcurrent protection resistor is connected to the user load.

[0027] In summary, this utility model has the following beneficial effects:

[0028] This invention provides a UPS power supply conversion circuit based on phase pre-synchronization. A zero-crossing detection circuit collects the phase signal output from the main grid in real time, and an inverter output sampling circuit synchronously acquires the phase signal output from the inverter. Both signals are transmitted to a synchronization controller, which outputs an SPWM signal to drive and adjust the inverter's output voltage phase, ensuring that the inverter maintains the same mains phase as the grid during no-load operation, thus achieving phase pre-synchronization. The synchronization controller also drives a composite switching circuit and a bypass relay to prepare for power supply switching. In normal mains mode, power is directly supplied to the load through the bypass relay. During switching, the composite switching circuit performs power conversion to power the inverter, reducing hardware costs and minimizing power conversion steps, thus avoiding the low efficiency problem of existing double-conversion online UPS systems. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of a UPS power supply conversion circuit based on phase pre-synchronization according to this utility model.

[0030] Figure 2 This is a structural diagram of the zero-crossing detection circuit of this utility model;

[0031] Figure 3 This is a block diagram of the inverter output sampling circuit of this utility model;

[0032] Figure 4 This is a block diagram of the composite switch circuit principle of this utility model. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to the accompanying drawings.

[0034] To make the objectives, solutions, and advantages of this utility model clearer, the following detailed description of this utility model is provided in conjunction with the embodiments and accompanying drawings. The illustrative embodiments and descriptions of this utility model are only used to explain this utility model and are not intended to limit this utility model.

[0035] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that these specific details are not necessary to implement the present invention. In other embodiments, well-known structures, circuits, materials, or methods are not specifically described in order to avoid obscuring the present invention.

[0036] The following is in conjunction with the appendix of this utility model. Figures 1 to 3 The embodiments of this utility model will be described in detail below.

[0037] Example 1:

[0038] In this embodiment, refer to Figure 1 As shown, a UPS power supply conversion circuit based on phase pre-synchronization is provided, including a zero-crossing detection circuit, an inverter output sampling circuit, a synchronization controller, a PWM modulation unit, a composite switching circuit, and a bypass relay. Among them,

[0039] The output of the main power grid is connected to the user load via a bypass relay; the input of the zero-crossing detection circuit is connected in parallel to the output of the main power grid, and the output of the zero-crossing detection circuit is connected to the first input of the synchronization controller.

[0040] The input terminal of the inverter output sampling circuit is connected to the output terminal of the inverter, and the output terminal of the inverter output sampling circuit is connected to the second input terminal of the synchronous controller; the input terminal of the inverter is connected to the UPS power supply.

[0041] The output of the synchronous controller is connected to the input of the PWM modulation unit, the drive of the composite switching circuit, and the drive of the bypass relay, respectively; the output of the PWM modulation unit is connected to the drive of the inverter.

[0042] The inverter's output is connected to the input of the composite switching circuit; the composite switching circuit's output is connected to the user's load.

[0043] In this embodiment, the zero-crossing detection circuit collects the zero-crossing signal output by the main grid in real time, and the inverter output sampling circuit synchronously obtains the phase information output by the inverter. After the two transmit the signals to the synchronization controller, the synchronization controller can obtain the phase difference between the main grid and the inverter in advance, and generate a corresponding SPWM signal to the PWM modulation unit according to the phase difference. Then, the PWM modulation unit drives the inverter bridge in the inverter to change the phase of the inverter's output voltage, so as to synchronize the phase of the inverter's output voltage with the mains power phase in advance, thereby realizing the phase pre-synchronization of the UPS power supply conversion.

[0044] In this embodiment, the synchronization controller can be implemented using a digital signal processor of model TMS320F28335, or it can be implemented using a control chip such as STM32G4 series that has a built-in high-precision timer and supports hardware PWM phase shifting. The specific choice can be made according to the actual scenario and requirements. This embodiment does not make any specific limitations.

[0045] In this embodiment, the zero-crossing detection circuit includes a step-down transformer, a first optocoupler isolator, and a Schmitt trigger.

[0046] In this circuit, the input terminal of the step-down transformer is connected in parallel to the output terminal of the main power grid, and the output terminal of the step-down transformer is connected to the input terminal of the first optocoupler isolator. The step-down transformer is used to step down the high-voltage AC mains power from the main power grid. In the above circuit, a rectifier bridge can be added after the step-down transformer for full-wave rectification, which facilitates the subsequent detection of the zero-crossing signal of the mains power by the first optocoupler isolator.

[0047] The output of the first optocoupler is connected to the input of the Schmitt trigger, and the output of the Schmitt trigger is connected to the first input of the synchronous controller.

[0048] The Schmitt trigger can be a 74HC14 model. When detecting the mains phase, the Schmitt trigger can shape the signal output from the first optocoupler isolator, which can play an anti-interference role.

[0049] Specifically, refer to Figure 2As shown, in one embodiment of this utility model, the zero-crossing detection circuit includes a step-down transformer T1, a current-limiting resistor R1, a first optocoupler isolator U1, and a Schmitt trigger S1. The step-down transformer T1 steps down the input mains power to achieve primary-secondary electrical isolation and block common-mode interference. The stepped-down signal is connected to the input terminal of the first optocoupler isolator U1 (HCPL-817) via the current-limiting resistor R1. The first optocoupler isolator U1 performs photoelectric conversion, and the optocoupler output is connected to the Schmitt trigger S1 to eliminate noise interference before outputting the zero-crossing detection signal of the mains power. The phase of the mains power grid can be determined based on this signal. AC-AC isolation is achieved through the step-down transformer, high-low voltage isolation is achieved through the first optocoupler isolator, and digital noise isolation is achieved through the Schmitt trigger, improving the safety of phase detection and providing a certain degree of anti-interference capability.

[0050] also, Figure 2 In this embodiment, a diode D1 is connected in reverse parallel to the input terminal of the first optocoupler U1 to prevent reverse breakdown. Resistor R2 is used to prevent short circuit at the power supply VCC terminal, and resistor R3 is used to provide overcurrent protection for the first optocoupler U1.

[0051] In this embodiment, refer to Figure 3 As shown, the inverter output sampling circuit includes a voltage transformer, a bias circuit, and a comparator. The input of the voltage transformer is connected to the output of the inverter, and the output of the voltage transformer is connected to the input of the comparator via the bias circuit. The output of the comparator is connected to the second input of the synchronous controller.

[0052] Specifically, the voltage transformer steps down the inverter's no-load output voltage for sampling, and then the bias circuit raises the sampled AC signal to a DC bias voltage. At this point, the comparator converts the AC signal into a digital square wave signal with the same frequency as the input signal and transmits it to the synchronous controller for further processing.

[0053] In this embodiment, the PWM modulation unit includes a second optocoupler isolator and a PWM signal driver; wherein...

[0054] The input of the second optocoupler is connected to the output of the synchronous controller, the output of the second optocoupler is connected to the input of the PWM signal driver, and the output of the PWM signal driver is connected to the drive of the inverter.

[0055] The second optocoupler isolator can be a TLP250 model, which uses a DIP-8 package, has an isolation voltage of 2500Vrms and a maximum propagation delay of 500ns, and is small in size with low maintenance costs. The PWM driver can be an IR2110 driver chip, which is small in size, has a fast response, strong driving capability, low cost, and is easy to debug. Alternatively, other optocouplers and PWM drivers can be selected according to the actual scenario and requirements; these will not be specifically described in this embodiment.

[0056] Specifically, since the inverter primarily converts DC power to AC power through an inverter bridge, which also has the ability to adjust the output voltage frequency and amplitude, the PWM modulation unit can drive the inverter bridge in the inverter based on the SPWM signal output by the synchronous controller, changing the phase of the inverter's output voltage to synchronize it with the mains voltage phase. A second optocoupler isolator is used to isolate the synchronous controller from the PWM driver, ensuring the safe transmission of the SPWM signal. Simultaneously, the cooperation between the PWM driver and the synchronous controller enables rapid phase adjustment of the inverter, improving drive efficiency.

[0057] In this embodiment, refer to Figure 4 As shown, the composite switching circuit includes an IGBT driver, a relay driver, an IGBT module, and a magnetic latching relay.

[0058] In this configuration, the collector terminals of the IGBT module and the input terminals of the magnetic latching relay are connected to the output terminals of the inverter, respectively. The emitter terminals of the IGBT module are connected to the user load, and the output terminal of the magnetic latching relay is also connected to the user load. The output terminals of the synchronous controller are connected to the input terminals of the IGBT driver and the relay driver, respectively. The output terminal of the IGBT driver is connected to the drive terminal of the IGBT module, and the output terminal of the relay driver is connected to the drive terminal of the magnetic latching relay.

[0059] This embodiment achieves power switching through the cooperation of IGBT modules and magnetically latched relays, simultaneously meeting the requirements for response speed and conduction loss during switching. When the synchronous controller detects an abnormality in the mains power through the zero-crossing detection circuit (the inverter phase has completed pre-synchronization), it controls the bypass relay to disconnect the bypass and simultaneously generates an IGBT drive signal, which is transmitted to the IGBT driver. The IGBT driver drives the IGBT module to conduct instantaneously, and the current establishes a path through the IGBT (at this time, the relay is still open), seamlessly switching the load voltage to the UPS power supply. After a certain delay, such as 50 microseconds (to ensure that the IGBT is fully turned on), the synchronous controller outputs a relay drive signal to the relay driver, which activates the magnetically latched relay for zero-voltage engagement. The relay coil is energized, and the contacts close within 3ms. Because the IGBT module has eliminated the contact voltage difference, there is no arc during the engagement process. Finally, after the auxiliary contacts of the magnetically latched relay provide a feedback closing signal, the synchronous controller blocks the IGBT driver, and the load current automatically migrates to the relay path. The composite switching circuit in this embodiment can quickly switch the UPS power supply to provide power while achieving phase pre-synchronization. In a 220V system, it can ensure that the voltage difference at the moment of switching is less than 10V, reducing load voltage fluctuations and lowering component costs.

[0060] Example 2:

[0061] In this embodiment, to further improve the safety of power supply conversion, based on the composite switching circuit of Embodiment 1 above, an RC snubber circuit, a freewheeling diode, and an overcurrent protection resistor are also provided in the composite switching circuit. Among these,

[0062] The two ends of the RC snubber circuit are connected in parallel with the collector and emitter terminals of the IGBT module to suppress the turn-off voltage spikes of the IGBT module.

[0063] The anode of the freewheeling diode is connected to the output terminal of the magnetic latching relay, and the cathode of the freewheeling diode is connected to the input terminal of the magnetic latching relay. Connecting the freewheeling diode in reverse parallel with the magnetic latching relay coil can eliminate back electromotive force.

[0064] The first terminal of the overcurrent protection resistor is connected to the emitter terminal of the IGBT module, and the second terminal is connected to the user load. By connecting the overcurrent protection resistor in series with the emitter of the IGBT module, overcurrent protection can be provided for the IGBT module.

[0065] In this embodiment, by adding an RC snubber circuit, a freewheeling diode, and an overcurrent protection resistor to the composite switching circuit, the stability of the composite switching circuit can be improved, and the reliability of the overall circuit can be guaranteed while appropriately increasing the cost of the components.

[0066] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this utility model. It should be understood that the above description is only a specific embodiment of this utility model and is not intended to limit the scope of protection of this utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the scope of protection of this utility model.

Claims

1. A UPS power supply conversion circuit based on phase pre-synchronization, characterized in that, include: The circuit includes a zero-crossing detection circuit, an inverter output sampling circuit, a synchronous controller, a PWM modulation unit, a composite switching circuit, and a bypass relay; among which, The output of the main power grid is connected to the user load via a bypass relay; the input of the zero-crossing detection circuit is connected in parallel to the output of the main power grid, and the output of the zero-crossing detection circuit is connected to the first input of the synchronization controller. The input terminal of the inverter output sampling circuit is connected to the output terminal of the inverter, and the output terminal of the inverter output sampling circuit is connected to the second input terminal of the synchronous controller; the input terminal of the inverter is connected to the UPS power supply. The output terminal of the synchronous controller is connected to the input terminal of the PWM modulation unit, the drive terminal of the composite switching circuit, and the drive terminal of the bypass relay, respectively; the output terminal of the PWM modulation unit is connected to the drive terminal of the inverter. The output terminal of the inverter is connected to the input terminal of the composite switching circuit; the output terminal of the composite switching circuit is connected to the user load. The zero-crossing detection circuit includes a step-down transformer, a first optocoupler isolator, and a Schmitt trigger; wherein, the input terminal of the step-down transformer is connected in parallel to the output terminal of the main power grid, the output terminal of the step-down transformer is connected to the input terminal of the first optocoupler isolator, the output terminal of the first optocoupler isolator is connected to the input terminal of the Schmitt trigger, and the output terminal of the Schmitt trigger is connected to the first input terminal of the synchronization controller; The inverter output sampling circuit includes a voltage transformer, a bias circuit, and a comparator; the input terminal of the voltage transformer is connected to the output terminal of the inverter, and the output terminal of the voltage transformer is connected to the input terminal of the comparator via the bias circuit; the output terminal of the comparator is connected to the second input terminal of the synchronous controller. The PWM modulation unit includes a second optocoupler isolator and a PWM signal driver; wherein, the input terminal of the second optocoupler isolator is connected to the output terminal of the synchronous controller, the output terminal of the second optocoupler isolator is connected to the input terminal of the PWM signal driver, and the output terminal of the PWM signal driver is connected to the drive terminal of the inverter. The composite switching circuit includes an IGBT driver, a relay driver, an IGBT module, and a magnetic latching relay. The collector terminal of the IGBT module and the input terminal of the magnetic latching relay are connected to the output terminal of the inverter, respectively. The emitter terminal of the IGBT module is connected to the user load, and the output terminal of the magnetic latching relay is connected to the user load. The output terminal of the synchronization controller is connected to the input terminals of the IGBT driver and the relay driver, respectively. The output terminal of the IGBT driver is connected to the drive terminal of the IGBT module, and the output terminal of the relay driver is connected to the drive terminal of the magnetic latching relay. The composite switching circuit also includes an RC snubber circuit, a freewheeling diode, and an overcurrent protection resistor; wherein, the two ends of the RC snubber circuit are connected in parallel with the collector and emitter terminals of the IGBT module; the anode of the freewheeling diode is connected to the output terminal of the magnetic latching relay, and the cathode of the freewheeling diode is connected to the input terminal of the magnetic latching relay; the first end of the overcurrent protection resistor is connected to the emitter terminal of the IGBT module, and the second end of the overcurrent protection resistor is connected to the user load.

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