TWI699955B - Power conversion system and control method thereof - Google Patents

Abstract

The invention discloses a power conversion system and the control method thereof, and the invention belongs to a field of circuit conversion technology. The system comprises a bridge switching circuit, the bridge switching circuit comprises a plurality of switch sub circuits, each of which comprises: a change-over switch for controlling the on/off of the switch sub circuit; a control unit, configured to execute the following cycles of commands: when the voltage between the change-over switch and the cathode is smaller than the first threshold voltage and the switch sub circuits are not charged, the control unit controls the change-over switch to be on, and enters into the mode which is allowed to charge, after that the switch sub circuit is charged; when the voltage between the change-over switch and the cathode is larger than the second threshold voltage, the control unit controls the change-over switch to be off; when the charging voltage of the control unit is larger than the third threshold voltage, the control unit stop charging the switch sub circuit. The beneficial effect of the invention is that, the structure of the circuit is simple, so that the circuit power loss of the bridge rectifier is reduced.

Description

Power conversion system and control method

The invention relates to the technical field of circuit conversion, in particular to a power conversion system and a control method.

The AC/DC power converter is a power conversion device that converts alternating current (AC) into direct current (DC). In AC/DC power converters, bridge rectifier circuits are often used as AC/DC power conversion systems.

However, the structure of the existing bridge rectifier circuit is relatively complicated, and the loss of the circuit conversion energy is relatively large. For example, a bridge rectifier disclosed in the US published patent document US9843251 needs to use a signal external to the bridge circuit to drive the gate of the bridge switch. The circuit structure is relatively complicated and the construction cost is relatively high. Another example is a bridge rectifier disclosed in the US published patent document US8804389, in which the bridge rectifier circuit needs to be charged in an ultra-high voltage environment, and switches are switched multiple times in the high voltage environment, thereby causing a large amount of useless circuit energy loss. In other words, in the existing technical solutions, the bridge rectifier circuit usually performs some useless switching during the alternating current cycle, and the charging process is usually carried out in the high voltage cycle, which leads to increased circuit energy loss and increased circuit operating costs. .

According to the above-mentioned problems existing in the prior art, a technical solution of a power conversion system and a control method is now provided, which aims to reduce the circuit energy loss of the power conversion system and simplify the circuit structure. The above technical solution specifically includes: a power conversion system, which includes a bridge switch circuit, the input end of the bridge switch circuit is connected to the AC input end of the power conversion system, and the output end of the bridge switch circuit is respectively connected to the power supply The DC output terminal of the conversion system; the bridge switch circuit includes a plurality of switch sub-circuits, the anode of each switch sub-circuit is connected to one of the AC input terminal and the DC output terminal, and the cathode of each switch sub-circuit Connected to the other of the AC input terminal and the DC output terminal; each switch sub-circuit includes: a transfer switch, connected between the anode and the cathode of the switch sub-circuit, for controlling the on-off of the switch sub-circuit; The control unit is connected to the transfer switch, and the control unit is configured to execute the following control cycle: when the voltage between the transfer switch and the cathode is less than a preset first voltage threshold and the control unit does not perform the switch When the circuit is charged, the control unit controls the transfer switch to turn on, and after the transfer switch is turned on, the control unit enters an allowable charging mode, in which the control unit is allowed to charge the switch sub-circuit ; When the voltage between the switch and the cathode is greater than a preset second voltage threshold, the control unit controls the switch to turn off; and when the charging voltage of the control unit is greater than a preset third voltage valve When the value is reached, the control unit stops charging the switch sub-circuit.

Preferably, the power conversion system, wherein the conversion switch is formed by a first MOS tube, the drain of the first MOS tube is connected to the anode of the switch sub-circuit, the source is connected to the cathode of the switch sub-circuit, and the gate is connected The control unit; a parasitic diode is also connected across the source and drain of the first MOS tube.

Preferably, in the power conversion system, the first MOS transistor is an NMOS transistor.

Preferably, in the power conversion system, the gate voltage of the first MOS transistor is clamped to a fixed voltage value.

Preferably, in the power conversion system, the control unit includes: a detection terminal connected between the first MOS tube and the cathode of the switch sub-circuit, and is used to detect whether the first MOS tube and the switch sub-circuit The crossover voltage between the cathodes; a switch control module, the switch control module is respectively connected to the detection terminal and the control terminal of the first MOS tube, used to: compare the crossover voltage with the first voltage threshold, When the crossover voltage is less than the first voltage threshold and the control unit does not charge the switch sub-circuit, the switch control module controls the first MOS transistor to be turned on through the control terminal of the first MOS transistor; and The jumper voltage is compared with the second voltage threshold, and when the jumper voltage is greater than the second voltage threshold, the switch control module controls the first MOS transistor to turn off through the control terminal of the first MOS transistor; The control module is connected to the switch control module, and is used to enter the allowable charging mode after the switch control module controls the first MOS tube to be turned on, and stop charging when the charging voltage reaches the third voltage threshold.

Preferably, in the power conversion system, the switch control module is implemented by a comparator; The non-inverting input terminal of the comparator is connected to a reference voltage module preset with the first voltage threshold and the second voltage threshold; the inverting input terminal of the comparator is connected to the detection terminal; the output terminal of the comparator Connect the control terminal of the switch.

Preferably, in the power conversion system, the value range of the first voltage threshold is -450mV~-100mV.

Preferably, in the power conversion system, the first voltage threshold is preferably -250 mV.

Preferably, in the power conversion system, the second voltage threshold has a value range of 0mV-10mV.

Preferably, in the power conversion system, the second voltage threshold is preferably 1 mV.

Preferably, the power conversion system, wherein the detection terminal is implemented by a second MOS tube, the drain of the second MOS tube is connected between the conversion switch and the cathode of the switch sub-circuit, and the source is connected to the switch The control module, the gate is connected to the charging control module; the second MOS tube keeps always on.

Preferably, in the power conversion system, the second MOS transistor is a PMOS transistor.

Preferably, in the power conversion system, the charging control module includes: a charging control chip, a control terminal of the charging control chip is connected to the gate of the second MOS tube, and a charging terminal of the charging control chip is connected to a charging capacitor , The other end of the charging capacitor is connected between the changeover switch and the anode of the switch sub-circuit, and an output end of the charging control chip is connected to the inverting input end of the comparator; After the switch is turned on, the charging control chip charges the charging capacitor through the charging terminal. When the charging voltage of the charging terminal is greater than the third voltage threshold, the charging control chip stops charging.

Preferably, in the power conversion system, the third voltage threshold is 15.6V.

A control method of a power conversion system, which is applied to the above-mentioned power conversion system, wherein each switch sub-circuit has the following control process: Step S1, using the control unit to perform the voltage between the conversion switch and the cathode Real-time detection; step S2, the control unit compares the detected voltage with a preset first voltage threshold, and when the detected voltage is less than the first voltage threshold, go to step S3; step S3, the control The unit controls the transfer switch to turn on, the control unit enters the charging mode, and then starts to charge the switch sub-circuit; step S4, the control unit compares the detected voltage with a preset second voltage threshold, and When the detected voltage is greater than the second voltage threshold, go to step S5; step S5, the control unit controls the switch to turn off; step S6, when the charging voltage output by the control unit is greater than a preset third voltage valve When the value is reached, the control unit stops charging and returns to step S2.

The beneficial effect of the above technical solution is that the circuit structure is simple, and the circuit energy loss of the bridge rectifier can be reduced.

A: Bridge switch circuit

A1: Input terminal

A2: Output

A3: Switch sub-circuit

B: External load

C1: Electrolytic capacitor

Vin: AC input

Line: FireWire

Neurual: neutral line

Anode: anode

Cathnode: Cathode

A31: Transfer switch

A32: Control unit

A321: Detection end

A322: Switch control module

A323: Charging control module

Vcc Charge: charge control chip

C2: Charging capacitor

Ref: Reference voltage module

CP: Comparator

M1: The first MOS tube

M2: Second MOS tube

Vcc: charging voltage

MUX1: the first data selector

MUX2: the second data selector

Figure 1 is a schematic diagram of the overall structure of a power conversion system in a preferred embodiment of the present invention; 2 is a schematic diagram of a simplified circuit structure of a power conversion system in a preferred embodiment of the present invention; FIG. 3 is a schematic diagram of a switch sub-circuit module in a preferred embodiment of the present invention; FIG. 4 is a comparative diagram of the present invention In a preferred embodiment, the working sequence diagram of the power conversion system; Fig. 5 is a schematic diagram of the circuit structure of the switch sub-circuit in a preferred embodiment of the present invention; Fig. 6 is a schematic diagram of the charging control in a preferred embodiment of the present invention The schematic diagram of the circuit structure of the chip; FIG. 7 is a schematic diagram of the structure of combining the first MOS transistor and the second MOS transistor to form a circuit element in a preferred embodiment of the present invention; FIG. 8 is a schematic diagram of a preferred embodiment of the present invention, A schematic flow chart of a control method of a power conversion system.

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other if there is no conflict.

The present invention will be further described below in conjunction with the drawings and specific embodiments, but it is not a limitation of the present invention.

According to the above-mentioned problems in the prior art, a technical solution of a power conversion system is now provided. The power conversion system is suitable for use in an AC/DC power converter and specifically includes a bridge switch circuit, the input end of the bridge switch circuit is connected to The AC input terminal of the power conversion system and the output terminal of the bridge switch circuit are respectively connected to the DC output terminal of the power conversion system; the bridge switch circuit includes a plurality of switch sub-circuits, and the anode of each switch sub-circuit is connected to the AC input terminal and One of the DC output terminals, the cathode of each switch sub-circuit is respectively connected to the other of the AC input terminal and the DC output terminal; each switch sub-circuit includes: a transfer switch, which is connected between the anode and the cathode of the switch sub-circuit , Used to control the on and off of the switch sub-circuit; the control unit, connected to the transfer switch, the control unit is configured to perform the following control cycle: when the voltage between the transfer switch and the cathode is less than a preset first voltage threshold and control When the unit is not charging the switch sub-circuit, the control unit controls the transfer switch to turn on, and after the transfer switch is turned on, the control unit enters an allowable charging mode, and the control unit is allowed to charge the switch sub-circuit; when the transfer switch is between the cathode When the voltage between the control unit is greater than a preset second voltage threshold, the control unit controls the transfer switch to turn off; and when the charging voltage of the control unit is greater than a preset third voltage threshold, the control unit stops charging the switch sub-circuit.

Specifically, in this embodiment, as shown in FIG. 1, the power conversion system includes a bridge switch circuit A. The input terminal A1 of the bridge switch circuit A is connected to the external AC power input terminal Vin. The output terminal A2 of the bridge switch circuit A is used as the DC output terminal of the power conversion system, and the DC output terminal A2 is connected to Into an external load B, and used to output the converted direct current to the external load B. At the same time, an electrolytic capacitor C1 is also connected between the DC output terminal A2, and the electrolytic capacitor C1 plays a role of power supply filtering, which will not be repeated here.

The bridge switch circuit A includes a plurality of switch sub-circuits A3, specifically in FIG. 1 includes four switch sub-circuits A3 connected in a bridge type, each of the switch sub-circuit A3 has the same structure and control logic, and the switch The sub-circuits A3 are independent of each other, and their control logic is not affected by other switch sub-circuits A3.

The above-mentioned bridge circuit A can also be simplified to the circuit structure in FIG. 2. In this circuit structure, each switch sub-circuit A3 only switches once in an alternating current cycle. The specific principle will be described in detail below.

As shown in Figure 3, the description is made for a single switch sub-circuit. The switch sub-circuit A1 specifically includes: a transfer switch A31, connected between the anode (Anode) and the cathode (Cathnode) of the switch sub-circuit A3, for controlling the switch sub-circuit The on and off of the circuit A3; the control unit A32 is connected to the switch A31, and the control unit A32 is configured to execute the following control cycle: when the voltage between the switch A31 and the cathode is less than a preset first voltage threshold and the control unit When the switch sub-circuit is not charged, the control unit A32 controls the transfer switch to turn on, and after the transfer switch A31 is turned on, the control unit A32 enters the charging mode, and then starts to charge the switch sub-circuit A3; when the transfer switch A31 and When the voltage between the cathodes is greater than a preset second voltage threshold, the control unit A32 controls the switch to turn off; and when the charging voltage of the control unit A32 is greater than a preset third voltage threshold, the control unit A32 stops The switch sub-circuit A3 is charged.

Specifically, each switch sub-circuit A3 described above is provided with a control unit A32 and a transfer switch A31. The transfer switch A31 is used to control the on-off of the switch sub-circuit A3, and the control unit A32 is used to control the on-off of the transfer switch A31. , Thereby controlling the on-off of the entire switch sub-circuit A3.

In an alternating current cycle, the control unit A32 first detects the voltage between the changeover switch A31 and the cathode, and determines whether it is less than a preset first voltage threshold (the first voltage threshold is a negative voltage), when the voltage is less than At the first voltage threshold (in the negative half cycle of AC power at this time), the control unit A32 controls the transfer switch A31 to turn on. At this time, the switch subcircuit A3 is turned on, and the control unit A32 enters the charging mode, and Then, the switch sub-circuit A3 is charged, so the charging process is performed in a low-voltage environment, which can reduce the circuit energy loss during charging. Since the charging of the control unit A32 and the turning on of the changeover switch A31 do not necessarily occur at the same time, generally speaking, the control unit A32 starts to charge the switch sub-circuit A3 after the changeover switch A31 is turned on. Therefore, in the present application, when the transfer switch A31 is turned on, the control unit A32 enters the allowable charging mode, which means that the control unit A32 can charge the switch sub-circuit A3 later.

At the same time, the control unit A32 continues to detect the voltage between the changeover switch A31 and the cathode. Since the changeover switch A31 is already turned on at this time, the control unit A32 actually detects the voltage between the anode and the cathode of the switch sub-circuit A3, and judges it. Whether it is greater than a preset second voltage threshold (the second voltage threshold is a positive voltage), when the voltage is greater than the second voltage threshold (in the positive half cycle of the alternating current), the control unit A32 controls the switch A31 is closed. At the same time, when the charging voltage of the control unit A32 to the switch sub-circuit A3 is greater than a preset third voltage threshold (the third voltage threshold is a positive voltage), the control unit A32 stops charging the switch sub-circuit A3, and the switch sub-circuit A3 The circuit A3 enters the discharge phase. Subsequently, the control unit A32 continues to detect the voltage between the changeover switch A31 and the cathode, and waits for it to be less than the first voltage threshold.

The above process is executed cyclically, so that each switch sub-circuit A3 forms a cycle of switching on → starting charging → turning off the transfer switch → stopping charging → turning on the transfer switch. In this way, the switching sub-circuit A3 has multiple state changes (multiple bursts) during operation, which can reduce the energy loss of the circuit.

Moreover, in the above process, each switch sub-circuit A3 only opens and closes once in an alternating current cycle, and the charging process is always performed in a low-voltage environment, which can also reduce circuit energy loss.

The above process can also be seen through the timing diagram in Figure 4. In Figure 4, curve 41 is used to represent the line voltage change in single-phase alternating current, curve 42 is used to represent the neutral line voltage change in single-phase alternating current, and curve 43 is used to represent the on-off of the transfer switch The curve 44 is used to indicate the change of the charging control of the control unit. Then: at time T0, the control unit detects that the voltage is less than the preset first voltage threshold. At this time, it is in the negative half cycle of the alternating current, the transfer switch is turned on, the control unit enters the charging mode, and then starts charging; T0-T1 At time, when the switch is in the on state, the control unit detects the current flow between the anode and the cathode in real time; at time T1, the current flow changes, and the control unit detects that the voltage is greater than the preset second voltage threshold. In the positive half cycle of alternating current, the transfer switch is closed; at time T1-T2, the transfer switch is in the off state, the blocking voltage in the switch sub-circuit A3 increases, and the control unit continues to charge the switch sub-circuit A3; at T2 At time, the charging voltage Vcc output by the control unit is greater than the third voltage threshold, and the control unit stops charging; at time T2-T0, at this time, the transfer switch is in the off state and the control unit is also in the state of stopping charging. The control unit detects whether the voltage is in real time It is less than the preset first voltage threshold, and returns to T0 when it is less than the first voltage threshold, so as to implement the circuit operation process at the time T0-T2 cyclically.

In a preferred embodiment of the present invention, as shown in FIGS. 3 and 5, the above-mentioned transfer switch A31 is formed by a first MOS tube M1, the drain of the first MOS tube M1 is connected to the anode of the switch sub-circuit, and the source is connected The cathode and the gate of the switch sub-circuit are connected to the control unit A32; a parasitic diode D1 is also connected across the source and drain of the first MOS transistor M1.

Then the control unit A32 controls the first MOS transistor M1 to be turned on or off by controlling the gate voltage of the first MOS transistor M1.

The above-mentioned first MOS tube M1 is an NMOS tube.

In a preferred embodiment of the present invention, the gate voltage of the first MOS transistor is clamped to a fixed voltage value.

In a preferred embodiment of the present invention, as shown in FIG. 3, the above-mentioned control unit A32 includes: a detection terminal A321, connected between the first MOS tube and the cathode of the switch sub-circuit, for detecting and obtaining the first MOS tube The switch control module A322 and the switch control module A322 are respectively connected to the detection terminal and the control terminal of the first MOS tube to compare the jumper voltage with the first voltage threshold. , When the crossover voltage is less than the first voltage threshold and the control unit does not charge the switch sub-circuit, the switch control module A322 controls the first MOS transistor to be turned on through the control terminal of the first MOS transistor; and connects the crossover voltage to the second The voltage threshold is compared. When the crossover voltage is greater than the second voltage threshold, the switch control module A322 controls the first MOS tube to turn off through the control terminal of the first MOS tube; the charging control module A323 is connected to the switch control module A322 for After the switch control module A322 controls the first MOS tube to be turned on, it enters the allowable charging mode, then starts charging, and stops charging when the charging voltage reaches the third voltage threshold.

Specifically, the above-mentioned switch control module A322 is implemented by a comparator CP; the non-inverting input terminal of the comparator CP is connected to a reference voltage module Ref preset with a first voltage threshold and a second voltage threshold; the inverse of the comparator CP The phase input terminal is connected to the detection terminal A321; the output terminal of the comparator CP is connected to the control terminal of the transfer switch.

The detection terminal is implemented by a second MOS tube M2, the drain of the second MOS tube M2 is connected between the conversion switch and the cathode of the switch sub-circuit, the source is connected to the switch control module, and the gate is connected to the charging control module. The second MOS tube M2 remains always on, which is a PMOS tube.

The charging control module includes: a charging control chip Vcc Charge, a control terminal 3 of the charging control chip Vcc Charge is connected to the gate of the second MOS tube M2, a charging terminal 1 of the charging control chip Vcc Charge is connected to a charging capacitor C2, the charging capacitor The other end of C2 is connected between the change-over switch and the anode of the switch sub-circuit, and an output terminal 2 of the charge control chip Vcc Charge is connected to the output terminal of the comparator CP, so as to provide the first MOS transistor when the comparator CP outputs a high level. M1 provides a gate voltage, which is equivalent to the charging voltage Vcc output by the charging control chip; when the switch M1 is turned on, the charging control chip Vcc Charge charges the charging capacitor C2 through the charging terminal 1. When the charging voltage is greater than the third voltage threshold, the charging control chip stops charging.

Specifically, in this embodiment, the specific circuit structure of each switch sub-circuit A3 is as shown in FIG. 5. Among them, the first MOS tube M1 is used as the switch of the switch sub-circuit A3, its source and drain are respectively connected to the anode and the cathode of the switch sub-circuit A3, and the gate of the first MOS tube M1 (that is, the control terminal of the switch) is connected To the output terminal of the comparator CP, and the output terminal 2 of the charge control chip Vcc Charge is connected to the output terminal of the comparator CP. The non-inverting input terminal of the comparator CP is connected to a reference voltage module Ref. The reference voltage module Ref is provided with two reference voltages, a first voltage threshold and a second voltage threshold. Threshold, where the first voltage threshold is a negative voltage threshold and the second voltage threshold is a positive voltage threshold. A feedback terminal of the reference voltage module Ref is also connected to the output terminal of the comparator CP. The inverting input terminal of the comparator CP is connected to the source of a second MOS transistor M2, that is, the source of the second MOS transistor M2 serves as the input voltage of the inverting input terminal of the comparator CP.

Initially, the first MOS transistor M1 is in the off state. When the source and drain voltage of the second MOS transistor M2 is less than the first voltage threshold, the output of the comparator CP is high. At this time, the first MOS transistor M1 is turned on, and the output terminal 2 of the charge control chip Vcc Charge goes to The first MOS tube M1 provides a gate voltage for it to turn on, and at the same time the charging control chip Vcc Charge enters the charging mode, and then starts to charge the charging capacitor C2. Since charging has just started, the gate voltage of the second MOS transistor M2 is initially lower than the charging voltage Vcc, for example, 6V.

As time changes, the source and drain currents of the first MOS tube M1 start to reverse when the first MOS tube M1 is turned on. When the voltage at the inverting input terminal of the comparator CP is greater than the second voltage threshold, the output terminal of the comparator CP outputs a low voltage. Level, the first MOS tube M1 is turned off. At this time, the charge control chip Vcc Charge is still charging, and the gate voltage of the second MOS tube M2 is lower than the third voltage threshold, for example, 12V.

The charging control chip Vcc Charge stops charging until the charging control chip Vcc Charge continues to charge until its charging voltage is higher than a third voltage threshold. The control unit A32 continues to detect the voltage across the first MOS tube M1, and when the voltage at the inverting input terminal of the comparator CP is less than the first voltage threshold, the first MOS tube M1 is turned on again, and the above process is repeated.

It is worth noting that, during the above charging process, the charging current flows from the cathode Cathode through the source and drain of the second MOS tube M2 to the charging control chip Vcc Charger, so as to be provided to the charging control chip Vcc Charger for charging.

In a preferred embodiment of the present invention, the value range of the above-mentioned first voltage threshold can be set to -400mV to -100mV, more preferably -250mV.

In a preferred embodiment of the present invention, the value range of the above-mentioned second voltage threshold can be set to 0mV-10mV, more preferably, it can be set to 1mV.

In a preferred embodiment of the present invention, the above-mentioned third voltage threshold may be set to 15.6V.

Of course, in other embodiments of the present application, the appropriate value of the above threshold can be set according to the actual circuit conditions, which will not be repeated here. In a preferred embodiment of the present invention, the above-mentioned reference voltage module Ref is connected to the output terminal of the comparator CP through a feedback terminal, so that the reference voltage output by itself can be determined by the high and low level output of the output terminal of the comparator CP. Threshold. For example, when the output of the comparator CP is at a high level (for example, Vcc), the reference voltage module Ref outputs the first voltage threshold, that is, the first voltage threshold is compared with the source-drain voltage of the second MOS tube M2; When the output of the converter CP is a low level (for example, 0V), the reference voltage module Ref outputs a second voltage threshold, that is, compares the second voltage threshold with the source-drain voltage of the second MOS transistor M2.

In addition, in order to cope with the problem of switching power supply, some necessary opening and closing conditions are set for the above process, for example: when the voltage of the charge control chip Vcc Charge is less than the fourth voltage threshold (for example, 13V) and the switch sub-circuit has been triggered. When the voltage is locked, the charge control chip Vcc Charge also starts charging.

When the voltage across the first MOS transistor M1 triggers the under-voltage lockout of the switch sub-circuit, the first MOS transistor M1 is turned off.

Figure 6 shows the internal circuit structure of the charge control chip Vcc Charger: two data selectors are provided in the charge control chip Vcc Charger. The two input terminals of the first data selector MUX1 are respectively connected to the reference voltage of the third voltage threshold (here set to 15.6V) and the fourth voltage threshold (here set to 13V), and the output terminal is connected to a comparison The inverting input terminal of CP2.

The source-drain voltage of the second MOS transistor M2 is connected to the inverting input terminal of the comparator CP, and at the same time is connected to the non-inverting input terminal of the comparator CP2 through a diode. The charging terminal 1 of the charging control chip Vcc Charger is drawn from the non-inverting input terminal of the comparator CP2.

The output terminal of the aforementioned comparator CP2 is reversed by a NOR circuit and then introduced into the first input terminal of a NOR circuit. The second input terminal of the NOR circuit is connected to the gate of the first MOS transistor M1 (that is, The output terminal 2) of the charging control chip Vcc Charger. The output terminal of the NOR circuit is simultaneously connected to the control terminal of the first data selector MUX1 and the control terminal of the second data selector MUX2.

The two input terminals of the second data selector MUX2 are connected to the reference voltage 8V and the charging voltage Vcc, respectively, and the output terminal is connected to the gate of the second MOS transistor M2 to provide the gate voltage required for its turn-on.

Specifically, based on the internal circuit structure of the charging control chip Vcc Charger, the working principle of the first data selector MUX1 depends on the level change of the control terminal of the first data selector MUX1:

Only when the input signal of the first input terminal of the NOR circuit (that is, the output signal of the comparator CP2) is 1 (logic high) and the second input terminal of the NOR circuit (that is, the first MOS transistor M1 When the gate voltage) is also 1 (logic high), the output terminal of the NOR circuit outputs a first selection signal. At this time, the first data selector MUX1 selects 13.6V to output according to the first selection signal.

In other cases, the output terminal of the NOR circuit outputs a second selection signal, and the first data selector MUX1 selects 15V to output according to the second selection signal.

Similarly, when the output terminal of the NOR circuit outputs the first selection signal, the second data selector MUX2 selects 8V output according to the first selection signal; when the output terminal of the NOR circuit outputs the second selection signal, The second data selector MUX2 selects the Vcc output according to the second selection signal Out. The function of the aforementioned reference voltage of 8V is to clamp the maximum value of the charging voltage of the second MOS transistor M2 to prevent it from being charged to Vcc.

In the preferred embodiment of the present invention, the above-mentioned first MOS transistor M1 and second MOS transistor M2 can also be combined to form a circuit element (as shown in FIG. 7). The control principle of the circuit element is the same as the above. No longer.

To sum up, in the technical solution of the present invention, for a single switch sub-circuit A3, through the mutual cooperation of the transfer switch A31 and the control unit A32, the transfer switch A31 is only switched once in an alternating current cycle, and the switch sub-circuit A3 The charging process is only performed in a low-voltage environment, so that the circuit energy loss of the entire power conversion system is reduced, and the circuit is simple to implement, and the implementation cost is low.

In a preferred embodiment of the present invention, based on the power conversion system described above, a method for controlling the power conversion system is now provided. As shown in FIG. 8, the method includes: step S1, using a control unit to connect the conversion switch and The voltage between the cathodes is detected in real time; step S2, the control unit compares the detected voltage with a preset first voltage threshold, and when the detected voltage is less than the first voltage threshold, go to step S3; step S3, the control unit controls the changeover switch to turn on, the control unit enters the charging mode, and then starts charging the switch sub-circuit; step S4, the control unit compares the detected voltage with a preset second voltage threshold, And when the detected voltage is greater than the second voltage threshold, go to step S5; step S5, the control unit controls the changeover switch to turn off; step S6, when the charging voltage output by the control unit is greater than a preset third voltage threshold, The control unit stops charging and returns to step S2.

The above descriptions are only preferred embodiments of the present invention, and do not limit the implementation and protection scope of the present invention. For those skilled in the art, they should be able to realize that all equivalents made using the description and illustrations of the present invention are equivalent. The solutions obtained by substitutions and obvious changes should all be included in the protection scope of the present invention.

A: Bridge switch circuit

A1: Input terminal

A2: Output

A3: Switch sub-circuit

B: External load

C1: Electrolytic capacitor

Vin: AC input

Claims (16)

A power conversion system includes a bridge switch circuit, the input end of the bridge switch circuit is connected to the AC input end of the power conversion system, and the output ends of the bridge switch circuit are respectively connected to the DC output end of the power conversion system: the The bridge switch circuit includes a plurality of switch sub-circuits. The anode of each switch sub-circuit is connected to one of the AC power input terminal and the DC output terminal. The cathode of each switch sub-circuit is connected to the AC power input terminal and the DC output terminal. The other one of the DC output terminals; each switch sub-circuit includes: a transfer switch, connected between the anode and the cathode of the switch sub-circuit, for controlling the on-off of the switch sub-circuit; a control unit, connected to the transfer switch, The control unit is configured to execute the following control cycle: when the voltage between the changeover switch and the cathode is less than a preset first voltage threshold and the control unit does not charge the switch sub-circuit, the control unit controls The transfer switch is turned on, and after the transfer switch is turned on, the control unit enters an allowable charging mode. In the allowed charging mode, the control unit is allowed to charge the switch sub-circuit; when the transfer switch and the cathode When the voltage between the control unit is greater than a preset second voltage threshold, the control unit controls the switch to turn off; and when the charging voltage of the control unit is greater than a preset third voltage threshold, the control unit stops The switch sub-circuit is charged; each switch sub-circuit is independent of each other, and its control logic is not affected by other switch sub-circuits. In an alternating current cycle, each switch sub-circuit only switches once. The power conversion system described in item 1 of the scope of patent application, wherein the conversion switch It is formed by using a first MOS tube, the drain of the first MOS tube is connected to the anode of the switch sub-circuit, the source is connected to the cathode of the switch sub-circuit, and the gate is connected to the control unit; on the source of the first MOS tube A parasitic diode is also connected across the drain and drain. The power conversion system described in item 2 of the scope of patent application, wherein the first MOS transistor is an NMOS transistor. The power conversion system described in item 2 of the scope of patent application, wherein the gate voltage of the first MOS transistor is clamped to a fixed voltage value. For the power conversion system described in item 2 of the scope of patent application, the control unit includes: a detection terminal connected between the first MOS tube and the cathode of the switch sub-circuit for detecting and obtaining the first MOS tube And the voltage across the cathode of the switch sub-circuit; a switch control module, the switch control module is respectively connected to the detection terminal and the control terminal of the first MOS tube, for: the jump voltage and the first voltage The threshold value is compared. When the crossover voltage is less than the first voltage threshold value and the control unit is not charging the switch sub-circuit, the switch control module controls the first MOS transistor through the control terminal of the first MOS transistor. And compare the crossover voltage with the second voltage threshold. When the crossover voltage is greater than the second voltage threshold, the switch control module controls the first MOS tube through the control terminal of the first MOS tube. A MOS tube is turned off; a charging control module, connected to the switch control module, is used to enter the allowable charging mode after the switch control module controls the first MOS tube to be turned on, and stop when the charging voltage reaches the third voltage threshold Recharge. For the power conversion system described in item 5 of the scope of patent application, the switch control module is implemented by a comparator; the non-inverting input terminal of the comparator is connected to a preset with the first voltage threshold and the second voltage Threshold reference voltage module; the inverting input terminal of the comparator is connected to the detection terminal; the output terminal of the comparator is connected to the control terminal of the transfer switch. For the power conversion system described in item 1 of the scope of patent application, the first voltage threshold has a value range of -450mV~-100mV. The power conversion system described in item 7 of the scope of patent application, wherein the first voltage threshold is preferably -250mV. For the power conversion system described in item 1 of the scope of the patent application, the second voltage threshold has a value range of 0mV-10mV. According to the power conversion system described in item 9 of the scope of patent application, the second voltage threshold is preferably 1 mV. The power conversion system described in item 6 of the scope of patent application, wherein the detection terminal is realized by a second MOS tube, and the drain of the second MOS tube is connected between the conversion switch and the cathode of the switch sub-circuit, The source is connected to the switch control module, and the gate is connected to the charging control module; the second MOS tube is kept on. For the power conversion system described in item 11 of the scope of patent application, the second MOS transistor is a PMOS transistor. For the power conversion system described in item 11 of the scope of patent application, the charging control module includes: A charging control chip, a control end of the charging control chip is connected to the gate of the second MOS transistor, a charging end of the charging control chip is connected to a charging capacitor, and the other end of the charging capacitor is connected to the transfer switch and the switch Between the anodes of the circuit, an output terminal of the charging control chip is connected to the inverting input terminal of the comparator; when the switch is turned on, the charging control chip charges the charging capacitor through the charging terminal. When the charging voltage is greater than the third voltage threshold, the charging control chip stops charging. For the power conversion system described in item 13 of the scope of patent application, the third voltage threshold is 15.6V. A control method for a power conversion system is applied to the power conversion system as described in any one of items 1 to 14 in the scope of the patent application, wherein the following control process is provided for each switch sub-circuit; step S1, adopts the The control unit detects the voltage between the switch and the cathode in real time; step S2, the control unit compares the detected voltage with a preset first voltage threshold, and when the detected voltage is less than the first voltage threshold When a voltage threshold is reached, go to step S3; step S3, the control unit controls the switch to turn on, and at the same time the control unit starts to charge the switch sub-circuit; step S4, the control unit compares the detected voltage with a preset The second voltage threshold is compared, and when the detected voltage is greater than the second voltage threshold, go to step S5; in step S5, the control unit controls the switch to turn off. Step S6, when the charging voltage output by the control unit is greater than a preset third voltage threshold, the control unit stops charging and returns to step S2.

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