CN112421971A - Power supply conversion system and control method - Google Patents

Power supply conversion system and control method Download PDF

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Publication number
CN112421971A
CN112421971A CN201910775224.2A CN201910775224A CN112421971A CN 112421971 A CN112421971 A CN 112421971A CN 201910775224 A CN201910775224 A CN 201910775224A CN 112421971 A CN112421971 A CN 112421971A
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China
Prior art keywords
switch
voltage
circuit
charging
control unit
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CN201910775224.2A
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Chinese (zh)
Inventor
陈铭学
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Alpha and Omega Semiconductor Cayman Ltd
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Alpha and Omega Semiconductor Cayman Ltd
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Priority to CN201910775224.2A priority Critical patent/CN112421971A/en
Publication of CN112421971A publication Critical patent/CN112421971A/en
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M7/219—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only in a bridge configuration
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0048—Circuits or arrangements for reducing losses
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Charge And Discharge Circuits For Batteries Or The Like (AREA)

Abstract

The invention discloses a power supply conversion system and a control method, and belongs to the technical field of circuit conversion. The system includes a bridge switching circuit including a plurality of switching sub-circuits, each switching sub-circuit including: the change-over switch is used for controlling the on-off of the switch sub-circuit; a control unit configured to execute the following control loop: when the voltage between the change-over switch and the cathode is smaller than a first voltage threshold and the switch sub-circuit is not charged, the control unit controls the change-over switch to be switched on and enters a charging allowing mode, and then the switch sub-circuit is charged; when the voltage between the change-over switch and the cathode is larger than a second voltage threshold value, the control unit controls the change-over switch to be closed; when the charging voltage of the control unit is larger than the third voltage threshold, the control unit stops charging the switch sub-circuit. The beneficial effects of the above technical scheme are: the circuit structure is simple, and the circuit energy loss of the bridge rectifier can be reduced.

Description

Power supply conversion system and control method
Technical Field
The invention relates to the technical field of circuit conversion, in particular to a power conversion system and a control method.
Background
An AC/DC power converter is a power conversion device that converts Alternating Current (AC) into Direct Current (DC). Bridge rectifier circuits are often used in AC/DC power converters as AC/DC power conversion systems.
However, the existing bridge rectifier circuit is relatively complex in structure, and the loss of the conversion energy of the circuit is large. For example, the patent document US9843251 discloses a bridge rectifier, which needs to use signals outside the bridge circuit to drive the gate of the bridge switch, and the circuit structure is complicated and the construction cost is high. Also for example, U.S. published patent document US8804389 discloses a bridge rectifier, in which a bridge rectifier circuit needs to be charged in an ultra-high voltage environment and switches many times in a high voltage environment, resulting in a large amount of useless circuit energy loss. In other words, in the prior art, the bridge rectifier circuit usually performs some useless switching in the ac cycle, and the charging process is usually performed in the high-voltage cycle, thereby increasing the energy loss of the circuit and increasing the operating cost of the circuit.
Disclosure of Invention
In light of the above problems in the prior art, a technical solution of a power conversion system and a control method is provided to reduce the circuit energy loss of the power conversion system and simplify the circuit structure. The technical scheme specifically comprises the following steps:
a power conversion system comprises a bridge type switch circuit, wherein the input end of the bridge type switch circuit is connected with the alternating current input end of the power conversion system, and the output end of the bridge type switch circuit is respectively connected with the direct current output end of the power conversion system;
the bridge type switching circuit comprises a plurality of switching sub-circuits, wherein the anode of each switching sub-circuit is respectively connected with one of the alternating current input end and the direct current output end, and the cathode of each switching sub-circuit is respectively connected with the other of the alternating current input end and the direct current output end;
each of the switch sub-circuits includes:
the change-over switch is connected between the anode and the cathode of the switch sub-circuit and is used for controlling the on-off of the switch sub-circuit;
a control unit connected to the transfer switch, the control unit configured to perform the following control cycle:
when the voltage between the change-over switch and the cathode is smaller than a preset first voltage threshold and the control unit does not charge the switch sub-circuit, the control unit controls the change-over switch to be switched on, and after the change-over switch is switched on, the control unit enters a charging allowing mode, and in the charging allowing mode, the control unit is allowed to charge the switch sub-circuit;
when the voltage between the change-over switch and the cathode is larger than a preset second voltage threshold value, the control unit controls the change-over switch to be closed; and
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.
Preferably, in the power conversion system, the transfer switch is formed by using a first MOS transistor, a drain of the first MOS transistor is connected to an anode of the switch sub-circuit, a source of the first MOS transistor is connected to a cathode of the switch sub-circuit, and a gate of the first MOS transistor is connected to the control unit;
and a parasitic diode is also connected between the source electrode and the drain electrode of the first MOS tube in a bridging manner.
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 at a fixed voltage value.
Preferably, the power conversion system, wherein the control unit includes:
the detection end is connected between the first MOS tube and the cathode of the switch sub-circuit and is used for detecting and obtaining the cross-over voltage between the first MOS tube and the cathode of the switch sub-circuit;
the switch control module is respectively connected with the detection end and the control end of the first MOS tube and is used for:
comparing the cross-over voltage with the first voltage threshold, and when the cross-over voltage is smaller than the first voltage threshold and the control unit does not charge the switch sub-circuit, controlling the first MOS transistor to be switched on by the switch control module through the control end of the first MOS transistor; and
comparing the cross-over voltage with the second voltage threshold, and controlling the first MOS transistor to be closed by the switch control module through the control end of the first MOS transistor when the cross-over voltage is greater than the second voltage threshold;
and the charging control module is connected with the switch control module and used for entering the charging permission mode after the switch control module controls the first MOS tube to be connected and stopping charging when the charging voltage reaches the third voltage threshold.
Preferably, in the power conversion system, the switch control module is implemented by using a comparator;
the positive phase input end of the comparator is connected with a reference voltage module preset with the first voltage threshold and the second voltage threshold;
the inverting input end of the comparator is connected with the detection end;
and the output end of the comparator is connected with the control end of the change-over switch.
Preferably, in the power conversion system, the first voltage threshold ranges from-450 mV to-100 mV.
Preferably, the power conversion system, wherein said first voltage threshold is preferably-250 mV.
Preferably, in the power conversion system, the value of the second voltage threshold ranges from 0mV to 10 mV.
Preferably, in the power conversion system, the second voltage threshold is preferably 1 mV.
Preferably, in the power conversion system, the detection end is implemented by using a second MOS transistor, a drain of the second MOS transistor is connected between the transfer switch and a cathode of the switch sub-circuit, a source is connected to the switch control module, and a gate is connected to the charge control module;
the second MOS tube is kept normally 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 control end of the charging control chip is connected with the grid electrode of the second MOS tube, a charging end of the charging control chip is connected with a charging capacitor, the other end of the charging capacitor is connected between the change-over switch and the anode of the switch sub-circuit, and an output end of the charging control chip is connected with the inverting input end of the comparator;
when the change-over switch is switched on, the charging control chip charges the charging capacitor through the charging end, and when the charging voltage of the charging end 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, wherein the control method is applied to the power conversion system, and the control method comprises the following control procedures for each switch sub-circuit:
step S1, detecting the voltage between the change-over switch and the cathode in real time by the control unit;
step S2, the control unit compares the detected voltage with a preset first voltage threshold and goes to step S3 when the detected voltage is less than the first voltage threshold;
step S3, the control unit controls the transfer switch to turn on, the control unit enters a charge-enabled 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 goes to step S5 when the detected voltage is greater than the second voltage threshold;
step S5, the control unit controls the changeover switch to be turned off;
in step S6, when the charging voltage outputted by the control unit is greater than a preset third voltage threshold, the control unit stops charging and returns to step S2.
The beneficial effects of the above technical scheme are: the circuit structure is simple, and the circuit energy loss of the bridge rectifier can be reduced.
Drawings
FIG. 1 is a schematic diagram of a power conversion system according to a preferred embodiment of the present invention;
FIG. 2 is a simplified circuit diagram of a power conversion system according to a preferred embodiment of the present invention;
FIG. 3 is a block diagram of a switch sub-circuit in accordance with a preferred embodiment of the present invention;
FIG. 4 is a timing diagram illustrating the operation of the power conversion system according to the preferred embodiment of the invention;
FIG. 5 is a circuit diagram of a switch sub-circuit according to a preferred embodiment of the present invention;
FIG. 6 is a schematic circuit diagram of a charging control chip according to a preferred embodiment of the present invention;
FIG. 7 is a schematic structural diagram of a circuit device formed by combining a first MOS transistor and a second MOS transistor according to a preferred embodiment of the present invention;
fig. 8 is a flowchart illustrating a control method of a power conversion system according to a preferred embodiment of the invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
The invention is further described with reference to the following drawings and specific examples, which are not intended to be limiting.
According to the above problems in the prior art, a technical solution of a power conversion system is provided, where the power conversion system is suitable for an AC/DC power converter, and specifically includes a bridge switch circuit, an input terminal of the bridge switch circuit is connected to an AC input terminal of the power conversion system, and output terminals of the bridge switch circuit are respectively connected to a DC output terminal of the power conversion system;
the bridge type switching circuit comprises a plurality of switching sub-circuits, wherein the anode of each switching sub-circuit is respectively connected with one of the alternating current input end and the direct current output end, and the cathode of each switching sub-circuit is respectively connected with the other of the alternating current input end and the direct current output end;
each switch sub-circuit comprises:
the change-over switch is connected between the anode and the cathode of the switch sub-circuit and is used for controlling the on-off of the switch sub-circuit;
a control unit connected to the transfer switch, the control unit configured to perform the following control cycle:
when the voltage between the change-over switch and the cathode is smaller than a preset first voltage threshold and the control unit does not charge the switch sub-circuit, the control unit controls the change-over switch to be switched on, and after the change-over switch is switched on, the control unit enters a charging allowing mode, and the control unit is allowed to charge the switch sub-circuit;
when the voltage between the change-over switch and the cathode is larger than a preset second voltage threshold value, the control unit controls the change-over switch to be closed; and
when the charging voltage of the control unit is larger than a preset third voltage threshold, the control unit stops charging the switch sub-circuit.
Specifically, in the embodiment, as shown in fig. 1, the power conversion system includes a bridge switch circuit a. The input terminal a1 of the bridge switching circuit a is connected to an external ac input terminal Vin. The output end a2 of the bridge switch circuit a serves as a dc output end of the power conversion system, and the dc output end a2 is connected to an external load B and is used for outputting the converted dc power to the external load B. Meanwhile, an electrolytic capacitor C1 is connected between the direct current output ends A2, and the electrolytic capacitor C1 plays a role in power supply filtering, which is not described in detail herein.
The bridge switch circuit a includes a plurality of switch sub-circuits A3, specifically includes 4 switch sub-circuits A3 connected in a bridge manner in fig. 1, the structure and control logic of each switch sub-circuit A3 are the same, and the switch sub-circuits A3 are independent of each other, and their control logic is not affected by other switch sub-circuits A3.
The bridge circuit a can also be simplified to the circuit configuration of fig. 2, in which each switch sub-circuit a3 is switched only once during an ac cycle, and the specific principle will be described in detail below.
As shown in fig. 3, the description is made for a single switch sub-circuit, and the switch sub-circuit a1 specifically includes:
the change-over switch A31 is connected between an Anode (Anode) and a cathode (cathode) of the switch sub-circuit A3 and is used for controlling the on-off of the switch sub-circuit A3;
control unit a32, connected to transfer switch a31, control unit a32 is configured to execute the following control loop:
when the voltage between the change-over switch A31 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 A32 controls the change-over switch to be turned on, and after the change-over switch A31 is turned on, the control unit A32 enters a charge-enabled mode and then starts to charge the switch sub-circuit A3;
when the voltage between the change-over switch A31 and the cathode is greater than a preset second voltage threshold, the control unit A32 controls the change-over switch to be closed; and
when the charging voltage of the control unit a32 is greater than a preset third voltage threshold, the control unit a32 stops charging the switch sub-circuit A3.
Specifically, each switch sub-circuit A3 is provided with a control unit a32 and a switch a31, the switch a31 is used for controlling the on/off of the switch sub-circuit A3, and the control unit a32 is used for controlling the on/off of the switch a31, so as to control the on/off of the entire switch sub-circuit A3.
During an ac power cycle, the control unit a32 first detects the voltage between the switch a31 and the cathode and determines whether it is smaller than a preset first voltage threshold (the first voltage threshold is a negative voltage), when the voltage is smaller than the first voltage threshold (in the negative half cycle of the ac power), the control unit a32 controls the switch a31 to be turned on, at this time, the switch sub-circuit A3 is turned on, and the control unit a32 enters a charge-enabled mode, and then charges the switch sub-circuit A3, so that the charging process is performed in a low voltage environment, and the circuit energy loss during charging can be reduced. Since the start of charging of the control unit a32 and the switching-on of the changeover switch a31 do not necessarily occur simultaneously, normally the control unit a32 only starts charging the switch sub-circuit A3 when the changeover switch a31 is switched on. In the present application, therefore, the control unit a32 enters the charge-enabled mode when the changeover switch a31 is switched on, i.e. means that the control unit a32 can then charge the switch sub-circuit A3.
At the same time, the control unit a32 continues to detect the voltage between the change-over switch a31 and the cathode, since the change-over switch a31 is 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 determines whether the voltage is greater than a preset second voltage threshold (the second voltage threshold is a positive voltage), and when the voltage is greater than the second voltage threshold (in the positive half-cycle of the alternating current at this time), the control unit a32 controls the change-over switch a31 to be turned off. Meanwhile, 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 enters a discharging phase. The control unit a32 then continues to detect the voltage between the transfer switch a31 and the cathode, waiting for it to be less than the first voltage threshold.
The above processes are executed circularly, so that each switch sub-circuit A3 forms a work flow of cyclic reciprocation of switch on → charging start → switch off → charging stop → switch on, thus the switch sub-circuit A3 has a plurality of state changes (bursts) during operation, and the circuit energy loss can be reduced.
In addition, in the process, each switch sub-circuit A3 is only opened and closed once in one alternating current period, the charging process is always carried out in a low-voltage environment, and the energy loss of the circuit can be reduced.
The above process can also be seen by the timing diagram in fig. 4. In fig. 4, a curve 41 is used to indicate a Line voltage change in the single-phase alternating current, a curve 42 is used to indicate a Neutral voltage change in the single-phase alternating current, a curve 43 is used to indicate an on-off change of the transfer switch, and a curve 44 is used to indicate a charging control change of the control unit. Then:
at the time T0, the control unit detects that the voltage is less than a preset first voltage threshold value, and is in an alternating current negative half cycle, the change-over switch is turned on, the control unit enters a charging allowing model, and then charging is started;
at the time of T0-T1, the change-over switch is in an on state, and the control unit detects the current flowing direction between the anode and the cathode in real time;
at the time T1, the current flow direction changes, the control unit detects that the voltage is greater than a preset second voltage threshold, and at this time, the alternating current positive half cycle is performed, and the change-over switch is turned off;
at time T1-T2, when the transfer switch is in an off state, the Blocking Voltage (Blocking Voltage) in the switch sub-circuit A3 increases, and the control unit continues to charge the switch sub-circuit A3;
at time T2, the control unit outputs a charging voltage Vcc greater than a third voltage threshold, and stops charging;
and at the time of T2-T0, the change-over switch is in an off state at the moment, the control unit is also in a state of stopping charging, and the control unit detects whether the voltage is smaller than a preset first voltage threshold value in real time and returns to the action of T0 when the voltage is smaller than the first voltage threshold value, so that the circuit operation process at the time of T0-T2 is executed circularly.
In the preferred embodiment of the present invention, as shown in fig. 3 and 5, the switch a31 is formed by a first MOS transistor M1, a drain of the first MOS transistor M1 is connected to an anode of the switch sub-circuit, a source is connected to a cathode of the switch sub-circuit, and a gate is connected to the control unit a 32;
a parasitic diode D1 is also connected across the source and drain of the first MOS transistor M1.
The control unit a32 controls the first MOS transistor M1 to turn on or off by controlling the gate voltage of the first MOS transistor M1.
The first MOS transistor M1 is an NMOS transistor.
In a preferred embodiment of the present invention, the gate voltage of the first MOS transistor is clamped at a fixed voltage value.
In a preferred embodiment of the present invention, as shown in fig. 3, the control unit a32 includes:
the detection end A321 is connected between the first MOS tube and the cathode of the switch sub-circuit and used for detecting and obtaining a cross-over voltage between the first MOS tube and the cathode of the switch sub-circuit;
switch control module A322, switch control module A322 connect the control end of sense terminal and first MOS pipe respectively for:
comparing the cross-over voltage with a first voltage threshold, and when the cross-over voltage is smaller than the first voltage threshold and the control unit does not charge the switch sub-circuit, controlling the first MOS transistor to be switched on by the switch control module A322 through the control end of the first MOS transistor; and
comparing the cross-over voltage with a second voltage threshold, and controlling the first MOS transistor to be closed by the switch control module A322 through the control end of the first MOS transistor when the cross-over voltage is greater than the second voltage threshold;
and the charging control module A323 is connected with the switch control module A322 and is used for entering a charging permission mode after the switch control module A322 controls the first MOS tube to be connected, then starting charging and stopping charging when the charging voltage reaches a third voltage threshold value.
Specifically, the switch control module a322 is implemented by a comparator CP;
the positive phase input end of the comparator CP is connected with a reference voltage module Ref preset with a first voltage threshold and a second voltage threshold;
the inverting input end of the comparator CP is connected with the detection end A321;
the output end of the comparator CP is connected with the control end of the change-over switch.
The detection end is realized by adopting a second MOS tube M2, the drain electrode of the second MOS tube M2 is connected between the change-over switch and the cathode of the switch sub-circuit, the source electrode is connected with the switch control module, and the grid electrode is connected with the charging control module. The second MOS transistor M2 remains normally on, and is a PMOS transistor.
The charging control module comprises:
a control end 3 of the charging control chip Vcc Charge is connected with a grid electrode of the second MOS transistor M2, a charging end 1 of the charging control chip Vcc Charge is connected with a charging capacitor C2, the other end of the charging capacitor C2 is connected between the change-over switch and the anode of the switch sub-circuit, an output end 2 of the charging control chip Vcc Charge is connected with the output end of the comparator CP, so as to provide a grid electrode voltage to the first MOS transistor M1 when the comparator CP outputs a high level, wherein the grid electrode voltage is equal to the charging voltage Vcc output by the charging control chip;
when the changeover switch M1 is turned on, the charging control chip Vcc Charge charges the charging capacitor C2 through the charging terminal 1, and when the charging voltage of the charging terminal 1 is greater than the third voltage threshold, the charging control chip stops charging.
Specifically, in the present embodiment, the specific circuit structure of each switch sub-circuit a3 is as shown in fig. 5. The first MOS transistor M1 is used as a transfer switch of the switch sub-circuit A3, the source and drain electrodes of the first MOS transistor M1 are respectively connected to the anode and the cathode of the switch sub-circuit A3, the gate electrode of the first MOS transistor M1 (i.e. the control terminal of the transfer switch) is connected to the output terminal of the comparator CP, and the output terminal 2 of the charging control chip Vcc Charge is connected to the output terminal of the comparator CP. The positive phase input end of the comparator CP is connected to a reference voltage module Ref, two reference voltage thresholds, namely a first voltage threshold and a second voltage threshold, are arranged in the reference voltage module Ref, wherein the first voltage threshold is a negative voltage threshold, the second voltage threshold is a positive voltage threshold, and a feedback end of the reference voltage module Ref is also connected to the output end of the comparator CP. The inverting input terminal of the comparator CP is connected to the source of a second MOS transistor M2, i.e. the source of the second MOS transistor M2 is used 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-drain voltage of the second MOS transistor M2 is less than the first voltage threshold, the output of the comparator CP is at a high level, at this time, the first MOS transistor M1 is turned on, the output terminal 2 of the charging control chip Vcc Charge provides the gate voltage to the first MOS transistor M1 for turning on, and at the same time, the charging control chip Vcc Charge enters the Charge-enabled mode and then starts to Charge the charging capacitor C2. Since the charging is started, the gate voltage of the second MOS transistor M2 is initially lower than the charging voltage Vcc, for example, 6V.
With time, the source-drain current of the first MOS transistor M1 starts to reverse, and 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 level, and the first MOS transistor M1 is turned off. At this time, the charging control chip Vcc Charge is still being charged, and the gate voltage of the second MOS transistor M2 is lower than the third voltage threshold, for example, 12V.
The charging control chip Vcc Charge does not stop 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 transistor M1, and when the voltage at the inverting input terminal of the comparator CP is smaller than the first voltage threshold, the first MOS transistor M1 is turned on again, and the above-mentioned process is performed in a loop.
It should be noted that in the charging process, a charging current flows from the Cathode to the charging control chip Vcc charge through the source-drain of the second MOS transistor M2, so as to be supplied to the charging control chip Vcc charge for charging.
In a preferred embodiment of the present invention, the value range of the first voltage threshold may be set to-400 mV to-100 mV, and more preferably may be set to-250 mV.
In a preferred embodiment of the present invention, the value of the second voltage threshold may be set to be in a range of 0mV to 10mV, and more preferably may be set to be 1 mV.
In a preferred embodiment of the present invention, the third voltage threshold may be set to 15.6V.
Of course, in other embodiments of the present application, a suitable value of the threshold may be set according to an actual circuit condition, and details are not described here. In a preferred embodiment of the present invention, the reference voltage module Ref is connected to the output end of the comparator CP through a feedback end, so that the output reference voltage threshold can be determined by the high-low level variation of the output end of the comparator CP. For example, when the output of the comparator CP is at a high level (e.g., Vcc), the reference voltage module Ref outputs a first voltage threshold, that is, the first voltage threshold is compared with the source-drain voltage of the second MOS transistor M2; when the output of the comparator CP is at a low level (e.g. 0V), the reference voltage module Ref outputs a second voltage threshold, that is, the second voltage threshold is compared with the source-drain voltage of the second MOS transistor M2.
In addition, in order to deal with the problem of the switching power supply, some necessary on-off conditions are set for the above process at the same time, such as:
when the voltage of the charging control chip Vcc Charge is less than the fourth voltage threshold (for example, 13V) and the under-voltage locking of the switch sub-circuit has been triggered, the charging control chip Vcc Charge also starts charging.
When the voltage across the first MOS transistor M1 triggers the under-voltage lock of the switch sub-circuit, the first MOS transistor M1 is turned off.
Fig. 6 shows an internal circuit configuration of the charge control chip Vcc charge:
two data selectors are provided in the charge control chip Vcc charge. The first data selector MUX1 has two inputs respectively connected to the reference voltages of the third voltage threshold (here set to 15.6V) and the fourth voltage threshold (here set to 13V), and an output connected to the inverting input of a comparator CP 2.
The source-drain voltage of the second MOS transistor M2 is connected to the inverting input terminal of the comparator CP, and 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 charge is led out from the non-inverting input terminal of the comparator CP 2.
The output terminal of the comparator CP2 is inverted by a not gate circuit and then introduced into a first input terminal of a nor gate, a second input terminal of the nor gate is connected to the gate of the first MOS transistor M1 (i.e., the output terminal 2 of the charging control chip Vcc charge), and an output terminal of the nor gate is connected to both the control terminal of the first data selector MUX1 and the control terminal of a second data selector MUX 2.
The two input terminals of the second data selector MUX2 are respectively connected to the reference voltage 8V and the charging voltage Vcc, 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 configuration of the charging control chip Vcc charge, the operating principle of the first data selector MUX1 varies depending on the level of the control terminal of the first data selector MUX 1:
the output terminal of the nor circuit outputs a first selection signal only when the input signal of the first input terminal of the nor circuit (i.e., the output signal of the comparator CP 2) is 1 (logic high level) and the second input terminal of the nor circuit (i.e., the gate voltage of the first MOS transistor M1) is also 1 (logic high level), and the first data selector MUX1 selects the 13.6V output according to the first selection signal.
In other cases, the output of the NOR gate outputs a second select signal, when the first data selector MUX1 selects the 15V output based on the second select signal.
Similarly, when the output terminal of the nor gate outputs the first selection signal, the second data selector MUX2 selects the 8V output according to the first selection signal; when the output of the nor gate outputs the second select signal, the second data selector MUX2 selects Vcc output according to the second select signal. The above-mentioned reference voltage 8V is used to clamp the maximum value of the charging voltage of the second MOS transistor M2, and prevent it from being charged to Vcc.
In a preferred embodiment of the present invention, the first MOS transistor M1 and the second MOS transistor M2 may also be combined to form a circuit element (as shown in fig. 7), and the control principle of the circuit element is the same as that described above, and therefore, the description thereof is omitted.
In summary, in the technical solution of the present invention, for a single switch sub-circuit A3, through the mutual cooperation of the switch a31 and the control unit a32, the switch a31 is switched only once in an ac power cycle, and the charging process of the switch sub-circuit A3 is performed only 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 has a low implementation cost.
In a preferred embodiment of the present invention, based on the power conversion system described above, a control method of the power conversion system is now provided, as shown in fig. 8, including:
step S1, detecting the voltage between the conversion switch and the cathode in real time by using a control unit;
step S2, the control unit compares the detected voltage with a preset first voltage threshold, and goes to step S3 when the detected voltage is less than the first voltage threshold;
step S3, the control unit controls the switch to be switched on, the control unit enters a charging permission mode, and then the switch sub-circuit is charged;
step S4, the control unit compares the detected voltage with a preset second voltage 1 threshold, and goes to step S5 when the detected voltage is greater than the second voltage threshold;
step S5, the control unit controls the change-over switch to be switched off;
in step S6, when the charging voltage outputted by the control unit is greater than a preset third voltage threshold, the control unit stops charging and returns to step S2.
While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.

Claims (15)

1. A power conversion system is characterized by comprising a bridge type switch circuit, wherein the input end of the bridge type switch circuit is connected with the alternating current input end of the power conversion system, and the output end of the bridge type switch circuit is respectively connected with the direct current output end of the power conversion system;
the bridge type switching circuit comprises a plurality of switching sub-circuits, wherein the anode of each switching sub-circuit is respectively connected with one of the alternating current input end and the direct current output end, and the cathode of each switching sub-circuit is respectively connected with the other of the alternating current input end and the direct current output end;
each of the switch sub-circuits includes:
the change-over switch is connected between the anode and the cathode of the switch sub-circuit and is used for controlling the on-off of the switch sub-circuit;
a control unit connected to the transfer switch, the control unit configured to perform the following control cycle:
when the voltage between the change-over switch and the cathode is smaller than a preset first voltage threshold and the control unit does not charge the switch sub-circuit, the control unit controls the change-over switch to be switched on, and after the change-over switch is switched on, the control unit enters a charging allowing mode, and in the charging allowing mode, the control unit is allowed to charge the switch sub-circuit;
when the voltage between the change-over switch and the cathode is larger than a preset second voltage threshold value, the control unit controls the change-over switch to be closed; and
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.
2. The power conversion system of claim 1, wherein the transfer switch is formed by a first MOS transistor, a drain of the first MOS transistor is connected to an anode of the switch sub-circuit, a source of the first MOS transistor is connected to a cathode of the switch sub-circuit, and a gate of the first MOS transistor is connected to the control unit;
and a parasitic diode is also connected between the source electrode and the drain electrode of the first MOS tube in a bridging manner.
3. The power conversion system of claim 2, wherein the first MOS transistor is an NMOS transistor.
4. The power conversion system of claim 2, wherein the gate voltage of the first MOS transistor is clamped at a fixed voltage level.
5. The power conversion system of claim 2, wherein the control unit comprises:
the detection end is connected between the first MOS tube and the cathode of the switch sub-circuit and is used for detecting and obtaining the cross-over voltage between the first MOS tube and the cathode of the switch sub-circuit;
the switch control module is respectively connected with the detection end and the control end of the first MOS tube and is used for:
comparing the cross-over voltage with the first voltage threshold, and when the cross-over voltage is smaller than the first voltage threshold and the control unit does not charge the switch sub-circuit, controlling the first MOS transistor to be switched on by the switch control module through the control end of the first MOS transistor; and
comparing the cross-over voltage with the second voltage threshold, and controlling the first MOS transistor to be closed by the switch control module through the control end of the first MOS transistor when the cross-over voltage is greater than the second voltage threshold; and the charging control module is connected with the switch control module and used for entering the charging permission mode after the switch control module controls the first MOS tube to be connected and stopping charging when the charging voltage reaches the third voltage threshold.
6. The power conversion system of claim 5, wherein the switch control module is implemented using a comparator;
the positive phase input end of the comparator is connected with a reference voltage module preset with the first voltage threshold and the second voltage threshold;
the inverting input end of the comparator is connected with the detection end;
and the output end of the comparator is connected with the control end of the change-over switch.
7. The power conversion system of claim 1, wherein the first voltage threshold ranges from-450 mV to-100 mV.
8. The power conversion system of claim 7, wherein the first voltage threshold is preferably-250 mV.
9. The power conversion system of claim 1, wherein the second voltage threshold has a value in a range of 0mV to 10 mV.
10. The power conversion system of claim 9, wherein the second voltage threshold is preferably 1 mV.
11. The power conversion system according to claim 6, wherein the detection terminal is implemented by a second MOS transistor, a drain of the second MOS transistor is connected between the transfer switch and a cathode of the switch sub-circuit, a source of the second MOS transistor is connected to the switch control module, and a gate of the second MOS transistor is connected to the charge control module;
the second MOS tube is kept normally on.
12. The power conversion system of claim 11, wherein the second MOS transistor is a PMOS transistor.
13. The power conversion system of claim 11, wherein the charge control module comprises:
a control end of the charging control chip is connected with the grid electrode of the second MOS tube, a charging end of the charging control chip is connected with a charging capacitor, the other end of the charging capacitor is connected between the change-over switch and the anode of the switch sub-circuit, and an output end of the charging control chip is connected with the inverting input end of the comparator;
when the change-over switch is switched on, the charging control chip charges the charging capacitor through the charging end, and when the charging voltage of the charging end is greater than the third voltage threshold, the charging control chip stops charging.
14. The power conversion system of claim 13, wherein the third voltage threshold is 15.6V.
15. A control method of a power conversion system, applied to the power conversion system according to any one of claims 1 to 14, characterized in that, for each of the switch sub-circuits, the following control procedures are provided:
step S1, detecting the voltage between the change-over switch and the cathode in real time by the control unit;
step S2, the control unit compares the detected voltage with a preset first voltage threshold and goes to step S3 when the detected voltage is less than the first voltage threshold;
step S3, the control unit controls the transfer switch to be turned 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 second voltage threshold and goes to step S5 when the detected voltage is greater than the second voltage threshold;
step S5, the control unit controls the changeover switch to be turned off;
in step S6, when the charging voltage outputted by the control unit is greater than a preset third voltage threshold, the control unit stops charging and returns to step S2.
CN201910775224.2A 2019-08-21 2019-08-21 Power supply conversion system and control method Pending CN112421971A (en)

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