阅读说明：本技术 反激电源中利用可控硅隔离控制大功率负载的电路及电器 (Circuit and electric appliance for isolating and controlling high-power load by using silicon controlled rectifier in flyback power supply ) 是由 汪军 何志明 陈文强 潘广泉 于 2020-06-12 设计创作，主要内容包括：本发明公开了反激电源中利用可控硅隔离控制大功率负载的电路及电器,包括高频变压器,吸收电路、次级输出电路、辅助供电电路、驱动电路和可控硅；所述辅助供电电路连接在所述高频变压器,且所述辅助供电电路两端接入交流相线输入和模拟地；所述驱动电路的输出端连接可控硅的G极,用于控制可控硅的导通,当反激电源启动时,所述辅助供电电路上具有持续的直流电输出；当所述驱动电路导通时,所述可控硅内具有所述辅助供电电路提供的直流电输入,本发明目的在于提供一种反激电源中利用可控硅隔离控制大功率负载的电路,在电路中增加以辅助供电电路,可直接为可控硅导通提供触发电流,减小可控硅导通时的瞬时电流或瞬时电压,利于EMC测试的通过。(The invention discloses a circuit and an electric appliance for isolating and controlling a high-power load by using a silicon controlled rectifier in a flyback power supply, wherein the circuit and the electric appliance comprise a high-frequency transformer, an absorption circuit, a secondary output circuit, an auxiliary power supply circuit, a driving circuit and the silicon controlled rectifier; the auxiliary power supply circuit is connected with the high-frequency transformer, and two ends of the auxiliary power supply circuit are connected with an alternating-current phase line input and a simulation ground; the output end of the driving circuit is connected with the G pole of the controllable silicon and used for controlling the conduction of the controllable silicon, and when the flyback power supply is started, the auxiliary power supply circuit has continuous direct current output; when the driving circuit is conducted, the silicon controlled rectifier is internally provided with direct current input provided by the auxiliary power supply circuit, the invention aims to provide a circuit for controlling a high-power load in a flyback power supply by utilizing silicon controlled rectifier isolation, and the auxiliary power supply circuit is additionally arranged in the circuit, so that trigger current can be directly provided for the conduction of the silicon controlled rectifier, the instantaneous current or instantaneous voltage when the silicon controlled rectifier is conducted is reduced, and the passing of an EMC test is facilitated.)

1. A circuit for isolating and controlling a high-power load by using a silicon controlled rectifier in a flyback power supply comprises a high-frequency transformer, an absorption circuit and a secondary output circuit, wherein the absorption circuit and the secondary output circuit are connected with the high-frequency transformer through pins; the auxiliary power supply circuit is connected to a pin of the high-frequency transformer, and two ends of the auxiliary power supply circuit are connected to an alternating-current phase line input and a simulation ground; the output end of the driving circuit is connected with the G pole of the controlled silicon and used for controlling the conduction of the controlled silicon, the T1 pole of the controlled silicon is connected to the input of the alternating current phase line, and the T2 pole of the controlled silicon is used as the output end of the controlled silicon;

when the flyback power supply is started, the auxiliary power supply circuit has continuous direct current output; when the driving circuit is conducted, the silicon controlled rectifier is internally provided with direct current input provided by the auxiliary power supply circuit.

2. The circuit of claim 1, wherein the driving circuit comprises a first resistor, a second resistor, a main control chip, an optocoupler and a triode, wherein a control A pole of the optocoupler is connected to a direct current low voltage power supply, a control K pole of the optocoupler is connected to an I/O port of the main control chip, a first output end of the optocoupler is connected in series with the first resistor and the second resistor and is connected to a G pole of the thyristor, a second output end of the optocoupler is connected to a base of the triode, an emitter of the triode is connected to the analog ground, a collector of the triode is connected to a first output end of the optocoupler, and a pull-down resistor is connected between the second output end of the optocoupler and the analog ground.

3. The circuit according to claim 1, wherein the auxiliary power supply circuit comprises a first snubber circuit, a first energy storage capacitor and a first dummy load resistor, the first snubber circuit, the first energy storage capacitor and the first dummy load resistor are formed by a first diode, a first current limiting resistor and a first filter capacitor, the first snubber circuit, the first energy storage capacitor and the first dummy load resistor are connected in parallel, and two ends of the first current limiting resistor are respectively connected with the input of the alternating current phase line and the analog ground.

4. The circuit of claim 1, wherein the secondary output circuit comprises a second buffer circuit, a second energy storage capacitor and a second current limiting resistor, the second buffer circuit, the second energy storage capacitor and a second dummy load resistor are formed by a second diode, a second current limiting resistor and a second filter capacitor, the second buffer circuit, the second energy storage capacitor and the second dummy load resistor are connected in parallel, and two ends of the second dummy load resistor are used as load output ends of the secondary output circuit.

5. The circuit according to claim 1, wherein the absorption circuit comprises a first rectifying diode, a first filter capacitor and a first discharge resistor, the first rectifying diode, the first filter capacitor and the first discharge resistor form a closed loop, the closed loop is connected in parallel with a first current limiting resistor, and two ends of the first current limiting resistor are respectively connected with the high-voltage direct current input and the power chip output.

6. The circuit according to claim 1, further comprising a Y capacitor, wherein the Y capacitor comprises a first capacitor, a second capacitor and a third capacitor connected in a star shape, and the other ends of the first capacitor, the second capacitor and the third capacitor are respectively and correspondingly connected to the absorption circuit, the auxiliary power supply circuit and the secondary output circuit.

7. A water purifier comprising a circuit for isolating and controlling a high-power load using a thyristor according to any one of claims 1 to 6.

8. An electrical appliance comprising a circuit for isolated control of a high power load using thyristors according to any one of claims 1 to 6.

Technical Field

The invention relates to the technical field of flyback power supplies and thyristor drive application, in particular to a circuit and an electric appliance for isolating and controlling a high-power load by utilizing a thyristor in a flyback power supply.

Background

With the development of science and technology and the development of society, people have more and more requirements on high-power products, and the quality certification of the products is more and more strict, especially in the aspect of EMC testing. At present, most products which have isolation requirements and need to control the high-power load switch frequently generally adopt the following technologies:

generally, a switching power supply with a flyback topology structure is used as a power supply, and a silicon controlled rectifier and a bidirectional optocoupler are used as control devices. The thyristor isolation control circuit is characterized in that a T2 pole, a G pole, a current-limiting resistor and an output end of a bidirectional optocoupler of a thyristor are connected in series, a direct current low-voltage electrode, the current-limiting resistor, an input end of the bidirectional optocoupler and a control pin of a main control chip are connected in series, the conduction and the cut-off of the output end of the bidirectional optocoupler are controlled through a high level and a low level which are controlled by the main control chip, alternating current commercial power is supplied, and then the conduction and the cut-off of the thyristor are controlled, so that the thyristor works in a first quadrant and.

However, due to the existence of the trigger current of the bidirectional thyristor, the conduction voltage of the current-limiting resistor and the bidirectional optocoupler and other reasons, larger instantaneous voltage and instantaneous current, namely dv/dt and di/dt, exist at the moment of each conduction of the bidirectional thyristor, and particularly the bidirectional thyristor controls a high-power device; and alternating current commercial power input is after zero at every turn, all need wait that triac T2 utmost point reaches certain degree with the voltage in G utmost point both ends and can have sufficient trigger current to make triac switch on for the product is difficult to pass through in EMC test.

In view of the above problems, there is a need for an improved circuit design for isolating and controlling a high-power load with a thyristor.

Disclosure of Invention

The invention aims to provide a circuit for controlling a high-power load by utilizing silicon controlled rectifier isolation, wherein an auxiliary power supply circuit is added in the circuit, so that trigger current can be directly provided for the conduction of the silicon controlled rectifier, the instantaneous current or the instantaneous voltage when the silicon controlled rectifier is conducted is reduced, and the passing of an EMC test is facilitated.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a circuit for controlling a high-power load by silicon controlled rectifier isolation comprises a high-frequency transformer, an absorption circuit and a secondary output circuit, wherein the absorption circuit and the secondary output circuit are connected with the high-frequency transformer through pins; the power supply circuit also comprises an auxiliary power supply circuit, a driving circuit and a controlled silicon; the auxiliary power supply circuit is connected to a pin of the high-frequency transformer, and two ends of the auxiliary power supply circuit are connected to an alternating-current phase line input and a simulation ground; the output end of the driving circuit is connected with a control electrode of the controlled silicon and used for controlling the conduction of the controlled silicon, a T1 electrode of the controlled silicon is connected to the input of the alternating-current phase line, and a T2 electrode of the controlled silicon is used as the output end of the controlled silicon;

when the flyback power supply is started, the auxiliary power supply circuit has continuous direct current output; when the driving circuit is conducted, the silicon controlled rectifier is internally provided with direct current input provided by the auxiliary power supply circuit.

The invention relates to a circuit for isolating and controlling a high-power load by utilizing a silicon controlled rectifier in a flyback power supply, which comprises a high-frequency transformer, an absorption circuit and a secondary output circuit, wherein the absorption circuit and the secondary output circuit are connected with the high-frequency transformer through pins; the output end of the driving circuit is connected with a control electrode of the controlled silicon and used for controlling the conduction of the controlled silicon, a T1 electrode of the controlled silicon is connected to the input of the alternating-current phase line, and a T2 electrode of the controlled silicon is used as the output end of the controlled silicon; when the flyback power supply is started, the auxiliary power supply circuit has continuous direct current output; when the drive circuit is conducted, the direct current input provided by the auxiliary power supply circuit is arranged in the silicon controlled rectifier, and the silicon controlled rectifier conduction condition is that the T2 pole and the G pole can have enough trigger current to conduct the silicon controlled rectifier to a certain degree.

Further, drive circuit includes first resistance, second resistance, main control chip, opto-coupler and triode, the control A utmost point of opto-coupler inserts direct current low voltage power, the control K utmost point of opto-coupler connects the IO mouth of main control chip, the first output series connection first resistance and the second resistance of opto-coupler, and connect the G utmost point of silicon controlled rectifier, the second output termination of opto-coupler the base of triode, the projecting pole of triode connects the simulation ground, the collecting electrode of triode connects the first output of opto-coupler, it has pull-down resistance to connect between the second output of opto-coupler and the simulation ground.

Furthermore, the auxiliary power supply circuit comprises a first buffer circuit, a first energy storage capacitor and a first dummy load resistor, wherein the first buffer circuit, the first energy storage capacitor and the first dummy load resistor are formed by a first diode, a first current limiting resistor and a first filter capacitor, the first buffer circuit, the first energy storage capacitor and the first dummy load resistor are connected in parallel, and two ends of the first current limiting resistor are respectively connected with the input of the alternating current phase line and the analog ground.

Furthermore, the secondary output circuit comprises a second buffer circuit, a second energy storage capacitor and a second current limiting resistor, wherein the second buffer circuit, the second energy storage capacitor and the second dummy load resistor are formed by a second diode, a second current limiting resistor and a second filter capacitor, the second buffer circuit, the second energy storage capacitor and the second dummy load resistor are connected in parallel, and two ends of the second dummy load resistor are used as load output ends of the secondary output circuit.

Furthermore, the absorption circuit comprises a first rectifier diode, a first filter capacitor and a first discharge resistor, the first rectifier diode, the first filter capacitor and the first discharge resistor form a closed loop, the closed loop is connected with a first current limiting resistor in parallel, and two ends of the first current limiting resistor are respectively connected with the high-voltage direct current input and the power chip output.

And the other ends of the first capacitor, the second capacitor and the third capacitor are respectively and correspondingly connected to the absorption circuit, the auxiliary power supply circuit and the secondary output circuit.

Another aspect of the present invention also provides a water purifier, which includes a circuit for isolating and controlling a high-power load by using a thyristor in the flyback power supply.

Another aspect of the present invention also provides an electrical appliance, which includes a circuit for controlling a high-power load by using thyristor isolation in the flyback power supply.

Drawings

Fig. 1 is a schematic circuit diagram of a circuit for controlling a high-power load by using thyristor isolation in a flyback power supply.

Detailed Description

The circuit for controlling the high-power load by utilizing the silicon controlled rectifier isolation in the flyback power supply is described by combining the attached drawings.

As can be seen from the schematic diagram shown in fig. 1, as a preferred embodiment of the present invention:

a circuit for isolating and controlling a high-power load by using a silicon controlled rectifier in a flyback power supply comprises a high-frequency transformer TIA, an absorption circuit 1 and a secondary output circuit 2, wherein the absorption circuit 1 is connected with the high-frequency transformer TIA through pins and is provided with a high-voltage power supply input; the power supply circuit also comprises an auxiliary power supply circuit 3, a drive circuit 5 and a silicon controlled rectifier SCR 1; the auxiliary power supply circuit 3 is connected to a pin of the high-frequency transformer TIA, and two ends of the auxiliary power supply circuit 3 are connected to an AC live wire input ACL and a simulation ground GNDA; the output end of the driving circuit 5 is connected with the control electrode of a silicon controlled rectifier SCR1 and is used for controlling the conduction of a silicon controlled rectifier SCR1, the T1 electrode of the silicon controlled rectifier SCR1 is connected to the AC live wire input ACL, and the T2 electrode of the silicon controlled rectifier SCR1 is used as the output end of the silicon controlled rectifier SCR 1;

when the flyback power supply is started, the auxiliary power supply circuit 3 has continuous direct current output; when the driving circuit 5 is turned on, the silicon controlled SCR1 has a dc input provided by the auxiliary power supply circuit 3.

The invention relates to a circuit for isolating and controlling a high-power load by using a silicon controlled rectifier in a flyback power supply, which comprises a high-frequency transformer TIA, an absorption circuit 1 and a secondary output circuit 2, wherein the absorption circuit 1 and the high-frequency transformer TIA are connected through pins, the absorption circuit 1 is provided with a high-voltage power supply input, a basic constitution form of the high-power load circuit is provided, the basic circuit also comprises an auxiliary power supply circuit 3, a driving circuit 5 and a silicon controlled rectifier SCR1, the auxiliary power supply circuit 3 is connected on the pins of the high-frequency transformer TIA, and two ends of the auxiliary power supply circuit 3 are connected with an AC live wire input ACL and a simulation ground GN; the output end of the driving circuit 5 is connected with the control electrode of a silicon controlled rectifier SCR1 and is used for controlling the conduction of a silicon controlled rectifier SCR1, the T1 electrode of the silicon controlled rectifier SCR1 is connected to the AC live wire input ACL, and the T2 electrode of the silicon controlled rectifier SCR1 is used as the output end of the silicon controlled rectifier SCR 1; when the flyback power supply is started, the auxiliary power supply circuit 3 has continuous direct current output; when the driving circuit 5 is conducted, the silicon controlled rectifier SCR1 is internally provided with a direct current input provided by the auxiliary power supply circuit 3, and the conduction condition of the silicon controlled rectifier SCR1 is that the T2 pole and the G pole reach a certain degree to have enough trigger current to conduct the silicon controlled rectifier SCR1, but in the invention, the auxiliary power supply current is used for providing a direct current input which is used as a reference value, so that the change of the conduction condition of the silicon controlled rectifier SCR1 from 0 to conduction is converted from the reference value to conduction, thereby effectively reducing the instantaneous current and the instantaneous voltage when the bidirectional silicon controlled rectifier SCR1 is conducted, on the other hand, when the bidirectional silicon controlled rectifier SCR1 switch is switched, the radiation on side bands caused by switching transients and discrete frequencies except adjacent channels is reduced, and the passing of an EMC test is facilitated.

In addition, in the embodiment of the invention, the alternating current commercial power is 380V input.

The following describes the various components of the circuit according to a schematic diagram of the circuit:

in this embodiment, the high-frequency transformer TIA is applied to a switching power supply of a flyback topology, and is used in cooperation with the absorption circuit 1.

The drive circuit 5: drive circuit 5 includes first resistance R10, second resistance R9, main control chip, opto-coupler U1 and triode Q1, the control A utmost point of opto-coupler U1 inserts direct current low voltage power, the control K of opto-coupler U1 connects the IO mouth of main control chip, the first output series connection first resistance R10 and second resistance R9 of opto-coupler U1, and the G utmost point of silicon controlled rectifier SCR1, the second output termination of opto-coupler U1 triode Q1's base, triode Q1's projecting pole connects analog ground GNDA, triode Q1's collecting electrode connects the first output of opto-coupler U1, it has pull-down resistance R11 to connect between opto-coupler U1's second output and the analog ground GNDA.

The pull-down resistor R11 is clamped at a high level by one end of the output when the optocoupler U1 is switched on, the pull-down resistor R11 plays a role in current limiting, when one end of the optocoupler U1 is at a high level, the other end opposite to the high level is at a low level, and the G of the SCR1 is at a negative voltage.

In this embodiment, the driving circuit 5 is composed of a triode Q1, resistors (R8, R9, R10, R12), a discharge resistor R7, a pull-down resistor R11, a third filter capacitor (C5, C6) and an optocoupler U1, and the driving circuit 5 and a thyristor SCR1 together form a thyristor driving circuit; the T1 pole of the SCR1 is connected with an AC live wire input ACL and one end of a resistor R6 of the auxiliary power supply circuit 3, the T2 pole is the output end of the SCR1, and the G pole is connected with a collector of a triode Q1 and a pin 4 of an optocoupler U1 after being connected with a first resistor R10 and a second resistor R9 in series; the base electrode of the triode Q1 is connected with a pin 3 of the optocoupler U1 and one end of the pull-down resistor R11, and the emitter e of the triode Q1 is connected with the other end of the first current-limiting resistor R6 and the other end of the pull-down resistor R11 of the auxiliary power supply circuit 3; the low-voltage direct current, the resistor R12 and the pin 1 of the optocoupler U1 are sequentially connected in series, and the pin 2 of the optocoupler U1 is connected with an I/O port of the main control chip.

Auxiliary power supply circuit 3: the auxiliary power supply circuit 3 comprises a first buffer circuit, a first energy storage capacitor EC2 and a first dummy load resistor R5, wherein the first buffer circuit is composed of a first diode D3, a first current limiting resistor R6 and a first filter capacitor C3, the first buffer circuit, the first energy storage capacitor EC2 and the first dummy load resistor R5 are connected in parallel, and two ends of the first current limiting resistor R6 are respectively connected with the AC live wire input ACL and the analog ground GNDA.

According to the connection relationship of the auxiliary power supply circuit 3, the two ends of the first current limiting resistor R6 are respectively connected with the ac live wire input ACL and the analog ground GNDA, and according to the known connection relationship, the power supply voltage of the auxiliary power supply circuit 3 is obtained through the high-voltage dc input of the absorption circuit 1 according to the turn ratio between the auxiliary power supply circuit 3 and the absorption circuit 1.

In this embodiment, when the flyback power supply is started, the auxiliary power supply circuit 3 always provides a direct current output of about 17V, in order to keep the circuit stable, the first energy storage capacitor EC2 is used for storing the electric energy provided by the auxiliary power supply circuit 3, and the first dummy load resistor R5 is used for consuming the electric energy, so as to ensure that the auxiliary power supply circuit 3 is stable.

Secondary output circuit 2: the secondary output circuit 2 comprises a second buffer circuit, a second energy storage capacitor EC1 and a second dummy load resistor R4, wherein the second buffer circuit is composed of a second diode D2, a second current limiting resistor R3 and a second filter capacitor C2, the second buffer circuit, the second energy storage capacitor EC1 and the second dummy load resistor R4 are connected in parallel, and two ends of the second dummy load resistor R4 are used as load output ends of the secondary output circuit 2.

The secondary output circuit 2 is used for providing output for a load, and comprises a second buffer circuit which is composed of a second diode D2, a second current limiting resistor R3 and a second filter capacitor C2 and is used for switching loss of the load, inhibiting the rising rate of current passing through the load and protecting the load from normal operation, and a second energy storage capacitor EC1 is arranged for further preventing the load current from suddenly changing, and the second dummy load resistor is convenient for fault detection of the load.

The absorption circuit 1: the absorption circuit 1 comprises a third rectifier diode D1, a third filter capacitor C1 and a third discharge resistor R2, the third rectifier diode D1, the third filter capacitor C1 and the third discharge resistor R2 form a closed loop, the closed loop is connected with a first current-limiting resistor R1 in parallel, and two ends of the third current-limiting resistor R1 are respectively connected with a high-voltage direct current input and a power chip output.

The third rectifier diode D1, the third filter capacitor C1 and the third discharge resistor R1 form a closed loop to form the spike absorption circuit 1, the third filter capacitor C1 and the third discharge resistor R1 are used to suppress surge voltage occurring in the absorption circuit 1, meanwhile, the third rectifier diode D1 is used, the third rectifier diode D1 is a fast recovery diode, meanwhile, the absorption circuit 1 has a buffering function, the third rectifier diode D1, the third filter capacitor C1 and the third discharge resistor R1 are used to suppress the voltage rise rate in the absorption circuit 1, and the third discharge resistor R1 provides a discharge path for the third filter capacitor C1.

Y capacitance: the Y capacitor comprises a first capacitor CY1, a second capacitor CY2 and a third capacitor CY3 which are connected in a star shape, and the other ends of the first capacitor CY1, the second capacitor CY2 and the third capacitor CY3 are respectively and correspondingly connected to the absorption circuit 1, the auxiliary power supply circuit 3 and the secondary output circuit 2.

The Y capacitor is used for suppressing common-mode interference signals.

In addition, in the Y capacitor, when one capacitor in the capacitor bank is in short circuit due to breakdown of faults, the fault current is reduced to a certain range due to the impedance limitation of the other two healthy phases, the fault influence is reduced, and the star connection has the greatest advantage that various protection modes can be selected.

Analyzing the working principle of the circuit: the flyback power supply is normally started, high-voltage direct current input is subjected to spike elimination through the absorption circuit 1 and is converted through the high-frequency transformer TIA, a certain turn ratio exists between the absorption circuit 1 and the auxiliary power supply circuit 3, the auxiliary power supply circuit 3 always outputs direct current of about 17V through adjustment of the turn ratio, and the magnitude of the direct current output by the auxiliary power supply circuit 3 is determined by the magnitude of conduction current of the silicon controlled rectifier SCR 1;

when the I/O port of the main control chip outputs low level, the optocoupler U1 is conducted, the optocoupler U1 is connected with the triode Q1 in a manner similar to a Darlington tube, so that the triode Q1 is conducted, and as the pull-down resistor R11 limits the pin 3 of the optocoupler U1 to be high level, the pin 4 of the optocoupler U1 to be low level, namely the G electrode of the SCR1 is input with negative voltage; because the T1 pole of the bidirectional thyristor SCR1 is connected to the AC live wire input ACL and is also connected to the anode output by the auxiliary power supply circuit 3, a potential difference is formed, trigger current is generated, the current direction flows in from the T1 pole of the thyristor SCR1 and flows out from the G pole, and the voltage of the AC live wire input ACL is output by the SCR1T2 pole, when the optocoupler U1 and the thyristor SCR1 are simultaneously conducted, the thyristor SCR1 can directly obtain the trigger current from the auxiliary power supply circuit 3, enough trigger current can be obtained to conduct the thyristor SCR1 without waiting for the T2 pole and the G pole of the thyristor SCR1 to reach a certain degree, dv/dt and di/dt when the bidirectional thyristor SCR1 is conducted can be effectively reduced, and the passing of an EMC test is facilitated.

When the optocoupler U1 is turned on and the thyristor SCR1 is turned on, the thyristor SCR1 works in the second quadrant and the third quadrant, in this embodiment, the thyristor SCR1 is a bidirectional thyristor SCR1, and belongs to a NPNPN five-layer device, in this embodiment, the negative T1 pole of the trigger voltage G of the thyristor SCR1 is positive, when an ac live wire is input to an ACL, because there is a phase transition between the ac live wire and an ac zero line input, there is a sudden-small alternating transition between the T1 pole and the T2 pole of the working voltage of the thyristor SCR1, and the direction of the conduction current of the thyristor SCR1 causes the T2 pole to flow to the T1 pole or the T1 pole to flow to the T2 pole, in sum, in this embodiment, the thyristor SCR1 works in the second quadrant and the third quadrant.

In addition, the opto-coupler U1 provides the characteristic of electrical isolation, and as is known, opto-coupler U1 plays the isolation effect of signal, because opto-coupler U1 is unidirectional transmission, so can realize the unidirectional transmission of signal, make input and output realize electrical isolation completely, output signal does not have the influence to the input, and the interference killing feature is strong, job stabilization.