CN109713919A - A kind of double winding secondary side feedback Switching Power Supply - Google Patents

Abstract

The disclosure discloses a kind of double winding secondary side feedback Switching Power Supply, comprising: primary side rectification filtering unit, control unit, confession electric unit, secondary side feedback unit, OVP unit, two-winding transformer and voltage signal acquisition unit.On the one hand the disclosure obtains pressure stabilizing output by secondary side feedback, be monitored using overvoltage protection to output voltage, in safe range by output voltage control；On the other hand stand-by power consumption is effectively reduced for electric energy by booting.

Description

A dual-winding secondary feedback switching power supply

technical field

The present disclosure belongs to the technical field of electronic circuits, and in particular relates to a dual-winding secondary feedback switching power supply.

Background technique

Switching power supply is a power supply conversion device for electronic equipment and electronic appliances. With the increasing attention to the safety of switching power supply, the application of isolated switching power supply is becoming more and more extensive.

In traditional isolated switching power supplies, optocoupler isolation feedback is often used to obtain stable voltage output, as shown in Figure 1. The system feeds back the output voltage V _out signal to the PWM module in the switching power supply control chip through the optocoupler set in the feedback loop, and then the PWM module adjusts the energy transferred from the transformer to the secondary side by controlling the duty cycle, so as to realize the secondary side's power supply. Constant voltage output. The power required by the switching power supply control chip to perform the control process is provided by a self-power supply circuit, which consists of a starting resistor R ₁ , a power tube Q ₁ , a diode D ₂ and an external charging capacitor C ₂ . However, this technology has the following problems in practical applications: 1. When the feedback loop is disconnected, such as when the light-emitting diode in the optocoupler is broken down and short-circuited, the switching power supply control chip on the primary side cannot monitor and control the output voltage V _out , when the output voltage is too high, the load will be burned, and even more serious safety accidents will occur. 2. Considering the problem of loss on R ₁ , R ₁ usually selects a MΩ-level resistor. When Q ₁ supplies power to C ₂ , it is in the amplifying area, and there is no saturation conduction, so the voltage drop generated is very high, even as high as above Hundred volts, resulting in a large loss of power supply, it is difficult to achieve the six-level energy efficiency standards.

In conclusion, there is an urgent need to design a switching power supply system to improve system security and reduce standby power consumption.

SUMMARY OF THE INVENTION

In view of the problems existing in the prior art, the purpose of the present disclosure is to provide a dual-winding secondary-side feedback switching power supply, which obtains a regulated output through secondary-side feedback, and uses overvoltage protection to monitor the output voltage to prevent the output voltage from running out of control and causing safety Accident happens.

To achieve the above objects, the present disclosure describes the following technical solutions in detail:

A dual-winding secondary-side feedback switching power supply, comprising: a primary-side rectification and filtering unit, a control unit, a self-power supply unit, an overvoltage protection unit, a secondary-side feedback unit, a dual-winding transformer and a voltage signal acquisition unit; wherein,

The primary-side rectifier filter unit includes a rectifier bridge and a C1 capacitor, which is used to convert alternating current into direct current and then input it;

The control unit includes a PWM module and a drive module, which are used to control the charging and discharging process of the self-powered unit, and perform corresponding adjustment of the circuit based on the received feedback information;

The self-power supply unit is respectively connected with the power supply Vin and the control unit, and is used for storing energy and supplying power to the control unit;

The secondary side feedback unit is provided with a feedback output terminal, one end is connected to the positive plate or negative plate of the energy storage capacitor of the self-power supply unit, and the other end is connected to the PWM module for detecting the change of the secondary side output signal and feeding it back to the control unit;

One end of the OVP unit is connected to the voltage signal acquisition unit, and the other end is connected to the PWM module, for detecting that the output voltage V _out exceeds the preset threshold, generating an OVP signal and outputting it to the PWM module to make the power supply enter the overvoltage protection state ;

The double-winding transformer includes a primary side inductance Lp and a secondary side inductance Ls, the positive pole of the Lp is connected to the switch tube of the self-power supply unit, and the negative pole is grounded;

One end of the voltage signal acquisition unit is grounded, and the other end is connected to the positive pole of the primary inductor Lp.

Preferably, the voltage signal acquisition unit includes resistors R ₈ and R ₉ , and the common terminals of the resistors R ₈ and R ₉ are connected to the overvoltage protection unit.

Preferably, the secondary side feedback unit includes a voltage regulator device, an optocoupler and a feedback auxiliary device; the optocoupler includes a light emitting diode and a phototransistor, and the collector and emitter of the phototransistor are feedback output terminals; wherein, the phototransistor The collector of the triode is connected to the chip gnd, and the emitter is connected to the PWM module through the chip FB pin; the feedback auxiliary device includes a voltage divider resistor.

Preferably, the self-powered unit includes a start-up resistor, a first switch tube, a second switch tube, a Vcc charging capacitor management module and a Vcc charging capacitor; wherein,

The Vcc charging capacitor is the energy storage capacitor of the self-powered unit;

The drain of the first switch is connected to the power supply V _in , and the source is connected to the drain of the second switch;

and,

The common terminal of the first switch tube and the second switch tube is connected to the _Vcc charging capacitor through the _Vcc charging management unit;

The grids of the first switch tube and the second switch tube are connected to the driving module of the control unit;

When the circuit works normally, the first switch tube is turned on, and the second switch tube is turned off, forming a charging path from the power supply V _in , the first switch tube to the Vcc charging capacitor, and realizing the bootstrap power supply;

When the first and second switch tubes are turned off at the same time, resulting in insufficient power supply to the circuit, the first switch tube is turned on to achieve high-voltage power supply.

Preferably, the bootstrap power supply is applicable to any one of the following load circuits: no-load, light-load and heavy-load.

Preferably, the first switch tube and the second switch tube are of voltage-driven type.

Preferably, the source of the second switch tube is connected with a sampling resistor, and the input end of the sampling resistor is connected to the control unit for monitoring the ILp current when the primary side is turned on. The control unit obtains and controls the primary side circuit by obtaining and controlling the The current peak value of ILp in ILp realizes cycle-by-cycle overcurrent protection.

Preferably, the switching power supply further includes an undervoltage protection unit, the input end of the undervoltage protection unit is connected to the common end of the resistors R8 and R9, and the output end is connected to the PWM module, which is used for detecting that the power supply Vin is lower than the preset value. When the threshold is set, an undervoltage signal is generated and output to the PWM module to make the power supply enter the undervoltage protection state.

Preferably, the switching power supply further includes an absorption unit, which includes a resistor R1, a capacitor C4 and a diode D1; wherein, after the resistor R1 and the capacitor C4 are connected in parallel, one end is connected to the positive electrode of the primary inductor Lp through the diode D1, and the other One end is connected to the negative pole of the primary inductor Lp.

Preferably, the switching power supply further includes an output rectifying and filtering unit, which is used for converting the alternating current into half-wave direct current and further filtering out the alternating current component to reduce the ripple before outputting.

Preferably, the rectifying and filtering unit includes a diode and a capacitor.

Compared with the prior art, the beneficial effects brought by the present disclosure are:

1. The present disclosure designs a switching power supply circuit in which the secondary side feedback and overvoltage protection jointly control the output voltage. On the one hand, the secondary side feedback is used to quickly respond and adjust the output voltage to obtain a regulated output; on the other hand, the overvoltage protection is used. The output voltage is monitored, and when the output voltage exceeds the preset threshold, the overvoltage protection is activated to avoid the loss of control of the output voltage when the optocoupler feedback loop fails, resulting in the occurrence of safety accidents;

2. The present disclosure designs a floating structure, which facilitates accurate and convenient collection of voltage data, helps to achieve accurate overvoltage protection and control, and the voltage sampling circuit is simple, which simplifies the production process and reduces the cost;

3. The present disclosure also designs a self-power supply circuit implemented by the switching power supply by means of bootstrapping. During the bootstrapping power supply process, since the switching tube is in a saturated conduction state, the power dissipated is extremely small, and the standby power consumption is reduced.

Description of drawings

1 is a schematic structural diagram of a conventional switching power supply circuit;

2 is a schematic structural diagram of a switching power supply circuit provided by the present disclosure;

3 is a schematic structural diagram of another switching power supply circuit provided by the present disclosure;

Figure 4 is a schematic diagram of the bootstrap power supply waveform when the circuit is overloaded;

Figure 5 is a schematic diagram of the bootstrap power supply waveform when the circuit is no-load or light-load.

The symbols in the figure are represented as:

1-primary side rectification filter unit; 2-control unit; 3-Brown out unit; 4-voltage signal acquisition unit; 5-secondary side feedback unit (51-optical coupler; 52-feedback auxiliary device); 6-absorption unit; 7-Output rectifier filter unit; 8-OVP unit.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to FIGS. 1 to 5 in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of them. example. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

The switch tubes involved in the technical solutions provided by the embodiments of the present invention may be transistors such as MOS, MESFET, JFET, etc., and may be enhancement mode or depletion mode. In the embodiments of the present invention, MOS tubes are used as examples for description; The connection can be a direct connection of components or an electrical connection.

Various embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. It should be noted that the display order of the embodiments of the present disclosure only represents the sequence of the embodiments, and does not represent the advantages and disadvantages of the technical solutions provided by the embodiments.

As shown in Figure 2, a dual-winding secondary-side feedback switching power supply circuit includes: a primary-side rectification and filtering unit 1, a control unit 2, a self-power supply unit, a secondary-side feedback unit 5, an OVP unit 8, a dual-winding transformer and a voltage signal Collection unit 4; wherein,

The primary-side rectifier filter unit includes a rectifier bridge and a C1 capacitor, which is used to convert the alternating current into the direct current Vin and input it;

The control unit includes a PWM module and a drive module, which are used to control the charging and discharging process of the self-powered unit, and perform corresponding adjustment of the circuit based on the received feedback information;

The self-power supply unit is respectively connected with the power supply Vin and the control unit, and is used for storing energy and supplying power to the control unit;

The secondary side feedback unit is provided with a feedback output terminal, one end is connected to the positive plate or negative plate of the energy storage capacitor of the self-power supply unit, and the other end is connected to the PWM module for detecting the change of the secondary side output signal and feeding it back to the control unit;

One end of the OVP unit is connected to the voltage signal acquisition unit, and the other end is connected to the PWM module for detecting that the output voltage V _out exceeds the preset threshold, generating an OVP signal and outputting it to the PWM module to make the power supply enter overvoltage protection. state;

The double-winding transformer includes a primary side inductance Lp and a secondary side inductance Ls, the positive pole of the Lp is connected to the switch tube of the self-power supply unit, and the negative pole is grounded;

One end of the voltage signal acquisition unit is grounded, and the other end is connected to the positive pole of the primary inductor Lp.

The above embodiment completely discloses the technical solution of the present invention. Compared with the problem in the prior art that the output voltage cannot be detected and controlled, the output voltage is too high and the load is burned out. The output voltage responds and adjusts to obtain a regulated output; on the other hand, the overvoltage protection is used to detect the output voltage and carry out overvoltage protection to avoid the occurrence of safety accidents caused by excessive output voltage.

Further, the present disclosure realizes self-power supply by means of bootstrapping. During the power supply process, the switch tube is in a saturated conduction state, which overcomes the problem of large power loss in the prior art.

In another embodiment, the voltage signal acquisition unit includes resistors R ₈ and R ₉ , and the common terminals of the resistors R ₈ and R ₉ are connected to the overvoltage protection unit.

In another embodiment, the secondary side feedback unit 5 includes a voltage regulator device, an optocoupler 51 and a feedback auxiliary device 52;

The optocoupler 51 includes a light-emitting diode D3 and a phototransistor Q1, and the collector and the emitter of the phototransistor Q1 are feedback output terminals; wherein, the collector of the phototransistor Q1 is connected to the chip ground gnd, and the emitter is connected to the chip pin. FB is connected to the PWM module;

The feedback auxiliary device 52 includes voltage dividing resistors R3-R7.

In this embodiment, the output voltage Vout is divided by a voltage dividing resistor and then input to the voltage regulator device for comparison with the reference voltage. The error voltage signal output by the operational amplifier controls the current flowing through the optocoupler 51. When the output voltage Vout is high, the current The current passing through the optocoupler 51 becomes larger, the voltage at the FB port of the chip becomes smaller, and the PWM module controls the output duty cycle to become smaller to reduce the energy transferred from the transformer to the secondary side, and the output voltage Vout begins to decrease; on the contrary, if the output voltage is biased to a lower Vout , according to the feedback of the current of the optocoupler 51, the PWM module controls the increase of the duty cycle to increase the energy transferred from the transformer to the secondary side, thereby increasing the output voltage Vout. In this way, the control is continuously adjusted to stabilize the output voltage at the set value.

In another embodiment, the self-power supply unit includes a start-up resistor, a first switch tube M1, a second switch tube M2, a Vcc charging capacitor management module, and a Vcc charging capacitor; wherein,

The Vcc charging capacitor is the energy storage capacitor of the self-powered unit;

The drain of the first switch M1 is connected to the power supply V _in , and the source is connected to the drain of the second switch M2;

and,

The common terminals of the first switch tube M1 and the second switch tube M2 are connected to the _Vcc charging capacitor through the _Vcc charging capacitor management module;

The gates of the first switch tube M1 and the second switch tube M2 are connected to the driving module of the control unit;

When the circuit works normally, the first switch tube is turned on, and the second switch tube is turned off, forming a charging path from the power supply V _in , the first switch tube to the Vcc charging capacitor, and realizing the bootstrap power supply;

When the first and second switch tubes are turned off at the same time, resulting in insufficient power supply to the circuit, the first switch tube is turned on to achieve high-voltage power supply.

In this embodiment, when the switching power supply starts, the power supply charges the gate-source parasitic capacitance Cgs of M1 through the start-up resistor R1, and raises the gate-source voltage Vgs of M1 to its threshold voltage Vth to make M1 turn on, forming the power supply, M1 to Vcc charging The charging path of capacitor C2 charges Vcc to a preset value, and the control circuit starts. The Vcc charging capacitor management module is used to ensure the unidirectional conduction of the charging circuit, and protect the switch M1 by limiting the current of the charging circuit. The Vcc voltage is fed back to the control circuit.

Secondly, when the switching power supply control circuit works normally, the control circuit first drives M1 and M2 in the switching circuit to turn on at the same time, and turns off M2 after a delay. At this time, the gate-source parasitic capacitance Cgs of M1 is bootstrapped, and M1 remains on. state, form the charging path from the power supply, M1 to the charging capacitor C2, charge Vcc, and realize the bootstrap power supply; because M1 is in the bootstrap state at this time, the gate voltage is large, M1 is in a saturated conduction state, and the voltage drop is extremely small, The resulting power consumption is therefore extremely small.

After the Vcc charging is completed, M2 is turned on again under the action of the control circuit, and the current flows from the input power supply through M1, M2, and the primary inductance Lp of the transformer to the ground, that is, the primary side is in a conducting state, and the transformer stores energy during this process; After that, M1 and M2 are turned off, and the primary side is turned off. Since the magnetic flux cannot be abruptly changed, the secondary side of the transformer induces positive and negative voltages on the upper and lower sides, and the secondary side freewheels to release energy.

In addition, when M1 and M2 are in the off state for a long time and the Vcc power supply is insufficient, the control circuit raises the gate voltage of M1 to Vcc, and the power supply charges the gate of M1 through the start-up resistor R1, so that M1 is turned on for high-voltage power supply.

Regarding the bootstrap power supply of the circuit in the above embodiment, it should be emphasized here that, unlike the prior art, the above embodiment is applicable to circuits with different load generation capabilities, including no-load, light-load and heavy-load.

Exemplarily, when the circuit is heavily loaded (the load impedance is small and the load current is large), the waveform is as shown in FIG. 4 . At this time, the Vcc power supply adopts the bootstrap power supply mode. When the primary side is turned on, M1 and M2 are turned on at the same time, and then M2 is turned off after a delay. Turn on M2, and finally turn off M1 and M2 at the same time.

When the circuit has no load (the load is in an open state) or light load (the load rate is generally below 30%-50%), the waveform is shown in Figure 5. At this time, the circuit still uses the bootstrap power supply, but due to the low frequency, the power generated by a bootstrap power supply cannot maintain the power consumed by the chip during the entire working cycle. When the chip works for several cycles, the Vcc capacitor will continue to discharge to under-voltage protection. Therefore, in the no-load or light-load state of the circuit, the high-voltage power supply is turned on for a period of time after M1 and M2 are turned off to meet the power consumption requirements of the chip.

In another embodiment, the first switch M1 and the second switch M2 are voltage-driven.

In this embodiment, the first switch transistor M1 and the second switch transistor M2 can be selected from at least one of MOS, MESFET, JEFT and other transistors, preferably NMOS.

In another embodiment, a sampling resistor R2 is connected to the source of the second switch tube, and the input end of the sampling resistor R2 is connected to the control unit for monitoring the ILp current when the primary side is turned on. The control unit obtains And control the current peak value of ILp in the primary circuit to realize cycle-by-cycle overcurrent protection.

In another embodiment, the switching power supply circuit further includes a Brown out unit, the input end of the Brown out unit is connected to the common end of the resistors R8 and R9, and the output end is connected to the PWM module for detecting that the power Vin is low. At the preset threshold, an undervoltage signal is generated and output to the PWM module to make the power supply enter the undervoltage protection state.

In this embodiment, when the primary side is turned on, the Brown out unit 3 generates a current so that the voltage of the common terminals of R8 and R9 is equal to the voltage of the input terminal of the primary side inductor Lp. Vin is approximately equal to the input terminal voltage of the primary inductor Lp, and the voltage applied across R8 is approximately equal to the power supply Vin, then the chip's output current I _prt =Vin/R8, by comparing I _prt with the reference current I _bias , when I _prt < After the I _bias is maintained for a period of time, the Brown out protection is triggered, and the Brown out signal is generated, that is, the input undervoltage protection.

In another embodiment, the switching power supply circuit further includes an absorption unit 6, which is used to prevent the switching tube from being damaged by the occurrence of excessively high spikes when the switching tube is turned off. The absorption unit includes a resistor R1, a capacitor C4 and a diode D1; wherein the resistor R1 and the capacitor C4 are connected in parallel and one end is connected to the positive electrode of the primary inductor Lp through the diode D1, and the other end is connected to the negative electrode of the primary inductor Lp.

In another embodiment, the switching power supply circuit further includes an output rectifying and filtering unit 7, which is used to convert the alternating current into half-wave direct current and further filter out the alternating current component to reduce the ripple before outputting; the rectifying and filtering unit 7 includes a diode D2 and a Capacitor C5.

In this embodiment, when the primary side of the transformer is turned off, the mutual inductance electromotive force of the secondary side makes the rectifier diode D2 conduct. On the one hand, the current flows into the load, and on the other hand, the capacitor C5 is charged and stored, so that the primary side can release energy to the load when it is turned on again. .

It should be noted that the present disclosure innovatively proposes a design concept of integrating the rest of the switching power supply circuit except the Vcc charging capacitor inside the chip. Among them, one end of the overvoltage protection unit (OVP) 8 and the undervoltage protection unit (Brownout) 3 is connected to the input end of the PWM module respectively, and the other end is connected to the voltage signal acquisition through the prt pin used for voltage signal acquisition in the control chip. The unit is connected, and the ground gnd pin of the control chip is connected with the input end of the primary side inductor Lp of the transformer to form a floating structure design. The PWM module receives the current value of the main circuit when the primary side is turned on through the cs pin used for current signal acquisition in the control chip, so as to start the overcurrent protection according to the monitoring result of the current peak value. The PWM module receives the feedback of the output voltage through the FB pin used for receiving the feedback information of the output voltage, so as to control the constant voltage output.

The above are only some embodiments of the present disclosure, and are not intended to limit the inventive concept of the present disclosure. Those skilled in the art can make certain replacements and modifications without departing from the inventive concept of the present disclosure, but they should all fall within the scope of the present disclosure. protected range.

Claims (10)

1. A dual winding secondary feedback switching power supply comprising: the device comprises a primary side rectifying and filtering unit, a control unit, a self-powered unit, a secondary side feedback unit, an OVP unit, a double-winding transformer and a voltage signal acquisition unit; wherein,

the primary side rectifying and filtering unit comprises a rectifying bridge and a C1 capacitor and is used for converting alternating current into direct current and inputting the direct current;

the control unit comprises a PWM module and a driving module and is used for controlling the charging and discharging process of the self-powered unit and correspondingly adjusting the circuit based on the received feedback information;

the self-powered unit is respectively connected with the power Vin and the control unit and is used for storing energy and supplying power to the control unit;

the secondary feedback unit is provided with a feedback output end, one end of the feedback output end is connected with the positive plate or the negative plate of the energy storage capacitor of the self-power supply unit, and the other end of the feedback output end is connected with the PWM module and used for detecting the change of a secondary output signal and feeding the change back to the control unit;

one end of the OVP unit is connected with the voltage signal acquisition unit, and the other end of the OVP unit is connected with the PWM module and used for detecting the output voltage V_outWhen the voltage exceeds a preset threshold value, generating an OVP signal and outputting the OVP signal to the PWM module to enable the power supply to enter an overvoltage protection state;

the double-winding transformer comprises a primary inductor Lp and a secondary inductor Ls, wherein the positive electrode of Lp is connected with a switching tube of the self-power supply unit, and the negative electrode of Lp is grounded;

one end of the voltage signal acquisition unit is grounded, and the other end of the voltage signal acquisition unit is connected with the anode of the primary side inductor Lp.

2. The switching power supply according to claim 1, wherein the voltage signal collecting unit preferably comprises a resistor R₈、R₉Said resistance R₈、R₉Is connected to the OVP unit.

3. The switching power supply according to claim 1, wherein the secondary feedback unit comprises a voltage regulator device, an optical coupler and a feedback auxiliary device;

the optocoupler comprises a light emitting diode and a phototriode, and a collector and an emitter of the phototriode are feedback output ends; wherein,

the collector and the emitter of the phototriode are feedback output ends;

the feedback auxiliary device comprises a divider resistor.

4. The switching power supply according to claim 1, wherein the self-powered unit comprises a starting resistor, a first switch tube, a second switch tube, a Vcc charging capacitor management module and a Vcc charging capacitor; wherein,

the Vcc charging capacitor is an energy storage capacitor of a self-powered unit;

the drain electrode of the first switch tube and a power supply V_inThe source electrode is connected with the drain electrode of the second switch tube;

and,

the common end of the first switch tube and the second switch tube passes through V_ccCharging capacitor management module and V_ccThe charging capacitors are connected;

the grid electrodes of the first switching tube and the second switching tube are connected with the driving module of the control unit;

when the circuit works normally, the first switch tube is switched on, the second switch tube is switched off to form a power supply V_inThe first switching tube is connected with a charging path of the Vcc charging capacitor to realize bootstrap power supply;

when the first switch tube and the second switch tube are turned off simultaneously to cause insufficient power supply of the circuit, the first switch tube is turned on to realize high-voltage power supply.

5. The switching power supply according to claim 4, wherein the bootstrap power supply is adapted to any one of the following load circuits: no-load, light load and heavy load.

6. The switching power supply according to claim 4, wherein the first switching tube and the second switching tube are of a voltage-driven type.

7. The switching power supply according to claim 4, wherein the source of the second switching tube is connected to a sampling resistor, an input terminal of the sampling resistor is connected to the control unit for monitoring ILp current when the primary side is turned on, and the control unit obtains and controls a peak value of ILp current in the primary side circuit.

8. The switching power supply according to any one of claims 1-7, further comprising an under-voltage protection unit, wherein an input terminal of the under-voltage protection unit is connected to a common terminal of the resistors R8, R9, and an output terminal of the under-voltage protection unit is connected to the PWM module, for generating an under-voltage signal and outputting the under-voltage signal to the PWM module to enable the power supply to enter an under-voltage protection state when detecting that the power Vin is lower than the preset threshold.

9. The switching power supply according to any one of claims 1-7, further comprising a sinking element, the sinking element comprising a resistor R1, a capacitor C4, and a diode D1; after the resistor R1 and the capacitor C4 are connected in parallel, one end of the resistor R1 is connected with the anode of the primary inductor Lp through the diode D1, and the other end of the resistor R1 is connected with the cathode of the primary inductor Lp.

10. The switching power supply according to any one of claims 1 to 7, further comprising an output rectifying and filtering unit for converting the alternating current into half-wave direct current and further filtering out alternating current components to reduce ripple and outputting the half-wave direct current; the rectifying and filtering unit comprises a diode and a capacitor.