CN218473035U - Flyback conversion circuit, converter, servo motor and driver of servo motor - Google Patents
Flyback conversion circuit, converter, servo motor and driver of servo motor Download PDFInfo
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- CN218473035U CN218473035U CN202221722047.5U CN202221722047U CN218473035U CN 218473035 U CN218473035 U CN 218473035U CN 202221722047 U CN202221722047 U CN 202221722047U CN 218473035 U CN218473035 U CN 218473035U
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Abstract
The utility model discloses a flyback conversion circuit, a converter, a servo motor and a driver thereof, wherein one end of a first switch is connected with a bus, and the other end is connected with a second end of a primary coil of a transformer; one end of the second switch is connected with the first end of the primary coil, and the other end of the second switch is grounded; the anode of the first diode is connected with the first end of the primary coil, and the cathode of the first diode is connected with the bus; the cathode of the second diode is connected with the second end of the primary coil, and the anode of the second diode is grounded through the third switch; the third switch is connected with the absorption circuit in parallel, and the absorption capacitor and the absorption resistor in the absorption circuit are connected in parallel; the first input end of the voltage comparison circuit is used for inputting bus sampling voltage, the second input end of the voltage comparison circuit is used for inputting threshold voltage, the output end of the voltage comparison circuit is connected with the input end of the driving circuit, and the output end of the driving circuit is connected with the control end of the third switch.
Description
Technical Field
The utility model relates to a DC-DC field especially relates to a flyback conversion circuit, converter, servo motor and driver thereof.
Background
The flyback converter topology structure has low cost, high reliability and excellent performance, and is widely applied to a low-power switching power supply below 200W and auxiliary power supplies of various electronic devices. The flyback converter can be divided into a single-tube flyback converter and a double-tube flyback converter due to different numbers of switches connected with the primary coil in series and different connection structures.
Because the switching tube that the primary winding connects in series need bear the busbar voltage, secondary winding passes through the superimposed voltage of transformer reflection primary winding voltage (reflection voltage promptly) and the peak voltage (the induced electromotive force that the primary winding leaks the inductance and produces) that the switching tube turn-off produced, under high input voltage's condition, the switching tube needs bear higher withstand voltage, and this makes the highest input voltage of this topological structure receive obvious restriction. However, when a low voltage is input, as long as the design is reasonable, theoretically, the single-tube flyback converter can still normally output under an extremely low input voltage.
The follow current of the primary coil (caused by induced electromotive force generated by leakage inductance of the primary coil and the like) of the double-tube flyback converter can return to the input bus through the clamping two-position tube, so that the switch tube only needs to bear the withstand voltage of the bus voltage, and the topological structure is easier to apply to the condition of high input voltage. However, when a low voltage is input, that is, when the bus voltage is lower than the voltage reflected from the secondary winding to the primary winding, the clamping diode transmits the energy that should be transmitted to the secondary winding back to the primary winding in a forward mode, so that the secondary winding can only output an output voltage slightly lower than the bus voltage, that is, if the turn ratio of the primary winding to the secondary winding of the transformer is n:1, the secondary output voltage is: vo = Vin/n-VD, where Vo, vin, and VD are the output voltage, the input voltage of the bus, and the voltage drop of the rectifier diode, respectively.
The traditional double-tube flyback converter has problems when low voltage is input, a designer can only avoid the section, the lowest input voltage is firstly determined at the beginning of design, and even if the lowest and highest input voltages in wide-range input cannot be considered at the same time.
It can be seen that the single-tube flyback converter has no advantage at high input voltage, while the dual-tube flyback converter has a problem at low input voltage.
As an example, nowadays, super capacitors are widely used as a backup power source in the field of servo drive, especially for wind power pitch servo drives. When the power grid is electrified, three-phase 400Vac alternating current is input into an alternating current rectification circuit, and 800Vdc can be achieved under the condition of the voltage limit of a rectified bus; when the power grid is in no power supply and the super capacitor serving as a backup power supply needs to be used for working, in order to utilize the energy of the super capacitor to the maximum extent, the voltage of the super capacitor needs to be released as low as possible, the ideal value is zero, and the variation range of the working voltage of the bus voltage is between dozens of volts and 800 Vdc.
SUMMERY OF THE UTILITY MODEL
Based on above-mentioned current situation, the utility model aims to provide a flyback conversion circuit, converter, servo motor and driver thereof to for the realization can be in very wide input voltage normal work, and the withstand voltage value of first switch and second switch can be lower effect provides the hardware basis.
In order to achieve the above object, the utility model adopts the following technical scheme:
a flyback converter circuit comprises a first switch, a second switch, a first diode and a second diode, and further comprises: the driving circuit comprises a third switch, a voltage comparison circuit, a driving circuit and an absorption circuit, wherein the absorption circuit comprises an absorption capacitor and an absorption resistor; one end of the first switch is connected with the bus, and the other end of the first switch is connected with the second end of the primary coil of the transformer; one end of the second switch is connected with the first end of the primary coil, and the other end of the second switch is grounded; the anode of the first diode is connected with the first end of the primary coil, and the cathode of the first diode is connected with the bus; the cathode of the second diode is connected with the second end of the primary coil, and the anode of the second diode is grounded through the third switch; the third switch is connected with the absorption circuit in parallel, and the absorption capacitor and the absorption resistor in the absorption circuit are connected in parallel; the first input end of the voltage comparison circuit is used for inputting bus sampling voltage, the second input end of the voltage comparison circuit is used for inputting threshold voltage, the output end of the voltage comparison circuit is connected with the input end of the driving circuit, and the output end of the driving circuit is connected with the control end of the third switch.
Preferably, the flyback converter further includes a third diode, a cathode of the third diode is connected to an anode of the second diode, and an anode of the third diode is connected to the low potential end of the snubber circuit, or a cathode of the third diode is connected to the high potential end of the snubber circuit, and an anode of the third diode is grounded.
Preferably, the flyback converter circuit further includes a resistor, the third switch is an MOS transistor, and the resistor is bridged between a gate and a source of the MOS transistor.
The utility model also provides a flyback conversion circuit, including first switch, second switch, first diode, second diode, still include: the driving circuit comprises a third switch, a voltage comparison circuit, a driving circuit and an absorption circuit, wherein the absorption circuit comprises an absorption capacitor and an absorption resistor; one end of the first switch is connected with the bus, and the other end of the first switch is connected with the second end of the primary coil of the transformer; one end of the second switch is connected with the first end of the primary coil, and the other end of the second switch is grounded; the anode of the first diode is connected with the first end of the primary coil, and the cathode of the first diode is connected with the bus; the anode of the second diode is grounded, and the cathode of the second diode is connected with the second end of the primary coil through the third switch; the third switch is connected with the absorption circuit in parallel, and the absorption capacitor and the absorption resistor in the absorption circuit are connected in parallel; the first input end of the voltage comparison circuit is used for inputting bus sampling voltage, the second input end of the voltage comparison circuit is used for inputting threshold voltage, the output end of the voltage comparison circuit is connected with the input end of the driving circuit, and the output end of the driving circuit is connected with the control end of the third switch.
Preferably, the flyback converter further includes a third diode, a cathode of the third diode is connected to the second end of the primary coil, and an anode of the third diode is connected to the low potential end of the absorption circuit, or a cathode of the third diode is connected to the high potential end of the absorption circuit, and an anode of the third diode is connected to a cathode of the second diode.
Preferably, the flyback converter circuit further includes a resistor, the third switch is an MOS transistor, and the resistor is bridged between a gate and a source of the MOS transistor.
The utility model also provides a flyback conversion circuit, including first switch, second switch, first diode, second diode, still include: the driving circuit comprises a third switch, a voltage comparison circuit, a driving circuit and an absorption circuit, wherein the absorption circuit comprises an absorption capacitor and an absorption resistor; one end of the first switch is connected with the bus, and the other end of the first switch is connected with the second end of the primary coil of the transformer; one end of the second switch is connected with the first end of the primary coil, and the other end of the second switch is grounded; the cathode of the second diode is connected with the second end of the primary coil, and the anode of the second diode is grounded; the cathode of the first diode is connected with the bus, and the anode of the first diode is connected with the first end of the primary coil through the third switch; the third switch is connected with the absorption circuit in parallel, and the absorption capacitor and the absorption resistor in the absorption circuit are connected in parallel; the first input end of the voltage comparison circuit is used for inputting bus sampling voltage, the second input end of the voltage comparison circuit is used for inputting threshold voltage, the output end of the voltage comparison circuit is connected with the input end of the driving circuit, and the output end of the driving circuit is connected with the control end of the third switch.
Preferably, the flyback converter further includes a third diode, a cathode of the third diode is connected to an anode of the first diode, and an anode of the third diode is connected to the low potential end of the snubber circuit, or a cathode of the third diode is connected to the high potential end of the snubber circuit, and an anode of the third diode is connected to the first end of the primary coil.
Preferably, the flyback converter circuit further includes a resistor, the third switch is an MOS transistor, and the resistor is bridged between a gate and a source of the MOS transistor.
The utility model also provides a flyback conversion circuit, including first switch, second switch, first diode, second diode, still include: the driving circuit comprises a third switch, a voltage comparison circuit, a driving circuit and an absorption circuit, wherein the absorption circuit comprises an absorption capacitor and an absorption resistor; one end of the first switch is connected with the bus, and the other end of the first switch is connected with the second end of the primary coil of the transformer; one end of the second switch is connected with the first end of the primary coil, and the other end of the second switch is grounded; the cathode of the second diode is connected with the second end of the primary coil, and the anode of the second diode is grounded; the anode of the first diode is connected with the first end of the primary coil, and the cathode of the first diode is connected with the bus through the third switch; the third switch is connected with the absorption circuit in parallel, and the absorption capacitor and the absorption resistor in the absorption circuit are connected in parallel; the first input end of the voltage comparison circuit is used for inputting bus sampling voltage, the second input end of the voltage comparison circuit is used for inputting threshold voltage, the output end of the voltage comparison circuit is connected with the input end of the driving circuit, and the output end of the driving circuit is connected with the control end of the third switch.
Preferably, the flyback converter further includes a third diode, a cathode of the third diode is connected to the bus, and an anode of the third diode is connected to the low potential end of the snubber circuit, or a cathode of the third diode is connected to the high potential end of the snubber circuit, and an anode of the third diode is connected to the cathode of the first diode.
Preferably, the flyback converter circuit further includes a resistor, the third switch is an MOS transistor, and the resistor is bridged between a gate and a source of the MOS transistor.
The utility model also provides a flyback converter, including the transformer, still include arbitrary flyback converter circuit.
The utility model also provides a servo motor driver, including the transformer, still include wantonly flyback conversion circuit.
The utility model also provides a servo motor, include the servo motor driver.
[ PROBLEMS ] the present invention
Under the condition that the bus sampling voltage is greater than the threshold voltage, the voltage comparison circuit controls the third switch to be conducted, so that the second diode and the third switch form a clamping circuit of the primary coil, the clamping circuit is similar to a double-tube flyback converter, and the withstand voltage values of a first switch and a second switch of the clamping circuit can be lower; when the bus sampling voltage is smaller than the threshold voltage, the voltage comparison circuit controls the third switch to be switched off, so that the second diode and the absorption circuit form a clamping absorption circuit of the primary coil, and the first end or the second end of the primary coil of the transformer cannot be clamped, so that the problem that the energy of the secondary coil is transmitted back to the primary coil in a forward mode, and the secondary coil can only be slightly lower than the output voltage of the turn ratio of the bus voltage is avoided.
Other beneficial effects of the utility model will be elucidated through the introduction of specific technical characteristics and technical scheme in the detailed description, and through the introduction of these technical characteristics and technical scheme, the skilled person in the art can understand the beneficial technical effect that technical characteristics and technical scheme brought.
Drawings
A preferred embodiment of the flyback converter circuit of the present invention will be described below with reference to the accompanying drawings. In the figure:
fig. 1 is a circuit topology diagram of a single-tube flyback converter circuit in the prior art;
fig. 2 is a schematic circuit topology diagram of a dual-transistor flyback converter circuit in the prior art;
fig. 3 is a flyback converter circuit according to a preferred embodiment of the present invention;
fig. 4 is a flyback converter circuit according to another preferred embodiment of the present invention;
fig. 5 is a flyback converter circuit according to another preferred embodiment of the present invention;
fig. 6 is a flyback converter circuit according to another preferred embodiment of the present invention;
fig. 7 is a flyback converter circuit according to another preferred embodiment of the present invention;
fig. 8 is a flyback converter circuit according to another preferred embodiment of the present invention;
fig. 9 is a flyback converter circuit according to another preferred embodiment of the present invention;
fig. 10 is a flyback converter circuit according to another preferred embodiment of the present invention.
Detailed Description
The present invention will be described below based on examples, but the present invention is not limited to only these examples. In the following detailed description of the present invention, certain specific details are set forth, such that well-known methods, procedures, flows, and components have not been described in detail so as not to obscure the present invention.
Further, those of ordinary skill in the art will appreciate that the drawings provided herein are for illustrative purposes and are not necessarily drawn to scale.
Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is, what is meant is "including, but not limited to".
In the description of the present invention, it is to be understood that the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. In addition, in the description of the present invention, "a plurality" means two or more unless otherwise specified.
The flyback conversion circuit is very suitable for a scene with a wide input voltage variation range, and products applying the flyback conversion circuit can be as follows: the device comprises a switching power supply, a frequency converter, a servo driver, a UPS, an inverter, an energy storage device and the like. Fig. 3 is a flyback converter circuit according to an embodiment of the present invention, the flyback converter circuit is configured to convert the voltage on its bus into an output voltage Vo to be provided to a load, for example, a servo motor (correspondingly, the flyback converter circuit is a component of a servo driver).
The flyback conversion circuit comprises a control unit (not shown in the figure), a driving unit (not shown in the figure), a bus capacitor C1, a first switch Q1, a second switch Q2, a first diode D1 (freewheeling diode), a second diode D2 (freewheeling diode), a third switch Q3, a voltage comparison circuit, an absorption circuit, a transformer T, a rectifier diode D and an output filter capacitor C2, wherein the absorption circuit comprises an absorption capacitor C3 and an absorption resistor R1. The first switch Q1, the second switch Q2 and the third switch Q3 may be MOS transistors, such as N-channel MOS transistors or P-channel MOS transistors, and IGBTs (insulated gate bipolar transistors).
The bus of the flyback converter circuit is grounded through a bus capacitor C1, and the voltage on the bus is derived from the output voltage of the previous stage circuit, which is the input voltage of the flyback converter circuit. The range of the output voltage of the present front-stage circuit is greatly changed, for example, the range of the output voltage is 20V-800V. The front-stage circuit can be a super capacitor (namely a standby power supply) and an alternating current rectification circuit, and the super capacitor and the alternating current rectification circuit respectively work under corresponding conditions; when the power grid is electrified, the alternating current rectifying circuit works, and converts alternating current voltage into direct current voltage to be supplied to the bus; when the power grid is not electrified, the super capacitor works, and output direct-current voltage is supplied to the bus.
One end of the first switch Q1 is connected with the bus, and the other end is connected with a second end T2 of a primary coil of the transformer T; one end of the second switch Q2 is connected with the first end T1 of the primary coil, and the other end is grounded. The anode of the first diode D1 is connected with the first end T1 of the primary coil, and the cathode is connected with the bus. The second diode D2 and the third switch Q3 are connected between the second end T2 of the primary coil and the ground in series; in one embodiment, as shown in fig. 3, the third switch Q3 may be disposed between the anode of the second diode D2 and the ground, and the cathode of the second diode D2 is connected to the second end T2 of the primary winding; in another embodiment, as shown in fig. 4, the third switch Q3 may be disposed between the cathode of the second diode D2 and the second end T2 of the primary coil, and the anode of the second diode D2 is grounded. The third switch Q3 is connected in parallel with an absorption circuit, and an absorption capacitor C3 and an absorption resistor R1 in the absorption circuit are connected in parallel.
The voltage comparison circuit samples the bus voltage V (i.e. the sampling voltage of the input voltage) ’ in is compared with the threshold voltage, when the bus sampling voltage is greater than the threshold voltage, the voltage comparison circuit controls the third switch Q3 to be turned on, so that the second diode D2 and the third switch Q3 form a clamping circuit of the primary coil, and the current (also called continuous current, current generated when the first switch Q1 and the second switch Q2 are turned off in the switching operation period of the first switch Q1 and the second switch Q2) in the clamping circuit is in the direction from the anode of the second diode D2, the cathode of the second diode D2 to the second end T2 of the primary coil, and the third switch Q3 short-circuits the absorption circuit. When the bus sampling voltage is smaller than the threshold voltage, the voltage comparison circuit controls the third switch Q3 to be switched off, so that the second diode D2 and the absorption circuit form a clamping absorption circuit of the primary coil. As shown in fig. 3, in one embodiment, the voltage comparison circuit uses a comparator, one end of which inputs a bus sampling voltage (i.e. a sampling voltage of the input voltage), the other end of which inputs a threshold voltage, and the output end of which outputs a comparison result signal, for example, when the sampling voltage of the input voltage is greater than the threshold voltage, the comparison result signal is at a high level, and when the sampling voltage of the input voltage is less than the threshold voltage, the comparison result signal is at a low level. In some embodiments, the flyback converter further includes a driving circuit, which converts the comparison result signal into a driving signal for driving the third switch Q3, and inputs the driving signal to the control terminal of the third switch Q3 to control the third switch Q3 to be turned on or off; for example, the third switch Q3 is a MOS transistor, the driving signal is input to the gate of the MOS transistor, and a resistor R2 is connected between the gate and the source, so as to provide both a bias voltage for the gate of the third switch Q3 and a quick release path for the accumulated charges on the gate.
One end of a secondary winding of the transformer T is connected with the positive output end Vo + through the rectifier diode D, the other end of the secondary winding of the transformer T is connected with the negative output end Vo-, the two ends of the filter capacitor are respectively connected with the positive output end Vo + and the negative output end Vo-, and output voltage Vo between the positive output end Vo + and the negative output end Vo-is supplied to a load.
Under the condition that the bus sampling voltage is larger than the threshold voltage, after the voltage comparison circuit compares the bus sampling voltage with the threshold voltage to obtain a comparison result, the third switch Q3 is controlled to be conducted, and the third switch Q3 is used for short-circuiting the absorption circuit. The following describes the operation of the flyback converter circuit in the operating cycle in detail: (1) The control unit controls the first switch Q1 and the second switch Q2 to be switched on through a driving unit (not shown in the figure), current flows out from a bus and flows into the ground through the first switch Q1, the primary coil and the second switch Q2, the current excites the transformer T in the process, electric energy is converted into magnetic energy, the rectifier diode D is switched off (namely switched off), and no current exists in the secondary coil. At this time, the voltage of the cathode of the second diode D2 is greater than the voltage of the anode thereof, and thus the second diode D2 is turned off (i.e., turned off); the voltage of the cathode of the first diode D1 is greater than the voltage of the anode thereof, so that the first diode D1 is turned off (i.e., turned off); (2) After the step (1) lasts for a certain time, the control unit controls the first switch Q1 and the second switch Q2 to be switched off through a driving unit (not shown in the figure), the magnetic energy in the transformer T starts to be converted into electric energy, the rectifier diode D is switched on, and the secondary side coil has current; in addition, because the first switch Q1 and the second switch Q2 are disconnected instantly, the leakage inductance of the primary coil generates a large induced electromotive force; the output voltage Vo of the flyback conversion circuit generates a reflected voltage at the primary coil due to the turn ratio of the transformer T (the turn ratio between the primary coil and the secondary coil), and thus the voltage difference between both ends of the primary coil is the sum of the induced electromotive force and the reflected voltage. The voltage of the first end T1 of the primary coil is clamped to the sum of the input voltage and the voltage drop of the first diode D1 (namely Vin + VD 1) due to the clamping of the first diode D1; the voltage of the second end T2 of the primary coil is clamped between 0 and the voltage drop difference (namely-VD 2) of the second diode D2 due to the clamping of the second diode D2; therefore, the continuous current on the primary coil flows out from the first end T1, flows into the bus through the first diode D1, charges the bus capacitor C1, and returns to the second end T2 of the primary coil through the bus capacitor C1 and the second diode D2 to form a continuous current loop.
Under the condition that the bus sampling voltage is smaller than the threshold voltage, the voltage comparison circuit compares the bus sampling voltage with the threshold voltage to obtain a comparison result, then the third switch Q3 is controlled to be switched off, and the second diode D2 and the absorption circuit form a clamping absorption circuit (RCD circuit) of a primary coil, which is similar to the traditional single-tube flyback converter. The following describes the operation of the flyback converter circuit in the operating cycle in detail: (1) The control unit controls the first switch Q1 and the second switch Q2 to be switched on through a driving unit (not shown in the figure), current flows out from a bus and flows into the ground through the first switch Q1, the primary coil and the second switch Q2, the current excites the transformer T in the process, electric energy is converted into magnetic energy, the rectifier diode D is switched off (namely switched off), and no current exists in the secondary coil. At this time, the voltage of the cathode of the second diode D2 is greater than the voltage of the anode thereof, and thus the second diode D2 is turned off (i.e., turned off); the voltage of the cathode of the first diode D1 is greater than the voltage of the anode thereof, so that the first diode D1 is turned off (i.e., turned off); (2) After the step (1) lasts for a certain time, the control unit controls the first switch Q1 and the second switch Q2 to be switched off through a driving unit (not shown in the figure), the magnetic energy in the transformer T starts to be converted into electric energy, the rectifier diode D is switched on, and the secondary side coil has current; in addition, because the first switch Q1 and the second switch Q2 are disconnected instantly, the leakage inductance of the primary coil generates a large induced electromotive force; the output voltage Vo of the flyback conversion circuit generates a reflected voltage at the primary coil due to the turn ratio of the transformer T (the turn ratio between the primary coil and the secondary coil), that is, the voltage difference between the two ends of the primary coil is the sum of the induced electromotive force and the reflected voltage. The voltage of the first end T1 of the primary coil is clamped to the sum of the input voltage and the voltage drop of the first diode D1 (namely Vin + VD 1) due to the clamping of the first diode D1, and the continuous current on the primary coil flows out of the first end T1, flows into a bus through the first diode D1 and charges a bus capacitor C1; because the voltage of the first end T1 of the primary coil is clamped, the voltage of the second end T2 of the primary coil (the voltage of the second end T2 of the primary coil is a negative value) is approximately equal to the sum of the induced electromotive force and the reflected voltage subtracted from the bus voltage, the second diode D2 is conducted, the absorption capacitor C3 starts to charge, and the charging current flows back to the second end T2 of the primary coil after passing through the absorption capacitor C3 and the second diode D2. Due to the charging effect of the absorption capacitor C3, a voltage peak caused by induced electromotive force in the voltage of the second end T2 of the primary coil is also absorbed and becomes gentle; (3) When the absorption capacitor C3 is charged to a certain voltage, and the voltage difference between the absorption capacitor C3 and the second end T2 of the primary coil is smaller than the conduction voltage drop of the second diode D2, the charging of the absorption capacitor C3 is cut off (i.e., turned off); (4) The absorption capacitor C3 can discharge through the absorption resistor R1, the discharge current flows out from the high potential end P32 (the end connected with the ground) of the absorption capacitor C3, flows into the low potential end P31 (the end in common with the anode of the second diode D2) of the absorption capacitor C3 through the absorption resistor R1, and after discharging to a certain voltage value, the flyback conversion circuit starts to enter the steps (1) - (3) of the next period, wherein in the step (1) of the next period, the cathode voltage of the second diode D2 is the bus voltage, the anode voltage of the second diode D2 is the negative voltage of the low potential end P31, and at this time, the second diode D2 is turned off; the absorption capacitor C3 starts to charge again after step (3) of the next cycle. Therefore, when the bus sampling voltage is smaller than the threshold voltage, the voltage VC3 at the low potential terminal P31 of the absorption capacitor C3 can be stably maintained at least below a certain voltage value (negative value) (i.e., at least a certain amount of stored electric energy) related to the capacitance value of the absorption capacitor C3, the resistance value of the absorption resistor R1, and the duty ratio of the on-time of the first switch Q1 and the second switch Q2 during the operation of the flyback converter circuit. Therefore, under the condition that the bus sampling voltage is less than the threshold voltage, the second end T2 of the primary coil is not clamped at the input voltage, so that the flyback conversion circuit can work normally, and the problem that the energy of the secondary coil is transmitted back to the primary coil in a forward mode, so that the secondary coil can only obtain the output voltage slightly lower than the turn ratio of the bus voltage is solved.
In some embodiments, the output voltage Vo of the flyback converter circuit (which is output by the secondary winding of the transformer T through the rectifier diode D) is generally adjustable, for example, 20V needs to be output in some scenarios, and 48V needs to be output in some scenarios, and the control unit may adjust the output voltage Vo of the flyback converter circuit to a new voltage value by adjusting the duty ratios of the on-time of the first switch Q1 and the second switch Q2. When the output voltage Vo is adjusted to a new voltage value, the control unit updates the threshold voltage and outputs the updated threshold voltage to the voltage comparison circuit; wherein the control unit updates the threshold voltage to a greater threshold voltage when the output voltage Vo is adjusted to a greater voltage value, and updates the threshold voltage to a smaller threshold voltage when the output voltage Vo is adjusted to a smaller voltage value; and finally, the control unit outputs the updated threshold voltage to the voltage comparison circuit. The voltage comparison circuit controls the third switch Q3 to turn on or off according to the updated threshold voltage.
In some embodiments, the magnitude of the determined threshold voltage Vth is calculated by the output voltage Vo and the voltage drop VD of the rectifying diode D: vth = k × n (Vo + VD); wherein n is the turn ratio of the primary coil and the secondary coil of the transformer T, k is a sampling coefficient, and the range of values is (0, 1), that is, k = V 'in/Vin (Vin is the bus voltage, and V' in is the bus sampling voltage). In the above relation, when the first switch Q1 and the second switch Q2 are turned off, instantaneous oscillation or fluctuation of the voltage difference between the two ends of the primary winding of the transformer T is ignored, and it is roughly considered that the threshold voltage Vth = k × n (Vo + VD) is quite appropriate, the flyback conversion circuit normally operates between the input voltage intervals vin.min-Vth, and the voltage of the second end of the primary winding of the transformer T is not clamped at-VD 2; the voltage-stabilizing circuit has the advantages of a traditional double-tube flyback conversion circuit when the voltage is input within the interval Vth-vin.max; where vin.min and vin.max are the minimum and maximum values of the input voltage, respectively.
In some embodiments, when considering the transient oscillation or fluctuation of the voltage difference across the primary winding of the transformer T when the first switch Q1 and the second switch Q2 are turned off, some margin may be added to the threshold voltage Vth, that is, the magnitude of the threshold voltage Vth is calculated and determined by the output voltage Vo and the voltage drop VD of the rectifier diode D: vth = k (n (Vo + VD) + V1); wherein V1 is a constant between 5V-10V.
As described above, in the embodiment shown in fig. 4, the third switch Q3 may be disposed between the cathode of the second diode D2 and the second end T2 of the primary coil, the anode of the second diode D2 is grounded, and the working process of the flyback converter in the working period is the same as that of the flyback converter in fig. 3 in principle, and the specific process is different, for example, when the bus sampling voltage is less than the threshold voltage, and when the absorption capacitor C3 is charged to a certain voltage in the working process step (3), the voltage difference between the high potential end P32 (correspondingly, P31 is the low potential end) and the ground (voltage is 0) is less than the conducting voltage drop of the second diode D2, the charging of the absorption capacitor C3 is cut off.
In some embodiments, as shown in fig. 5, the flyback converter further includes a third diode D3, the absorption circuit is connected in series with the third diode D3 and then connected in parallel with the third switch Q3, and at the moment when the third switch Q3 is turned on, the third diode D3 is used to prevent the electric quantity of the absorption capacitor from discharging through the third switch Q3; the third diode D3 forms part of the snubber clamp after the third switch Q3 is turned off. For example, the cathode of the third diode D3 is connected to the anode of the first diode D1, and the anode is connected to the low potential terminal P31 of the snubber circuit. As another example, the cathode of the third diode D3 is connected to the high potential terminal P32, and the anode is grounded (not shown). As mentioned above, in the case that the bus sampling voltage is smaller than the threshold voltage, the absorption capacitor C3 has a voltage value, when the bus sampling voltage changes to be larger than the threshold voltage, the third switch Q3 is controlled to be turned on, and due to the presence of the third diode D3, the voltage on the absorption capacitor C3 is discharged through the absorption resistor R1; otherwise, if the third diode D3 does not exist, at the moment when the third switch Q3 is controlled to be turned on, the third switch Q3 is turned on to short-circuit the absorption capacitor C3, and the voltage of the absorption capacitor C3 is instantaneously loaded on the third switch Q3, so that an instantaneous peak current is generated, thereby causing damage to the third switch Q3. Similarly, the flyback converter circuit in fig. 4 may also include a third diode D3, where at the instant when the third switch Q3 is turned on, the third diode D3 is used to prevent the electric quantity of the absorption capacitor from discharging through the third switch Q3; after the third switch Q3 is turned off, the third diode D3 forms part of the snubber clamp. As shown in fig. 9, the absorption circuit is connected in series with the third diode D3 and then connected in parallel with the third switch Q3, the cathode of the third diode D3 is connected to the second end T2 of the primary winding T, and the anode is connected to the low potential end P31 of the absorption circuit; for another example, the cathode of the third diode D3 is connected to the high potential terminal P32, and the anode is connected to the cathode (not shown) of the second diode D2.
Fig. 6 is a flyback converter circuit according to another embodiment of the present invention, which is substantially similar to the flyback converter circuit of fig. 3.
The bus of the flyback converter circuit is grounded through a bus capacitor C1, and the voltage on the bus is derived from the output voltage of the previous stage circuit, which is the input voltage of the flyback converter circuit. The range of the output voltage of the preceding stage circuit is changed greatly, for example, the change range is 20V-800V, the preceding stage circuit can be a super capacitor and an alternating current rectification circuit, and the super capacitor and the alternating current rectification circuit respectively work under corresponding conditions; when the power grid is electrified, the alternating current rectifying circuit works, and converts alternating current voltage into direct current voltage to be supplied to the bus; when the power grid is not electrified, the super capacitor works, and output direct-current voltage is supplied to the bus.
One end of the first switch Q1 is connected with the bus, and the other end is connected with a second end T2 of a primary coil of the transformer T; one end of the second switch Q2 is connected with the first end T1 of the primary coil, and the other end is grounded. The cathode of the second diode D2 is connected to the second end T2 of the primary coil, and the anode is grounded. The first diode D1 and the third switch Q3 are connected in series between the bus and the first end T1 of the primary coil; in one embodiment, as shown in fig. 6, the third switch Q3 may be disposed between the anode of the first diode D1 and the first end T1 of the primary coil, the cathode of the first diode D1 being connected to the bus; in another embodiment, as shown in fig. 7, the third switch Q3 may be disposed between the bus bar and the cathode of the first diode D1, and the anode of the first diode D1 is connected to the first end T1 of the primary winding. The third switch Q3 is connected in parallel with an absorption circuit, and an absorption capacitor C3 and an absorption resistor R1 in the absorption circuit are connected in parallel.
The voltage comparison circuit compares the bus sampling voltage (i.e., the sampling voltage of the input voltage) with a threshold voltage, and when the bus sampling voltage is greater than the threshold voltage, the voltage comparison circuit controls the third switch Q3 to be turned on, so that the first diode D1 and the third switch Q3 form a clamping circuit of the primary coil, and a current (also referred to as a follow current, a current generated when the first switch Q1 and the second switch Q2 are turned off in a switching operation period of the first switch Q1 and the second switch Q2) in the clamping circuit is directed from an anode of the first diode D1, a cathode of the first diode D1 to the bus, and so that the third switch Q3 short-circuits the snubber circuit. When the bus sampling voltage is smaller than the threshold voltage, the voltage comparison circuit controls the third switch Q3 to be switched off, so that the first diode D1 and the absorption circuit form a clamping absorption circuit of the primary coil. As shown in fig. 6, in one embodiment, the voltage comparison circuit uses a comparator, one end of which inputs a bus sampling voltage (i.e. a sampling voltage of the input voltage), the other end of which inputs a threshold voltage, and the output end of which outputs a comparison result signal, for example, when the sampling voltage of the input voltage is greater than the threshold voltage, the comparison result signal is at a high level, and when the sampling voltage of the input voltage is less than the threshold voltage, the comparison result signal is at a low level. In some embodiments, the flyback converter further includes a driving circuit, which converts the comparison result signal into a driving signal for driving the third switch Q3, and inputs the driving signal to the control terminal of the third switch Q3 to control the third switch Q3 to be turned on or off; for example, the third switch Q3 is a MOS transistor, the driving signal is input to the gate of the MOS transistor, and a resistor R2 is connected between the gate and the source, so as to provide both a bias voltage for the gate of the third switch Q3 and a quick release path for the accumulated charges on the gate.
One end of a secondary winding of the transformer T is connected with the positive output end Vo + through the rectifier diode D, the other end of the secondary winding of the transformer T is connected with the negative output end Vo-, the two ends of the filter capacitor are respectively connected with the positive output end Vo + and the negative output end Vo-, and the output voltage Vo between the positive output end Vo + and the negative output end Vo-is supplied to a load.
Under the condition that the bus sampling voltage is larger than the threshold voltage, after the voltage comparison circuit obtains a comparison result by comparing the bus sampling voltage with the threshold voltage, the third switch Q3 is controlled to be conducted, and the third switch Q3 is used for short-circuiting the absorption circuit. The following describes the operation process of the flyback converter circuit in the working period in detail: (1) The control unit controls the first switch Q1 and the second switch Q2 to be switched on through a driving unit (not shown in the figure), current flows out from a bus and flows into the ground through the first switch Q1, the primary coil and the second switch Q2, the current excites the transformer T in the process, electric energy is converted into magnetic energy, at the moment, the rectifier diode D is cut off (namely switched off), and no current flows in the secondary coil. At this time, the voltage of the cathode of the second diode D2 is greater than the voltage of the anode thereof, and thus the second diode D2 is turned off (i.e., turned off); the voltage of the cathode of the first diode D1 is greater than the voltage of the anode thereof, and thus the first diode D1 is turned off (i.e., turned off); (2) After the step (1) lasts for a certain time, the control unit controls the first switch Q1 and the second switch Q2 to be switched off through a driving unit (not shown in the figure), the magnetic energy in the transformer T starts to be converted into electric energy, the rectifier diode D is switched on, and the secondary side coil has current; in addition, because the first switch Q1 and the second switch Q2 are disconnected instantly, the leakage inductance of the primary coil generates a large induced electromotive force; the output voltage Vo of the flyback conversion circuit generates a reflected voltage at the primary coil due to the turn ratio of the transformer T (the turn ratio between the primary coil and the secondary coil), and thus the voltage difference between both ends of the primary coil is the sum of the induced electromotive force and the reflected voltage. The voltage of the first end T1 of the primary coil is clamped to the sum of the input voltage and the voltage drop of the first diode D1 (namely Vin + VD 1) due to the clamping of the first diode D1; the voltage of the second end T2 of the primary coil is clamped between 0 and the voltage drop difference (namely-VD 2) of the second diode D2 due to the clamping of the second diode D2; therefore, the continuous current on the primary coil flows out from the first end T1, flows into the bus through the first diode D1, charges the bus capacitor C1, and returns to the second end T2 of the primary coil through the bus capacitor C1 and the second diode D2 to form a continuous current loop.
Under the condition that the bus sampling voltage is smaller than the threshold voltage, the voltage comparison circuit compares the bus sampling voltage with the threshold voltage to obtain a comparison result, then the third switch Q3 is controlled to be switched off, and the first diode D1 and the absorption circuit form a clamping absorption circuit of the primary coil. The following describes the operation of the flyback converter circuit in the operating cycle in detail: (1) The control unit controls the first switch Q1 and the second switch Q2 to be switched on through a driving unit (not shown in the figure), current flows out from a bus and flows into the ground through the first switch Q1, the primary coil and the second switch Q2, the current excites the transformer T in the process, electric energy is converted into magnetic energy, at the moment, the rectifier diode D is cut off (namely switched off), and no current flows in the secondary coil. At this time, the voltage of the cathode of the second diode D2 is greater than the voltage of the anode thereof, and thus the second diode D2 is turned off (i.e., turned off); the voltage of the cathode of the first diode D1 is greater than the voltage of the anode thereof, so that the first diode D1 is turned off (i.e., turned off); (2) After the step (1) lasts for a certain time, the control unit controls the first switch Q1 and the second switch Q2 to be switched off through a driving unit (not shown in the figure), the magnetic energy in the transformer T starts to be converted into electric energy, the rectifier diode D is switched on, and the secondary side coil has current; in addition, because the first switch Q1 and the second switch Q2 are disconnected instantly, the leakage inductance of the primary coil generates a large induced electromotive force; the output voltage Vo of the flyback conversion circuit generates a reflected voltage at the primary coil due to the turn ratio of the transformer T (the turn ratio between the primary coil and the secondary coil), that is, the voltage difference between the two ends of the primary coil is the sum of the induced electromotive force and the reflected voltage. The voltage of the second end T2 of the primary coil is clamped at the difference (namely-VD 2) between 0 and the voltage drop of the second diode D2 due to the clamping of the second diode D2, and the charging current on the bus capacitor C1 flows out of the bus capacitor C1, passes through the second diode D2 and then flows into the second end T2 of the primary coil; because the voltage of the second end T2 of the primary coil is clamped, the voltage of the first end T1 of the primary coil (the voltage of the first end T1 of the primary coil is a positive value) is approximately equal to the sum of the induced electromotive force and the reflected voltage, the first diode D1 is conducted, the absorption capacitor C3 starts to charge, the charging current flows out from the first end T1 of the primary coil, and flows back to the bus after passing through the absorption capacitor C3 and the first diode D1, and the bus capacitor C1 is charged. Due to the charging effect of the absorption capacitor C3, a voltage peak caused by induced electromotive force in the voltage of the first end T1 of the primary coil is also absorbed and becomes gentle; (3) When the high potential end of the absorption capacitor C3 is charged to a certain voltage and the voltage difference between the low potential end of the absorption capacitor C3 and the bus is smaller than the conduction voltage drop of the second diode D2, the charging of the absorption capacitor C3 is cut off (namely, is cut off); (4) The absorption capacitor C3 can discharge through the absorption resistor R1, the discharge current flows out from a high potential end P32 (one end connected with the first end T1 of the primary coil) of the absorption capacitor C3, flows into a low potential end P31 (one end which is in common with the anode of the first diode D1) of the absorption capacitor C3 after passing through the absorption resistor R1, and after discharging to a certain voltage value, the flyback conversion circuit starts to enter the steps (1) - (3) of the next period, wherein in the step (1) of the next period, the cathode voltage of the first diode D1 is the bus voltage, the anode voltage of the first diode D1 is the voltage of the low potential end P31, and the first diode D1 is cut off at the moment; the absorption capacitor C3 starts to charge again after step (3) of the next cycle. Therefore, when the bus sampling voltage is smaller than the threshold voltage, the voltage VC3 of the high potential terminal P32 of the absorption capacitor C3 can be stably maintained at least below a certain voltage value (i.e., at least a certain amount of stored electric energy) related to the capacitance value of the absorption capacitor C3, the resistance value of the absorption resistor R1, and the duty ratio of the on-time of the first switch Q1 and the second switch Q2 during the operation of the flyback converter circuit. Therefore, under the condition that the bus sampling voltage is less than the threshold voltage, the voltage of the first end T1 of the primary coil cannot be clamped at the input voltage, so that the flyback conversion circuit can work normally, and the problem that the energy of the secondary coil is transmitted back to the primary coil in a forward mode, so that the secondary coil can only obtain the output voltage slightly lower than the turn ratio of the bus voltage is solved.
Similarly, in some embodiments, when the output voltage Vo is adjusted to a new voltage value, the control unit updates the threshold voltage and outputs the updated threshold voltage to the voltage comparison circuit; wherein the control unit updates the threshold voltage to a greater threshold voltage when the output voltage Vo is adjusted to a greater voltage value, and updates the threshold voltage to a smaller threshold voltage when the output voltage Vo is adjusted to a smaller voltage value; and finally, the control unit outputs the updated threshold voltage to the voltage comparison circuit. The voltage comparison circuit controls the third switch Q3 to be turned on or off according to the updated threshold voltage.
In some embodiments, the magnitude of the determined threshold voltage Vth is calculated by the output voltage Vo and the voltage drop VD of the rectifying diode D: vth = k × n (Vo + VD); wherein n is the turn ratio of the primary coil and the secondary coil of the transformer T, k is a sampling coefficient, and the numeric area is (0, 1), that is, k = V 'in/Vin (Vin is the bus voltage, and V' in is the bus sampling voltage). In the above relation, when the first switch Q1 and the second switch Q2 are turned off, the transient oscillation or fluctuation of the voltage difference across the primary winding of the transformer T is ignored, and it is roughly considered that the threshold voltage Vth = k × n (Vo + VD) is quite appropriate, the flyback conversion circuit normally operates between the input voltage intervals vin.min-Vth, and the voltage of the second end of the primary winding of the transformer T is not clamped to-VD 2; the voltage-stabilizing circuit has the advantages of a traditional double-tube flyback conversion circuit when the voltage is input within the interval Vth-vin.max; wherein vin.min and vin.max are the minimum and maximum values of the input voltage, respectively.
In some embodiments, when considering the transient oscillation or fluctuation of the voltage difference across the primary winding of the transformer T when the first switch Q1 and the second switch Q2 are turned off, some margin may be added to the threshold voltage Vth, that is, the magnitude of the threshold voltage Vth is calculated and determined by the output voltage Vo and the voltage drop VD of the rectifier diode D: vth = k (n (Vo + VD) + V1); v1 is a constant between 5V and 10V, k is a sampling coefficient, and the value range is (0, 1), that is, k = V 'in/Vin (Vin is a bus voltage, and V' in is a bus sampling voltage).
As described above, in the embodiment shown in fig. 7, the third switch Q3 may be disposed between the cathode of the first diode D1 and the bus, the anode of the first diode D1 is connected to the first end T1 of the primary coil, and the working process of the flyback converter in the working period is the same as that of the flyback converter in fig. 6 in principle, and the specific process is different, for example, when the bus sampling voltage is less than the threshold voltage, and when the absorption capacitor C3 is charged to a certain voltage in the working process step (3), the voltage difference between the high potential end P32 (correspondingly, P31 is the low potential end) and the first end T1 of the primary coil is less than the on-state voltage drop of the first diode D1, the charging of the absorption capacitor C3 is cut off.
In some embodiments, the flyback converter circuit of fig. 7 further includes a third diode D3, as shown in fig. 8, the snubber circuit is connected in series with the third diode D3 and then connected in parallel with the third switch Q3, and at the instant when the third switch Q3 is turned on, the third diode D3 is used to prevent the electric quantity of the snubber capacitor from discharging through the third switch Q3; the third diode D3 forms part of the snubber clamp after the third switch Q3 is turned off. For example, the cathode of the third diode D3 is connected to the bus bar, and the anode is connected to the low potential terminal P31 of the snubber circuit. For another example, the cathode of the third diode D3 is connected to the high potential terminal P32, and the anode is connected to the cathode of the first diode D2 (not shown). As mentioned above, in the case that the bus sampling voltage is smaller than the threshold voltage, the absorption capacitor C3 has a voltage value, when the bus sampling voltage changes to be larger than the threshold voltage, the third switch Q3 is controlled to be turned on, and due to the presence of the third diode D3, the voltage on the absorption capacitor C3 is discharged through the absorption resistor R1; otherwise, if the third diode D3 does not exist, at the moment when the third switch Q3 is controlled to be turned on, the third switch Q3 is turned on to short-circuit the absorption capacitor C3, and the voltage of the absorption capacitor C3 is instantaneously loaded on the third switch Q3, an instantaneous high voltage is generated, thereby damaging the third switch Q3. Similarly, the flyback converter in fig. 6 may also include a third diode D3, as shown in fig. 10, the snubber circuit is connected in series with the third diode D3 and then connected in parallel with the third switch Q3, the cathode of the third diode D3 is connected to the anode of the first diode D1, and the anode is connected to the low potential terminal P31 of the snubber circuit; for another example, the cathode of the third diode D3 is connected to the high potential terminal P32 of the snubber circuit, and the anode is connected to the first terminal T1 of the primary winding.
It will be appreciated by those skilled in the art that the above-described preferred embodiments may be freely combined, superimposed, without conflict.
It will be appreciated by those skilled in the art that the various preferences described above can be freely combined, superimposed without conflict.
It should be understood that the above-described embodiments are illustrative only and not restrictive, and that various obvious or equivalent modifications and substitutions may be made by those skilled in the art without departing from the basic principles of the invention, and are intended to be included within the scope of the appended claims.
Claims (15)
1. A flyback converter circuit comprises a first switch, a second switch, a first diode and a second diode, and is characterized by further comprising: the driving circuit comprises a third switch, a voltage comparison circuit, a driving circuit and an absorption circuit, wherein the absorption circuit comprises an absorption capacitor and an absorption resistor;
one end of the first switch is connected with the bus, and the other end of the first switch is connected with the second end of the primary coil of the transformer; one end of the second switch is connected with the first end of the primary coil, and the other end of the second switch is grounded;
the anode of the first diode is connected with the first end of the primary coil, and the cathode of the first diode is connected with the bus;
the cathode of the second diode is connected with the second end of the primary coil, and the anode of the second diode is grounded through the third switch; the third switch is connected with the absorption circuit in parallel, and the absorption capacitor and the absorption resistor in the absorption circuit are connected in parallel;
the first input end of the voltage comparison circuit is used for inputting bus sampling voltage, the second input end of the voltage comparison circuit is used for inputting threshold voltage, the output end of the voltage comparison circuit is connected with the input end of the driving circuit, and the output end of the driving circuit is connected with the control end of the third switch.
2. The flyback converter of claim 1,
a third diode is also included and is included,
the cathode of the third diode is connected to the anode of the second diode, and the anode is connected to the low potential end of the absorption circuit, or,
the cathode of the third diode is connected with the high potential end of the absorption circuit, and the anode of the third diode is grounded.
3. The flyback converter circuit of claim 1 or 2,
the third switch is an MOS tube, and the resistor is bridged between the grid electrode and the source electrode of the MOS tube.
4. A flyback converter circuit comprises a first switch, a second switch, a first diode and a second diode, and is characterized by further comprising: the driving circuit comprises a third switch, a voltage comparison circuit, a driving circuit and an absorption circuit, wherein the absorption circuit comprises an absorption capacitor and an absorption resistor;
one end of the first switch is connected with the bus, and the other end of the first switch is connected with the second end of the primary coil of the transformer; one end of the second switch is connected with the first end of the primary coil, and the other end of the second switch is grounded;
the anode of the first diode is connected with the first end of the primary coil, and the cathode of the first diode is connected with the bus;
the anode of the second diode is grounded, and the cathode of the second diode is connected with the second end of the primary coil through the third switch; the third switch is connected with the absorption circuit in parallel, and the absorption capacitor and the absorption resistor in the absorption circuit are connected in parallel;
the first input end of the voltage comparison circuit is used for inputting bus sampling voltage, the second input end of the voltage comparison circuit is used for inputting threshold voltage, the output end of the voltage comparison circuit is connected with the input end of the driving circuit, and the output end of the driving circuit is connected with the control end of the third switch.
5. The flyback converter of claim 4,
a third diode is also included and is included,
the cathode of the third diode is connected to the second end of the primary coil, and the anode is connected to the low potential end of the absorption circuit, or,
the cathode of the third diode is connected with the high potential end of the absorption circuit, and the anode of the third diode is connected with the cathode of the second diode.
6. The flyback converter of claim 4,
the third switch is an MOS tube, and the resistor is bridged between the grid electrode and the source electrode of the MOS tube.
7. A flyback converter circuit comprises a first switch, a second switch, a first diode and a second diode, and is characterized by further comprising: the driving circuit comprises a third switch, a voltage comparison circuit, a driving circuit and an absorption circuit, wherein the absorption circuit comprises an absorption capacitor and an absorption resistor;
one end of the first switch is connected with the bus, and the other end of the first switch is connected with the second end of the primary coil of the transformer; one end of the second switch is connected with the first end of the primary coil, and the other end of the second switch is grounded;
the cathode of the second diode is connected with the second end of the primary coil, and the anode of the second diode is grounded;
the cathode of the first diode is connected with the bus, and the anode of the first diode is connected with the first end of the primary coil through the third switch; the third switch is connected with the absorption circuit in parallel, and the absorption capacitor and the absorption resistor in the absorption circuit are connected in parallel;
the first input end of the voltage comparison circuit is used for inputting bus sampling voltage, the second input end of the voltage comparison circuit is used for inputting threshold voltage, the output end of the voltage comparison circuit is connected with the input end of the driving circuit, and the output end of the driving circuit is connected with the control end of the third switch.
8. The flyback converter of claim 7,
and a third diode is also included, and,
the cathode of the third diode is connected to the anode of the first diode, and the anode is connected to the low potential terminal of the snubber circuit, or,
and the cathode of the third diode is connected with the high potential end of the absorption circuit, and the anode of the third diode is connected with the first end of the primary coil.
9. The flyback converter of claim 7,
the third switch is an MOS tube, and the resistor is bridged between the grid electrode and the source electrode of the MOS tube.
10. A flyback converter circuit comprises a first switch, a second switch, a first diode and a second diode, and is characterized by further comprising: the driving circuit comprises a third switch, a voltage comparison circuit, a driving circuit and an absorption circuit, wherein the absorption circuit comprises an absorption capacitor and an absorption resistor;
one end of the first switch is connected with the bus, and the other end of the first switch is connected with the second end of the primary coil of the transformer; one end of the second switch is connected with the first end of the primary coil, and the other end of the second switch is grounded;
the cathode of the second diode is connected with the second end of the primary coil, and the anode of the second diode is grounded;
the anode of the first diode is connected with the first end of the primary coil, and the cathode of the first diode is connected with the bus through the third switch; the third switch is connected with the absorption circuit in parallel, and the absorption capacitor and the absorption resistor in the absorption circuit are connected in parallel;
the first input end of the voltage comparison circuit is used for inputting bus sampling voltage, the second input end of the voltage comparison circuit is used for inputting threshold voltage, the output end of the voltage comparison circuit is connected with the input end of the driving circuit, and the output end of the driving circuit is connected with the control end of the third switch.
11. The flyback converter of claim 10,
and a third diode is also included, and,
the cathode of the third diode is connected with a bus, the anode of the third diode is connected with the low potential end of the absorption circuit, or,
the cathode of the third diode is connected with the high potential end of the absorption circuit, and the anode of the third diode is connected with the cathode of the first diode.
12. The flyback converter of claim 10,
the third switch is an MOS tube, and the resistor is bridged between the grid electrode and the source electrode of the MOS tube.
13. A flyback converter comprising a transformer and further comprising a flyback converter circuit as claimed in any of claims 1-12.
14. A servo motor driver comprising a transformer, further comprising a flyback converter circuit as claimed in any of claims 1-12.
15. A servo motor comprising a servo motor driver according to claim 14.
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| CN202221722047.5U CN218473035U (en) | 2022-07-04 | 2022-07-04 | Flyback conversion circuit, converter, servo motor and driver of servo motor |
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