CN114552966A

CN114552966A - Switching power supply for stepping motor driver

Info

Publication number: CN114552966A
Application number: CN202210020936.5A
Authority: CN
Inventors: 华庆; 郝新源; 陈曦童; 王寰宇
Original assignee: Shandong Normal University
Current assignee: Shandong Normal University
Priority date: 2022-01-10
Filing date: 2022-01-10
Publication date: 2022-05-27

Abstract

The invention belongs to the field of circuits, and provides a switching power supply for a stepping motor driver, which comprises a self-excitation starting circuit and an excitation control circuit, wherein the self-excitation starting circuit comprises a first power switching circuit and a high-frequency transformer, and the excitation control circuit comprises a PWM chip, a second power switching circuit and an excitation transformer; the first power switch circuit is connected with the high-frequency transformer, and after the power supply is conducted, the first power switch circuit generates self-excitation, so that the high-frequency transformer generates interactive electromotive force to respectively supply power to the exciting transformer and the PWM chip; the PWM chip is connected with the exciting transformer, outputs PWM signals, excites the change of electromotive force of a winding in the transformer by controlling the second power switch circuit, and then controls and starts the first power switch circuit, so that the high-frequency transformer generates high-frequency electromotive force to supply power for the stepping motor driver.

Description

Switching power supply for stepping motor driver

Technical Field

The invention belongs to the field of circuits, and particularly relates to a switching power supply for a stepping motor driver.

Background

The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.

With the development of semiconductor technology, the technology of switching power supplies has been developed rapidly. The switching power supply is being miniaturized, speeded up, and intelligentized. However, the conventional analog control switching power supply cannot meet all application requirements. The stepping motor has high precision and simple structure, and is widely applied to various industries. The general switching power supply is suitable for being used in occasions where resistive loads and loads are relatively stable, the stepping motor drives the whole system to be an environment where inductive loads and load changes are relatively large, the requirement on the switching power supply is high, in the aspect of supplying power for driving the stepping motor, because the motor is a large-inductance type load when working, instantaneous high voltage can be formed on a power supply end, and under the high-voltage condition, the working voltage ripple peak value of a stepping motor driver cannot exceed the highest rated voltage of the driver.

The general switching power supply adopts a self-excitation control type switching power supply or an independent excitation type switching power supply, and has the defects of poor stability of oscillation frequency, difficulty in control by a control circuit, interference on the circuit, instability of the power supply, poor overload performance, protective turn-off, insufficient output torque or step loss of a stepping motor when the power is insufficient, oscillation, high power consumption and other faults easily occur, and finally the motor and the switching power supply are damaged.

Disclosure of Invention

In order to solve at least one technical problem in the background art, a first aspect of the present invention provides a switching power supply for a stepping motor driver, which employs a self-excited start to excite a controlled half-bridge type switching power supply, so as to improve the working efficiency of the power supply, and also match the working frequency of the stepping motor driver, thereby ensuring that the required power output of the motor is satisfied.

In order to achieve the purpose, the invention adopts the following technical scheme:

a switching power supply for a stepper motor driver, comprising: the self-excitation starting circuit comprises a first power switch circuit and a high-frequency transformer, and the self-excitation control circuit comprises a PWM chip, a second power switch circuit and an exciting transformer;

the first power switch circuit is connected with the high-frequency transformer, and after the power supply is conducted, the first power switch circuit generates self-excitation, so that the high-frequency transformer generates interactive electromotive force to respectively supply power to the exciting transformer and the PWM chip;

the PWM chip is connected with the exciting transformer, outputs PWM signals, excites the change of electromotive force of a winding in the transformer by controlling the second power switch circuit, and then controls and starts the first power switch circuit, so that the high-frequency transformer generates high-frequency electromotive force to supply power for the stepping motor driver.

In one embodiment, the first power switch circuit includes a first switch tube and a second switch tube, the high-frequency transformer includes a main winding and a feedback winding, collectors of the first switch tube and the second switch tube are connected to the main winding, the first switch transistor and the second switch transistor are self-excited, alternately switched on and switched off after being powered on, and the feedback winding generates mutual inductance to respectively supply power to the excitation transformer and the PWM chip.

In one embodiment, the excitation transformer includes a plurality of primary windings and a plurality of secondary windings, the first secondary winding is connected to the base of the first switching transistor, the second secondary winding is connected to the base of the second switching transistor, after the base of the first switching transistor receives a voltage, the collector and the emitter of the first switching transistor are turned on, the voltage begins to drop, after the voltage is turned on, a current flows out from the emitter, and at the time, the second switching transistor is in an off state, and the current flows to the primary winding.

In one embodiment, the second power switching circuit includes a third switching transistor and a fourth switching transistor, the PWM chip includes a plurality of pins, a first pin is connected to a base of the third switching transistor, and a second pin is connected to a base of the fourth switching transistor.

The main winding generates self-inductance in the self-excitation process of the first switching triode and the second switching triode, the feedback winding generates induced voltage, a middle tap is arranged in the middle of the feedback winding, and the induced voltage is output through a pin position of the feedback winding.

As an embodiment, the PWM chip is connected to the primary winding to control the mutual conduction of the primary winding, and the secondary winding also generates an alternating current due to the mutual inductance, so as to further control the mutual conduction of the first switching transistor and the second switching transistor, so that the first switching transistor and the second switching transistor output a square wave having the same frequency as the PWM chip, thereby achieving a loaded charge in the primary winding of the high-frequency transformer and outputting an induced voltage.

In one embodiment, when the first switching transistor is turned on and the second switching transistor is turned off, the voltage applied across the excitation transformer is half of the bus voltage, and energy is transferred from the primary winding to the secondary winding.

As an embodiment, the primary winding includes a first winding, a second winding, and a third winding, the first winding and the second winding are conducted through a collector and an emitter of a third switching transistor, a base of a fourth switching transistor is conducted at the same time, and the second winding and the third winding are conducted through a fourth switching transistor.

In one embodiment, the PWM chip outputs a PWM signal to drive the excitation transformer to control the first switching transistor and the second switching transistor by controlling the third switching transistor and the fourth switching transistor, so that the main winding of the high frequency transformer outputs a mutual inductance to the main winding to generate an oscillator circuit.

In one embodiment, the control circuit is configured to connect a capacitor in series with the primary winding of the drive transformer.

The invention has the beneficial effects that:

the self-excited starting is a half-bridge switch power supply which is excited and controlled, under the condition of using the same power switch tube, the power which is twice as high as the original output power can be obtained, and the voltage applied to the power switch tube in the half-bridge converter circuit is lower and is not higher than the value of the input direct-current power supply voltage. The problem of poor stability of high-speed operation of the motor is solved, the working efficiency of a power supply is improved, and the working frequency of a stepping motor driver can be matched, so that the power output required by the motor is ensured to be met.

The switching power supply has large capacity and good surge impact capability and is suitable for driving the stepping motor. Therefore, the stepping motor can fully exert the characteristics thereof under the conditions of high input voltage and high output power.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.

Fig. 1 is a schematic diagram of the overall circuit structure of a switching power supply for a stepping motor driver in an embodiment of the present invention;

FIG. 2 is a schematic diagram of a self-excited starting circuit according to an embodiment of the present invention;

fig. 3 is a schematic diagram of the excitation control circuit in the embodiment of the invention.

Detailed Description

The invention is further described with reference to the following figures and examples.

It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

In the present invention, terms such as "upper", "lower", "left", "right", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only terms of relationships determined for convenience in describing structural relationships of the components or elements of the present invention, and do not denote any components or elements of the present invention, and are not to be construed as limiting the present invention.

In the present invention, terms such as "connected" and the like are to be understood in a broad sense and mean either fixedly connected or integrally connected or detachably connected; may be directly connected or indirectly connected through an intermediate. The specific meanings of the above terms in the present invention can be determined according to specific situations by persons skilled in the relevant scientific or technical field, and are not to be construed as limiting the present invention.

As shown in fig. 1 to 3, the present embodiment provides a switching power supply for a stepping motor driver, including a self-excited starting circuit including an input voltage, a rectifying and smoothing circuit, a first power switching circuit, and a high frequency transformer, and an excitation control circuit including a PWM chip, a second power switching circuit, and an excitation transformer, a secondary rectifying current, and a smoothing and smoothing circuit;

the input voltage is used for outputting 220V alternating voltage;

the input voltage is connected with a rectifying and filtering circuit, after 220V alternating current voltage is input, the alternating current voltage passes through the rectifying and filtering circuit, the rectifying and filtering circuit is used for converting the alternating current voltage into 310V pulsating direct current voltage, and the 310V direct current voltage enters a main winding of the high-frequency transformer through a C3 capacitor.

Common mode clutter and differential mode clutter in the circuit are eliminated, and a switching power supply is protected;

the rectifying and filtering part comprises a rectifying bridge and main filtering capacitors C1 and C2 and converts 220V alternating current voltage into 310V pulsating direct current voltage; the 310V dc voltage enters the primary winding of the high frequency transformer through the C3 capacitor.

The rectification filter circuit is connected with a first power switch circuit, the first power switch circuit comprises a first switch triode Q1 and a second switch triode Q2, and the high-frequency transformer comprises a main winding and a feedback winding;

the collectors of the first switching triode Q1 and the second switching triode Q2 are connected to a main winding of the high-frequency transformer, the first switching triode Q1 and the second switching triode Q2 generate self-excitation after being electrified, and are alternately switched on and off, so that the high-frequency transformer generates mutual electromotive force, and a feedback winding of the high-frequency transformer generates mutual inductance to respectively supply power to the excitation transformer and the PWM chip;

the PWM chip is connected with the exciting transformer and outputs PWM signals, the second power switch circuit comprises a third switching triode Q3 and a fourth switching triode Q4 and drives the third switching triode Q3 and the fourth switching triode Q4 to be switched on and off, high-pulse electromotive force is generated in a winding of the exciting transformer, the frequency of the exciting transformer is controlled, the variation of the electromotive force of the winding in the exciting transformer is controlled, then the first switching triode Q1 and the second switching triode Q2 which are started in a self-excitation mode are controlled, the self-excitation starting circuit is converted into a self-excitation control circuit, and the first switching triode Q1 and the second switching triode Q2 in the self-excitation circuit are controlled to be switched on and off alternately.

The high-frequency transformer generates a required voltage signal to provide continuous working voltage for the PWM chip, the PWM chip stably provides the PWM signal, and the driving transformer is driven to control the first switching triode Q1 and the second switching triode Q2 by controlling the third switching triode Q3 and the fourth switching triode Q4, so that the main windings of the high-frequency transformer mutually feel the main output winding to generate an oscillating circuit.

The main output winding generates high-frequency electromotive force after mutual inductance, so that the charge with a load can be achieved in the main winding of the high-frequency transformer, and the high-frequency transformer and the load are connected in parallel to form a capacitor with larger capacity after passing through a secondary rectification current and a smoothing filter circuit.

Due to the charging and discharging functions of the capacitor and the voltage at two ends of the capacitor, the pulsation degree of the output voltage of the rectifying circuit is greatly weakened, the stable 24V voltage is smoothly output, the 24V direct current voltage is input into a driver of the stepping motor, and the AB two-phase power supply is supplied to the stepping motor through an H-bridge circuit in the driving circuit.

The rectifying and filtering circuit comprises an inductor, a plurality of capacitors and a rectifying bridge, wherein the rectifying bridge consists of four rectifying diodes, including D1, D2, D3 and D4.

The rear part of the rectifier bridge comprises two main filter capacitors C1 and C2, and a series of resistors, capacitors and diodes are connected to the first switching triode Q1 and the second switching triode Q2 and are used for dividing voltage, biasing, accelerating conduction and the like.

In this embodiment, after the power is turned on, the first switching transistor Q1 and the second switching transistor Q2 generate self-excitation, and the process of alternately turning on and off includes:

in the initial stage of energization, the first switching triode Q1 is in a cut-off state, the voltage input end accesses the mains supply 220V, the alternating current 220V is converted into a pulse direct current voltage of 310V through the rectifying and filtering circuit, and the main filtering capacitors C1 and C2 are charged.

One path of pulsating direct current positive voltage boosted to 310V passes through a collector electrode of a first switching triode Q1, the other path of pulsating direct current positive voltage passes through the partial pressure of a resistor, passes through a bias resistor R3, is added to a base electrode of a triode Q1, a starting voltage is provided for a first switching triode Q1, and a switching triode Q1 is conducted.

The excitation transformer T2 includes a plurality of primary windings and a plurality of secondary windings, the second secondary winding L2 is a primary winding of the excitation transformer T2, the first secondary winding L1 and the third secondary winding L3 are secondary windings of the excitation transformer, the first secondary winding L1 is connected to the base of the first switching transistor Q1, and the third secondary winding L3 is connected to the base of the second switching transistor Q2;

two pins 10 and 6 of the excitation transformer T2 are the first secondary winding L1, a pin 8 is the second winding L2, and pins 7 and 9 are the third secondary winding L3.

After the base of the first switching triode Q1 obtains voltage, the collector and the emitter of the first switching triode Q1 are conducted, the voltage begins to drop, current flows out from the emitter after the first switching triode Q2 is conducted, the current can flow downwards to the second secondary winding L2 due to the fact that the second switching triode Q2 is in the cut-off state at the moment, and the current continues to flow downwards.

After the base of the first switching triode Q1 obtains voltage, the collector and the emitter of the first switching triode Q1 are conducted, the voltage begins to drop, the high-frequency transformer T1 comprises a primary side and a secondary side, and the secondary side power of the high-frequency transformer is obtained by energy conservation according to the power provided by the primary side.

The power provided by the primary side of the high-frequency transformer T1 in unit time is directly proportional to the sum of the square of Ton and the frequency, is directly proportional to the square of the input primary side direct current voltage, and is inversely proportional to the number of turns of the primary side winding.

If the primary flux of the high frequency transformer is reset during the time toff and the secondary flux of the high frequency transformer is reset during the time ton of the high frequency transformer T1, the flux in the transformer core will gradually increase if the flux does not return to the beginning of the cycle at the end of the switching cycle, causing the core to saturate and damaging the power switching tube. To satisfy the flux reset condition of the single-ended converter, Ton and Toff should be appropriate and not too long, otherwise the frequency of the switching tube is low and is related to the number of turns of the primary winding and the secondary winding of the high-frequency transformer.

The high-frequency transformer T1 includes a fourth secondary winding L4, which passes through the fourth secondary winding L4, and at this time, the fourth secondary winding L4 generates a self-inductance that hinders the current from increasing, and the current continues to go downward to charge the capacitor C5, and a circuit cycle is completed with the charging of the capacitor C5.

In different output powers, the influence of Ton on the output power is the largest only by changing the power of the primary side of the high-frequency transformer, but the Ton is not suitable to be changed greatly due to the limitation of the magnetic flux reset condition, only the parameters of the filter inductor, the filter capacitor and the like of the front circuit can be changed by changing the direct-current voltage of the primary side, and the frequency is limited by the self condition of the power switch tube.

The self-inductance direction generated by the second secondary winding L2 is left positive and right negative, mutual inductance is generated between the first secondary winding L1 and the third secondary winding L3, the same-name ends are consistent, the generated mutual inductance directions are the same, and the mutual inductance direction of the first secondary winding L1 of the excitation transformer is left positive and right negative.

The positive electrode of the first secondary winding L1 is connected to the base of the switching transistor Q1 through a diode D1 and a resistor R3, so that the base voltage of the switching transistor Q1 is raised, the conduction amount of the collector and the emitter is increased, the conduction amount is gradually increased, and finally, the saturation state is reached, and the current flowing in the period is also increased.

The third secondary winding L3 also generates a left-right positive-negative mutual inductance, the negative electrode of the third secondary winding L3 is connected to the base of the second switching transistor Q2, the base of the second switching transistor Q2 is a negative voltage, and at this time, the collector and emitter of the second switching transistor Q2 cannot be conducted.

At this time, the switching transistors Q1 and Q2 are in a conducting state under the action of the exciting transformer winding, and the first switching transistor Q1 is in a cut-off state, and the second switching transistor Q2 is in a conducting state.

After the capacitor C5 is charged, the voltage gradually increases, and the fourth secondary winding L4 prevents the current from decreasing as the current decreases, so that the direction of the mutual inductance varies, and a mutual electromotive force of positive and negative polarities is generated inside the high-frequency transformer to suppress the current from decreasing.

The second secondary winding L2 of the excitation transformer T2 also generates a positive right, left, and negative self-induced electromotive force that suppresses the current reduction, the third secondary winding L3 of the excitation transformer T2 generates a positive right, left, and negative mutual-induced electromotive force, and the first secondary winding L1 also generates a positive right, left, and negative mutual-induced electromotive force.

The positive pole of the third secondary winding L3 is connected to the base of the second switching transistor Q2, the base of the second switching transistor Q2 will get a positive voltage, and the collector and emitter of the second switching transistor Q2 will be turned on after getting a positive voltage.

The first secondary winding L1 of the driver transformer T2, which is negative on the left, is connected up to the base of the first switching transistor Q1, where the base of the first switching transistor Q1 is negative and the collector and emitter are off. When the first switching transistor Q1 is turned off, the capacitor C5 changes from a charging state to a discharging state, and the current flows through the fourth secondary winding L4 of the high-frequency transformer T1 through the main loop, and flows through the second secondary winding L2 of the excitation transformer T2, and the current continues upward, and when the first switching transistor Q1 is turned off, the second switching transistor Q2 is turned on, and the current flows from the collector to the emitter of the second switching transistor Q2, and continues to flow to the cathode of the rectifier bridge, so that a cycle can be formed.

During the discharging process of the capacitor C5, the current flowing through the capacitor C5 gradually decreases due to the voltage drop, and when the current flows through the fourth secondary winding L4, the fourth secondary winding L4 generates an electromotive force for suppressing the current reduction, so that the first secondary winding L2 is excited to generate a left positive and right negative self-induced electromotive force for preventing the current reduction.

The third secondary winding L3 and the first secondary winding L1 also generate the same mutual electromotive force with positive left and negative right, so that the first secondary winding L1 drives the first switching triode Q1 to be turned on, and the third secondary winding L3 drives the second switching triode Q2 to be turned off, thus alternately generating a self-excitation starting process.

The said operation process is self-excited starting process, and the general semi-bridge self-excited switch power supply has only one exciting transformer, its self-excited feedback winding is on the main transformer, and its pulse duty ratio control signal is coupled to the primary side by means of the secondary side of the exciting transformer, so that the self-excited switch transformer is non-voltage-stabilizing.

The invention improves the traditional self-excitation part, the unbalanced volt-second value is directly proportional to the direct current bias voltage is filtered out when the primary coil of the transformer is excited to be connected with the capacitor C17 in series, the voltage volt-second value of the voltage is balanced during the conduction period of the triode to eliminate the bias magnetism, the iron core of the transformer is prevented from being saturated and generating overlarge collector current of the transistor, the efficiency of the transformer is reduced, and the triode is out of control and even burnt.

The invention adopts a half-bridge circuit, when a first switching triode Q1 is switched on and a second switching triode Q2 is switched off, the voltage applied to two ends of an excitation transformer is half of the bus voltage, and simultaneously, energy is transferred from a primary side to a secondary side. When the first switching transistor Q1 is turned off and the second switching transistor Q2 is turned off, the two windings on the secondary side of the excitation transformer are in a short-circuit state due to the simultaneous freewheeling of the two tubes of the rectifier diode, and the primary winding is also in a short-circuit state.

When the first switching transistor Q1 is turned off and the second switching transistor Q2 is turned on, the voltage applied across the excitation transformer is also substantially half the bus voltage, and energy is transferred from the primary side to the secondary side. And the secondary side two diodes complete commutation.

Aiming at the problems that a chip is burnt off and the like caused by serious burr, low voltage and serious heating of a power tube due to the rise of the voltage of the high-voltage side of a common switching power supply, the power tube which runs under a half-bridge inductive load circuit and is in a turn-off state bears the rapid rise of the voltage due to the recovery process of an anti-parallel diode of the power tube.

The static dv/dt is typically higher than the rate of rise when the power tube is off. Due to the miller effect, this dv/dt generates a current in the collector, capacitor, which flows to the driver circuit. When the bridge is in an off state, the voltage Vg is zero, and the current increases the voltage due to the impedance of the circuit, so that the voltage reaches the threshold voltage in severe cases, and the bridge arm is short-circuited.

The loss of the driver is mainly concentrated on the loss when the switch tube is switched on, switched off and switched on: the losses of the freewheel circuit and the losses of the working auxiliary power supply. Under high-frequency and high-current working conditions, the power consumption of the switching triode is larger. The follow current diode absorbs the overvoltage when the driving tube is turned off and feeds back the overvoltage to the power supply, so that the power supply efficiency is obviously improved, the dropping speed of the current winding of the stepping motor is accelerated, and the output torque of the stepping motor is improved.

The reverse withstand voltage of the Schottky diode is low, reverse leakage current is large, loss of the rectifier tube is increased, and after part of the Schottky diode is reserved, the other diodes are fast recovery diodes.

The first switching triode Q1 and the second switching triode Q2 adopt a capacitor C5 and a capacitor C6 to isolate and filter the power except for adding a voltage stabilizing tube to the base electrode.

During the time that the first switching transistor Q1 and the second switching transistor Q2 are conducting, the freewheeling diode D8 is turned off due to reverse bias. Although the dc voltage is applied, the current in the inductor L rises linearly and is stored as magnetic energy. When the switch tube T is turned on, the current in the energy storage inductor L rises to the maximum value.

When the first switching transistor Q1 and the second switching transistor Q2 are turned off and just turned off, since the current in the energy storage inductor L cannot change suddenly, self-induced electromotive force with the polarity opposite to that of the original voltage is generated at the two ends of the L. The freewheeling diode D starts to conduct in the forward direction, and the magnetic energy stored in the energy storage inductor L starts to be released through the freewheeling diode and the load resistor in the form of electric energy. When the switching transistor Q1, Q2 is turned off and ends, the current in the energy storage inductor L drops to a minimum value.

In the separately excited oscillation circuit part, the fourth winding L4 of the high-frequency transformer T1 self-induces during the self-excitation of the first switching transistor Q1 and the second switching transistor Q2, so that the secondary winding generates an induced voltage, the two secondary windings of the high-frequency transformer, and a middle tap between two pins 6 and 7 of the two secondary windings, and the induced voltage is output through two pins 6 and 7 of the secondary winding.

The outputs of the pins 6 and 7 of the secondary winding are the same, the pin 7 passes through a rectifier diode D5 downwards, the pin 6 also passes through a rectifier diode D6 downwards, the connection is carried out between the pin and the diode, and finally the pin is connected to the pin 12 of the power supply pin of the PWM chip.

When the circuit is started by self-excitation, a reference voltage 5V is generated at a pin 14 of a reference voltage input end of a PWM chip, the rectified electric energy is transmitted to a pin of a third main winding of an excitation transformer T2, the lower path of the electric energy is transmitted to a pin 12 of a power supply pin of the PWM chip, after the PWM chip is electrified, the chip outputs stable PWM square waves, the chip is in a push-pull mode, pins 8 and 11 of the PWM chip interactively output control signals, when the pins 8 output, the pins 11 do not output, the pins 8 of the chip are connected to a base electrode of a switching triode Q3, and the pins 11 are connected to a base electrode of a switching triode Q4 of the excitation transformer.

The primary winding comprises a first winding, a second winding and a third winding, the first winding and the second winding of the exciting transformer T2 are conducted and grounded through a collector and an emitter of a third switching triode Q3 controlled by the first winding and the second winding, when a control signal is output by a pin 11 of the chip, voltage conduction is obtained at a base of a fourth switching triode Q4, and the second winding and the third winding of the exciting transformer T2 are conducted through a control switching triode Q4 and flow to the ground.

The PWM chip controls the mutual conduction of two main windings of an exciting transformer T2, and the secondary winding above generates alternating current due to mutual inductance, so that the mutual conduction of two switching triodes Q1 and Q2 is further controlled, the power switches Q1 and Q2 output square waves with the same frequency as the chip, and the main winding of the high-frequency transformer T1 can be charged with load and has induced voltage output to provide output voltage for a following circuit.

The method comprises the steps of controlling, using a power switch transformer to provide base reverse driving voltage to shorten storage of a power switch tube, using RC circuit to delay conduction to avoid double-tube common-state conduction, shortening storage time of turning off the power switch tube, and using delay conduction pulse to avoid double-tube common-state conduction.

The switching triodes Q1 and Q2 alternately work, the output power of the switching triodes is equivalent to the output power of two switching power supplies, the output power of the switching triodes is about twice of the output power of a single switching power supply, after the switching triodes are rectified by a rectifier bridge, the voltage ripple coefficient Sv and the current ripple coefficient Si of output voltage are small, and only small filter inductors and capacitors are needed.

The switching transistors Q1 and Q2 work alternately, which is equivalent to the output power of two switching power supplies, and the output power is about that two control switches are in an on state at the same time. When the switching transistors Q1, Q2 start to conduct, it is equivalent to charging the capacitor, and it needs a transition process from the off state to the complete conducting state; when the switching transistors Q1 and Q2 are switched from the on state to the off state, a transition process is also required from the on state to the completely off state, which is equivalent to discharging the capacitor.

When the two switching devices are in the on and off transition processes respectively, namely when the two switching devices are in the semi-conducting state when in the semi-conducting state, the two control switches are equivalently switched on simultaneously, and the two control switches can cause short circuit to the power supply voltage; in this case, a large current will be present in the series circuit of the two control switches, and this current does not pass through the transformer load.

During the transient period when the two control switches Q1 and Q2 are simultaneously in process, the two switches will generate large power loss. In order to reduce the loss generated in the transition process of the control switches, in a half-bridge type switching power supply circuit, the turn-on and turn-off time of the two control switches is staggered for a short time.

Because the stepping motor can generate large inductive load in normal work and can generate instant high voltage for a power supply end. The switching power supply of the stepper motor driver must therefore be greater than the maximum amperage of the driver.

Although the working current of the motor is not large, the current can be increased by 3-4 times at the moment of reversing or starting the stepping motor. If the load of the motor is too large, the current at this time is larger.

When the power supply capacity of the switching power supply is insufficient, the stepping motor is embodied in a serious step loss (the stepping motor does not reach a position which should be reached according to an instruction), and even overcurrent protection of the power supply can be caused, so that no output is generated in driving or the heating is serious.

By the invention, under the condition of using the same power switch tube, the power which is twice as high as the original output power can be obtained. The voltage applied to the power switch tube in the half-bridge converter circuit is lower and not higher than the value of the input direct current power supply voltage.

In the low-speed operation process of the stepping motor, because the interval time of the magnetic pulse of the motor is long, the motor is represented as single-step operation, the rotor starts to move under the action of electromagnetic force, when the balance point is reached, the electromagnetic torque drives the torque to be zero, but the rotating speed of the rotor is overlarge, and due to inertia, the rotor rushes over the balance point, at the moment, the motor generates negative torque, and under the action of the negative torque, the rotating speed of the rotor is gradually zero and starts to rotate reversely, so that the rotor oscillates around the balance point.

The switch power supply adopts a self-excited starting circuit which excites an oscillation circuit, thereby overcoming the problem of poor stability of high-speed operation of the motor.

The switching power supply has large capacity and good surge impact capability, and is suitable for being driven by a stepping motor. Therefore, the stepping motor can fully exert the characteristics thereof under the conditions of high input voltage and high output power.

It is understood that in other embodiments, the model of the PWM chip may be set by those skilled in the art according to specific operating conditions, for example, TL494 may be adopted, and will not be described in detail herein.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A switching power supply for a stepper motor driver, comprising: the self-excitation starting circuit comprises a first power switch circuit and a high-frequency transformer, and the self-excitation control circuit comprises a PWM chip, a second power switch circuit and an exciting transformer;

the first power switch circuit is connected with the high-frequency transformer, and after the first power switch circuit is electrified, the first power switch circuit generates self-excitation to enable the high-frequency transformer to generate interactive electromotive force to respectively supply power to the exciting transformer and the PWM chip;

the PWM chip is connected with the exciting transformer, outputs PWM signals, excites the change of electromotive force of a winding in the transformer by controlling the second power switch circuit, and then controls and starts the first power switch circuit, so that the high-frequency transformer generates high-frequency electromotive force to supply power for the driver of the stepping motor.

2. The switching power supply for a stepping motor driver as claimed in claim 1, wherein said first power switching circuit comprises a first switching tube and a second switching tube, said high frequency transformer comprises a main winding and a feedback winding, and collectors of said first switching tube and said second switching tube are connected to said main winding, and when said high frequency transformer is energized, said first switching tube and said second switching tube are self-excited, alternately turned on and off, and said feedback winding is mutually induced to supply power to said exciting transformer and said PWM chip, respectively.

3. The switching power supply for a stepping motor driver as claimed in claim 1, wherein said exciting transformer comprises a plurality of primary windings and a plurality of secondary windings, a first secondary winding is connected to a base of a first switching transistor, a second secondary winding is connected to a base of a second switching transistor, a collector and an emitter of the first switching transistor are turned on after a voltage is obtained at the base of the first switching transistor, the voltage starts to drop, a current flows from the emitter after the turn-on, and the second switching transistor is in a cut-off state at which the current flows to the primary winding.

4. The switching power supply for a stepper motor driver as defined in claim 1, wherein the second power switching circuit comprises a third switching transistor and a fourth switching transistor, the PWM chip comprising a plurality of pins, a first pin connected to a base of the third switching transistor and a second pin connected to a base of the fourth switching transistor.

5. The switching power supply for a stepping motor driver as claimed in claim 2, wherein the main winding generates self-inductance during self-excitation of the first switching transistor and the second switching transistor, the feedback winding generates induced voltage, a center tap is provided in a center of the feedback winding, and the induced voltage is outputted through a pin of the feedback winding.

6. The switching power supply for a stepping motor driver as claimed in claim 2, wherein said PWM chip is connected to the primary winding to control the mutual conduction of the primary winding, and the secondary winding generates an alternating current due to mutual inductance to control the mutual conduction of the first switching transistor and the second switching transistor, so that the first switching transistor and the second switching transistor output a square wave having the same frequency as the PWM chip, and the main winding of the high frequency transformer receives a loaded charge to output an induced voltage.

7. The switching power supply for a stepping motor driver as claimed in claim 4, wherein when the first switching transistor is turned on and the second switching transistor is turned off, the voltage applied across the excitation transformer is half of the bus voltage while energy is transferred from the primary winding to the secondary winding, and when the first switching transistor and the second switching transistor are simultaneously turned off, the secondary winding of the excitation transformer is in a short-circuit state.

8. The switching power supply for a stepping motor driver as claimed in claim 6, wherein said primary winding comprises a first winding, a second winding and a third winding, said first winding and said second winding are conducted through a collector and an emitter of a third switching transistor, while a base of a fourth switching transistor is conducted with voltage, and said second winding and said third winding are conducted through a fourth switching transistor.

9. The switching power supply for a stepping motor driver as claimed in claim 8, wherein the PWM chip outputs a PWM signal to drive the excitation transformer to control the first switching transistor and the second switching transistor by controlling the third switching transistor and the fourth switching transistor, so that the main winding of the high frequency transformer is mutually output to the main winding to generate the oscillator circuit.

10. The switching power supply for a stepping motor driver as claimed in claim 1, wherein said switching power supply excites a capacitor in series with a primary winding of a driving transformer in a control circuit.