JPH083200Y2 - Stepping motor drive circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Self-starting characteristics, resonance characteristics, torque characteristics, reliability against damage to an exciting transistor, and the like are listed as the performance of a stepping motor drive circuit. The characteristics of the stepping motor vary greatly depending on the performance of the stepping motor drive circuit.The present invention not only suppresses the heat generation of the stepping motor in the constant current drive method, but also stabilizes the DV clamp circuit and controls the constant current. More specifically, the present invention relates to a stepping motor drive circuit devised to improve the self-starting characteristic and the torque characteristic without impairing the resonance characteristic. More specifically, the DC power source (E ₁ ) and the semiconductor chopper are described. (Q ₁ ), pulse width modulation switching circuit (PWM), and reactor (L
₁ ), smoothing capacitor (C ₁ ), drive winding switching circuit (DQ), sense resistor (R ₅ ) and error amplifier (AM
And P _2), resistors for DV voltage divider connected in series (R _6, R ₇₎
And a comparator (AMP ₁ ) and a comparator stabilizing capacitor (C ₂ ), the semiconductor chopper (Q ₁ ) is connected to the output side of the DC power supply (E ₁ ) It is for controlling the output of the power supply (E _1), the pulse width modulation switching circuit (PWM), the connected to the base of the semiconductor chopper (Q ₁₎ is for controlling the semiconductor chopper (Q _1), a smoothing capacitor (C ₁₎ is connected in parallel to the drive winding switching circuit (DQ), an output of the semiconductor chopper (Q ₁₎ with a series-connected reactor in the output side of the semiconductor chopper (Q ₁₎ (L ₁₎ It is a small capacitance that smooths to a certain extent, and the sense resistor (R ₅ ) is connected in series to the output side of the drive winding switching circuit (DQ) that controls the switching of the drive winding, and passes through the drive winding. The total current amount is detected by the voltage change. The error amplifier (AMP ₂ ) is connected to the input side of the pulse width modulation switching circuit (PWM), and the voltage change of the sense resistor (R ₅ ) and the total Controls the pulse width modulation switching circuit (PWM) by comparing the voltage that is the reference for power control and inputting the output signal to the pulse width modulation switching circuit (DQ) to control the total current flowing in the drive winding. And the resistors for dividing the DV voltage (R ₆ , R ₇ ) are the reactor (L ₁ )
It is connected in series between the output of and the power supply ground (E ₁ GND). The connection point of both resistors (R ₆ , R ₇ ) for dividing the DV voltage and the non-inverting input terminal of the comparator (AMP ₁ ) ( +) Is connected to reduce the ratio of the fluctuation of DV voltage and input it to the comparator (AMP ₁ ).
P ₁ ) is connected in parallel to the error amplifier (AMP ₂ ) and to the input side of the pulse width modulation switching circuit (DQ), and the non-inverting input terminal (+) of the comparator (AMP ₁ ) and the power supply ground (E ₁ The amount of fluctuation that is a reduced ratio to the fluctuation of the DV voltage detected by the division resistance (R ₇ ) connected to (GND) and the reference voltage for clamping the drive voltage to a specified voltage value. Is compared and is output to the pulse width modulation switching circuit (DQ), which controls the pulse width modulation switching circuit (DQ) to clamp the drive voltage at a specified voltage value. The conversion capacitor (C ₂ ) is connected in parallel to the power ground side dividing resistor (R ₇ ) connected between the non-inverting input terminal (+) of the comparator and the power ground (E ₁ GND), Both connected in series And characterized in that is adapted to control the comparator (AMP ₁₎ to Statistical Tech by smoothing the ripple of the dividing resistor having a reduced ratio (R ₇₎ by dividing resistor (R _6, R ₇₎ The present invention relates to a stepping motor drive circuit that operates.

Hereinafter, a detailed description will be given by comparing an example of the present invention with an example of the present invention with reference to the accompanying drawings.

The first figure denotes a typical example of a conventional circuit, this circuit includes a DC power supply (E _1), the semiconductor chopper (Q ₁₎ for chopper control the output of the DC power supply (E _1), the semiconductor chopper ( Pulse width modulation circuit (PWM) that controls Q ₁ ) by pulse width modulation switching action, flywheel diode (D ₁ ) that supplies current to reactor (L ₁ ) when semiconductor chopper (Q ₁ ) is cut off , a reactor which is inserted in series with the output side of the semiconductor chopper _{(Q 1) (L 1)} ,
It is composed of a smoothing capacitor (C ₁ ) connected between the output of the reactor (L ₁ ) and the input of the sense resistor (R ₅ ). DC power supply (E ₁ ) is shown by battery symbol,
Generally, a DC power supply obtained by full-wave rectifying an AC power supply is used. (DQ) is a driving winding switching circuit, the exciting transistor (Q ₂ ~Q ₅₎ The parallel output of the sense resistor having a low value (R ₅₎ a driving winding switching circuit (DQ) as a switching element It is connected to the side. (M) is a stepping motor, which has drive windings (DL _{1 to} DL ₄ ) and a rotor (not shown). The drive windings (DL _{1 to} DL ₄ ) are connected in series with the transistors (Q _{2 to} Q ₅ ), respectively. (AM
P ₁ ) is a comparator and (AMP ₂ ) is an error amplifier, which are connected in parallel and connected to the input of the pulse width modulation circuit (PWM). The resistor (R ₁ ) for dividing E ₂ voltage and the resistor (R ₂ ) are connected in series, and the connection point is connected to the inverting input terminal of the error amplifier (AMP ₂ ) to set the reference voltage. The other end of the resistor (R ₁ ) is connected to the reference voltage (E ₂ ). The dividing resistor (R ₃ ) and the resistor (R ₄ ) are also connected in series. The connection point of the resistor (R ₃ ) and the resistor (R ₄ ) is connected to the non-inverting input terminal of the error amplifier (AMP ₂ ). The other end of the resistor (R ₃ ) is also connected to the reference voltage (E ₂ ), and the other end of the resistor (R ₄ ) is connected to the output side of the drive circuit (DQ). A resistor (R ₆ ) for dividing the DV voltage and a resistor (R ₇ ) are also connected in series. The connection point between the resistor (R ₆ ) and the resistor (R ₇ ) is a comparator (AMP ₁ ).
The other end of the resistor (R ₆ ) is connected to the output side of the reactor (L ₁ ) and the other end of the resistor (R ₇ ) is connected to the power supply ground (E ₁ GND).

In the above configuration, the stepping motor (M) is driven by the output of the constant current power supply, and corresponds to the opening and closing of each exciting transistor (Q _{2 to} Q ₅ ) of the drive winding switching circuit (DQ) controlled to open and close by the distribution circuit. The stepping motor is rotated by a predetermined angle to perform a predetermined step drive. During this period, the stepping motor (M) normally accelerates from a low speed to a high speed, on the contrary, it decelerates at the falling time and rises after the rising. The so-called trapezoidal operation, in which high-speed steady operation is performed until just before the descent, is designed to move from the starting point to the stop position in the shortest time. The exciting current flowing through the drive winding (ML) of the stepping motor (M) up to the high speed region is sensed by the sense resistor (R ₅ ),
The constant current is controlled so as to always flow. In the constant speed region, the coil impedance of the stepping motor (M) is low, so the drive current voltage (DV) is lowered. In the high speed region, on the contrary, the coil impedance becomes extremely high, and therefore the drive current voltage (DV). Is increased to keep the drive current value flowing through the stepping motor (M) constant. In the conventional circuit shown in FIG. 1, the smoothing capacitor (C ₁ ′) has a large capacity in order to prevent resonance and ensure the stability of the DV clamp, but it has the following drawbacks. That is, the large-capacity smoothing capacitor (C ₁ ′) slows the rising of the exciting current of the stepping motor (M), delays the establishment of the magnetic flux inside the stepping motor (M), and deteriorates the self-starting characteristic.

The large-capacity smoothing capacitor (C ₁ ′) needs to discharge the electric charge that has been charged to the load fluctuation of the stepping motor (M), and the semiconductor chopper (Q ₁ ) is turned off by the control of the pulse width modulation circuit (PWM). Even then, the capacity of the smoothing capacitor (C ₁ ′) flows into the stepping motor (M), which causes a delay in loop speed.

When the stepping motor (M) is suddenly stopped while being driven at high speed, the coil impedance of the stepping motor (M) becomes high at high speed rotation, and the drive voltage (DV) inevitably rises. However, if it suddenly stops, the coil impedance will suddenly drop, and the charge stored in the large-capacity smoothing capacitor (C ₁ ′) will be released instantly, so this must be consumed by the excitation transistor (Q _{2 to} Q ₅ ). You will not get it. As a result, drive voltage (DV) = V
And the emission current = I, the exciting transistor (Q _{2 to} Q ₅ )
There is a risk of exceeding the ASO (safe operating area) of
The excitation transistors (Q _{2 to} Q ₅ ) were damaged, resulting in poor reliability against damage.

Therefore, rather than taking measures against heat generation of the stepping motor (M), the drive voltage (DV) is limited at a low place and derated in order to improve reliability against damage to the excitation transistors (Q _{2 to} Q ₅ ). However, this naturally caused a decrease in torque in the high speed range.

If a smoothing capacitor (C ₁ ′) with a small capacity is used instead of a large capacity, the ripple of the drive voltage (DV) becomes large and the comparator (AMP ₁ ) Operates at the ripple level,
The on-pulse width of the semiconductor chopper (Q ₁ ) fluctuates, the drive voltage (DV) becomes unstable, and in terms of torque characteristics, a resonance phenomenon occurs near this. Therefore, if the smoothing capacitor (C ₁ ′) has a large capacity, the resonance can be alleviated although the above-mentioned problems ( ₁ ) to ( ₃ ) occur.

As described above, increasing the capacity of the smoothing capacitor (C ₁ ′) is effective as a measure against resonance to some extent, but has the drawbacks that self-starting characteristics, reliability of damage to the exciting transistor, and adverse effects on high-speed torque are large. .

The present invention has been made in view of the drawbacks of the conventional example,
Its purpose is to increase the loop speed by not holding an excessive capacitor capacity in the constant current control feedback loop, and to stabilize the drive voltage clamp for suppressing heat generation of the stepping motor. Therefore, it is possible to provide a countermeasure against resonance, and to provide a stepping motor drive circuit with improved self-starting characteristics, reliability against damage to the excitation transistor, and high-speed torque. FIG. 2 solves the above problems. 1 is an embodiment of the present invention. The same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. The drive winding switching circuit (DQ) is not limited to the illustrated embodiment, and an appropriate circuit may be selected according to the type of the stepping motor (M).

In the first embodiment of the present invention, as shown in FIG. 2, a comparator stabilizing capacitor (C ₂ ) is connected in parallel with a dividing resistor (R ₇ ). Then, although the stepping motor (M) is step-driven by the output of the constant current power source, each exciting winding (DL _{1 to} DL ₄ ) is formed by the exciting transistors (Q _{2 to} Q ₅ ) controlled to be opened and closed by the distribution circuit. ) Is excited, and this exciting current is sensed by the sense resistor (R ₅ ). The sense voltage sensed by the sense resistor (R ₅ ) is In raising the voltage level of the non-inverting input terminal of the error amplifier (AMP ₂₎ shown, the error amplifier (AMP ₂₎ is The output is amplified so that it becomes the same as the reference voltage level indicated by. (Note that (E ₂ ) in the previous equation is given by the equation described later.) The output of the error amplifier (AMP ₂ ) turns on the semiconductor chopper (Q ₁ ) for the required pulse width by the pulse width modulation circuit (PWM). Let The pulse turned on by the semiconductor chopper (Q ₁ ) is smoothed by the reactor (L ₁ ) and the smoothing capacitor (C ₁ ) and supplies necessary power to the stepping motor (M). Here, in order to increase the rotation speed of the stepping motor (M), if the frequency for exciting each phase of the exciting transistors (Q _{2 to} Q ₅ ) is increased, the coil impedance of the stepping motor (M) also increases and the exciting current flows. The driving voltage (DV) smoothed by the reactor (L ₁ ) and the smoothing capacitor (C ₁ ) rises to maintain the voltage level of the sense resistor (R ₅ ). How the driving voltage (DV) can be increased changes the flow of the exciting current, which greatly affects the torque characteristics in the high-speed range. On the contrary, the heat generated by the stepping motor (M) itself also increases, so the driving voltage (DV) level Must be controlled with an appropriate value. Therefore, the comparator (AMP ₁ ) limits the pulse width modulation circuit (PWM) when the drive voltage (DV) × R ₇ ÷ (R ₆ + R ₇ ) = E ₂ , DV clamp is performed to suppress heat generation of the stepping motor (M).

Next, the function of the comparator stabilizing capacitor (C ₂ ) will be described in detail.

The problem when the smoothing capacitor (C ₁ ) has a large capacity is as described above, but in this circuit, the comparator stabilization capacitor (C ₂ ) provides a function equivalent to that of the conventional large-capacity capacitor (C ₁ ). It is characterized by having
This has made it possible to reduce the capacity of the smoothing capacitor (C ₁ ) and solve the conventional problems.

First, when the smoothing capacitor (C ₁ ) has a small capacity, the ripple of the drive voltage (DV) becomes large, and the comparator (AMP ₁ ) operates at the ripple level near the drive voltage (DV) is clamped. Since the on-pulse width of the chopper (Q ₁ ) fluctuates, the drive voltage (DV) becomes unstable,
As described above, in terms of torque characteristics, a resonance phenomenon occurs near this point. Therefore the comparator stabilizing capacitor (C _2), smoothes the ripple having a reduced ratio in resistance for DV voltage divider (R ₆₎ and a resistor (R _7), to control the comparator (AMP ₁₎ in a static manner. As a result, stable comparator operation can be secured even near the DV clamp, resonance is improved, and the function is equivalent to that of the conventional large-capacity smoothing capacitor (C ₁ ). Therefore, by using the comparator stabilizing capacitor (C ₂ ), the smoothing capacitor (C ₁ ) of the present invention has a smaller capacity than the conventional smoothing capacitor (C ₁ ′). C ₂ ) also has a low withstand voltage and a small capacity, so compared to conventional products, it has overall advantages in terms of cost and space factor. Further, since the comparator stabilizing capacitor (C ₂ ) is a capacitance that does not participate in the control loop in the constant current control before being DV clamped, it does not affect the loop speed which has been a problem in the past. Further, as described above, since the smoothing capacitor (C ₁ ) has a small capacity, the control can follow the impedance change of the stepping motor (M) quickly, so that the establishment of the magnetic flux is accelerated and the self-starting characteristic is improved. In addition, the comparator stabilizing capacitor (C ₂ ) does not participate in constant current control, the smoothing capacitor (C ₁ ) has a small capacity, and the smoothing capacitor (C ₁ ) can store a small amount of charge, resulting in high speed. without exceeding the ASO of even a sudden stop from rotating excitation transistor (Q ₂ ~Q _5), increases reliability of breakage of the excitation transistor due to the delay of the loop speed.

Further, as a result, it is possible to limit the value to a value higher than the conventional DV clamp value, which leads to an improvement in high-speed torque.

FIG. 3 shows another embodiment of the present invention, which is a comparator (AM
At the non-inverting input terminal (+) of P ₁ ), connect a comparator stabilizing capacitor (C ₂ ) between the non-inverting input terminal (+) and the power supply ground (E ₁ GND), and This is an example of connecting a resistor (R ₈ ) between the connection point of C ₂ ) and the dividing resistors (R ₆ , R ₇ ).

As described above, in the present invention, since the comparator stabilizing capacitor is connected in parallel to the resistor for dividing the DV voltage, the role of the conventional large-capacity smoothing capacitor can be supplemented, and the smoothing capacitor can be reduced in capacity. Moreover, the comparator stabilization capacitor can also have a low withstand voltage and a small capacity, improving the overall space factor and cost, and also improving the self-starting characteristics, torque characteristics, and reliability against damage to the excitation transistor. There is an advantage that it can be done.

[Brief description of drawings]

1 is a wiring diagram showing an example of a conventional constant current drive circuit for a stepping motor, FIG. 2 is a wiring diagram of an embodiment of the present invention, and FIG. 3 is a wiring diagram of another embodiment of the present invention. (E ₁ ) …… DC power supply, (Q ₁ ) …… Semiconductor chopper (PWM) …… Pulse modulation switching circuit (D ₁ ) …… Flywheel diode (L ₁ ) …… Reactor (DQ) …… Drive winding Switching circuit (R ₁ ) to (R ₄ ), (R ₆ ) to (R ₇ ) …… Division resistance (R ₅ ) …… Sense resistance, (R ₈ ) …… Resistance (M) …… Stepping motor (DL ₁ ) to (DL ₄ ) …… Drive winding (DV) …… Drive voltage, (C ₁ ) …… Smoothing capacitor (AMP ₁ ) …… Comparator (AMP ₂ ) …… Error amplifier (C ₂ )… … Comparator stabilizing capacitor.

Claims (1)

[Scope of utility model registration request] 1. A DC power supply, a semiconductor chopper, a pulse width modulation switching circuit, a reactor, a smoothing capacitor, a drive winding switching circuit, a sense resistor, an error amplifier, and a DV voltage divider connected in series. Is a stepping motor drive circuit consisting of a resistor, a comparator, and a comparator stabilizing capacitor.The semiconductor chopper is connected to the output side of the DC power supply and controls the output of the DC power supply. The circuit is connected to the base of the semiconductor chopper to control the semiconductor chopper, and the smoothing capacitor is connected in parallel to the drive winding switching circuit, and is connected to the output side of the semiconductor chopper in series with the reactor. It has a small capacity that smoothes the output to some extent. It is connected in series to the output side of the drive winding switching circuit that controls the winding switching, and detects the total amount of current passing through the drive winding by voltage change.The error amplifier is the input of the pulse width modulation switching circuit. The pulse width modulation switching circuit is controlled by comparing the voltage change of the sense resistor with the reference voltage of the total current control, and inputting the output signal to the pulse width modulation switching circuit. It controls the total current flowing in the drive winding, and the DV voltage division resistor is connected in series between the reactor output and the power supply ground, and the connection point of both DV voltage division resistors is connected. And the non-inverting input terminal of the comparator are connected, and the fluctuation of the DV voltage is reduced and input to the comparator. Connected in parallel with the input side of the pulse width modulation switching circuit, and reduced the ratio to the fluctuation of the DV voltage detected by the dividing resistor connected between the non-inverting input terminal of the comparator and the power supply ground. The fluctuation amount is compared with a reference voltage for clamping the drive voltage to a predetermined voltage value, and the signal is output to the pulse width modulation switching circuit, which controls the pulse width modulation switching circuit to drive the drive voltage. Is clamped at a predetermined voltage value, and the comparator stabilizing capacitor is connected in parallel to the power-ground-side dividing resistor connected between the non-inverting input terminal of the comparator and the power ground, and is connected in series. The comparator is implemented by smoothing the ripple component of the ground side dividing resistor whose ratio is reduced by the divided resistors. A stepping motor drive circuit characterized by being controlled by a system.