JP2688746B2 - PWM drive circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical field   The present invention relates to a PWM (pulse width modulation) drive circuit,
A pulse signal with a pulse width according to the signal level of the drive signal
And switch the load based on this pulse signal.
The present invention relates to a PWM drive circuit for driving a drive. Background art   PWM bidirectional as one method to drive loads such as motors
A switching drive system is known. The drive system
Has the advantage of low power loss and low power consumption
It has the following features, especially for vehicles that use a battery as a power source
For driving loads such as motors in equipment and portable equipment
It is for.   Conventionally, as a PWM drive circuit, as shown in FIG.
Generate two triangular wave signals a and b in phase with each other,
One of the square wave signals has a DC bias level
When the bell is high, enter the upper and lower limits of the comparison circuit 100.
Force, and by using the drive signal c as a comparison input,
The pulse width depends on the signal level of the drive signal and the load drive
Obtain a pair of pulse signals d and e corresponding to the moving direction, and
The load is switched and driven based on the pulse signals d and e of
There was one of the composition.   In such a configuration, the signal level of the drive signal c is small.
Range, the tip of the triangular wave signal should be used.
You. However, in the process of generating the triangular wave signal,
Does not have an infinite band, and a ring at the tip of the triangular wave
Avoid ringing or so-called blunting
Therefore, the tip of the triangular wave signal must be used.
In the conventional circuit tail which does not exist, especially the signal level of the drive signal c is
It is said that the linearity of input / output characteristics when it becomes small deteriorates.
There were drawbacks.   By the way, in the power drive stage that drives the load
Is a pair of transformers connected in series to the load.
Two sets of transistors are provided, and each set has different transistors.
Drive current in different directions depending on load when it is turned on by imming
By supplying the
Has become. Here, the transistor is generally shown in FIG.
As shown, t due to the capacitance Co between base and emitter_OFF
Has a delay time of
It has the characteristic that it cannot be turned off. This allows
In the power drive stage, when the driving direction is reversed,
Delay time t_OFFIf a reverse drive pulse occurs in
Transistors of different groups are temporarily turned on at the same time.
And a large current flows through the transistor,
The randista may be destroyed. Summary of the Invention   The present invention has been made in view of the above points, and the pulse
Use only the linear portion of the triangular wave signal to generate the signal
Due to the input / output especially when the signal level of the drive signal becomes small.
The linearity of force characteristics can be improved, and even power dry
PWM drive that can surely prevent simultaneous turning on of transistor
The purpose is to provide a dynamic circuit.   The PWM drive circuit according to the present invention has almost the same peak value.
Two-phase triangular wave signals with opposite phases are generated, and these two-layer three-wave signals are generated.
Input the upper and lower limits of the comparison circuit for the square wave signals respectively.
By setting the pulse signal according to the signal level of the drive signal.
Drive signal in a configuration that generates
The polarity with respect to the reference level is determined, and based on this determination result
Power drive only the drive pulse corresponding to the drive direction.
It is configured to supply to the stage. Example   Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
You.   In FIG. 1, the first constant current source 1 is a transistor.
Q₁, Q_TwoAnd resistance₁, R_TwoA current mirror circuit consisting of
Has been established. Connected in series with this first constant current source 1.
The second constant current source 2 is a transistor connected in parallel with each other.
Q_Three, Q_FourAnd these transistor Q_Three, Q_FourAnd resistance R_ThreeThrough
Transistor Q whose base is commonly connected_FiveAnd each transition
Star emitter resistance R_Four, R_FiveThe current mirror circuit consists of
The constant current value I of the first constant current source 1_Oof
Double current value 2I_OIs designed to inhale. First and second
And the second constant current source 1, 2 common connection point, that is, the transistor Q
_TwoAnd transistor Q_Three, Q_FourCollector common connection point and reference voltage
Condenser, which is a means of storing electricity, is connected to the
C₁Is connected.   Capacitor C₁The voltage across the₁, COMP
_TwoComparing the comparison circuit 3 consisting of
Input, ie Comparator COMP₁Inverting input and COMP_TwoNon
Inverted input. Comparison criteria for the upper and lower limits of the comparison circuit 3
Level V_UAnd V_LAre four resistors R connected in series with each other_Five
~ 8₈Set by dividing the reference power supply voltage Vref by
I have. Resistance R_Five~ R₈Further reduces the reference power supply voltage Vref to approximately 1/2.
Operational amplifier OP with voltage divider and voltage follower circuit configuration₁Through 1
Set to / 2Vref. The two comparison outputs of the comparison circuit 3, that is, the
Parator COMP₁, COMP_TwoEach output of RS-flip-flop
It becomes 4 sets (S) of 4 and a reset (R) input. Step
The output of the lip flop (hereinafter simply referred to as FF) 4 is
Transistor Q₆And resistance R₉, R_TenConsisting of a second constant current source 2
Is supplied to the control circuit 5 that controls activation / deactivation of
You. This control circuit 5 includes a transistor Q₆Is the output of FF4
Transistor Q in response to_Three, Q_FourOff
By setting the state, the second constant current source 2 is deactivated.
State.   Emitter resistance R in the second constant current source 2_FiveVoltage across
Is an operational amplifier OP with voltage follower circuit configuration_TwoInverted input of
ing. Operational amplifier OP_TwoIs the resistance R₁₁, R₁₂Reference power source
The comparison reference level is set by dividing the voltage Vref.
The first and second constant current sources 1 and 2 according to the comparison output.
The current value setting circuit 6 for setting the constant current source of
You.   Capacitor C₁The voltage between both ends is the operation of the voltage follower circuit configuration.
Amplifier OP_ThreeWhen it becomes the first phase triangular wave signal φa via
OP amplifier_FourAnd resistance R₁₃, R₁₄Inverter consisting of
The phase of the triangular wave signal φa of the first phase is inverted by 7
It becomes the second phase triangular wave signal φb. These triangular wave signals φa,
A direct current bias of 1/2 Vref is applied to φb. Again FF4
The Q output of is added to the Toruga terminal of FF12,
Acts as a number.   Due to the above, the two peak phases are almost equal and opposite to each other.
The triangular wave generation circuit 8 for generating the triangular wave signals φa and φb of
Has been established. In the triangular wave generation circuit 8, a constant current source
I_OFirst constant current source 1 and constant current value 2I_O2nd constant current
Flow source 2 is provided to control ON / OFF of the second constant current source 2.
By capacitor C₁Is charged and discharged with a constant current.
Since it is configured to generate a triangular wave,
When integrating 8 into an IC (integrated circuit), capacitor C₁For
And only one terminal pin (terminal 8a in Fig. 1)
There is an advantage to say.   Two-phase triangular wave signals φa and φb are used for comparator COMP_Three, COMP
_FourAn upper and lower limit comparison reference input of the comparison circuit 9 consisting of
That is, the comparator COMP_Three, COMP_FourIt becomes each inversion input of. ratio
The comparison input of the comparison circuit 9, that is, the comparator COMP_Three, COMP_Fourof
The drive signal of the motor M, which is a load as each non-inverting input,
No. is resistance R_FifteenIs supplied via Comparator COMP_Three, C
OMP_FourA resistor R is attached to each non-inverting input of₁₆(R_Fifteen= R₁₆) Through
Reference voltage Vref is applied to the resistor R_Fifteen, R₁₆of
Since the resistance values are set equal, the drive signal
1 / 2Vref when it becomes the comparison input of the window comparator 9
Will be biased to. That is, the drive signal
The signal reference level becomes 1/2 Vref.   As a result, the circuit reference level of the triangular wave generation circuit 8 is
The comparison reference level of the comparison circuit 3 and the DC via of the drive signal
Level power supply (signal reference level)
It will be set by the resistance voltage division of the voltage Vref. Follow
Even if the power supply voltage fluctuates, two-phase triangular wave signals φa and φ
The relative signal level between b and the drive signal is always kept constant
Will always be stable regardless of fluctuations in the power supply voltage.
The specified circuit operation is performed.   Comparator COMP_ThreeThe comparison output of AND gate 10 and NOR
It becomes one input of each of the gate 11, and the comparator COMP_Fourcomparison
The output becomes the other inputs of the AND gate 10 and the NOR gate 11.
As a result, the output terminals of the AND gate 10 and NOR gate 11
Is the first and second pulses corresponding to the driving direction of the motor M.
Signal will be derived.   The drive signal described above is the resistance R_FifteenThrough the comparator COM
P_FiveIt is also the non-inverting input of. Comparator COMP_FiveIs 1
By setting / 2Vref as the inverting input, the signal reference level of the drive signal
Consists of polarity determining means for determining the polarity of the bell
You. Comparator COMP_FiveDiscrimination output is D-FF12 data
(D) It becomes an input. D-FF12 is in the triangular wave generation circuit 8
Trigger the RS-FF4 Q output as a triangular wave inversion signal
(T) Input, and its Q and output are AND gates 13 and 14, respectively.
Input. AND gates 13 and 14 are AND gate 10 and NOR gate.
11 output, that is, the first and second pulse signals, respectively.
It is used as the other input, and is based on the Q and output of D-FF12.
Outputs only one of the first and second pulse signals
It constitutes a gate means for applying force.   Each output pulse of AND gates 13 and 14 is
Diode D for absorbing back electromotive force in live circuit 18₁, D_Two
Compensation Circuit Compensating for Energy Loss Due to Counter Electromotive Force
Supplied to 15,16. In the compensation circuit 15, the AND gate 13
The output pulse of resistor R₁₇Through the transistor Q₇Bee
This transistor Q₇Is the capacitor C_TwoAverage
Column connected. Capacitor C_TwoIs the transistor Q₇No
Both ends are short-circuited at the
Transistor Q₇Is turned off, that is, the AND gate 13
Charged by constant current source Ia from the time the output pulse disappears
Is started. Capacitor C_TwoThe voltage across both ends of the comparator
COMP₆Inverted input of. Comparator COMP₆Is the reference voltage
E_OIs a non-inverting input and capacitor C_TwoIs the reference voltage
Pressure E_OWhen it is lower, a high level pulse signal is generated. So
As a result, from the compensation circuit 15 to the output pulse of the AND gate 13.
In contrast, a pulse with a pulse of almost constant pulse width added
A signal will be output.   Compensation circuit 16 is the same as₁₈, Tran
Jista Q₈, Capacitor C_Three, Constant current source Ib and comparator
COMP₇Compensation circuit 15
Is exactly the same as   Each output pulse of the compensation circuits 15 and 16 is the pre-drive circuit 1
It is supplied to the motor drive circuit 18 via 7. motor
In the drive circuit 18, the motor M is a PNP type transistor.
Q₉And NPN transistor Q_TenAnd PNP transistor Q₁₁
And NPN transistor Q₁₂Between the common connection points of
Has been continued. Transistor Q₉, Q_Ten, Q₁₁, Q₁₂Is powered
It is a randista. Transistor Q₉, Q₁₁Each emitter of
Direct power V_CCAnd each base has its own resistance R₁₉, R
₂₀Power through V_CCIt is connected to the. On the other hand, Transi
Star Q_Ten, Q₁₂Each emitter is grounded together and each base is
Resistance R_{twenty one}, R_{twenty two}Grounded through and Zener
Diode ZD₁, ZD_TwoIs connected to each collector via
You. Both ends of the motor M are diodes D for absorbing back electromotive force.₁, D_Two
Power through V_CCIt is connected to the.   In the pre-drive circuit 17, supplied from the compensation circuit 15.
The pulse signal is a resistance R_{twenty three}, R_{twenty four}And transistor Q₁₃From
Power transistor Q through the pre-drive stage₉Drive
The resistor R_{twenty five}~ R
₂₇And transistor Q₁₄Via a pre-drive stage consisting of
Power transistor Q₁₂Drive. This allows you to
A current in the direction of the arrow indicated by the solid line in the figure flows through the motor M,
The motor M is rotationally driven in the positive direction. Also compensation
The pulse signal from the circuit 15 is transferred through the inverter 20 to the transistor.
Jista Q_FifteenIs also supplied to the motor M to stop the forward drive.
Sometimes the transistor Q_FifteenTurn on. This
Power transistor Q_FifteenWill be shorted by
Power transistor Q₁₂Turns off instantly. this
Transistor Q_FifteenI will explain in detail later why
explain. Transistor Q_FifteenThe base of the resistance R₂₈Through
Power supply V_CCIt is connected to the.   On the other hand, the pulse signal supplied from the compensation route 16 is the resistance R
₂₉, R₃₀And transistor Q₁₆A pre-drive stage consisting of
Through power transistor Q₁₁Drive the
Resistance R after being inverted by barter 21₃₁~ R₃₃And transistor
Q₁₇Power transis via a pre-drive stage consisting of
Q_TenDrive. As a result, the motor M has a broken line
The current flows in the direction of the arrow indicated by, and the motor M rotates in the opposite direction.
Will be driven. In addition, from the compensation circuit 16 to the constant current source
Transistor Q via inverter 22₁₈Also supplied
When the reverse drive of the motor M is stopped, the transistor
Q₁₈Turn on. This allows the power transistor Q
_TenBetween the base and emitter of the transistor Q₁₈By short
Power transistor Q_TenIs instantly off
State. Transistor Q₁₈The base of the resistance R₃₄Through
Power supply V_CCIt is connected to the.   Next, regarding the circuit operation of the PWM drive circuit according to the present invention
explain.   First, the circuit operation of the triangular wave generation circuit 8 is shown in the waveform diagram of FIG.
Will be described with reference to. In the triangular wave generation circuit 8,
2 constant current source 2 is in a deactivated state, that is,
Jista Q₆Turning on the transistor Q_Three, Q_FourIs off
Sometimes, capacitor C₁Is supplied from the first constant current source 1.
Due to the constant current generated, as shown in FIG.
It is charged with a tilt angle. Capacitor C₁Voltage across
Upper limit reference level V of comparison circuit 3_UWhen the comparator is reached
COMP₁Generates a low level pulse (b),
In response to (b), RS-FF4 output (d) goes low
Transition. This allows the transistor Q₆Is off
Therefore, the second constant current source 2 is in an activated state,
Star Q_Three, Q_FourTurns on and the constant current of the first constant current source 1
The current is drawn in twice as much as the current.   As a result, the capacitor C that was in the charged state until then₁Is
At the time of charging, as shown in FIG.
The discharge is performed with the same inclination angle as. Then,
Densa C₁Is the lower limit reference level V of the comparison circuit 3_LTo
When it reaches Comparator COMP_TwoIs a pair-level pulse (c)
Is generated and RS-FF4 is output in response to this pulse (c).
The force (d) transitions to a high level. This allows the transition
Star Q₆Turns on and deactivates the second constant current source 2.
Then, again, the capacitor C₁Is the first constant current source 1
Charged with a constant inclination angle by a constant current supplied from
Will be done.   In this way, the constant current generated by the first and second constant current sources 1 and 2
Current C₁That the charging and discharging operations of
Than the capacitor C₁The voltage across both ends is shown by the solid line in Fig. 2 (a).
It changes into a triangular wave as shown in, and the operational amplifier OP_ThreeThrough
Output as first phase triangular wave signal φa
By the phase inversion at 7, the broken line in FIG.
As shown, is the first phase triangular wave signal φa equal to the peak value?
Output as a triangular wave signal φb of the second phase of the opposite phase
become. These two sets of triangular wave signals φa and φb are output from the comparison circuit 9.
It becomes the reference input.   As a comparison input of the comparison circuit 9, a 1/2 Vref signal reference
A drive signal of a motor having a level is supplied. here
Then, the motor M rotationally drives, for example, a compact disc.
If the spindle motor is
The error obtained by comparing the raw sync signal with the reference sync signal.
Error signal becomes the above drive signal, and based on this error signal
Drive control of the spindle motor is performed.
You. This is the so-called spindle servo.   In FIG. 3, two sets of triangular wave signals φa and φb are crossed.
The point is at 1/2 Vref level, and at this 1/2 Vref level
In contrast, when the signal level of the drive signal is high or low
The PWM operation will be described below.   In the comparison circuit 9, first, the signal level of the drive signal is
As shown by the chain line in Fig. (A), it is higher by the 1/2 Vref level.
If not, the comparator COMP_ThreeOutput (b) is the drive signal
Signal level of the first phase triangular wave signal φa
When the bell goes low t₁Transition from low level to high level
However, the signal level of the triangular wave signal φa is the signal level of the drive signal.
Point t_FourMaintain a high level up to. In addition,
Parator COMP_FourOutput (c) is the second phase triangular wave signal φ
Time t when the signal level of b exceeds the signal level of the drive signal_Two
Transitions from the high level to the low level with the signal level of the drive signal.
When it becomes lower than_ThreeThen transition to high level again.   On the other hand, the signal level of the drive signal is indicated by the double-dashed line in Fig. (A).
In case of lower than 1/2 Vref level as shown and above
If it has the same absolute value level as
COMP_Three(D) is the signal level of the first phase triangular wave signal φa.
Time t when the bell exceeds the signal level of the drive signal_TwoAt low level
To a high level, the signal level of the triangular wave signal φa changes
Time t when the signal level of the drive signal is exceeded_ThreeUp to high level
Carry. Also, the comparator COMP_FourOutput (e) is
The signal level of the two-phase triangular wave signal φb is the signal level of the drive signal.
Time t when the bell is crossed₁Transition from high level to low level,
Time t when it becomes lower than the signal level of the drive signal_FourHigh again
Transition to bell.   Comparator COMP_Three, COMP_FourEach output of AND gate 10 and
NOR gate 11 has 2 inputs, AND gate 10 has 2 inputs
When both forces are high level, that is, the signal level of the drive signal is
High level pulse (f) when higher than 1/2 Vref level
NOR gate 11 outputs both when both inputs are low level,
That is, if the signal level of the drive signal is lower than 1/2 Vref level
Outputs high level lus (g). Therefore, AND game
The gate 10 and the NOR gate 11 correspond to the driving direction of the motor M.
The pulse signals (f) and (g) will be output. What
Note that here, only when the signal level of the drive signal is constant,
Pulse width of pulse signals (f) and (g)
Is constant, but this pulse width is the signal of the drive signal.
It is easy to understand that it changes depending on the level.   In this way, the peak values are equal and opposite phases of 2
Generate the two-phase triangular wave signals φa and φb.
To perform PWM operation using the straight line parts of signals φa and φb
Ringing on the tip of the triangular wave
Therefore, even if so-called rounding occurs, the signal level of the drive signal
There is no deterioration in linearity when the bell becomes small, so
is there.   If the reference power supply voltage Vref fluctuates, the PWM
The pulse width of the pulse signal generated by
The drive power due to the loose signal changes according to the fluctuation of the power supply voltage
Will be done. That is, as shown in FIG.
Pulse signal when the drive signal is at a certain signal level
Pulse width of T_OThen, the drive voltage by this pulse signal
Force is its pulse width T_OAnd drive voltage V_D(Reference power supply voltage
Vref) is defined as the product of
Live voltage V_DIf, for example, becomes 1/2, the driving power will also be
As shown by the line, it will be halved.   However, in the triangular wave generation circuit 8, the first and the first
Current value setting circuit to set the constant current value of 2 constant current sources 1 and 2
The reference level of 6 is resistance R₁₁, R₁₂Reference power supply voltage V
It is set by the partial pressure of ref.
Since it fluctuates according to the fluctuation of the power supply voltage, the current
The value setting circuit adjusts the first and second constants according to the fluctuation of the power supply voltage.
The constant current value of the current sources 1 and 2 can be controlled. The result
As a result, the inclination angle of the triangular wave changes, as shown in Fig. 4 (B).
Will be done. On the other hand, the ratio of the upper limit and the lower limit of the comparison circuit 3
Comparative reference level V_U, V_LAlso resistance R_Five~ R₈Reference power supply voltage Vre
Since it is set by dividing the voltage of f, the reference power supply voltage Vre
If f becomes 1/2, the upper and lower comparison reference levels V_U, V_L
Also becomes 1/2, and as a result, the peak value V of the triangular wave_PIs Fig. 4
As shown in (B), it is half that before the power supply fluctuation. Therefore, three
The repetition cycle of the angular wave is the same before and after the power fluctuation.
By setting the inclination angle of the triangle wave,
Double (2T_O), A pulse signal having a pulse width of
Drive voltage V_DEven if it becomes 1/2
The driving power due to the output signal becomes the same as before the power supply change.   That is, in the triangular wave generation circuit 8, the triangular wave
The peak value and tilt angle can be controlled according to the fluctuation of the power supply voltage.
The drive power by the pulse signal is
It can be kept constant regardless of changes in ef. Three
The angle of inclination of the angular wave is the constant current value of the first and second constant current sources 1 and 2.
And capacitor C₁Determined by the capacity of.   Again in FIG. 1, the signal level of the drive signal is now
If it changes as shown by the chain line in Fig. 5 (a),
2 of pulse width according to the polarity and signal level of the drive signal of
Two pulse signals (b) and (c) are connected to the AND gate 10 and NOR gate.
Output from the gate 11 and each of the AND gates 13 and 14
Help. Drive signal is COMP of comparator_FiveComparison input
Therefore, the polarity with respect to the signal reference level 1/2 Vref is known.
Separated. This comparator COMP_FiveComparison output (d)
D-FF12, which is used as data input, is stored in the triangular wave generation circuit 8.
RS-FF4 Q output (e)
Is input and the timing of the fall of the Q output (e)
Q, outputs (f) and (g) are generated. This Q, out
Forces (f) and (g) are AND gates 13 as gate control signals.
Supplied to 14.   In the above embodiment, the Q output (e) of RS-FF4 is directly changed.
Trigger input of line D-FF12, but rising of Q output (e)
Pulse generation that generates pulses at the rising and falling timings
It is also possible to use it as a trigger input for the D-FF12 via a living instrument.
is there. According to this, the cycle of polarity determination is halved,
You will be able to double the resolution.   Q of D-FF12, output (f), (g) drive motor M
It becomes the control signal that determines the direction, for example, the signal of the drive signal.
Timin whose level is small and whose polarity changes from positive to negative
The NOR gate 11 instantly fires as shown in Fig. 5 (c).
In the generated reverse drive pulse signal (first pulse)
On the other hand, at the time of occurrence, the output (g) goes low.
Therefore, the AND gate 14 does not operate to prohibit its output.
You. The reason for prohibiting this will be described below.   Now, the signal level of the drive signal is low and its polarity is positive.
From the NOR gate at the timing of changing from negative to negative
Instantaneous reverse drive pulse signal is generated as shown in (c).
In the case of doing so, in the motor drive circuit 18, the fifth
Transistor Q in response to the pulse signal shown in FIG.₉, Q
₁₂Is turned on and the motor M is being driven in the forward direction.
However, the reverse drive pulse signal shown in Fig. 5 (c) is used.
Signal is generated, the transistor Q₉, Q₁₂Is off
Becomes, transistor Q₁₁, Q_TenTurns on and the motor
Attempts to drive M in the opposite direction.   Here, the transistor is generally as shown in FIG.
Capacitance C between base and emitter_OBy the existence of
Transistor in the on state in response to the dynamic pulse (a)
From the time of disappearance of pulse (a) to the off state
To t_OFFIt has the characteristic that it requires a delay time. Obedience
Therefore, as described above, the reverse drive shown in FIG.
When a pulse signal is generated, the transistor Q₉, Q₁₂But
Turned off and transistor Q₁₁, Q_TenTurns on
It should be, but the above delay time t_OFFBy tiger
Transistor Q₁₂Cannot be turned off instantly, and temporarily
Transistor Q₁₁At the same time, there is a period in which it is in the ON state
So transistor Q₁₁, Q₁₂Large current flows
The transistor may be destroyed.
You.   However, in this PWM drive circuit, AND gates 13 and 14 are installed.
The gates 13 and 14 to the signal reference level of the drive signal.
It was controlled based on the result of polarity discrimination
In the case of the above example, the reverse drive shown in FIG.
Responding the output of the motion pulse signal to the output (g) of D-FF12
Since it can be prohibited by AND gate 14, transistor Q₁₂Is
Transistor Q₁₁At the same time, it will not be turned on.
is there.   Also, power transistor Q₁₂, Q_TenDelay time t
_OFFIn order to reduce the
Transistor Q_FifteenAnd Q₁₈Is provided. These transitions
Star Q_Fifteen, Q₁₈Is the power transistor Q₁₂, Q_TenDrive pulse of
In response to the disappearance of the
Jista Q₁₂, Q_TenTo short the base and emitter of
From the above delay time t_OFFCan be shortened. Tiger
Delay time of register t_OFFIs generally about 1-2 μsec
There is a transistor Q_FifteenAnd Q₁₈By providing
It can be shortened to about 1/10, that is, about 100 nsec.   Others for preventing the power transistor synchronization ON
An example of is shown in FIG. In this figure, as described above
First and second pulse signals corresponding to the driving direction of the motor M
No. (a) is output from AND gate 10 and NOR gate 11,
These pulse signals are delayed by the delay circuits 23 and 24 for a predetermined time.
τ_OOnly delayed. These delayed outputs (b) are
It is supplied to the 3-state buffers 25 and 26. Also, the first and
And the second pulse signal (a) is a one-shot multi-vibe
It is also supplied to the vibrators 27 and 28, respectively. One shot
The multivibrator 27, 28 is used for the first and second pulse signals.
From the time of occurrence to a certain time after its disappearance, preferably a delay circuit
23,24 delay time τ_OTwice the time (2τ_O) Just passed
Generate low level output (c) until
The second and the second output supplied from the delay circuits 24 and 23 to the 26 and 25
The supply of the first pulse signal to the next stage is prohibited.   FIG. 8 is an operation waveform diagram of the circuit shown in FIG.
(A) to (c) are the signals (a) to (c) of FIG.
The waveforms are shown correspondingly. See this waveform diagram
Then, the circuit operation of FIG.
To explain, the pulse signal (a) is delayed by the delay circuit 23.
τ_OIs delayed only to become the drive pulse (b) for the motor M.
But at this time, one-shot multi-vibrator
In response to the low level inhibit signal (c) output from 27
Buffer 26 shuts off the output line of the other drive pulse
And As a result, before and after the drive pulse (b) is generated.
A certain period after birth (time τ_O) Between local drive pulses
Since the force will be banned, time τ_OOf the above
Work transistor Q₁₂, Q_TenDelay time t_OFFLonger than
Power transistor Q₉And Q
_Ten(Or Q₁₁And Q₁₂) Are never turned on at the same time
It is.   As mentioned above, the delay time of the transistor
t_OFFIs generally about 1 to 2 μsec, so time τ_O5
It is desirable to set it to about μsec.   In FIG. 1, the mode output from AND gates 13 and 14 is
The first and second pulse signals corresponding to the driving direction of
It is supplied to the compensation circuits 15 and 16, respectively. These compensation circuits 1
5, 16 are counter electromotive force supply inductors in the motor drive circuit 18.
Iod D₁, D_TwoTo compensate for the energy loss in
Things. Counter electromotive force absorption diode D₁, D_TwoEnergy in
The rugie loss is almost constant, and the pulse width of the pulse signal is
Pulses that are negligible when large
When the width is small, the loss ratio becomes large. Follow
Then, as shown by the broken line in FIG. 9, the pulse width of the pulse signal
Since the gain will decrease in the area where
Diode D for supplying back electromotive force when width is small₁, D_Twoso
You just have to compensate for the energy loss.   Here, regarding the circuit operation of the compensation circuit 15, the waveform of FIG.
If you explain with reference to the figure, the capacitor C_TwoIs a constant current
Charged at constant current by source Ia, input pulse
Transistor Q in response to (a)₇Is turned on
By capacitor C_TwoCharge is instantly discharged and
When the force pulse (a) disappears, the capacitor C is restarted._TwoIs
It is charged with a constant current. Therefore, the capacitor C_TwoOf both ends
The pressure changes as shown in FIG. 10 (b). This voltage across
(B) Comparator COMP₇With reference voltage E_OCompared to
As a result comparator COMP₇Input pulse at the output of
After the occurrence of (a), a certain time Ta elapses after the disappearance.
A pulse signal (c) having a pulse width of up to
Will be. That is, for the input pulse (a)
This means that a constant pulse width Ta has been added.
The counter electromotive force is generated by the energy corresponding to the pulse width Ta
Force absorption diode D₁, D_TwoCompensation for energy loss in
You can.   FIG. 11 shows the input / output characteristics of the compensation circuits 15 and 16, that is, the input parameters.
The relationship between the pulse width of the pulse and the added pulse width is shown.
The capacitor C_TwoThe voltage across both ends of the comparator COMP₇
Reference voltage E_OPulse of the input pulse
In the pulse width region, the pulse width is not added and the reference voltage E_OLess than
In the area until reaching the zero level, the additional pulse width is relatively
Changes to and is added in the area after reaching the zero level.
The pulse width is fixed. That is, the input pulse
In the region where the pulse width is extremely small, additional pulse width
This is because there is nothing or the additional pulse width changes relatively.
This is because the rising and falling edges of the input pulse are not sharp
Is due to the fact that the
In the result area, the gain is adjusted as shown by the solid line in FIG.
You can do it.   As the compensating circuits 15 and 16, those having the configuration of the above embodiment
Without limitation, for example, as shown in FIG.
Has a constant pulse width Tb in response to the rising edge of the pulse.
Pulse generator circuit 29 that generates a pulse signal for
The logical sum of the output pulse and the input pulse of the pulse generator 29
It may be configured with the OR gate 30.
In such a configuration, the pulse width of the input pulse is
If it is smaller than the pulse width Tb, the pulse width Tb is always
By outputting the pulse signal from the OR gate 30,
Diode for absorbing back electromotive force when input pulse width is small
D₁, D_TwoThe energy loss in the
Input when the pulse width of the pulse exceeds the above pulse width Tb.
No change in pulse width is made for the pulse.   In the above example, the compact disc was rotated.
When applied to the drive circuit of a moving spindle motor
However, the present invention is not limited to this.
For carriage motors and pickups that drive backup
Control of focus and tracking of information reading light in
Eggplant focus actuator and tracking actuator
It can also be applied to the drive circuit of the data,
Various loads not only on the sprayer but also on various devices
It is widely applicable to the drive circuit of. The invention's effect   As described above, the PWM drive circuit according to the present invention
The triangular wave signal to generate the pulse signal that drives the load.
Since it is configured to use only the straight line part, the triangular wave
There is ringing or bluntness on the tip of the
However, it is not affected by any of these, especially the drive signal.
Of the input / output characteristics when the signal level of the signal decreases
It will be possible to improve.   In addition, the polarity of the drive signal with respect to the signal reference level is determined
The drive pattern corresponding to the drive direction based on this determination result.
I decided to supply only Ruth to the power drive stage
And the transistor t_OFFDue to the delay time
Surely prevent the transistors in the word drive stage from turning on simultaneously.
Can be

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG.
FIG. 4 is a waveform chart of each part for explaining the circuit operation of the triangular wave generation circuit in the figure, and FIG. 3 is a waveform diagram of each part for explaining the operation of generating two pulse signals corresponding to the drive direction of the load by the PWM operation, FIG. (A) and (B) are waveform charts for explaining the operation of changing the inclination angle and the peak value of the triangular wave in response to the fluctuation of the power supply voltage, and FIG.
Waveform diagram of each part for explaining the circuit operation of the simultaneous ON prevention circuit of the power transistors in the drive stage due to the _OFF delay time, FIG. 6 is a diagram for explaining the t _OFF delay time of the transistor, and FIG. FIG. 8 is a block diagram showing another embodiment of the ON prevention circuit, FIG. 8 is a waveform chart of each part for explaining the circuit operation of FIG. 7, and FIG. 9 is energy loss due to counter electromotive force in the counter electromotive force absorption diode. Fig. 10 shows the change in gain caused by the above, Fig. 10 is a waveform diagram for explaining the circuit operation of the compensation circuit that compensates the energy loss due to back electromotive force in the back electromotive force absorption diode, and Fig. 11 is such FIG. 12 is a diagram showing input / output characteristics of the compensation circuit, FIG. 12 is a block diagram showing another embodiment of the compensation circuit, and FIG. 13 is a diagram for explaining a conventional example and its operation. Explanation of symbols of main parts 1 ... First constant current source 2 ... Second constant current source 3,9 ... Comparison circuit 8 ... Triangular wave generation circuit 15,16 ... Compensation circuit 17 ... Pre-drive circuit 18: Motor drive circuit

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Kobayashi               Kawagoe City, Yamada, Nishimachi 25-1, Pio               Near Kawagoe Factory (72) Inventor Akio Namiki               Kawagoe City, Yamada, Nishimachi 25-1, Pio               Near Kawagoe Factory                    Examiner Ryozo Arizumi                (56) References JP-A-60-153219 (JP, A)                 JP 54-80657 (JP, A)                 JP-A-54-100653 (JP, A)

Claims (1)

(57) [Claims] A PWM (pulse width modulation) drive circuit for generating a pulse signal having a pulse width according to the signal level of a drive signal and switching-driving a load based on the pulse signal,
Triangular wave generating means for generating two-phase triangular wave signals having substantially equal peak values and opposite phases to each other; and a comparison circuit using the two-phase triangular wave signals as upper and lower reference inputs and the drive signal as a comparison input, respectively. First gate means for outputting first and second pulse signals corresponding to the drive direction to the load based on an output of the comparison circuit; and a polarity of the drive signal with respect to a signal reference level as a data input, Only one of the first and second pulse signals is input based on the determination result of the input signal polarity determination means that uses the triangular wave inversion signal output from the triangular wave generation means as a trigger input. A PWM drive circuit comprising: second gate means for outputting, and driving the load based on an output of the second gate means.