JP2006269930A - Pulse control circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pulse control circuit which outputs an output signal having the maintained duty ratio of a pulse width modulated signal as an input signal and having a varied period. <P>SOLUTION: A pulse control circuit 3 for outputting a second pulse signal CP to a drive circuit of an actuator on the basis of a pulse-width-modulated, first pulse signal P comprises a measuring unit 31 for measuring waveform information including at least duty ratio of the first input pulse signal P, and a pulse output unit 33 for outputting the second pulse signal CP having the maintained duty ratio and having a varied period of the first pulse signal. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pulse control circuit that controls a pulse signal subjected to pulse width modulation for driving an actuator and outputs the pulse signal to an actuator drive circuit.

  Pulse width modulation (PWM) is well known as a method for controlling the operation of actuators such as solenoids and motors to control the operation of these actuators. In general, in this PWM, the ratio between the high level (hereinafter referred to as H level) and the low level (hereinafter referred to as L level) of the pulse signal, that is, the duty ratio is changed within one cycle of the pulse having a constant cycle. By this duty ratio, the ratio of the effective period (for example, H level) within one cycle is determined, and the current flowing through the actuator is controlled by this ratio.

  In such PWM, the duty ratio of the pulse signal varies, but the pulse period is constant as described above. The pulse signal is a signal including a high-frequency component when the waveform rises and falls. Therefore, when the actuator is driven by a pulse signal, this high frequency component becomes radiation noise. Driving the actuator requires a larger current than an electronic circuit such as a microcomputer. Therefore, this radiation noise generated when the actuator is driven has a large energy (electric power) and has a great influence on other circuits and devices. It may cause malfunction of other circuits, noise of audio equipment or image equipment, or disturbance of images.

  Therefore, various measures have been proposed to disperse the peak frequency of the high frequency component so that the energy of the radiation noise does not concentrate on a specific frequency. Patent Document 1 shown below describes a driving method for driving a solenoid as an actuator by PWM control. According to this, the duty ratio for PWM control is calculated, and the period of the pulse is increased or decreased periodically or randomly while maintaining this duty ratio. That is, by changing the pulse period, the radiation noise due to the above-described high frequency component is prevented from being fixed to a specific frequency.

Japanese Examined Patent Publication No. 6-27510 (page 2-3, FIG. 4)

  Incidentally, the calculation of the duty ratio for performing the PWM is generally performed using a microcomputer or the like in many cases. Since the fluctuation range of the pulse cycle is smaller than the fluctuation range of the duty ratio, finer control is required to change the pulse cycle. In order to perform finer control with a microcomputer, an operating frequency corresponding to the fineness is required. There is no problem when the actuator control is relatively slow, that is, when the pulse period is relatively long, but the microcomputer is also required to operate at high speed when high speed control is required.

  That is, even a microcomputer having sufficient performance with respect to the period of generated pulses and duty control may not be sufficient to finely vary the period of pulses. In this case, due to fluctuations in the pulse period, it is necessary to take measures such as increasing the operating clock of the microcomputer or using a high-performance microcomputer. However, increasing the clock speed will also create a new cause of radiation noise. In addition, the use of a high-performance microcomputer only for this purpose leads to an increase in cost, which is not preferable. In addition, when another microcomputer is used for the fluctuation of the cycle in an environment where past design assets can be utilized, extra man-hours such as program development are generated.

  Here, if a pulse control circuit for changing the cycle of the pulse signal output from the microcomputer or the like and outputting it to the drive circuit is provided, the cycle of the pulse signal can be changed without depending on the pulse generation means such as the microcomputer. Can do. In recent years, with the high-speed operation of equipment, the problem of radiation noise due to high-frequency components of pulse signals has become increasingly important. For this reason, various circuits (integrated circuits) that perform spread spectrum that changes the period of a pulse signal input at a constant period at a constant period are also provided.

  Various types of such circuits are available that are inexpensive and can handle a wide range of frequencies, but these do not take into account the duty ratio of the original signal when changing the period. As a general spread spectrum circuit, a frequency feedback control circuit called PLL (Phase Locked Loop) is used. The PLL mainly includes a phase comparator, a low-pass filter, and a voltage controlled oscillator (VCO). The PLL operates so as to determine the frequency (period) by comparing the edges of the pulses generated by the VCO with a phase comparator. Therefore, since the output signal is generated by the VCO, the duty ratio of the input pulse signal is not considered. For this reason, if the period of the PWM-controlled signal is changed using such a spread spectrum circuit, the duty ratio of the PWM control is destroyed.

  The present invention has been made in view of the above problems, and provides a pulse control circuit that uses a pulse-width modulated signal as an input signal and outputs an output signal whose period is changed while maintaining the duty ratio of the input signal. The purpose is to do.

In order to achieve the above object, the characteristic configuration of the pulse control circuit according to the present invention is:
Based on the pulse width modulated first pulse signal, the second pulse signal is output to the actuator drive circuit, and measurement is performed to measure waveform information including at least the duty ratio of the input first pulse signal. And a pulse output unit that outputs the second pulse signal by changing the cycle of the first pulse signal while maintaining the duty ratio.

  According to this characteristic configuration, since the measurement unit that measures the waveform information of the first pulse signal subjected to the pulse width modulation is provided, the pulse control circuit can be provided completely separate from the control unit that performs the pulse width modulation. Moreover, since the pulse output unit outputs the second pulse signal at an arbitrary period based on the duty ratio based on the measured waveform information, the period of the pal signal can be changed while maintaining the duty ratio.

  A random number generation unit; and a diffusion period setting unit that determines a diffusion period that is a period of the second pulse signal based on the random number generated by the random number generation unit, wherein the pulse output unit includes the diffusion period and The second pulse signal is preferably output based on the waveform information.

  When the change of the pulse period is varied at a constant period, for example, the peak power of the radiation noise due to the high frequency component is attenuated, but a mountain corresponding to the constant period of the fluctuation also appears. As described above, when the change of the pulse period is changed randomly based on the random number, the peak of the radiation noise corresponding to this fluctuation period can also be reduced.

  The measurement unit preferably includes a waveform information holding unit that holds the measured waveform information.

  When the period of the first pulse signal is changed at a constant period, the next period can be predicted. However, when the period of the first pulse signal is changed randomly using a random number or the like, the next period cannot be predicted. For example, if the setting of a significantly shorter pulse period than the period of the first pulse signal continues, the second pulse signal may have to be output before the first pulse signal is input. Therefore, it is preferable to store the waveform information for several cycles of at least about 1 to 2 cycles to deal with the above case. Therefore, as described above, when the waveform information holding unit that holds the measured waveform information is provided, the second pulse signal can be output satisfactorily based on the first pulse signal.

  In addition, an abnormality processing unit that detects interruption of the first pulse and instructs to generate an interpolated pulse during the interrupted period, and the pulse output unit responds to an instruction from the abnormality processing unit according to the instruction from the diffusion period. And outputting the second pulse signal based on the waveform information.

  According to this feature, when the input of the first pulse signal is interrupted for about 1 to 2 periods due to noise or the like, the interpolation is performed, so that the actuator can be driven satisfactorily. Here, the case where the first pulse signal is interrupted includes, for example, a case where an apparently discontinuous period is measured, or an apparently inaccurate duty ratio is calculated as PWM control. The duty ratio of PWM control is usually not discrete but changes continuously. Therefore, the duty ratio of the interrupted portion can be predicted based on the past waveform information already held. Moreover, since the period of a 1st pulse signal is a fixed value, this can be utilized. As described above, it is preferable to generate the interpolation pulse by using the held waveform information, even if a failure occurs in the first pulse signal, it does not affect the drive of the actuator that is the final purpose.

  In addition, it includes an abnormality processing unit that detects an input abnormality detection signal and instructs the output stop of the second pulse according to the detected abnormality, and the pulse output unit responds to an instruction from the abnormality processing unit, It is preferable to stop the output of the second pulse.

  The pulse control circuit according to the present invention generates a second pulse signal based on the input first pulse signal. Therefore, the second pulse signal is output with a delay of at least one cycle, preferably several cycles, compared to the first pulse signal. Therefore, for example, the abnormality detection signal is simultaneously input to a device (for example, a microcomputer) that generates the first pulse signal, and even if this stops the output of the first pulse signal, the second pulse signal does not stop immediately. . However, the second pulse signal can be quickly stopped if the abnormality processing unit instructs the pulse output unit to stop the pulse based on the abnormality detection signal.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an example of an actuator drive system provided with a pulse control circuit according to the present invention. This actuator drive system controls, for example, an electromagnetic solenoid for an active mount of an automobile. The active mount is to suppress the vibration transmitted to the engine frame by moving the electromagnetic solenoid so as to absorb the vibration of the engine. Since it is necessary to control the electromagnetic solenoid following the vibration of the engine, for example, PWM control with a higher frequency (shorter cycle) than that of a solenoid such as a door lock is required.

  The microcomputer 4 as a pulse generating unit performs PWM control and outputs a modulated pulse signal (first pulse signal) P. The pulse control circuit 3 maintains the duty ratio based on the first pulse signal P, spreads the pulse period, and outputs the second pulse signal CP. The pulse control circuit 3 includes an oscillation circuit 3X, and can operate independently of the microcomputer 4 with a unique clock. The pulse control circuit 3 also receives detection signals F (corresponding to abnormality detection signals of the present invention) from various sensors 9 inside the vehicle. The detection signal F is not limited to one but may be a plurality of signal lines from a plurality of types of sensors 9. Moreover, the signal from the microcomputer 4 may be sufficient. That is, detection signals from various sensors may be input to the microcomputer 4 and processed internally, and the microcomputer 4 may input the detection signals to the pulse control circuit 3 as the sensors 9.

  The second pulse signal CP whose period is spread by the pulse control circuit 3 and outputted is inputted to the drive circuit 8. The drive circuit 8 includes a pulse driver unit 5 and a drive unit 2. Here, before describing the drive circuit 8, the power supply of the actuator drive system of the present embodiment will be described.

  System power for the actuator drive system is supplied from a vehicle battery 6 having a power supply voltage + B. Here, + B is about 12V for a general vehicle. The microcomputer 4 and the pulse control circuit 3 are configured by a single or a combination of semiconductor elements having a power supply voltage of 3.3V or 5V. Therefore, the power supplied to the microcomputer 4 and the pulse control circuit 3 is stabilized at a desired power supply voltage VCC (for example, 3.3 V or 5 V) by the stabilized power supply unit 7.

  On the other hand, the electromagnetic solenoid 1a as the actuator 1 is preferably driven by a + B power source in order to ensure a sufficient driving force. However, since the pulse control circuit 3 operates at the power supply voltage VCC as described above, the second pulse signal CP is also a pulse that swings between ground and VCC. Therefore, the pulse driver unit 5 drives (converts voltage) this to a pulse (third pulse signal) DP touched between the ground and + B. At this time, since it is not preferable that the pulse driver unit 5 generate a signal delay, a high-speed driver circuit using a power transistor or a power FET (electrolytic effect transistor) is used. The switching circuit of the drive unit 2 is driven by the third pulse signal DP that is the output signal of the pulse driver unit 5, the drive current flows, and the electromagnetic solenoid 1a operates. The drive unit 2 is configured by a well-known H-type bridge circuit or half-bridge circuit using a power FET or the like.

  The series of operations for driving the electromagnetic solenoid 1a by the actuator driving system of the present embodiment has been described above. The details of the operation of the pulse control circuit 3 provided in the actuator drive system will be described below. FIG. 2 is a block diagram showing an example of the pulse control circuit 3 according to the present invention. FIG. 3 is a timing chart for explaining the relationship between the input signal (first pulse signal P) and the output (second pulse signal CP) of the pulse control circuit 3 according to the present invention.

  The measuring unit 31 is a block that measures the waveform information of the first pulse signal P input to the pulse control circuit 3. Here, the waveform information is the period, pulse width, and duty ratio of the first pulse signal P. In the present embodiment, the period refers to the period from the rising edge to the rising edge of the pulse, and the pulse width refers to either or both of the H level period and the L level period of the pulse in one period. The measuring unit 31 includes a pulse width measuring unit 11, a period measuring unit 12, a duty calculating unit 13, and a duty holding unit (waveform information holding unit) 14.

  The period measurement unit 12 measures the period of the first pulse signal P. That is, as described above, the period from the rising edge to the rising edge of the first pulse signal P is measured. As a result, as shown in FIG. 3, a period T having a constant period is measured. In this waveform example, when the period from the fall of the pulse to the fall is measured, a time different from the period T is measured, and the measurement result is different for each period. This is because the first pulse signal P is a PWM-controlled signal. The pulse control circuit 3 that operates independently cannot always know in advance whether the microcomputer 4 generates the pulse signal P by defining the period at the rising edge or the falling edge. Therefore, the period measuring unit 12 measures both periods from rising to rising and falling to falling, and recognizes the period T based on a measurement result that is recognized as a constant period.

  As shown in FIG. 3, the pulse width measurement unit 11 sequentially measures the H-level period TH and the L-level period TL of the first pulse signal P. Alternatively, either the H level period TH or the L level period TL is sequentially measured. Then, the ratio of the H level period TH and the L level period TL within the period recognized by the period measurement unit 12, that is, the duty ratio is calculated by the duty calculation unit 13. Then, the calculation results are sequentially held in the duty holding unit (waveform information holding unit) 14.

  The diffusion cycle setting unit 32 includes a random number generation unit 21, a calculation unit 22, and a diffusion cycle holding unit 23. The random number generation unit 21 randomly extracts numerical values within a predetermined range and generates random numbers. The computing unit 21 computes the cycle ST of the second pulse signal CP based on the generated random number and the cycle T (period T) measured by the measuring unit 31. The cycle ST is different from the cycle T of the first pulse signal P and has a different value for each cycle. Therefore, every time the measurement unit 31 (cycle measurement unit 12) detects one rising edge (one cycle), the calculation unit 22 receives a random number from the random number generation unit 21 and calculates one cycle ST. The calculated cycle ST is sequentially held in the diffusion cycle holding unit 23.

  Based on the waveform information (duty ratio) held in the duty holding unit (waveform information holding unit) 14 and the cycle ST held in the diffusion cycle holding unit 23 as described above, the diffusion pulse generation unit 33 newly The second pulse signal CP is generated and output. As shown in FIG. 3, in the first period, the period ST of the second pulse signal CP is set to 1.5 times the period T of the first pulse signal P. In this case, in order to maintain the duty ratio, the period STH1 which is 1.5 times the H level period TH1 is output as the H level period STH of the second pulse signal. Similarly, a period STL1 that is 1.5 times the L level period TL1 is output as the L level period STL of the second pulse signal.

  Hereinafter, in the second period, the third period, and the fourth period, the period ST of the second pulse signal CP is ST2 = T × 0.5, ST3 = T × 0.67, ST4 = T × 1.25 and randomly diffused. Correspondingly, the respective duty ratios maintain the relationship of TH2: TL2 = STH2: STL2, TH3: TL3 = STH3: STL3, TH4: TL4 = STH4: STL4. That is, the cycle is spread while maintaining the duty ratio of TH: TL = STH: STL.

  FIG. 4 is a graph for explaining the diffusion effect of the period T by the pulse control circuit 3 according to the present invention. When the period of the first pulse signal P is not spread, radiation noise due to the PWM fundamental wave output at a constant period of the period T appears with a strong intensity as the frequency fclk, as shown by a waveform E1 in the figure. The n-order harmonic components (second-order harmonic 2fclk, third-order harmonic 3fclk,...) Each appear with a high peak intensity. For this reason, there is a high possibility that the radiation noise of the frequency indicating the peak intensity affects other circuits and devices. However, when the period T is diffused as in the present invention, it is possible to suppress the appearance of the frequency having the peak intensity as shown in the waveform E2.

  In the present embodiment, the cycle ST of the second pulse signal CP is determined based on the random number generated by the random number generation unit 21. However, a method of periodically increasing / decreasing the cycle T around the cycle T may be used. In this case, a small peak of radiation noise corresponding to the increasing / decreasing period appears, but its peak value is lower than the waveform E1 and higher than the waveform E2. Since the random number generator 21 is not provided, the scale of the pulse control circuit 3 can be reduced. Therefore, such a configuration may be adopted when the effect of suppressing radiation noise is sufficiently recognized.

  Further, as shown in FIG. 2, the pulse control circuit 3 includes an abnormality detection unit 39. The abnormality detection unit 39 includes an interruption monitoring unit 91 that detects an abnormality of the first pulse signal P such as an instantaneous interruption of the first pulse signal P. This momentary interruption includes a case where, for example, an apparently discontinuous period is measured due to the influence of external noise or the like, or an apparently inaccurate duty ratio is calculated as PWM control. In such a case, it is not considered that the regular first pulse signal P has been input, and it is recognized that the pulse is missing for about one to two cycles. When the interruption monitoring unit 91 detects this momentary interruption, the interpolation pulse generation instruction unit 92 issues an interpolation pulse generation instruction to the diffusion pulse generation unit 33. The diffusion pulse generator 33 generates an interpolation pulse based on this instruction.

  The duty ratio of PWM control is usually not discrete but changes continuously. Therefore, the duty ratio of the interrupted portion can be predicted based on the past waveform information already held. Further, since the period of the first pulse signal P is a constant value, the number of interrupted periods can be grasped. As described above, when the interpolation pulse is generated using the held waveform information, the second pulse signal CP can be output even if the first pulse signal P is defective.

  As described above, it has been described that the measurement unit 31 and the diffusion period setting unit 32 perform measurement and the setting of the diffusion period in accordance with the period of the first pulse signal P. However, the period of the first pulse signal P is constant. Accordingly, the period of the first pulse signal P is measured and recognized at the initial stage of the operation, and thereafter, the control is performed according to a timer (not shown) in the pulse control circuit 3, and the period T of the first pulse signal P is confirmed for confirmation. May be measured. In particular, the diffusion period ST does not necessarily have to be synchronized with the period T of the first pulse signal P, and may have some stock. Then, the cycle ST stocked as the cycle for generating the interpolation pulse may be used.

  In addition, the abnormality processing unit 39 includes an abnormality detection unit 93 and a pulse stop instruction unit 94. The abnormality detection unit 93 detects an abnormal state from the detection signal input from the external sensor 9. Here, the abnormal state means that, for example, the actuator 1 may not operate due to a mechanical trouble or the like, and an overcurrent may flow. This is detected by an encoder, a photomicrosensor, or the like. When the abnormality detection unit 93 detects such an input of the detection signal F, the pulse stop instruction unit 94 instructs the diffusion pulse generation unit 33 to stop the output of the second pulse signal CP. Upon receiving this instruction, the diffusion pulse generator 39 stops outputting the second pulse signal CP.

  In the pulse control circuit 3, after calculating the duty ratio of the input first pulse signal P, the second pulse signal CP is generated using this duty ratio. Therefore, as can be seen from FIG. 3, the second pulse signal CP is output with a delay of one to two cycles compared to the first pulse signal P. Therefore, for example, even if a signal corresponding to the detection signal F is input to the microcomputer 4 and the microcomputer 4 stops outputting the first pulse signal P, the second pulse signal CP is not stopped immediately. However, if the abnormality processing unit 39 instructs the diffusion pulse generation unit (pulse output unit) 33 to stop the pulse based on the detection signal F, the second pulse signal CP can be quickly stopped.

  The pulse control circuit 3 is constructed by a group of electronic circuits, ASIC (Application Specific Integrated Circuit), FPGA (Field Programmable Gate Array), and PLD (Programmable Logic Device). Alternatively, a single-function dedicated microcomputer or processor may be used. If it is a single function microcomputer or the like, an inexpensive product can be selected even at high speed operation. Moreover, each part of the pulse control circuit 3 described above indicates the sharing as a function, and does not necessarily indicate a physically independent circuit or the like. Therefore, each part of the pulse control circuit 3 may share each function by software such as a program executed on hardware such as a microcomputer.

  In the above description, an example in which one first pulse signal P is converted into one second pulse signal CP has been described, but the number of signals is not limited thereto. For example, when the direction of the current for driving the actuator 1 is reversely controlled, a bridge circuit or the like is used as the drive circuit 8 (drive unit 2), and control in both forward and reverse directions is required. Of course, since control in both the forward and reverse directions needs to be performed synchronously, two types of first pulse signals P may be converted into two types of second pulse signals CP. Further, when a bridge circuit is used, a control signal for returning (regenerating) the induced current generated by the actuator 1 may be added. The control signal for recirculation needs to be synchronized with the control signal for the drive current. Therefore, one first pulse signal P that controls the drive current may be converted into two second pulse signals that control the drive current and the return current. Of course, the present invention can also be applied to these cases.

  As described above, according to the present invention, it is possible to provide a pulse control circuit that uses a pulse-width modulated signal as an input signal and outputs an output signal whose period is changed while maintaining the duty ratio of the input signal. .

The block diagram which shows an example of the actuator drive system provided with the pulse control circuit which concerns on this invention 1 is a block diagram showing an example of a pulse control circuit according to the present invention. Timing chart explaining relation between input signal (first pulse signal) and output (second pulse signal) of pulse control circuit according to the present invention The graph explaining the period diffusion effect by the pulse control circuit according to the present invention

Explanation of symbols

3 Pulse control circuit P 1st pulse signal CP 2nd pulse signal 31 Measurement part 33 Pulse output part

Claims (5)

A pulse control circuit that outputs a second pulse signal to the actuator drive circuit based on the pulse width modulated first pulse signal,
A measurement unit for measuring waveform information including at least a duty ratio of the input first pulse signal;
A pulse output unit that outputs the second pulse signal by changing the period of the first pulse signal while maintaining the duty ratio;
A pulse control circuit comprising: A random number generation unit, and a diffusion period setting unit that determines a diffusion period that is a period of the second pulse signal based on the random number generated by the random number generation unit,
The pulse control circuit according to claim 1, wherein the pulse output unit outputs the second pulse signal based on the diffusion period and the waveform information.   The pulse control circuit according to claim 2, wherein the measurement unit includes a waveform information holding unit that holds the measured waveform information.   An abnormality processing unit for detecting interruption of the first pulse and instructing to generate an interpolation pulse in the interrupted period, the pulse output unit, according to an instruction from the abnormality processing unit, The pulse control circuit according to claim 3, wherein the second pulse signal is output based on waveform information.   An abnormality processing unit that detects an abnormality detection signal that is input and instructs the output stop of the second pulse in accordance with the detected abnormality, and the pulse output unit is configured to respond to an instruction from the abnormality processing unit. The pulse control circuit according to claim 1 or 2, wherein the output of two pulses is stopped.

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