JPS6113973Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pulse width modulation type potentiometer, particularly to improving resolution in a pulse width modulation type potentiometer.

As shown in the principle diagram in FIG. 1, the pulse width modulation type potentiometer varies the application time of the input voltage E applied to the integrating circuit 1 within one period by the switching element 2.
By varying the width of the pulse-like input of the voltage E input to the integrator circuit 1, a smoothed output proportional to the duty ratio within one cycle of the pulse-like input is obtained from the integrating circuit 1. In FIG. 1, for example, one cycle of the switching element 2 is T time, and the contact 2a
mT time (0≦m≦1) on the side, and (1
-m) When connected for T time, a smoothed output expressed by Eo=mE is generated between output terminals 3-3'.

FIG. 2 is a circuit diagram of a pulse _width modulation type potentiometer that is a generalized version of _FIG . time not to
T ₁ to T _o are connected to input voltages E ₁ to _{E o} . Therefore, a smoothed output expressed by the following equation (1) is obtained from the integrating circuit 1.

Here, Ti is T ₁ to T _o and Ei is E ₁ to _{E o} .

In this way, conventional pulse width modulation type potentiometers digitally vary the time width of the input voltage applied to the integrating circuit using a switching element to obtain a smoothed output proportional to the duty ratio in one cycle. It has become popular in recent years because the circuit configuration is simple and it can be constructed using non-precision parts.

However, as can be seen from the above description, since the duty ratio of the input voltage applied to the integrating circuit 1 is digitally varied, high resolution, that is, minimum variable step of the output Eo, and high speed response are not compatible.

In other words, the response speed of the output Eo is determined by the time constant C and R of the integrating circuit 1, and in order to increase the response speed, it is necessary to reduce the time constant C and R. On the other hand, the ripple content of the output Eo is determined by the pulse It is determined by the ratio of the cycle time T of the state input and the time constant C・R,
In order to reduce the ripple content, T≪C・R
It must be. Therefore, in order to make the ripple content sufficiently small, the response speed fast, and the resolution high, the time width of the input voltage within one cycle should be made sufficiently short, and the time constant C/R of the integrating circuit should be made sufficiently small. There is a need. However, if the time width of the input voltage is made sufficiently short, an error will occur in the response speed of the switching element, resulting in a loss of output accuracy.

Therefore, an object of the present invention is to provide a pulse width modulation type potentiometer that has a sufficiently fast response speed, high accuracy, and high resolution without shortening the time width of the input voltage.

To achieve this purpose, the pulse width modulation type potentiometer according to the present invention uses the input voltage for a part of time _T1 of one period T, and for the other part of time _T2 that does not overlap, the input voltage The remaining time T ₃ (T ₃ =T−T ₁ −
_T2 ) is composed of switch means that repeats the operation of respectively connecting the input voltage to the reference potential, and an integrating circuit connected to a common output point of the switch means,
The settings of the times T ₁ , T ₂ and T ₃ are adjusted digitally, and the voltage division ratio is adjusted analogously, so that the output voltage is obtained from the output terminal of the integrating circuit.

EMBODIMENT OF THE INVENTION Hereinafter, the pulse width modulation type potentiometer according to the present invention will be explained in detail using embodiments shown in the drawings.

FIG. 4 is a circuit diagram showing an embodiment of the pulse width modulation type potentiometer according to the present invention, and the same parts as in FIG. 1 are given the same symbols. In the figure, a switching element _S1 repeats an operation of connecting to an input voltage E for a part of time _T1 of one period T;
A switching element _S2 repeats the operation of connecting the input voltage E to a constant voltage divided by a variable resistor VR having a resolution of 1/L for another time _T2 that does not overlap with the time _T1 ; Remaining time of period T
It consists of a switching element _S3 that repeats the operation of connecting to the reference potential of the input voltage E by T3, and an integrating circuit 1 connected to a common output point _of these switching elements _S1 to _S3 .

In the pulse width modulation type potentiometer configured in this way, each switching element S ₁ , S ₂ ,
In the switching control of _S3 , each timing is controlled by a control signal obtained by counting clock pulses of a predetermined frequency, and this switching control circuit is constructed as shown in FIG. 7, for example. That is, the clock pulse Cp of a predetermined frequency generated from the oscillator 4 is counted by the counter 5, the output of this counter 5 is decoded by the decoder 6, and then the decoded output of the required timing is selected from among the outputs of the decoder 6. Select with switch 7 to input to flip-flops FF ₁ to _{FF 3} , and output from flip-flops FF ₁ to _{FF 3} to switching elements S ₁ to FF 3.
It is given as a control signal for _S3 . As _shown in _the time chart _{of FIG .
T2} hours and _S3 are controlled to be turned on during one period T for _T3 hours.

Therefore, the output Eo obtained at the output end 3-3' of the pulse width modulation type potentiometer shown in FIG. 4 as an embodiment of the present invention can be determined by substituting a specific value into equation (1). It is expressed by the following equation (2).

Eo=ET ₁ +αE・T ₂ +O・T ₃ /T ₁ +T ₂ +T
₃ =T ₁ +αT ₂ /T ₁ +T ₂ +T ₃ ×E (2) Here, α is the division ratio of the variable resistor VR.

This will be explained using a specific example. For example, if one period T is set to the time equivalent to 100 clock pulses Cp of one period τ, then one period T is T = T ₁ + T ₂ + T ₃ = 100τ, and the time T ₂ = τ, T ₁ =Mτ(M: Any setting value, and in this example, the variable range of M is 0≦M
≦100. ), the above equation (2) becomes as follows.

Eo=M+α/100×E...(3) Therefore, if the resolution 1/L of the variable resistor VR is set to 1/100, which does not require precision, then the variable range of the division ratio α is 1/100≦ α≦1, and as a result, the output Eo is Eo=□□. □□/100×E ……(4) Thus, it is possible to obtain an output Eo with a resolution of 4 digits. In this case, the variable resistor VR
Since the division ratio α is weighted to 1/100, precision is not required. To generalize the above, in a design with maximum resolution, if N clock pulses Cp are counted as one period, and the divided output αE of the variable resistor VR is assigned to one clock pulse Cp. The resolution, that is, the minimum variable step of the output Eo is 1/N×1/L because it depends on how much αE can be taken within one cycle, with αE as the minimum variable step. In this case, the main setting value M (value for varying the time _T1 ) can be varied from 0 to N. That is, when M=N, the switching element _S1 in FIG. 4 is always on, the others are always off, and the output Eo becomes Eo=E. Further, when the main setting value M is M≦N-1, there is always a time T ₂ in which the switching element S ₂ is turned on, so the resolution is 1/N×1/L.

Note that the above is a case where the time T ₂ is set as one clock pulse Cp, but T ₁
Of course, various time T ₂ can be set within the range +T ₂ ≦T.

Also, the on time of switching elements S ₁ , S ₂ , S ₃
There is no theoretical need for T ₁ , T ₂ , and T ₃ to be continuous for a certain period of time as shown in the time chart of FIG. 5, but as shown in the time chart of _FIG . T ₂ and T ₃ may be intermittent.

As described above, according to this embodiment, by combining only a variable resistor with a resolution of 1/L with the conventional pulse width modulation potentiometer with a resolution of 1/N, high-resolution 1/N. A 1/L pulse width modulation potentiometer can be obtained. Moreover, since high resolution can be obtained without increasing the switching speed of the switching element, the response speed can be increased by adjusting the time constant of the integrating circuit.
A highly accurate pulse width modulation type potentiometer can be provided.

8 and 9 are circuit diagrams showing other embodiments of the pulse width modulation type potentiometer according to the present invention, and FIG. 8 is a circuit diagram showing a buffer circuit A in the input and output stages of the circuit shown in FIG. ₁ and _A2 are connected, and in FIG. 9, a buffer circuit _A3 is also connected to the divided voltage output side of the variable resistor VR. By doing so, it is possible to reduce mutual interference of voltages inputted to the outside and to the switching elements S ₁ and S ₂ , and a reliable pulse width modulation type potentiometer can be provided.

In the embodiment described above, in order to obtain a reverse output, it can be easily realized by configuring the integrating circuit 1 as shown in FIG.

Furthermore, although the integrating circuit 1 is constructed with one CR each, it goes without saying that it may be constructed with a plurality of CRs as shown in FIG.

As explained above, according to the present invention, by combining only a variable resistor with a resolution of 1/L with a conventional pulse width modulation potentiometer with a resolution of 1/N, it is possible to easily achieve high resolution of 1/N. - A 1/L pulse width modulation potentiometer can be obtained. Moreover, in the case of the present invention, high resolution can be achieved without increasing the switching speed of the switching element, so it is possible to achieve both high-speed response and high resolution, and it is possible to adjust the time constant of the integrating circuit. As a result, it is possible to obtain a pulse width modulation type potentiometer with a sufficiently fast response speed and high precision, which is extremely effective in practice.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram for explaining the principle of a pulse width modulation type potentiometer, Figure 2 is a generalized circuit diagram of Figure 1, and Figure 3 is a circuit diagram of the pulse width modulation type potentiometer shown in Figure 2. FIG. 4 is a circuit diagram showing an embodiment of the pulse width modulation type potentiometer according to the present invention, and FIGS. 5 and 6 show the pulse width modulation type potentiometer of FIG. 4. Time chart to explain the operation of
FIG. 7 is a circuit diagram showing an example of a switching control circuit that performs switching control of a switching element, and FIGS. 8 and 9 are circuit diagrams showing other embodiments of the pulse width modulation type potentiometer according to the present invention. 10 and 11 are circuit diagrams showing other examples of the integrating circuit used in the present invention. 1...Integrator circuit, 2, S ₁ to _{S o} ... Switching element, 3, 3'... Output terminal, 4... Oscillator,
5...Counter, 6...Decoder, 7...Selection switch, _A1 , _A2 , _A3 ...Buffer circuit.

Claims (1)

[Scope of utility model registration request] A part of time T ₁ of one period T is applied to the input voltage, another part of time T ₂ that does not overlap is applied to a constant voltage obtained by dividing the input voltage, and the remaining time T ₃ of one period T (T ₃ =
T-T ₁ -T ₂ ) has switch means for repeating the operation of respectively connecting the input voltages to the reference potential, and an integrating circuit connected to _a common output point of the switch means, and ₂ and _T3 settings are adjusted digitally, the voltage division ratio is adjusted analogously, and the output voltage is obtained from the output terminal of the integration circuit using a pulse width modulation type potentiometer.