JPS6260306A - Pwm drive circuit - Google Patents

Abstract

PURPOSE:To attain the required dynamic range by using a PWM signal driving a load with a higher gain at a low input drive and a lower power voltage while applying a duty ratio having a longer on-period. CONSTITUTION:An analog input signal fed to an input terminal IN is fed to a variable gain circuit 11 such as an attenuator and fed to an input voltage level detection circuit 12. A gain in response to the level is given and fed to a PWM modulation circuit 14. The PWM signal is subjected to power amplification by a PWM-BTL (balanced transless) driver 16 to drive a load 17. When the level of an analog input signal is more lower, the gain is increased more, that is, the attenuation is decreased and the power voltage is lowered so as to lower the peak value of the PWM signal at that time. Thus, the duty ratio having a longer ON period is given as the PWM signal equivalently. As a result, the efficiency driving the load is improved.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention is directed to a Taki Dry! Regarding circuits.

[Technical background of the invention and its problems]

As is well known, a CD player includes various drive units such as a focus/tracking actuator, a vi, qua, push motor, and a disc motor. As a drive circuit for driving these various drive units, a PWM (/arm width variation v!4) drive circuit is generally used.

By the way, when a waterfall drive circuit drives a load such as the various drive units described above, the effective voltage of the drive waveform is only the DC component of the PWM signal, and all other harmonic components become invalid voltages. The longer the on period of the PWM signal is, the greater the above-mentioned effective voltage becomes, and therefore the efficiency of conversion from electric power to kinetic energy becomes higher.

FIGS. 4(a) and 4(b) show two types of open signals having the same effective voltage but different peak values. That is, since (,) contains more harmonic components than (b) and also has a shorter on period, the efficiency of moving the load becomes worse.

However, in general drive circuits, since the peak voltage of the image signal is set to the clip level determined by the power supply voltage value used, it is inevitable to drive the load where the duty ratio of the wM signal is small, or where the peak period is short. Therefore, as mentioned above, there was a problem in that the efficiency of moving the load deteriorated.

In other words, the reason for this is that in order to ensure the dynamic range of the drive circuit, the power supply voltage used is not so necessary during normal driving, but it is increased to a considerably high value in consideration of driving under special conditions. This is because it has been selected. This poses a problem in that power usage efficiency deteriorates and power consumption increases.

[Summary of the invention]

That is, the groove drive circuit according to the present invention includes a first means for converting an analog input signal into a groove signal, a second means for power amplifying the image signal produced by the first means, and a first means for converting an analog input signal into a groove signal. The PWM after conversion is used to distinguish and detect the level of the previous analog input signal into multiple levels.
a third means for detecting the duty ratio of the signal by discriminating it into a plurality of ranges; and a power supply voltage value to be supplied to the second means according to the detection output by the third means, which is determined by the first means. fourth means for switching and controlling the duty ratio of the signal in a direction in which the always-on period becomes longer; The present invention is characterized by comprising a fifth means for variable control in a direction to compensate for the gain change caused by the switching K of the power supply voltage by the means of 4. The purpose of this invention is to provide an extremely good PWM German circuit which is improved so as to be able to drive a load with high efficiency and ensure the necessary dynamic range.

[Embodiments of the invention]

An embodiment of the present invention will be described in detail below with reference to the drawings.

That is, an analog input signal applied to an input terminal (IN) is supplied to a variable gain circuit 1 such as an attenuator, and is also supplied to an input voltage level detection circuit 12. This input voltage level detection circuit 12 sequentially increases the level of the analog input signal from level L1 to level L2.
... Ln is level-discriminated and detected, and its detection output is supplied to the variable gain circuit 11 for variable control of its gain, and is also supplied to the power selector switch s'w1.
is supplied to switch and control its position.

Here, each position of the power supply selector switch SW1 has a voltage v1. Power supplies 131, 132", . . . , 13n capable of supplying voltages v2, . . . , vn are connected.

Then, the analog input signal is given a gain according to the level at that time by the variable gain circuit 11 based on the detection output from the input voltage level detection circuit 12.
The signal is supplied to the modulation circuit 14. This groove conversion circuit 14 compares the gain-controlled analog input signal with a reference voltage triangular wave (including nine sawtooth waves) from a reference voltage triangular wave generation circuit 15 and converts it into an image signal. This PWM signal is power amplified by a PWM-BTL (balanced transformerless) driver 16 and provided to drive a load 17 .

By the way, in this case, the PWM-BTL driver 16
As shown in FIG. 2, from the power supplies 131', 13□゛...13n whose switching is controlled by the power supply changeover switch sw1 as described above, voltages v1, Any one of v2...vn is supplied as a drive power supply voltage.

As a result, the PWM-BTL driver 16 drives the load 17 with the signal M whose peak value is the level determined by the power supply voltage corresponding to the analog input signal level at that time. This means that no matter what the level of the analog input signal is, the image signal that drives the load 17 will be used as if its duty ratio is long on period. This means that driving efficiency is improved.

Specifically, when the level of the analog input signal is low, the gain is increased, i.e., the tenate amount is decreased, and the power supply voltage is lowered to reduce the peak value of the image signal at that time. This is because the image signal at that time is made to have a long on-period due to constraints such as lowering the value. Note that as the level of the analog input signal increases, the power supply voltage is increased, but at this time, the gain is decreased by the amount of the level, that is, the amount of attenuation is increased, and the change in the gain of the entire system due to fluctuations in the power supply voltage is is compensated for.

FIG. 3 shows another embodiment, and the same components as in FIG. 1 are given the same reference numerals and their explanations are omitted. The rear part of the liquor converting circuit 14 is configured to control the variable gain circuit 11 and the power changeover switch SW1 with the output of the nine PWM duty ratio detection circuit 18. In this case, the range D, -T ratio detection circuit 18 uses power supplies 131, 132, . . . 13 corresponding to the operating range of the duty ratio to be detected.
It is assumed that the power source selector switch sw1 is controlled to select rs and, at the same time, the gain of the variable gain circuit 1 is controlled.

Further, in the embodiment shown in FIG. 3, the variable gain circuit 11 and the power source selector switch SW1 can be controlled by the outputs of the detection circuits Z 91', 192, . . . in a state specific to the equipment used. Here, the above-mentioned detection circuit 191
．． I, 192. For example, if the device used is C
In the case of the D7' layer, the following states can be detected.

■ When it becomes necessary to expand the dynamic range of the driver that drives each load during a search.

■ When it becomes necessary to expand the driver's dynamic range due to vibration.

■ When operating the pickup feed motor or disc motor at high speed.

■ When the CLV servo RAM is about to overflow or underflow (when it becomes necessary to expand the dynamic range of the disk motor driver).

According to the Taki drive circuit described above, by operating with a high gain and a low power supply voltage during normal low input driving, the image signal that drives the load can be used at a duty ratio with a long on period. As a result, it is possible to improve the efficiency of driving the load, improve the power supply utilization rate, and reduce power consumption.

Moreover, in preparation for special driving situations such as when a large input is required, the necessary dynamics can be secured by operating the power supply voltage at a high voltage and the gain at a low level.
When applied to a router, in addition to the above-mentioned advantages, the present invention is very convenient as it enables reliable search and playback operations.

It goes without saying that the present invention is not limited to the embodiments described above and illustrated, and that various modifications and applications can be made without departing from the gist of the invention.

〔Effect of the invention〕

Therefore, as detailed above, according to the present invention, it is possible to provide an extremely good liner circuit that is improved so as to be able to drive a load with high efficiency and ensure the necessary dynamic range. .

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing one embodiment of the field drive circuit according to the present invention, FIG. 2 is a waveform diagram for explaining the operation of FIG. 1, and FIG. 3 is a configuration diagram showing another embodiment. Figure 4(a)
# (b) is a waveform diagram for explaining load drive efficiency by PWM signal. IN...analog signal input terminal;
11... Variable gain circuit (attenuator), 12...
・Input voltage level detection circuit, swl...power supply changeover switch, 131.1.92...13n...power supply, 14
... Waterfall conversion circuit, 15 ... Triangular wave generation circuit for reference voltage, 16 ... PWM-BTL driver, 17 ...
Load, 18...Takide, -T ratio detection circuit. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] a first means for converting an analog input signal into a PWM signal; and a second means for power amplifying the PWM signal produced by the first means.
and third means for detecting the level of the analog input signal before conversion by the first means by distinguishing it into a plurality of levels, or by discriminating and detecting the duty ratio of the PWM signal after conversion into a plurality of ranges. and a fourth means for switching and controlling the power supply voltage value supplied to the second means in accordance with the detection output by the third means in a direction in which the duty ratio of the PWM signal by the first means becomes longer at all times. and the means of
a fifth means for variably controlling the gain of the analog input signal before conversion by the first means in accordance with the detection output by the third means in a direction that compensates for a gain change caused by switching the power supply voltage by the fourth means; A PWM drive circuit characterized by comprising: means.