JPH03216803A - Current detecting circuit for current driving circuit - Google Patents

Abstract

PURPOSE:To surely as well as exactly judge whether a prescribed current flows or not by providing a voltage detecting part which detects the transient and quick change of the output voltage of a voltage amplifying circuit due to the start of flow of the prescribed current to a load. CONSTITUTION:A current detecting circuit 9 is provided with a comparator (voltage detector ) 4 which detects an output voltage V0 of a voltage amplifying circuit 1, a positive-polarity reference voltage applying means 5 which applies a positive-polarity reference voltage VT-POS to this comparator, a negative- polarity reference voltage applying means 6 which applies a negative-polarity reference voltage VT-NEG, and a D type latch circuit 7. Consequently, the tran sient output voltage change of the voltage amplifying circuit due to the start of flow of the prescribed current to the load is detected to detect the start of flow of the prescribed current to the load by detecting the transient change of the output voltage. Thus, it is surely as well as exactly judged whether the prescribed current flows or not.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a current detection system that is provided in a current drive circuit for causing a predetermined current to flow through a load and detects that a predetermined current has started flowing through the load. It relates to circuits and is used, for example, to drive control of a magnetic field generation circuit installed in a magneto-optical disk system.

[Conventional technology]

A magneto-optical disk system is equipped with a magnetic field generation circuit for applying a magnetic field involved in recording and erasing information to a magneto-optical disk. The magnetic field generation circuit is equipped with a coil for generating a magnetic field, and this coil generates a magnetic field in a desired direction using a current from the current drive circuit.

As shown in FIG. 3, the above current drive circuit includes a voltage amplification circuit 1 including an arithmetic circuit 1a, a coil 2 serving as a load (resistance value R2), and a current sense resistor 3 (resistance value R2) for detecting current.
resistance value R3). Coil 2 above
and current sense resistor 3 are connected in series. Also,
A return line 1b is connected so that the current passing through the coil 2 is fed back to the voltage amplification circuit l, and due to this current feedback, a current proportional to the input voltage vi (Vi/R3) {
The current flows to coil 2.

By the way, the coil 2, which is a load, has self-inductance, so that when the power supply voltage circuit starts up and when the current direction is switched, the current flowing through the coil 2 reaches the input voltage V. A slight but constant delay t time 11 is required until the current reaches a ratio compared to . Therefore, in order to reliably record and erase information caused by the coil magnetic field 6, it is necessary to judge whether or not the necessary magnetic field has been generated during immersion. It is an important element in doing so.

There are three typical conventional methods for making the above judgments:
Two methods are known.

■Set a certain waiting time based on empirical or calculated values.

■Detect and judge the generated magnetic field using sensors such as Hall elements.

■Detect and judge the current actually flowing through the coil 2.

The above method (■) can be executed only by software processing and does not require hardware, so it is possible to make the above judgment with a simple configuration, but the delay time changes due to fluctuations in power supply voltage, etc. Therefore, it is necessary to set a waiting time with sufficient margin, which has the disadvantage that speeding up of recording and erasing is hindered.

In addition, the above method (2) requires a sensor such as a Hall element, which has the drawback of making the circuit expensive.

For this reason, the method (2) above is generally adopted. As shown in FIG. 4, a circuit that implements this method, that is, a current detection circuit of a conventional current drive circuit, detects a voltage V at point a.
, a positive reference voltage applying means 5 for applying a positive reference voltage (Vy-pos) to the comparator 4, and a negative reference voltage applying means 5 for applying a negative reference voltage (V7-nta) to the comparator 4. 1,000 reference voltage application stages 6. The two reference voltage applying means 5 and 6 are provided to correspond to the direction of current flow.

In such a current detection circuit, as shown in FIG. 5(a), for example, the above-mentioned V. By setting , somewhat lower than vi, as shown in (c) of the same figure, ■,
The logic signal S of the comparator 4 rises at the time when . Based on this logic signal Sl, it is determined whether a predetermined current flows through the coil 2 or not. Note that the logic signal S2 shown in (b) of the same figure is the ON-O signal of the current drive circuit.
FF signal (“HIGIN” when ON, “i’” when OFF
The time from the rise of the signal S2 to the rise of the signal SL is approximately equal to the delay time t1 described above.

[Problem to be solved by the invention]

However, in the current detection circuit of the conventional current drive circuit, vt-p. If the difference between 3 and V, is too small, ■
, the fluctuation of V? -P. , a situation arises in which voltage comparison by the comparator 4 becomes impossible. Therefore,
If we want to reliably determine whether a predetermined current has flowed through coil 2, then V T-PG! The difference between and ■ must be made as large as possible. However, if this difference is made too large, the rise of the logic signal St will be accelerated, and it will be determined that the prescribed current is flowing through the coil 2 even though it is not, resulting in inaccurate judgments. Become.

In other words, it is extremely difficult to achieve both reliability and accuracy in determining whether or not a predetermined current has flowed.

[Means for Solving the Problems] In order to solve the above problems, a current detection circuit of a current drive circuit according to the present invention applies an output voltage from a voltage amplification circuit including an arithmetic circuit to a load, and also applies a current to a load. In a current detection circuit that is included in a current drive circuit that supplies a predetermined current to a load by performing feedback and detects that a predetermined current has started flowing to the load, the current flowing to the load is equal to the predetermined current. When the delay time until L becomes L, and the rise time of the output voltage of the voltage amplifier circuit is also 2,
A voltage detection unit is provided that detects a transient and steep fluctuation in the output voltage of the voltage amplification circuit caused by a predetermined current flowing through the load within a range where t1>t2 holds. It is characterized by the presence of

(Function) According to the above configuration, since the output voltage fluctuation of the voltage amplifier circuit that occurs transiently due to the start of a predetermined current flowing through the load is detected, this transient output voltage fluctuation is detected. It is possible to detect that a predetermined current has started flowing through the load.

Since the above output voltage shows a steep change,
As long as it is within the range that shows this steep change, no matter where the reference level for voltage fluctuation determination is set, accurate determination results can be obtained without any change. In other words, it is not necessary to make the reference level as close as possible to a certain level in order to ensure the accuracy of the judgment, and it is not necessary to make the reference level as close as possible to a certain level in order to ensure the reliability and accuracy of the judgment as to whether or not a predetermined current has flowed. It is possible to achieve both.

〔Example〕

An embodiment of the present invention will be described below based on FIGS. 1 and 2. For convenience of explanation, the same reference numerals are added to the same elements as those shown in the conventional example.

As shown in FIG.
2), and a current sense resistor 3 (resistance value R3) for detecting current. The above coil 2 and current sense resistor 3 are connected in series. Further, a feedback line 1b is connected so that the current passing through the coil 2 is fed back to the voltage amplification circuit l, and this current feedback causes the input voltage . A current (V4/Ra) proportional to is caused to flow through the coil 2.

The current detection circuit 9 includes a comparator (voltage detection unit) 4 that detects the output voltage o of the voltage amplifier circuit 1, and a positive reference voltage that applies a positive reference voltage (VT-POS) to the comparator 4. 1,000 steps of application, negative polarity reference voltage (V r-NE
r. ), and a D-type latch circuit 7. The two reference voltage application stages 5 and 6 are provided to correspond to the direction of current flow. D type latch circuit 7
The logic signal S from the comparator 4 is input to the CK terminal of the circuit, and the logic signal S2 indicating ON/OFF of the current drive circuit is input to the CL terminal. There is. A "HIGH" signal is always manually input to the D terminal. Also, a logic signal S3 is output from the Q terminal.

As shown in FIG. 2(d), the logic signal S2 takes a "HIGH" state when the current drive circuit is turned on, and takes a "LOW" state when it is turned off. and,
As shown in (b) of the figure, the voltage at point a reaches voltage ■ after a delay time tl when the current drive circuit is turned on, and when the current drive circuit is turned off, it enters a transient state. After that, he becomes Ov.

Here, since the voltage amplification circuit 1 including the arithmetic circuit 1a drives the coil 2 by current feedback, the voltage gain is very large, and the current flowing through the coil 2 reaches a steady value and the arithmetic result becomes a value close to 0. Until (corresponding to the above time tl), the output voltage of the voltage amplifier circuit 1 is ■. indicates a transient fluctuation. That is, as shown in (a) of the figure, the output voltage is ■. The rise time L2 is the above time 1,
When the output voltage V is smaller than , the output voltage V is smaller than V due to the fact that no current feedback is applied immediately after the current drive circuit starts up. reaches its maximum amplitude at rise time t2, after which coil 2
A current gradually begins to flow, and the voltage gradually decreases depending on the circuit capacity of the voltage amplifier circuit 10. And time t
When a predetermined current begins to flow through the coil 2 after l, current feedback is applied and the output voltage is V. is a steep and steady value (VD, I
v).

Comparator 4 outputs the above output voltage ■. is input, and the positive polarity reference voltage (Vt-p) from the positive polarity reference voltage applying means 5 is inputted.
. ) or the negative reference voltage (VT-NEC) from the negative reference voltage applying means 6 and the output voltage V. A logic signal SI is output. The signal SI has an output voltage ■, as shown in (c) of the same figure. ``LOW'' is output while VT-POS is higher than VT-NEC or VT-NEC is lower than VT-NEC.

The logic signal S1 is input to the CK terminal of the D-type latch circuit 7, and the logic signal S3 is output from the Q terminal of the D-type latch circuit 7 due to this input. The signal S3 rises in synchronization with the rise of the signal S1 in the "HIGH'" state of the signal S2. That is, as shown in (e) of the same figure, the output voltage V0 reaches the steady value (Vo++
v) and the specified current begins to flow through the coil 2, it becomes "'}flGH", and this "HIGH" state is changed to "L" when the current drive circuit is turned off.
The signal becomes "LOW" and is maintained until this "LOW" is input to the CL terminal and the D-type latch circuit 7 is cleared.

Therefore, from the signal S3, it is possible to detect that the predetermined current has started to flow through the coil 2 and that the drive current has been turned off and the predetermined current has stopped flowing.

Here, as mentioned above, since the fluctuation of the output voltage v0 shows a steep change due to the predetermined current starting to flow through the coil 2, within the range showing the steep change, If there is, no matter where the reference level for voltage fluctuation determination is set, accurate determination results will be obtained without any change. That is, as shown in FIG. 2, for example, the positive polarity reference voltage V? -POS, the highest reference voltage VT-F. S-
H ■ and the lowest reference voltage V TP. , , 1N, there is no change in the rise of the signal S3, and an accurate signal can be obtained.

Therefore, it is no longer necessary to bring the reference level as close as possible to a certain level in order to ensure the accuracy of the determination, so it is possible to achieve both reliability and accuracy in determining whether or not a predetermined current has flowed. can be done.

Note that the output voltage of the voltage amplification circuit l is ■. The drive current O
A high voltage of negative polarity is generated due to the back electromotive force of the coil 2 due to the FF. Therefore, V by the negative polarity reference voltage applying means 6
? -Comparing with NEG, there is a rise timing in the signal S, but at this timing,
Since the signal S2 is "LOW", the signal S3 is not latched.Also, the above explanation has been made for the case where the input voltage 8 is of positive polarity, but when the input voltage 8 is of negative polarity, the output voltage 8 is of negative polarity.
Only the polarities of o and ■ are reversed, and the same current detection as described above is possible.

〔Effect of the invention〕

As described above, in the current detection circuit of the current drive circuit according to the present invention, when the delay time until the current flowing through the load reaches a predetermined current is t1, and the rise time of the output voltage of the voltage amplifier circuit is t2. , t+>tz, which detects a transient and steep fluctuation in the output voltage of the voltage amplification circuit caused by a predetermined current starting to flow through the load. The configuration is as follows.

As a result, regarding the determination of whether or not a predetermined current has flowed,
This has the effect of achieving both reliability and accuracy.

[Brief explanation of drawings]

1 and 2 show one embodiment of the present invention. FIG. 1 is a circuit diagram of a current detection circuit of a current drive circuit. FIG. 2 is a time chart showing the correlation between the output voltage of the voltage amplifier circuit and the logic signal from the comparator. FIG. 3 is a circuit diagram of the current drive circuit. FIGS. 4 and 5 show conventional examples. FIG. 4 is a circuit diagram of the current detection circuit of the current drive circuit. FIG. 5 is a time chart showing the correlation between the voltage after the voltage drop due to the load and the logic signal from the comparator. 1 is a voltage amplifier circuit, 1a is an arithmetic circuit, 2 is a coil (load), 3 is a current sense resistor, 4 is a comparator, 5 is a positive polarity reference voltage application means, 6 is a negative polarity reference voltage application means, 7 is D 9 is a type launch circuit, and 9 is a current detection circuit.

Claims (1)

[Claims] 1. A current drive circuit is provided that supplies a predetermined current to the load by applying an output voltage from a voltage amplification circuit including an arithmetic circuit to the load and performing current feedback, so that the predetermined current flows through the load. In the current detection circuit that detects when the current has started, when the delay time until the current flowing through the load reaches a predetermined current is t_1, and the rise time of the output voltage of the voltage amplification circuit is t_2, t_1>t_
A voltage detection unit is provided that detects a transient and steep fluctuation in the output voltage of the voltage amplification circuit caused by a predetermined current starting to flow in the load within a range where 2 is satisfied. A current detection circuit for a current drive circuit characterized by: