JP2828521B2 - Inductive load current controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inductive load current controller for intermittently exciting an inductive load.

[0002]

2. Description of the Related Art FIG. 3 shows a circuit configuration of a conventional inductive load current control device. Reference numeral 1 denotes a DC power supply whose (-) pole is grounded, 2 denotes an inductive load having one end connected to the (+) pole side of the DC power supply 1, and 3 denotes a collector whose other end of the inductive load 2 is an input terminal. A transistor as a first switch,
Reference numeral 4 denotes a current detection resistor as a current detector connected between the emitter serving as the output terminal of the transistor 3 and the ground.

[0005] 5 is a transistor as a second switch,
Reference numeral 6 denotes a flywheel diode which is connected in series and connected in parallel to the inductive load 2. Reference numeral 7 denotes a Zener diode provided between the collector of the transistor 3 and the ground for absorbing a surge voltage applied to the collector, 10 a reference voltage, and 11 a comparator for comparing the voltage of the current detection resistor 4 with the reference voltage 10. .

[0004] Reference numeral 12 denotes a logical product of a command signal for commanding start / stop of the device (current), an output of the comparator 11, and an output of a monostable flip-flop (hereinafter referred to as a monostable FF) 15 described later. In the circuit, the output is supplied to the transistor 3 via the base resistor 13 and the monostable FF 1
5 input. An inverter circuit 16 inverts the command signal and supplies the inverted signal to the transistor 5 via the base resistor 17.

FIG. 4 is a waveform diagram of signals of various parts of the current control device for an inductive load having the above-described configuration. S 1 is a command signal, S 2 is a signal of a part which is an output part of the AND circuit 12, and S 3 is a transistor 3 A current signal, S4 is a signal of the b portion of the output section of the inverter circuit 16, S5 is a current signal of the transistor 5, and S6 is a current signal of the inductive load 2.

Next, the operation will be described. When the command signal is at the “L” level (hereinafter, referred to as “L”), the output of the AND circuit 12 is “L” and the transistor 3 is in the OFF state. At this time, the output of the inverter circuit 16 is at the "H" level (hereinafter, referred to as "H"), and the transistor 5 is also in the OFF state. In this state, since no current flows through the current detection resistor 4, the output of the comparator 11 is "H" and the output of the monostable FF 15 is also "H" on the stable side.

Next, when the command signal becomes "H", the output of the AND circuit 12 becomes "H" and the transistor 3 is turned on. Thereby, the (+) pole side of the DC power supply 1 → inductive load 2 → transistor 3 → DC detection resistor 4 → DC power supply 1
Current starts to flow through the first circuit of the (−) pole side loop of
It rises at a value determined by the inductance, resistance and power supply voltage of the first circuit.

Since the voltage applied to the current detection resistor 4 during the rise of the current becomes higher than the reference voltage 10, the output of the comparator 11 becomes "L" and the output of the AND circuit 12 also becomes "L". Therefore, the transistor 3 is turned off.
As a result, the current to the current detection resistor 4 becomes 0 and the output of the comparator 11 returns to “H”. However, the output of the monostable FF 15 becomes “L” for a certain time t _OFF due to the fall of the output of the AND circuit 12. Become. Therefore, during this “L” period, the output of the AND circuit 12 is still “L”, so that the transistor 3
Is turned off.

On the other hand, when the command signal is "H", the output of the inverter circuit 16 becomes "L" and the transistor 3 is turned off because the transistor 5 is turned on.
, The current flowing through the inductive load 2 becomes
→ Transistor 5 → Flywheel diode 6 → Flow through the second circuit of the inductive load 2 loop. Eventually, when a certain time t _OFF during which the monostable FF 15 outputs “L” elapses, the output of the AND circuit 12 becomes “H”, the transistor 3 turns on, and a current flows in the first circuit.

As shown in FIG. 4, by repeating the above operation when the command signal S1 is "H", current flows intermittently through the first circuit (current signal S3 of the transistor 3).
Conversely, a current also flows intermittently in the second circuit (a current signal S5 of the transistor 5), and the current S6 flowing through the inductive load 2 is controlled to be substantially constant.

The flywheel diode 6 provided in the second circuit includes a transistor 3 and a transistor 5
This is to prevent an excessive current from flowing through the path of DC power supply 1 → transistor 5 → transistor 3 → current detection resistor 4 even when the power supply is turned on at the same time.

[0012]

The conventional inductive load current control device is constructed as described above.
When the circuit operates, the voltage drop due to the flywheel diode 6 is large, and the power consumption in this portion is large and heat is released.

If the power consumption by the flywheel diode 6 is large, the current drop during the current flowing in the second circuit is large, and the ripple rate of the current signal flowing to the inductive load 2 is large. When the induction load 2 is a solenoid, there is a problem that it cannot be brought into a stable operation state.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and eliminates the need for a flywheel diode, thereby solving the problem of heat generation and stably supplying a current to an inductive load. It is an object of the present invention to obtain a current control device for an inductive load that can perform the control.

[0015]

Means for Solving the Problems] The current control device of the inductive load of the present invention includes a DC power supply, an inductive load, the first switch and the first circuit connected in series, in conjunction with the second switch A second switch forming a second circuit comprising a closed loop;
The command signal for starting and stopping the conductive load and the current detector
ON / OFF control of the first switch based on the detection signal
ON / OFF control of the first control means and the second switch
Control means for controlling the start-up finger according to the command signal.
In a current control device for an inductive load, the current control device controls the current to flow alternately through the first circuit and the second circuit at the time of command .
Circuit is such that only the second switch is connected in parallel with the inductive load.
The second control means includes a power supply of a DC power supply.
Comparator for comparing the voltage with the voltage at the input / output end of the second switch
And the second opening based on the comparison result of the comparator and the command signal.
And a logic circuit for controlling ON / OFF of the closing device.
The voltage at the input / output terminal of the second switch exceeds the power supply voltage
Only when the second switch is turned on.
Ri, startup command, the ON · OFF of the first switch is to ON · OFF controlling the second switch to reverse.

[0016]

According to the present invention, a current control device for an inductive load is
Since the closed loop is composed of only the inductive load and the second switch, the voltage drop at the time of energization is only the second switch, so that the loss is small, so the ripple rate of the current of the inductive load is small,
Also, the first and second switches are turned ON / OFF in opposite phases.
Because they are controlled, they are not turned on at the same time, so that an excessive current does not flow.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a circuit configuration of an inductive load current control device according to one embodiment of the present invention. In FIG.
13, 15, and 17, and the description thereof is omitted. However, the transistor 5 as the second switch is an inductive load 2
Are connected in parallel.

Reference numeral 18 denotes a NAND circuit which takes the product of a command signal and an output signal of a comparator 19 to be described later and outputs a result of negation.
Is the voltage at the connection point e between the power supply voltage of the DC power supply 1 and the other end of the inductive load 2 opposite to the side connected to the DC power supply 1 and the emitter of the transistor 5, ie, the input / output terminal of the transistor 5. Is a comparator for comparing the voltage of the emitter and the voltage of the collector. Components 10 to 12 and 15 constitute first control means for controlling ON / OFF of the transistor 3, and components 18 and 19 constitute second control means for controlling ON / OFF of the transistor 5. Is composed.

FIG. 2 shows the waveforms of the signals at various parts of the apparatus shown in FIG. 1. S1 is a command signal, S2 is a signal at a part which is the output of the AND circuit 12, S3 is a current signal of the transistor 3, and S7 is a signal. A signal of an output section c of the NAND circuit 18;
S5 is a current signal of the transistor 5, and S6 is a current signal of the inductive load 2.

Next, the operation of the embodiment will be described with reference to FIGS. However, a part overlapping with the operation of the conventional example described in FIG. 3 is omitted.

When the command signal is "L", the NAND circuit 1
8 is "H", the transistor 5 as the second switch is in the OFF state, and the transistor 3 as the first switch is in the OFF state as in the conventional example. No current flows through the circuit No. 1 (loop of code 1 → 2 → 3 → 4 → 1) and the second circuit (corresponding to the loop of code 2 → 5 → 2).

When the command signal becomes "H", the transistor 3 is turned on as in the conventional example, and the (+) pole of the DC power supply 1 → inductive load 2 → transistor 3 → current detecting resistor 4 → DC power supply 1 A current flows through the first circuit of the (−) pole side loop. At this time, the voltage of the portion e is the inductive load 2
Is lower than the power supply voltage of the DC power supply 1
The output of the comparator 19 comparing these voltages is "L".
Therefore, the output of the NAND circuit 18 is "H" and the transistor 5 is in the OFF state.

When the amount of current flowing through the first circuit increases and the transistor 3 is switched from the ON state to the OFF state in the same manner as in the conventional example, the voltage of the portion e is instantaneously induced by the induction load 2. It rises and becomes higher than the power supply voltage of the DC power supply 1. As a result, the output of the comparator 19 becomes "H" and the output of the NAND circuit 18 becomes "L", so that the transistor 5 is turned on, and the second load of the closed loop of the inductive load 2 → the transistor 5 → the inductive load 2 is obtained. Current flows through the circuit. The period during which the current flows at this time is a fixed time t during which the output of the monostable FF 15 is "L" as in the prior art
_OFF . Hereinafter, as described above, the current flows alternately in the repetition of the first circuit → the second circuit → the first circuit.

When a current is flowing through the second circuit,
Although a voltage drop occurs due to the transistor 5, this is not a problem because it is much smaller than that of the flywheel diode used in the conventional example. According to the present invention, since the power loss of the flywheel diode is smaller than that of the conventional example, the current drop of the second circuit during the constant OFF time of the transistor 3 is small, that is, the current reduction rate ｛ When the peak current amount of S6 is I _p and the current amount after the current drop is I _b , (I _p −I _b ) / I
_p ｝ is smaller than the conventional example (see S6 in FIG. 4).

In the above embodiment, the monostable FF 15 receives the output of the AND circuit 12 as an input.
The same effect as in the above-described embodiment can be obtained even when the output of 1 is input.

[0026]

As described above, according to the present invention , the direct current
A first circuit in which a power supply, an inductive load, and a first switch are connected in series.
Road, and a second closed loop associated with the second switch.
A second switch forming a circuit and start / stop of an inductive load
Signal and the detection signal of the current detector.
Control means for controlling ON / OFF of a first switch by using a switch
And a second control means for controlling ON / OFF of the second switch.
And a first circuit when the start command is given by the command signal.
For controlling current to flow alternately in the second circuit and the second circuit
In the load current control device, the second circuit includes a second open circuit.
The configuration consists of only a switchgear connected in parallel to the inductive load.
2 means for controlling the power supply voltage of the DC power supply and the second switch
A comparator that compares the voltage at the input / output terminals and a comparison
ON / OFF of the second switch based on the result and the command signal
And a logic circuit for controlling, when a start command is issued,
Only when the voltage at the input / output terminals of the
By controlling the ON / OFF of the switch (2), at the time of a start command,
Opposite to ON / OFF of the first switch , the second switch is set to O
The N-OFF control is adopted, so that the flywheel diode is not required, so that heat generation is reduced and the equipment can be downsized. In addition, the temperature rise in the equipment is reduced, so the reliability of other parts is reduced. This has the effect of leading to improvement.

Further, since the power loss due to the flywheel diode is reduced, the OF of the first switch is reduced.
Current decrease rate during a certain time at F 時 (I _p −I _b ) / I
_{Since p} ｝ is reduced, that is, the current ripple rate flowing through the inductive load is reduced, for example, when a solenoid is applied as the inductive load, the operation state of the solenoid is more stabilized.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of an inductive load current control device according to an embodiment of the present invention.

FIG. 2 is a signal waveform diagram of each section of the circuit in FIG.

FIG. 3 is a circuit configuration diagram of a conventional device.

FIG. 4 is a signal waveform diagram of each section of the circuit in FIG. 3;

[Explanation of symbols]

 Reference Signs List 1 DC power supply 2 Inductive load 3 Transistor (first switch) 4 Current detection resistor (current detector) 5 Transistor (second switch) 10 Reference voltage 11 Comparator 12 AND circuit 15 Monostable FF 18 NAND circuit 19 Comparator

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H02P 7/06-7/34 H01F 7/18 H02P 8/00-8/42

Claims (1)

(57) [Claims] 1. A first circuit in which a DC power supply, an inductive load, a first switch and a current detector are connected in series, and a second circuit forming a second circuit comprising a closed loop in association with the inductive load. switch and the detection signal and the first switch on the basis of a command signal for commanding start and stop of the inductive load and said current detector O
First control means for N · OFF control, and a second control means for controlling ON · OFF the second switch, upon activation command by the command signal, the first circuit and
In a current control device for an inductive load that controls current to flow alternately through the second circuit, the second circuit has a configuration in which only the second switch is connected in parallel to the inductive load , The second control means includes a power supply voltage of the DC power supply and an input / output terminal of the second switch.
And a comparator that compares the voltage of the comparator and the command signal based on the comparison result of the comparator and the command signal.
A logic circuit for controlling ON / OFF of the second switch.
Seen, the startup command, the second switch input and output of the voltage
ON control of the second switch only when the power supply voltage exceeds the power supply voltage, the second switch is turned on and off at the time of the start command, contrary to ON / OFF of the first switch. current control device of an induction load and controlling ON · OFF.