JPH02262829A - Inverter for automobile - Google Patents

Abstract

PURPOSE:To prevent usage under overcurrent state by outputting an interruption signal when the supply current level exceeds a predetermined level and sustained for a predetermined time corresponding to the supply current level and then interrupting supply current based on the interruption signal. CONSTITUTION:When the supply current level higher than a first predetermined level is sustained for a predetermined time corresponding to the supply current level, charging voltage of a capacitor 102, i.e. the voltage at one terminal 70 of an operational amplifier 62 exceeds over the voltage at + terminal 65 and thereby the voltage at the output terminal 131 of the operational amplifier 62 is brought to H level thus producing an interruption signal. Consequently, base current of a transistor 110 is interrupted, and thus interrupting current supply to a load 23.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to an automobile battery (hereinafter referred to as a battery).
The present invention relates to an inverter device for an automobile (hereinafter referred to as an inverter device) that obtains an alternating current voltage from a vehicle.

[Conventional technology]

In conventional inverter devices, the current supplied to the load is excessive.
When a current occurs, a fuse or no-fuse breaker is used to cut off the current to protect the power supply and inverter device or prevent short-circuit accidents on the load side.

[Problem to be solved by the invention]

However, in such an inverter device, the fuse or bimetal type no-fuse breaker has a breaking characteristic that easily changes depending on the ambient temperature, which may cause damage to the battery or the inverter device. In addition, electromagnetic no-fuse breakers cannot change the time it takes to shut off depending on the current value, so even if there is a temporary overcurrent, such as when starting a motor, the supply current will be cut off instantly. There was a problem.

In addition, the structure was such that anyone could easily use it in an overcurrent condition by replacing the fuse with a fuse that exceeds the rating, or by fixing the return handle of the no-fuse breaker to the return side with adhesive tape or the like. This has led to damage to the battery or inverter device or short-circuit accidents on the load side.

SUMMARY OF THE INVENTION Therefore, the present invention provides an inverter device having the following features: the cut-off characteristics do not change depending on the ambient temperature, the time until cut-off changes depending on the current value, and it is possible to prevent intentional use in an overcurrent state. The purpose is to

[Means to solve the problem]

In order to achieve such an object, an inverter device of the present invention includes an inverter circuit that converts a DC voltage into an AC voltage and supplies it to a load, a current detection circuit that detects the value of the current supplied to the load, and a current detection circuit that detects the value of the current supplied to the load. Consisting of a cutoff control circuit that outputs a cutoff signal when the current value exceeds a predetermined current value and continues for a predetermined time corresponding to the supplied current value, and a current cutoff circuit that cuts off the supplied current in response to the cutoff signal. The gist is:

[Effect]

In the inverter device of the present invention, the inverter circuit converts a DC voltage into an AC voltage and supplies it to a load. When the supply current value to the load detected by the current detection circuit exceeds a predetermined current value and continues for a predetermined time corresponding to this supply current value, the cutoff control circuit outputs a cutoff signal. The current cutoff circuit cuts off the current supplied to the load upon receiving the cutoff signal.

〔Example〕

FIG. 1 is a circuit diagram showing an embodiment of an inverter device of the present invention.

The inverter device 10 of the present invention includes an inverter circuit 11
, a current detection circuit 12, a cutoff control circuit 13, a current cutoff circuit 14, etc., are basically configured, and a battery 21 is connected to an input terminal 20.20, and a load 23 is connected to an output terminal 22.22.

Next, each circuit constituting the inverter device 10 of the present invention will be explained in detail.

The inverter circuit 11 has a battery 21 connected to its input side and a load 23 connected to its output side, and converts the DC voltage of the battery 21 into, for example, a commercial AC voltage of 50 Hz, 100 cm. The positive terminal 33 of the battery 21 is connected to the middle point 32 of the logic coil 31 of the transformer 30, the collectors of transistors 34 and 34 are connected to both ends of the secondary coil 31, and the emitters of the transistors 34 and 34 are both connected to the ground 35. connected to. The drive circuit 36 is a known circuit, and is connected to the bases of the transistors 34, 34, and outputs a signal to the bases so that the transistors 34, 34 are alternately turned on. Secondary coil 37 of transformer 31
The output terminal 22 is connected to the current transformer 3 through the coil 39.
．． 22 is provided, and a load 23 is connected to the output terminal 22.22.

The current detection circuit 12 includes a current transformer coil 39 connected in series to the secondary coil 37 side of the transformer 30;
It can be composed of a secondary coil 50 of the current transformer 38 and a rectifier circuit 51 that rectifies the voltage generated in the secondary coil 50, and the voltage generated in the secondary coil 50 is rectified and sent to the cutoff control circuit 1.
Output to 3.

The cutoff control circuit 13 includes three operational amplifiers 60, 61, and 6.
2, each operational amplifier's ten terminals 6
3.64.65, the reference tS- is supplied from the DC constant voltage circuit 66.
is applied. In the operational amplifier 60, the output of the current detection circuit 12 is connected to one terminal 67, and the output terminal 68 is connected to one terminal 69.70 of the operational amplifier 61.62. Output terminals 130. of operational amplifiers 61.62.
131 is connected to the gate terminal 72 of the thyristor 71 of the current cutoff circuit 14. Resistors 73 to 7EH are used to set the reference voltage, resistors 79 to 84 are used to set the amplification level, resistors 85 to 92 are used to limit the current, and capacitor 95 is used to set the reference voltage.
-99 is for noise absorption, diode 100.100
is for backflow prevention.

Further, the resistor 101 and the capacitor 102 are used for setting a time constant.

The current cutoff circuit 14 includes a thyristor 71 and a transistor 1.
10.111, relay 112, etc. The anode of the thyristor 71 is connected to the output terminal 113 of the DC constant voltage circuit 66 together with the base of the transistor 110, and the cathode of the thyristor 71 is connected to the ground 35. Transistors 110 and 111 form a Darlington connection, with the collector of transistor 111 connected to relay 112 and the emitter of transistor 111 connected to ground 35. The relay 112 is connected to a power switch 115 via a backflow prevention diode 114, and the power switch 115 is connected to the positive electrode 33 of the battery 21. Further, the contact 116 of the relay 112 is connected between the midpoint 32 of the primary coil 31 of the transformer 30 and the positive electrode 33 of the battery 21 . Resistors 120 to 123
is for current limiting, and the diode 124 is for absorbing back electromotive force.

Note that the diode 114 for backflow prevention is connected to the battery 21.
This is to protect the inverter device by blocking current from the battery 21 when the battery 21 is reversely connected.

The DC constant voltage circuit 66 is a known circuit composed of a three-terminal regulator IC, etc., and is used as a supply voltage source for operational amplifiers, transistors, thyristors, and the like. However, if these supply voltages can be substituted by the voltage of the battery 21, this is not necessarily necessary.

Next, the operation of the inverter device 10 of the present invention will be described.

First, the battery 21 is connected to the input terminal 20.20, and the output terminal 2
2. Connect the loads 23 to 22 and turn on the power switch 1.
15, the respective reference voltages are applied from the DC constant voltage circuit 66 to the child terminals 63, 64, and 65 of the operational amplifiers 60, 61, and 62. Further, since one terminal 67 of the operational amplifier 60 is OV, the output terminal 68 is Ov,
Output terminals 130 and 131 of operational amplifier 61 and 62 are also OV
It is.

Therefore, the thyristor 7e is off, and base current flows from the DC constant voltage circuit 66 to the transistor 110, turning on the transistors 110 and 111. Therefore, when the current flows through the relay 112 and the contact 116 closes, the DC voltage of the battery 21 is changed to the inverter circuit 11.
is applied to the transformer 30.

In the inverter circuit 11, when the transistors 34 and 34 are turned on alternately, an alternating current voltage is generated in the primary coil 31 of the transformer 30, and is transformed into a predetermined voltage in the secondary coil 37. The AC voltage thus obtained is supplied to the load 23.

The current supplied to the load 23 causes the secondary coil 50 of the current transformer 38 of the current detection circuit 12 to generate a voltage. This voltage is outputted to one terminal 67 of the operational amplifier 60 of the cutoff control circuit 13 via the rectifier circuit 51 .

Here, if the current value I supplied to the load 23 is smaller than the first predetermined current value If, the voltage at one terminal 67 of the operational amplifier 60 is lower than the voltage at the child terminal 63, so the inverter device jlO is in the above state. is maintained, and the current supplied to the load 23 is maintained.

Further, when the current value I supplied to the load 23 becomes larger than the first predetermined current value 11, one terminal 6 of the operational amplifier 60
The voltage at terminal 7 becomes higher than the voltage at child terminal 63, and the voltage at output terminal 68 increases in proportion to the difference between the voltage at one terminal 67 and the voltage at child terminal 63. That is, the operational amplifier 60 operates as a voltage amplifier. And capacitor 1
The capacitor 102 is charged according to a specific number determined by the capacitance value of the capacitor 02 and the resistance value of the resistor 101.

Then, when the supply current value summer continues to be larger than the first predetermined current value [1, and a predetermined time corresponding to the supply current value summer has elapsed, the charging voltage of the capacitor 102, that is, the voltage at one terminal 7o of the operational amplifier 62. becomes higher than the voltage at the child terminal 65, and the voltage at the output terminal 131 of the operational amplifier 62 becomes H.
A level, that is, a cutoff signal is output. Then, a gate current flows from the DC constant voltage circuit 66 to the builistor 1, turning on the thyristor 71, and an anode current flows, thereby cutting off the base current of the transistor 110. Then, the transistors 110 and 111 are turned off, power to the relay 112 is stopped, the contact 116 is opened, and the current supplied to the load 23 is cut off.

Furthermore, when the supply current value ■ to the load 23 becomes larger than the second predetermined current value I2, the voltage at the output terminal 68 of the operational amplifier 60, that is, the voltage at one terminal 69 of the operational amplifier 61, becomes higher than the voltage at the child terminal 64. is also expensive, op amp 61
The voltage at the output terminal 130 of
The number is output.

Then, the thyristor 71 is turned on, the energization to the relay 112 is stopped, the contact 116 is opened, and the current supplied to the load 23 is cut off. In this case, the supply current value I to the load 23
However, after the current exceeds the second predetermined current value I2, the current is instantaneously supplied to the load 23 until the current supplied to the load 23 is cut off.

The second panel is a graph showing the current interruption characteristics of the inverter device of the present invention.

The horizontal axis is the supply current value 1 to the load. The M axis is the time T until shutoff when the supply-% flow value I is held.

If the supply current (if! I continues to maintain the first predetermined current value 11, the supply current is cut off at time T1. Then, +
The closer the It supply current value I is to the second predetermined current value 2, the shorter the time T until shutoff. Furthermore, a second predetermined current value 12
At the above supply current value I, the supply current is instantaneously cut off.

Therefore, in the case of a temporary overcurrent such as when starting a motor, the circuit will not be cut off unless the overcurrent condition continues for a certain amount of time. In addition, large 11t'lA such as short circuit condition
will be instantly blocked. Furthermore, since the heat generated by overcurrent is not used for current detection, it exhibits stable interrupting characteristics even when ambient temperature changes.

Further, when the supply current is cut off, the thyristor 71 remains on, and the inverter device 10 will not be restored unless the -degree power switch 115 is opened. Also,
In order for the inverter device 10 to recover, the relay 112
contact 116 and power switch 115 both need to be closed.

However, since the user can only operate the power switch 115 from the outside of the inverter device 10, the user cannot intentionally use the inverter device 10 in an overcurrent state.

In addition, in FIG. 2, the supply current value ■ is the second predetermined current value ■
2, the time T until shutoff decreases linearly, but it may also decrease in a convex or concave manner.

Further, a first predetermined current value 11, a second predetermined current value I2,
To give an example of a specific numerical value such as the time T1 until interruption at the first predetermined current value 1, the predetermined current value 11 is 5A.
, the predetermined current value I2 is IOA, and the time T1 is 3 seconds.

In the above embodiment, the operational amplifier 60 of the cutoff control circuit 13 is used for voltage amplification, so it may be omitted if the output voltage of the current detection circuit 12 is sufficiently large.

Furthermore, in the above embodiment, the L transistors 110 and 111 of the current cutoff circuit 14 are configured with Darlington connections, but the transistors 110 and 111 have a sufficiently large current amplification factor.
Of course, it may be replaced with .

Furthermore, the current detection circuit 12 is a current transformer 30 in the above embodiment.
Although it is provided on the side of the secondary coil 37, it can also be provided on the side of the secondary coil 31 or on the side of the pantry 21 from the midpoint 32 of the deciding coil 31.

It should be noted that the configurations of the inverter circuit 11, current detection circuit 12, cutoff control circuit] 3, current cutoff circuit 14, etc. are not limited to the above embodiments, and it is of course possible to change the design without departing from the gist. be.

〔Effect of the invention〕

As explained above, the inverter device of the present invention provides the following effects.

(1) Since the heat generated by overcurrent is not used for current detection, stable interrupting characteristics can be obtained even with changes in ambient temperature, and damage to the power supply or inverter device or short-circuit accidents on the load side can be reliably prevented. I can do it.

Ru.

(2) Since the time until shutoff can be changed according to the current value, the supply current can be used without instantaneously shutting off even if there is a temporary overcurrent such as when starting the motor. The types of loads can be increased.

(3) Since the device has a structure that cannot be used in an overcurrent state, it is possible to reliably prevent damage to the battery or inverter device or short-circuit accidents on the load side caused by intentional use in an overcurrent state.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram showing an embodiment of an inverter device of the present invention, and FIG. 2 is a graph showing current interrupting characteristics of the inverter device of the present invention. 10...Inverter device 11...Inverter circuit 12...Current detection circuit 13...Break control circuit 14...Current cut-off circuit 23...Load Figure 2 Patent applicant Yoshida Denpa Kogyo Co., Ltd. person
Patent attorney Kichi 1) A telegraph message from a major association to Kanji Yoshiharu (Suminum)

Claims (1)

[Claims] an inverter circuit that converts a DC voltage into an AC voltage and supplies it to a load; a current detection circuit that detects a current value supplied to the load; An inverter device for an automobile comprising a cutoff control circuit that outputs a cutoff signal when the cutoff signal continues for a certain period of time, and a current cutoff circuit that cuts off the supply current in response to the cutoff signal.