JPS585431Y2 - Transistor chopper device for electric vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transistor chopper device, and particularly aims to provide a transistor chopper device for electric vehicles that enables base drive with good control efficiency when base driving a main transistor.

An example of a conventional circuit shown in FIG. 1 in which a transistor is applied as a chopper device for an electric vehicle such as a battery-equipped forklift truck using a battery as a power source and a DC motor as a load will be described.

In FIG. 1, DM is the armature of the DC motor, and F is its field winding.

DF is a flywheel diode, TM is a main transistor connected in series to the motor circuit, and an auxiliary transistor TS□ serves as a base drive for the main transistor TM.

T5□ is applied respectively.

R1 is a collector side resistance of the first auxiliary transistor T5□, and R2 is a collector side resistance of the second auxiliary transistor TS2, and a desired base drive signal is inputted from the base electrode of this auxiliary transistor T8□.

E is a battery.

To briefly explain the operation of the conventional circuit example configured in this way, when a desired base drive signal is inputted from the base electrode of the second auxiliary transistor TS2, this auxiliary transistor T5□ is turned ON, and then the first By turning on the auxiliary transistor TSI and finally turning on the main transistor TM, a predetermined armature voltage is applied to the load motor DM, and the DM is driven.

The speed and speed control of the load motor DM is performed by appropriately controlling the average value of the DC voltage applied to the load motor DM, for example, by controlling the conductivity of the main transistor TM.

In an example of a conventional circuit in which such control is performed, for example, when driving on a flat road, a current of 100 A flows through the main transistor T.
Assume that a current of 100 A is flowing through M, and the battery voltage is 50 V.

In this case, assuming that the current amplification factor β of the main transistor TM is 10, the base current ■8 must be set to ■1. /β= 100/10 = 1
OA is necessary.

In the case where the car is now on the road, assuming that the load current I[- is, for example, 500A, the base current LB needs to be 500/10A.

Assuming that 500 A is the maximum load current that this device can handle, the base current IB needs to be supplied at all times when the car is running.

If only 1 OA is applied, if the load suddenly increases, the main transistor TM will not be able to saturate, and the forward voltage drop will increase, causing thermal damage to the main transistor TM. I end up.

In other words, when driving on a flat surface, the load motor DM has 100%
Even when an input of A X50V=5KW is given, the base current I8 is 50A and the battery voltage is 50V.
Therefore, the collector side resistance R of the auxiliary transistor T8□
1, a loss of approximately 50 A x 50 V = 2.5 KW is generated, which has the disadvantage that the efficiency of the device itself becomes extremely poor.

Note that the circuit loss in the stage before the first auxiliary transistor T5□ and the loss due to the saturation voltage drop of the transistor itself are small, so they will be ignored and explained.

The present invention has been devised in view of this point, and will be described in detail below based on Examples.

FIG. 2 shows a basic block configuration diagram according to the present invention,
In the same figure, the same parts as in FIG. This is what I did.

That is, a resistor R8 for detecting the load current is provided in the main circuit, so that the operating power supply voltage generating device A, which generates the operating power supply voltage, can be controlled in accordance with the detected signal value.

To briefly describe the operation of this principle diagram, the base current (8) that drives the main transistor TM of the chopper device is the output voltage (2) of the operating power supply voltage generator (a).

Then, it is approximately V. /R, so it can be expressed as ■.

When 18 increases, 18 increases accordingly.

Therefore, when the load current increases at that time, the base current of the main transistor TM also increases.

Next, to explain in detail a specific circuit example of this embodiment, the embodiment of FIG. 3 uses, for example, a DC
-It is characterized by the application of a DC converter,
As shown in the figure, this DC-DC converter C has a control transistor T whose internal impedance is adjusted according to a load current detection signal derived from a current detection circuit.
.

And glue handle L to suppress charging current.

and a control transistor T.

Each of the capacitors C8 is configured as a capacitor C8 whose charging voltage level is adjusted according to a change in the internal impedance of the capacitor C8.

B is a chopper drive circuit, and this drive circuit has a charging voltage V applied to, for example, the Darlington-connected auxiliary transistor T5□ shown in FIG.

This is to drive the base according to the

To describe the operation of this embodiment configured in this way, the converter control section monitors the level of the load current based on the current detection signal led from the current detection resistor R8. control transistor T depending on the level of the applied load current.

Since the internal impedance of changes, the charging voltage of capacitor C6 of DC-DC converter C changes.

is arbitrarily adjusted according to the detected level of the load current.

Therefore, as is clear from the figure, the charging voltage of capacitor C8 is ■.

is led to the chopper drive circuit B, so that if the load current increases, the chopper drive circuit B will be connected to the Darlington-connected auxiliary transistor Ts□.
By performing a predetermined operation of increasing the base drive voltage applied to the auxiliary transistor TS2, and conversely decreasing the base drive voltage applied to the auxiliary transistor TS2 when the load current decreases, regardless of the level of the load current. This enables highly efficient control in which steady-state power loss is always kept to a minimum value.

To explain this concretely using a numerical example, suppose that a current of 10 OA is flowing through the main transistor TM when the car is running on a flat road, and the current amplification factor of TM is β10.
The base current (18) of the TM should be IB=100/10=10A.

At that time, the operating power supply voltage V is detected by main current (load current) detection.
.

For example, it becomes 5 ■.

The value of resistor R1 of chopper drive circuit B is 5 V.
/10 A20, 5Q is selected, and the loss at this resistor R1 is 10AX5V=50W.

On the other hand, in the conventional device, as mentioned above, < 50 A
Since 50 V = 2.5 KW, it is easy to understand how small the power loss is in this embodiment.

Now, if the load current gradually increases when the car is on the road, for example, and a load current of 500 A flows through the main transistor TM, it will be detected that the load has started to increase and the operating power supply voltage will be reduced.

goes up and ■. The voltage is controlled to be, for example, about 25V.

Therefore, when the load current is 50OA, the base current ■8 is 1.
=25V10.5Q25OA, which means that a base current of a value sufficient to saturate the main transistor TM is supplied.

As described above, in the present invention, when the load increases, the base current IB is changed accordingly, so when the rated load is applied, such as when driving on a flat surface, a commensurately small base current is sufficient, compared to conventional devices. The loss in the base circuit is small,
The overall efficiency of the chopper device can also be greatly improved.

As described above, in the present invention, since the operating power supply voltage applied to the chopper device is changed in accordance with the load current, various effects can be achieved as shown below.

■ Power loss can be significantly reduced compared to conventional equipment, so the efficiency of the equipment itself can be improved.

■ As the operating power supply voltage generating device, well-known devices such as inverters or DC-DC converters can be used, and since they are very efficient, the losses in these applied circuit examples can be ignored and the efficiency can be further improved. This will further improve reliability and stability.

■ Since it supplies enough base current to saturate the main transistor even under heavy loads such as when pitching, thermal damage to the transistor can be completely prevented, further improving reliability and stability. It is.

[Brief explanation of the drawing]

FIG. 1 is a specific circuit diagram showing a conventional device, FIG. 2 is a basic block diagram of the present invention, and FIG. 3 is a specific circuit diagram showing an embodiment of the present invention. DM is the armature of the DC motor, F is its field winding, A is the base drive voltage generator, B is the chopper drive circuit, C is the DC-DC converter, D is the converter control unit, E is the battery, and TM is the main unit. Transistor, T8□, T
s□ is an auxiliary transistor, Tso is a control transistor, and Ro is a load current detection resistor.

Claims (1)

[Scope of utility model registration request] In this device, the average value of DC power supplied to a load motor is controlled by controlling the conductivity of a transistor chopper device inserted into the main circuit and formed by connecting a main transistor and an auxiliary transistor in a Darlington connection. connected in parallel between the terminals of the mains battery,
and a DC-DC converter including a control transistor whose internal impedance is adjusted according to a load current detection signal, a capacitor whose charging voltage is controlled according to a change in the internal impedance of the transistor, and a charging voltage of the capacitor. and a chopper drive circuit for base-driving the auxiliary transistor.