JPS6022466A - Base current feeding circuit - Google Patents

Abstract

PURPOSE:To reduce the heat loss of a resistor by supplying a base current from the second capacitor when a transistor chopper is ON, and transferring the voltage of the first capacitor to the second capacitor when the voltage falls. CONSTITUTION:A transistor chopper 7 connected in parallel with a series circuit having a capacitor C1, a diode D4 and a capacitor D2 is connected in series with a motor 5, and the motor 5 is driven by ON and OFF of the dhopper 7. A transistor TR12 is turned ON by a conduction rate controller 11, the chopper 7 is turned ON by the discharge of a capacitor C2 as half of a power source voltage, the voltage is detected by a Schmitt circuit 10, a transistor TR3 is turned ON when the detected level decreases, the voltage of the capacitor C1 is transferred to the capacitor C2, and the chopper 7 is controlled. Therefore, since charging voltage can be reduced, the loss of the resistor R1 can be suppressed to the minimum limit, thereby reducing the heat loss.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a pace current supply circuit for a transistor chopper, and more particularly to a pace current supply circuit in which internally generated heat loss is small.

[Background of the invention]

The base current of the transistor chopper can be supplied via a power supply and a resistor, but in this case a lot of power is consumed by the resistor, which increases heat generation. For this reason, some kind of countermeasure is required for high-power choppers, and one of them is a capacitor series charge/parallel discharge method that does not supply base current directly from the power supply voltage, but uses a capacitor with the power voltage reduced to about half. was considered (see JP-A-58-46882). According to this method, the heat loss consumed by the resistor can be reduced to about half, but the amount of heat generated is still large, and there is a problem that a heat dissipation arrangement using a large-capacity resistor is required.

[Purpose of the invention]

The present invention has been made to eliminate the above-mentioned problems, and its purpose is to provide a pace current supply circuit with less heat loss by preventing unnecessary base current from flowing through the transistor chopper.

[Summary of the invention]

In the present invention, first and second capacitors connected in series are connected in parallel with a transistor chopper to charge these capacitors when the transistor chopper is off, and to supply base current from the second capacitor when the transistor chopper is on. In addition, when the terminal voltage of the second capacitor decreases due to the supply of the base current, means is provided for detecting the decrease and transferring the charge of the first capacitor to the second capacitor. It is characterized by this.

[Embodiments of the invention]

The present invention will be described in detail below with reference to Examples.

FIG. 1 shows an embodiment of the present invention, in which the main circuit of the motor is connected to a positive power source 1, a current detector 3, an armature 5 of the motor 4, forward contactors F and C, a field coil 6, a contactor R, C,) negative side power supply 2 via transistor chopper 7
This is the circuit that leads to. A series circuit consisting of a diode D3, a capacitor C1, a diode D4, and a capacitor C2 is connected in parallel to the transistor chopper 7, and forward contactors F and C' (I) are operated as shown by the dotted line to turn the main circuit on. At the same time, the capacitor C2 is charged with a voltage that is approximately half of the power supply voltage Vi.The voltage of this capacitor C2 is charged to the transistor TRO that constitutes the transistor chopper 7 via the resistor R1, the diode D5, and the transistor TI' (2). The constant voltage circuit 8 generates a constant voltage line 9 even if the power supply voltage VII fluctuates and supplies it to each control circuit. connected to the circuit 10.The Schmitt circuit 10 is connected to the voltage V2 of the capacitor C2.
is input, and an output voltage Vs as shown in FIG. 2 is generated. That is, when the input voltage v2 becomes low, the high level I (signal shown in FIG. 2) is output.

When a pulse signal having a required on/off ratio is outputted from the conduction rate control circuit 11, it is applied to the transistor TRI and is applied to the Darlington-connected transistor TTL2.
is conductive during its on period.

When transistor T1N2 becomes conductive, the charge in capacitor C2 is transferred to resistor 11,1, diode D5, and transistor TR.
The base current of the transistor chopper 7 flows through the transistor 2, the transistor chopper 7 is turned on and off, and the motor 4 is driven. As this operation continues, the charge in the capacitor C2 is discharged, and the voltage v2 decreases. Voltage V! When the voltage reaches the voltage Vzo shown in FIG. 2, the output voltage of the Schmitt circuit 10 becomes a high level H, and the diode D6 turns off, so that the base potential of the transistor TR3 rises and turns on. Therefore, the charge of capacitor C1 is transferred to resistor R3, transistor TR,3, diode D7, and capacitor C2.
, flows through diode D8. The capacitor C2 is charged. The charging voltage at this time is equal to the sum of the high level output H value of the Habo Schmitt circuit 10 and the Zener voltage of the Zener diode ZD. In this way, the voltage V2 of the capacitor C2 is controlled so that it always falls within a certain range, and this voltage range is controlled by the transistor Tl.
By not allowing an extra base current to flow as a value necessary for turning on and off 'tO, the loss in the resistor R1 can be suppressed to the necessary minimum. Also, when the voltage of capacitor C2 drops, a method is used in which the capacitor C1 is charged.
3 loss can be reduced.

(2) When the transistor chopper 7 turns off, the charging pressure of the capacitor C2 is increased (transistor TR3
shorten the on time).

(3) The emitter-collector withstand voltage of the transistor TR3 can be reduced.

It has the following advantages.

FIG. 3 shows another embodiment of the present invention, in which the configuration shown in FIG. 1 prevents the voltages of capacitors C1 and C2 from becoming excessive, and also prevents the base current from increasing as the motor current increases. , an efficient base current supply circuit is constructed. That is, when the amount of charge discharged from the capacitor C1 is small, its voltage becomes higher than the power supply voltage. At this time, the third
As shown in the figure, capacitor C1 is discharged through diode D9 and choke L1 until it reaches the power supply voltage, thereby preventing overvoltage. Also, since the capacitor C2 supplies the base current of the chopper 7, its voltage decreases. However, if the plugging operation is performed frequently, capacitor C2
Since the charging of is large and the discharging is extremely small, its voltage increases.

Therefore, as shown in Figure 3, resistor R4 and diode 1) 10
, diode D9, and capacitor C2 via choke L1.
This prevents overvoltage from occurring. Furthermore, the base current adjustment circuit 12 detects the motor current by the current detector 3, adjusts the energization l° of the transistor TR4 with an analog value, and controls the voltage of the capacitor C2 by making the base current flow according to the motor current. This is to prevent a decrease in the resistance value and to suppress the amount of heat generated by the resistor R1.

〔Effect of the invention〕

As is clear from the above embodiments, according to the present invention, by supplying the base current of the transistor chopper from a capacitor that is suppressed within the required voltage range, heat loss in the resistor can be significantly reduced. There is an effect that it can be done.

[Brief explanation of drawings]

FIG. 1 is a diagram showing one embodiment of the present invention, FIG. 2 is a diagram showing the operating characteristics of the Schmitt circuit of FIG. 1, and FIG. 3 is a diagram showing another embodiment of the present invention. 7...Transistor chopper, 10...Schmitt circuit, TRO~TR4...Transistor, R1~R3
...Resistance, C1, C2...Capacitor, D1~DI
O...Diode. Agent Patent Attorney Akio Takahashi

Claims (1)

[Claims] 1. The first and second capacitors are connected in series with each other via a diode and are connected in parallel to the transistor chopper to be charged. a switch means for supplying a base current t- from a second capacitor to the transistor chopper via the resistor; and transfer means for detecting the electric charge of the first capacitor and transferring the charge of the first capacitor to the second capacitor until the voltage of the second capacitor reaches a predetermined second level. Current supply circuit.