JPS5986921A - Base driving circuit of transistor - Google Patents

Abstract

PURPOSE:To make a titled circuit have a high efficiency and to make it small- sized by Darlington-connecting an MOSFET between the collector and the base of a bipolar transistor, and also connecting a switching element and a reverse bias electric power source between said base and the emitter. CONSTITUTION:When DC voltage is applied and an MOSFET 12 is turned on, a forward direction base current IB1 of a bipolar transistor 1 for electric power flows as shown in the figure. On the other hand, a capacitor 11 is charged with a forward direction voltage drop voltage portion of a diode 10 through a resistance 9. Subsequently, when a transistor 7 is turned off and a transistor 8 is turned on, a reverse direction base current IB2 flows as shown in the figure. This reverse direction base current IB2 is used for drawing out an accumulation carrier of the transistor 1, and when the carrier is eliminated, the current IB2 does not flow.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a pace drive circuit for bipolar transistors.

[Technical background of the invention]

In recent years, the power of transistors has increased, and they have come to be widely used in place of thyristors for power control on the order of tens of kW. This is because transistors have advantages such as being able to be turned on and off with only a pace signal, being capable of high-speed switching, eliminating the need for a commutation circuit, and making the device smaller and lighter.

On the other hand, transistors have the disadvantage that they require more pace drive power when compared to thyristor dart signals. Therefore, as the power of devices increases, there is a need for a base drive circuit with an internal configuration suitable for this.

FIG. 1 shows an example of the internal circuit of a power bipolar transistor. As shown, power bipolar transistors are typically of the NPN type. In addition, in order to increase the direct current amplification factor (hFz), Ql r Q
It has a Darlington configuration consisting of two transistors, a speed-up diode (SPD) for quick turn-off, a freewheel diode (FRD) in the opposite direction, and a resistor R1 for stable drive of the element. It is characterized by having R2.

On the other hand, the base current for driving such a transistor at high speed is a reverse base current IB1 at the moment of turning off, compared to a normal forward base current IB1 in the on state.
It is necessary to stream B2.

FIG. 2 shows an example of a pace drive circuit proposed for this purpose.

In the figure, 1 is the power bipolar transistor shown in FIG. 2 and 3 are output stage transistors of the base drive circuit, which are turned on and off by signals prepared in advance. The operations of transistors 2 and 3 are opposite to each other υ, so when transistor 2 is on, transistor 3 is off,
A signal is given so that when transistor 3 is on, transistor 2 is turned off. Further, 4 is a pace resistor, and the value of 1 is determined from when 1 is caused to flow from the forward direction pace current to the power bipolar transistor 1 when the transistor 2 is on. This base current IB1 is supplied from the positive electrode side of a separately provided DC power source to a resistor 4. Transistor 2. Power bipolar transistor 1. It passes through the diode 5 and flows to the negative electrode side. On the other hand, diode 5. :i capacitors 6 are connected in parallel as shown. When a forward pace current flows through the diode 5, the capacitor 6 is charged to the illustrated polarity due to the forward voltage drop.

Next, when the power bipolar transistor 1 is to be turned off, the transistor 2 is turned off and the transistor 3 is turned on at the same time. Then, the charge charged in the capacitor 6 flows from the positive electrode side of the capacitor through the power bipolar transistor 1° transistor 3 to the negative electrode side of the capacitor. This is a reverse base current called B2, which speeds up the switching on of the power bipolar transistor 1. In this case, depending on the type of power bipolar transistor 1 used, a diode 5 or a capacitor 6 may be used.
By increasing the value and number of , it is possible to flow a sufficient reverse base current.

[Problems with background technology]

In pace drive circuits having such a configuration, heat generation in the base resistor 4 through which the forward pace current IBi flows often poses a problem. For example, the rated collector current of the power bipolar transistor used is 10OA.
, its hFE is 100/8
0X:2). When the overdrive factor is set to 2, the forward pace current IB1 is 2.5A. Also,
The loss when pace resistance 4 is 50 is (2,5)2
X5=31.25W. In this way, conventional pace drive circuits are fabricated on printed circuit boards.
If 1.25 W of heat is generated, there are disadvantages such as the resistor used becomes thicker, the 7' lint board becomes larger, other semiconductor components are heated, and the efficiency of the entire device decreases.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned drawbacks.
The purpose is to provide a highly efficient, compact, and high performance transistor pace drive circuit.

[Summary of the invention]

In order to achieve the above object, the present invention comprises connecting a MOS-FET between the collector and base of a bipolar transistor in Darlington, and connecting a semiconductor switching element and a reverse bias power supply between the base and emitter of the bipolar transistor. It is characterized by

[Embodiments of the invention]

An embodiment of the present invention shown in the drawings will be described below.

FIG. 3 shows an example of the configuration of a pace drive circuit for a power bipolar transistor according to the present invention. In the figure, 1 is the aforementioned power bipolar transistor. Reference numeral 7 denotes a transistor of the pace drive circuit, which turns on the power bipolar transistor 1 when the trunk stuff turns on. 8 is transistor 7
This transistor is turned on when the power bipolar transistor 1 is off, and is used to flow a reverse base current IB2 when the power bipolar transistor 1 is off. Further, 9 is a charging resistor for charging the capacitor 11. 10 is a diode,
The capacitor 11 is charged by this forward voltage drop. Furthermore, a MOS-FET 12 has its source connected to the pace of the power transistor 1, and its drain connected to the collector, forming a so-called Darlington connection.

Here, the dart of the MOS-FET is insulated from the internal channel portion by an insulating oxide film, and is a type of field effect transistor that can be turned on and off by simply applying a voltage to the dart.

Next, the operation of the non-base drive circuit configured as described above will be explained. Now, in FIG. 3, when transistor 7 is turned on, a DC voltage is applied to the gate of MOS-FET 12, and MOS-FET 12 is turned on. When this MOS-FET is turned on, the forward pace current pace IB1 of the power bipolar transistor l connected to Darlington is changed to IvIO8-FET as shown in the figure.
22 drain→source→base of power bipolar transistor 1→emitter.

Next, a description will be given of how to flow the reverse pace current IB2 when the power bipolar transistor l is turned off.

The capacitor 11 is charged through the resistor 9 by the forward voltage drop of the diode 1o. Then, when the transistor 7 is turned off and the transistor 8 is turned on, 2 flows from the emitter of the power bipolar transistor 1 to the base current from the reverse base current, and then returns through the transistor 8 to the capacitor 1. This reverse base current IB21d is only for drawing out the accumulated carriers of the power bipolar transistor 1, and when the carriers disappear, the current 2 stops flowing.

The base drive circuit configured as described above provides the following effects.

(a) Power bipolar transistor 1 and MOS-
Since we configured FET 12 to be connected in Darlington,
Power for pace drive is not required, the pace circuit is simplified, and heat generation in the base circuit is eliminated.

(b) Since the switching semiconductor element and the reverse bias power supply device are provided between the pace and the emitter of the power bipolar transistor 1, the power bipolar transistor 1 can be turned off at high speed.

Next, another embodiment of the present invention will be described using FIG. 4.

Note that the same parts in FIG. 4 as those in the embodiment shown in FIG. 3 are designated by the same reference numerals, and the explanation thereof will be omitted. In this example, M.O.
This makes use of the characteristics that the S-FET is a voltage control element and that the IC, l:, 9 can also be driven directly. 13 in the figure is a digital IC at the final stage of the control circuit, which determines whether the power bipolar transistor 1 is turned on or off. 14 is an inverting digital IC, and when the input is °'1'', the output is II O#.1
5 is the second MOS-FET, and the reverse base current l
This is for streaming B2.

In the power bipolar transistor base drive circuit configured as described above, when the output of the digital ICl3 at the final stage of the control circuit is 1'', the MO8-FET 12 is turned on and the forward pace current IB1 flows.Digital IC
When the output of l3 is 0'', the output of digital ICI 4 is °l
'', the second MOS-FET 15 is turned on to flow the reverse base current IB2, and the power bipolar transistor 1 is turned off.

Therefore, according to this embodiment, the MO connected to Darlington
Another second MOS-F in addition to S-FET l 2
Since the ET 15 is used, there is an advantage that the power bipolar transistor 1 can be directly controlled by the output signal of the digital IC.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide a highly efficient, compact, and high performance transistor base drive circuit.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the internal equivalent circuit of a power bipolar transistor, Fig. 2 is a diagram showing a conventional base drive circuit, Fig. 3 is a circuit diagram showing an embodiment of the present invention, and Fig. 4 is a diagram showing the present invention. FIG. 3 is a circuit diagram showing another embodiment of the present invention. 1... Power bipolar transistor, 2.3°7.
8...Transistor, 4,9...Resistor, 5゜10・
・Diode, 6.11...Capacitor, 12.15
...MOS-FET, Zs, J4...
・Digitale C0 Applicant Representative Patent Attorney Takehiko Suzue Figure 1 Figure 2

Claims (1)

[Claims] MOS between collector and pace of bipolar transistor
- A transistor pace drive circuit characterized in that a FET is Darlington connected, and a semiconductor switching element and a reverse bias power supply are connected between the pace and emitter of the bipolar transistor.