JPH01311871A - Driving device - Google Patents

Abstract

PURPOSE:To make a circuit and a transformer small-sized by converting output signals of a pulse generation circuit into DC on the secondary side of a transformer and by converting this voltage into pulse signals again using a switching element to drive the external switching element. CONSTITUTION:A driving device 1 is connected to an inverter circuit 2. As its pulse transformer 12 an intermediate tapped one is used to the secondary coil. To the secondary coil of this transformer 12 a rectification-smoothing circuit 40 is connected with rectification diodes 34 and 35, resistances 36 and 37 and smoothing capacitors 38 and 39. Transistors(Tr) 41 and 43 are connected to this output and each base is connected to the initial winding of the secondary coil for the pulse transformer 12. The output energy of a pulse generation circuit 8 is thereby stored in the rectification-smoothing circuit 40 through the pulse transformer 12. It is converted into pulse signals again through Trs 41 and 42 and drives external Trs 3-4. As a result, the peak value of current through the pulse transformer 12 is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a drive device used for driving power transistors, power MO3FETs, and the like.

BACKGROUND OF THE INVENTION Conventionally, this type of drive device has been used in a half-bridge inverter device as shown in FIG. Drive device 1
The output of is connected to the inverter circuit 2. The inverter circuit 2 includes a transistor 3, a transistor 4, a capacitor 5, a DC power supply 6, and a load 7. The drive circuit 1 includes a pulse generation date W@8, a pulse transformer 12, a constant voltage diode 13, a diode 14, a diode 15 connected to the secondary side of the transformer 12, and a transistor 3.
It is composed of a resistor 16 and a resistor 17 for driving.

The pulse generating circuit 8 is composed of an oscillator 9, a transistor 11 as a switching element that is turned on and off according to a signal from the oscillator 9, and a DC power supply 10.

18 is a drive circuit.

The inverter circuit 2 alternately turns on the transistors 3.4 to supply a high frequency current to the load 7, and the oscillator 9 of the drive device 1 generates a voltage v1 when turning on the transistor 3 as shown in FIG. ) as shown in Figure 6(b), and when transistor 4 is turned on, voltage ■2 is set to ``H'' level as shown in Figure 6(b).
As shown in FIG. 1, the 0 oscillator 9 which outputs "H" level outputs "L" level for both V1 and V2 during time t1 in order to avoid simultaneous conduction of transistors 3 and 4 during the storage period. First, the operation during the period when Vl is at the "I" level will be explained. In this case, the transistor 11 is turned on and the output voltage of the direct Kth source 10 is applied to the primary coil of the pulse transformer 12.
A current 11 as shown in FIG. 6(d) flows through the collector of. The secondary coil of the transformer 12 is provided with a voltage V3 (FIG. 6(c)) in the direction of forward biasing the base of the transistor 3.
] occurs, the current is limited by the resistor 16, a forward base current is supplied, and the transistor 3 is turned on. At the same time, magnetic energy is stored in the excitation inductance of the pulse transformer 12. When the t-pressure v1 reaches the 'L' level, the transistor 11 is turned off.Then, the magnetic energy stored in the transformer 12 during the on period is turned off. Therefore, a reverse voltage [A in Fig. 6(C)] is applied to the secondary side of the pulse transformer 12.
) is generated, supplies a reverse base current to the transistor 3 through the diode 15, and turns off the transistor 3. The remaining magnetic energy after the transistor 3 is turned off is absorbed by the series circuit of the constant voltage diode 13 and the diode 14. On the other hand, in the drive circuit 18, the transistor 4
The transistor 4 is reverse biased while the voltage v2 is at the "1-" level. therefore,
(2) The transistor 3 and the transistor 4 are turned on alternately, and a high frequency current is supplied to the load 7. At this time, a current 11 proportional to the forward base current of the l transistor 3 and an excitation current I lo offi flow through the transistor transistor 11 during the period when the voltage ■1 is at the "H" level.

FIG. 7 shows another conventional example, in which the transistor 3.4 in FIG. 6 is replaced with a MOS type FET 20.21, and the circuits are exactly the same. Figure 8 fa) to (d)
The waveforms of various parts of this circuit are shown in comparison with FIGS. 6(a) to 6(d). In this case as well, when the t pressure ■1 reaches the "11" level, the voltage ■3 becomes the "1■" level, and the FET 20
turns on. Further, when the voltage (1) becomes the "L" level, the magnetic energy stored in the pulse transformer 12 during the on period causes the voltage (v3) to become zero, and the FET 20 is turned off.

Problems to be Solved by the Invention In the drive device 1 shown in FIG. 5, in order to speed up the turn-on of the transistor 3, when performing so-called overdrive, the initial value II of 11, as shown in FIG. 6(d), is set. needs to be made larger. Therefore, it is necessary to increase the current rating of the pulse transformer 12 and reduce the impedance of the winding, and the pulse transformer 12 becomes large. In order to turn off the 1-transistor 3 at a high speed during turn-off, it is necessary to store a very large amount of magnetic energy in the pulse 1-lance 12. Therefore, the excitation current 110 increases, and the output of the pulse generating circuit 8 It is necessary to make the peak value of the current quite large.

A similar problem exists in the drive device 1 shown in FIG. 8, but in this case, taking advantage of the fact that the FETs 20 and 21 are voltage control elements, the transistor 11 and the pulse transformer 12 are replaced by the drive device shown in FIG. Although the size can be reduced compared to the case of It becomes necessary to flow a large current and a large excitation current, and the pulse lance 12 cannot be sufficiently miniaturized.

An object of the present invention is to provide a drive device that can flow a large peak current as a drive output signal even if the pulse transformer is small.

Means for Solving the Problems The drive device of the present invention connects the primary coil of a pulse transformer to the output of a pulse generation circuit, connects the secondary coil of the pulse transformer to a rectifying and smoothing circuit that converts the output signal into DC,
The present invention is characterized in that a switching element is connected to the output of the rectifying and smoothing circuit, and the switching element is turned on and off in synchronization with the output of the pulse generating circuit, and a drive output signal is obtained from the output of the switching element.

Effect: According to this configuration, the output energy of the pulse generating circuit is stored in the Nm smoothing circuit via the pulse lance. The peak current required when the external switching element to be driven is inverted flows from the rectifying and smoothing circuit, and is converted into a pulse signal again by the switching element to drive the external switching element. The peak value of the current flowing through is suppressed.

Embodiments Hereinafter, embodiments of the present invention will be explained based on FIGS. 1 to 4. Components having the same functions as those in FIGS. 5 and 7 showing the conventional example will be described with the same reference numerals.

FIG. 1 shows a first embodiment, in which a drive device 1 is connected to an inverter circuit 2, like the inverter device shown in FIG. The side configuration has been changed as follows.

Note that here, as the pulse transformer 12, a one having a secondary coil with an intermediate tap is used.

The secondary coil of the pulse transformer 12 includes a rectifier diode 34, 35, a resistor 36, 37, and a smoothing capacitor 38.
, 39 is connected thereto. Transistors 41 and 43 as switching elements are connected to the output of the rectifying and smoothing circuit 40, and their respective bases are connected to the winding start of the secondary coil of the pulse transformer 12. Note that here, the transistor 41 acts as a switching element that forward biases the transistor 3 of the inverter circuit 2, and the transistor 42 acts as a switching element that reverse biases the transistor 3. Resistor 43 is for base current limitation.

Next, the operation will be explained with reference to FIG.

In FIG. 2, (aHb) is the output voltage of the oscillator 9 ■1,
2. (C) is the voltage v3 between the base and emitter of the transistor 3, [dHe] is the terminal voltage V4 of the smoothing capacitor 38 and the smoothing capacitor 39. V5, (f) is the output current 11 of the pulse generating circuit 8, and (g) is the waveform of the base current I2 of the transistor 3. FIGS. 2(a) and 2(b) have the same waveforms as FIGS. 6(a) and (b). Smoothing capacitor 38
．． 39 terminal voltage V4. V5 is charged from the secondary coil of the transformer 33 via the diode 34, the diode 35, the resistor 36, and the resistor 37, and rises while the voltage V1 is at the "H" level. In FIG. 2, when the voltage 1 reaches the "H" level at time t2, the base of the transistor 41 is raised to a high potential by the action of the pulse transformer 12.
The forward base current of the transistor 3 flows through the smoothing capacitor 38
is supplied through transistor 41. Furthermore, when the voltage V1 goes to the “L” level at time t3, a negative voltage is applied to the base of the transistor 42 due to the magnetic energy stored in the pulse transformer 12, and the reverse base current of the transistor 3 flows from the smoothing capacitor 39. is fed through transistor 42.

Therefore, as shown in FIG. 2(f), the output current 11 of the pulse generating circuit 8 does not need to be supplied with an overdrive amount due to the amplification effect of the transistor 41 even when the transistor 3 is turned on. Due to the amplification effect of the transistor 42, the amount of magnetic energy to be stored in the transistor 42 can be reduced to a small value, there is no need to supply a large excitation current, and the current rating of the pulse generating circuit 8 and the pulse transformer 12 can be reduced.

FIG. 3 shows another embodiment, in which the transistor 3.4 of the inverter circuit 2 in FIG. 1 is a MOS type FET 20,
The only difference is that it is replaced with 21, and the rest is the same. 4(a) to 4(a) are waveforms of various parts in FIG. 3. In FIG. 4, (a) to (8) are the same as (a) to (e) in FIG.

As shown in Fig. 4 (g), the gate current of the FET 20 is large in order to speed up the on and off operations, and is required only during extremely short periods of transition from on to off and from off to on. is the smoothing capacitor 38
and is supplied from the smoothing capacitor 39, the output current 11 of the pulse generating circuit 8 at this time can be a very small value.
current rating can be made very small.

Note that although positive and negative voltages were applied to the FET 20 as shown in FIG. 4(C), the threshold value of the FET 20 is
~3 volts or more, the voltage 3 during the off period may be set to zero. In that case, by connecting the collector of the transistor 42 to the source of the FET 20, the smoothing capacitor 39, resistor 37, and diode 35 This eliminates the need for the intermediate terminal of the secondary coil of the pulse transformer 12.

In each of the embodiments described above, the final stage of the inverter circuit 2 is a power transistor or a power MO8FET, but the same applies to the switching element of the inverter circuit 2.

Effects of the Invention According to the present invention, as shown in L, the output signal of the pulse generating circuit is converted into DC by the rectifying and smoothing circuit on the secondary side of the lance, and the DC-converted voltage is pulsed again by the switch element. Since it is converted into a signal to drive an external switching element, when a peak current flows to an external switching element, it is allowed to flow from the rectifying and smoothing circuit, and the current flowing from the pulse generating circuit via the pulse transformer can be suppressed to a small level. It is possible to achieve miniaturization of the pulse generation circuit and the pulse transformer.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an inverter device employing the drive device of the present invention, Fig. 2 is a waveform diagram of the main parts of the same device, Fig. 3 is a block diagram of another embodiment, and Fig. 4 is a main part of the same device. Fig. 5 is a configuration diagram of an inverter device using a conventional drive device;
FIG. 7 is a diagram showing its operating waveforms, FIG. 7 is a configuration diagram of another conventional example, and FIG. 8 is a waveform diagram of essential parts of the same device. 1... Drive device, 8... Pulse generation circuit, 12...
・Pulse transformer, 40... Rectifier and smoothing circuit, 41...
・L-transistor [switch element]. Agent Yoshihiro Morimoto Figure 2
-1f 1iD'gl
41 ->Lancey (S A4+) Figure 2 Figure 3 Cause 7, 2 Figure 4 Figure S, ・2 Amber no Mi to f be hard! fig.

Claims (1)

[Claims] 1. Connect the primary coil of the pulse transformer to the output of the pulse generation circuit, connect the secondary coil of the pulse transformer with a rectifier and smoothing circuit that converts the output signal to DC, and connect a switch element to the output of the rectifier and smoother circuit, A drive device that turns on and off the switch element in synchronization with an output signal of the pulse generating circuit and obtains a drive output signal from the output of the switch element.