JPS59176927A - Driving circuit of switch element - Google Patents

Abstract

PURPOSE:To minimize power loss with a switching element by using a serial circuit consisting of a diode and a resistance and an inductive element which are set in parallel to said diode to form a driving circuit of a semiconductor element for switching operation. CONSTITUTION:The gate driving circuits of switching semiconductor elements Q1 and Q2 consist of a serial circuit containing diodes D1 and D2 connected in the direction where the conduction is prevented for the elements Q1 and Q2 respectively and a resistance R1 and an inductive IND element L1 which are parallel to the diodes D1 and D2 as well as a serial circuit of a resistance R2 and an IND element L2. When a step type signal is impressed in forward direction to an input terminald 1, the gate voltage of the element Q1 shows the synthesization of a curve which rises up with a time constant obtained by the inter- electrode capacity between the R1 and the Q1 and a curve produced by the L1 and the inter-electrode capacity. This gives some delay to the time during which the Q1 is turned on and prevents that both Q1 and Q2 are simultaneously turned on. Furthermore the gate bias is deepened after the Q1 is turned on, and therefore the ON resistance is reduced. This attains a switching operation with small power loss.

Description

[Detailed Description of the Invention] The present invention relates to a drive circuit for a switching element, and in particular, the speed at which the switch turns 4 during switching IIW is made slightly slower, and the speed at which it becomes non-conducting is increased, thereby reducing the power consumption in the element. The present invention relates to a drive circuit that minimizes loss.

Conventionally, the OJ building's circuit was as shown in Figure 1. In the figure, 1 is the input terminal, and the diode L1
．． and one end of the resistor R1 are k iE. The anode of the diode D, and the curved end of the resistor R, are connected to the gate of the N-channel FET Q. The drain of this F E 1' Qt is led to the output terminal 2 , and the source is connected to the negative power supply 3 . Also, the configuration with the opposite polarity is diode D? It is made up of resistors R, , P-channel FET Qt, is provided with an input terminal 4, and is supplied with a positive power source 5.

Note that, as shown in the figure, FETQr has interelectrode capacitance CI between the gate and drain and between the gate and source.

C7 is present in each case. On the other hand, P channel FETQ2
Similarly, there is an interelectrode capacitance (not shown).

Next, the operation will be explained. Input terminals 1 and 4 are supplied with in-phase square waves with different DC levels, but the FE
Looking at the TQr side, it is necessary to charge and discharge the electrodes JftCx and C2 when turning on and off. Looking at the input side from the gate, the resistance R1v is on when it is on, and the diode D is on when it is off. When it is off, it is slow, and when it is off, it becomes fast.The pressure waveform of this input terminal 1 and the gate of FET Ql is shown in Figure 2 (al).
Since I also operates in the same way, F E T Ql −Qt
can be prevented from becoming conductive at the same time.

By the way, in general, the deeper the gate bias is applied to the FET, the smaller the on-resistance becomes.
1 (The change in resistance is as shown in Figure 2 (bl).

That is, the on-resistance is relatively large after turning on, and gradually decreases as the gate bias becomes deeper. For this reason, despite the switch operation ζ, the FE
The disadvantage is that the power loss at T is relatively large.

Tree Brother I 1. f. This was developed in order to eliminate the drawbacks of conventional ones such as the above one, and by using an inactive element in a part of the gate drive circuit, it is possible to prevent a pair of switching elements from becoming conductive at the same time. An object of the present invention is to provide a drive circuit for a switch element that can minimize power loss in the switch element.

Hereinafter, the present invention will be explained based on the drawings.

FIG. 3 is a circuit diagram showing an embodiment of the present invention, and the difference from the circuit of FIG. 1 is that resistors R1 and RI and R1 are inserted in series with resistors R1 and R1, respectively.

The inactive elements L+ and R2 have small inductance and can be constructed from coils or bead cores. Further, the values of the resistors R, , R, are set smaller than in the case of FIG.

Next, the operation of the present invention will be explained.

The transition from ON to OFF is the same as in the conventional case, but the gate waveform when transitioning from OFF to ON is significantly different. When a step-like signal is applied to the input terminal l in the positive direction, the gate voltage rises with a time constant due to the resistance R and the capacitance between the electrodes (also referred to as the Miller effect), and the curve between Ll and the electrode. This is a combination of the resonance curve caused by the capacitance (resistance is damped by 1 force, resulting in material reduction vibration), and a waveform as shown in FIG. 4 (al) is obtained.

What about this? , F I: T The time until CJ+ turns on can be slightly delayed, and F'ETQ+, Q
While retaining the 4u point of the conventional circuit that can prevent t from turning on at the same time, the gate bias becomes deep within a short period of time after turning on, and the on-resistance increases immediately after turning on, as shown in Figure 4 (b). It can be kept small. Therefore, a switching operation with no loss of 1 (squid) is possible.

Therefore, the above embodiment can be used as is in the output stage of a class D amplifier.

Further, although the above example shows an example in which the source is common, a circuit in which the drain is common, as shown in FIG. 5, can produce the same effect. In addition, as shown in Fig. 46, the train and source of the same polarity (P channel) FET Ql, (h are connected to output terminal 2, and the FET
The configuration may be such that the source of QI is connected to the negative power supply 3, and the drain of Ei'E'1'Q2 is connected to the positive ttj,'iJ:F,5, respectively.

Furthermore, an example of use in a switching power supply is shown in FIG.

FETQ by sub-transformer 1-1.

and Qt are turned on alternately, and the load 6 is driven by the main transformer T.

In this example as well, the above-mentioned drive circuit is used to prevent F E T Ql and Qt from being turned on at the same time.

Although this example shows a push burqa type power supply, the same concept can be used with other systems as well.

Further, although the above example describes the case where a FET is used, a transistor may be used, and as long as inter-electrode capacitance is utilized, it is within the scope of the present invention.

As described above, the present invention is configured to utilize attenuation imaging due to resonance between the interactive element used in the drive circuit and the electrode contact of the switching element, so that the on-resistance is reduced immediately after turning on. can be done, and
Since a pair of switching elements are not turned on at the same time, an efficient switching circuit can be realized.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a conventional switching circuit, and FIG. 2 is a diagram showing an example of waveforms to explain the operation of the conventional circuit.
FIG. 3 is a circuit diagram showing an embodiment of the present invention, FIG. 4 is a diagram showing waveform examples for explaining the present invention in detail, and FIG. 6
．． FIG. 7 is a circuit diagram showing another embodiment of the present invention. Qs, Qt...FET R,, R,...Resistance, % D,...Diode Ll, L2...Induct tape element patent applicant Pioneer Corporation Company Figure 2 Figure 7

Claims (1)

[Claims] a semiconductor element for switching operation; and 4 of the semiconductor elements.
An input terminal for applying a signal for controlling non-conduction, a diode connected between the semiconductor element and the input terminal in a direction to prevent conduction of the semiconductor element, and a resistor connected in parallel with the diode. and induct tape element 1
1. A switch element drive circuit comprising: a tI column circuit.