JPH0334710A - Static induction transistor circuit - Google Patents

Abstract

PURPOSE:To reduce the effective on-resistance and to set an optimum power efficiency by connecting a constant voltage circuit to a prestage of static induction transistor(TR) connecting to a drive element. CONSTITUTION:It is assumed that a sufficiently small impedance is selected when suspective drive element 21, 22 are turned on. In this case, while the drive element 21 is turned on and the other drive element 22 is turned off, a voltage nearly equal to a negative voltage of a drive source 1 is applied between a gate 31 and a source 32 of a static induction TR SIT 3 and the SIT 3 is turned off. Moreover, while the drive element 21 is turned off and the other drive element 22 is turned on, the SIT 3 is turned on. The gate voltage of the SIT 3 shows a waveform where the voltage level at turn-on is constant depending on the constant voltage characteristic of a diode 4a. Thus, the effective on-characteristic of the SIT 3 is lowered more, small voltage loss is enough and the power efficiency is improved.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention is directed to improvements in electrostatic induction transistor circuits used, for example, in power amplification stages or modulation amplification stages of medium-wave or short-wave broadcasters. Regarding.

(Prior Art) Generally, a static induction transistor
When using a translator (hereinafter abbreviated as SIT) as a high-frequency switching element, to turn the SIT off (opp), apply a negative bias voltage of several tens of volts (V) to the gate terminal, and then turn it on (opp).
N), it is necessary to raise the gate voltage from a negative voltage to close to zero V.

The resistance (on-resistance [1)] characteristics with respect to the gate voltage when turning on the IIT are as shown in Figure 7, and as the voltage approaches zero V from a negative voltage, the on-resistance (value) decreases, and as the voltage approaches zero V, the on-resistance (value) decreases.
Even if the voltage exceeds 1, the resistance value continues to decrease.

Therefore, in order to reduce power loss due to the on-resistance of the SIT, the gate voltage is often used in a range from zero (V) to a slightly positive voltage when the SIT is on.

On the other hand, when the switching frequency is relatively low, the SI
Although there is no particular problem in the driving operation of the T, when trying to perform a switching operation in a high frequency region, the input capacitance value of the SIT becomes a problem and cannot be ignored. usually,
Considerable driving power is required to charge and discharge the input capacitance of the SIT through switching operations. On the other hand, the input capacitance value of the SIT increases as the gate voltage increases, as shown in FIG. 8, where the change in capacitance value with respect to the gate voltage is expressed logarithmically in the vertical axis direction. Therefore, as described above, on the one hand, in order to reduce power loss due to on-resistance in switching operation, the higher the gate voltage is, the more driving power is required to charge and discharge the human capacitance. Therefore, when the switching frequency becomes high, the SIT drive power requires a large amount of power, which is a fraction of the output power, and when the SIT is configured as a switching amplifier, it becomes a problem in terms of power efficiency. Ta.

The 317 circuit, which uses a conventional SIT as a high-frequency switching amplification element, adopts the circuit configuration shown in Figure 9 in order to reduce the driving power, and reduces the gate voltage to zero V at most.
It is set as below and is often not operated in the positive voltage region.

That is, FIG. 9 shows a conventional 317 circuit, which includes a driving power source l made of a negative voltage power source, a pair of driving elements 21.22 connected to this driving power source l, and this driving element 21.2.
It consists of 5IT3 connected to 2 and 5IT3. In addition, 23
is an element drive circuit that drives the drive elements 21 and 22,
Here, the element drive circuit 23. The driving elements 21 and 22 are referred to as S
It is assumed to be IT drive circuit 2.

In the 317 circuit shown in FIG. 9, driving element 21.
If the impedance of 22 is sufficiently low, the output impedance of the SIT drive circuit 2 can be made sufficiently low, so the voltage of 5IT3's gate 31 at this time is in the range from negative voltage to zero, as shown in Figure 1O. The power loss of the 5IT3 itself can be minimized.

However, in the high switching frequency region, the first
Even if you try to drive 5IT3 with the gate voltage shown in factor O, the driving power will be extremely large due to the influence of the gate input capacitance as described above, and when considering the overall power efficiency of the entire SIT circuit. cannot necessarily be said to be the best. Therefore, in reality, as shown in FIG. 11, the output impedance of the drive circuit 2 is large to some extent, and the power efficiency is maximized when the gate drive waveform is such that the amplitude of the gate voltage does not reach 0 V when turned on. There is a point.

The reason for this is that when the SIT gate drive voltage decreases, the drive power decreases, and conversely, when the drive voltage decreases, the resistance when the SIT is on increases and the on-resistance loss increases. This is because in a drive voltage range slightly below V, the amount of reduction in drive power exceeds the amount of on-resistance loss, and as a result, the point at which the overall power efficiency is maximized exists below zero V.

However, even with the 317 circuit in which the amplitude of the drive voltage is set in the region where the power supply efficiency is the best by adjusting the output impedance of the drive circuit 2, the gate voltage of the 5IT3 will not be as shown in FIG. As shown, it is not constant but changes during the ON period (T). For this reason, the on-resistance value of the 5ITI also changes during the on-period (T), and especially for the 317 circuit as a high-frequency switching amplifier that operates in class D, the on-resistance is large when the maximum current flows. However, there is a drawback that the best power efficiency that can be obtained with a constant driving power cannot necessarily be obtained.

In this way, in the conventional 317 circuit, the SIT on period (T
), it was difficult to obtain the best power efficiency.

(Issue 8 to be solved by the invention) In the conventional 317 circuit, the SIT drive circuit in high-frequency switching operation is always in the best condition because the SIT has a large human capacitance and the resistance value changes during the on period. The drawback was that power efficiency could not be achieved.

This invention does not increase the drive power of SIT,
It is an object of the present invention to provide a 317 circuit that can reduce the effective on-resistance of an SIT and improve power efficiency.

[Structure of the Invention] (Means for Solving the Problems) A static induction transistor circuit according to the first invention includes a driving power source, a constant voltage circuit connected to the driving power source, and a constant voltage circuit connected to the constant voltage circuit. It is characterized by comprising a driving element and a static induction transistor connected to the driving element.

The static induction transistor circuit according to the second invention includes a driving power source, a driving element connected to the driving power source, a constant voltage circuit connected to the driving element, and a capacitor connected to the constant voltage circuit. A transistor.

(Function) The static induction transistor circuit according to the present invention has a constant voltage circuit connected to the front stage of the capacitance transistor.
It is possible to clamp the drive voltage of the SIT to a voltage level that does not reach zero volts.

As a result, it is possible to keep the voltage value constant during the SIT on period in the region of relatively low output impedance, reducing the effective on resistance without increasing the SIT drive power and achieving optimal power efficiency. Can be set.

(Embodiments) Hereinafter, embodiments of the capacitance transistor circuit according to the present invention will be described in detail with reference mainly to FIGS. 1 to 6.

Components that are the same as those of the conventional 817 circuit shown in FIG. 9 are designated by the same reference numerals, and detailed description thereof will be omitted.

That is, FIG. 1 is a circuit diagram showing a first embodiment of the circuit of the present invention, in which a driving power source 1 consisting of a negative power source, a constant voltage circuit 4 connected to this driving power source, and a constant voltage circuit 4 connected to this driving power source A pair of connected driving elements 21.22, and this driving element 21.22.
It consists of 5IT3 connected to 22.

The constant voltage circuit 4 shown in FIG. 1 uses a diode 4a, and has a constant voltage characteristic approximately based on the F characteristic of the diode.

Now, assuming that drive elements 21 and 22 are selected whose respective impedances are sufficiently small when they are on, the period during which one drive element 21 is on and the other drive element 22 is off is equal to the gate of 5IT3. (31)・Sauce (3
2) (Reference) A voltage approximately equal to the negative voltage of the drive power supply 1 will be applied between them, and 5IT3 will be turned off.

Also, when one drive element 21 is off and the other drive element 22
During the period in which the gate (31) of the 5IT3 is turned on, a negative voltage is applied to the gate (31) of the 5IT3 from zero V by the VF voltage of the diode, and the 5IT3 is turned on. As shown in FIG. 2, the gate voltage of 5IT3 at this time draws a waveform in which the voltage level when turned on is constant due to the constant voltage characteristics of the diode 4a. That is, the middle point in time (T) of the on period (T) of 5IT3
The 5IT3 gate voltage in 1) is due to constant voltage characteristics,
Since the waveform is closer to zero than the waveform in the conventional circuit shown in Figure 9, the effective on-resistance of 5IT3 is lower and power loss is smaller, improving the overall power efficiency of the 817 circuit. .

At this time, in comparison with FIGS. 2 and 11, the minimum level (L) and maximum level (L) of the drive voltage waveform are
11) are equal, the driving power required for charging and discharging the human power capacitance of SIT' remains the same.

However, for example, if the SIT having the characteristics shown in FIG. 7 is operated as a class D voltage amplifier, the gate voltage of 5IT3 at time (1) in the middle of the on period in FIGS. 2 and 11 is -0.
, 3v and 10, 6v, the on-resistance at the center point is less than 1/2 of the voltage waveform in Fig. 11 when the voltage waveform is in Fig. 2, and the SIT on-resistance loss can be reduced to 1/2 or less.

Further, in this first embodiment, a diode is used as the constant voltage circuit, but the same effect can be obtained by replacing the diode with a battery or a DC power source.

FIG. 3 is a block diagram showing a second embodiment of the circuit of this invention.
Instead of the constant power supply circuit using the diode 4a shown in FIG.
A resistor R2 is connected between the negative terminal 1a of the 5IT3 and the gate terminal 31 of the 5IT3.

According to the circuit shown in FIG. 3, the on/off duty (duty
) ratio makes the voltage (El) between both ends of the resistor R1 constant.

Also, this voltage El causes the capacitance value of the capacitor C1 to increase to 5
If the value is much larger than the input capacitance of IT3, and the time constant determined by capacitor C1 and resistor R1 is sufficiently large with respect to the period of the switching frequency,
This capacitor C1 has the same function as the constant voltage circuit shown in FIG.

That is, the drive element current that flows while the drive element 22 is on changes in a pulse-like manner as shown in FIG. Any circuit or element can be similarly used as a constant voltage circuit.

In addition, in FIG. 3, the resistor R2 is connected to the drive power supply l and 5IT.
Although the two driving elements 21 and 22 forming the driving circuit 2 are connected in parallel to the series circuit of the two driving elements 21 and 22, the same function can be achieved and the object can be achieved.

Furthermore, FIG. 5 shows a third embodiment of the circuit of the present invention, and the difference from FIGS. Voltage circuit 4
is inserted and connected. This SIT circuit can also maintain the gate voltage level at a constant value when 5IT3 is on due to the action of the constant voltage circuit 4, so it is possible to obtain the same effect as the circuits in FIGS. 1 and 3. It is.

Further, FIG. 6 is a circuit diagram showing a fourth embodiment according to the present invention, in which, similarly to the embodiment of FIG. 5
By inserting it between the gate terminal 31 of the IT3, the gate voltage level when the 5IT3 is turned on can be maintained at a constant value, and the best power efficiency can always be obtained.

[Effects of the Invention] As described above, the electrostatic induction transistor circuit according to the present invention lowers the effective on-resistance of the SIT without increasing the drive power of the SIT drive circuit, and improves the power efficiency as a high frequency switching amplifier. This is something that can be improved and has a great practical effect.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the electrostatic induction transistor circuit according to the present invention, FIG. 2 is a characteristic diagram showing the SIT gate voltage characteristics of the circuit shown in FIG. 1, and FIG. 3 is a circuit diagram of the circuit according to the invention. FIG. 4 is a waveform diagram of the current flowing through the drive element 2 of the circuit shown in FIG. 3, and FIG. 5 is a circuit diagram showing a third embodiment of the circuit of the present invention. FIG. 6 is a circuit diagram showing a fourth embodiment of the circuit of the present invention, and FIG.
Figure 8 is a characteristic diagram showing the on-resistance with respect to the gate voltage of SIT, Figure 8 is a characteristic diagram showing the gate input capacitance with respect to the gate voltage of SIT, Figure 9 is a circuit diagram showing a conventional SIT circuit, Figures 1O and 11. Each figure is a gate voltage waveform diagram for explaining the operation of the SIT shown in FIG. 9. 1... Drive power supply, 2... Element drive circuit,
21, 22... Drive element, 3... SIT. 4... Constant voltage circuit.

Claims (2)

[Claims] (1) A static induction transistor including a driving power source, a constant voltage circuit connected to the driving power source, a driving element connected to the constant voltage circuit, and a static induction transistor connected to the driving element. circuit. (2) A static induction transistor comprising a driving power source, a driving element connected to this driving power source, a constant voltage circuit connected to this driving element, and a static induction transistor connected to this constant voltage circuit. circuit.