JPS5850042B2 - Relaxation oscillator using high frequency excitation - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an oscillator that generates relaxation oscillations by changing an active element from an active state to a cutoff state using an intermittent high-frequency voltage.

Conventionally, this type of relaxation oscillator uses a transformer to turn on and off the transistor by changing the phase of the output voltage and feeding it positive feedback to the input side to saturate the transistor.

This is what is called a blocking oscillator.

There is also a relaxation oscillator as an astable circuit using two transistors.

Each circuit diagram is shown in FIG. 1 and FIG. 2. These conventional relaxation oscillators have three stages: an active state, a saturation state, and a cutoff state.

The present invention provides a relaxation oscillator which provides relaxation oscillation by turning on and off an active element using a high frequency voltage, and whose frequency changes over a wide range depending on the power supply voltage without requiring special adjustment.

The present invention will be explained below with reference to the circuit diagram shown in FIG.

In this embodiment, a transistor having three terminals will be described as an example of a semiconductor active element.

A capacitor C1 is connected between the base and emitter of the active element, and a resistor R1 is connected to the power supply terminal ■.

and the base, and resistor R2 to terminal V.

and the collector, a capacitor C3 and a coil L3 as an inductance are connected in series between the base and the collector, and a capacitor C2, a capacitor C4 and a coil L4 as an inductance are connected in series. By connecting these in parallel between the collector and emitter, a relaxation oscillation circuit using high frequency excitation is constructed.

In this circuit, C1 determines the high frequency oscillation frequency.
They are C2 and L3.

That is, the oscillation frequency f is calculated using the following formula: % Formula % This formula: C1=250PF1 C2=500PFL3=
Substituting 0.3 μH gives 23 MHz in f.

FIG. 4 shows the high frequency voltage waveform.

As is clear from this figure, the frequency is approximately 23 MHz.

This waveform can also be seen between the collector and emitter and between the base and emitter.

Assuming the waveform size is vcg for the former and ■ for the latter, it is V-shaped 0.15 volt (P-P'), VBB: 0
．． 2 volt (P P).

However, this is the case where the power supply voltage (■o) is set to 20 volts.

In other words, the voltage generated between the base and emitter increases.

This change in base-emitter bias voltage dVBE
As a result of the charge change dQB occurring at the base, the diffusion capacitance cd=dQB/dVBE can be considered.

The above phenomenon is considered to be a state in which high-frequency oscillation of the transistor is occurring, so the operation of the transistor is in the active region.

As a result, a high frequency voltage is applied to the base region as an excitation voltage, causing the transistor to change from an active state to a cutoff state.

In this cutoff state, it is considered that the high frequency voltages generated between the base and emitter and between the collector and emitter as well as the pulse waveforms coincide well, so that they enter the cutoff region at the same time.

FIG. 5 shows observed waveforms for the active region and cutoff region.

As is clear from the waveform at the bottom of Figure 5, the base-emitter voltage attenuated from the positive region to the negative region by the high-frequency voltage reverse biases the base-emitter of the transistor, making it impossible to maintain high-frequency oscillation. .

The transistor is therefore cut off.

The high frequency oscillation stops in the cut-off state, and charging and discharging phenomena occur as a result of the action of the external circuit elements of the transistor, and the transistor returns to the active state again, and the above-mentioned state is repeated as the next operation.

Therefore, it can be said that the present invention is fundamentally different from the conventional ones in that it utilizes a high frequency voltage.

The so-called high frequency voltage is about 23M as mentioned above.
It is a high frequency such as Hz or 45 MHz, and the waveform between the collector and emitter generated when L4 and C4 are removed in FIG. 3 is shown in FIG. 4, indicating that it is a sine wave.

If L4 and C4 are connected when this high frequency oscillation voltage is generated, a relaxation oscillation waveform as shown in FIG. 5 is obtained.

In FIG. 5, the upper part shows the waveform between the collector and emitter, and the lower part shows the waveform between the base and emitter.

Figure 6 shows an enlarged view of the falling part of the relaxation oscillation waveform. The upper part is the waveform at both ends of C4 in Figure 3, and the lower part is the base-emitter waveform included in the shaded part of the high-frequency voltage. It is.

The waveforms at both ends of C4 exclude high frequency components.

In FIG. 3, compared to the conventional circuit elements, relaxation oscillation occurs without any special adjustment required, and the frequency can be changed over a wide range by changing the power supply voltage.

The frequency is changed from about 2011z to about 50KHz, and the power supply voltage is changed from about 8V to about 30V.

The relationship is shown in Figure 7.

On the other hand, it was confirmed that oscillation occurs with good reproducibility even when a voltage exceeding the maximum rating of the transistor is applied, and the frequency is 50KH.
It can be more than z.

As for the output voltage, as shown in FIG. 8, even if the power supply voltage is increased, the amplitude of the output voltage does not change much.

Therefore, it is advantageous to connect an amplifier or the like to the next stage.

Furthermore, the voltage across C4 shown in FIG. 6 can be used as a DC component.

Next, we will show that the oscillation conditions are extremely different from those in ordinary transistors.

First, the base current flows 1500 to 2000 times the normal amount, and the collector current also flows 150 to 500 times.

Fortunately, these currents do not flow continuously and do not cause damage to the transistor.

Since this is a unique phenomenon, appropriate oscillation conditions cannot be determined easily.

However, what can be said is that it is desirable that the high frequency oscillation frequency be 20 MHz or higher.

For example, when the inductance L is small, high frequency oscillation of 45 MHz occurs, but the period (frequency) of the relaxation oscillation changes significantly with changes in the power supply voltage.

Specifically, it shows a change from 20Hz to 50KHz.

In the case of 23 MHz, it shows a change from 80 Hz to 5 KHz.

Also, the larger R1 is, the better.

The reason why it is better to have a higher high-frequency oscillation frequency is because it is considered that the diffusion capacitance cd=dQB//dVBE increases.

The equivalent circuit in the active region of the transistor is one in which a diffused resistor rd and a base diffused resistor rb are connected in series in parallel to Cd.

Resistor R1 at the bottom of the circuit and Cd, rd in the equivalent circuit
The conditional expression is as follows.

Calculate the oscillator using this formula.

In the case of 23■Z, the measured waveform shows that during the forward bias period between the base and emitter, rd=20KJ7. Cd=250PF
So l lrd 7 Cdl l:27 Q.

During the reverse bias period between base and emitter, rd=IM
Q.

Cd=2X10'PF and l 1 rd/ccti
It becomes 0.35g in 1.

R1=500! Since Q, the above equation is fully satisfied.

It is thought that Cd becomes even larger at 45 MHz.

In the above equation, since w and Cd become larger, it is clear that the conditions are more advantageous than 23 MHz.

For example, using the above rd and Cd values as they are, 45 MH
Substituting z, it becomes 1lrd/Cd in the forward bias period.
1l cow 14g1 1rd//C in reverse bias period
dl l=:=o, 18 (becomes j.

If we take into account that Cd becomes larger, the value becomes even smaller, which is more advantageous.

As mentioned above, this is a relaxation oscillator with a new mechanism in which a high-frequency oscillation voltage is generated using an active element such as a transistor, and the active element is turned on and off using the high-frequency voltage, and the frequency range is wide depending on the power supply voltage. This oscillator has the advantage of being able to be changed to

The present invention is a very important invention because it can be used in pulse circuits for televisions and the like.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of a transistor blocking oscillator using a pulse transformer, diode, etc. Figure 2 shows an astable circuit (multivibrator). FIG. 3 is a circuit diagram used in the present invention. Figure 4 shows the high-frequency oscillation waveform observed between the collector and emitter, a sine wave with a frequency of 23MHz. Horizontal axis X = 0.02 μS/div, vertical axis Y = 0.2 V
/ div, power supply voltage ■. =6 Volt. FIG. 5 shows relaxation oscillation waveforms produced by the circuit of the present invention. The top is the observed waveform between the collector and emitter, and the bottom is the observed waveform between the base and emitter. Horizontal axis X = 0.2 ms/d iv. Vertical axis Y=1v
/div1 power supply voltage V □ = 20 Vol t □ Figure 6 is an enlarged waveform of the falling part of the relaxation oscillation waveform. The top is the waveform observed at both ends of C4, and the bottom is the observed waveform between the base and emitter. Horizontal axis X = 0.5μS/aiv, vertical axis Y = IV/div,
Power supply voltage V □ = 20 Vol t □ Fig. 7 is a diagram showing the relationship between frequency and power supply voltage. FIG. 8 shows the magnitude of the amplitude of the output voltage with respect to the power supply voltage. In the figure, the symbol indicates the upper limit of the output voltage, and the symbol ■ indicates the lower limit of the output voltage.

Claims (1)

[Claims] 1. A capacitor C1 is connected between the base and emitter of one transistor, and one terminal V of the power supply. Connect a resistor R1 between the terminal and the base. A resistor R2 is connected between the collector and the collector, a series circuit consisting of an inductance L3 and a capacitor C3 is connected between the collector and the base, a capacitor C2 is connected between the collector and the emitter, and a capacitor C4 and an inductance L4 are connected in parallel with this. A relaxation oscillator using high frequency excitation, which is formed by connecting a series circuit consisting of the following, connecting the connection point of L4 and C4 to the output terminal, and connecting the emitter to the other terminal of the power supply.