JPS5947892B2 - blocking oscillator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a blocking oscillator circuit (blocking oscillator) that generates pulses using one transistor and a transformer.

Conventionally, this type of oscillator has a configuration as shown in FIG.

That is, a transformer TR having a primary winding N1 and a secondary winding N2 on the input side and a tertiary winding N3 on the output side is provided, and the winding start terminal of the primary winding N1 of this transformer TR is Connect the DC power supply terminal 10Vcc, while the primary winding N
The end terminal of the winding 1 is led to the collector of a transistor Q1 whose emitter is connected to the ground terminal E of the DC power supply.

Furthermore, the base of this transistor Q1 is connected to the secondary winding N
2 through the power terminal 10V.

It is connected to the connection point between resistors R1 and R2, which are connected in series between 0 and earth terminal E.

Between the emitter of transistor Q1 and secondary winding N2,
A capacitor C1 is provided which, together with resistors R, R2, defines the oscillation frequency of this oscillator.

In addition, the primary winding N1 of the transformer TR is connected to a power terminal.

A diode D1 is connected in parallel with C in a reverse direction.

This diode D1 can be replaced with a resistor R3 and a capacitor C2 with equal restrictions.

Note that since the transformer TR is connected to the collector load of the transistor Q1, the diode D1 absorbs the spike voltage induced when the collector current Ic is cut off, and serves to prevent deterioration of the transistor Q1.

Note that in this figure, terminals indicated by symbols a and b are output terminals of this oscillator, and are normally connected to a rectification and smoothing circuit including a diode D2, a capacitor C3, and the like.

The operation of the blocking oscillator configured as described above will be explained.

When the power supply voltage +VCC is applied, a base current 8 flows into the transistor Q1 through the resistor R1, and as a result,
Collector current ■ through the primary winding N1 of transformer TR
.

begins to flow, but this collector current■.

Due to the increase in , a positive voltage V, (
The polarity of the transformer TR is set so that VB=M-dIc/dt (M is the mutual inductance of the transformer TR) is added.

Therefore, the transistor Q1 becomes conductive (on) due to the positive feedback effect caused by the positive voltage 8.

On the other hand, when charge is accumulated in the capacitor C1 and the voltage VB decreases, the collector current becomes ■.

decreases, and a negative voltage is now applied to the base of transistor Q1, which transitions to the cutoff (off) state.

In this state, a voltage (cB=n
-Vo and H are applied with a turns ratio N2:Nl).

Since the transistor Q1 is in the off state, the voltage CB is discharged to the power supply through the resistors R1 and R2, and when it reaches 0, the transistor Q1 is turned on again in the same way as above. and time constant τ due to capacitor C1 and turns ratio n of transformer TR
Pulses are generated from output terminals a and b with an oscillation period T defined by .

The blocking oscillator described above is the transistor Q1
Collector current flowing into■.

In this configuration, a diode D1 is connected in parallel to the primary winding N1 in order to absorb the spike voltage induced in the transformer TR when the transistor Q1 is turned off and to stabilize the transistor Q1.

However, during reverse bias, the operating speed of transistor Q1 is delayed due to the capacitive component of diode D1.

This inevitably increases the oscillation period T, leading to an increase in the size of the transformer TR.

An object of the present invention is to provide a blocking oscillator that is compact and capable of high-speed operation by solving these problems.

A blocking oscillator according to the present invention includes a transistor whose emitter is grounded, a transformer having a first winding that conducts a current from a DC power source to the collector of the transistor, and the transistor is connected in series and placed between the base and emitter of the transistor. a second winding of the transformer and a capacitor, the operation of the transistor is controlled by a positive feedback effect of the voltage induced in the second winding of the transformer and charging and discharging of the capacitor; In a blocking oscillator that outputs a pulse through a winding of a first resistor, a first resistor having one terminal connected to the base of the transistor and the other terminal connected to the capacitor; A Zener diode having an anode connected to a terminal, a second resistor disposed between the cathode of the Zener diode and the DC power supply, and a diode disposed between both ends of the second winding. Features.

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 shows the first blocking oscillator according to the present invention.
FIG. 2 is a circuit configuration diagram showing an embodiment of the present invention.

As shown in FIG. 2, the oscillator according to this embodiment is
A transformer TR having a primary winding N1 and a secondary winding N2 at the input end and a tertiary winding N3 at the output side is provided, and the winding start terminal of the primary winding N1 of this transformer TR is Power terminal of DC power supply ■.

0, while the end terminal of the primary winding N1 is connected to the collector of a transistor Q1o whose emitter is connected to the ground terminal E of the DC power source.

Further, a resistor R1° is connected in series between the base of the transistor Q1o and the earth terminal E.

Place R13.

At the connection point of resistors R1゜ and R13, there is a power supply terminal ■.

The anode of a Zener diode DZ, whose cathode is connected to the other terminal of a resistor R1□, one terminal of which is connected to 0, is connected to the other terminal of the resistor R1□.

Further, a capacitor C1□ is connected between the connection point of the resistors R1□ and R15 and the secondary winding N2 of the transformer TR.

Further, the cathodes of a diode D11 and a Zener diode DZ2 whose anodes are connected in series are connected between both terminals of the secondary winding N2.

Note that symbols a and b are output terminals of this oscillator, which are connected to a rectifier, smoothing circuit, etc. as in the conventional case.

The operation of the blocking oscillator configured in this way is as follows.

In other words, the power supply voltage +vo. is applied, resistor R10
, a base current 8 flows into the transistor Q1o through the Zener diode DZ1 and the resistor R13.

As a result, collector current ■ flows through the primary winding N1 of the transformer TR.

begins to flow, but this collector current■.

When increases, a positive voltage ■
The polarity of the transformer TR is set so that 8 is added.

In other words, the collector current ■ flowing through the primary winding N1.

As a result, an induced electromotive force (VB) is induced in the secondary winding N2.

Due to the positive feedback effect of this voltage VB, the transistor Q1
o is turned on.

On the other hand, when charge is accumulated in the capacitor C1 and the base voltage VB decreases, the collector current Ic decreases, and a negative voltage is now applied to the base of the transistor Q1o, causing the transistor Q1 to transition to an off state. .

A voltage CB is applied between the base and emitter of the transistor Q1o due to the charge of the capacitor C1.

However, since the transistor Q1o is in the off state, this voltage CB is discharged to the power supply through the resistor R1□, and when it becomes 0■, the transistor Q1o is turned on again.

Thereafter, by repeating this operation, the resistors R10 and R
A pulse is generated at an oscillation synchronization T defined by a time constant τ caused by C12 and a capacitor C1□, and a turns ratio n of the transformer TR.

A blocking oscillator configured in this way has a collector current I flowing into the transistor Qto.

When disconnected, the spike voltage induced by the resonant current caused by the inductance component and stray capacitance of the transformer TR is transferred to the secondary winding N2 of the transformer TR by a diode D1, which is connected in parallel with a Zener diode DZ2.
Absorb by.

In other words, the diode D1□ dissipates the excitation energy due to the spike voltage.

Therefore, the spike voltage generated at this time is not applied to the transistor Q1o.

In addition, the Zener diode DZ2 connected in parallel to the secondary winding N2 of the transformer TR mainly acts as a clamper for the voltage 8 induced in the secondary winding N2, thereby reducing the voltage VB already applied to the transistor Qio. The feedback described above is further stabilized.

Furthermore, Zener diode DZ. ■ The power supply voltage is higher than its Zener voltage.

Since the base bias of the transistor QIO is not applied unless the voltage reaches 0, unstable operation of the transistor QIO is prevented during the low voltage input period of the power supply voltage +VCC.

Since the Zener diode DZ1 forming the base bias of the transistor QIO becomes only a low resistance component when reverse biased by the power supply voltage +■Co, it does not affect the operating speed of the transistor QIO.

FIG. 3 shows the second block diagram of the blocking oscillator according to the present invention.
FIG. 2 is a circuit configuration diagram showing an embodiment of the present invention.

The blocking oscillator according to this embodiment leads the emitter of the transistor Q1o to the ground terminal E through the resistor R14, and connects the base of the transistor Q1o to the ground terminal E through the resistor R14.
Diodes D1゜, D connected in series in the forward direction between the emitters
The second embodiment differs from the first embodiment in the configuration in which 13 are arranged.

With this arrangement, the inflow collector current ■.

Even if the voltage increases, the base voltage of the transistor Q1° can be maintained at a constant level, and a constant current function can be achieved.

For example, the output terminal a of the tertiary winding N3 of the transformer TR,
Due to an abnormality on the load side connected to
If an induced electromotive force occurs in the collector current■.

Therefore, damage to the transistor Q1o can be prevented.

As described above, according to the present invention, it is possible to obtain a blocking oscillator that is small and can operate at a high oscillation cycle.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram showing an example of a conventional blocking oscillator, and FIGS. 2 and 3 are circuit configuration diagrams showing first and second embodiments of the blocking oscillator according to the present invention. TR...transistor, QIO...transistor, DZl. DZ2... Zener diode, D1□~D1
3...Diode, C11...Capacitor, R11-R14...Resistor, a, b
...Output terminal.

Claims (1)

[Claims] 1 A transistor whose emitter is grounded, a transformer having a first winding that conducts current from a DC power source to the collector of this transistor, and a second winding of the transformer connected in series and disposed between the base and emitter of the transistor.
a second winding of the transformer and a capacitor;
The blocking oscillator controls the operation of the transistor by the positive feedback effect of the voltage induced in the winding of the transformer and the charging/discharging of the capacitor, and outputs a pulse through the third winding of the transformer. a first resistor whose terminal is connected to the capacitor and whose other terminal is connected to the capacitor, a Zener diode whose anode is connected to the other terminal of the first resistor, and between the cathode of the Zener diode and the DC power supply. A blocking oscillator comprising: a second resistor disposed at the second winding; and a diode disposed between both ends of the second winding.