JPS5854873Y2 - Controlled transistor conversion circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a controlled transistor conversion circuit that controls the output of a transistor conversion circuit such as a blocking oscillation circuit or a ringing choke converter.

A typical circuit example of a transistor conversion circuit, as shown in FIG. 1, includes a power supply 1, a resistor 2, a capacitor 3.
It is composed of a load resistor 8, and by changing the winding ratio of the transformer 5, an arbitrary voltage can be applied to the load 8.

The circuit in which an output control function is added to the circuit shown in FIG. 1 is as shown in FIG.
By applying a positive voltage through the resistor 10, the impedance between the collector and emitter of this transistor 11 is lowered, and a part of the signal current applied to the base of the transistor 4 is bypassed to reduce the base current of the transistor 4. , the collector current of the L-transistor 4 can be reduced to arbitrarily control the output applied to the load resistor.

The circuit shown in FIG. 3 connects the Zener diode 12 to the base of the transistor 11 and the cathode of the diode 6 to keep the output voltage applied to the load 8 constant. This prevents the output voltage from changing due to fluctuations.

That is, when the output voltage becomes larger than a predetermined value, the Zener diode 12 becomes conductive, and the collectors of transistors 1 to 11,
Since the impedance between the emitters decreases and the base current of transistor 4 is bypassed to transistor 11, the collector current of transistor 4 decreases.
The output decreases, and as a result, the load voltage can be suppressed from becoming larger than a predetermined value, and the voltage applied to the load 8 can be made constant.

The conventional constant voltage output converter configured in this manner has the following drawbacks.

First, when a relatively high input voltage of 3 V or more is applied from the power supply 1, the number of turns of the collector winding 5□ of the transformer 5 is made larger than that of the base winding 52.

Further, when the input voltage from the power supply 1 is less than 3V, the number of turns in the collector winding 5□ is approximately the same as or larger than the number of turns in the base winding 5□.

Therefore, for voltage control, the base of transistor 4,
Bypassing the AC signal applied between the emitters with a low impedance between the collector and emitter of the transistor 11 corresponds to a short circuit of the base winding 5□ of the transformer 5, so the primary winding 5 of the transformer 5 , and the secondary winding 53
A disadvantage is that a portion of the electromagnetic energy that should be given to the circuit is dissipated, reducing the efficiency of the circuit.

This tendency is particularly noticeable in circuits with low input voltage specifications.

Figure 4 shows the equivalent circuit of Figure 3, where the signal source 1
3 to the primary winding 5 of the transformer 5 should all pass through the secondary winding 53 of the transformer 5 and be given to the load resistor 8, but the winding 52 of the transformer 5 3 and the impedance 14, a part of the signal is consumed in the circuit of the winding 52.

This consumption loss W is proportional to where the number of turns of the winding 5 is nl and the number of turns of the winding 52 is n2.

This Z is the sum of the impedance of the capacitor 3 and the impedance 14, and this corresponds to the sum of the impedance between the collector and emitter of the transistor 11 and the impedance of the capacitor 3 in FIG.

From this equation, it can be seen that the loss increases as the number of turns of the winding 52 of the transformer 5 increases.

Note that the bypass function of the transistor 11 includes: (1) bypassing the DC base bias current applied to the oscillation transistor 4 via the resistor 2; and (2) bypassing the DC base bias current that is generated in the base winding 52 of the transformer 5. It can be said that the two functions are to bypass the AC signal that is returned and to bypass the returning AC signal, and that both functions work together to control the output.

In order to eliminate the drawbacks of the conventional example described above, the present invention is a controlled transistor conversion system that enables output control without reducing conversion efficiency while setting the number of turns to supply sufficient base drive voltage at low input voltages. It provides a circuit.

That is, the present invention provides an intermediate tap at 5° of the base winding,
By connecting the collector of the transistor 11 to this intermediate tap, the amount of DC base bias current (2) bypassed is the same as when no tap is provided, but the AC signal (2) is bypassed. By appropriately setting the amount using taps, loss can be reduced without causing any trouble in output control.

Hereinafter, embodiments will be described in detail with reference to the drawings.

FIG. 6 shows a circuit of one embodiment of the present invention, and FIG. 5 shows an equivalent circuit around the transformer. The same reference numerals as in FIG. 3 indicate the same parts. In this embodiment, an intermediate tap is taken out from the winding 52 of the transformer 5, and this intermediate tap is connected to the collector of the transistor 11.

The further the center tap is located from the base side of the transistor 4, and the closer it gets to the side of the capacitor 3, the smaller the loss becomes.However, when the input voltage increases or when the load resistance 8 is light, the output control function decreases. and the output will become uncontrollable.
This intermediate tap must be placed at an appropriate location.

When the tap position of the winding 5° is determined to be the number of turns n divided by the number of turns n from the system relationship, the loss W consumed in a circuit with 52 turns becomes less than that of the conventional system.

Figure 7 shows an actual application example of the present invention.
Items with the same reference numerals as those in the figures indicate the same items.

Further, when this circuit is operated at a low input voltage, typical characteristics are compared with those of the conventional example, as shown below.

As explained above, according to the present invention, in the output control of a blocking oscillator circuit or a ringing choke type converter, a reduction in conversion efficiency is prevented and sufficient voltage control characteristics are obtained, so that the The advantage is that significant effects can be obtained for voltage applications.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of the basic circuit of a blocking oscillation circuit or ringing choke converter, and Figure 2 is a circuit diagram of the basic circuit of a blocking oscillation circuit or ringing choke converter.
Figure 3 is a circuit diagram in which an output control mechanism is added to the circuit in Figure 1, Figure 4 is an equivalent circuit diagram around the transformer of the circuit in Figure 3. , 5th
The figure is an equivalent circuit diagram around the transformer of the embodiment of the present invention.
The figure is a circuit diagram of an embodiment of the present invention, and FIG. 7 is a circuit diagram of an example of an actual operating circuit for low input voltage. 1...Power supply, 2...Resistance, 3...
... Capacitor, 4...1 ~ Ransistor, 5.
...Transformer, 6...Diode, 7.
...Capacitor, 8 ...Load resistance, 11
...Transistor, 12...Zena diode.

Claims (1)

[Claims for Utility Model Registration] An oscillation transistor 4, at least two windings, that is, a first winding 5 connected to the collector circuit of the oscillation transistor 4, and a base of the oscillation transistor 4. a second generating an AC feedback signal to be applied;
a transformer 5 having a winding 52; and an output control transistor 11 whose impedance changes according to the output in order to control the output to the load and bypass-controls the current in the base and emitter circuits of the oscillation transistor 4. A controlled transistor conversion circuit having a control type transistor conversion circuit, characterized in that the transformer 5 is provided with an intermediate tap, and the control transistor 11 is connected between the intermediate tap and the emitter of the oscillation transistor 4. circuit.