JPS58224561A - Switching type constant-voltage circuit - Google Patents

Abstract

PURPOSE:To improve the efficiency of a constant-voltage circuit by maintaining the base current substantially constant to the variation in the input voltage of a transistor which performs switching operation. CONSTITUTION:The first transistor TR1 and a smoothing circuit 3 are connected in series between a DC power source 1 and a load 2. A reverse voltage absorbing diode D1 is connected between the first transistor TR1 and the smoothing circuit 3. The emitter of the third transistor TR3 is connected to the base of the first transistor TR1. A series circuit which has a resistor R6 and the second transistor TR2 is connected to the base of the third transistor TR3. The collector of the second transistor TR2 is connected to the connecting point 8 of a coil 6 and a capacitor 7. Since the base current of the first transistor TR1 flows through the emitter and the collector of the third transistor TR3 to the load 2, its efficiency is improved without waste.

Description

[Detailed description of the invention] The present invention relates to a switching type constant voltage circuit.

Referring to FIG. 1, conventionally, a first transistor TRI and a smoothing circuit 3 are connected in series between a DC power supply l and a load 2, and a second transistor TRI controls the operation of the first transistor TR1. Transistor TR2 is controlled by control pulse generation circuit 4.

In such conventional technology, the first transistor TRI
Since the base current iB of flows through the second transistor TR2, the base current IB of vJ1 transistor TRI flows through the second transistor TR2.
is diverted, and the efficiency drops to about 80%.

In order to reduce such shunt current IB and improve efficiency, as shown in FIG.
It is simply conceivable that the third transistor TR3 is connected in a Darlington manner. In the circuit of FIG. 2, the base current IB is reduced by 1/hf8, where hfe is the current amplification factor of the third transistor TR3, and the efficiency should be improved. However, when the third transistor TR3 becomes conductive in response to the control pulse from the control pulse generating circuit 4, the collector-emitter voltage VCE of the third transistor TR3 becomes approximately 0. this is,
This means that in the first transistor TRI, the collector potential VC and the base potential VB are approximately equal.

Here, the emitter potential VE is VE=VB+0.8 to 0.9
Therefore, a potential difference of 0.8 to 0.9 .mu. is created between the collector and emitter of the first transistor TRI. Therefore, the loss in the first transistor TRI increases, and as a result, the efficiency does not improve.

The present invention aims to solve the above-mentioned technical problems and provide a switching voltage circuit with improved efficiency.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 3 is an electrical circuit diagram of one embodiment of the present invention.

A first transistor TR is connected between the DC power supply 1 and the load 2.
I and the smoothing circuit 3 are connected in series.

A reverse voltage absorbing diode D1 is connected between the first transistor TRI and the smoothing circuit 3. Further, the smoothing circuit 3 includes a coil 6 and a capacitor 7.

The first transistor TRI is a PNP transistor, and the emitter of the third transistor TR3, which is a PNP transistor, is connected to the base of the first transistor TRI. The emitter of the third transistor TR3 is also connected to the emitter of the first transistor TRI via a resistor R1, and the base of the third transistor TR3 is connected to the emitter of the first transistor TRI through a resistor R1.
, R2 (connected to the emitter of the first transistor TRI via i7. Furthermore, according to the present invention, the collector of the third transistor TR3 is connected to the connection point 8 between the coil 6 and the capacitor 7 in the smoothing circuit 3.

At the connection point 9 between the smoothing circuit 3 and the load 2, resistors R3 and R
A series circuit consisting of 4 and R5 is connected.

The control pulse generating circuit 4 is connected to the resistor R4 in a freely connected position. Therefore, the control pulse generation circuit 4 can detect the voltage corresponding to the potential at the connection point 9 and can arbitrarily change the set voltage.

A series circuit consisting of a resistor R6 and a second transistor TR2 is connected to the base of the third transistor TR3. 'S2 transistor 'I'R2 is an NPN transistor, and a control pulse from control pulse generation circuit 4 is applied to its base.

As described above, by connecting the collector of the second transistor TR2 to the connection point 8 between the coil 6 and the capacitor 7, the collector potential of the third transistor TR3 is lower than the collector potential VC of the first transistor TRI when the third transistor TR3 is conductive. V'C becomes lower. Therefore, as described in FIG. 2 above, the first transistor TR
The potential difference of 0.8 to 0.9 V between the emitter and collector of I does not decrease, and the potential difference between the emitter and collector becomes almost zero when the first transistor TRI is conductive.

Furthermore, since the base current iB of the first transistor TRI flows to the load 2 via the emitter collector of the third transistor TR3, there is no waste and efficiency is improved.

FIG. 4 is an electrical circuit diagram of another embodiment of the present invention;
Parts corresponding to the illustrated embodiments are given the same reference numerals. In the embodiment of FIG. 3, the first transition, 2. The base current iB of TR1 is determined by the base-emitter voltage VBE of the first transistor TRI and the base-emitter l1flt pressure V'BE of the third transistor TR3.

However, the sub voltage VBE.

Since VBE exhibits diode characteristics, the current cannot be set to an appropriate value. Therefore, in this embodiment, a tap is provided in the coil 6, and the collector of the third transistor TR3 is connected to the coil 6.

In this way, the base current IB can be set to an appropriate value. It becomes like this.

Furthermore, as shown in FIG.

FIG. 6 is an electrical circuit diagram of another embodiment of the present invention, and parts corresponding to each of the embodiments described above are given the same reference numerals. In this embodiment, the base current I of the first transistor TRI
In order to make B a constant current and further improve efficiency, the base of the first transistor TRI and the third transistor TR
A resistor R8 is interposed between the emitters of 3 and 3. As a result, the pace current iB becomes substantially constant over a wide range of voltage changes corresponding to changes in the input voltage E of the first transistor TRI, and the efficiency remains the same.

FIG. 7 is an electrical circuit diagram of another embodiment of the present invention, and parts corresponding to each of the embodiments described above are given the same reference numerals. In this embodiment, at least one and preferably two diodes D2 and D3 are connected in parallel with the resistor R2. In this way, the voltage across the resistor R2 is made constant, and the collector current of the third transistor TR3 is made constant, thereby improving efficiency.

In addition, as shown in FIG. 8, a diode D4 and a resistor (4.4.6, 60 series, A) may be connected in parallel with the resistor R2, and further in parallel with the resistor R2, as shown in FIG. A Zener diode ZD may be connected to the zener diode ZD.

As described above, according to the present invention, since the collector of the third transistor is connected to the tapped coil or between the coil and the load, the collector loss in the first transistor is reduced, and therefore the efficiency is improved. improves.

[Brief explanation of drawings]

Figure 141 is an electrical circuit diagram showing the American technology, Figure 2 is an electrical circuit diagram simply conceived to eliminate the drawbacks of the American technology, and Figure 3 is an electrical circuit diagram of an embodiment of the present invention. 4, 5, 6, 7, 8 and 9 are electrical circuit diagrams showing other embodiments of the present invention, respectively. 1... DC power supply, 2... Load, 3... Smoothing circuit,
4... Control pulse generation circuit, 6... Coil, TRI.
...1st transistor, TR2...%2 transistor, TR3...3rd transistor Agent Patent Attorney Kei Nishi Part 1 Figure 2 Figure 3 JP-A-58-224561 (4)

Claims (1)

[Claims] Between the DC power supply and the load, there is a first
A transistor and a smoothing circuit including a coil are connected in series, and a second transistor that controls the switching operation of the first transistor is controlled by a control pulse generation circuit that generates a control pulse in response to a voltage applied to the load. In a switching type constant voltage circuit designed to
The base of the first transistor is connected to the emitter of the third transistor, the emitter of the third transistor and the emitter of the first transistor are connected via a resistor, and the base of the third transistor is connected via another resistor. connected to the emitter of the first transistor and connected to the second transistor, and the collector of the third transistor;
A switching type constant voltage circuit characterized by being connected between a coil provided with a tap or a coil and a load.