JPS61102168A - Dc/dc converter - Google Patents

Abstract

PURPOSE:To obtain a very small power by a simple transformer construction by connecting an AC converter for converting a relatively low DC current into an AC power in between the secondary windings of a transformer having the primary and secondary windings wound solely. CONSTITUTION:The primary and secondary side windings N1, N2 of a transformer T1 are wound solely. A free-running multivibrator 20 having inverters 21, 22 is connected as an AC converter between the primary windings N1, and a pulse current is supplied from the multivibrator 20 to between the primary windings N1. A rectifier 23 is connected with the secondary side winding N2 of the transformer T1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a DC-DC converter, and more particularly to a DC-DC converter used as a power source for electronic devices that require very small amounts of power.

[Technical background of the invention]

Figures 6 and 7 show a conventional DC-DC converter (D
FIG. 6 shows a self-excited type, and FIG. 7 shows a separately excited type. The self-commutated converter has the collectors of transistors 3 and 4 connected to both ends of the primary winding 2 of the transformer 1, and connects each of the transistors 3 and 4 to its own connection via resistors 5 and 6, respectively. A DC power supply 8 is connected between the middle point 7 of the secondary winding 2 and the emitter of the transistor 4.

Here, when DC power from the DC power supply 8 is supplied to each transistor 3, 4 via the primary winding midpoint 7, the transistors 3, 4 are in a better conduction state.
, 4, and become conductive (ON). Therefore, when the transistor 3 becomes conductive, a pace current flows through the resistor 6 to the transistor 4, and the transistor 4 becomes conductive. In this way, each transistor 3.4 is alternately rendered conductive, thereby causing
- Current flows alternately to both sides of the primary winding 70 with the midpoint of the secondary winding 7 as a border. Then, AC power appears in the secondary winding 9 according to the number of turns of the primary winding 2 of the transformer (7) and the turns ratio of the winding of the secondary winding 9, and this AC power The power is rectified by the rectifier circuit 10 and output as DC power.

On the other hand, in a separately excited converter, a resistor 1). It has a configuration in which a square wave oscillation circuit 13 is connected via 12, and the other parts have the same configuration as the self-excited type. This DC-DC converter is constructed by applying square wave signals whose phases are shifted by half a period from each other from the square wave oscillation circuit 13 to the bases of the transistors 3 and 4, so that the transistors 3 and 4 alternate. becomes conductive. Thus, as in the self-excited type, the midpoint 7 of the primary winding 2
Current flows alternately on both sides of the boundary, AC power appears in the secondary winding 9 according to the winding ratio, and this AC power is rectified and output as DC power.

Therefore, such a DC-DC converter converts a temperature measurement signal obtained from a two-wire instrument with a common source in and an output line, for example, by temperature measurement, into a 4 to 20 mA current signal. It is often used as a DC power source for a temperature measurement detector in a two-wire input/output insulated temperature transmission device that transmits the temperature to another device. In this case, the converter converts the current signal of 4 to 20 mA from the output line to a power consumption that is smaller than the power consumption of the meter itself, for example, 24 mW or less, to the temperature measurement signal generation circuit or amplifier on the temperature measurement detector side. The operation is to supply the Therefore, the converter is required to have low power consumption.

[Problems with background technology]

However, the above converter has the following problems. That is, in the converters shown in FIGS. 6 and 7, transistors 3.4 are connected to both ends of the secondary winding 9 of the transformer 1, respectively, and DC power is supplied through the middle point 7 of the secondary winding. Because of this configuration, it is necessary to use a transformer with a center tap on the negative winding 2 or a transformer with two windings on the secondary winding 2. Therefore, a transformer with a large structure must be used.

In addition, the current from the DC power supply 8 increases when there is no load. Particularly in a self-excited converter, each transistor 3 and 4 are rendered conductive at the same time, albeit for a very short period, and the current consumption during this period increases. Therefore, in order to apply it to a two-wire meter, the current to each transistor 3 and 4 (
dry! However, this reduction in current causes a delay in the timing of conduction of each transistor 3, 4, and there is a limit to how much power can be reduced. The above-mentioned large current consumption also applies to the separately excited type.

However, the con/-? shown in FIGS. 6 and 7? - It is difficult to apply this method to a 2-wire meter, and if used in a 2-wire meter, the output current will deviate significantly from 4 to 20 mA.

[Purpose of the invention]

The present invention has been made based on the above-mentioned circumstances, and its purpose is to provide a DC-DC converter that can use a transformer with a simple configuration and that can be applied to electronic equipment that requires minute power. 9- It is to provide evening.

[Summary of the invention]

The present invention connects an AC conversion circuit composed of, for example, an astable multivibrator between the primary windings of a transformer having a single-wound primary winding and a secondary winding. A direct current system that converts relatively small amount of direct current power into alternating current power and supplies it to the primary winding of a transformer, and rectifies the alternating current power appearing at the secondary winding of this transformer to obtain a direct current output. It is a DC converter t4-.

[Embodiments of the invention]

An embodiment of the DC-DC converter/converter according to the present invention will be described below with reference to FIGS. 1 to 3. 1st
The figure is a circuit configuration diagram of a DC-DC converter according to the present invention. In FIG. 1, 1 is a transformer, and the primary winding N1 and secondary winding N2 of this transformer T1 are each a single winding. An astable multi/4 ibrator 20 having an input/register serving as an AC conversion circuit is connected between the negative and secondary windings N1. The configuration of this astable multi/quad ibrator 20 includes an inverter 21
．． 22 are connected in series, a series circuit of a capacitor C and a resistor R is connected in parallel to the inverter 21, and the connection point between the capacitor C and the resistor R is connected to the input end of the inverter 22. . In addition, each inverter 21
．． 22 uses a C-MOS inverter. And inverter 2.

The connection point 22 is connected to one end of the primary winding N1, and the output end of the inverter 21 is connected to the other end of the primary winding N1. A DC power supply ps is then connected to each inverter 21, 22. On the other hand, a rectifier circuit 23 is connected to the secondary winding N2 of the transformer T.

Next, the operation of the converter configured as described above will be explained. When DC power is supplied to each inverter 21, 22 of the astable multivibrator 20, the astable multivibrator 20 outputs a condenser C and a resistor R.
The pulse signal of the base pulse width is determined by the inverter 2.
They are outputted from the connection point between 1 and 22 and the output end of the inverter 21 with a phase difference of half a period from each other. That is, the operation of this astable multivibrator 20 is explained using a circuit such as that shown in FIG.

That is, the astable multivibrator 20 consists of a series circuit of MO8 type FETs 30 and 31 and an MO8 type FET 32.
, 33 are connected to the DC power supply pslIc, the connection point of MO8 type FETs 32 and 33 is connected to one end of the primary winding [N1, and the M~ type FETs 30 and 31
The connection point is connected to the other end of the primary winding N1. Therefore, to explain the operation, MO8 type FET 30
and 33 are conductive and non-conductive at the same time, Mos type F
ETs 31 and 32 become conductive and non-conductive at the same time.

Is this K? ), FET5o, and ss become conductive, a pulse current t1 flows through the path shown in Fig. 2,
Also FET JJ.

32 becomes conductive, the Jals current 12 flows through a path as shown in FIG. In this way, pulse current 1
). 12 flows through the primary winding N1, an AC voltage transformed according to the turns ratio appears across the secondary winding N2. This AC voltage is rectified by the rectifier circuit 23i and output as DC power.

In this way, in the converter of the present invention, the transformer T
The astable multi/dibrator 20 of the in/guator 21 and 221 is connected between the primary winding N1 of the inverter 21 and the astable multi/dibrator 20, and the /4 pulse current 1).
12 is supplied between the primary winding N1, so the transformer T1
1) It is not necessary to have an intermediate winding on the primary winding, and a transformer with a small number of windings on the secondary side can be used. Furthermore, since an astable multivibrator having a c-v5s in-theta is connected, this converter has low power consumption and operates at about several 100 μW at no load.

This makes the controller of the present invention ideal for two-wire meters. FIG. 3 is a configuration diagram when the converter of the present invention is applied to a two-wire input/output isolated temperature transmission device. The temperature sensing resistor RTD is connected to a circuit 40, and the temperature sensing circuit 40 outputs a temperature measurement signal corresponding to a change in resistance of the temperature sensing resistor RTD. This temperature measurement signal is sent to the operational amplifier 43 via the operational amplifier 41 and the isolation transformer 42 and is amplified, and the collector current of the citransostor Q1 is controlled by this amplified temperature measurement signal. A Zener diode ZD is connected to the emitter of the transistor QI, and the primary winding Nl of the DC-DC converter of the present invention is connected between the Zener diode ZD. In this way, the DC output from the secondary winding N2 side knob of the DC-DC converter is supplied to the Plizzo circuit 40, the oil amplifier 41, and the like. Mari, collector of transistor Q1, emitter,
A resistor Rf1, a load resistor RL, and a DC power supply 44 are connected in series between the resistor Rf1 and the DC power supply 44 via a Zener diode ZD. Therefore, in such a two-wire meter, the current flowing through the load resistor RL becomes a current signal of 4 to 20 mA that changes depending on the temperature measurement signal.

Here, the voltage drop of Zener diode ZD is calculated as DC power supply 4.
4. If the voltage is 6V due to the load resistance Rt, etc., the power consumption of the meter must be 6 (Vl - N4 (mA) (output bias current) = 24mW or less. , a DC-DC converter with low power consumption is required, and the converter of the present invention requires several hundred
It has low power consumption of μW, making it ideal as a DC power supply for two-wire meters.

Furthermore, by employing a converter with low power consumption, the functions of the two-wire meter are not limited by the large power consumption of the converter, and the functions, particularly the circuit configuration, of the two-wire meter are no longer limited.

Note that the present invention is not limited to the above embodiment.

For example, as shown in FIG. 4, each main unit of the astable multivibrator 21-1 to 21-ns.

A plurality of each of 22-1 to 22-n may be connected in parallel. In this way, each inverter 21-1 to 21-n.

By connecting a plurality of transistors 22-1 to 22-1) in parallel, the switching resistance can be reduced, and the output power (pulse signal) provided to the primary winding NllIC of the transformer T1 can be increased.

Furthermore, the circuit configuration shown in FIG. 5 can be used to apply a /gus signal between the transformer and the next winding. That is, NPN transistors QIO and Qll and a PNP transistor Q12 are connected to both ends of the transformer's secondary winding N.
．． A transistor circuit SO whose collectors are commonly connected to QlB.

51 and further connect these transistors Q10 to Q
Resistor RJ with the same resistance value for each pace of 13.

R2, R3, and R4 are connected to supply the transistor circuits 50 and 51 with pulse signals PI and P2 having a phase difference of half a cycle from each other, respectively. With this configuration, the transistor Ql 2 ,
QIJ functions as a discharge transistor, and transistor Q10
．． Qll functions as a suction and a main pulse signal is applied to the transformer's next winding N.

When the transistors QIO to Q13 are used in this way, the switching resistance of the transistors is smaller than that of the C-MOS inverter, so the output power can be increased like the converter shown in FIG. 4.

〔Effect of the invention〕

According to the present invention, an AC conversion circuit for converting relatively small DC power into AC power is connected between the secondary windings of a transformer having a single-wound primary winding and a secondary winding. It is possible to provide a DC-DC converter whose transformer structure can be simplified and which can be applied to electronic devices that require very small amounts of power.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the DC-DC converter according to the present invention, Fig. 2 is an equivalent circuit diagram of the converter shown in Fig. 1, and Fig. 3 is a two-wire type converter shown in Fig. 1. 4 and 5 are block diagrams showing modified examples of the converter of the present invention, and FIGS. 6 and 7 are block diagrams of a conventional DC-DC converter. T1...Transformer, N1...-next winding, N2...
・Secondary winding, PS...DC power supply, 20...Astable multivibrator, 21.22...Inverter, C
... Capacitor, R... Resistor, 23... Rectifier circuit. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 51 Qll Figure 6 Figure 7

Claims (3)

[Claims] (1) A transformer having a single-wound primary winding and a secondary winding, with an output end connected to both ends of the primary winding of this transformer, and a relatively small direct current supplied to the input end. an AC conversion circuit that converts electric power into AC power and applies it to the primary winding of the transformer; and an AC conversion circuit that is connected to both ends of the secondary winding of the transformer and rectifies the AC output appearing between the secondary windings. A direct current characterized by comprising a rectifier circuit.
DC converter. (2) The AC converter circuit is constituted by an astable multivibrator having an inverter as claimed in claim (1).
DC-DC converter described in Section 1. (3) The astable multivibrator is constituted by a plurality of inverters connected in parallel according to claim (2).
DC-DC converter described in Section 1.