JPH01303056A - Dc/dc converter - Google Patents

Abstract

PURPOSE:To prevent the breakdown of parts and the like, by adding a circuit for suppressing a surge voltage generated in a circuit, when the transistor of the circuit is turned OFF. CONSTITUTION:A DC/DC converter is composed of a transformer 10, a transistor(Tr) 20, and a control circuit 30 to supply a load 40 with power. Then, the secondary winding n2 of a saturable magnetic core SR is connected through a resistance R1 and a diode D2 with a tertiary winding N3 provided in said transformer 10 so that a voltage-surge suppressor circuit 50 is added to the converter. Thus, because electric current flows through the secondary winding N2 of the transformer 10 and the primary winding n1 of SR and a voltage generated in the tertiary winding N3 of the transformer 10 is hindered by the diode D2 when the Tr20 is turned OFF, electric current does not flow through the voltage-surge suppressor circuit 50. Then, because electric current If flows through the secondary winding n2 of SR by the voltage generated in the tertiary winding N3 of the transformer 10 and the SR is saturated and the Tr20 is turned OFF in the state when the Tr20 is switched from OFF to ON, no surge voltage is not generated in the converter.

Description

[Detailed Description of the Invention] [Summary] Regarding the DC/DC converter used in communication devices, etc., the DC/DC converter is equipped with a circuit that suppresses the surge voltage generated when the transistor (hereinafter referred to as Tr) in the above circuit is turned off. C/
In order to provide a DC converter, one end of the primary winding N1 and the other end of the primary winding are connected to a DC power source through a switch means, and the voltage of the primary S cotton is transformed to 2 A lance that outputs to the next winding N2, a switch means that is inserted between one end of the primary winding of the transformer and the DC power supply and performs on/off operation according to a control signal, and one end of the secondary winding of the transformer. A saturable magnetic core (hereinafter referred to as SR) connected to St? A DC smoothing means connected to the other end rectifies and smoothes the human input signal, and a voltage state of a load connected to the DC smoothing means and the other end of the secondary winding of the transformer is used to control the switching means at a predetermined level. B
In a DC/DC converter having a control means for outputting a control signal for on/off control during i'1, a tertiary winding N added to the transformer and a secondary winding n2 added to the SR. one end of which is connected, the tertiary winding N, and the secondary winding n
A surge voltage suppression circuit formed by connecting a diode 1"D2 and a resistor R having a predetermined resistance value in series is added between the other ends of the surge voltage suppressing circuit.

[Industrial application field]

TECHNICAL FIELD The present invention relates to an improvement of a DC/DC conharc used in a JM communication device or the like.

At this time, there is a demand for a DC/DC converter that is equipped with a circuit that suppresses the surge voltage that occurs when the Tr in the circuit 2 is turned off.

[Conventional technology]

FIG. 4 is a circuit diagram of a conventional DC/DC converter.

In Fig. 4, if the voltage across the load 4 is Eo, then
The voltage at the midpoint f of the resistor connected in parallel to load 4 is Eo/2
becomes. This voltage is applied to a known operational amplifier (
(Hereinafter referred to as operational amplifier) Add it to one side of 3-2. In this case, to the other human power, add base r1 (voltage Vrc!f) set to 172, which is the voltage value you want to output to 1"l load,
Find the voltage difference between EO/2 and the reference voltage 'Jref.

This is a voltage/frequency conversion circuit (hereinafter referred to as V/[) 3
-1 and outputs a pulse (pulse width is constant) with a frequency corresponding to the difference in voltage. Tr this output
2, the switching period of 'Pr 2 is changed and the load voltage is controlled to be constant.

Now, when Tr 2 is on, the primary winding N of transformer 1
Current flows through transformer 1, but since the secondary winding N2 of transformer 1 is in the opposite direction to the primary winding, it is blocked by diode In, and no current flows through the secondary winding. .

Next, when Tr2 is off, the energy stored in the secondary winding when Tr2 is on is released, and a current flows in the forward direction of the secondary winding C1 diode D1.

Next, when Tr 2 is turned on, the current flowing through diode D+ does not instantaneously become 0, but due to the accumulated charge in D, a current Is flows in the opposite direction in a pulsed manner as shown by the dotted line in Figure 4. . At this time, inductance Ls due to wiring in the circuit, etc.
(not shown) both of the diode F' DI ◇:;
Excessive →noge voltage is generated. This surge voltage causes destruction of the diode D1 or generation of large noise at the output terminal.

As a method of suppressing the generation of this 1-nerge voltage, an SR shown in Fig. 4 is inserted in series with the diode 1]1 to block the reverse current Is that is the cause of the 1-nerge voltage. ing. That is, the high inductance of SR blocks the reverse current Is.

In this way, the surge voltage generated across the diode when the Tr is turned on is prevented.

[Problem to be solved by the invention]

However, in the circuit described above,
Due to the inductance, the forward current flowing when the Tr is turned off is also blocked, and both of the SR ◇:! 1 voltage increases, and the voltage generated in the secondary winding N2 of the transformer also increases. Therefore, the voltage generated in the primary winding N1, which is determined by the turn ratio of the tramp, also increases, causing the problem that an excessive surge voltage is applied to Tr2, resulting in destruction of Tr2.

Therefore, an object of the present invention is to provide a D
The purpose is to clean the C/DC converter.

[Means to solve the problem]

The second problem can be solved by the circuit configuration shown in FIG.

That is, in FIG. 1, one end of the primary winding 11+ and the other end of the primary winding θ:! through the switch means 200. ; is connected to the DC power supply, transforms the voltage of the primary winding, and connects the secondary 8 wire N2
1-lance 100 that outputs to
A saturable magnetic core Sit is connected to one end of the next winding and prevents the generation of leege voltage, and a saturable magnetic core Sit is connected to the other end of the saturable magnetic core,
A DC smoothing means 600 rectifies and smoothes an input signal, and a switching means is controlled to be turned on and off for a predetermined time depending on the voltage state of a load connected to the DC smoothing means and the other end of the secondary S line of the transformer. In the DC/DC converter circuit 500, a tertiary winding N, which is added to the transformer, and one end of the secondary winding n2, which is added to the saturable magnetic core, are connected to the transformer. connected, tertiary winding N3
This surge voltage suppression circuit is formed by connecting in series a diode "D2" and a resistor R1 having a predetermined resistance value between the other end of the secondary winding r12 and the other end of the secondary winding r12.

[For production]

In FIG. 1, when the switch means 200 is switched from OFF to ON, a voltage generated in the tertiary winding NJ of the transformer 100 causes a current to flow through the diode D2 and the resistor R1 to the secondary winding n2 of the saturable magnetic core SR. As a result, the saturable magnetic core SR becomes saturated.

As a result, the switch means 200 is turned off when the saturable magnetic core SR is in a saturated state, i.e., in a low inductance state, so that no excessive voltage is generated in the primary winding N1 of the transformer ]00.

〔Example〕

The second figure is a circuit diagram of a DC/DC converter to which a surge voltage suppression circuit is added according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating the operation of the embodiment.

The same reference numerals indicate the same objects throughout the figures.

In Fig. 2, the tertiary winding N installed in the transformer 10
J is resistor R1 and die; t-FD2 is 1ffi
II (connected to secondary winding n2).

When Tr20 is off, current flows through the secondary 8 wire N2 of the transformer 10 and the primary winding nl of the SR. Also, the voltage generated in the tertiary winding N3 of the transformer 10 is connected to the diode l.
'12, the surge voltage suppression circuit 5
No current flows at 0.

Next, when Tr20 switches from off to on,
As shown in FIG. 3, due to the voltage generated in the tertiary winding N3 of the transformer 10, a current I flows through the resistor R1 and the diode 1-"D2 to the secondary S line n2 of the Sll. At this time, SR is The current ■r brings it into a saturated state.

As a result, St? Since the Tr 20 is turned off when the inductance is saturated (that is, the inductance value is low), it is possible to prevent the generation of a sudden voltage.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to suppress the surge voltage that occurs when the transistor is turned off, and it is possible to eliminate the damage to parts due to the generation of the surge voltage or the influence on the fl and load due to output noise.

[Brief explanation of the drawing]

Fig. 1 shows the principle of the present invention, Fig. 2 is a circuit diagram of a DC/DC converter added with a surge voltage suppression circuit according to an embodiment of the present invention, and Fig. 3 is a diagram explaining the operation of the embodiment. FIG. 4 is a circuit diagram of a conventional DC/DC converter. In the figure, 100 is a transformer, 200 is a switch means, 300 is a control means, 500 is a nudge voltage suppression circuit, and 600 is a DC smoothing means.

Claims (1)

[Claims] One end of the primary winding (N_1) and the switch means (200
), the other end of the primary winding is connected to a DC power supply, and the
A transformer (100) transforms the voltage of the secondary winding and outputs it to the secondary winding (N_2), and is inserted between one end of the primary winding of the transformer and the DC power supply, and is turned on/off by a control signal. a saturable magnetic core (SR) connected to one end of the secondary winding of the transformer to prevent the generation of surge voltage; a switch means (200) connected to the other end of the saturable magnetic core;
DC smoothing means (600
), and control means (300) for outputting a control signal for controlling on/off of the switching means for a predetermined time depending on the voltage state of the load connected to the DC smoothing means and the other end of the secondary winding of the transformer. In the DC/DC converter, one end of a tertiary winding (N_3) added to the transformer and a secondary winding (n_2) added to the saturable magnetic core are connected, and the tertiary winding A surge voltage suppression circuit (500) formed by connecting a diode (D_2) and a resistor (R_1) having a predetermined resistance value in series between the other end of the secondary winding (N_3) and the secondary winding (n_2). D characterized by adding
C/DC converter.