JPH0239187B2 - DCCDCKONBAATA - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a DC-DC converter that cuts and cuts DC input from an input power source using a semiconductor switch element, converts it into DC via a transformer, and outputs the converted DC.

Conventionally, the DC-DC converter is shown in the figure.
A DC-DC converter that does not use a transformer T ₂ ' is known. In this DC-DC converter, a DC input power source E and a transformer T ₁ '' are connected, and the primary winding N ₁ of the transformer T ₁ '' is connected in series with the Darlington connection circuit of the switch transistors TR and TR ₁ . The transistor is supplied with power from the DC input power supply E and is controlled by the control circuit CON.
A DC output whose power is controlled is obtained by turning on and off the predetermined frequencies of TR and TR ₁ . The DC power supply DC1 is
Power is controlled from the secondary winding N ₂ of the transformer T ₁ ″ and the secondary winding N ₂ of the transformer T ₁ ″ to the DC power supply DC1, and a DC voltage is output from the DC power supply DC.

The output voltage control of DC power supply DC1 is
The output voltage of is the sense input to the control circuit CON,
This is performed by controlling the primary side of the transformer T ₁ ″. Through this control, the output of the DC power supply DC1 can be stabilized without having an output stabilizing circuit and with only a smoothing circuit.

However, in this DC-DC converter, when transistors TR ₁ and TR are turned on and the voltage between the collector and emitter of transistor TR is saturated, the saturation voltage becomes high.As a result, the loss of transistor TR increases and the efficiency of the converter decreases. The disadvantage is that it decreases. Therefore, by providing a tap on the primary winding N1 of the transformer _{T1 '} ' and connecting the collector of the transistor _TR1 to this tap, the saturation voltage between the emitter and collector of the transistor TR can be lowered, and the loss of the transistor can be reduced.

However, if you do this, the above transformer
The position of the tap provided on the primary winding _N1 of _T1 '' needs to be selected at an optimal value to lower the saturation voltage between the emitter and collector of the transistor TR, but as the operating frequency of the converter increases, As the induced voltage increases, it becomes difficult to find the position of the tap to obtain the optimum value.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above drawbacks and provide a DC-DC converter that has high efficiency even at high operating frequencies.

The figure shows an embodiment of the invention.

In this embodiment, a transformer T ₂ ′ is connected to the primary winding N ₁ of the transformer T ₁ ″ in the above DC-DC converter, and the saturation voltage between the emitter and collector of the transistor TR is selected to be a low desired optimum value. It is.

Details of this example are shown below.

A DC input power supply E and a transformer T ₁ ″ are connected, and the primary winding N ₁ of the transformer T ₁ ″ is connected in series with the switching transistor TR, while the collector of the transistor TR and the primary winding of the transformer T ₁ ″ are connected in series. Connect the transformer T ₂ ' between the tap ends coming out from N ₁ .

Also, take out the tap from the winding of transformer T ₂ ′,
Connect the collector of the Darlington connected transistor TR ₁ to this tap. Power is supplied from the DC power supply E, and the control circuit CON controls the _power from the secondary winding _N2 of the transformer _T1 to the DC power supply _DC1 by turning on and off the transistors TR and _TR1 at a predetermined frequency. A desired DC voltage is output from. A DC power source DC ₁ that obtains a DC output is powered from the secondary winding N ₂ of the transformer T ₁ ″.

Output control of the DC power supply DC ₁ is performed by using the output voltage of the DC power supply DC ₁ as a sense input to the control circuit CON, and controlling the transistor TR with the control circuit CON.

In this embodiment, transistors TR,
The switch is operated by connecting the two _TR1s in Darlington, but by using the tap of the transformer _T2 ', the collector voltage when the transistor is on is
The saturation voltage between the emitters can be lowered, and highly efficient switch operation with extremely low loss is possible.

As described above, according to the present invention, in a DC-DC converter in which a second transistor is Darlington-connected to a first transistor in series with the transformer primary winding, the transformer primary winding and the collector of the first transistor are connected to each other. Since the second transformer is inserted between the connection point and the tap of the primary winding of the transformer and the collector of the second transistor, the switching effect of the transistor is high even at high operating frequencies, resulting in high efficiency.

In the above embodiment, a single-stone type converter has been described, but a half-bridge type converter and a push-pull type converter can be similarly implemented.

[Brief explanation of drawings]

The figure is a circuit diagram showing an embodiment of the present invention. T ₁ ″, T ₂ ′...Transistor, TR, TR ₁ ...Transistor.

Claims (1)

[Claims] 1 A first transformer whose primary winding is connected to a DC input power source, a first transistor connected in series between the primary winding of this transformer and the DC input power source, and a Darlington connection with this first transistor. a transistor circuit consisting of a second transistor turned on and off at a predetermined frequency; a DC power source that is supplied with power from the secondary winding of the first transformer and outputs a DC voltage; and an output of this DC power source. and a control circuit that controls the output voltage of the DC power supply by receiving a voltage as a sense input and controlling the transistor circuit.
In the DC-DC converter, a second transistor is inserted between a connection point between the primary winding of the first transformer and the collector of the first transistor, and a tap of the primary winding and the collector of the second transistor. A DC-DC converter equipped with two transformers.