JPH0245435B2 - 2SEKISHIKIFUOWAADOGATASUITSUCHINGUREGYUREETA - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a two-stone forward switching regulator, and more specifically, a two-stone forward switching regulator that balances heat loss due to variations in the characteristics of its switching elements. This relates to a type switching regulator.

Conventional technology and its problems Switching regulators include types suitable for small size and small capacity, such as ringing chain type and series type, and types suitable for large and large capacity, such as push-pull type, half bridge type, and full bridge type. There are some suitable formats, but in recent years small and
The single-stone forward type, which is suitable for large capacity, is becoming mainstream. However, the output capacity of this single-stone forward type is limited to a few hundred W, and for those with an output capacity higher than that, a full bridge type or a two-stone forward type is used. Among these, the two-stone forward type has two switching elements. They tend to be used frequently because they can achieve an output capacity of several kilowatts.

The operation of this two-stone forward type switching regulator will now be explained with reference to FIG. In Fig. 4, the DC voltage applied between the input terminals 1 and 1' is applied to the transformer 6 when the first and second switching elements 2 and 3, which are turned on and off in the same phase, are turned on.
The voltage applied to the primary winding 6-1 and induced in the secondary winding 6-2 according to the turns ratio is rectified by the diode 7, smoothed by the reactor 9 and the capacitor 10, and then sent to the output terminal 11. , 11'. Furthermore, when the first and second switching elements 2 and 3 are off, the energy stored in the reactor 9 is supplied to the load via the diode 8, and the excitation energy of the primary winding of the transformer is transferred to the first and second switching elements. It is fed back to the input side via diodes 4 and 5.

The above-mentioned two-stone forward type switching regulator includes first and second switching elements 2,
A control signal is given so that the second switching element 3 turns on and off in the same phase, but due to variations in the characteristics of the elements, they do not turn on and off at exactly the same time. For example, if the second switching element 3 turns off earlier, the second As shown in Fig. 5, the voltage applied when the second switching element 3 is turned off increases, and the heat loss during turn-on and turn-off of the second switching element 3 becomes larger than the heat loss of the first switching element 2, causing the temperature to decrease. There were cases where the lift became unbalanced and even led to destruction. Therefore, the characteristics of the switching elements must be selected, which has the disadvantage of increasing the number of steps.

Purpose of the Invention The present invention solves the above-mentioned drawbacks, and by balancing the voltage applied when the switching element is turned off, it balances the heat loss of the switching element, reduces the number of man-hours for selecting characteristics, and achieves stable operation. The purpose is to provide a small-sized, large-capacity switching regulator.

Structure of the Invention The two-stone forward type switching regulator of the present invention has a first switching element and a first diode connected in series between input terminals, and a second switching element and a first diode connected in series between the input terminals.
The switching element and the second diode are connected in series, one end of the primary winding of the transformer is connected to the connection point between the first switching element and the first diode, and the second switching element and the second diode are connected in series. The other end of the primary winding of the transformer is connected to the connection point with the diode, and the primary winding of the transformer is further provided with a center tap, and two capacitors are connected in series between the input terminals. A resistor is connected between the tap and the connection point of the two capacitors.

Examples The following examples will be explained below. FIG. 1 is a circuit diagram of a two-stone forward switching regulator of the present invention, in which parts having the same functions as in FIG. 4 are designated by the same reference numerals. The two capacitors connected in series between the input terminals according to the present invention are 12 and 13.
A resistor 14 is connected between the connection point and a center tap provided on the primary winding 6-1 of the transformer 6. Therefore, the primary winding 6 of the transformer 6
The center tap of -1 is clamped to a potential of 1/2 of the DC voltage applied between input terminals 1 and 1'.
Even if there are variations in characteristics such as turn-off time between the first and second switching elements 2 and 3, as shown in FIG.
It is possible to balance the voltages applied when 3 is off, and the heat loss can also be balanced.

Note that in the above embodiment, the capacitors 12 and 13
The purpose of this is to prevent the voltage applied during off-state from being unbalanced due to variations in the characteristics of the first and second switching elements 2 and 3, and a large capacity device such as that used in a half-bridge type is not necessary. The output capacity is about 1KW and the capacitor is 1.
2 and 13 may be on the order of tens of thousands _{of PF} , and the resistor 14 may also be on the order of several tens of ohms.

FIG. 3 shows another embodiment of the present invention, in which input terminals 1,
During 1', the AC voltage is rectified into DC by the rectifier 15,
A DC voltage obtained by smoothing with a smoothing capacitor 16 is applied.

Effects of the Invention As detailed in the embodiments, the two-stone forward switching regulator of the present invention has a center tap provided in the primary winding of the transformer, and two capacitors connected in series between the input terminals. By connecting a resistor between the center tap and the connection point of the two capacitors, it is possible to balance the voltage applied when the first and second switching elements are turned off and the heat loss. This reduces the number of man-hours required to select switching elements, and can greatly contribute to the miniaturization and increase in capacity of switching regulators.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a two-stone forward switching regulator of the present invention, FIG. 2 is an operating waveform diagram of the first and second switching elements of the present invention, and FIG. 3 is a diagram of another switching device of the present invention. FIG. 4 is a circuit diagram of a conventional two-stone forward type switching regulator, and FIG. 5 is a diagram of operating waveforms of the first and second switching elements in the prior art. 1, 1'...Input terminal, 2...First switching element, 3...Second switching element, 4...
...first diode, 5...second diode,
6...Transformer, 12,13...Capacitor, 1
4...Resistance.

Claims (1)

[Claims] 1 A first switching element and a first diode are connected in series between the input terminals, a second switching element and a second diode are connected in series, and the first switching element and the first diode are connected in series. A two-stone forward type in which one end of the primary winding of the transformer is connected to the connection point, and the other end of the primary winding of the transformer is connected to the connection point of the second switching element and the second diode. In the switching regulator, a center tap is provided on the primary winding of the transformer, and two taps are provided between the input terminals.
A two-stone forward type switching regulator, characterized in that two capacitors are connected in series, and a resistor is connected between the center tap and the connection point of the two capacitors.