JPH0534236Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a surge current absorption circuit for diodes and transistors mainly used in switching regulators.

Generally, when forward current is flowing through a diode, carriers are accumulated on the PN junction surface.
When a reverse voltage is applied, a reverse current flows transiently due to this accumulation effect. This large reverse current,
That is, the surge current causes noise when the diode is used as a rectifying diode in a switching regulator, for example.

Figure 1 shows a circuit diagram of the secondary side of an inverter-type switching regulator with a converter transformer in between.
A series circuit in which a capacitor is connected to both ends of a resistor is connected in parallel with 1 and D2, and this series circuit absorbs surge current to reduce noise generation. The capacitor connected to both ends of the resistor prevents it from burning out if one end of the resistor is grounded during reliability testing or use. However, surge currents occur not only in the rectifier diodes connected to the secondary windings that serve as voltage sources, but also in transistors, and depending on the design specifications of the switching regulator, it may be necessary to A surge current absorption circuit must also be connected to the semiconductor device. Therefore, connecting the same series circuit to each diode or transistor is wasteful from the standpoint of saving circuit elements. The present invention provides a first voltage source whose input end is connected to the output end of the voltage source.
A surge current absorption circuit provided in a semiconductor circuit having a second semiconductor element whose input terminal is connected to the other output terminal of the same voltage source, and whose current output terminals of the respective semiconductor elements are commonly connected. be. This surge current absorption circuit connects the capacitor side end of a first series circuit consisting of a first capacitor and a first resistor to the current input terminal of the first semiconductor element, and connects the capacitor side end to the current input terminal of the second semiconductor element. The capacitor side end of a second series circuit consisting of a second capacitor and a second resistor is connected to the capacitor side, and the resistor side ends of each series circuit are connected in common, and the common connection end of this series circuit and the semiconductor element are connected to each other. A third capacitor is connected between the common connection points of the two.

An embodiment of the present invention will be described below with reference to FIG. 2. Figure 2 shows the converter transformer of an inverter-type switching regulator.
Only the circuit diagram on the next side is shown, where L1 is the secondary winding of the converter transformer that serves as the voltage source, L2 is the chiyoke coil, D3 and D4 are the rectifier diodes, and C1
...C4 is a capacitor, and R1 and R2 are resistors. The anodes of rectifier diodes D3 and D4 whose cathodes are commonly connected are connected to both ends of the secondary winding L1, and the commonly connected cathodes are connected to one end of a chiyoke coil L2. A capacitor C4 is connected between the other end of the choke coil L2 and the intermediate tap of the secondary winding L1, and it is unnecessary to explain that these circuits constitute a rectifying and smoothing circuit of the switching regulator. .

Then, centering on the connection point between resistor R1 and resistor R2, a series circuit of capacitor C1 and resistor R1, a series circuit of capacitor C3 and resistor R2, and a series circuit of capacitor C
2 form one side of a circuit connected in a Y-shape. Capacitor C1 and capacitor C3 are connected to the anodes of rectifier diodes D3 and D4, respectively, and capacitor C2 is connected to rectifier diode D which is commonly connected.
3, connected to the cathode of D4. A first closed circuit is formed between the anode, which is the current input end, and the cathode, which is the output end, of the rectifier diode D3, which is a series circuit in which capacitors C1 and C2 are respectively connected to both ends of the resistor R1. A second closed circuit is formed between the anode and cathode of the resistor R2 by a series circuit having capacitors C3 and C2 connected to both ends of the resistor R2. Furthermore, a capacitor C1, a resistor R1,
A third closed circuit is formed by a series circuit of R2 and capacitor C3.

In the circuit connected in a Y-shape in this way, the first closed circuit and the second closed circuit are each connected to a rectifier diode D3,
It absorbs the surge current of the rectifier diode D4 and forms a surge current absorption circuit for both rectifier diodes. This surge current absorption circuit can save one capacitor compared to the one in Figure 1, but since a third closed circuit is formed, it can also absorb the spike current that occurs in the secondary winding L1. Even when a special circuit is required, there is an advantage that the third closed circuit can be used for the same purpose.

FIG. 3 is a circuit diagram of only the secondary side of a single-stone switching regulator sandwiching a converter transformer, and shows another embodiment of the present invention. The same parts as in FIG. 2 are given the same numbers. Rectifier diode D5 and flywheel diode D6
The cathodes of the two are connected in common, and the anodes of each
It is connected to both ends of the next winding L1. The circuit configuration of the surge current absorption circuit connected in a Y-shape is the same as shown in Figure 2, except that capacitor C1 and capacitor C3 are
are connected to the anodes of rectifier diode D5 and flywheel diode D6, respectively, and capacitor C
2 are connected to a commonly connected cathode. A first closed circuit is formed between the anode and cathode of the rectifier diode D5 by a series circuit in which a capacitor C1 and a capacitor C2 are respectively connected to both ends of a resistor R1, and a resistor R2 is connected between the anode and cathode of the flywheel diode D6. A second closed circuit is formed by a series circuit in which capacitors C2 and C3 are connected to both ends of the secondary winding L, which serves as a voltage source.
A third closed circuit is formed at both ends of 1 in the same manner as in FIG. Such a surge current absorption circuit connected in a Y-shape can absorb the surge current of the rectifier diode D5 and the flywheel diode D6. FIG. 4 is a circuit diagram of a chopper-type switching regulator, and shows yet another embodiment of the present invention, in which the same parts as in FIGS. 2 and 3 are given the same reference numerals. The collector of the control transistor T is connected to a DC source S serving as a voltage source, and its emitter is commonly connected to the cathode of a flywheel diode D6. A capacitor 1C1 of the surge current absorbing circuit connected in a Y-shape is connected to the collector of the control transistor T, a capacitor C3 to the anode of the flywheel diode D6, and a common connection to the capacitor C2. The control transistor T is chopped by the signal applied to the base, and at this time a surge current tries to flow between the collector and emitter, but the capacitor C
1, the surge current is absorbed by the first closed circuit formed by the series circuit of resistor R1 and capacitor C2. The surge current of the flywheel diode D6 is absorbed by the second closed circuit as described above.

Thus, the surge current absorbing circuit of the present invention forms a closed series circuit in which a capacitor is connected to both ends of a resistor between the input terminal and output terminal of two semiconductor elements by Y-shaped circuit connection. Even though the number of capacitors is reduced compared to the conventional method, the surge current of the semiconductor element can be absorbed.

Furthermore, another closed circuit is formed, so for example, if the semiconductor elements are two rectifier diodes of a switching regulator, not only the surge current of the rectifier diodes but also the spike current of the secondary winding of the converter transformer will be generated. can be absorbed.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a switching regulator showing a conventional surge current absorption circuit, and FIG.
3 and 4 are circuit diagrams of a switching regulator showing an embodiment of the surge current absorbing circuit of the present invention. L1... Secondary winding, D1... D5... Rectifier diode, D6... Flywheel diode, C
1...C4...Capacitor, R1, R2...Resistor, L2...Chiyoke coil, T...Control transistor.

Claims (1)

[Scope of utility model registration request] A first semiconductor element having a current input terminal connected to the output terminal of the voltage source, and a second semiconductor element having a current input terminal connected to the other output terminal of the voltage source, and the current output of each semiconductor element In a surge current absorption circuit provided in a semiconductor circuit whose ends are commonly connected, the first
The capacitor side end of a first series circuit consisting of a capacitor and a first resistor is connected to the current input terminal of the first semiconductor element, and the capacitor side of a second series circuit consisting of a second capacitor and a second resistor is connected to the current input terminal of the first semiconductor element. is connected to the current input terminal of the second semiconductor element, the resistor side ends of the respective series circuits are commonly connected, and a second semiconductor element is connected between the common connection point of the series circuit and the common connection point of the semiconductor element. A surge current absorption circuit characterized by connecting a capacitor No. 3.