JP2563385B2 - Switching regulator device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching regulator device for supplying a regulated DC voltage to industrial or consumer equipment.

2. Description of the Related Art Conventionally, this type of switching regulator device has a configuration as shown in FIG. A conventional switching regulator device will be described with reference to FIG. Reference numeral 1 is a DC input power source, and 2 is switching elements 3 and 4 which are turned on / off complementarily by a signal from the control circuit 17.
A switching circuit mainly configured, 9 is a capacitor, 10 is a resistor connected in series to the primary windings 11a and 11b of the transformer 11, and spike voltage generated in the primary windings 11a and 11b is applied to the switching circuit 2. A snubber circuit 11 for preventing application of a voltage, a transformer 11 having primary windings 11a and 11b and a secondary winding, and a pulse voltage applied to the primary winding is 2
It is induced in the next winding and transformed into a predetermined voltage, converted to DC by an output smoothing circuit consisting of diodes 12 and 13, choke transformer 14 and capacitor 15, and supplied to the load from output terminals 16 and 16 '. . The control circuit 17 adjusts by changing the control signal applied to the switching circuit 2 so that the DC voltage at the output terminals 16 and 16 'is constantly constant.

Further, the operation of the snubber circuit composed of the capacitor 9 and the resistor 10 will be described in detail with reference to FIG. FIG. 7A shows a switching voltage waveform A applied to the switching element 3 or 4 of the switching circuit 2. t ₁ ~t ₂ between is between t ₂ ~t ₅ in the period in which one switching element is turned on in a period where one of the switching elements is turned off, t ₃ ~t ₄ during the on other switching elements during _{t 2 ~t 3, t 4 ~t} 5 in the period we are in a period when the switching element is off the counterpart. The spike voltage B shown in the switching voltage waveform A is mainly 1 of the transformer 11.
It is generated by the leakage inductance of the secondary windings 11a and 11b and the energy stored in the leakage inductance of the primary and secondary windings. FIG. 7 (b) shows a current waveform B flowing through the snubber circuit, and it can be seen that when the switching voltage waveform A changes abruptly, a current is passed and power is consumed. By this action, the energy stored in the leakage inductance is consumed in the snubber circuit, so that the spike voltage B is suppressed to a low level. It should be noted that a waveform similar to the voltage waveform of FIG. 7 (a) is generated in the other switching element with a half cycle shift.

FIG. 8 shows another conventional switching regulator device. In FIG. 8, the same parts as those in FIG. 6 are designated by the same reference numerals and the description thereof will be omitted. Reference numerals 7 and 8 are diodes that charge the capacitor 9 with the spike voltage generated in the primary windings 11a and 11b of the transformer 11. 10 is a resistor for discharging the electric charge stored in the capacitor 9.

Further, the operation of the snubber circuit composed of the diodes 7 and 8, the resistor 10 and the capacitor 9 will be described below.
This will be described in detail with reference to the drawings. In Fig. 9 (a), the same parts as those in Fig. 7 are designated by the same reference numerals, and the description thereof will be omitted. FIG. 9A shows the switching element 3 of the switching circuit 2.
Or the switching voltage waveform A'applied to 4 is shown, and B'shows the spike voltage. FIG. 9 (b) shows the waveform C'of the current flowing through the capacitor 9, and it can be seen that the current is selectively passed only to the spike voltage B'and power is consumed. This is because the capacitor 9 is charged by the switching voltage waveform A'through the diodes 7 and 8 while the resistor connected in parallel to the capacitor 9
Since it is discharged by 10, the voltage across the capacitor 9 becomes substantially constant, and the spike voltage B'applied to the switching element 3 or 4 is clamped at a constant value. It should be noted that the clamp voltage can be arbitrarily set to some extent by the capacitance of the capacitor 9 and the resistance value of the resistor 9.

Problems to be Solved by the Invention In such a conventional configuration, in the snubber circuit shown in FIG. 6, power is consumed even when the switching voltage waveform other than the spike voltage changes sharply. When the power consumption of the circuit is increased, a large loss occurs, and the power supply efficiency decreases and the snubber circuit loss increases, which causes the size of components and heat dissipation problem.In addition, the peak current at turn-on of the switching element also occurs. There is a problem that it becomes larger, and the spike voltage cannot be suppressed sufficiently.

Therefore, the snubber circuit shown in FIG. 8 is effective as a means for solving the above problems, but there is a problem that an excessive short-circuit current flows through the switching element at the start of power source startup (when the control circuit is operating). The situation is shown in Figs. 10 and 11.

FIG. 10 (a) shows a capacitor 9 which constitutes a snubber circuit.
Shows the waveform of the voltage V _C across both ends of the switching element 3 (b).
Or the waveform of the current I _D flowing in 4 is shown, and FIG. 11 is an operation explanatory diagram. Since both switching elements 3 and 4 are off before the start of startup, the voltage V _C across capacitor 9 is O _V
Is. When the switching element 4 is turned on at the start of startup, for example, the voltage E is applied to the primary winding 11b of the transformer 11 from the DC input voltage 1, and at the same time, the same voltage E is induced in the primary winding 11a. Therefore, the voltage E is applied to both ends of the capacitor 9 through the diode 7, so that an excessive short circuit current I _C for rapidly charging the capacitor 9 flows through the primary winding 11a. Since the primary windings 11a and 11b are coupled to each other, the same current as the short circuit current I _C flows through the switching element 4. Since the short-circuit current I _C continues to flow until the voltage across the capacitor 9 is charged to the same voltage E as the DC input voltage 1, the short-circuit current I _C flows for a longer time as the capacitor capacity increases. Such an excessive current flowing through the switching element at the time of starting the start breaks the switching element or significantly deteriorates reliability.Therefore, there is a problem that a large capacity switching element capable of withstanding the excessive current is required. .

The present invention solves such a problem. By charging the capacitor with a voltage equal to the voltage E of the DC input power source before starting the start, an excessive charging current flowing in the capacitor at the start of starting is prevented. It is an object of the present invention to eliminate the excessive current flowing in the switching element by eliminating it, improve the reliability of the switching element, and enable the use of a small capacity switching element, thereby constructing an inexpensive switching regulator device.

Means for Solving the Problems In order to solve this problem, the present invention provides first and second switching elements which are connected to one end of a DC input power source and which are turned on and off complementarily by a signal from a control circuit, and at least the above-mentioned switching elements. A transformer having a winding connected in series between the first and second switching elements, a first diode connected to both ends of the DC input power supply, and a switch circuit that turns on or off when the control circuit operates. The other end of the DC input power source is connected to the series circuit and the intermediate tap of the winding, and the series circuit of the second and third diodes is connected to both ends of the winding, and the second and third diodes are connected. A parallel connection circuit of a resistor and a capacitor is connected to the connection point of (1), the connection point of the first diode and the switch circuit.

Operation With this configuration, the voltage across the capacitor can be charged to the same level as the DC input power supply before starting the power supply, and it is possible to prevent excessive charging current to the capacitor at the start of the power supply. Therefore, it becomes possible to eliminate the same current as the excessive charging current of the capacitor transmitted to the switching element through the transformer.

Embodiments Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a circuit configuration diagram of a switching regulator device according to an embodiment of the present invention. In FIG. 1, the same components as those in FIG. 6 are designated by the same reference numerals and detailed description thereof will be omitted. 1
Is a DC input power source, 2 is a switching circuit mainly composed of switching elements 3 and 4, 7 and 8 are diodes, whose cathodes are connected to each other, and whose anode is one end of the primary windings 11a and 11b of the transformer 11. Further, the cathode is connected to the anode of the diode 6 through the parallel circuit of the capacitor 9 and the resistor 10, and the cathode of the diode 6 is connected to the connection point of the primary windings 11a and 11b of the transformer 11 and the DC input power source. Connected to the positive voltage of. 1 of the transformer 11 generated by the on / off operation of the switching circuit 2
The spike voltage generated in the secondary windings 11a and 11b is
The spike voltage is absorbed by charging the capacitor 9 through 7, 8 and 6, and the voltage across the capacitor 9 is kept constant by discharging the charge of the capacitor 9 by the resistor 10, so that the primary winding 11a A snubber circuit for preventing the spike voltage generated in the switches 11b from being applied to the switching circuit 2 is formed. 5 is a switch circuit, one of which is connected to the connection point of the anode of the diode 6 and the capacitor 9 and the resistor 10 and the other of which is connected to the negative voltage of the DC input power source 1
Turns off when 17 starts operating. 12 and 13 are diodes, 14 is a choke transformer, 15 is a capacitor, and 16-16 'are output terminals.

In addition, diodes 7, 8 and 6, capacitor 9, resistor 1
The operation of the snubber circuit composed of 0 and the switch circuit 5 will be described in detail with reference to FIGS. 4 and 5.
4 (a) shows the voltage V _C waveform across the capacitor 9 forming the snubber circuit, FIG. 4 (b) shows the current I _D waveform flowing through the switching element 3 or 4, and FIG. An explanatory view is shown. When the voltage E of the DC input power supply 1 is applied, as shown in FIG. 5, the switch elements 3 and 4 are both turned off, and the positive voltage of the DC input power supply 1, the transformer 11
A current flows to the negative voltage of the DC input power supply 1 through the primary windings 11a and 11b, the diodes 7 and 8, the capacitor 9, and the switch circuit 5 in the ON state, and both ends of the capacitor 9 are the same as the DC input power supply 1. It is charged to the voltage E. Diode 6
Prevents the DC input power supply 1 from being short-circuited by the switch circuit 5. Next, when the control circuit 17 starts the operation and starts the activation, the switch circuit 5 is turned off, and at the same time, the switching elements 3 and 4 are turned on / off. At the start of the startup,
For example, when the switching element 4 is turned on, the voltage E of the DC input power supply 1 is applied to the primary winding 11b of the transformer 11, and at the same time, the same voltage E is induced in the primary winding 11a.
Since the same voltage E as that of the DC input power source 1 has already been stored as the voltage V _C across the capacitor 9, no charging current flows. While the control circuit 17 operates and the switching circuit 2 is on / off, the switch circuit 5 continues to be off,
It does not affect the operation of the snubber circuit, and by selectively consuming power only to the spike voltage generated in the primary windings 11a and 11b of the transformer 11 as in the conventional case, it is efficiently applied to the switching circuit 2. Clamp the spike voltage.

FIG. 2 shows another embodiment of the present invention. In the circuit of this embodiment, snubber circuits are separately connected to the primary windings 11a and 11b of the transformer 11, and the switch circuit 5 and the diode 6 are shared. Further, a configuration in which the snubber circuit and the switch circuit 5 are separately connected to the primary windings 11a and 11b of the transformer 11 is also possible, and the same applies to the case where the transformer 11 has two or more primary windings. It is easy to see that Also, it is easily understood that the same effect can be obtained even if a limiting circuit is provided to limit the current flowing through the switch circuit 5. Further, a capacitor may be connected in parallel with the diode in order to speed up the diode used in the snubber circuit.

FIG. 3 shows a concrete circuit example of the control circuit 17 and the switch circuit 5 used in the embodiment of the present invention. Third
In the figure, the switch circuit 5 includes transistors 20 and 2
1, a resistor 24 and 23, a control circuit 17 is composed of a bias power supply 26, a start-up circuit 25, and a control unit 34. The control unit 34 includes an oscillation circuit 27, a reference voltage 28, an error amplifier 29, and a PWM.
It is composed of a comparator 30, a T flip-flop 31, and OR circuits 32 and 33.

As described above, according to the present invention, the snubber circuit having the diode, the capacitor, and the resistor that efficiently absorbs, consumes, and clamps the spike voltage generated by the leakage inductance of the transformer is the greatest drawback. It is possible to prevent excessive current flowing in the switching circuit at the start of startup with an inexpensive circuit, which may damage the switching element used in the switching circuit,
It is not necessary to use an unnecessarily large-capacity switching element that can withstand an excessive short-circuit current, and reliability is significantly improved.
Moreover, since the snubber circuit can be used, a switching element having a low breakdown voltage can be used, and an efficient switching regulator device with a small snubber loss can be obtained, which is of great industrial value.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a switching regulator device according to an embodiment of the present invention, FIG. 2 is a circuit configuration diagram according to another embodiment of the present invention, and FIG. 3 is a circuit used in the embodiment of the present invention. Specific circuit diagram of block, FIG. 4 is an operation waveform diagram of the present invention, FIG. 5 is an operation explanatory diagram of the present invention, FIG. 6 is a circuit configuration diagram of a conventional switching regulator device, and FIG. 7 is a conventional operation Waveform diagram, FIG. 8 is another conventional circuit configuration diagram, FIG. 9 is another conventional operation waveform diagram, FIG. 10 is a conventional operation waveform diagram, and FIG. 11 is a conventional operation explanatory diagram. 1 ... DC input power supply, 2 ... Switching circuit, 3, 4 ...
… Switching elements, 5 …… Switch circuits, 6,7,8,12,1
3 …… Diode, 9,15 …… Capacitor, 10 …… Resistance, 1
1 …… transformer, 14 …… choke transformer, 16,16 ′ ……
Output terminal, 17 ... Control circuit.

Claims (2)

(57) [Claims] 1. A first and a second switching element which are connected to one end of a DC input power source and which are turned on and off complementarily by a signal of a control circuit, and are connected in series between at least the first and the second switching elements. A series circuit of a transformer having a winding, a first diode connected to both ends of the DC input power supply, and a switch circuit which is turned on or off when the control circuit operates, and the DC input power supply at an intermediate tap of the winding. Connect the other end of the
And a series circuit of a third diode are connected,
A switching regulator device, wherein a parallel connection circuit of a resistor and a capacitor is connected to a connection point of a third diode and a connection point of the first diode and the switch circuit. 2. A second diode, a parallel connection circuit of a first capacitor and a resistor, a parallel connection circuit of a second capacitor and a resistor, and a series connection circuit including a third diode are connected to both ends of the winding. The switching regulator device according to claim 1, wherein the connection point of the parallel connection circuit of the first and second capacitors and the resistor and the connection point of the first diode and the switch circuit are connected. .