JP3396994B2 - Multi-output DC-DC converter - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a power supply device for an electric vehicle or the like and has a multi-output DC-unit having a plurality of DC output sections.
It relates to a DC converter.

[0002]

2. Description of the Related Art As a multi-output DC-DC converter, a plurality of secondary windings are provided on the secondary side of a transformer in which a switching element is connected to the primary side, and the secondary windings are respectively provided.
Converters that connect a rectifying and smoothing circuit to obtain DC outputs of a plurality of systems are used as various DC power supply devices.

Since the output voltage of this type of DC-DC converter may increase significantly when there is no load, when a semiconductor circuit for controlling a motor or the like is connected to the output side,
In order to prevent the destruction of the semiconductor element, it is necessary to control the output voltage to be a constant voltage.

Therefore, conventionally, in a DC-DC converter, a dummy resistor is connected to the secondary side of the transformer to branch the load current, and a switching element is connected in series with the dummy resistor and the load current is detected. When the load is in a no-load state, a voltage detection circuit that turns on the switching element and sends a current to the dummy resistor when the load goes into a no-load state to suppress the output voltage rise is stabilized. A digitizing circuit is proposed by Japanese Patent Laid-Open No. 6-311748.

[0005]

However, the multi-output DC-
When the voltage stabilizing circuit having the above-mentioned configuration is adopted in the DC converter, it is necessary to connect the voltage stabilizing circuit to all of the plurality of output circuits provided on the secondary side of the transformer. However, there is a problem in that the manufacturing cost increases as the manufacturing cost increases.

The present invention has been made in view of the above points, and it is not necessary to connect the voltage stabilizing circuit to all of the plurality of output circuits connected to the secondary side of the transformer, and a simple circuit configuration is adopted. An object of the present invention is to provide a multi-output DC-DC converter capable of stabilizing the voltage of all of a plurality of output circuits.

[0007]

In order to achieve the above object, a multi-output DC-DC converter of the present invention includes a transformer having a primary winding and a plurality of secondary windings, and a primary winding of the transformer. A switch circuit connected to the transformer and a plurality of rectifier circuits connected to each of the secondary windings of the transformer, one secondary winding of the plurality of secondary windings being used for output detection, The detection resistance circuit for voltage detection is connected to the output side of the rectifier circuit connected to the detection secondary winding, and the switching operation of the switch circuit is controlled so that the voltage of the detection resistance circuit becomes a constant value. in multi-output DC-DC converter control circuit is connected to the switch circuit, con
Inverters are installed on the output side of multiple rectifier circuits for burner output.
The device's multi-phase gate drive circuit is connected as a load device.
Of the switching element provided in the gate drive circuit
Switching stop signal output when switching stops
Is used as a load current reduction signal to
Based on the load current reduction signal output when reducing the current
Switch to increase the resistance value of the detection resistance circuit.
An anti-switching means is provided .

[0008]

A plurality of resistors may be connected to the detection resistance circuit, and a transistor may be connected as the resistance switching means to the detection resistance circuit so that the connection of the resistors is switched by the transistor.

[0010]

[Operation and effect] In the multi-output DC-DC converter configured as described above, at the time of its operation, the detection resistance circuit connected to the output side of the rectification circuit for output detection produces a voltage equivalent to the load voltage of the converter. It detects and sends the voltage signal to the control circuit of the switch circuit. Since the control circuit controls the switching operation of the switch circuit so that the voltage of the detection resistance circuit becomes a constant value, the output side voltage of the rectification circuit connected to the plurality of secondary windings for converter output, that is, The voltages of the plurality of load devices are controlled to be constant voltages.

Therefore, it is not necessary to connect a voltage stabilizing circuit to a plurality of output circuits connected to the secondary side of the transformer, and it is possible to stabilize the voltage of all the plurality of output circuits with a simple circuit configuration. You can

Further, since the resistance switching means switches so as to increase the resistance value of the detection resistance circuit based on the load current reduction signal output when the load current of the load device is reduced, the load current is reduced from the load device. When a signal is output, the resistance value of the detection resistance circuit increases, which increases the feedback gain of the control circuit that controls the switch circuit. Therefore, the output voltage of the converter is suppressed when the load current is reduced, and overvoltage that tends to occur at that time is prevented,
It is possible to prevent the circuit breakdown of the load device due to overvoltage.

[0013]

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

FIG. 1 is a block diagram of a multi-output DC-DC converter that supplies DC power to an inverter device 15 that drives and controls an AC servomotor 20. Reference numeral 1 is a transformer for a DC-DC converter, 2 is a primary winding of the transformer 1, and 3, 4, 5 and 6 are secondary windings of the transformer 1. The secondary windings 3, 4, 5 are for output of the converter, and the secondary winding 6 is used for output detection.

A switch circuit 7 is connected to one end of the primary winding 2 of the transformer 1, and a control circuit 8 for controlling the switching is connected to the switch circuit 7. The control circuit 8
Output a pulse signal with a controlled duty ratio to the base of the switching element built in the switch circuit 7,
Control is performed so that a predetermined output voltage is obtained from each output circuit.

A DC power supply B such as a battery is connected to the input side of the DC-DC converter, that is, between one end of the primary winding 2 of the transformer 1 and the switch circuit 7, and a smoothing capacitor C1 is connected in parallel with it. .

Each secondary winding 3, 4, 5, 6 of the transformer 1 has a rectifying circuit 9 composed of a diode and a smoothing circuit,
10, 11, 12 are connected. The rectifier circuit 12 is used for output detection, and the other three rectifier circuits 9, 10, 11 are used.
Supplies DC power to the inverter device 15 connected to its output side.

For the inverter device 15, for example, a three-phase voltage type PWM inverter is used, and a three-phase AC servomotor 20 is connected to the output side thereof. 16, 17, 18
Is a gate drive circuit for driving the switching elements 21, 22, and 23 provided in the inverter device 15. The switching elements 21, 22, and 23 are IGBTs and MOs, respectively.
It consists of voltage drive type semiconductor switch element such as SFET,
Diodes 24, 25, 26 are connected in parallel to the switching elements 21, 22, 23, respectively.

Further, 19 is a gate control circuit of the inverter device 15, which outputs a pulse signal having a controlled pulse width to the gate drive circuits 16, 17 and 18 of each phase in the inverter device 15 at a predetermined cycle. To do. Further, the gate control circuit 19 sends a signal for switching the resistance value of the voltage detection resistance circuit described later to the transistor T of the resistance switching circuit 14 during the switching stop control of the inverter device 15.
output to r.

At the output side of the rectifier circuit 12 of the secondary winding 6 for output detection, a voltage detection resistance circuit 13 and a resistance switching circuit 1 are provided.
4 is connected. The resistance value of the detection resistance circuit 13 is set to be the same as the load resistance at the time of switching the gate drive circuits 16, 17, and 18 of the inverter device 15.

That is, the load in the gate drive circuits 16, 17 and 18 is a loss caused by charging / discharging the gates of the voltage drive type semiconductor switching elements 21, 22 and 23 and other circuits, and rectification for output detection. By setting the resistance value of the detection resistance circuit 13 connected to the output side of the circuit 12 to the same value as this resistance value, the same state as the load of each phase (gate drive circuits 16, 17, 18) is created. The control circuit 8 is controlled according to the output voltage.

The resistance circuit 13 for detection is constructed by connecting the resistance R1 connected in series to the output side of the rectifier circuit 12 and the resistance R2 and the resistance R3 connected in series, and the resistance switching circuit 14 is connected in series. Connected resistor R4 and transistor Tr
Is connected in parallel with the resistor R3. And
The detection resistance circuit 13 is connected so as to send a voltage signal to the control circuit 8 from the connection point of the resistors R2 and R3.

A signal corresponding to the switching state including a switching stop signal is applied to the base of the transistor Tr of the resistance switching circuit 14 from the gate control circuit 19 of the inverter device 15, and the gate drive circuits 16 to 18 switch the switching element 21. , 22 and 23 are charged and discharged, the transistor Tr maintains the ON state, and the gate control circuit 19
When the switching stop signal is output from the transistor Tr, the transistor Tr is turned off.

In the circuits 13 and 14 having the above structure, when the transistor Tr is turned on by the signal sent from the gate control circuit 19 of the inverter device 15 (the gate drive circuits 16 to 18 charge the switching elements 21, 22 and 23). During discharging), the output voltage generated in the detection resistance circuit 13 is divided by the parallel combined resistance of the resistors R3 and R4, and the voltage signal is sent to the control circuit 8. On the other hand, when the transistor Tr is off (gate drive circuit 16-
When the charging / discharging of the gates of the switching elements 21, 22, and 23 is stopped by 18), the output voltage generated in the detection resistance circuit 13 is divided by the resistances R2 and R3, and the voltage signal is divided by the control circuit 8. Send to.

The control circuit 8 of the DC-DC converter receives the voltage signal from the detection resistance circuit 13 as a control signal and controls the switch circuit 7 so that the output voltage of the rectifier circuit 12 becomes a constant value. .

Next, the operation of the multi-output DC-DC converter having the above configuration will be described.

The DC-DC converter supplies the DC power supplied from the DC power supply B on the primary side of the transformer 1.
The switch circuit 7 switches at a cycle controlled by the control circuit 8 to generate AC power in the secondary windings 3 to 6 of the transformer 1. The AC power generated in the secondary windings 3 to 6 is converted into DC by the rectifier circuits 9 to 12 connected thereto, and the three-phase DC power output from the rectifier circuits 9 to 11 is converted into the inverter. Sent to the device 15.

In the gate drive circuits 16 to 18 of each phase of the inverter device 15, the gate control circuits 19 cause the gate drive circuits 16 to 18 to operate by the operation of the gate control circuit 19.
The switching operation is performed in the time width controlled by 9, and the AC power having the controlled pulse width is supplied to the AC servomotor 20 to drive the motor 20.

Each gate drive circuit 1 of the inverter device 15
In the normal state where 6 to 18 perform the switching operation,
Since the switching stop signal is not output from the gate control circuit 19, the transistor Tr of the resistance switching circuit 14 maintains the ON state, and the load of each phase of the DC-DC converter (gates of the switching elements of the gate drive circuits 16 to 18). The charge / discharge loss load) is a relatively large value. The output characteristic of the converter at this time is as shown by the output characteristic curve A in FIG. 2, and the DC-DC converter operates near the operating point C.

In such an operating state, the control circuit 8 inputs a voltage signal from the detection resistance circuit 13 and, according to the voltage, the base of the switching element in the switch circuit 7,
A pulse signal with a controlled duty ratio is output, and control is performed so that a predetermined output voltage is obtained from the output circuit of the converter. At this time, the transistor T of the resistance switching circuit 14
Since r is in the ON state, the voltage signal divided by the resistance R2 and the parallel combined resistance of the resistances R3 and R4 is sent from the detection resistance circuit 13 to the control circuit 8.

That is, during the normal switching operation of the inverter device 15, the feedback gain of the feedback control performed by the control circuit 8 is (R3 // R4) / {R
2+ (R3 // R4)}.

On the other hand, when the protection circuit of the inverter device 15 operates and the switching stop signal is output from the gate control circuit 19 and the switching operation of the gate drive circuits 16 to 18 is stopped, the switching stop signal is the resistance switching circuit. 14 is applied to the base of the transistor Tr to turn off the transistor Tr. Therefore, the detection resistance circuit 13 sends to the control circuit 8 a voltage signal divided by the resistances R2 and R3.

That is, when the switching of the inverter device 15 is stopped, the feedback gain of the feedback control performed by the control circuit 8 is R3 / (R2 + R3), which is larger than that during the switching operation.

As described above, when the switching of the inverter device 15 is stopped, the feedback gain of the control circuit 8 becomes larger than that during the switching operation, so the control circuit 8 controls so as to suppress the output of the converter.

Therefore, the output characteristic of the converter when the transistor Tr of the resistance switching circuit 14 is off is shown in FIG.
The output characteristic curve B is lower than that of the characteristic curve A, and as the switching of the inverter device 15 is stopped, the resistance loss of the switching element of the switching circuit, that is, the load is small, and the output current is reduced. , The converter operates near the operating point D. For this reason,
As shown in FIG. 2, even when the switching of the inverter device is stopped, the output voltage of the converter does not become an overvoltage and can be maintained near the rated voltage.

FIG. 3 shows another embodiment of the resistance switching circuit connected to the detection resistance circuit 13. The resistance switching circuit 24 is composed of a resistor 5 and a transistor Tr connected in series, and is connected in parallel to both ends of the resistor 2 and the resistor 3 or the resistor 1 of the detection resistor circuit 13. The base of the transistor Tr is connected to the gate control circuit 19 as described above.

In the resistance switching circuit 24 having such a configuration,
When the transistor Tr is on, the load on the secondary phase used for detecting the output voltage is the combined resistance of the resistors R1 and 5.

On the other hand, when the transistor Tr is off, the load of the secondary phase used for detecting the output voltage is the resistor R1. Here, the resistor R1 is applied to the load of the gate drive circuits 16 to 18 when the inverter device is stopped, and the resistor R1
By setting the combined resistance of the resistor R5 and the resistor R5 as the load of the gate drive circuit during switching of the inverter device, the transformer characteristic curve shown in FIG. 2 is obtained. Therefore, as in the above embodiment, the output voltage of the converter does not become an overvoltage and can be maintained near the rated voltage even when the switching of the inverter device is stopped.

Further, FIG. 4 shows another embodiment of the resistance switching circuit connected to the detection resistance circuit 13. The resistance switching circuit 34 is configured by connecting a capacitor C2 between the resistance R4 and the resistance R2 of the resistance switching circuit 14 in the embodiment of FIG.

As described above, by connecting the capacitor C2 to the resistance switching circuit 34, when the gate control circuit 19 of the inverter device 15 changes from the switching stop signal to the switching operation signal and the transistor Tr is turned on,
The voltage signal sent from the detection resistance circuit 13 to the control circuit 8 gradually changes, and the feedback gain of the control circuit 8 gradually decreases.

Therefore, the output current of the DC-DC converter can be gently increased, and thus the load of the motor 20 or the like connected to the inverter device 15 can be gently restarted.

On the other hand, FIG. 5 shows a multi-output DC-comparative example.
The block diagram of a DC converter is shown. This DC-
The DC converter is composed of a resistor R4 and a transistor Tr.
The converter is the same as the converter of the above-described embodiment of FIG. 1 except that the converter is not provided. That is, in the DC-DC converter of this comparative example, the voltage dividing resistors R2 and R3 are connected in parallel to the detection resistance circuit 13 connected to the output detection rectifier circuit 12, and the middle point thereof is the control circuit 8. It is only connected to send a voltage signal.

In the DC-DC converter having such a configuration, while the inverter device 15 connected to the output side performs the normal switching operation, as described above, the resistance value of the detection resistance circuit 13 is the inverter. Since it is set to be the same as the load resistance of the switching element of the switching circuit of the device 15 at the time of switching, the control circuit 8 controls so as to obtain the rated output voltage.

However, when the inverter device 15 stops switching, the charging / discharging loss of the gate of the switching element, that is, the load resistance of the converter is reduced, but the resistance of the detection resistance circuit 13 connected to the detection rectification circuit 12 is reduced. The value remains unchanged.

For this reason, the control circuit 8 controls the detection resistance circuit 13 so that a predetermined output voltage can be obtained despite the decrease in the load of the converter, so that the output of the converter is as shown in FIG. It operates near the operating point E on the output characteristic curve A in the graph, and the output voltage becomes an overvoltage.

Therefore, when such an overvoltage is applied to the gate of the switching element of the inverter device 15, the gate is destroyed by the overvoltage, or an excessive surge voltage is generated at the time of switching to destroy the switching element. I will end up.

Although the three-phase inverter device is connected as a load to the output side of the DC-DC converter in the above embodiment, other loads may be connected. In this case, the switching stop signal sent to the transistor Tr of the resistance switching circuit 14 may be output from the circuit that controls the load as the load current reduction signal.

Further, although the transistor is used in the resistance switching circuit 14, other switching means such as FET may be used. Also, the output of the converter is three-phase,
It is also possible to have two phases or four or more phases.

[Brief description of drawings]

FIG. 1 is a block diagram of a multi-output DC-DC converter showing an embodiment of the present invention.

FIG. 2 is a graph showing output characteristics of a converter.

FIG. 3 is a circuit diagram showing a resistance switching circuit of another embodiment.

FIG. 4 is a circuit diagram showing a resistance switching circuit of still another embodiment.

FIG. 5 is a block diagram of a multi-output DC-DC converter as a comparative example.

[Explanation of symbols]

1-trans, 2-primary winding, 3, 4, 5, 6-secondary winding, 9, 10, 11, 12-rectifier circuit, 13-detection resistance circuit, 14-resistance switching circuit, 15-Inverter device.

Claims (2)

(57) [Claims] 1. A transformer having a primary winding and a plurality of secondary windings, a switch circuit connected to the primary winding of the transformer, and a plurality of switch circuits connected to each of the secondary windings of the transformer. A rectifier circuit, one secondary winding of the plurality of secondary windings is used for output detection, and voltage detection is performed on the output side of the rectifier circuit connected to the secondary winding for output detection. Multi-output DC-DC converter to which a detection resistance circuit for detection is connected, and a control circuit for controlling the switching operation of the switch circuit so that the voltage of the detection resistance circuit has a constant value is connected to the switch circuit. in the output side of the plurality of rectifier circuits for the converter output, inverter
The multi-phase gate drive circuit of the controller device is connected as a load device
And a switching element provided in the gate drive circuit.
Switching stop output when child switching stops
Signal is used as the load current reduction signal,
Load current reduction signal that is output when the load current of the storage device is reduced.
To increase the resistance value of the detection resistance circuit.
A multi-output DC-DC converter, characterized in that a resistance switching means for switching to is provided . 2. A plurality of resistors is connected to the detecting resistor circuit, the transistor is connected to the resistor circuit said detectable as the resistance switching means, according to claim 1, wherein the said transistor switching the connection of the resistor Multi-output DC-DC converter.