JP2001189652A - Driving device for current controlled element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the flow of a through current caused by inverse recovering operation by letting a current flow through an MOS switch for inversely turning on a current controlled transistor when a back electromotive force is generated from an induced load. SOLUTION: When the output of a driving circuit 13 becomes high level, a transistor T1 for driving is turned on and an N type MOS switch 11 is turned off. When the output of the driving circuit 13 becomes low level, on the other hand, the transistor T1 for driving is turned off and the N type MOS switch 11 is turned on. When another transistor T2 for driving is turned off in such a state, the back electromotive force is generated from an induced load L1 and a voltage at a point P shown in the figure is increased by the back electromotive force. When the voltage at the point P becomes higher than that at the base terminal of the transistor T1 for driving, a current flows in a direction C as shown in the figure through the N type MOS switch 11. As a result, the transistor T1 for driving is inversely turned on and a loop current generated by the back electromotive force flows in a direction B shown in the figure so that the flow of the through current caused by the inverse recovering operation can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device for a current control element for supplying a driving current to an inductive load.

[0002]

2. Description of the Related Art A drive device for a current control type element for driving an inductive load is used, for example, in a chopper circuit and an H-bridge circuit for controlling an induction motor. In these circuits, a protection circuit is provided to protect the current control type element from a back electromotive force generated by an inductive load. FIG. 7 is a diagram showing a part of an H-bridge circuit provided with a protection circuit, which is described in, for example, Japanese Patent Application Laid-Open No. 8-84060. In FIG. 7, T101 and T102 are current control type switching transistors (hereinafter simply abbreviated as driving transistors) for supplying a driving current to an inductive load L1 composed of a motor or the like, and drive circuits respectively connected to base terminals. It is driven by 103 and 133. The power supply voltage Vcc is connected to the collector terminal of the driving transistor T101, and the emitter terminal of the driving transistor T102 is grounded. An inductive load L1 is connected between the emitter terminal of the driving transistor T101 and the collector terminal of the driving transistor T102.

The diodes 102, 1 are connected between the emitter terminals and the base terminals of the driving transistors T101, T102, respectively.
22 is connected. By flowing a current due to the back electromotive force generated from the inductive load L1 to these diodes 102 and 122, the destruction of the driving transistors T101 and T102 is prevented. For example, when the driving transistor T102 is turned on by the driving circuit 133, a current flows in a direction indicated by A in the figure. Thereafter, when the driving transistor T102 is turned off by the driving circuit 133, a back electromotive force is generated from the inductive load L1, and the potential at point P in the figure rises due to the back electromotive force. The potential at point P is the driving transistor T101
When the potential becomes higher than the potential of the base terminal, the diode 102 is forward-biased, and a current flows in a direction indicated by C in FIG. Then, the driving transistor T101 is turned on in the reverse direction, and the circulating current due to the back electromotive force flows in the direction indicated by B in the drawing.

[0004]

However, if the driving transistor T102 is turned on again while the driving transistor T101 is turned on in the reverse direction, the driving transistor T101 enters a reverse recovery operation and the P-point is turned on. , A current flows in the direction A again. For this reason, the electric charge accumulated in the driving transistor T101 stays as it is. As a result, while the driving transistor T101 is in the off state, a current flows in the direction from the collector to the emitter, that is, in the forward direction, and the driving transistor T101 is turned off.
In addition, there is a problem that a large through current flows through the driving transistor T102.

An object of the present invention is to provide a driving device for a current-controlled element in which electric charges accumulated in a current-controlled transistor are sufficiently suppressed.

[0006]

The present invention will be described with reference to FIGS. 1 and 5 showing one embodiment. (1) The invention according to claim 1 includes a current control type transistor T1 for supplying a drive current to an inductive load L1 connected to a drive terminal (emitter terminal), and the current control type transistor T1 is inductive load. For a current control type device having a protection means for supplying a current due to a back electromotive force generated from the inductive load L1 to the control terminal (base terminal) of the current control type transistor T1 so as to be turned on in a direction opposite to the driving direction of L1. Applied to driving devices. The protection unit includes a switching unit 11 for turning on / off a drive terminal (emitter terminal) and a control terminal (base terminal), and a period during which at least the current control transistor T1 is turned on in the reverse direction.
The above-described object is achieved by providing the switching control unit 14 that turns on the switching unit 11 during a period in which the current control transistor T1 is reversely recovered from turning on in the reverse direction. (2) According to a second aspect of the present invention, in the current control type element driving device of the first aspect, the switching means 11
Indicates that the MOS transistor is turned on at least during a period when the current control transistor T1 is turned on in the reverse direction and during a period when the current control transistor T1 is reversely recovered from turning on in the reverse direction. Features. (3) According to a third aspect of the present invention, in the current control type element driving device according to the second aspect, the drive control means 13 for outputting a control signal for turning on / off the current control type transistor T1 is provided. The control means turns on the MOS transistor in synchronization with a control signal from the drive control means for turning off the current control transistor T1. (4) The current controlling element driving device according to the fourth aspect of the present invention is arranged on the upper arm side with respect to the inductive load L1 to supply a driving current in the first direction and to drive the inductive load L1. A first current control type transistor T1 for flowing a current due to a back electromotive force generated in the reverse direction, and a first current control type transistor T1 connected in series with the first current control type transistor T1 and located on the lower arm side with respect to the inductive load L1. A second current-controlled transistor T2 for supplying a drive current in a second direction different from the first direction and for flowing a current due to a back electromotive force generated from the inductive load L1 in a reverse direction; First drive control means 13 for turning on / off transistor T1
A second drive control means 33 for turning on / off the second current control transistor T2; and a drive terminal to which the inductive load L1 of the first current control transistor T1 is connected.
(Emitter terminal) and the first current control transistor T
A first switching means 11 for turning on / off between the first control terminals (base terminals), a period during which at least the first current control type transistor T1 is on in the reverse direction, and a first current control type transistor T1. During the period in which the first switching means 11 recovers from the reverse ON state.
The first switching control means 14 for turning on the
A second terminal for turning on / off a terminal (emitter terminal) of the current control transistor T2 different from the drive terminal to which the inductive load L1 is connected and a control terminal (base terminal) of the second current control transistor T2. Switching means 31
At least during the period when the second current-controlled transistor T2 is turned on in the reverse direction and during the period when the second current-controlled transistor T2 is reversely recovered from being turned on in the reverse direction. By providing the second switching control means 34 for turning on, the above-described object is achieved. (5) The invention according to claim 5 is the invention according to claim 4, wherein at least the first drive control means 13 'and the first switching control means 14' are provided with the first current control transistor T1. Floating power supplies 40 and 44 for supplying a power supply voltage based on the potential of the driving terminal (emitter terminal)

In the section of the means for solving the above-mentioned problems, the present invention is associated with the drawings of the embodiments for easy understanding of the present invention, but the present invention is not limited to the embodiments. is not.

[0008]

According to the present invention as described in detail above, the following effects can be obtained. (1) In the invention according to claims 1 to 3, switching means is provided between the control terminal and the driving terminal of the current control type transistor, and at least a period in which the current control type transistor is turned on in the reverse direction, and The switching means is turned on during the period of reverse recovery from turning on. Therefore, a current for turning on the current control type transistor in the reverse direction flows through the turned on switching means, so that the loss can be reduced as compared with the conventional case where a circulating current is passed through a circulating diode. As a result, the size of the semiconductor device can be reduced.

Further, in addition to the above (1), for example, even when electric charge is accumulated in the current control type transistor, the accumulated electric charge is turned on when the current control type transistor enters the reverse recovery operation. Through the switched switching means, it is possible to escape to the control terminal side of the current control type transistor with low loss. Therefore, the current control transistor is turned off, so that a large current flowing through the current control transistor is prevented from flowing. (2) In the invention according to claims 4 and 5, the first current control transistor for supplying a driving current in the first direction to the inductive load, and the first current control transistor to supply the driving current to the inductive load in the first direction. The switching means according to the first to third aspects is provided for each of the second current control transistors for supplying the driving current in the different second directions. Then, at least a period in which the current control type transistors T1 and T2 are turned on in the reverse direction, and the current control type transistors T1 and T2
In the period in which No. 2 is reversely recovered from on in the reverse direction, each switching means is turned on. Therefore, the effect (1) can be obtained regardless of whether the direction of the current flowing through the inductive load is the first direction or the second direction.

(3) According to the fifth aspect of the present invention, at least the first drive control means and the first switching control means located on the upper arm side are used for driving the first current control transistor. A power supply voltage is supplied from a floating power supply having a terminal as a reference potential. Therefore, for example, even if the potential of the drive terminal of the first current control transistor fluctuates, the predetermined voltage is not changed to the first voltage.
To the first drive control means and the first switching control means. As a result, the circuit design of the first drive control means and the first switching control means is facilitated, and the effect of reducing the development cost is obtained.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. First Embodiment FIG. 1 is a circuit diagram of a current control type semiconductor device according to a first embodiment of the present invention, which is a part of an H-bridge circuit for controlling an induction motor, for example. In FIG. 1, current-controlled switching transistors (hereinafter simply referred to as driving transistors) T1 and T2 are switching devices that supply a driving current to an inductive load L1 such as a motor, and are each connected to a base terminal. Drive circuit 1
Driven by 3, 33. The power supply voltage Vcc is connected to the collector terminal of the driving transistor T1, and the emitter terminal of the driving transistor T2 is grounded. An inductive load L1 is connected between the emitter terminal of the driving transistor T1 and the collector terminal of the driving transistor T2. An N-type MOS switch 11 is provided between the emitter terminal and the base terminal of the driving transistor T1.
In the N-type MOS switch 11, a parasitic diode 12 is built in parallel with the switch due to the structure of the device, that is, between the drain terminal and the source terminal. The opening and closing of the N-type MOS switch 11 is controlled by the drive circuit 14. An N-type MOS switch 31 and a diode 32 incorporated in the switch 31 are connected in parallel between the emitter terminal and the base terminal of the driving transistor T2, similarly to the driving transistor T1. N-type MOS switch 31
Are controlled to be opened and closed by a drive circuit 34.

FIG. 2 is an example of a circuit diagram constituting the driving circuits 13 and 33. In FIG. 2, drive circuits 13 and 33 include a switching transistor 21 and a resistor 2
2 and a impedance adjustment circuit IA including a transistor 24, a capacitor 23, a resistor 25, and a diode 26. The switching circuit SC outputs an output terminal 27 according to the level of the voltage signal input from the input terminal 20 of the drive circuits 13 and 33.
Outputs a driving current for driving the driving transistors T1 and T2. The impedance adjustment circuit IA changes the impedance between the output terminals 27 of the drive circuits 13 and 33 and the ground based on the level of the voltage signal input from the input terminal 20.

The operation of the drive circuit 13 will be described. When a high-level voltage signal is input to the input terminal 20 of the drive circuit 13, the switching transistor 21 is turned on, so that a drive current flows through the resistor 22 and the diode 26. This drive current is supplied from the output terminal 27 to the base terminal of the drive transistor T1 (FIG. 1) to drive the drive transistor T1 (FIG. 1). At this time, by charging the capacitor 23 of the impedance adjustment circuit IA, the transistor 24 is turned on after a lapse of a predetermined time. When the transistor 24 is turned on, the impedance between the output terminal 27 and the ground, that is, the impedance between the base terminal of the driving transistor T1 (FIG. 1) and the ground decreases.

Next, when a low-level voltage signal is input to the input terminal 20 of the drive circuit 13, the switching transistor 21 is turned off, so that the output terminal 27 is connected to the base terminal of the drive transistor T1 (FIG. 1). The drive current stops flowing. At this time, the electric charge accumulated in the capacitor 23 is discharged through the transistor 24 and the resistor 25, and the on state of the transistor T24 is maintained for a while after the switching transistor 21 is turned off. That is, the impedance between the base terminal and the ground of the driving transistor T1 (FIG. 1) is kept low for a while after the driving transistor T1 (FIG. 1) is turned off. Therefore, by utilizing this period, it is possible to quickly extract the charge accumulated in the collector region of the driving transistor T1 (FIG. 1) to the base region. As a result, the turn-off time of the driving transistor T1 (FIG. 1) is reduced.

When the discharge of the capacitor 23 is completed, no current flows to the base terminal of the transistor T24, and the transistor T24 is turned off. As a result, the impedance between the base terminal and the ground of the driving transistor T1 (FIG. 1) increases.

The driving circuit 33 operates similarly to the driving circuit 13. That is, a driving current for driving the driving transistor T2 (FIG. 1) is output from the output terminal 27 in accordance with the level of the voltage signal input to the input terminal 20 of the driving circuit 33, and the driving current is input to the input terminal 20 of the driving circuit 33. The impedance between the base terminal and the ground of the driving transistor T2 (FIG. 1) is changed based on the level of the input voltage signal.

Drive circuits 14 and 34 invert the outputs of drive circuits 13 and 33, for example, to generate drive signals for N-type MOS switches 11 and 31. For the above inversion, an inverter of a logic circuit may be used. The drive circuits 14 and 34 output a low-level drive signal when a drive current for driving the drive transistors T1 and T2 is output from the output terminal 27 of the drive circuits 13 and 33. When a driving current for driving the driving transistors T1 and T2 is not output from the output terminals 27 of the driving circuits 13 and 33, a high-level driving signal is output. As a result, the N-type MOS switch 11
Is controlled to be turned off when the driving transistor T1 is turned on and to be turned on when the driving transistor T1 is turned off. The N-type MOS switch 31 is controlled to be turned off when the driving transistor T2 is turned on and to be turned on when the driving transistor T2 is turned off.

The operation of the above-described current control type semiconductor device will be described in detail. —Upper Arm— FIG. 3 shows an upper arm portion of the circuit diagram of FIG. 1, that is, the signal Sig1 output from the output terminal 27 of the drive circuit 13.
3. The signal Si output from the output terminal 27 of the drive circuit 33
g33 and N-type MOS output from drive circuit 14
6 is a time chart of a drive signal Sig14 of the switch 11. When the output signal Sig13 of the drive circuit 13 becomes high level (t1 in FIG. 3), a drive current flows through the base terminal of the drive transistor T1, and the drive transistor T1 is turned on in the forward direction and the direction indicated by Z in FIG. Current flows through At this time, the impedance adjustment circuit in the drive circuit 13 described above is used.
By the action of IA, the impedance between the base terminal and the ground of the driving transistor T1 decreases.

When the output signal Sig13 of the drive circuit 13 goes low (t2 in FIG. 3), no drive current flows through the base terminal of the drive transistor T1, and the drive transistor T1 turns off. Output signal Si of control circuit 13
g13 changes to low level for a while, that is,
For a while after the driving transistor T1 is turned off, the impedance adjustment circuit in the driving circuit 13 described above is used.
By the action of IA, the state where the impedance between the base terminal and the ground of the driving transistor T1 is low is maintained. During this period, the charge accumulated in the collector region of the driving transistor T1 is drawn out to the ground via the base terminal of the driving transistor T1. When the discharge of the capacitor 23 (FIG. 2) of the impedance adjustment circuit IA ends, the impedance between the base terminal and the ground of the driving transistor T1 increases.

On the other hand, in FIG. 1, considering the operation of the lower arm portion of the circuit diagram, the driving transistor T
When the driving circuit T2 is turned on from the off state by the driving circuit 33 while the electric charge accumulated in the collector region 1 is being drawn to turn off the driving transistor T1 (t11 in FIG. 3), A in FIG.
The current flows in the direction shown in FIG. Thereafter, when the driving transistor T2 is turned off by the driving circuit 33 (FIG. 3).
At t3), a back electromotive force is generated from the inductive load L1, and the back electromotive force increases the potential at point P in FIG. When the potential of the point P becomes higher than the potential of the base terminal of the driving transistor T1, at this time, the driving circuit 1
Since the N-type MOS switch 11 is turned on by the operation of 4, a current flows in the direction shown by C in FIG. 1 from the source terminal to the drain terminal of the N-type MOS switch 11. At this time, as described above, the impedance between the base terminal and the ground of the driving transistor T1 is increased,
When the driving transistor T1 is turned on in the reverse direction,
A current flows in the opposite direction from the emitter terminal to the collector terminal, that is, in the direction shown in FIG.

Since the current for turning on the driving transistor T1 in the reverse direction flows not through the diode 12 built in the N-type MOS switch 11, but through the ON-state N-type MOS switch 11 having a lower impedance than the diode 12, The loss is lower than in the case of flowing through No. 12.

When the driving circuit T2 is turned on again by the driving circuit 33 (t4 in FIG. 3) while the current flowing in the directions indicated by B and C, that is, the circulating current is flowing, the driving transistor T1 shifts to the reverse recovery operation. At this point, although the impedance between the base terminal and the ground of the driving transistor T1 is in a high state, the electric charge accumulated in the collector region of the driving transistor T1 does not stay because the N-type MOS switch 11 is turned on. . That is, the electric charge in the collector region of the driving transistor T1 is drawn from the base terminal of the driving transistor T1 to the emitter terminal side of the driving transistor T1 through the N-type MOS switch 11. As a result, the driving transistor T1 is turned off, and no large through current flows from the collector terminal of the driving transistor T1 to the emitter terminal.

Thereafter, when the driving transistor T2 is turned off again by the driving circuit 33 (t5 in FIG. 3), the driving transistor T1 is turned on in the reverse direction and the emitter terminal is turned on, as in the case of the timing t3 described above. Circulating current flows from the collector terminal to the collector terminal. After that, when the output signal Sig13 of the drive circuit 13 goes high (t6 in FIG. 3), a drive current flows through the base terminal of the drive transistor T1. As a result, when the driving transistor T1 is turned on in the forward direction, the same operation as at the timing t1 described above is repeated.

FIG. 4 shows a signal Sig 33 output from the output terminal 27 of the drive circuit 33, a signal Sig 13 output from the output terminal 27 of the drive circuit 13, and N output from the drive circuit 34.
6 is a time chart of a drive signal Sig34 of the type MOS switch 31. FIG. 5 is a diagram for explaining a lower arm portion of the circuit diagram of FIG. In FIG. 4, when the output signal Sig33 of the driving circuit 33 becomes high level (t1 ′ in FIG. 4), a driving current flows through the base terminal of the driving transistor T2,
The driving transistor T2 is turned on in the forward direction, and a current flows in the direction shown by G in FIG. At this time, the impedance between the base terminal and the ground of the driving transistor T2 is reduced by the action of the impedance adjusting circuit IA in the driving circuit 33 described above.

When the output signal Sig33 of the driving circuit 33 becomes low level (t2 'in FIG. 4), the driving transistor T2
No drive current flows through the base terminal of the drive transistor T2, and the drive transistor T2 is turned off. Output signal of control circuit 33
For a while after the Sig 33 changes to the low level, that is, for a while after the driving transistor T2 is turned off, the operation of the impedance adjustment circuit IA in the driving circuit 33 described above causes the base terminal of the driving transistor T2 to have a negative polarity. The state where the impedance between the grounds is low is maintained.
During this period, the electric charge accumulated in the collector region of the driving transistor T2 is drawn out to the ground through the base terminal of the driving transistor T2. When the discharge of the capacitor 23 (FIG. 2) of the impedance adjustment circuit IA is completed,
The impedance between the base terminal and the ground of the driving transistor T2 increases.

On the other hand, in FIG. 5, considering the operation of the upper arm portion of the circuit diagram, the driving transistor T
When the drive transistor T1 is turned on from the off state by the drive circuit 13 while the charge accumulated in the collector region 2 is being drawn to turn off the drive transistor T2 (t11 'in FIG. 4). 5 flows in the direction shown in FIG. Thereafter, when the driving transistor T1 is turned off by the driving circuit 13 (t3 ′ in FIG. 4), a back electromotive force is generated from the inductive load L1, and
The back electromotive force causes the potential at point P in FIG. 5 to drop. P
When the potential of the point becomes lower than the potential of the emitter terminal of the driving transistor T2, that is, the ground potential, the potential of the base terminal of the driving transistor T2 becomes lower than the potential of the emitter terminal. At this point, since the N-type MOS switch 31 is turned on by the operation of the drive circuit 34, a current flows from the source terminal of the N-type MOS switch 31 through the drain terminal in the direction indicated by I in FIG. At this time, as described above, the impedance between the base terminal and the ground of the driving transistor T2 is increased, so that the driving transistor T2 is turned on in the reverse direction, that is, in the reverse direction from the emitter terminal to the collector terminal, that is, 5 flows in the direction indicated by H in FIG.

Since the current for turning on the driving transistor T2 in the reverse direction flows not through the diode 32 built in the N-type MOS switch 31, but through the ON-state N-type MOS switch 31 having a lower impedance than the diode 32, The loss is lower than that in the case of flowing through the P.32.

When the driving circuit T1 is turned on again by the driving circuit 13 (t4 'in FIG. 4) while the current flowing in the directions indicated by I and H, that is, the circulating current is flowing, the driving The transistor T2 shifts to the reverse recovery operation. At this point, although the impedance between the base terminal and the ground of the driving transistor T2 is in a high state, the electric charge accumulated in the collector region of the driving transistor T2 does not stay because the N-type MOS switch 31 is turned on. . That is, the electric charge in the collector region of the driving transistor T2 is drawn from the base terminal of the driving transistor T2 through the N-type MOS switch 31 to the emitter terminal side of the driving transistor T2. As a result, the driving transistor T2 is turned off, and no large through current flows from the collector terminal of the driving transistor T2 to the emitter terminal.

Thereafter, when the driving transistor T1 is turned off again by the driving circuit 13 (t5 'in FIG. 4),
As in the case of the timing t3 'described above, the driving transistor T2 is turned on in the reverse direction, and a circulating current flows from the emitter terminal to the collector terminal. After that, when the output signal Sig33 of the drive circuit 33 becomes high level (t6 'in FIG. 4), a drive current flows through the base terminal of the drive transistor T2. As a result, when the driving transistor T2 is turned on in the forward direction, the same operation as the above-described timing t1 'is repeated.

According to the first embodiment described above,
The following operational effects can be obtained. (1) N-type MOS switches 11 and 31 are respectively connected between the base terminals and the emitter terminals of the driving transistors T1 and T2, and the N-type MOS switches 11 and 31 are connected when the driving transistors T1 and T2 are turned on. The N-type MOS switches 11 and 31 are turned on when the driving transistors T1 and T2 are turned off, respectively. Therefore, the current that turns on the transistors T1 and T2 in the reverse direction flows through the N-type MOS switches 11 and 31 in the ON state, so that the loss can be reduced as compared with the conventional case where the circulating current flows through the circulating diode. As a result, the size of the semiconductor device can be reduced.

(2) In addition to the above (1), when the driving transistors T1 and T2 enter a reverse recovery operation, the charges (carriers) accumulated in the collector regions of the driving transistors T1 and T2 are turned on. Drive transistors T through N-type MOS switches 11 and 31, respectively.
1 and T2 can be released to the emitter terminal side with low loss. Therefore, there is no charge remaining in the collector region, and the driving transistors T1 and T2 are turned off, thereby preventing a through current from flowing from the collector terminals of the driving transistors T1 and T2 to the emitter terminals. As a result, it is possible to prevent the drive transistor not performing the reverse recovery operation from being destroyed by the through current.

(3) Since the upper and lower arms are symmetrical, the driving transistors T1 and T2
In other words, the above-described effects (1) and (2) can be obtained regardless of whether the direction of the current flowing through the inductive load L1 in FIG. (4) Since the on state of the transistor T24 is maintained for a while after the switching transistor 21 is turned off by the impedance adjusting circuit IA, the base terminals of the driving transistors T1 and T2
The impedance between the grounds is kept low. As a result, the charges accumulated in the collector regions of the driving transistors T1 and T2 can escape to the base region, and the turn-off time of the driving transistors T1 and T2 is reduced.

In the circuits of FIGS. 1 and 5 described above,
As a circuit component constituting the upper arm, a component having a higher withstand voltage than a circuit component constituting the lower arm is used. That is, the drive circuit 13 and the drive circuit 1 forming the upper arm
4 is a component that allows at least the power supply voltage Vcc. On the other hand, the drive circuit 33 and the drive circuit 34 constituting the lower arm only need to be components that allow at least the voltage between the point P and the ground.

In the above description, both the upper and lower arms of the current control type semiconductor device, that is, the driving transistor T1
And T2, N-type MOS switches 11 and 3 respectively between their emitter and base terminals.
1 are connected, and the N-type MOS switches 11 and 31 are controlled to open / close in response to the off / on driving of the driving transistors T1 and T2, respectively. However, an N-type MOS switch is connected between the emitter terminal and the base terminal of at least one of the driving transistors T1 and T2, and the N-type MOS switch is opened / closed in response to off / on driving of the driving transistor.
Closed control can also be performed. In this case, since a through current does not flow through the driving transistor to which the N-type MOS switch is connected, it is possible to prevent the other driving transistor from being damaged by the through current.

In the above description, the driving transistor T1
Since a large circulating current needs to flow in the reverse direction from the emitter terminal of T2 and the collector terminal of T2, it is desired that the reverse current amplification factor h'FE of the driving transistors T1 and T2 is sufficiently large. In this regard, the driving transistors T1 and T2 described above may be, for example, general power bipolar transistors. In particular, the semiconductor devices disclosed in Japanese Patent Application Laid-Open No. 6-252408 (current control transistors So-called GTB
T) is particularly effective as the driving transistor of the present invention because the reverse current amplification factor h′FE is substantially equal to the forward current amplification factor hFE.

Second Embodiment FIG. 6 is a circuit diagram of a current-controlled semiconductor device according to a second embodiment of the present invention. Compared to the first embodiment,
The difference is that a power supply voltage is supplied to each drive circuit by the transformer 40. Driving transistors T1 and T2
The drive circuits connected to are the same as in the first embodiment, but since the voltage of the power supply supplied to each drive circuit is different, the same circuit numbers as those in the first embodiment are denoted by “′”. To represent. That is, a driving circuit 13 'for driving the driving transistor T1, a driving circuit 14' for driving the N-type MOS switch 11, a driving circuit 33 'for driving the driving transistor T2, and a driving circuit 34 for driving the N-type MOS switch 31. ′ Is supplied with a power supply voltage from the transformer 40.

In FIG. 6, the power supply circuit is
And smoothing circuits 44 and 45. Transformer 40
The voltage V1 input to both ends of the primary coil 41 is transformed into a voltage V2 across the secondary coil 42 of the transformer 40 and a voltage V3 across the secondary coil 43. The voltage V2 at both ends of the secondary coil 42 is smoothed by the smoothing circuit 44, and the voltage e1 at the output terminal of the smoothing circuit 44 is applied to the drive circuit 13 '.
Is applied to The voltage V3 at both ends of the secondary coil 43 is smoothed by the smoothing circuit 45, and the voltage e at the output terminal of the smoothing circuit 45 is output.
2 is applied to the drive circuit 13 '. The reference potential of the voltage V2 at both ends of the secondary coil 42 of the transformer 40 and the voltage e1 at the output end of the smoothing circuit 44 is at point P in FIG.
This is the potential of the emitter terminal of the driving transistor T1.
That is, the secondary coil 42 of the transformer 40 and the smoothing circuit 4
4 and the terminal on the low voltage side of the drive circuit 13 'are connected to the emitter terminal of the drive transistor T1, respectively. On the other hand, the reference potential of the voltage V3 at both ends of the secondary coil 43 of the transformer 40 and the voltage e2 of the output terminal of the smoothing circuit 45 is the ground potential in the figure. That is, the transformer 40
Secondary coil 43, smoothing circuit 45, and drive circuit 3
Terminals on the low voltage side of 3 'are grounded.

When the driving transistors T1 and T2 are operated in the same manner as in the first embodiment, the potential at the point P in FIG. 6, that is, the potential at the emitter terminal of the driving transistor T1 and the potential at the collector terminal of the driving transistor T2 becomes As described above, the voltage rises and falls due to the back electromotive force from the inductive load L1. However, the value of the voltage e1 at the output terminal of the smoothing circuit 44 based on the potential at the point P is kept at a predetermined value. Therefore, the circuit design of the drive circuit 13 'and the drive circuit 14' to which the power supply voltage is supplied by the smoothing circuit 44 is facilitated, and the drive circuit 13 'and the drive circuit 14' are different from the drive circuit 13 'and the drive circuit 14' as in the first embodiment. Therefore, it is not necessary to use circuit components having a high withstand voltage.

In the second embodiment described above, the power supply voltage is supplied to the respective drive circuits 13 'and 33' in a floating state by using the transformer 40. Therefore, the circuit design of each drive circuit 13 'and drive circuit 33' becomes easy,
The effect of reducing the development cost can be obtained. In addition, since it is not necessary to use components with a high withstand voltage, smaller components can be used, so that component mounting is simplified, and
The device can be reduced in size.

The correspondence between each component in the claims and each component in the embodiment of the invention will be described. The emitter terminal is a drive terminal, the drive transistor T1 is a current control transistor and the first transistor. A current control transistor; a base terminal as a control terminal; an N-type MOS switch 11 as a switching means and a first switching means;
Are the switching control means and the first switching control means, the driving transistor driving circuit 13 is the driving control means, the driving transistor T2 is the second current control type transistor, and the driving transistor driving circuits 13 and 13 '. Are connected to the first drive control means, the drive transistor drive circuit 33 is connected to the second drive control means, and the emitter terminal of the drive transistor T2 is connected to the terminal to which the inductive load of the second current control transistor is connected. N to different terminals
Type MOS switch 31 is connected to the second switching means by N
The drive circuit 34 of the type MOS switch corresponds to the second switching control means, and the transformer 40 and the smoothing circuit 44 correspond to the floating power supply.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a current control type semiconductor device according to a first embodiment.

FIG. 2 is a diagram illustrating an example of a circuit constituting drive circuits 13 and 33.

FIG. 3 is a time chart of signals of an upper arm portion of the circuit diagram of FIG. 1;

FIG. 4 is a time chart of signals of a lower arm portion of the circuit diagram of FIG. 1;

FIG. 5 is a diagram for explaining a lower arm portion of the circuit diagram of FIG. 1;

FIG. 6 is a circuit diagram of a current control type semiconductor device according to a second embodiment.

FIG. 7 is a circuit diagram showing a part of an H-bridge circuit provided with a protection circuit according to a conventional technique.

[Explanation of symbols]

11, 31 ... N-type MOS switch, 12, 32 ... built-in diode, 13, 13 ', 33, 33' ... drive transistor drive circuit, 14, 14 ', 34, 34' ... N-type MOS switch drive circuit , 40 ... trance,
41: Primary coil, 42, 43: Secondary coil, 44, 45: Smoothing circuit, L1: Inductive load, T1, T2: Driving transistor

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) EY12 EY17 EY21 EY29 EZ00 EZ07 EZ21 EZ63 GX01 GX04

Claims (5)

[Claims] A current control transistor for supplying a drive current to an inductive load connected to a drive terminal, wherein the current control transistor is turned on in a direction opposite to a direction in which the inductive load is driven. A current control type element driving device comprising protection means for supplying a current due to a back electromotive force generated from the inductive load to a control terminal of the current control type transistor, wherein the protection means comprises: the drive terminal and the control terminal. Switching means for turning on / off the switch, and the switching means at least during a period in which the current-controlled transistor is turned on in the reverse direction and a period in which the current-controlled transistor is reversely recovered from on in the reverse direction. And a switching control means for turning on the current control element. 2. The current controlling element driving device according to claim 1, wherein the switching means is constituted by a MOS transistor, and at least a period during which the current controlling transistor is turned on in the reverse direction; The current control type element driving device, wherein the MOS transistor is turned on during a period when the current control type transistor is reversely recovered from the reverse ON state. 3. The current controlling element driving device according to claim 2, further comprising: driving control means for outputting a control signal for turning on / off the current controlling transistor; A current control type element driving device, wherein the MOS transistor is turned on in synchronization with a control signal for turning off the current control type transistor by means. 4. A method according to claim 1, wherein a driving current is supplied to the inductive load on the upper arm side in a first direction, and a current caused by a back electromotive force generated from the inductive load flows in a reverse direction.
A current-controlled transistor of, and connected in series with the first current-controlled transistor,
The first arm is located on the lower arm side with respect to the inductive load.
A second current-controlled transistor that supplies a drive current in a second direction different from the direction of the above, and flows a current due to a back electromotive force generated from the inductive load in the reverse direction; and the first current-controlled transistor. First drive control means for turning on / off, second drive control means for turning on / off the second current control transistor, and the inductive load of the first current control transistor are connected. First switching means for turning on / off between a driving terminal and a control terminal of the first current control type transistor, a period in which at least the first current control type transistor is on in the reverse direction, and A first switching for turning on the first switching means during a period when the first current control transistor is reversely recovered from the on in the reverse direction; Control means; and second switching means for turning on / off a terminal of the second current control transistor which is different from a drive terminal to which the inductive load is connected and a control terminal of the second current control transistor. At least during the period in which the second current-controlled transistor is turned on in the reverse direction and during the period in which the second current-controlled transistor is reversely recovered from on in the reverse direction. And a second switching control means for turning on the means. 5. The current control type element driving device according to claim 4, wherein at least the first drive control means and the first switching control means are driven by the first current control type transistor. And a floating power supply for supplying a power supply voltage based on the potential of the terminal for current control.