Driver circuit for power device

Details Driver circuit for power device Driver circuit for power device

2003-02-04

2004-01-20

Le, Dinh T. (Department: 2816)

Miscellaneous active electrical nonlinear devices, circuits, and

Signal converting, shaping, or generating

Current driver

C363S034000

Reexamination Certificate

active

06680630

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a driver circuit for power device. More particularly, it relates to a driver circuit for power device preventing malfunction or breakdown while allowing scaledown and cost reduction thereof.
2. Description of the Background Art
FIG. 8
is a circuit diagram illustrating a three-phase inverter circuit and a driver circuit thereof in the background art. A three-phase inverter circuit
100
in
FIG. 8
includes high side switching elements
101
,
103
and
105
, and low side switching elements
102
,
104
and
106
. The three-phase inverter circuit
100
further includes diodes
107
,
109
and
111
respectively connected in parallel to the high side switching elements
101
,
103
and
105
, and diodes
108
,
110
and
112
respectively connected in parallel to the low side switching elements
102
,
104
and
106
.
The high side switching elements
101
,
103
and
105
, and the low side switching elements
102
,
104
and
106
each receive power supplied thereto from a power source
113
. Interconnect lines for connecting the high side switching elements
101
,
103
,
105
and the low side switching elements
102
,
104
,
106
have respective self-inductances as indicated by reference numerals
114
through
121
in FIG.
8
. The high side switching elements
101
,
103
and
105
, and the low side switching elements
102
,
104
and
106
are each an IGBT (insulated gate bipolar transistor).
A Load such as a three-phase motor
122
is connected to the three-phase inverter circuit
100
. A high side switching driver circuit is connected to each one of the high side switching elements
101
,
103
and
105
, and a low side switching driver circuit is connected to each one of the low side switching elements
102
,
104
and
106
. In
FIG. 8
, only a high side switching driver circuit
200
connected to the high side switching element
101
, and a low side switching driver circuit
300
connected to the low side switching element
102
are shown. Those driver circuits respectively connected to the high side switching elements
103
and
105
, and to the low side switching elements
104
and
106
are omitted. The inverter circuit, the high side switching driver circuit, and low side switching driver circuit constitute a driver circuit for power device.
The high side switching driver circuit
200
connected to the high side switching element
101
includes an emitter follower circuit, a high voltage IC
201
, and a power source
202
and capacitors
203
and
204
for driving these circuits. An NPN transistor (on-side emitter follower transistor)
205
and a PNP transistor (off-side emitter follower transistor)
206
constitute the emitter follower circuit of the high side switching driver circuit
200
. Emitter terminals of the transistors
205
and
206
are respectively connected to resistors
207
and
208
, and then commonly connected to the gate terminal of the high side switching element
101
. The capacitor
203
is provided between a high-voltage side power source terminal Vb and a high-voltage side reference terminal Vs in the high voltage IC
201
, and the capacitor
204
is provided between a low-voltage side power source terminal Vcc and a low-voltage side reference terminal Vss in the high voltage IC
201
. An input terminal IN of the high voltage IC
201
receives a driving signal Hi-IN of the high side switching element inputted thereto. The driving signal Hi-IN is outputted from an output terminal OUT of the high voltage IC
201
to the emitter follower circuit.
Similarly, the low side switching driver circuit
300
connected to the low side switching element
102
includes an emitter follower circuit, a high voltage IC
301
, and a power source
302
and capacitors
303
,
304
for driving these circuits. An NPN transistor
305
and a PNP transistor
306
constitute the emitter follower circuit of the low side switching driver circuit
300
. Emitter terminals of the transistors
305
and
306
are respectively connected to resistors
307
and
308
, and then commonly connected to the gate terminal of the low side switching element
102
. The capacitor
303
is provided between a high-voltage side power source terminal Vb and a high-voltage side reference terminal Vs in the high voltage IC
301
, and the capacitor
304
is provided between a low-voltage side power source terminal Vcc and a low-voltage side reference terminal Vss in the high voltage IC
301
. The capacitors
204
and
304
are connected to a power source
309
. AN input terminal IN of the high voltage IC
301
receives a driving signal Low-IN of the low side switching element inputted thereto. The driving signal Low-IN is outputted from an output terminal OUT of the high voltage IC
301
to the emitter follower circuit.
As shown in
FIG. 8
, clamping diodes
209
and
310
are further provided to the high voltage ICs
201
and
301
, respectively. The clamping diodes
209
and
310
each have an anode connected to the low-voltage side reference terminal Vss, and a cathode connected to the high-voltage side reference terminal Vs. As disclosed in Japanese Patent Application Laid-Open No. 10-42575 (1998), the clamping diodes
209
and
310
are operative to protect the high voltage ICs
201
and
301
from negative potential surge (hereinafter referred to as negative surge). Such negative surge is generated by the variation in current with respect to time (di/dt) and the self-inductances
114
through
121
of the interconnect lines when the high side switching elements
101
,
103
and
105
, or the low side switching elements
102
,
104
and
106
are switched for driving the load.
However, the clamping diodes
209
and
310
may not be operative enough to sufficiently protect the high voltage IC
201
of the high side switching driver circuit and the high voltage IC
301
of the low side switching driver circuit, respectively. As a countermeasure therefor, in the three-phase inverter circuit and the driver circuit thereof shown in
FIG. 8
, a resistor
400
is interposed between the emitter terminal of the low side switching element
104
and the power source
309
. When the negative surge is generated, negative surge current flowing in the clamping diodes
209
and
310
is limited so that the high voltage ICs
201
and
301
can be protected. Such technique is disclosed in PCT Publication No. WO 01/59918.
When only the high side switching element
101
and the low side switching element
104
are in ON state and the high side switching element
101
is switched to OFF state, the negative surge is generated in the three-phase inverter circuit and the driver circuit thereof in
FIG. 8
, the detail of which will be given below.
When only the high side switching element
101
and the low side switching element
104
are in ON state, current supplied from the positive pole of the power source
113
flows through the high side switching element
101
, self-inductance
114
, load
122
, self-inductance
117
, low side switching element
104
, and the self-inductance
121
in this order. The current then returns to the negative pole of the power source
113
.
Next, when the high side switching element
101
is switched to OFF state, the current flowing through the load
122
follows the different path. Namely, the current flows through the load
122
, self-inductance
117
, low side switching element
104
, self inductance
120
, diode
108
, self-inductance
115
, and the load
122
in this order. In the course of this current flow, the self inductances
114
,
115
,
120
and
121
of the interconnect lines generate the negative surge.
When such negative surge is generated, the low-voltage side reference terminal Vss and the high-voltage side reference terminal Vs in the high voltage IC
201
of the high side switching driver circuit
200
receive voltage applied thereto. This voltage is the sum of induced voltages of the self-inductances
114
,
115
and
120
, and forward voltage of the diode
108
. The cl

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