H-bridge driver

Details H-bridge driver H-bridge driver

2001-02-27

2004-06-22

Callahan, Timothy P. (Department: 2816)

Miscellaneous active electrical nonlinear devices, circuits, and

Gating

Utilizing three or more electrode solid-state device

C327S424000, C327S494000, C327S587000, C327S588000

Reexamination Certificate

active

06753717

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an H-bridge driver having a drive signal generating circuit for generating a square-wave signal as a drive signal for driving an H-bridge that is used to drive a load from both ends thereof in a complementary fashion.
2. Description of the Prior Art
FIG. 4
shows a conventional H-bridge driver for driving a load such as the primary coil of a transformer. This H-bridge driver includes, for example, an H-bridge
400
consisting of two complementary connection circuits
300
-
1
and
300
-
2
, of which each is composed of a p-channel MOS FET (hereinafter referred to as the “pMOS”)
301
and an n-channel MOS FET (hereinafter referred to as the “nMOS”)
302
. Within each of the complementary connection circuits
300
-
1
and
300
-
2
, the source of the pMOS
301
is connected to a supply voltage V
CC
, the source of the nMOS
302
is connected to ground GND, and the drains of the pMOS
301
and the nMOS
302
are connected together. In this circuit configuration, to drive the H-bridge
400
, a signal P
1
output from a logic circuit
100
′ is fed through a buffer amplifier
200
-
1
′ directly to the gates of the pMOS
301
and the nMOS
302
of the complementary connection circuit
300
-
1
, and a signal P
2
output from the logic circuit
100
′, which is an inverted version of the signal P
1
, is fed through a buffer amplifier
200
-
2
′ directly to the gates of the pMOS
301
and the nMOS
302
of the complementary connection circuit
300
-
2
.
In this circuit configuration, let the threshold level at which the p-channel MOS FETs turn on be V
thp
, and let the threshold level at which the n-channel MOS FETs turn on be V
thn
Moreover, assume that the high-level voltage of the pulse signals P
1
and P
2
is set to be higher than V
CC
−V
thp
and the low-level voltage thereof is set to be lower than V
thn
. Under these conditions, when the pulse signal P
1
is at the low level and the pulse signal P
2
is at the high level, in the complementary connection circuit
300
-
1
, the pMOS
301
is on and the nMOS
302
is off, and, in the complementary connection circuit
300
-
2
, the pMOS
301
is off and the nMOS
302
is on. As a result, a current flows from the supply voltage V
CC
to the pMOS
301
of the complementary connection circuit
300
-
1
, then to a load
500
, then to the nMOS
302
of the complementary connection circuit
300
-
2
, and then to ground GND. By contrast, when the pulse signal P
1
is at the high level and the pulse signal P
2
is at the low level, in the complementary connection circuit
300
-
1
, the pMOS
301
is off and the nMOS
302
is on, and, in the complementary connection circuit
300
-
2
, the pMOS
301
is on and the nMOS
302
is off. As a result, a current flows from the supply voltage V
CC
to the pMOS
301
of the complementary connection circuit
300
-
2
, then to the load
500
, then to the nMOS
302
of the complementary connection circuit
300
-
1
, and then to ground GND. In this way, the load
500
is driven from both ends thereof in a complementary fashion.
However, in this conventional H-bridge driver, since the H-bridge
400
is driven by directly using the square-wave pulse signals (i.e. signals containing high-frequency components) output from the logic circuit
100
′, the inductance component of the load
500
causes high-frequency noise of the order of tens of millivolts. For this reason, conventional H-bridge drivers are unusable in audio, visual, and similar applications.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an H-bridge driver that has a drive signal generating circuit for generating a square-wave signal as a drive signal for driving an H-bridge and that permits significant reduction of the high-frequency noise caused by the inductance component of the load of the H-bridge.
To achieve the above object, according to the present invention, an H-bridge driver including a drive signal generating circuit for generating a square-wave signal as a drive signal for driving an H-bridge is provided with: a waveform shaping circuit for blunting the drive signal generated by the drive signal generating circuit to drive the H-bridge; and a control circuit for keeping the voltage on the output side of the H-bridge equal to the voltage output from the waveform shaping circuit. In this circuit configuration, a signal having a blunted version of the waveform of the drive signal for driving the H-bridge appears on the output side of the H-bridge.


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