Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Current driver
Utility Patent
2000-01-03
2001-01-02
Tran, Toan (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Current driver
C327S427000, C327S542000
Utility Patent
active
06169431
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates to a drive circuit for a controllable semiconductor component, in particular a drive circuit for rapidly switching on a high-side MOS power transistor. The semiconductor component is connected to a first reference potential (for example a positive pole of battery) at its first main terminal and is connected to a load at its second main terminal, and the load furthermore isg connected to a second reference potential (for example negative pole of battery).
Although it can be applied to any controllable semiconductor components, the present invention and also the problem area on which it is based are explained with regard to drive circuits for rapidly switching on a high-side MOS power transistor.
High-side MOS power transistors, which generally have intelligent supplementary circuitry, are widespread in many areas of application, in particular in modern motor vehicle electronics, on account of various advantages, such as, for example, protection against short circuits for the supply and protection against corrosion for the load.
A charge pump is required for switching on the high-side MOS power transistor; however, the charge pump is very slow and thus limits the switch-on speed. This principle does not suffice, therefore, for applications that require a high switch-on speed, for example in the ultrasonic frequency range.
A solution presented is a discrete bootstrap circuit, since an associated bootstrap capacitor cannot be integrated on the chip for viability reasons. A monolithic solution for the high-side MOS power transistor and the drive circuit (drive IC) can scarcely be realized in the case of a self-insulating process, since the free interconnectability of such a process is highly limited.
An alternative presented is a two-chip solution that provides a discrete bootstrap capacitor. This solution can readily be realized using chip-on-chip technology in a housing or else by use of two separately mounted chips.
The separate drive IC chip must also satisfy a number of far-reaching requirements. The internal IC circuit which drives the high-side MOS power transistor must be able to take up the full battery voltage, for example 12 V. This presupposes a power IC fabrication process.
Published, Non-Prosecuted German Patent Application DE 33 14 300 A1 discloses a drive circuit for a high-side NMOS power transistor which is connected between a first reference voltage potential and a load. The drive circuit furthermore has a control signal generating device and a series circuit formed by a capacitor and a diode which is connected between the main terminals of the power transistor and serves as a bootstrap device. Furthermore, provision is made of a controllable switching device in the form of an NPN bipolar transistor, whose base terminal is connected via a phototransistor to a junction point between the power transistor and the load. The aim of the drive circuit is to reduce a switching delay in a power MOSFET push-pull output stage with an optocoupler.
In Published, British Patent Application GB 2 180 422 A, the combination of a charge pump with a bootstrap circuit is provided for driving a semiconductor switch.
Published, Non-Prosecuted German Patent Application DE 0 572 706 A1 describes a drive circuit for a power FET with a load on the source side, in which the power FET is driven via a pump circuit. The pump circuit has an NPN bipolar transistor, a charge store and also a diode. These components are referred to an operating voltage +U
BB
. The control of the NPN bipolar transistor is performed via a MOSFET connected between the base and the collector. The control terminal of the MOSFET is connected to a junction point of the series circuit formed by a resistor and a controllable switch. The series circuit is connected between a high supply potential and a reference-ground potential. The control terminal of the NPN bipolar transistor is furthermore connected via a further resistor to the load.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a drive circuit for a controllable semiconductor component which overcomes the above-mentioned disadvantages of the prior art devices of this general type, which is simple to produce and is in particular an improved drive circuit for a high-side MOS power transistor, which enables the controllable semiconductor component to be switched on more rapidly.
With the foregoing and other objects in view there is provided, in accordance with the invention, in combination with a semiconductor component having a first main terminal connected to a first reference potential, a second main terminal connected to a second reference potential via a load, and a control terminal, a drive circuit for driving the semiconductor component, the drive circuit including:
a control signal generating device generating a control signal for switching the semiconductor component on and off, the control signal generating device has a circuit section operating according to a bootstrap principle and serving for switching on the semiconductor component;
a diode having a first terminal connected to the first reference potential and a second terminal;
a capacitor device having a first terminal connected to the second terminal of the diode for charging the capacitor device via the first reference potential and a second terminal connected to the second main terminal of the semiconductor component;
a series circuit formed of a series resistor and a first controllable NMOS transistor having a control terminal receiving the control signal from the control signal generating device, the series circuit is connected between the first terminal of the capacitor device and the second reference potential;
a controllable PMOS transistor having a control terminal connected to a junction point between the series resistor and the first controllable NMOS transistor, a first main terminal connected to a junction point between the diode and the capacitor device, and a second main terminal;
an NPN bipolar transistor having a collector terminal connected to the first terminal of the capacitor device, an emitter terminal connected to the control terminal of the semiconductor component, and a base terminal connected to the second main terminal of the controllable PMOS transistor;
an inverter receiving the control signal from the control signal generating device and outputting an inverted control signal; and
a resistor device having a second controllable NMOS transistor with a first main terminal connected to the base terminal of the NPN bipolar transistor, a second main terminal connected to the second main terminal of the semiconductor component, and a control terminal receiving the inverted control signal from the inverter.
The drive circuit according to the invention has the particular advantage that the switching device in the form of the NPN bipolar transistor has a high current-carrying capacity and can be switched on rapidly by the switching control device.
The idea underlying the present invention is that the control terminal of the switching element has a fixedly defined potential in the switched-off state.
In accordance with a further preferred development, provision is made of a charge pump circuit for receiving the control signal and outputting a boosted control signal to the control terminal of the semiconductor component. This affords the advantage that the switching device can also remain permanently switched on (pulse width modulation (PWM) duty ratio=100%) should the capacitor device discharge over time.
In accordance with a preferred development, the semiconductor component is an NMOS power transistor.
In accordance with a further preferred development, the first resistor device has a second NMOS transistor, whose first main terminal is connected to the base terminal of the NPN bipolar transistor, whose second main terminal is connected to the second main terminal of the semiconductor component and whose control terminal receives the inverted control signal
Greenberg Laurence A.
Infineon - Technologies AG
Lerner Herbert L.
Stemer Werner H.
Tran Toan
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