JPH0449870A - Semiconductor output circuit - Google Patents

Abstract

PURPOSE:To prevent the breakdown of a MOS transistor or a lead wire by overcurrents by providing an overcurrent detection means between the low voltage power terminal of a H-type bridge connection and the low voltage power source, and inputting the signal detected by the overcurrent detection means so as to clamp a gate control signal and break the transistor on high voltage side. CONSTITUTION:In case that load RL goes wrong and the division between output terminals M and N shorts, or that excessive voltage adds to a power terminal 7 and excessive currents flows to load resistance RL or a power terminal 9, the detection voltage VR at overcurrent detection resistance 16 rises. The current flows to an NPN transistor base, too, and turnes on transistors 5 and 6, and lowers the voltages of gate control signals S1 and S3 on high voltage side, and turns off the MOS transistors 1 and 3 on high voltage side, and prevents the excessie currents which flow to the load resistance RL of output. Hereby, the breakage of a MOS transistor and the fusion of a lead wire which connects it with the lead frame of a chip can be prevented.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to semiconductor output circuits.

[Conventional technology]

Many integrated circuits that drive stepping motors use a so-called H-bridge configuration using MOS transistors in their output circuits.

FIG. 3 is a circuit diagram of an example of an H-type bridge output section of a conventional semiconductor output circuit.

The H-type bridge output section has a high-voltage side pair of n-channel MOS transistors 1.3 and a low-voltage side pair of n-channel MOS transistors 2.4 in a bridge configuration, with a common drain point 18 connected to the high voltage power supply terminal 7, and a common source point 8 connected to the ground terminal. Connected to 9.

The diagonally corresponding control signals S1 and 82 have the same phase, and the control signals S3 and 84 having opposite phases are input to the corresponding control terminals 11 to 14, respectively.

A load RL such as a stepping motor is connected between bridge output terminals M and N.

[Problem to be solved by the invention]

The above-mentioned conventional semiconductor output circuit has a drawback in that the MOS transistor, lead wire, etc. are destroyed by an overcurrent generated when a short-circuit accident occurs in the load.

Furthermore, when the load is a motor, there is a drawback that it continues to rotate due to inertia even in the event of an accident.

[Means to solve the problem]

The semiconductor output circuit of the present invention has an H-type bridge output section in which a gate control signal is input to the gate end of one transistor pair of a bridge configuration having two MOS transistor pairs, and a load is connected between the bridge output terminal pair. In the semiconductor output circuit, an overcurrent detection means is provided between the low voltage power supply terminal of the bridge connection and the low voltage power supply, and a detection signal output from the overcurrent detection means is inputted to clamp the gate control signal to detect the high voltage. and means for turning off the side transistor.

The semiconductor output circuit of the present invention is configured such that the gate ends of the other transistor pair of the H-type bridge output section are respectively connected to the gate ends of the one transistor via an inverter.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a circuit diagram of an embodiment of the present invention.

The semiconductor output circuit has an overcurrent detection section 15 added between the common source point 8 and the ground terminal 9 of the conventional H-type bridge output section 10 shown in FIG.

The overcurrent detection unit 15 has an overcurrent detection resistor 16 provided between the common source point 8 and the terminal 9, inputs the voltage VR to the base, connects the collector to the gate control terminal 11.13 on the high voltage side, and connects the common emitter to the overcurrent detection resistor 16. It has NPN transistors 5 and 6 which connect the point to the ground terminal 9.

If load RL fails for some reason and output terminal M,
If there is a short circuit between N and N, or if excessive voltage is applied to the power supply terminal 7 and excessive current flows to the load resistor RL or the power supply terminal 9, the detection voltage VR of the overcurrent detection resistor 16 will be 0.7V.
The voltage rises above the current level, current also flows to the base of the NPN transistor, transistor 5.6 turns on, and the gate control signal S on the high voltage side
1 and 83 and lower the voltage of MOS transistor 1 on the high voltage side.
．． 3 is turned off to prevent excessive current flowing through the output load resistor RL.

Note that the resistance value is made sufficiently small in order to prevent loss due to the current detection resistor 16 and to prevent the NPN (Npn) run lister from being turned on under normal conditions.

FIG. 2 is a circuit diagram of a second embodiment of the invention.

The collector of the NPN) run lister 5.6 of the overcurrent detection unit 15 described in the first embodiment and the low voltage side transistor 24
One 18° inverter is added between the gates.

In this embodiment, when an excessive current flows through the H-type bridge, both of the pair of MOS transistors 1.3 on the high-voltage power supply terminal 7 side of the two MOS transistor pairs forming the H-type bridge output section 10a are turned off. At the same time, the pair of MOS Landestors 2 and 4 on the ground terminal 8 side is turned on to form a closed loop with the load RL and the transistor 2.4.

This has the effect of having a function of applying a brake to the driving motor to stop it when excess current is detected.

In the above embodiment, N-channel M is used as a MOS) run lister.
Although NPN transistors were used as O5FETs and bipolar transistors5, the same effect can be obtained by combining other transistors as long as the polarity is selected.

〔Effect of the invention〕

As explained above, in the present invention, in a semiconductor output circuit having an H-type bridge output section consisting of a pair of two MOS transistors, an H-type bridge is configured by detecting an excessive load current of the circuit and clamping the control signal. Some MOS
) By turning off the run lister, it is possible to prevent damage to the MOS transistor or melting down of the lead wires connecting the lead frame of the chip.

Further, in the case of a motor load, some MOS transistors are turned on, forming a closed circuit including the motor, and braking the motor.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a first embodiment of the present invention, FIG. 2 is a circuit diagram of a second embodiment of the present invention, and FIG. 3 is a circuit diagram of an example of a conventional semiconductor output circuit. 1 to 4...n channel MO3) run lister, 5°6.
・・NPN) run lister, 7・High voltage power supply terminal, 8・
...Common source point, 9...Ground terminal, 10...H-type bridge, 11-14...Control signal terminal, 15...
Overcurrent detection section, 16...Current detection resistor, 17.18...
・Inverter.

Claims (1)

[Claims] An H-type bridge output section in which a gate control signal is input to each gate end of one transistor pair of a bridge configuration having one or two MOS transistor pairs, and a load is connected between a pair of bridge output terminals. In the semiconductor output circuit, an overcurrent detection means is provided between the low voltage power supply terminal of the bridge connection and the low voltage power supply, and a detection signal output from the overcurrent detection means is inputted to clamp the gate control signal to detect the high voltage. 1. A semiconductor output circuit comprising means for turning off a side transistor. 2. The semiconductor output circuit according to claim 1, wherein the gate ends of the other transistor pair of the H-type bridge output section are respectively connected to the gate ends of the one transistor via an inverter. .