US 5,309,347 AGranted

H-bridge circuit with protection against crossover conduction

AssigneesSGS-Thomson Microelectronics S.A., Marelli Autronica S.p.A.

InventorsAlberto Poma, Vanni Poletto, Marco Morelli

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Abstract

An H-bridge circuit which includes four power transistors (an npn pull-down and a pnp pull-up for each of the output terminals). Two control circuits are connected to drive these transistors in a complementary crossover configuration, so that each control circuit can turn on the pull-up transistor on one side of the load and the pull-down transistor on the opposite side of the load. Each of the power transistors is paralleled (base-to-base) by a smaller transistor which provides a scaled current output (proportional to that of the corresponding power transistor) to the opposite control circuit. The control circuit includes static current-thresholding disable logic, which prevents turn-on until the currents through the opposite power devices have declined to threshold levels. Thus, as long as either control circuit is driving one of the pull-up transistors into in the on-state, the other control circuit will not be able to turn on the pull-down transistor which is in series with the active pull-up transistor. This efficiently prevents any condition of unlimited crowbar current, without adding any excess delay or causing any high-impedance condition at the output.

Claims35

Dependent claims

An H-bridge amplifier circuit, comprising:

first and second output terminals;
a first pull-down power transistor connected between said first output terminal and a first power supply connection, and a first pull-up power transistor connected between said first output terminal and a second power supply connection which is more positive than said first power supply connection;
and a second pull-down power transistor connected between said second output terminal and said first power supply connection, and a second pull-up power transistor connected between said second output terminal and said second power supply connection;
and
a first control circuit connected to control said first pull-up power transistor and said second pull-down power transistor, and a second control circuit connected to control said second pull-up power transistor and said first pull-down power transistor;
said first and second control circuits each having at least one respective enable/disable input;
a first auxiliary pull-down transistor connected, in parallel with said first power pull-down transistor, to provide said first control circuit with a respective monitoring current which is proportional to the current output of said first pull-down transistor;
and
a first auxiliary pull-up transistor connected, in parallel with said first power pull-up transistor, to provide said second control circuit with a respective monitoring current which is proportional to the current output of said first pull-down transistor;
and
a second auxiliary pull-up transistor connected, in parallel with said second power pull-up transistor, to provide said first control circuit with a respective monitoring current which is proportional to the current output of said first pull-down transistor;
and
a second auxiliary pull-down transistor connected, in parallel with said second power pull-down transistor, to provide said second control circuit with a respective monitoring current which is proportional to the current output of said first pull-down transistor;
wherein said first and second control circuit each contain current-thresholding disable logic connected to receive at least two said monitoring currents from at least one of said auxiliary transistors, and to disable activation of power transistors by said control circuit if either said monitoring current is greater than a predetermined respective magnitude.

11 more elements

A circuit, comprising:

first and second output terminals for connection to the terminals of a load,
first and second pairs of electronic power switches which are connected between said output terminals and the two poles of a direct-current voltage supply so as to form an H-shaped structure with the load, and driver circuit connected to selectively make said the electronic power switches of said first pair or of said second pair conductive in order to cause a current to flow through the load in one direction or the other, respectively, and for preventing said electronic power switches which are connected between the same output terminal and the two poles of the voltage supply from conducting simultaneously;
said driver circuit also including:
at least one first and one second auxiliary electronic switch, which are connected respectively to an electronic power switch of said first pair and to an electronic power switch of said second pair in a relation such that, in operation, the current flowing through each auxiliary electronic switch depends on the current flowing through the associated electronic power switch;
and wherein comparator and enabling circuitry are connected to said auxiliary electronic switches for supplying a signal to enable current to be conducted through one of said pairs of electronic power switches only when the current flowing through said auxiliary switch associated with the other pair has fallen below a predetermined value.

2 more elements

An integrated circuit H-bridge amplifier, comprising:

first and second output terminals;
a first pull-down power transistor connected between said first output terminal and a first power supply connection, and a first pull-up power transistor connected between said first output terminal and a second power supply connection which is more positive than said first power supply connection;
and a second pull-down power transistor connected between said second output terminal and said first power supply connection, and a second pull-up power transistor connected between said second output terminal and said second power supply connection;
and
a first control circuit connected to control said first pull-up power transistor and said second pull-down power transistor, and a second control circuit connected to control said second pull-up power transistor and said first pull-down power transistor;
said first and second control circuits each having at least one respective enable/disable input;
at least two different transistors selected from the group consisting of:
1) a first auxiliary pull-down transistor connected, in parallel with said first power pull-down transistor, to provide said first control circuit with a monitoring current which is proportional to and smaller than the current output of said first pull-down transistor;
and
2) a first auxiliary pull-up transistor connected, in parallel with said first power pull-up transistor, to provide said second control circuit with a monitoring current which is proportional to and smaller than the current output of said first pull-down transistor;
and
3) a second auxiliary pull-up transistor connected, in parallel with said second power pull-up transistor, to provide said first control circuit with a monitoring current which is proportional to and smaller than the current output of said first pull-down transistor;
and
4) a second auxiliary pull-down transistor connected, in parallel with said second power pull-down transistor, to provide said second control circuit with a monitoring current which is proportional to and smaller than the current output of said first pull-down transistor;
wherein said first and second control circuit each contain current-thresholding disable logic connected to receive at least one said monitoring current from at least one of said auxiliary transistors, and to disable activation of power transistors by said control circuit if said monitoring current is greater than a predetermined respective magnitude.

12 more elements

An integrated circuit H-bridge amplifier, comprising:

first and second output terminals;
a first pull-down power device connected between said first output terminal and a first power supply connection, and a first pull-up power device connected between said first output terminal and a second power supply connection which is more positive than said first power supply connection;
and a second pull-down power device connected between said second output terminal and said first power supply connection, and a second pull-up power device connected between said second output terminal and said second power supply connection;
and
a first control circuit connected to control said first pull-up power device and said second pull-down power device, and a second control circuit connected to control said second pull-up power device and said first pull-down power device;
said first and second control circuits each having at least one respective enable/disable input;
at least two different devices selected from the group consisting of:
1) a first auxiliary pull-down device connected to said first power supply connection and connected to be controlled by said second control circuit in parallel with said first power pull-down device and connected to supply an enable signal to said first control circuit accordingly;
and
2) a first auxiliary pull-up device connected to said second power supply connection and connected to be controlled by said first control circuit in parallel with said first power pull-up device and connected to supply an enable signal to said second control circuit accordingly;
and
3) a second auxiliary pull-up device connected to said second power supply connection and connected to be controlled by said second control circuit in parallel with said second power pull-up device and connected to supply an enable signal to said first control circuit accordingly;
and
4) a second auxiliary pull-down device connected to said first power supply connection and connected to be controlled by said first control circuit in parallel with said second power pull-down device and connected to supply an enable signal to said second control circuit accordingly.

11 more elements

An integrated circuit H-bridge amplifier, comprising:

first and second output terminals;
a first pull-down power transistor connected between said first output terminal and a first power supply connection, and a first pull-up power transistor connected between said first output terminal and a second power supply connection which is more positive than said first power supply connection;
and a second pull-down power transistor connected between said second output terminal and said first power supply connection, and a second pull-up power transistor connected between said second output terminal and said second power supply connection;
and
a first control circuit connected to control said first pull-up power transistor and said second pull-down power transistor, and a second control circuit connected to control said second pull-up power transistor and said first pull-down power transistor;
said first and second control circuits each having at least one respective enable/disable input;
at least two different transistors selected from the group consisting of:
1) a first auxiliary pull-down transistor connected to said first power supply connection and connected to be controlled by said second control circuit in parallel with said first power pull-down transistor and connected to supply an enable signal to said first control circuit accordingly;
and
2) a first auxiliary pull-up transistor connected to said second power supply connection and connected to be controlled by said first control circuit in parallel with said first power pull-up transistor and connected to supply an enable signal to said second control circuit accordingly;
and
3) a second auxiliary pull-up transistor connected to said second power supply connection and connected to be controlled by said second control circuit in parallel with said second power pull-up transistor and connected to supply an enable signal to said first control circuit accordingly;
and
4) a second auxiliary pull-down transistor connected to said first power supply connection and connected to be controlled by said first control circuit in parallel with said second power pull-down transistor and connected to supply an enable signal to said second control circuit accordingly.

11 more elements

Dependencies are inferred from the claim text.