Circuit for preventing more than one transistor from conducting

• US 5,777,496 A
• Filed: 03/27/1996
• Issued: 07/07/1998
• Est. Priority Date: 03/27/1996
• Status: Expired due to Fees

• Current Assignee: Schneider Automation Incorporated (Schneider Electric SE)
• Original Assignee: AEG Schneider Automation, INC.
• Inventors: Herman, Jerard I.
• Primary Examiner(s): Callahan, Timothy P.
• Assistant Examiner(s): ZWEIZIG, JEFFERY SHAWN
• Application Number:
  US08/622,744
• Time in Patent Office: 832 Days
• Field of Search: 327/72, 327/73, 327/77, 327/108, 327/109, 327/110, 327/111, 327/112
• US Class Current: 327/108
• CPC Class Codes: H03K 17/08122 in field-effect transistor switches
• CPC Class Codes: H03K 17/6872 using complementary field-effect transistors
• CPC Class Codes: H03K 19/0013 in field effect transistor circuits

Abstract

A totem pole output stage including first and second control modules cross coupled to first and second switching modules for measuring the charge on the gate of a FET contained in the opposing switching module to determine the condition of the opposing switching module, so as to avoid mutual conductivity events without the use of a fixed timing delay while maximizing switching performance.

Claims

1. A switching stage for switching an output signal (OUTPUT) between a first voltage level and a second voltage level in response to an input signal (INPUT), said switching stage comprising:

a. first switch means (SWITCH1), responsive to a first control signal (CTRL1) for switching the output signal (OUTPUT) to the first voltage level and for providing a first switch status signal (SW1), indicative of the conductive state of said first switch means (SWITCH1);

b. second switch means (SWITCH2), responsive to a second control signal (CTRL2) for switching the output signal (OUTPUT) to the second voltage level and for providing a second switch status signal (SW2), indicative of the conductive state of said second switch means (SWITCH2),

c. first control means (CONTROL1), responsive to the input signal (INPUT) and the second switch status signal (SW2), for providing the first control signal (CTRL1); and

d. second control means (CONTROL2), responsive to the input signal (INPUT) and the first switch status signal (SW1) for providing the second control signal (CTRL2),

whereby the output signal (OUTPUT) is switched to either the first or second voltage level in response to the input signal (INPUT), but not both voltage levels simultaneously, and wherein the output signal (OUTPUT) is switched to the first voltage level only when said second switch status signal (SW2) indicates that said second switch means (SWITCH2) is not conducting and wherein the output signal (OUTPUT) is switched to the second voltage level only when said first switch status signal (SW1) indicates that said first switch means (SWITCH1) is not conducting; and

wherein said first switch means (SWITCH1) includes a PFET type field effect transistor (FET) and wherein said second switch means (SWITCH2) includes an NFET type field effect transistor (FET) and wherein said first and second switch means (SWITCH1, SWITCH2) are arranged in series between the first and second voltage levels and the output signal (OUTPUT) signal is connected to the drains of the PFET and NFET type field effect transistors (FETs); and

wherein said first control means (CONTROL) comprises,

first sensing means (SENSE1), responsive to the second switch status signal (SW2) for providing a first enable signal (EN1),

first logic means (LOGIC1), responsive to the input signal (INPUT) and the first enable signal (EN1) signal, for providing a first logic signal (L1), and

first driving means (DRIVER1), responsive to the first logic signal (L1) for providing the first control signal (CTRL1) and wherein said second control means (CONTROL2) comprises,

second sensing means (SENSE2), responsive to the first switch status signal (SW1) for providing a second enable signal (EN2),

second logic means (LOGIC2), responsive to the input signal (INPUT) and the first enable signal (EN1) for providing a second logic signal (L2), and

second driving means (DRIVER1), responsive to the second logic signal (L2) for providing the second control signal (CTRL2); and

wherein said first logic means (LOGIC1) comprises a NAND gate and wherein said second logic means (LOGIC2) comprises a NOR gate; and

wherein said first sensing means (SENSE1) comprises a first operational amplifier (OPAMP1), a first resistor (RP_threshold), a second resistor (RN_sense) and a first transistor (Q_RN) and wherein said second sensing means (SENSE2) comprises a second operational amplifier (OPAMP2), a resistor (RP_sense) and a fourth resistor (RN_threshold) and a second transistor (Q_RP).

2. The switching stage of claim 1, wherein said first resistor (RP_threshold), said first transistor (Q_RN) and said second resistor (RN_sense) are arranged in series between the first and second voltage levels such that said first resistor (RP_threshold) is connected between the first voltage level and the collector of said first transistor (Q_RN) and said second resistor (RN_sense) is connected between the second voltage level and the emitter of said first transistor (Q_RN) and wherein a noninverting input of said first operation amplifier (OPAMP1) is connected to the collector of said first transistor (Q_RN) and the base of said first transistor (Q_RN) is connected to said second switch means (SWITCH2).

3. The switching stage of claim 1, wherein said third resistor (RP_sense), said second transistor (Q_RP) and said fourth resistor (RN_threshold) are arranged in series between said first and second voltage levels such that said third resistor (RP_sense) is connected between the first voltage level and the collector of said second transistor (Q_RP) and said fourth resistor (RN_threshold) is connected between the second voltage level and the emitter of said second transistor (Q_RP) and wherein a noninverting input of OPAMP2 is connected to the emitter of said second transistor (Q_RP) and said first switch means (SWITCH1) comprises a PFET and the base of said second transistor (Q_RP) is connected to the gate of said PFET.

4. The switching stage of claim 1, wherein said first operational amplifier (OPAMP1) comprises a third transistor (Q3) and wherein said second operational amplifier (OPAMP2) comprises a fourth transistor (Q4).

5. A switching stage for switching an output (OUTPUT) signal between first and second voltage levels in response to an input signal (INPUT), said switching stage comprising:

a. first and second switching devices arranged in a totem pole configuration between the first and second voltage levels, said first switching device being responsive to a first control signal (CTRL1), said second switching device being responsive to a second control signal (CTRL2);

b. first control means (CONTROL1) coupled to said first and second switching devices, said first control means (CONTROL1) being responsive to the input signal (INPUT) and a conductive state of said second switching device for providing said first control signal (CTRL1) for selecting either a conductive or nonconductive state of said first switching device; and

c. second control means (CONTROL2) coupled to said first and second switching devices, said second control means (CONTROL2) being responsive to the input signal (INPUT) and the conductive state of said first switching device for providing said second control signal (CTRL2) for selecting either a conductive or nonconductive state of said second switching device,

such that said switching stage operates so as to prevent said first and second switching devices from conducting simultaneously while minimizing the switching time of said switching stage, and

wherein the output signal (OUTPUT) is switched to the first voltage level only when said second switching device is not conducting and wherein the output signal (OUTPUT) is switched to the second voltage level only when said first switching device is not conducting, and

wherein said first and second switching devices provide first and second switch status signals (SW1, SW2) respectively indicative of the conductive state thereof, and wherein said first control means (CONTROL1) comprises,

first sensing means (SENSE1), responsive to the second switch status signal (SW2) for providing a first enable signal (EN1),

first logic means (LOGIC1), responsive to the input signal (INPUT) and the first enable signal (EN1) for providing a first logic signal (L1), and

first driving means (DRIVER1), responsive to the first logic signal (L1) for providing the first control signal (CTRL1), and

wherein said second control means (CONTROL2) comprises,

second sensing means (SENSE2), responsive to the first switch status signal (SW1) for providing a second enable signal (EN2),

second logic means (LOGIC2), responsive to the input signal (INPUT) and the first enable signal (EN1) for providing a second logic signal (L2), and

second driving means (DRIVER1), responsive to the second logic signal (L2) signal for providing the second control signal (CTRL2), and

wherein said first logic means (LOGIC1) comprises a NAND gate and wherein said second logic means (LOGIC2) comprises a NOR gate, and

wherein said first sensing means (SENSE1) comprises a first operational amplifier (OPAMP1), a first resistor (RP_threshold), a second resistor (RN_sense) and a first transistor (Q_RN) and

wherein said second sensing means (SENSE2) comprises a second operational amplifier (OPAMP2), a third resistor (RP_sense) and a fourth resistor (RN_threshold) and a second transistor (Q_RP).

6. The switching stage of claim 5, wherein said first resistor (RP_threshold), said first transistor (Q_RN) and said second resistor (RN_sense) are arranged in series between the first and second voltage levels such that said first resistor (RP_threshold) is connected between the first voltage level and the collector of said first transistor (Q_RN) and said second resistor (RN_sense) is connected between the second voltage level and the emitter of said first transistor (Q_RN) and wherein a noninverting input of said first operational amplifier (OPAMP1) is connected to the collector of said first transistor (Q_RN) and wherein said second switching device includes an NFET and the base of said first transistor (Q_RN) is connected to the gate of said NFET.

7. The switching stage of claim 5, wherein said second resistor (RP_sense), said second transistor (Q_RP) and said first resistor (RN_threshold) are arranged in series between said first and second voltage levels such that said third resistor (RP_sense) is connected between the first voltage level and the collector of said second transistor (Q_RP) and said first resistor (RN_threshold) is connected between the second voltage level and the emitter of said second transistor (Q_RP) and wherein a noninverting input of OPAMP2 is connected to the emitter of said second transistor (Q_RP) and said first switching device comprises a PFET and the base of said second transistor (Q_RP) is connected to the gate of said PFET.

8. The switching stage of claim 5, wherein said first operational amplifier (OPAMP1) comprises a third transistor (Q3) and wherein said second operational amplifier (OPAMP2) comprises a fourth transistor (Q4).