EP0345679A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
A power supply fault protection circuit
Assignee: RCA Licensing Corp
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Filing: 1989-06-03
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Granted: —
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Expires: 2009-06-03
Abstract
Abstract A MOSFET power switch (Q₁) in a DC-to-DC converter of a television apparatus has a drain electrode (D) that is coupled via a primary winding (T 1A ) of a chopper transformer (T₁) to an input supply voltage (B+). A first signal (V G ) at a given frequency causes, during normal operation, alternate conduction and nonconduction in the transistor (Q₁). A second signal (V Q2 ) is generated that is proportional to the voltage developed across the internal "on" resistance of the transistor (Q₁) when the transistor is conductive. The second signal (V Q2 ) is clamped when the MOSFET (Q₁) is nonconductive. The second signal (V Q2 ) is coupled via a current sensing arrangement (51) to the transistor gate (G). The second signal (V Q2 ) prevents the transistor (Q₁) from further conducting when the amplitude of the second signal (V Q2 ) exceeds a predetermined value that corresponds with a predetermined limiting threshold level of current (i₁) in the transistor (Q₁).
Inventors
- 👤 Felix Aschwanden
- 👤 Peter Eduard Haferl
- 👤 Theodor Ernst Bart
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-01 11:53
CPC Classifications
H; H04; H04N; H04N5/00; H04N5/63; H02; H02H; H02H7/00; H02H7/10; H02H7/12; H02H7/122; H02H7/1213
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
456 words
A fault detection and protection apparatus in a switching power supply, comprising: a source of an input supply voltage; a first switching power transistor having first and second main current conducting electrodes and a control electrode; a source of a first control signal at a given frequency that is coupled to said control electrode of said first switching power transistor for causing, during normal operation, said first switching transistor to operate at a switching frequency determined in accordance with said given frequency; a utilization circuit including an impedance coupled to said input supply voltage and to said first main current conducting electrode for developing an output supply voltage in said utilization circuit, characterized in that said impedance (T 1a ) forming a current path to a switched main current (i₁) that flows in said first switching power transistor (Q₁) to develop a first current sensing signal (V Q1 ) at a frequency determined in accordance with said given frequency, and that is developed between said first (D) and second (S) main current conducting electrodes of said first switching power transistor (Q1) when said first switching power transistor is conductive, said first current sensing signal (V Q1 ) being indicative of a level of said main current when said first switching power transistor (Q₁) is conductive; first means (Q₂) responsive to said first control signal (V G ) and to said first current sensing signal (V Q1 ) and having an input terminal (R₁) that is coupled to said first main current conducting electrode (D) for generating at an output terminal (Q 2a ) a first portion of a second current sensing signal (V Q2 ) that is indicative of said level of said main current (i₁) when said first switching power transistor (Q₁) is at a conductive state, and for decoupling said output terminal (Q 2a ) from said power transistor (Q₁) when said first switching power transistor (Q₁) is at a nonconductive state to prevent a voltage (V Q1 ) that is developed at said first main current conducting electrode (D) of said first switching power transistor (Q₁) when said power transistor is nonconductive from having a substantial contribution to an amplitude of said second current sensing signal (V Q2 ); and second means (51) responsive to said second current sensing signal (V Q2 ) for generating a second control signal (INHIBIT), when a magnitude of said first portion of said second current sensing signal (V Q2 ) is outside a normal operation range indicating an occurrence of a fault condition in said power supply, said second control signal (INHIBlT) being coupled to said control electrode (G) of said first switching power transistor (Q₁) for preventing said first switching power transistor (Q₁) from further conducting.
Claim 2
Dependent Claim
456 words
A fault detection and protection apparatus in a switching power supply, comprising: a source of an input supply voltage; a first switching power transistor having first and second main current conducting electrodes and a control electrode; a source of a first control signal at a given frequency that is coupled to said control electrode of said first switching power transistor for causing, during normal operation, said first switching transistor to operate at a switching frequency determined in accordance with said given frequency; a utilization circuit including an impedance coupled to said input supply voltage and to said first main current conducting electrode for developing an output supply voltage in said utilization circuit, characterized in that said impedance (T 1a ) forming a current path to a switched main current (i₁) that flows in said first switching power transistor (Q₁) to develop a first current sensing signal (V Q1 ) at a frequency determined in accordance with said given frequency, and that is developed between said first (D) and second (S) main current conducting electrodes of said first switching power transistor (Q1) when said first switching power transistor is conductive, said first current sensing signal (V Q1 ) being indicative of a level of said main current when said first switching power transistor (Q₁) is conductive; first means (Q₂) responsive to said first control signal (V G ) and to said first current sensing signal (V Q1 ) and having an input terminal (R₁) that is coupled to said first main current conducting electrode (D) for generating at an output terminal (Q 2a ) a first portion of a second current sensing signal (V Q2 ) that is indicative of said level of said main current (i₁) when said first switching power transistor (Q₁) is at a conductive state, and for decoupling said output terminal (Q 2a ) from said power transistor (Q₁) when said first switching power transistor (Q₁) is at a nonconductive state to prevent a voltage (V Q1 ) that is developed at said first main current conducting electrode (D) of said first switching power transistor (Q₁) when said power transistor is nonconductive from having a substantial contribution to an amplitude of said second current sensing signal (V Q2 ); and second means (51) responsive to said second current sensing signal (V Q2 ) for generating a second control signal (INHIBIT), when a magnitude of said first portion of said second current sensing signal (V Q2 ) is outside a normal operation range indicating an occurrence of a fault condition in said power supply, said second control signal (INHIBlT) being coupled to said control electrode (G) of said first switching power transistor (Q₁) for preventing said first switching power transistor (Q₁) from further conducting.
Claim 3
Dependent Claim
106 words
An apparatus according to Claim 1 characterized in that said first means comprises a second switching transistor (Q₂) having a control electrode (gate) that is coupled to said first control signal (V G ) and a main current conducting electrode that is coupled via a second impedance (R₁) to said first main current conducting electrode (D) of said first switching power transistor (Q₁) for developing said second current sensing signal (V Q2 ) at said main current conducting electrode of said second switching transistor (Q₂) such that when said first switching power transistor (Q₁) is conductive said second switching transistor (Q₂) is nonconductive, and vice versa.
Claim 4
Dependent Claim
79 words
An apparatus according to Claim 1 characterized in that said first means (Q₂) operates at a frequency that is related to that of said first control signal (V G ) and wherein, when said first switching power transistor (Q₁) is nonconductive, said first means (Q₂) causes said second current sensing signal (V Q2 ) to be at a predetermined constant level that is substantially lower than of said first portion of said second current sensing signal (V Q2 ).
Claim 5
Dependent Claim
147 words
An apparatus according to Claim 1 characterized in that said first means comprises a diode (D₂′) having a first terminal (cathode) that is coupled to said first main current conducting electrode (D) of said first switching power transistor (Q₁) for developing said second current sensing signal (V D2′ ) at a second terminal (anode) of said diode (D₂′) such that, when said first switching power transistor (Q₁′) is conductive, said diode (D₂′) is forward biased, and when said first switching power transistor (Q i ) is nonconductive, said first current sensing signal (V Q1 ′) that is developed at said first main current conducting electrode (D) of said first switching power transistor (Q₁′) back biases said diode (D 2 ′) to decouple said first main current conducting electrode (D) of said first switching power transistor (Q₁′) from said second terminal (anode) of said diode (D 2 ′).
Claim 6
Dependent Claim
198 words
An apparatus according to Claim 1 characterized in that said impedance comprises, a first transformer winding (T 10a ) having a first terminal (90) that is coupled to said first main current conducting electrode (D) of said first switching power transistor (Q₁₀), a second switching power transistor (Q₂₀) having a first main current conducting electrode (D) that is coupled to a second terminal (91) of said first transformer winding (T 10a ) that is remote from said first switching power transistor (Q₁₀) for conducting a second switching current in said second switching power transistor (Q₂₀) and having a control electrode that is responsive to a control signal (V 2b ) at a frequency that is related to that of said first control signal (V 2a ) such that said first (Q₁₀) and second (Q₂₀) switching power transistors operate in a push-pull manner, and wherein said second means (51) is coupled to said first main current conducting electrodes (D) of said first (Q₁₀) and second (Q₂₀) switching power transistors for generating said second current sensing signal (V SUM ) that is indicative of an overcurrent condition in either one of said first (Q₁₀) and second (Q₂₀) switching power transistors.
Claim 7
Dependent Claim
137 words
An apparatus according to Claim 5 characterized in that said second means comprises first (D₂₀) and second (D₃₀) diodes, said first diode (D₂₀) having a first terminal (cathode) that is coupled to said first main current conducting electrode (D) of said first switching power transistor (Q₁₀) and said second diode (D₃₀) having a first terminal (cathode) that is coupled to said first main current conducting electrode (D) of said second switching power transistor (Q₂₀) and combining means (R₆, R₇) coupled to said diodes (D₂₀,D₃₀) for developing said second current sensing signal (V SUM ) in accordance with a signal (V S10 ) that is developed at a second terminal (anode) of said first diode (D₂₀) and in accordance with a signal (V S20 ) that is developed at a second terminal (anode) of said second diode (D₃₀).
Claim 8
Dependent Claim
95 words
An apparatus according to Claim 5 characterized by a rectifier arrangement (D₄,D₅) coupled to said first winding (T 10a ) for generating a first DC output voltage (V DG ) in a capacitor (C₁₀) and a switching third means (D₃₀) responsive to a signal that is developed at a second winding (T 10b ) of said transformer (T₁₀) for coupling said first DC output voltage to an output terminal (77) of said third means (Q₃₀) during normal operation and for fast decoupling said output terminal (77) from said capacitor (C₁₀) when a fault condition occurs.
Claim 9
Dependent Claim
79 words
An apparatus according to Claim 1 characterized by a delay means (U 3b ) responsive to said second current sensing signal (V SUM ) for generating a signal (V 3BOUT ) that enables resumption of the switching operation in said first switching power transistor (Q₁₀) only after a period having at least a predetermined length has elapsed following the occurrence of said second control signal (INHIBIT) that is sufficient to prevent harm to said first switching power transistor (Q₁₀).
Claim 10
Dependent Claim
406 words
A fault detection and protection arrangement of a power supply apparatus, comprising: a source of an input supply voltage; a first switching power transistor having first and second main current conducting electrodes and a control electrode; a source of a first signal at a given frequency coupled to said control electrode of said first switching power transistor for causing, during normal operation, said first switching transistor to operate at a switching frequency determined in accordance with said given frequency; a utilization circuit including an impedance coupled to said input supply voltage and to said first main current conducting electrode for developing an output supply voltage in said utilization circuit, characterized in that said impedance forming a current path to a switched main current (i₁) that flows in said first switching power transistor (Q₁) for developing a second signal (V Q1 ) at a frequency that corresponds with that of said first control signal (V G ) and that is developed between said first (D) and second (S) main current conducting electrodes of said first switching power transistor (Q₁), said second signal (V Q1 ) being indicative of a level of said switched main current (i₁); a second impedance (R₁) having a first terminal that is coupled to said first (D) main current conducting electrode of said first switching power transistor (Q₁); a second switching transistor (Q₂) having a control electrode (G) that is coupled to said first signal (V G ) and a main current conducting electrode (Q 2a ) that is coupled to a second terminal of said second impedance (R₁) for developing a third signal (V Q2 ), at said main current conducting electrode (Q 2a ) of said second switching transistor (Q₂) when said first switching power transistor (Q₁) is conductive, that is indicative of an amplitude of said switched main current, and when said first switching power transistor (Q₁) is nonconductive, said second switching transistor (Q₂) causes said third signal (V Q2 ) to be substantially smaller in value than when said first switching power transistor (Q₁) is conductive; and means (51) responsive to said third signal (V Q2 ) for generating a control signal (INHIBIT) that is coupled to said control electrode (G) of said first switching power transistor (Q₁), said control signal (INHIBIT) causing a reduction in said current (i₁) that flows in said first switching power transistor (Q₁) when said third signal (V Q2 ) exceeds a predetermined magnitude.
Claim 11
Dependent Claim
406 words
A fault detection and protection arrangement of a power supply apparatus, comprising: a source of an input supply voltage; a first switching power transistor having first and second main current conducting electrodes and a control electrode; a source of a first signal at a given frequency coupled to said control electrode of said first switching power transistor for causing, during normal operation, said first switching transistor to operate at a switching frequency determined in accordance with said given frequency; a utilization circuit including an impedance coupled to said input supply voltage and to said first main current conducting electrode for developing an output supply voltage in said utilization circuit, characterized in that said impedance forming a current path to a switched main current (i₁) that flows in said first switching power transistor (Q₁) for developing a second signal (V Q1 ) at a frequency that corresponds with that of said first control signal (V G ) and that is developed between said first (D) and second (S) main current conducting electrodes of said first switching power transistor (Q₁), said second signal (V Q1 ) being indicative of a level of said switched main current (i₁); a second impedance (R₁) having a first terminal that is coupled to said first (D) main current conducting electrode of said first switching power transistor (Q₁); a second switching transistor (Q₂) having a control electrode (G) that is coupled to said first signal (V G ) and a main current conducting electrode (Q 2a ) that is coupled to a second terminal of said second impedance (R₁) for developing a third signal (V Q2 ), at said main current conducting electrode (Q 2a ) of said second switching transistor (Q₂) when said first switching power transistor (Q₁) is conductive, that is indicative of an amplitude of said switched main current, and when said first switching power transistor (Q₁) is nonconductive, said second switching transistor (Q₂) causes said third signal (V Q2 ) to be substantially smaller in value than when said first switching power transistor (Q₁) is conductive; and means (51) responsive to said third signal (V Q2 ) for generating a control signal (INHIBIT) that is coupled to said control electrode (G) of said first switching power transistor (Q₁), said control signal (INHIBIT) causing a reduction in said current (i₁) that flows in said first switching power transistor (Q₁) when said third signal (V Q2 ) exceeds a predetermined magnitude.
Claim 12
Dependent Claim
368 words
A fault detection and protection apparatus in a switching power supply, comprising: a source of an input supply voltage; a first switching power transistor having a control electrode and first and second main current conducting electrodes for conducting a first switching current; a source of a first signal at a given frequency that is coupled to said control electrode of said first switching power transistor for causing, during normal operation, said first switching transistor to operate at a switching frequency that is determined in accordance with said given frequency; a first transformer winding having a first terminal that is coupled to said first main current conducting electrode of said first switching power transistor; a second switching power transistor having a first main current conducting electrode that is coupled to a second terminal of said first transformer winding that is remote from said first switching power transistor for conducting a second switching current in said second switching power transistor and having a control electrode that is responsive to a signal at a frequency that is related to that of said first signal such that said first and second switching power transistors operate in a push-pull manner; characterized by means (D₂₀,D₃₀) coupled to said first main current conducting electrodes of said first (Q₁₀) and second (Q₂₀) switching power transistors for generating a third signal (V SUM ) that is proportional, during first and second portions of a given period of said first signal (V 2a ), to values of internal impedances of said first (Q₁₀) and second (Q₂₀) switching power transistors, respectively, and that is proportional, during said first and second portions, to said first (i₁₀) and second switching (i₂₀) currents that flow therein, respectively; and means (U 3A ) responsive to said third signal (V SUM ) for generating a control signal (INHBIIT) when a magnitude of either one of said first (i₁₀) and second (i₂₀) switching currents is outside a normal operation range, that is indicative of an occurrence of a fault condition in said power supply, said control signal (INHIBIT) being coupled to said control electrode of at least one of said first (Q₁₀) and second (Q₂₀) switching power transistors for providing protection against said fault condition.
Claim 13
Dependent Claim
368 words
A fault detection and protection apparatus in a switching power supply, comprising: a source of an input supply voltage; a first switching power transistor having a control electrode and first and second main current conducting electrodes for conducting a first switching current; a source of a first signal at a given frequency that is coupled to said control electrode of said first switching power transistor for causing, during normal operation, said first switching transistor to operate at a switching frequency that is determined in accordance with said given frequency; a first transformer winding having a first terminal that is coupled to said first main current conducting electrode of said first switching power transistor; a second switching power transistor having a first main current conducting electrode that is coupled to a second terminal of said first transformer winding that is remote from said first switching power transistor for conducting a second switching current in said second switching power transistor and having a control electrode that is responsive to a signal at a frequency that is related to that of said first signal such that said first and second switching power transistors operate in a push-pull manner; characterized by means (D₂₀,D₃₀) coupled to said first main current conducting electrodes of said first (Q₁₀) and second (Q₂₀) switching power transistors for generating a third signal (V SUM ) that is proportional, during first and second portions of a given period of said first signal (V 2a ), to values of internal impedances of said first (Q₁₀) and second (Q₂₀) switching power transistors, respectively, and that is proportional, during said first and second portions, to said first (i₁₀) and second switching (i₂₀) currents that flow therein, respectively; and means (U 3A ) responsive to said third signal (V SUM ) for generating a control signal (INHBIIT) when a magnitude of either one of said first (i₁₀) and second (i₂₀) switching currents is outside a normal operation range, that is indicative of an occurrence of a fault condition in said power supply, said control signal (INHIBIT) being coupled to said control electrode of at least one of said first (Q₁₀) and second (Q₂₀) switching power transistors for providing protection against said fault condition.
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