EP0154062A1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Power switching circuit
Assignee: International Business Machines Corp
•
Filing: 1984-02-29
•
Granted: —
•
Expires: 2004-02-29
Abstract
Abstract @ A power switching circuit for switching power repetitively to a load at a relatively low frequency employs a power switching device (14) which is driven across an isolating transformer interface (60). The drive signals are high frequency pulse signals which are modulated with the low frequency switching information, the modulations being detected in the secondary circuit (62) of the transformer. Such an arrangement affords isolated driving with fast switching edges and requires only a small transformer. Power for the detection circuit is derived by rectification (120-124) of the high frequency signals induced in the transformer secondary.
Inventors
- 👤 Robert Duncan Commander
- 👤 Brian Peter Fenton
- 👤 John Gilbert Ramage
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 15:19
CPC Classifications
H; H03; H03K; H03K17/00; H03K17/51; H03K17/56; H03K17/687; H03K17/689; H03K17/691; H02; H02M; H02M7/00; H02M7/42; H02M7/44; H02M7/48; H02M7/53; H02M7/537; H02M7/5387; H03K2217/00; H03K2217/0045
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
189 words
A power switching circuit for switching power repetitively to a load, comprising a power switching device (14) responsive to a drive signal at a control input thereof to connect a power supply (17, 18) to a load (10) and a drive circuit (24, 60, 62-89) for providing a repetitive drive signal to the control input of the power switching device (14) within a predetermined frequency range, the drive circuit comprising a transformer (60) and a primary circuit (64-89) including a primary winding (75) of the transformer (60), a source (70, 149) of periodic signals of frequency above said predetermined frequency range, modulating means (64-73, 76-89) for producing from said periodic signals a signal modulated at a frequency within said predetermined range and means for applying the modulated signal to the primary winding (75), the drive circuit further comprising a secondary circuit (24) including a secondary winding (62) of the transformer (60), in which a correspondingly modulated signal is induced, and detection means (125-132) for detecting the modulations and producing in response thereto such a repetitive drive signal for application to the control input of the power switching device (14).
Claim 2
Dependent Claim
189 words
A power switching circuit for switching power repetitively to a load, comprising a power switching device (14) responsive to a drive signal at a control input thereof to connect a power supply (17, 18) to a load (10) and a drive circuit (24, 60, 62-89) for providing a repetitive drive signal to the control input of the power switching device (14) within a predetermined frequency range, the drive circuit comprising a transformer (60) and a primary circuit (64-89) including a primary winding (75) of the transformer (60), a source (70, 149) of periodic signals of frequency above said predetermined frequency range, modulating means (64-73, 76-89) for producing from said periodic signals a signal modulated at a frequency within said predetermined range and means for applying the modulated signal to the primary winding (75), the drive circuit further comprising a secondary circuit (24) including a secondary winding (62) of the transformer (60), in which a correspondingly modulated signal is induced, and detection means (125-132) for detecting the modulations and producing in response thereto such a repetitive drive signal for application to the control input of the power switching device (14).
Claim 3
Dependent Claim
40 words
A circuit as claimed in claim 1 in which the secondary circuit (24) includes rectifying means (120-123) for rectifying the modulated secondary winding signal, the rectified signal being connected to provide an independent power supply (124) to the detecting means.
Claim 4
Dependent Claim
46 words
A circuit as claimed in claim 1 in which the secondary circuit (24) includes inhibiting means (131, 132) for inhibiting the detection means (125-132) from producing the repetitive drive signal if the independent power supply voltage from the rectifying means (120-123) is below a predetermined minimum.
Claim 5
Dependent Claim
57 words
A power switching circuit as claimed in any preceding claim in which the modulated signal from the modulating means (64-73, 76-89) consists of periodic waveform portions (100, 101; 102, 103), at a frequency above said predetermined range, whose cyclic voltage excursions are asymmetric about a mean level, the modulation being effected by inversion of said waveform portions.
Claim 6
Dependent Claim
110 words
A power switching circuit as claimed in claim 4 in which the source of periodic signals is an oscillator (149) capable of producing a train of pulses (CLK) and the modulating means (64-73, 76-89) comprises gating logic (64-73, 82, 83) responsive to pulses from the oscillator (153) and also to at least one switching logic signal to produce gating signals, and a bridge circuit (76-81, 84-89) responsive to the gating signals from the gating logic to produce modulated signal whose cyclic voltage excursions comprise pulses (100, 102) of one sense, amplitude and duration alternating with pulses (101, 103) of the opposite sense, a lower amplitude and a proportionately increased duration.
Claim 7
Dependent Claim
61 words
A power switching circuit as claimed in claim 4 or claim 5 in which the detection means (125-132) includes amplitude comparison means for comparing the voltage excursions of the modulated signal induced in the secondary circuit with at least one predetermined threshold such that the threshold is exceeded by the induced signal in only one of its inverted and non-inverted states.
Claim 8
Dependent Claim
91 words
A circuit as claimed in claim 6 in which the amplitude comparison means is arranged to compare the voltage excursions of a signal derived from the modulated secondary signal with an upper threshold and a lower threshold, the detecting means (125-132) further including a bistable device which is set to one of its states when the derived signal exceeds the upper threshold and is set to the other of its states when the derived signal falls below the lower threshold, the output of the bistable device constituting the repetitive drive signal.
Claim 9
Dependent Claim
27 words
A circuit as claimed in claim 7 as dependent on claim 2 in which the upper and lower thresholds are referenced to the rectified power supply voltage.
Claim 10
Dependent Claim
54 words
A circuit as claimed in any preceding claim including isolated current sensing means (150-157) for sensing the current flowing through the power switching device (14) across an isolated interface and timer means (160) responsive to the sensed current exceeding a reference value to switch off the power switching device (14) for a predetermined interval.
Claim 11
Dependent Claim
155 words
A circuit as claimed in claim 9 in which the current sensing means comprises a transformer (150) whose secondary circuit includes a secondary winding (153) connected in parallel with a resistor (26) through which the current to be sensed is arranged to flow and a diode (154) arranged in series with the secondary winding (153) to prevent current flow from the power switching device (14) therethrough, the transformer primary circuit including a primary winding (152), a controllable current source (151), responsive to signals from said periodic signal source (149) to apply current pulses to the primary winding (152) whereby the diode (154) is forward biassed so that the voltage across the resistor (26) is applied to the secondary winding (153) to induce a proportionate voltage across the primary winding (152), the primary circuit further including a charge storage device (156) for storing the induced primary voltage which represents the current flowing through the resistor (26).
References Cited (Backward Citations)
FR1253423A
Cited
US3820008A
Cited
US3805094A
Cited
EP0053208A1
Cited
GB2110493A
Cited
GB2117144A
Cited
USPTO Annuity & Maintenance Windows
Maintenance schedule is calculated for granted US utility patents.