EP0256569A1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Supply circuit for supplying a smoothed direct current to a load impedance
Assignee: Koninklijke Philips NV
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Filing: 1987-06-25
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Granted: —
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Expires: 2007-06-25
Abstract
Abstract A supply circuit comprising an FET as a series element in series with the load resistance. The supply circuit is fed from the mains network via a rectifier 54 and a smoother 52, causing a ripple voltage to be present on the input terminals 2-1 and 2-2. The direct voltage component of the input voltage is present across load resistance 60, the alternating voltage component of this voltage being present across transistor 10. With known supply voltage circuits the voltage drop across the series element is selected to be equal to the maximum peak-to-peak value of the alternating voltage component, causing unnecessary dissipation to be developed at a minor ripple amplitude. This will cause fast ageing of the series element. The supply circuit in accordance with the invention comprises a comparator 42 comparing the voltage across transistor 10 to a threshold voltage. Comparator 42 controls the charge on the filter capacitors 30 and 32. Consequently, the overall voltage across transistor 10 will never exceed the sum of the threshold voltage and the peak-to-peak voltage of the voltage component of the input voltage.
Inventors
- 👤 Gerrit Rademaker
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 23:22
CPC Classifications
H; H02; H02M; H02M7/00; H02M7/02; H02M7/04; H02M7/12; H02M7/21; H02M7/217; H02M7/2176
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
256 words
A supply circuit for supplying a smoothed direct current to a load impedance, comprising : - input terminals for receiving a voltage consisting of a direct voltage component and a periodic alternating voltage component superposed thereon having a specified ripple period, - output terminals for connecting the load impedance, - a series element controllable via a control input and comprising a main current path connected in series with the load impedance, - a low-pass filter having an output on which there is a voltage whose direct voltage component is determined by at least one filter capacitor, - and a differential amplifier having an output connected to the control input of the series element, having a first input to which is supplied a voltage proportional to the voltage across the load impedance, and having a second input connected to the output of the low pass filter, characterized in that the supply circuit further comprises: - discharge means for discharging the current from the filter capacitor during at least part of the ripple period, - supply means for providing supply current to the filter capacitor, which supply current is large with respect to the discharge current, - a threshold voltage circuit for producing a threshold voltage, - and a comparator to be supplied with the threshold voltage, having an input to which the voltage over the series element is applied and having an output connected to the supply means, for making the supply current flow if the voltage across the series element is smaller than the threshold voltage.
Claim 2
Dependent Claim
256 words
A supply circuit for supplying a smoothed direct current to a load impedance, comprising : - input terminals for receiving a voltage consisting of a direct voltage component and a periodic alternating voltage component superposed thereon having a specified ripple period, - output terminals for connecting the load impedance, - a series element controllable via a control input and comprising a main current path connected in series with the load impedance, - a low-pass filter having an output on which there is a voltage whose direct voltage component is determined by at least one filter capacitor, - and a differential amplifier having an output connected to the control input of the series element, having a first input to which is supplied a voltage proportional to the voltage across the load impedance, and having a second input connected to the output of the low pass filter, characterized in that the supply circuit further comprises: - discharge means for discharging the current from the filter capacitor during at least part of the ripple period, - supply means for providing supply current to the filter capacitor, which supply current is large with respect to the discharge current, - a threshold voltage circuit for producing a threshold voltage, - and a comparator to be supplied with the threshold voltage, having an input to which the voltage over the series element is applied and having an output connected to the supply means, for making the supply current flow if the voltage across the series element is smaller than the threshold voltage.
Claim 3
Dependent Claim
61 words
A supply circuit as claimed in claim 1, characterized in that both the threshold voltage circuit and the comparator are together formed by a transistor whose base-emitter junction is connected in parallel with the main current path of the series element, the forward voltage of the base-emitter junction forming the threshold voltage and the collector forming the output of the comparator.
Claim 4
Dependent Claim
59 words
A supply circuit as claimed in claim 1 or 2, characterized in that the supply means are formed by a series arrangement of a resistance and a diode, the series arrangement being connected between one of the input terminals and the filter capacitor, and the junction point of the resistance and the diode being connected to the comparator output.
Claim 5
Dependent Claim
25 words
A supply circuit as claimed in any one of the preceding claims, characterized in that the series element is formed by a field effect transistor.
Claim 6
Dependent Claim
66 words
A supply circuit as claimed in any one of the preceding claims, characterized in that the low pass filter is formed by the parallel circuit of a first filter capacitor with a series arrangement of a resistance and a second filter capacitor, the connections of the first filter capacitor forming the input and the connections of the second filter capacitor forming the output of the filter.
References Cited (Backward Citations)
WO1983001694A1
Cited
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