Power-supply circuit
First Claim
1. A power-supply circuit for charging a battery, comprising two input terminals for applying an input voltage, a primary winding of a transformer and a first semiconductor switch connected in series between said two input terminals, a series arrangement of a secondary winding of the transformer and a diode with connection terminals for connecting to the battery, first switching means for turning off the first semiconductor switch at a specific value of the current throught the primary winding, and second means for maintaining the average of the voltage across the secondary winding substantially constant in the on-state of the first semiconductor switch.
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Accused Products
Abstract
A flyback converter for charging a battery (6) from different input voltages in which, during the forward interval, a linearly increasing current flows through a transformer primary winding (n1). The current is turned off by a first switch (S1) at a value dictated by switching means (3). During the flyback interval the energy stored in the transformer (Tr) is supplied to the battery as a charging current via the secondary winding (n2) and a diode (D1). The voltage pulses appearing across the secondary winding during the forward intervals are applied to an integrator (11) via a third switch (S3). The integrator intergrates these voltage pulses. If the output voltage of the integrator (11) exceeds a first threshold value a threshold circuit (12) is activated and turns on a second switch (S2) to disable the flyback converter. If subsequently the output voltage of the integrator decreases below a second threshold value, the second switch is turned off again by the threshold circuit so that the flyback converter can be restarted. In this way the average value of the voltage across the secondary winding during the forward intervals is maintained substantially constant. Thus, the flyback converter constitutes a constant-power source, the power supplied to the battery (6) being constant and independent of the input voltage.
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Citations
16 Claims
- 1. A power-supply circuit for charging a battery, comprising two input terminals for applying an input voltage, a primary winding of a transformer and a first semiconductor switch connected in series between said two input terminals, a series arrangement of a secondary winding of the transformer and a diode with connection terminals for connecting to the battery, first switching means for turning off the first semiconductor switch at a specific value of the current throught the primary winding, and second means for maintaining the average of the voltage across the secondary winding substantially constant in the on-state of the first semiconductor switch.
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16. A shaving apparatus comprising a motor which receives power from a power-supply circuit, the power-supply circuit charging a battery and comprising two input terminals for applying an input voltage, a primary winding of a transformer and a first semiconductor switch connected in series between the two input terminals, a series arrangement of a secondary winding of the transformer and a diode with connection terminals for connecting to the battery, first means for turning off the first semiconductor switch at a specific value of the current through the primary winding, and second means for maintaining the average of the voltage across the secondary winding substantially constant in the on-state of the first semiconductor switch.
Specification