U.S. Philips Corporation

Geert J Bosscha

Schelte Heeringa

Robert H Munnig Schmidt

Andries C Pasma

Robert H Munning Schmidt

A flyback converter including a first (6) and a second (8) switching transistor, a first (10) and a second (12) rectifier diode, and a primary winding (14) of a transformer, which parts are connected in a bridge arrangement. The first switching transistor (6) receives its drive by positive feedback via a secondary winding (30), a coupling capacitor (36) and a series resistor (38, 40). Upon commutation of the voltage on the secondary winding (30) the first switching transistor (6) is turned off, a discharge diode (44) providing a discharge path for the coupling capacitor (36) in order to achieve that the first switching transistor (6) is turned on more rapidly in the next switching cycle. However, the discharge diode (44) limits the cut-off voltage on the control electrode of the first switching transistor (6), so that turning off proceeds comparatively slowly. This effect is eliminated by a voltage source (46, 48, 52) and a further switching transistor (54) which is turned on upon commutation. The further switching transistor (54) then produces a higher cut-off voltage on the control electrode of the first switching transistor (6), as a result of which the first switching transistor (6) is turned off more rapidly.

Drive circuit for a flyback converter with switching transistors in

A device for determining the charge condition of a battery (10) comprises a current-frequency converter (50) which generates pulses of a frequency is dependent on the battery charge or discharge current. These pulses are counted and are used for computing the battery charge condition. In order to indicate a correct relative charge condition, especially in the case of a battery capacity which has changed due to, for example, ageing, the device comprises detection means (53) which detects an actual battery charge condition and correction means (52) for correcting the charge condition computed by a computing means (51). In one embodiment the correction means are integrated with the current-frequency converter and the frequency of the generated pulses is adapted to the present capacity of the battery.

Device for determining the charge condition of a battery

An electric shaving apparatus is provided which comprises a housing, a switch for activating switching cycles in which the apparatus is switched on and off, a holder for at least one external shaving member with hair-entry apertures, and an internal shaving member adapted to be driven by the external shaving member, the housing having a collecting space for shaving particles, which collecting space has a closing member with a locking mechanism, which locking mechanism comprises an actuating member, the apparatus comprising means for counting the number of switching cycles and a signalling device for signalling that cleaning of the collecting space is desirable in response to a predetermined or selected number of switching cycles. The signalling device comprises a light-emitting element in combination with the actuating member.

Electric shaving apparatus

In a device where a load (R.sub.1) is powered by a battery (6), if a detection means (10) detects a battery voltage below a first threshold value (V.sub.1) defined by an adjustable voltage source (20), a first time-measurement means (40, 50) measure the time interval during which the load 6 is powered by the battery (6), at a voltage below the first threshold value. If subsequently, the load is switched off and is not connected to the AC supply voltage via a power-supply circuit (1), the battery is discharged by a discharger (30). Second time-measurement means (40, 60) measure the time interval during which the discharger is operative until the detection means detect a battery voltage below a second threshold value (V.sub.2), which is defined by a voltage source (25) and at which the battery may be regarded as fully discharged or drained. After comparison of the sum of the time intervals measured by the first and the second time-measurement means with a reference value, correction means (70) correct the first threshold value in such a way that during a next discharge the time measured is more in agreement with the reference value.

Battery-powered device

In a device where a load (R.sub.L) is powered by a battery (6) if a first detection device (100) detects that the expired discharge time measured by measurement means (40, 70) is equal to a first reference value stored in a memory (22), a first time measurement apparatus (40, 80) measures the time during which the load is powered by the battery. When the load is switched off and is not connected to the AC supply voltage via a power-supply circuit (1), the battery is discharged by a discharger (9). Second time-measurement apparatus (50, 80) measure the time during which the discharger is operative until a second detection device (13) detects a battery voltage at which the battery may be regarded as fully discharged. After comparison of the sum of the time intervals measured by the first and the second time-measurement apparatus with a second reference value stored in a memory (21), a correction device corrects the reference value stored in a memory (22) in such the way that during a next discharge the sum of the time intervals measured by the first and the second time-measurement apparatus is in better agreement with the second reference value.

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Drachten, Netherlands

Geert J Bosscha