Circuit arrangement comprising a power supply unit
View Patent ↗The circuit arrangement comprises a power supply unit with a first power supply only for the analogue signal processing part and for the control part of a respective device. For the digital signal processing part, a second, separate switched mode power supply is provided, which is switched off, when only the analogue signal processing part is active, and which is in operation, when the digital signal processing part is on. For switching on and off of the second switched mode power supply, the power supply comprises a switching circuit ( 18 ), which is coupled in a special embodiment to a control loop ( 15 ) on the secondary side, for switching off the second power supply at the primary side via a galvanic isolating means ( 14 ). The switching circuit is provided with a supply voltage (12VS) from the first power supply and receives the on/off command from the control part, e. g. a microprocessor. The power supply unit is used advantageously within a D-VHS recorder, and the first power supply provides the power for the control part and the analogue circuit processing of the recorder. The second switched mode power supply is associated with the digital signal processing part. The second switched mode power supply is switched on for example, when a D-VHS tape is inserted into the recorder.
1. Circuit arrangement comprising an analogue signal processing part, a digital signal processing part, a control part including a micro-controller and a power supply unit, wherein said power supply unit comprises:
a first switched mode power supply for said analogue signal processing part and for said control part, and
a second switched mode power supply with a transformer having a primary and a secondary side for providing power to said digital signal processing part, said second switched mode power supply comprising on the secondary side a switching circuit coupled to a control loop for output power regulation of said second switched mode power supply, said switching circuit being provided with a constant supply voltage from said first switched mode power supply, said second switched mode power supply being switched on and off by said micro-controller via said switching circuit.
2. Circuit arrangement according to claim 1 , wherein said micro-controller switches on and off said second switched mode power supply on the primary side via a coupling means.
3. Circuit arrangement according to claim 1 , wherein said first and second switched mode power supply comprise its own start-up circuit and transformer for mains isolation.
4. Circuit arrangement according to claim 3 , wherein said second switched mode power supply is arranged separately on a printed circuit board and comprises its own mains filter, which is coupled to a mains input voltage.
5. Circuit arrangement to according to claim 1 , wherein the circuit arrangement is arranged within a D-VHS video recorder, and the first switched mode power supply is provided for supplying power to the analogue reading and recording part, to the drive mechanism and to the controlling part of the recorder.