Switched-mode power supply
First Claim
1. A switched-mode power supply circuit adapted to operate in a normal operating mode and a standby mode, said switched-mode power supply circuit comprising:
- a switch;
a control circuit for controlling the switch, said control circuit comprising a voltage-detection means coupled to receive a power supply voltage for bringing the control circuit to an off-state if the power supply voltage has decreased to an off-level, and for bringing the control circuit to an on-state if the power supply voltage has increased to a starting level;
a transformer having a primary winding and being incorporated in a series arrangement with the switch, said series arrangement being coupled to a DC input voltage source, the transformer further having a power supply winding coupled to the voltage-detection means, the power supply winding supplying a take-over voltage in the normal operating mode at a value at which the control circuit is in the on-state; and
power supply means coupled to the DC input voltage source for receiving an input current for applying a power supply current to the control circuit;
characterized in thatthe switched-mode power supply circuit further comprises means for decreasing the take-over voltage in the standby mode and, in response to a standby mode indication signal, to a value at which the control circuit may be alternately in the on-state and in the off-state.
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Accused Products
Abstract
In a standby mode, a switched-mode power supply circuit may be operated in a burst mode with reduced secondary voltages (Vo1, Vo2) for supplying a standby voltage (Vo1) at a very high efficiency. In a normal operating mode of the power supply, a control circuit (1) is maintained in its on-state by a power supply voltage (Vcc) generated by the power supply. The control circuit (1) supplies control pulses (Vd) for switching the power supply. The burst mode is obtained by decreasing the power supply voltage (Vcc) generated for the control circuit (1) to such an extent that, without any further provisions, the control circuit (1) reaches an off-state in which no control pulses (Vd) are generated. In the standby mode, the control circuit (1) is supplied with current by a power supply circuit (4). In the off-state, the control circuit (1) takes up a smaller power supply current (Icc) from the power supply circuit (4) than it is supplying and the power supply voltage (Vcc) increases until the control circuit (1) reaches the on-state and starts generating the control pulses (Vd). In the on-state, the control circuit (1) takes up a larger current from the power supply circuit (4) than it is supplying and the power supply voltage (Vcc) decreases until the control circuit (1) reaches the off-state again. In this way, the power supply, in the standby mode is each time active during first periods and inactive during second periods. To bring the power supply voltage to the standby mode, the power supply voltage (Vcc) generated for the control circuit (1) is decreased in such a way that also the secondary voltage (Vs1, Vs2) are decreased.
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Citations
20 Claims
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1. A switched-mode power supply circuit adapted to operate in a normal operating mode and a standby mode, said switched-mode power supply circuit comprising:
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a switch; a control circuit for controlling the switch, said control circuit comprising a voltage-detection means coupled to receive a power supply voltage for bringing the control circuit to an off-state if the power supply voltage has decreased to an off-level, and for bringing the control circuit to an on-state if the power supply voltage has increased to a starting level; a transformer having a primary winding and being incorporated in a series arrangement with the switch, said series arrangement being coupled to a DC input voltage source, the transformer further having a power supply winding coupled to the voltage-detection means, the power supply winding supplying a take-over voltage in the normal operating mode at a value at which the control circuit is in the on-state; and power supply means coupled to the DC input voltage source for receiving an input current for applying a power supply current to the control circuit;
characterized in thatthe switched-mode power supply circuit further comprises means for decreasing the take-over voltage in the standby mode and, in response to a standby mode indication signal, to a value at which the control circuit may be alternately in the on-state and in the off-state. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A picture display apparatus comprising:
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an input circuit for receiving an AC input voltage and for supplying a DC input voltage a switched-mode power supply circuit coupled to receive the DC input voltage for supplying an operating voltage and a standby voltage an addressing circuit coupled to receive the operating voltage for addressing a display unit; and operating means coupled to receive the standby voltage and operating commands, and for supplying a standby mode indication signal, wherein said switched-mode power supply circuit is adapted to operate in a normal operating mode and a standby mode, said switched-mode power supply circuit comprising; a switch; a control circuit for controlling the switch, said control circuit comprising a voltage-detection means coupled to receive a power supply voltage for bringing the control circuit to an off-state if the power supply voltage has decreased to an off-level, and for bringing the control circuit to an on-state if the power supply voltage has increased to a starting level; a transformer having a primary winding and being incorporated in a series arrangement with the switch, said series arrangement being coupled to a DC input voltage source, the transformer further having a power supply winding coupled to the voltage-detection means, the power supply winding supplying a take-over voltage in the normal operating mode at a value at which the control circuit is in the on-state; and power supply means coupled to the DC input voltage source for receiving an input current for applying a power supply current to the control circuit;
characterized in thatthe switched-mode power supply circuit further comprises means for decreasing the take-over voltage in the standby mode and, in response to a standby mode indication signal, to a value at which the control circuit may be alternately in the on-state and in the off-state.
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Specification