Device for energizing a D.C. motor, comprising an accumulator battery
First Claim
1. A device for energizing a d.c. motor comprising a flyback converter having an output circuit to which the motor may be connected, the flyback converter comprising a control circuit, which for the greater part is designed as an integrated circuit, for generating control pulses having a fixed frequency of the order of tens of kHz and with a controlled pulse duration for controlling a switching element which is connected in series with a primary winding of a transformer in the flyback converter, the control circuit including means for controlling the pulse duration of the control pulses depending on the output voltage and the current through the primary winding of the transformer, a rechargeable accumulator battery connected in series with a secondary winding of said transformer, switching means for connecting the motor in parallel with the accumulator battery, a power-supply capacitor for energizing the control-circuit, said power-supply capacitor being charged from the secondary winding of the transformer, the control circuit further comprising a voltage-level detector which keeps the control circuit in the active state when the voltage across the power-supply capacitor exceeds a specific threshold voltage, a starting circuit including a starting capacitor for supplying, in the case of an inactive control circuit, a control current for the switching element provided that the voltage across the starting capacitor and the instantaneous input voltage exceed a specific level, and wherein the pulse duration controlling means includes a detection circuit for detecting the current through the primary winding of the transformer and also the instantaneous value of the input voltage so that the pulse duration of the control pulses is also determined by the instantaneous value of the input voltage.
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Abstract
A small lightweight power-supply device a d.c. motor powered either by the a.c. supply voltage or by an accumulator battery which dissipates little power and has a well-defined output characteristic for a wide range of input voltages.
The device comprises a flyback converter, the forward sweep time being a function of the output voltage and the current through the primary winding of the transformer of the flyback converter. The forward sweep time is controlled by a control circuit which is integrated for the greater part. There is provided a starting circuit. A level detector in the control circuit ensures that this circuit is activated only when its supply voltage, which is applied via the secondary winding of the transformer, is sufficiently high.
33 Citations
14 Claims
- 1. A device for energizing a d.c. motor comprising a flyback converter having an output circuit to which the motor may be connected, the flyback converter comprising a control circuit, which for the greater part is designed as an integrated circuit, for generating control pulses having a fixed frequency of the order of tens of kHz and with a controlled pulse duration for controlling a switching element which is connected in series with a primary winding of a transformer in the flyback converter, the control circuit including means for controlling the pulse duration of the control pulses depending on the output voltage and the current through the primary winding of the transformer, a rechargeable accumulator battery connected in series with a secondary winding of said transformer, switching means for connecting the motor in parallel with the accumulator battery, a power-supply capacitor for energizing the control-circuit, said power-supply capacitor being charged from the secondary winding of the transformer, the control circuit further comprising a voltage-level detector which keeps the control circuit in the active state when the voltage across the power-supply capacitor exceeds a specific threshold voltage, a starting circuit including a starting capacitor for supplying, in the case of an inactive control circuit, a control current for the switching element provided that the voltage across the starting capacitor and the instantaneous input voltage exceed a specific level, and wherein the pulse duration controlling means includes a detection circuit for detecting the current through the primary winding of the transformer and also the instantaneous value of the input voltage so that the pulse duration of the control pulses is also determined by the instantaneous value of the input voltage.
- 9. A power supply device for energizing a D.C. motor comprising, a flyback converter that includes a transformer having a primary and a secondary winding and a controlled switching element connected in series with the primary winding across a pair of input supply voltage terminals, an output terminal coupled to the secondary winding for deriving an output voltage for said motor, switching means for selectively connecting a rechargeable battery in parallel with the motor, a control circuit coupled to a control electrode of said switching element for deriving control pulses of a fixed frequency and with a controllable pulse duration for controlling the operation of the switching element, a power-supply capacitor responsive to the voltage developed at said secondary winding for deriving an energizing voltage for the control circuit, and said control circuit comprises, means for controlling the pulse duration of the derived control pulses as a function of the output voltage and the current in the transformer primary winding, a voltage-level detector coupled to the power-supply capacitor for activating the control circuit when the voltage across said power-supply capacitor exceeds a given voltage level, and a starting circuit including a starting capacitor coupled to the primary winding for supplying a start signal to the control elctrode of the controlled switching element provided that the voltage across the starting capacitor and the input voltage exceed a given level and the control circuit is inactive.
Specification