Circuit for generating a DC voltage supply and a driver circuit using the DC voltage supply circuit
A circuit is for generating a DC voltage supply from a higher voltage AC signal. A first capacitor (C 1 ) is in series between an input ( 12 ) and a first node (N 1 ), a first diode (D 1 ) is in forward direction between the first node and a DC voltage supply node (Nout), a second capacitor (C 2 ) is between the DC voltage supply node and a reference terminal, and a second diode (D 2 ) is in forward direction between the reference terminal and the first node. This defines a general charge pump architecture. A third capacitor (C 3 ) is then provided between the first node and a second node (N 2 ) and a controllable voltage supply ( 60 ) defines the voltage at the second node (N 2 ). This adjustable node voltage improves the efficiency of the circuit, in that excess current can be dissipated efficiently, and it can be implemented with a simple circuit.
1. A circuit for generating a DC voltage supply from a higher voltage AC signal, comprising:
an input for receiving the higher voltage AC signal;
a first capacitor in series between the input and a first node;
a first diode in forward direction between the first node and a DC voltage supply node;
a second capacitor between the DC voltage supply node and a reference terminal;
a third capacitor between the first node and a second node;
a second diode in forward direction between the reference terminal and the first node;
a controllable voltage supply arranged to provide a voltage to the third capacitor via a third diode; and
a diode arrangement comprising the third diode and a fourth diode in series across the controllable voltage supply, with the junction between the third and fourth diodes defining the second node.
2. A circuit as claimed in claim 1 , further comprising a voltage clamping device between one terminal of the first diode and the reference terminal, wherein the voltage clamping device for example is a Zener diode.
3. A circuit as claimed in claim 1 , wherein the reference terminal is ground.
4. A circuit as claimed in claim 1 , wherein the controllable voltage supply has a terminal connected to a DC node or a low frequency AC node, directly or via a capacitor.
5. A driver circuit comprising:
a resonant switch mode power converter providing a first output for driving a load; and
a DC voltage supply circuit as claimed in claim 1 , wherein the high voltage AC signal is a second output from the resonant switch mode power converter.
6. A driver circuit as claimed in claim 5 , wherein the resonant switch mode power converter comprises an LCC converter.
7. A lighting circuit comprising:
a driver circuit as claimed in claim 5 ;
a lighting load driven by the first output; and
auxiliary circuitry driven by the second output.