Voltage converter for a power supply
A SEPIC type voltage converter ( 101 ) comprises a transformer ( 40 ) having a primary winding ( 41 ) and a storage capacitor ( 33 ) connected in series, and a controllable switch ( 51 ) coupled in parallel with said series combination. The transformer has a first secondary winding ( 42 1 ) and a first rectifying diode ( 43 1 ) connected in series, and a first capacitor ( 44 1 ) coupled in parallel with said series combination, one terminal of said first capacitor ( 44 1 ) being coupled to an output terminal ( 45 1 ). The voltage converter also comprises feedback means ( 50; 53, 52 ) coupled to said output terminal ( 45 1 ) and controlling said controllable switch ( 51 ). The transformer further has a second secondary winding ( 62 ) and a second rectifying diode ( 63 ) connected in series, wherein this series combination is also coupled to said output terminal ( 45 1 ) in order to limit the voltage across the storage capacitor.
1. A voltage converter ( 1 ; 201 ) comprising:
an energy storage section ( 111 ) comprising a first series combination of a storage capacitor ( 33 ) and a first inductor ( 41 ; 141 );
a controllable switch ( 51 ) coupled in parallel with said first series combination;
an energy transfer section ( 112 ) comprising a second series combination of a first rectifying diode ( 43 1 ; 143 ) and a first smoothing capacitor ( 44 1 ; 144 ), the first rectifying diode being coupled to the first inductor;
a first output terminal ( 45 1 ) coupled to a node between said first rectifying diode ( 43 1 ; 143 ) and a first smoothing capacitor ( 44 1 ; 144 );
feedback means ( 50 ; 53 , 52 ) coupled to said output terminal ( 45 1 ) for controlling said controllable switch ( 51 ); and
voltage clamping means ( 60 ; 160 ) for clamping a voltage across the storage capacitor ( 33 ).
2. A voltage converter according to claim 1 , wherein the following formula is satisfied, at least substantially:
N 62 /N 41= V OUT,1 /V CLAMP ,
wherein:
N 62 is the number of turns of said second inductor ( 62 ; 162 );
N 41 is the number of turns of said first inductor ( 41 ; 141 );
V OUT,1 is the regulated output voltage at said first output terminal ( 45 1 );
V CLAMP is the maximum allowed voltage across said storage capacitor ( 33 ).
3. A voltage converter according to claim 1 , wherein said voltage clamping means ( 60 ; 160 ) comprises a second inductor ( 62 ; 162 ) inductively coupled to said first inductor ( 41 ; 141 ), and a second rectifying diode ( 63 ; 163 ) connected in series with said inductor ( 62 ; 162 );
wherein said series combination of second rectifying diode ( 63 ; 163 ) and said second inductor ( 62 ; 162 ) is coupled to a reference voltage.
4. A voltage converter according to claim 3 , wherein said reference voltage is a voltage at said first output terminal ( 45 1 ).
5. A voltage converter according to claim 3 , wherein said first inductor ( 41 ) has a phase terminal ( 48 ) directed away from ground (GND; GNDP), and wherein said second inductor ( 62 ; 162 ) has a phase terminal ( 68 ) directed towards ground (GND; GNDS).
6. A voltage converter according to claim 5 , wherein said second rectifying diode ( 63 ; 163 ) is arranged between a reference terminal ( 67 ; 167 ) of second inductor ( 62 ; 162 ) and said first output terminal ( 45 1 ).
7. A voltage converter according to claim 6 , wherein said second rectifying diode ( 63 ; 163 ) has its anode connected to said reference terminal ( 67 ; 167 ) of second inductor ( 62 ; 162 ).
8. A voltage converter according to claim 1 , comprising a transformer ( 40 ) having a primary winding ( 41 ) and at least one secondary winding ( 42 1 );
wherein said first inductor ( 41 ) comprises said primary winding ( 41 ), and said first rectifying diode ( 43 1 ) is connected in series with a first of said secondary windings ( 42 1 ).
9. A voltage converter according to claim 8 , wherein said first secondary winding ( 42 1 ) has a phase terminal directed towards said output terminal ( 45 1 ) and a reference terminal directed towards ground (GND; GNDS).
10. A power supply ( 210 ) for generating at least one output voltage on the basis of an input voltage, the power supply comprising a voltage converter according to claim 1 .
11. An electronic apparatus ( 200 ) such as a monitor or a television, comprising a power supply ( 210 ) according to claim 10 .