EP0474471A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Fixed frequency single ended forward converter switching at zero voltage
Assignee: ITT Inc
•
Filing: 1991-09-04
•
Granted: —
•
Expires: 2011-09-04
Abstract
Abstract A single ended forward DC-to-DC converter is operated with a main switch in series circuit with a primary winding of the isolation transformer and an auxiliary switch for charging a reset capacitor also in circuit with said primary winding. The main switch and auxiliary switch are operated through control logic so that neither switch is On at the same time. A predetermined dead time is provided between turning OFF the auxiliary switch and turning ON the main switch to allow the output capacitance of the main switch to discharge into the secondary of the transformer. Current discharge into the secondary of the transformer during this time period is limited either by a saturable reactor in series circuit with the secondary or a selectively controlled rectifier.
Inventors
- 👤 Ionel Jitaru
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-30 04:58
CPC Classifications
H; H02; H02M; H02M3/00; H02M3/22; H02M3/24; H02M3/28; H02M3/325; H02M3/335; H02M3/33561; H02M3/33569; H02M3/01
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
285 words
A single ended, zero-voltage switching, forward DC-to-DC converter, characterised by a DC voltage source (44), a transformer (48) having a primary (50) and secondary (52) winding and main switching means for selectively coupling the voltage source across the primary winding of the transformer and further characterised by auxiliary switching means (32) for selectively allowing the voltage across the primary winding (50) to reach zero, the main switching means (30) and auxiliary switching means (32) each having an OFF period and an ON period with the auxiliary switching means being non-conductive prior to the ON period of the main switching means by a predetermined time period sufficient to allow the voltage across the main switching means to reach zero voltage and with the auxiliary switching means remaining non-conductive until the main switching means cycles through its corresponding ON period and OFF period, by a reset capacitor (38) coupled between the auxiliary switching means and AC ground of the converter, by third switching means (56,142) coupled in series with the secondary winding (52) of the transformer (48) for selectively remaining at least partially non-conductive as the voltage across the main switching means decreases, the third switching means becoming conductive when the voltage across the main switching means reaches zero, by a first rectifier means (58) coupled in series with the third switching means for conducting current from the third switching means and by a control circuit means (140,144) for selectively operating the main switching means, auxiliary switching means and third switching means to transfer energy through the converter by modification of the duty cycle of operation of at least the main and auxiliary switching means to achieve turn ON of the main switching means at zero voltage.
Claim 2
Dependent Claim
22 words
A converter according to claim 1, further characterised by a discrete, resonant capacitor (46) connected in parallel with the main switching means.
Claim 3
Dependent Claim
63 words
A converter according to claim 1, characterised in that the first rectifying means and the third switching means comprises a unidirectionally controlled switch means (142) selectively operated by the control means (144) so that the unidirectionally controlled switching means is non-conductive after the voltage across the main switching means reaches zero and is conductive during corresponding ON time of the main switching means.
Claim 4
Dependent Claim
21 words
A converter according to claim 1, characterised in that the transformer (48) comprises a plurality of secondary windings (52(1) to 52(m)).
Claim 5
Dependent Claim
17 words
A converter according to claim 1, characterised in that third switching means is a saturable reactor (56).
Claim 6
Dependent Claim
32 words
A converter according to claim 1, characterised by a load (66) and a load inductor (60) which is coupled in series circuit between the first rectifying means (58) and the load (66).
Claim 7
Dependent Claim
44 words
A converter according to claim 6, characterised in that a second rectifying means (62) is coupled between ground of the secondary winding (52) of the transformer (48) and the input to the load inductor (60) at its coupling to the first rectifying means (58).
Claim 8
Dependent Claim
42 words
A converter according to claim 6, characterised in that the control circuit means (140) comprises sensory means for sensing voltage across the load and maintains a constant voltage across the load by varying the ON period of the main switching means (30).
Claim 9
Dependent Claim
42 words
A converter according to claim 6, characterised in that the control circuit means (144) comprises sensory means for sensing voltage across the load and maintains a constant voltage across the load by varying the ON period of the third switching means (142).
Claim 10
Dependent Claim
49 words
A converter according to claim 6, characterised in that the control circuit means (144) comprises sensory means for sensing voltage across the load and maintains a constant voltage across the load by varying the ON period of both the main switching means (30) and the third switching means (142).
Claim 11
Dependent Claim
18 words
A converter according to claim 6, characterised in that the third switching means is a saturable reactor (56).
Claim 12
Dependent Claim
18 words
A converter according to claim 6, characterised in that the third switching means is a synchronised switch (142).
Claim 13
Dependent Claim
54 words
A converter according to claim 6, characterised by a voltage reference (REF) and by sensory means (102) for sensing voltage across the load and for comparing the difference in voltage across the load and the voltage reference, the difference being compared to a signal proportional to the current through the main switching means (30).
Claim 14
Dependent Claim
205 words
A single ended forward converter in which energy is transferred from a primary winding to a secondary winding of a transformer during an ON period of a primary switch, and in which circuitry is provided for recycling the magnetising energy stored in said transformer to reset it during the OFF period of said main switch such that discharge of output capacitance of said main switch to zero is achieved prior to turn ON of main switch on a subsequent cycle, the converter being characterised by a reset capacitor (38), an auxiliary switch (32) including an anti-parallel diode (106) coupled in series with the reset capacitor (38), switch control means operating the auxiliary switch including the anti-parallel diode in accordance with a control logic such that: (a) the auxiliary switch (32) including the anti-parallel diode (106) is opened prior to the ON period of the main switch (30) for a period of time sufficient to discharge the output capacitance of the main switch (30), (b) the auxiliary switch (32) including the anti-parallel diode (106) closes at the same time the main switch (30) opens, and (c) the auxiliary switch (32) including the anti-parallel diode (106) is open during the ON period of the main switch (30).
Claim 15
Dependent Claim
30 words
A converter according to claim 14, further characterised by means for inhibiting current in the secondary winding of the transformer until the output capacitance of the main switch is dissipated.
Claim 16
Dependent Claim
27 words
A converter according to claim 15, characterised in that the means is a saturable reactor (56) in series circuit with the secondary winding (52) of the transformer.
Claim 17
Independent Claim
109 words
A method of operating a single ended forward DC-to-DC converter characterised by the steps of storing energy in a primary winding (50) of a transformer (48) by flowing DC current through the primary winding in series circuit with a main switch (30), turning OFF the main switch, allowing the output capacitance of the main switch to discharge through the primary winding into a secondary winding (52) of the transformer until discharged and turning ON a secondary switch (32) in series circuit with the primary of the transformer to charge a reset capacitor (38), the secondary switch being turned ON only after there is zero voltage across the main switch.
Claim 18
Dependent Claim
35 words
A method according to claim 17, further characterised by the step of inhibiting current flow through the secondary winding (52) of the transformer until the output capacitance of the main switch is completely dissipated therethrough.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
Maintenance schedule is calculated for granted US utility patents.