Compact low noise low power dual mode battery charging circuit
First Claim
1. A battery charger comprising in combination:
- (a) a first rectifier receiving a line voltage and producing a rectified sinusoidal voltage;
(b) a transformer having a primary winding coupled to receive the rectified sinusoidal voltage and a secondary winding, a second rectifier being coupled between terminals of the secondary winding and terminals of a battery;
(c) a switch coupled in series relation with a terminal of the primary winding;
(d) means coupled to the switch for producing a signal indicative of current flowing through the switch and primary winding;
(e) battery condition means for producing a battery condition voltage representative of a voltage between the terminals of the battery;
(f) peak detect and hold means coupled to receive the voltage proportional to the battery condition voltage and detect and hold a peak value thereof;
(g) voltage droop measuring means for comparing an output voltage of the peak detect and hold means with the voltage proportional to the battery condition voltage to produce a voltage droop signal when the voltage proportional to the battery condition voltage falls a predetermined threshold voltage below the output voltage of the peak detect and hold means; and
(h) modulating means coupled to receive a signal representative of the voltage droop signal and the signal indicative of current flowing through the primary winding for producing a control signal applied to the switch to control flow of current through the primary winding in accordance with the battery condition voltage, the modulating means including means for producing a turn off time for the switch equal to a predetermined proportion of a resonant period of the primary winding and means for varying turn on time for the switch in response to the signal indicative of current flowing through the primary winding.
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Accused Products
Abstract
A low noise battery charger includes a rectifier to convert AC line voltage to a rectified sinusoidal voltage that is applied to a primary winding of a transformer. Another rectifier coupled to a first secondary winding applies a charging current to a battery. A switch coupled in series with the primary winding controls current therein. A rectifier coupled to another secondary winding produces a battery condition voltage. An incrementing signal synchronized with the rectified sinusoidal voltage increments a ratchet DAC until its output voltage exceeds the battery condition voltage. A low charging mode signal is produced when the battery condition voltage falls a certain amount below the DAC output voltage. Flow of current through the primary winding is controlled by operating the switch at a relatively high frequency and by producing constant turn off times for the switch which are proportional to the resonant period of the primary winding circuit and also by modulating turn on times for the switch in response to the signal indicative of primary winding current. Maximum power transfer across the transformer is thereby achieved without flyback voltage of the transformer exceeding breakdown voltage of the switch, and zero current switching is achieved.
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Citations
32 Claims
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1. A battery charger comprising in combination:
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(a) a first rectifier receiving a line voltage and producing a rectified sinusoidal voltage; (b) a transformer having a primary winding coupled to receive the rectified sinusoidal voltage and a secondary winding, a second rectifier being coupled between terminals of the secondary winding and terminals of a battery; (c) a switch coupled in series relation with a terminal of the primary winding; (d) means coupled to the switch for producing a signal indicative of current flowing through the switch and primary winding; (e) battery condition means for producing a battery condition voltage representative of a voltage between the terminals of the battery; (f) peak detect and hold means coupled to receive the voltage proportional to the battery condition voltage and detect and hold a peak value thereof; (g) voltage droop measuring means for comparing an output voltage of the peak detect and hold means with the voltage proportional to the battery condition voltage to produce a voltage droop signal when the voltage proportional to the battery condition voltage falls a predetermined threshold voltage below the output voltage of the peak detect and hold means; and (h) modulating means coupled to receive a signal representative of the voltage droop signal and the signal indicative of current flowing through the primary winding for producing a control signal applied to the switch to control flow of current through the primary winding in accordance with the battery condition voltage, the modulating means including means for producing a turn off time for the switch equal to a predetermined proportion of a resonant period of the primary winding and means for varying turn on time for the switch in response to the signal indicative of current flowing through the primary winding. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method of charging a battery using a battery charger, comprising the steps of:
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(a) rectifying an AC voltage to produce a sinusoidal rectified voltage and applying it to a primary winding of a transformer, a rectifier being coupled between terminals of a secondary winding of the transformer and terminals of a battery to supply a rectified charging current to the battery; (b) operating a switch coupled in series with a terminal of the primary winding to control current through the primary winding; (c) producing a signal indicative of primary winding current; (d) producing a battery condition voltage representative of voltage between the terminals of the battery; (e) detecting and storing a peak value of a reference voltage proportional to the battery condition voltage; (f) comparing the stored peak value with the voltage proportional to the battery condition voltage to produce a charging mode signal with a low charging mode state when the voltage falls a predetermined threshold voltage below the peak value; and (g) controlling flow of current through the switch by turning the switch off for times equal to a predetermined proportion of a resonant period of the primary winding and turning the switch on for times which vary in response to the signal indicative of the primary winding current.
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14. A method of charging a battery using a battery charger, comprising the steps of:
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(a) rectifying an AC voltage to produce a sinusoidal rectified voltage and applying it to a primary winding of a transformer, a rectifier being coupled between terminals of a secondary winding of the transformer and terminals of a battery to supply a rectified charging current to the battery; (b) operating a switch coupled in series with a terminal of the primary winding to control current through the primary winding; (c) producing a signal indicative of primary winding current; (d) controlling flow of current through the switch by turning the switch off for times equal to a predetermined proportion of a resonant period of the primary winding and turning the switch on for times which vary in response to the signal indicative of the primary winding current; (e) producing a battery charge condition signal indicating that the battery has been substantially fully charged in a fast charge mode; and (f) reducing the amounts of time the switch is turned on in step (d) in response to the battery charge condition signal to continue charging of the battery in a trickle charge mode. - View Dependent Claims (15)
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16. A battery charger, comprising in combination:
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(a) means for rectifying an AC line voltage to produce a sinusoidal rectified voltage; (b) a transformer having a primary winding receiving the sinusoidal rectified voltage; (c) a rectifier coupled between terminals of a secondary winding of the transformer and terminals of a battery to supply a rectified charging current to the battery; (d) a switch coupled in series with a terminal of the primary winding to control current through the primary winding; (e) means for operating the switch to control current through the primary winding; (f) means for producing a signal indicative of primary winding current; (g) means for controlling flow of current through the switch by turning the switch off for times proportional to a resonant period of the primary winding and turning the switch on for times which vary in response to the signal indicative of the primary winding current; (h) means for detecting a battery charge condition and producing a battery charge condition signal indicating that the battery has been substantially fully charged in a fast charge mode; and (i) means for reducing a duty cycle of times the switch is turned on in response to the battery charge condition signal to continue charging of the battery in a trickle charge mode.
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17. A method of charging a battery, comprising the steps of:
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(a) rectifying an AC line voltage to produce a sinusoidal rectified voltage and applying it to a primary winding of a transformer, a rectifier being coupled between terminals of a secondary winding of the transformer and terminals of a battery to supply a rectified charging current to the battery; (b) causing a resonant circuit including inductance of the primary winding and a capacitor coupled thereto to resonate at a predetermined frequency while a switch coupled to a terminal of the primary winding is off; (c) operating the switch coupled in series with a terminal of the primary winding to cause current to flow through the primary winding and stop the resonating; (d) producing a signal indicative of the current flowing through the primary winding; and (e) controlling flow of current through the switch by turning the switch off for times generally proportional to the period of the predetermined frequency and turning the switch on for times which vary in response to the signal indicative of the primary winding current. - View Dependent Claims (18, 19, 20, 21, 22, 23)
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24. A battery charger comprising in combination:
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(a) means for rectifying an AC line voltage to produce a sinusoidal rectified voltage; (b) a transformer having a primary winding receiving the sinusoidal rectified voltage; (c) a resonant circuit including inductance of the primary winding and a capacitor coupled thereto having a resonant frequency; (d) a switch coupled in series with a terminal of the primary winding to control current through the primary winding, the resonant circuit resonating while the switch is off; (e) means for operating the switch to cause current to flow through the primary winding and stop the resonating; (f) means for producing a signal indicative of the current flowing through the primary winding; (g) means for controlling flow of current through the switch by turning the switch off for times proportional to the period of the resonant frequency and turning the switch on for times which vary in response to the signal indicative of the primary winding current; and (h) a secondary winding and means coupling first and second terminals of the secondary winding to first and second terminal, respectively, of a battery. - View Dependent Claims (25)
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26. A battery charger comprising in combination:
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(a) a rectifier circuit operative to rectify an AC line voltage to produce a sinusoidal rectified voltage; (b) a transformer having a primary winding receiving the sinusoidal rectified voltage; (c) a resonant circuit including inductance of the primary winding and a capacitor coupled thereto having a resonant frequency; (d) a switch coupled in series with a terminal of the primary winding to control current through the primary winding, the resonant circuit resonating while the switch is off; (e) a sensing circuit coupled to the primary winding and operative to produce a signal indicative of the current flowing through the primary winding; (f) a control circuit coupled to the sensing circuit and operative to turn the switch off for times proportional to the period of the resonant frequency and to turn the switch on for times which vary in response to the signal indicative of the primary winding current; and (g) a secondary winding including first and second terminals coupled to first and second terminal, respectively, of a battery. - View Dependent Claims (27, 28, 29, 30, 31, 32)
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Specification