Charging voltage control circuit for battery chargers
First Claim
1. An improved method of operating a lead-acid-battery charger of the pulse-width modulated type having a duty cycle varying in response to charging current to maintain a desired charging voltage comprising the steps of:
- a) holding the charging voltage at a constant voltage when the charging current is above a predetermined value; and
b) increasing the charging voltage when the charging current is in a range below the predetermined value by sensing the duty cycle and adjusting the charging voltage in response to changes in the duty cycle.
16 Assignments
0 Petitions
Accused Products
Abstract
Charging voltage and current control circuits for battery chargers provide for a constant output voltage above a first predetermined value of charging current and an increasing output voltage below the first predetermined value of charging current. The charger makes use of a pulse-width modulated control circuit utilizing a variable duty cycle proportional to charging current and couples a signal proportional to charging current via a diode-resistor network to the pulse-width modulator for values below the first predetermined value of charging current. A current limit control circuit provides a current limit function by driving the pulse-width modulator to a minimum duty cycle during overcurrent conditions.
17 Citations
11 Claims
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1. An improved method of operating a lead-acid-battery charger of the pulse-width modulated type having a duty cycle varying in response to charging current to maintain a desired charging voltage comprising the steps of:
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a) holding the charging voltage at a constant voltage when the charging current is above a predetermined value; and b) increasing the charging voltage when the charging current is in a range below the predetermined value by sensing the duty cycle and adjusting the charging voltage in response to changes in the duty cycle. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An improved charging voltage trim circuit for use in a variable duty cycle pulse-width modulated battery charger of the type having a charging current proportional to the duty cycle, the trim circuit comprising:
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a) a resistor-capacitor averaging network connected to time-average the duty cycle to provide a voltage proportional to the charging current; and b) means for coupling the averaging network voltage to an error detection and correction means for controlling a charging voltage output of the battery charger while the charging current is below a predetermined value such that the charging voltage increases as the charging current decreases in a range below the predetermined value of the charging current. - View Dependent Claims (9)
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10. An output charging voltage trim circuit for use in a variable duty cycle battery charger of the type providing an output charging voltage delivered by a pulse-width modulated inverter driving a DC converter to provide an output charging current proportional to the duty cycle, the trim circuit comprising:
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a) a first capacitor connected to an input of the DC converter to provide AC coupling of the inverter output; b) a first resistor connected in series with the first capacitor to receive the AC coupled inverter output; c) a second capacitor connected in series with the first resistor and operable with the first resistor to form a duty cycle integrator; d) a second resistor connected in parallel with the second capacitor to continuously discharge the second capacitor is proportional to the duty cycle of the pulse-width modulated inverter; and e) coupling means for coupling the voltage across the second capacitor to a pulse modulation input when the output charging current is below a predetermined value such that the output charging voltage increases in proportion to decreases in the output charging current below the predetermined value. - View Dependent Claims (11)
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Specification