Storage capacitor power supply and method of operating same

• US 5,977,748 A
• Filed: 07/21/1998
• Issued: 11/02/1999
• Est. Priority Date: 04/03/1992
• Status: Expired due to Term

• Current Assignee: Nantong Jianghai Capacitor Company Limited, Okamura Laboratory Inc.
• Original Assignee: JEOL Limited
• Inventors: Okamura, Michio
• Primary Examiner(s): Tso, Edward H.
• Application Number:
  US09/120,683
• Time in Patent Office: 469 Days
• Field of Search: 320/116, 320/118, 320/119, 320/120, 320/127, 320/128, 320/135, 320/166
• US Class Current: 320/118
• CPC Class Codes: B60L 50/40 using propulsion power supplied by capacitors
• CPC Class Codes: B60L 53/00 Methods of charging batteries, specially adapted for electric vehicles; Charging stations or on-board charging equipment therefor; Exchange of energy storage elements in electric vehicles
• CPC Class Codes: B60L 53/55 Capacitors
• CPC Class Codes: B60L 58/10 for monitoring or controlling batteries
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits
• CPC Class Codes: H02J 7/345 using capacitors as storage or buffering devices
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
• CPC Class Codes: Y02T 90/12 Electric charging stations
• CPC Class Codes: Y02T 90/14 Plug-in electric vehicles

Abstract

A storage capacitor power supply has a plurality of electric double layer capacitors connected in series. Each capacitor has connected in parallel therewith a charge-limiting circuit. Each charge-limiting circuit measures a voltage across its corresponding capacitor and causes a charging current to bypass the capacitor when it is charged to a value corresponding to a reference voltage established by the charge-limiting circuit. When all the capacitors are charged to their corresponding reference voltages, the charging current is terminated whereafter the capacitors are discharged with a discharge current. When the capacitors are charged with a recharging current from a partially discharged state, the capacitors are charged to values corresponding to their respective reference voltages at the same time without bypassing the recharging current around one or more of the capacitors.

Claims

1. A storage capacitor power supply which stores electricity in a capacitor block having a plurality of capacitors connected in series to supply electric power to a load, the power supply comprising:

a charging power supply connected to electrically charge the capacitor block with a charging current; and

a charge-limiting circuit which includes a bypass circuit connected in parallel with each capacitor of the capacitor block and a detection circuit, with each detection circuit connected to detect the voltage developed across the capacitor connected in parallel therewith, wherein;

for each capacitor of the capacitor block, the charge-limiting circuit initializes the voltage thereof for discharging and charging based on a reference voltage by causing the bypass circuit to bypass the charging current around the capacitor when a voltage detected by the detection circuit reaches the reference voltage;

once initialized, all the capacitors are discharged with a common discharging current and recharged with a common recharging current; and

in response to receiving the recharging current, each capacitor reaches the reference voltage absent the need to bypass the charging current around any capacitor.

2. The power supply as set forth in claim 1, wherein each capacitor reference voltage is the same.

3. A method of operating a capacitor power supply comprising a plurality of capacitors connected in series to supply electric power on discharge, the method comprising the steps of:

a) first, charging all capacitors to the same voltage bypassing the charging current around any capacitor that has already been charged to the voltage; and

b) thereafter, discharging and charging the capacitors such that on recharging all capacitors reach the voltage at the same time without the need for bypassing current around capacitors.

4. A method of charging and discharging a capacitor power supply having a plurality of capacitors connected in series to supply electric power to a load on discharge, the method comprising the steps of:

a) starting with at least one capacitor substantially discharged, charging the plurality of capacitors connected in series with a charging current;

b) comparing a voltage across each capacitor to a corresponding reference voltage;

c) when each capacitor is charged to a value corresponding to its reference voltage, bypassing the charging current therearound;

d) terminating the charging current when all the capacitors are charged to their corresponding reference voltages;

e) discharging the plurality of capacitors connected in series with a discharge current; and

f) charging the plurality of capacitors connected in series with a recharging current such that all the capacitors are charged to values corresponding to their respective reference voltages at the same time without bypassing the recharging current around at least one of the capacitors.

5. The method as set forth in claim 4, wherein each capacitor reference voltage is the same.