Circuit and method for measuring battery voltage by time of discharge of a capacitor
US4866389A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 17, 1988 |
| Grant date | Sep 12, 1989 |
| Priority date | — |
| Expiry date | Jun 17, 2008 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01R19/0084
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A voltage measurement circuit is provided which can be used in a single supply situation, which has a measurement range from rail to rail and which uses a reference voltage which can lie anywhere between the rails but not at the rail to which measurements are to be referenced. The unknown voltage is sampled to a first plate of a capacitor. The second plate of the capacitor is connected to ground. The first plate of the capacitor is then connected to the first input of a comparator, the second input being connected to receive the reference voltage. If the unknown voltage is less than the reference voltage, the second plate of the capacitor is disconnected from ground and then connected to receive the reference voltage. Otherwise it remains connected to ground. The first plate of the capacitor is then connected to a constant current source, causing the voltage at the first comparator input to decrease linearly with time. By measuring the elapsed time between the connection of the first capacitor plate to the constant current source and a change of state of the comparator due to the voltage decrease at its first input, the difference in voltage between the unknown voltage and the refe…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.