# US 4,400,692 A · Method for periodic digital to analog conversion > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,400,692 A - Document ID: US4400692A - Status: Granted - Kind: A - Application number: 06/320,675 - Filed: 1981-11-12 - Granted: 1983-08-23 - Earliest claimed: 1980-11-20 - Assignees: BBC Brown, Boveri & Company, Limited - Inventors: Reto Klein - Web page: https://patentgrep.com/patent/US4400692A ## CPC - H03M 1/82: with intermediate conversion to time interval - H03M 1/86: with intermediate conversion to frequency of pulses - H03M: CODING; DECODING; CODE CONVERSION IN GENERAL (using fluidic means F15C4/00; optical analogue/digital converters G02F7/00; coding, decoding or code conversion, specially adapted for particular applications, see the relevant subclasses, e.g. G01D, G01R, G06F, G06T, G09G, G10L, G11B, G11C, H04B, H04L, H04M, H04N; ciphering or deciphering for cryptography or other purposes involving the need for secrecy G09C) ## Abstract For converting a digital value into an analog value, the digital value is first converted into a binary number and then selected auxiliary pulse trains corresponding to the binary number are used to control a switch which connects a capacitor alternatively to a reference voltage source or to ground to charge the capacitor to a voltage which corresponds to the converted analog value. The pulses in the auxiliary pulse trains associated with each binary position are grouped into pulse groups and the pulse groups of each pulse train are distributed over the duration of a conversion period in such a manner that during the superimposition of auxiliary pulse trains the number of pulse groups is not increased but the existing pulse groups are widened by being placed next to each other. In addition, the width of the single pulses forming the pulse groups is doubled so that the pulse groups are transformed into width-modulated pulses. ## Claims ### Claim 1 A method for converting a digital signal presented in the form of a binary number signal into a analog signal comprising the steps of: summing during a conversion period the pulses of selected ones of a set of auxiliary pulse trains to form a composite pulse train, wherein: the selected ones of said auxiliary pulse trains are selected in dependence on the value of each binary position of the binary number signal; each one of said auxiliary pulse trains corresponds to one of said binary positions and has a number of pulses equal to the value of 2.sup.N, where N is the number of the corresponding binary position; the pulses in each auxiliary pulse train starting with at least the auxiliary pulse train for the third binary position form pulse groups containing an equal number of pulses; the auxiliary pulse train for the highest number binary position has an even number of pulse groups and the number of pulses in each pulse group are identical to the number of clock pulses in each interval between successive pulse groups; each pulse group in the auxiliary pulse trains other than the auxiliary pulse train for the highest number binary position contain no more than half as many pulses as each pulse group in the auxiliary pulse train for the highest value binary position; and the pulse groups in the auxiliary pulse trains are displaced in time with respect to one another such that pulse groups from each auxiliary pulse train other than the auxiliary pulse train for the highest number binary position can be concatenated with the last pulse, or can precede the first pulse, of a pulse group from the auxiliary pulse train for the highest number binary position when the pulse trains are summed; and controlling a switch which connects a capacitor to a predetermined voltage source with said composite pulse train in order to charge the capacitor to a voltage constituting the analog signal. ### Claim 2 A method for converting a digital signal presented in the form of a binary number signal into a analog signal comprising the steps of: summing during a conversion period the pulses of selected ones of a set of auxiliary pulse trains to form a composite pulse train wherein: the selected ones of said auxiliary pulse trains are selected in dependence on the value of said binary position of the binary number signal; each one of said auxiliary pulse trains corresponds to one of said binary positions and has a number of pulses equal to the value of 2.sup.N, where N is the number of the corresponding binary position; the pulses in each auxiliary pulse train starting with at least the auxiliary pulse train for the third binary position form pulse groups containing an equal number of pulses; the auxiliary pulse train for the highest number binary position has an even number of pulse groups and the number of pulses in each pulse group are identical to the number of clock pulses in each interval between successive pulse groups; each pulse group in the auxiliary pulse trains other than the auxiliary pulse train for the highest number binary position contain no more than half as many pulses as each pulse group in the auxiliary pulse train for the highest value binary position; and the pulse groups in the auxiliary pulse trains are displaced in time with respect to one another such that pulse groups from each auxiliary pulse train can be concatenated with pulse groups from at least one other auxiliary pulse train when the pulse trains are summed; and controlling a switch which connects a capacitor to a predetermined voltage source with said composite pulse train in order to charge the capacitor to a voltage constituting the analog signal. ### Claim 3 (depends on 1, 2) The method of claim 1 or 2 comprising the further step of, prior to the controlling step, widening the pulses of the composite pulse train to the duration of one clock period in order to convert the pulse groups of the composite pulse train into width-modulated pulses. ### Claim 4 (depends on 3) The method according to claim 3, wherein the pulses are widened after having been summed. ### Claim 5 (depends on 1) The method according to claim 1, wherein the digital signal to be converted corresponds to a binary number having at least five binary positions, and the auxiliary pulse train for the highest value binary position has four pulse groups in each conversion period. ### Claim 6 (depends on 1) The method of claim 1, wherein the digital signal to be converted corresponds to a binary number having at least six binary positions, and the number of the pulse groups in the auxiliary pulse train for the highest value binary position is in each conversion period equal to the integral square root of the number of clock pulses required for converting this binary number or the binary number which is smaller by one binary position.