# US 9,438,106 B2 · Hysteretic current mode controller for a bidirectional converter with lossless inductor current sensing

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- Number: US 9,438,106 B2
- Document ID: US9438106B2
- Status: Granted
- Kind: B2
- Application number: 13/983,732
- Filed: 2012-02-08
- Published: 2013-11-21
- Granted: 2016-09-06
- Earliest claimed: 2011-02-11
- Assignees: Balancell (Pty) Ltd
- Applicants: Ian Douglas De Vries
- Inventors: Ian Douglas De Vries
- Web page: https://patentgrep.com/patent/US9438106B2

## CPC

- H02M 3/1563: {without using an external clock (H02M3/158 takes precedence)}
- G01R 19/0092: {Measuring current only}
- H02M 3/156: with automatic control of output voltage or current, e.g. switching regulators
- H02M 1/0009: {Devices or circuits for detecting current in a converter}
- H02M 1/0025: {Arrangements for modifying reference values, feedback values or error values in the control loop of a converter}
- H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P)
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)

## Abstract

A system and circuit for achieving bidirectional hysteretic current mode control of a converter. The system comprises a summer that provides a constant hysteresis and has added switching noise immunity, a comparator, a lossless inductor current sense means and a converter. A circuit using the inductors internal resistance for sensing the current through an inductor in a lossless manner is described. The circuit preserves both DC and dynamic current information while incorporating the RC time constant, difference amplifier and signal amplification, all using only one amplifier. This circuit provides excellent common mode and differential noise immunity, while still having a high bandwidth and small group delay of the current signal. A method to accomplish stability of a current mode controlled converter when closing the loop to control the output voltage with very high accuracy and gain is described.

## Claims

### Claim 1

A method to attain stability when closing the loop to control the output voltage of a current mode controlled converter when using a very high gain, comprising:
a difference amplifier positioned between a desired output voltage set point and the output voltage;
said difference amplifier having a first feedback resistor connected between the output of the amplifier and its negative input;
said first feedback resistor setting a DC gain of the difference amplifier;
said difference amplifier having a first RC stage added in parallel across said first feedback resistor;
said first RC stage comprising a second feedback resistor in series with a first feedback capacitor connected in parallel across said first feedback resistor;
said second feedback resistor being approximately 1/3 to 1/2 the value of said first feedback resistor;
said difference amplifier having a second RC stage also added in parallel across said first feedback resistor;
said second RC stage comprising a third feedback resistor in series with a second feedback capacitor also connected in parallel across said first feedback resistor;
said third feedback resistor being approximately 1/3 to 1/2 the value of said second feedback resistor; and
said second feedback capacitor being approximately 1/3 or less the value of said first capacitor.

### Claim 2 (depends on 1)

The difference amplifier of claim 1, having further RC stages connected in parallel across said first feedback resistor, up to the Nth stage whereby:
said Nth feedback resistor being approximately 1/3 to 1/2 the value of said Nth −1 feedback resistor; and
said Nth −1 feedback capacitor being approximately 1/3 or less the value of said Nth −2 feedback capacitor.