HIP6311A

FN9035 Rev 1.00

Page 7 of 16

July 2004

Operation

Figure 1 shows a simplified diagram of the voltage regulation

and current control loops. Both voltage and current feedback

are used to precisely regulate voltage and tightly control output

loop comprises the Error Amplifier, Comparators, gate drivers

and output MOSFETS. The Error Amplifier is essentially

connected as a voltage follower that has as an input, the

Programmable Reference DAC and an output that is the

CORE voltage.

Voltage Loop

the inverting input of the Error Amplifier. This signal can drive

the Error Amplifier output either high or low, depending upon

the CORE voltage. Low CORE voltage makes the amplifier

output move towards a higher output voltage level. Amplifier

output voltage is applied to the positive inputs of the

Comparators via the Correction summing networks. Out-of-

phase sawtooth signals are applied to the two Comparators

inverting inputs. Increasing Error Amplifier voltage results in

increased Comparator output duty cycle. This increased duty

cycle signal is passed through the PWM CIRCUIT with no

phase reversal and on to the HIP6601, again with no phase

reversal for gate drive to the upper MOSFETs, Q1 and Q3.

Increased duty cycle or ON time for the MOSFET transistors

results in increased output voltage to compensate for the low

output voltage sensed.

Current Loop

The current control loop works in a similar fashion to the

voltage control loop, but with current control information

applied individually to each channel’s Comparator. The

information used for this control is the voltage that is developed

they are conducting. A single resistor converts and scales the

voltage across the MOSFETs to a current that is applied to the

Current Sensing circuit within the HIP6311A. Output from

these sensing circuits is applied to the current averaging

circuit. Each PWM channel receives the difference current

signal from the summing circuit that compares the average

sensed current to the individual channel current. When a

power channel’s current is greater than the average current,

FIGURE 1. SIMPLIFIED BLOCK DIAGRAM OF THE HIP6311A VOLTAGE AND CURRENT CONTROL LOOPS FOR A TWO POWER

CHANNEL REGULATOR

CURRENT

SENSING

COMPARATOR

PWM

CIRCUIT

+

+

CORRECTION

ERROR

AMPLIFIER

FB

REFERENCE

Q3

Q4

PHASE

PWM1

DAC

HIP6311A

HIP6601

-

Q1

Q2

PHASE

HIP6601

CURRENT

SENSING

COMPARATOR

PWM

CIRCUIT

CORRECTION

PWM2

-

I AVERAGE

+

+

+

-

PROGRAMMABLE

-

-

-

-

+

+

CURRENT

AVERAGING

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