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Switching power supplies languished in commercial applications up until around An interesting note is that a description of the SG and its operation are For example, Silicon General brought out the SG, which. cover. AN Application Note AN Six-Output V MGDs. Simplify 3-Phase Motor Drives. Table of Contents. Page. Gate Drive Requirements. SG datasheet, cross reference, circuit and application notes in pdf format.


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This is possible because the switching frequency is adjusted in accordance with the load without changing operational states, thus making it unnecessary to define plural states of operation. The timing of turning on the switch es varies since the switch es is are turned on when two set ready signals both become ready.

For fixed frequency switching applications, switching pulses from a fixed frequency oscillator as a first set signal are skipped when a second set signal is not ready. On the other hand, for a variable frequency switching scheme which is implemented sg1525 application note driving the switching with a one-shot having a constant OFF time, the switching pulse is created after both set signals become active.

A low pass filter is also used to dynamically adjust the minimum peak inductor current and to minimize ripple voltage for low load conditions so that a smaller output capacitor may be used.

Field of the Invention The present invention relates to a DC to DC converter which is highly efficient for light loads and, more particularly, to a DC to DC converter having a current mode switching voltage regulator circuit and a feedback control path which regulates the switching frequency over broad current ranges based on the load without changing operational modes so that improved switching efficiency is made possible.

DC sg1525 application note DC converters of the type to which the present invention is directed employ a switching voltage regulator to convert the input DC voltage into the output DC voltage.

The switching voltage regulator employs a switch, such as a power MOSFET, coupled either in series or in parallel with the load. The voltage applied to the load is regulated by controlling the ON and OFF time of the switch using a control circuit which varies the duty cycle applied to the switch based on the difference between the input DC voltage and the output DC voltage.


The switching voltage regulator further employs inductive energy storage elements for converting the switched current pulses from the switch into a steady load current. The duty cycle of the switch can be varied using a fixed frequency approach in which the frequency of the pulse stream is fixed and the ON or OFF time of each pulse is varied, or using a variable frequency approach in which the ON or OFF time of each pulse is fixed but the pulse stream frequency is varied.

In either case, the output voltage is increased sg1525 application note increasing the ON time of the switch and is decreased by decreasing the ON time of the switch. A feedback circuit is used to accordingly vary the Sg1525 application note time of the switch so that a constant output voltage is maintained.

The present invention may use either approach. When the DC to DC converter is used in battery operated devices such as laptop and notebook computers and other hand-held electronic devices, the efficiency of the voltage regulator becomes critical to the effort to extend battery life.


Typically, the efficiency of the voltage regulator decreases at low output current or low load sg1525 application note since the efficiency is generally a function of output current drawn by the load and since the losses associated with the operation of the switching voltage regulator become a larger percentage of the overall energy dissipation.

Numerous techniques have been proposed to improve the efficiency of voltage regulators for low load conditions. The output voltage is maintained in a predetermined range defined by upper and lower voltage thresholds when the output power of the DC to DC converter is below a low power threshold by turning off the switch control circuit so long as the output voltage level is above the lower voltage threshold.

When the output capacitor discharges below the lower voltage threshold, the switch control sg1525 application note is again activated to cause normal duty cycle switching until the output DC voltage exceeds the upper voltage threshold. The switch control circuit is then deactivated until the output DC voltage again falls below the lower voltage threshold.

This operation is repeated so long as the output power to the load remains below the low power threshold. Once the low power threshold is exceeded, normal duty sg1525 application note switching operation is resumed. Since less switching energy is dissipated for light loads, efficiency of the voltage regulator is improved.

SG - Voltage Mode PWM - STMicroelectronics

A constant current source I1 and hysteretic comparator 24 are also provided for providing improved efficiency at low average current levels. The overvoltage condition is intentionally induced at low average output currents by constant current source Sg1525 application note.

In the sleep mode, other circuit elements may be deactivated as well. When it is detected by comparator 24 that VFB is less than VREF, the voltage regulator 10 sg1525 application note from the sleep mode and normal duty cycle switching resumes until the output capacitor is again overcharged and the "sleep" mode may be entered again.


The voltage regulator 10 of prior art FIG. Such over driving of the output capacitor COUT leads to increased ripple voltage.

US5912552A - DC to DC converter with high efficiency for light loads - Google Patents

A highly efficient voltage regulator is desired which minimizes the ripple voltage during low power conditions. Voltage regulator 30 improves operating efficiency by providing a light load sg1525 application note in which, rather than turning off the switching transistors for a "sleep" state, the rate of switching of the switching transistors is reduced in accordance with the sg1525 application note when a light load condition is detected.

As illustrated, voltage regulator 30 includes synchronous switching transistors 32 and 34, comparator 36 for comparing the output DC voltage drop across R2 to a reference voltage VREF, switching control circuit 38, and feedback comparators 40 and During operation, if the inductor current IL is detected by feedback comparator 40 to be greater than a threshold, comparator 40 outputs a level indicating that the output current is high.

On the other hand, if the inductor current IL is detected by feedback comparator 42 to be less than another, lower, threshold, comparator 42 outputs a level indicating that output current is low.

Comparator 36 monitors the voltage drop across R2, which is indicative of the output voltage VOUT and provides another control signal to switch control circuit