1. A hydrostatic drive comprising:
a hydraulic pump having an inlet and an outlet;
at least three hydraulic motors configured to be driven by the hydraulic pump;
a first flow divider that is arranged downstream of the hydraulic pump, and that has an inlet connected to the outlet of the hydraulic pump, a first outlet, and a second outlet;
a second flow divider that is arranged upstream of the hydraulic pump, and that has a first inlet, a second inlet, and an outlet connected to the inlet of the hydraulic pump, wherein:
a first hydraulic motor of the at least three hydraulic motors has:
an inlet side connected to the first outlet of the first flow divider; and
an outlet side connected to the first inlet of the second flow divider;
a second hydraulic motor of the at least three hydraulic motors has:
an inlet side connected to the first outlet of the first flow divider; and
an outlet side connected to the second inlet of the second flow divider; and
a third hydraulic motor of the at least three hydraulic motors has:
an inlet side connected to the second outlet of the first flow divider; and
an outlet side connected to the first inlet of the second flow divider.
2. The hydrostatic drive according to claim 1, further comprising a plurality of pressure limiting valves configured to open into a tank, such that:
for each hydraulic motor connected to the first flow divider, a respective pressure limiting valve is connected between the hydraulic motor and a corresponding outlet of the first flow divider; and
for each hydraulic motor connected to the second flow divider, a respective pressure limiting valve is connected between the hydraulic motor and a corresponding inlet of the second flow divider.
3. The hydrostatic drive according to claim 1, further comprising:
a feed pump;
a plurality of replenishing valves configured to open in a pressure medium flow direction away from the feed pump; and
a plurality of feed lines each connected to the feed pump via a respective replenishing valve, such that:
for each hydraulic motor connected to the first flow divider, a respective feed line is connected on one end to a corresponding replenishing valve, and on another end between the hydraulic motor and a corresponding outlet of the first flow divider; and
for each hydraulic motor connected to the second flow divider, a respective pressure limiting valve is connected on one end to a corresponding replenishing valve, and on another end between the hydraulic motor and a corresponding inlet of the second flow divider.
4. The hydrostatic drive according to claim 3, further comprising:
at least one bypass valve configured to control a pressure medium connection between the at least three hydraulic motors and the hydraulic pump, each bypass valve arranged parallel to a respective flow divider.
5. The hydrostatic drive according to claim 4, wherein the at least one bypass valve includes a valve slider configured to be acted on in a first direction of an open position by a pressure between the replenishing valves and the feed pump and configured to be acted on in a second direction of a closed position by a spring force of a valve spring.
6. The hydrostatic drive according to claim 4, wherein the at least one bypass valve includes a valve slider configured to be acted on in a first direction of a closed position with an adjustment force by an electric actuator and configured to be acted on in a second direction of an open position by a spring force of a valve spring.
7. The hydrostatic drive according to claim 6, further comprising:
a switch configured to activate or deactivate the electric actuator by a pivoting angle of a gas pedal of an engine which drives the hydraulic pump or by a pivoting angle of a steering cylinder of a steering system of a vehicle which has the hydrostatic drive.
8. The hydrostatic drive according to claim 1, wherein at least one of the first flow divider and the second flow divider is one of a hydraulic flow dividing valve, a hydraulic external gear machine, and a load-pressure-independent flow distribution controller.
9. The hydrostatic drive according to claim 1, wherein:
the hydrostatic drive is a traction drive; and
a respective hydraulic motor is connected to a respective wheel of the traction drive.
10. The hydrostatic drive according to claim 1, wherein the hydraulic pump is pivotable configured to pivot in order to reverse a direction of rotation of the hydraulic motors.
11. The hydrostatic drive according to claim 1, further comprising a fourth hydraulic motor that is configured to be driven by the hydraulic pump, and that includes:
an inlet side that is connected to the second outlet of the first flow divider; and
an outlet side that is connected to the second inlet of the second flow divider.
12. The hydrostatic drive according to claim 11, further comprising a plurality of pressure limiting valves configured to open into a tank, such that:
for each hydraulic motor connected to the first flow divider, a respective pressure limiting valve is connected between the hydraulic motor and a corresponding outlet of the first flow divider; and
for each hydraulic motor connected to the second flow divider, a respective pressure limiting valve is connected between the hydraulic motor and a corresponding inlet of the second flow divider.
13. The hydrostatic drive according to claim 11, further comprising:
a feed pump;
a plurality of replenishing valves configured to open in a pressure medium flow direction away from the feed pump; and
a plurality of feed lines each connected to the feed pump via a respective replenishing valve, such that:
for each hydraulic motor connected to the first flow divider, a respective feed line is connected on one end to a corresponding replenishing valve, and on another end between the hydraulic motor and a corresponding outlet of the first flow divider; and
for each hydraulic motor connected to the second flow divider, a respective pressure limiting valve is connected on one end to a corresponding replenishing valve, and on another end between the hydraulic motor and a corresponding inlet of the second flow divider.
14. The hydrostatic drive according to claim 11, further comprising:
at least one bypass valve configured to control a pressure medium connection between the at least three hydraulic motors and the hydraulic pump, each bypass valve arranged parallel to a respective flow divider.
15. The hydrostatic drive according to claim 11, wherein at least one of the first flow divider and the second flow divider is one of a hydraulic flow dividing valve, a hydraulic external gear machine, and a load-pressure-independent flow distribution controller.
16. The hydrostatic drive according to claim 11, wherein:
the hydrostatic drive is a traction drive; and
each of the at least three hydraulic motors is connected to a respective wheel of the traction drive.
17. The hydrostatic drive according to claim 1, further comprising:
at least one bypass valve configured to control a pressure medium connection between the at least three hydraulic motors and the hydraulic pump, each bypass valve arranged parallel to a respective flow divider.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
What is claimed is:
1. A comparator with an offset compensation function comprising:
a differential circuit provided with differential pair transistors each made up of an MOS transistor and a load circuit;
an output buffer circuit that inverts the phase of an output signal of said differential circuit; and
a feedback path for, when a same voltage is given to both of said differential pair transistors, feeding back the output signal of said output buffer circuit as a substrate bias voltage of either of said differential pair transistors.
2. The comparator according to claim 1, wherein, of said differential pair transistors, the size of the MOS transistor to which the output signal of said output buffer circuit is fed back as a substrate potential is designed to be greater than the size of the other MOS transistor so as to generate an initial offset to prevent a parasitic transistor which exists between the substrate and source of the MOS transistor from turning ON.
3. A DA conversion apparatus comprising:
a circuit for detecting an amount of inputoutput offset using the comparator according to claim 1; and
a circuit for compensating for said detected inputoutput offset.
4. A comparator with an offset compensation function capable of switching between a normal operating mode and offset canceling mode and integrated on a semiconductor substrate, comprising:
transistors forming a differential pair;
a circuit for equalizing the gate potentials of said differential pair transistors only in said offset canceling mode;
a current mirror that operates as a load of said differential pair transistors;
an output stage circuit that includes a first transistor which receives a single end output of said current mirror and a second transistor which is of a conductive type opposite to that of this first transistor;
a phase adjustment circuit that is connected between the gate and drain of said first transistor only in said offset canceling mode;
a path for giving the voltage of the output terminal of said output stage circuit to the substrate of the transistor that receives an input signal out of said differential pair transistors; and
a capacitance element that retains the voltage given to the substrate of the transistor that receives said input signal through said path even after said offset canceling mode is canceled.
5. The comparator according to claim 4, wherein an offset is given beforehand to current capacities of said differential pair transistors.
6. A DA conversion apparatus with an offset compensation function comprising:
a DA converter;
the comparator with an offset canceling function according to claim 4 that compares the output voltage of said DA converter and a reference voltage; and
an offset compensation circuit that compensates the input and output of said DA converter based on the output of said comparator.
7. A DA conversion apparatus with an offset compensation function using negative feedback loop control comprising:
a single inputdifferential output type DA converter;
a differentialsingle conversion circuit that converts the differential output of said DA converter to a single output;
the comparator with an offset canceling function according to claim 4 that compares the output voltage of said differentialsingle conversion circuit with a reference voltage; and
an offset compensation circuit that compensates an offset between the input and output of said DA converter based on the output of said comparator.
8. The DA conversion apparatus according to claim 7, wherein the follow-up capability of said negative feedback control loop is made variable.
9. A DA conversion apparatus with an offset compensation function, comprising:
a single inputdifferential output type DA converter;
a switched capacitor filter that receives the differential outputs of said DA converter as inputs;
a differentialsingle conversion circuit that converts the differential output which is output from said switched capacitor filter to a single output;
the comparator with an offset canceling function according to claim 4 that compares the output voltage of said differentialsingle conversion circuit with a reference voltage; and
an offset compensation circuit that compensates for an offset between the input and output of said DA converter based on the output of said comparator.
10. A CDMA-based radio transmitter that spreadsmodulates a transmission signal, DA-converts the spreadmodulated signal and transmits through an antenna, comprising the DA conversion apparatus with an offset compensation function according to claim 6 for converting said spreadmodulated signal to an analog signal.
11. A method for compensating for an inputoutput offset of said DA converter included in the DA conversion apparatus according to claim 6, comprising the steps of:
changing said comparator to an offset canceling mode and canceling an offset of said comparator by controlling the substrate bias of either of said differential pair transistors through negative feedback control;
returning said comparator to a normal operating mode;
completing an adjustment for canceling an inputoutput offset of said DA converter during a period during which the bias voltage for canceling said offset is retained by said capacitance element incorporated in said comparator.