CPI CMP 200 Series Service Manual page 283

7
Theory of Operation
7.1.0 INTRODUCTION
This chapter contains the theory of operation for the CMP 200® and CMP 200® DR X-ray generators.
The theory of operation is organized by functional blocks as per the functional drawings in chapter 9.
7.2.0 FUNCTIONAL THEORY OF OPERATION
Refer to the appropriate functional block diagram in chapter 9 in conjunction with the theory of operation
in this chapter. Waveforms and voltages at the pertinent test points are typically shown on the last page
of each functional drawing.
7.2.1 System ON (MD-0928)
The generator control board on the CMP 200® series of X-ray generators includes power ON and power
OFF switches S1 and S2 that may be used to switch the generator on and off locally while working on the
equipment. These switches are connected in parallel with the generator ON and OFF switches that are
located on the consoles.
Pressing any of the power-ON switches turns on Q5 on the generator control board. This turns on Q6,
holding the collector of Q6 low. This latches Q5 in the "on" state by holding the base of Q5 low when the
ON switch is released.
The collector of Q6 is connected to K1 on the generator control board (MD-0927). K1 will be energized
when the generator is switched on, supplying +24 V to the console.
With Q6 turned on, the base of Q7 is held low, turning Q7 off. The collector of Q7 is connected to the ON
/ OFF control pins on the +5 V, +12 V, and +15 V switching regulators on the generator control board
(MD-0927). With Q7 turned off, the regulator control pins will be pulled to a logic high state, enabling the
low-voltage supplies on the generator control board (MD-0927).
In normal operation, a wire jumper is connected between J2-1 and J2-2 on the generator control board.
An emergency-off switch may be connected to the generator by removing the jumper between J2-1 and
J2-2, and then wiring the emergency-off switch to J2-1 and J2-2. If the connection between J2-1 and J2-2
is open-circuit (i.e. no jumper or an open emergency-off switch), K2 will be de-energized as shown. This
holds the base of Q6 low, preventing Q6 from turning on.
A supervisory circuit (not shown) monitors the +1.2 V, +3.3 V, and +5 V DC supplies on the generator
control board. The supervisory circuit releases the CPU reset line when these low voltage DC supplies
are detected at start-up. This causes the CPU to enter its startup sequence. The CPU will initialize itself,
perform its startup diagnostics, and then output a command via U86 and U83 on the generator control
board to energize soft-start contactor K2 on the H.V auxiliary board. The CPU will then wait for
approximately 10 seconds for the output of opto-coupler U5 on the H.V auxiliary board to ramp high,
indicating that the DC bus capacitors are charged. If U5 indicates proper DC bus capacitor charging
within the allotted time, the CPU will output a command to U86 and the driver consisting of Q28, Q29, etc
to energize the main power contactor via the H.V auxiliary board. Soft-start contactor K2 will be de-
energized after a maximum of 10 seconds, as the soft-start circuit is not needed once the DC bus
capacitors are charged.
If opto-coupler U5 on the H.V auxiliary board does not indicate normal DC bus capacitor charge within the
allowed time limit, an error message will be presented and the turn-on sequence will be aborted.
Pressing any of the power-OFF switches turns on Q4 on the generator control board. This turns off Q5,
turning off Q6. This will de-energize K1 on the generator control board, removing the +24 V supply from
the console. With Q6 turned off, Q7 will turn on, taking the ON / OFF control lines on the +5 V, +12 V, and
+15 V regulators low. This disables the switching regulators, shutting down the generator control
functions. The main power contactor will open, removing the AC input to the mains rectifier assembly.
Use and disclosure is subject to the restrictions on the title page of this CPI document.
Page 7-2
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CMP 200 X-Ray Generator Service Manual
CPI Canada Inc.
Ch # 901476-09 Rev. C